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Evaluation of the Predictive Character of the Expiratory Inferior Vena Cava/Abdominal Aorta (eIVC/Ao) Index for Minimum Blood Pressure Following Spinal Anesthesia With 0.5% Hyperbaric Bupivacaine

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Author: Merle-Béral J

Cureus 16(8): e67310.

Abstract

Spinal anesthesia has many side effects, one of them being a drop in blood pressure (BP). Identifying predictive factors for this drop is a clear matter of concern. In this regard, the expiratory inferior vena cava/abdominal aorta (eIVC/Ao) index has already been spotted as such for doses of 0.5% hyperbaric bupivacaine greater than 12mg. Departing from the demonstrated correlation between this index and hypotension post-spinal anesthesia, our study aimed to (1) evaluate whether an eIVC/Ao index greater than 0.7, thus defining non-hypovolemic patients, can also predict minimal BP for doses inferior to 12mg and (2) identify other predictive factors for minimal BP post-spinal anesthesia. Lastly, we verified whether preoperative fasting induces hypovolemia.

This single-center prospective observational pilot study included 20 patients. The baseline measurements of BP, eIVC/Ao index, and fasting time were recorded at time T0′. Then spinal anesthesia was administered with 0.5% hyperbaric bupivacaine in doses inferior to 12 mg. The patients’ systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and metameric levels were each recorded at times T5′, T10′, T15′, and T20′.

The results indicated that baseline DBP was predictive of low DBP and minimum MAP, which reflect myocardial perfusion and systemic pressures, respectively. Therefore, it should trigger prophylaxis (spinal-lateralized, continuous, or lower dose) in patients with a low DBP baseline. Additionally, baseline SBP was predictive of minimum SBP, an independent risk factor for post-anesthetic hypotension if its baseline is less than 120 mmHg. Although female gender was linked to minimum SBP, other confounding factors (size, dose administered, and type of surgery related to gender) must also be considered. Moreover, a correlation was established between height and MAP in parturients. Hypotension was not recorded at local anesthetic (LA) doses between 8 and 12 mg and the doses administered were sufficient to achieve the metameric levels required for surgery (ether tests). Since 8 mg of 0.5% hyperbaric bupivacaine achieved the same level as 12 mg, lower doses of LA might prevent a significant drop in BP and its deleterious effects.

Therefore, in the current cohort, the eIVC/Ao index was not predictive of minimum BP during spinal anesthesia with doses less than 12 mg of 0.5% hyperbaric bupivacaine. However, predictive factors for minimum BP included gender and baseline SBP (for minimum SBP), height and baseline DBP (for minimum MAP), and baseline DBP (for minimum DBP). Lastly, preoperative fasting did not cause hypovolemia.

Introduction

Spinal anesthesia is associated with a significant drop in blood pressure (BP) to the point of hypotension (defined as systolic blood pressure (SBP) < 90 mmHg and/or diastolic blood pressure (DBP) < 60 mmHg [1]). Hypotension occurs in 15.3%-33% of cases [2] (particularly in pregnant women) and can interfere with tissue perfusion, leading to significant morbidity [3].

The index of the diameter of the inferior vena cava in exhalation compared to that of the abdominal aorta in systole (the expiratory IVC/Ao index) is a rapid, simple, non-invasive, and reliable method of determining the volume status of patients [4-6]. The pilot study by Salama et al. comprising 100 patients undergoing spinal anesthesia showed that the eIVC/Ao index is a predictive factor for the occurrence of post-spinal anesthesia arterial hypotension [7]. However, the doses of 0.5% hyperbaric bupivacaine were greater than 12 mg in the study.

The present study aimed to evaluate whether an eIVC/Ao index > 0.7 ± 0.09 [4] was predictive of minimal post-spinal anesthesia BP for < 12 mg of 0.5% hyperbaric bupivacaine in non-hypovolemic patients. In addition, we also determined whether there were other factors predictive of minimal post-spinal anesthesia BP and whether the duration of preoperative fasting-induced hypovolemia.

Materials & Methods

Herein, we conducted a single-center, prospective, observational pilot study at University Hospital Saint-Pierre, Brussels (Belgium) including 20 patients. The study was approved by the ethics committee (BE0762023231202).

The demographic characteristics recorded were sex, age, height, weight, body mass index (BMI), and American Society of Anesthesiologists (ASA) score.

The inclusion criteria were as follows: age between 18 and 65 years, ASA score I-II, and scheduled lower limb, urological, gynecological, or digestive surgery that could be performed under spinal anesthesia with 0.5% hyperbaric bupivacaine.

The exclusion criteria included patient refusals, contraindication to spinal anesthesia, lateralized spinal anesthesia, pediatric and geriatric populations, emergency surgery, patients with extremes of stature, i.e. too short (<160 cm) or too tall (>190 cm), use of sedatives, intrathecal adjuvant, preoperative volume replenishment, pregnant women, patients with poor echogenicity, those treated with beta-blockers and/or angiotensin-converting enzyme (ACE) inhibitors, and those assessed as hypovolemic using the according to the eIVC/Ao index or already suffering from arterial hypotension prior to spinal anesthesia.

Preoperative recording and evaluation

The duration of fasting was recorded when the patient arrived in the operating room. At T0′, the anesthetist recorded the baseline BP (SBP, DBP, and mean arterial pressure (MAP)). Then, the patient’s eIVC/Ao index was measured in the semi-seated position by ultrasound. In M mode (curvilinear low-frequency probe CA2-8AD, Siemens HS40 machine) in the subxiphoid window: measurement of the diameter of the inferior vena cava (eIVC) in the long axis 2 cm from the right atrial outlet. The anteroposterior systolic diameter of the aorta was estimated to be between 5 and 10 mm above the celiac trunk. Subsequently, the eIVC/Ao index was calculated as the ratio of the maximum diameter of the IVC during exhalation to the maximum diameter of the aorta during systole [6,7]. The image was recorded during three consecutive respiratory cycles in the inspiratory and expiratory phases by the same anesthetist (for the 20 cases) with a level 2 ultrasound experience and with a resident cardiologist reviewing and validating the images (Figure 1).

Ultrasound-measurement-point-location-for-eIVC-and-aorta
Figure 1: Ultrasound measurement point location for eIVC and aorta

A: Expiration IVC; B: Systole aorta

eIVC: Expiration Inferior Vena Cava

After ultrasound identification of the lumbar spine in the seating position, a 27-G Whitacre needle was inserted subarachnoidally at L3-L4. Then, a dose of < 12 mg of 0.5% hyperbaric bupivacaine was injected and adjusted according to the metameric level required for surgery. Each of the SBP, DBP, and MAP values was recorded at time points T5′, 10′, 15′ and 20′, and so were the metameric levels, by ether tests. Finally, arterial hypotension, if ever occurring, was planned to be treated using vasoactive agents and/or fluid challenge as appropriate.

Statistical analysis

Pearson’s correlation analysis was applied to compare the continuous data. The relationship between a continuous variable and a discrete variable was assessed using Student’s t-test when the underlying assumptions were met: 1) homogeneity of variances was evaluated using the Bartlett test and 2) normality of residuals was assessed using the Kolmogorov-Smirnov test. The results of the Student’s t-test were presented as the means and standard deviations per group. When the hypotheses underlying the t-test were not fulfilled, a Wilcoxon rank test was applied to the data, and the results were presented as medians and interquartile ranges. Finally, the data of several independent variables were analyzed using multiple linear regression models to predict the minimum BP level during the perioperative period. These data were entered into the multivariate regression analysis predicting minimum BP. For each of them, no multicollinearity was established (variance inflation factor (VIF) ≤ 5). In the case of multicollinearity, one of the two causative factors was removed from the regression model.

Next, we used a backward variable selection approach, sequentially removing the non-significant variables.

R software version 4.2.0 (R Core Team, 2021) was used to produce the statistical results [8].

Results

A total of 24 patients were recruited in the present study. Of these, three had poor echogenicity or structure detection was not feasible, and one patient withdrew consent. Consequently, 20 patients were included in the study. Among them, three (15%) had undergone orthopedic surgery, five (25%) had gynecological surgery, nine (45%) had urological surgery, and three (15%) patients had undergone proctological surgery. The cohort comprised 11 (55%) men and nine (45%) women, and their average age was 39.4 ± 12.35 years, average height 172.8 ± 7.52 cm, average weight 76.35 ± 9.84 kg, and average BMI 25.34 ± 2.80 kg/m2. Moreover, 11 (55%) patients were ASA I vs. 9 (45%) ASA II.

The average duration of preoperative fasting was 13.9 ± 3.22 h for solids and 11.9 ± 4.53h for liquids. The average eIVC/Ao index was 1.07 ± 0.21.

No hypotensive episodes were observed in the perioperative period. The minimum recorded post-spinal anesthesia SBP, the minimum MAP, and the minimum DBP were 108, 78, and 60 mmHg, respectively (Tables 1, 2).

Descriptive statistics Number (%)
Female 9 (45%)
Male 11 (55%)
ASA Score I 11 (55%)
ASA Score II 9 (45%)
Urological Surgery 9 (45%)
Gynecological Surgery 5 (25%)
Proctological Surgery 3 (15%)
Orthopedic Surgery 3 (15%)
Table 1: Descriptive statistics

ASA:  American Society of Anesthesiologists

Variable Min. 1st Qu. Median Mean 3rd Qu. Max SD
Age (years) 23.00 30.50 35.50 39.40 47.75 64.00 12.35
Weight (kg) 56.00 69.50 79.50 76.35 83.25 90.00 9.84
Height (cm) 160.0 167.0 173.0 172.8 178.5 183.0 7.52
BMI (kg/m2) 19.60 24.50 25.30 25.34 27.10 29.70 2.80
Ratio IVC/Ao 0.75 0.91 1.07 1.07 1.19 1.58 0.21
SBP Baseline (mmHg) 108.0 127.5 132.0 134.6 143.8 168.0 15.86
DBP Baseline (mmHg) 60.00 68.00 74.00 73.65 78.25 99.00 9.06
MAP Baseline (mmHg) 78.00 89.75 95.00 96.33 105.25 114.00 10.57
Solid Fasting (h) 8.00 11.88 12.75 13.85 16.00 21.00 3.22
Liquid Fasting (h) 4.00 9.75 11.75 11.85 13.00 23.00 4.53
Table 2: Recorded measurements for the Wilcoxon rank test

BMI: Body Mass Index; SBP: Systolic Blood Pressure; DBP: Diastolic Blood Pressure; MAP: Mean Arterial Pressure; IVC/Ao: Inferior Vena Cava/Aorta

Independently of the BP studied (systolic, diastolic, and mean) at the cuff, the eIVC/Ao index was not predictive of the minimum BP in the study population (if p > 0.05) (Tables 3–11).

Variable Minimum SBP
Age 0.22
Weight 0.21
Height 0.45*
BMI -0.15
ASA 0.29
SBP Baseline 0.60**
DBP Baseline 0.29
MAP Baseline 0.38
Ratio IVC:Ao 0.07
Bupivacaïne (Dose) 0.04
Table 3: Pearson correlation between the minimum SBP variable and other continuous variables

ASA:  American Society  of Anesthesiologists; BMI: Body Mass Index; SBP: Systolic Blood Pressure; DBP: Diastolic Blood Pressure; MAP: Mean Arterial Pressure; IVC/Ao: Inferior Vena Cava/Aorta

*: p-val<0.05; **: p-val<0.01 (p-value predictive if < 0.05)

Variable Variable =0 Variable =1 p-value
Sex  (0=F, 1=M) 113.11 ± 10.68 126.18 ± 11.06 0.01564
ASA (0=I, 1=II) 117.09 ± 8.36 124.22 ± 15.94 0.214
Table 4: Comparison of minimum SBP, function of gender, and ASA score using Student’s t-test

ASA:  American Society of Anesthesiologists; SBP: Systolic Blood Pressure

p-value predictive if < 0.05

Variable Estimate Std. Error t value Pr(>|t|)
Intercept 56.0875 20.0951 2.791 0.01206
 SBP 0.4772 0.1484 3.216 0.00479
Table 5: Results of multivariable linear regression

SBP: Systolic Blood Pressure

Pr(>|t|) value predictive < 0.05

Variable Minimum DBP
Age 0.23
Weight 0.01
Height 0.28
BMI -0.27
ASA 0.31
SBP Baseline 0.43
DBP Baseline 0.63*
MAP Baseline 0.56*
Ratio IVC:Ao 0.00
Bupivacaine (Dose) 0.08
Table 6: Pearson correlation between the minimum DBP variable and other continuous variables

ASA: American Society of Anesthesiologists; BMI: Body Mass Index; SBP: Systolic Blood Pressure; DBP: Diastolic Blood Pressure; MAP: Mean Arterial Pressure; IVC/Ao: Inferior Vena Cava/Aorta

*: p-val<0.01 (p-value predictive if < 0.05)

Variable Variable =0 Variable =1 p-value
Sex (0=F, 1=M) 63.56 ± 9.51 68.27 ± 8.38 0.2538
ASA (0=I, 1=II) 63.73 ± 8.13 69.11 ± 9.57 0.1901
Table 7: Comparison of minimum DBP, function of gender and ASA score, using Student’s t-test

ASA:  American Society of Anesthesiologists; DBP: Diastolic Blood Pressure

p-value predictive if < 0.05

Variable Estimate Std. Error t value Pr(>|t|)
Intercept 20.3214 13.5139 1.504 0.14999
DBP Baseline 0.6222 0.1822 3.416 0.00308
Table 8: Results of multivariable linear regression

 DBP: Diastolic Blood Pressure

pr (>| t |) predictive if < 0.05

Variable Minimum MAP
Age 0.16
Weight 0.24
Height 0.56*
BMI -0.21
ASA Score 0.26
SBP Baseline 0.54*
DBP Baseline 0.46*
MAP Baseline 0.46*
Ratio IVC:Ao 0.12
Bupivacaine (dose) 0.04
Table 9: Pearson correlation between the minimum MAP variable and other continuous variables

ASA: American Society of Anesthesiologists; BMI: Body Mass Index; SBP: Systolic Blood Pressure; DBP: Diastolic Blood Pressure; MAP: Mean Arterial Pressure; IVC/Ao: Inferior Vena Cava/Aorta

*: p-val<0.05 (p-value predictive if < 0.05)

Variable Variable =0 Variable =1 p-value
Sex (0=F, 1=M) 83.44 ± 9.76 89.32 ± 8.79 0.1741
ASA (0=I, 1=II) 84.50 ± 8.89 89.33 ± 10.00 0.2676
Table 10: Comparison of minimum MAP, function of gender, and ASA score using Student’s t-test

ASA:  American Society of Anesthesiologists; MAP: Mean Arterial Pressure

p-value predictive if < 0.05

Variable Estimate Std. Error t value Pr(>|t|)
Intercept -37.5776 41.8559 -0.898 0.3818
Height 0.5030 0.2331 2.158 0.0456
DBP Baseline 0.5070 0.1935 2.620 0.0179
Table 11: Results of multivariable linear regression

DBP: Diastolic Blood Pressure

pr (>| t |) predictive if < 0.05

However, two variables, height and baseline SBP, were predictive of minimum SBP. These variables were included in a multivariate regression analysis. Although the VIF was 8 for baseline SBP, baseline SBP did not detect multicollinearity between the variables (VIF close to 1) in the final model, which explained 37.91% of the variance in minimum SBP. The only variable predicting minimum SBP in a multivariate regression model was baseline SBP (p = 0.0151). Additionally, once controlled for baseline SBP, height did not have a significant role in predicting minimum SBP (p = 0.1374) and was removed from the model (Table 2). On the other hand, a correlation was established between minimum SBP and female gender (p = 0.01564).

Furthermore, two variables predicted minimum DBP: baseline DBP and baseline MAP. These were included in a multivariate regression analysis, and no concern for multicollinearity was detected. Then, the variable not significantly associated with the dependent variable was removed: baseline MAP (p = 0.484). The final model contained baseline DBP, which explained 35.95% of the variance in the minimum DBP (Tables 6–8).

The independent variables significantly associated with the baseline MAP were entered in multivariate regression analysis. A significant VIF was detected for baseline SBP, which we removed from the analysis. We also removed the variable non-significantly associated with the dependent variable: baseline SBP (p = 0.2555). The final model contained baseline height and baseline DBP, which explained 35.2% of the variance in minimum MAP (Tables 9–11).

Discussion

In the present study, we did not find a correlation between the eIVC/Ao index and minimum BP during spinal anesthesia with 0.5% bupivacaine at doses < 12 mg. The pilot study by Salama et al. predicted the occurrence of arterial hypotension using the eIVC/Ao index during spinal anesthesia [7]. However, this study differs from our approach in several aspects: (1) Our study included only patients who were not hypovolemic according to the eIVC/Ao index; (2) A low dose of 0.5% hyperbaric bupivacaine injected (< 12 mg vs. 12-15 mg); (3) The average age of the patients was lower (39.4 years vs. 49.5 years).

Previous studies have identified the factors associated with a drop in BP following spinal anesthesia: the dose of the local anesthetic (LA) injected, the height of the T5′ block, and age of ≥ 40 years [3,9,10]. In our opinion, these methodological and demographic differences between our study and that of Salama et al. may explain the absence of a significant drop in BP in our cohort.

Another study comprising 172 patients demonstrated that the mean eIVC/Ao index in normovolemic patients was 1.2 ± 0.12, hypovolemic 0.7 ± 0.09, and hypovolemic 1.6 ± 0.05 [4]. These results were further confirmed with an eIVC/Ao index of 1.2 ± 2 for SD = 0.17, defining a normovolemic state [6]. These findings align with the results as the mean value of the eIVC/Ao index in our cohort (1.07 ± 0.21) is compatible with a state of non-hypovolemia, which may also be termed a state of “physiological dehydration” [6]. Another recent study by Rahman et al. suggested a cutoff of the eIVC/Ao index at 1.14 ± 2 with SD 0.18 to detect the early phase of hypovolemic shock [5]. These relative discrepancies suggested that the standardization of eIVC/Ao index values concerning different volemic statuses needs an in-depth investigation.

The lack of correlation between the eIVC/Ao index and minimum BP in our cohort could be explained by the small sample size or a minimal drop in the BP.

The average age of our cohort was 39.4 ± 12.35 years, representing a relatively young population. Thus, it is not surprising that age was not a predictive factor for minimal BP after spinal anesthesia in our population. Elderly patients (defined by the World Health Organization (WHO) as individuals > 60 years old; clinical studies use a cutoff of 65 years) are at greater risk of a drop in BP following spinal anesthesia due to “closure” of the holes of conjugation linked to bone deformations [11-14]. This phenomenon might hinder the diffusion of the LA outside the medullary sheath, causing significant diffusion of the anesthetic block and other cardiovascular performance factors [9,10,13].

Similarly, obesity (defined by a BMI > 30 kg/m2 according to the WHO [15]) is a risk factor for post-spinal anesthetic pressure drop. Magnetic resonance imaging showed that obese people have up to 10 ml less cerebrospinal fluid than those with a normal BMI, which is a potential source of excessive spinal block for the same dose of LA, therefore causing a drop in BP [3,13]. The average BMI in our cohort was 25.34 ± 2.8 kg/m²; thus, our patients were below the risk profile.

In addition, some studies have shown that a high ASA score (> II) is a determining factor in arterial hypotension during general or spinal anesthesia; the older the patient, the greater the risk [16]. All our patients were considered to be at low risk of anesthesia (55% ASA I and 45% ASA II); therefore, our results were in line with the literature.

On the other hand, we also determined other factors predictive of minimal BP during spinal anesthesia with 0.5% bupivacaine at doses < 12 mg. Baseline DBP appeared to be a factor underlying DBP and minimal perioperative MAP. Since DBP and MAP are crucial in myocardial and systemic perfusion, respectively, patients with lower baseline DBP may be identified as requiring special monitoring during surgery [17].

Baseline SBP was predictive of minimal SBP post-spinal anesthesia with 0.5% bupivacaine. Hence, the anesthetic was termed an independent risk factor for the development of post-spinal arterial hypotension if the baseline SBP is < 120 mmHg [3].

A statistical relationship was established between minimum SBP and female gender (p = 0.01564). Also, confounding factors, such as height, dose administered, and type of surgery, could explain this result.

Finally, height also seemed to be a factor predicting minimum MAP; this relationship has been elaborated mainly in the literature on parturients [18].

In agreement with Muller et al. [19], we found that the recorded duration of fasting was not associated with preoperative hypovolemia. Instead, our patients had an eIVC/Ao index > 0.75, corresponding to a state of non-hypovolemia, despite fasting duration exceeding the current recommendations [20].

Furthermore, our study found no evidence of arterial hypotension (absolute minimum SBP: 108 mmHg and absolute minimum DBP: 60 mmHg) for doses of hyperbaric 0.5% bupivacaine ranging from 8 mg to 12 mg. Also, we did not observe any failure of spinal anesthesia regardless of the type of surgery considered, which was confirmed by the ether test of the metameric levels at time points T5′, T10′, T15′, and T20′. These findings suggested that we could consider doses of 0.5% hyperbaric bupivacaine in our daily practice to obtain a sufficient metameric level in certain surgeries. Although the same metameric level could be achieved for different doses of 0.5% hyperbaric bupivacaine (8 mg or 12 mg), the duration of the sensory-motor block is altered (39 min vs. 55 min) [14]. A lower dose of 0.5% hyperbaric bupivacaine might prevent arterial hypotension and its potentially deleterious effects. Thus, the baricity of the LA and the dose are two of the main determinants of LA distribution [13,14].

Methodology limitation

The primary limitation of this study is the small sample size, which results in insufficient statistical power. Thus, future studies with larger patient cohorts are recommended to confirm or refute our findings.

Conclusions

The eIVC/Ao index did not show any correlation with minimum BP during spinal anesthesia with hyperbaric 0.5% bupivacaine at doses less than 12 mg in non-hypovolemic patients. However, predictive factors for minimum blood pressure, under the set circumstances, were gender and baseline SBP (for minimum SBP), height and baseline DBP (for minimum MAP), and baseline DBP (for minimum DBP). Lastly, the duration of preoperative fasting in our cohort did not result in hypovolemia, according to the eIVC/Ao index.

References

  1. Abdallah R, Antoinette P: Arterial hypotension, behind the scene (Article in French). Rev Med Suisse. 2018, 10.53738/REVMED.2018.14.618.1581
  2. Carpenter RL, Caplan RA, Brown DL, Stephenson C, Wu R: Incidence and risk factors for side effects of spinal anesthesia. Anesthesiology. 1992, 76:906-16. 10.1097/00000542-199206000-00006
  3. Liu SS, McDonald SB: Current issues in spinal anesthesia. Anesthesiology. 2001, 94:888-906. 10.1097/00000542-200105000-00030
  4. El-Baradey GF, El-Shmaa NS: Does caval aorta index correlate with central venous pressure in intravascular volume assessment in patients undergoing endoscopic transuretheral resection of prostate?. Saudi J Anaesth. 2016, 10:174-8. 10.4103/1658-354X.168062
  5. Rahman NH, Ahmad R, Kareem MM, Mohammed MI: Ultrasonographic assessment of inferior vena cava/abdominal aorta diameter index: a new approach of assessing hypovolemic shock class 1. Int J Emerg Med. 2016, 9:8. 10.1186/s12245-016-0101-z
  6. Kosiak W, Swieton D, Piskunowicz M: Sonographic inferior vena cava/aorta diameter index, a new approach to the body fluid status assessment in children and young adults in emergency ultrasound–preliminary study. Am J Emerg Med. 2008, 26:320-5. 10.1016/j.ajem.2007.07.012
  7. Salama ER, Elkashlan M: Pre-operative ultrasonographic evaluation of inferior vena cava collapsibility index and caval aorta index as new predictors for hypotension after induction of spinal anaesthesia: a prospective observational study. Eur J Anaesthesiol. 2019, 36:297-302. 10.1097/EJA.0000000000000956
  8. The R Project for Statistical Computing. (2021). Accessed: April 5, 2024: https://www.r-project.org.
  9. Fabrice Ferré, Charlotte Martin, Vincent Minville: Control of arterial blood pressure during spinal anesthesia. Anesthésie & Réanimation. 2017, 3:147-55.
  10. Lairez O, Ferré F, Portet N, et al.: Cardiovascular effects of low-dose spinal anaesthesia as a function of age: an observational study using echocardiography. Anaesth Crit Care Pain Med. 2015, 34:271-6. 10.1016/j.accpm.2015.02.007
  11. Bréchat PH, Vogel T, Bérard A, Lonsdorfer J, Kaltenbach G, Berthel M: What prevention programmes and which organizations are needed to support healthy ageing? (Article in French). Sante Publique. 2008, 20:475-87. 10.3917/spub.085.0475
  12. Rooke GA, Freund PR, Jacobson AF: Hemodynamic response and change in organ blood volume during spinal anesthesia in elderly men with cardiac disease. Anesth Analg. 1997, 85:99-105. 10.1097/00000539-199707000-00018
  13. René Martin, Pierre Lena: Lack of predictability of spinal and epidural block as a cause of failure. Le Praticien en Anesthésie Réanimation. 2009, 13:207-12.
  14. Perimedullary blocks in adults. Annales Françaises d’Anesthésie et de Réanimation. 2007, 26:720-52.
  15. Physical Status: The Use of and Interpretation of Anthropometry, Report of a WHO Expert Committee. 1995 (ed): World Health Organization, Geneva;
  16. Boubacar Ba EH, Leye PA, Traoré MM, et al.: Intra-anesthetic arterial hypotension in elderly patients during emergency surgery: what are the risk factors? (Article in French). Pan Afr Med J. 2017, 26:242. 10.11604/pamj.2017.26.242.9886
  17. Lamia B, Chemla D, Richard C, Teboul JL: Clinical review: interpretation of arterial pressure wave in shock states. Crit Care. 2005, 9:601-6. 10.1186/cc3891
  18. Huang Q, Wen G, Hai C, Zheng Z, Li Y, Huang Z, Huang B: A height-based dosing algorithm of bupivacaine in spinal anesthesia for decreasing maternal hypotension in cesarean section without prophylactic fluid preloading and vasopressors: a randomized-controlled non-inferiority trial. Front Med (Lausanne). 2022, 9:858115. 10.3389/fmed.2022.858115
  19. Muller L, Brière M, Bastide S, et al.: Preoperative fasting does not affect haemodynamic status: a prospective, non-inferiority, echocardiography study. Br J Anaesth. 2014, 112:835-41. 10.1093/bja/aet478
  20. Bouvet L, Benhamou D: Preoperative fasting. Le Praticien en Anesthésie Réanimation. 2008, 12:413-21.

Activation of α7 nicotinic acetylcholine receptors inhibits hepatic necroptosis and ameliorates acute liver injury in mice

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Authors: Fang-Fang Xu, M.S. et al 
Anesthesiology August 2024.
Background

Acute liver injury (ALI) is a disease characterized by severe liver dysfunction, caused by significant infiltration of immune cells and extensive cell death with a high mortality. Previous studies demonstrated that the α7 nicotinic acetylcholine receptor (α7nAChR) played a crucial role in various liver diseases. The hypothesis of this study was that activating α7nAChR could alleviate ALI and investigate its possible mechanisms.

Methods

ALI was induced by intraperitoneal injection of lipopolysaccharide (LPS)/D-galactosamine (D-Gal) in wild type (WT), α7nAChR knockout (α7nAChR -/-) and Sting mutation (Stinggt/gt) mice in the presence or absence of a pharmacological selective α7nAChR agonist (PNU-282987). The effects of α7nAChR on hepatic injury, inflammatory response, mitochondrial damage, necroptosis and infiltration of immune cells during ALI were assessed.

Results

The expression of α7nAChR in liver tissue was increased in LPS/D-Gal induced ALI mice. Compared to the age-matched WT mice, α7nAChR deficiency decreased the survival rate, exacerbated the hepatic injury accompanied with enhanced inflammatory response and oxidative stress, and aggravated hepatic mitochondrial damage and necroptosis. Conversely, pharmacological activation of α7nAChR by PNU-282987 displayed the opposite trends. Furthermore, PNU-282987 significantly reduced the proportion of infiltrating monocyte-derived macrophages (CD45+CD11bhiF4/80int), M1 macrophages (CD45+CD11b+F4/80+CD86 hiCD163low), Ly6Chi monocytes (CD45+CD11b+MHCⅡ lowLy6C hi), but increased the resident Kupffer cells (CD45+CD11bintF4/80 hiTIM4 hi) in the damaged hepatic tissues caused by LPS/D-Gal. Interestingly, α7nAChR deficiency promoted the STING signaling pathway under LPS/D-Gal stimulation, while PNU-282987 treatment significantly prevented its activation. Finally, it was found that Sting mutation abolished the protective effects against hepatic injury by activating α7nAChR.

Conclusions

Our study revealed that activating α7nAChR could protect against LPS/D-Gal induced ALI by inhibiting hepatic inflammation and necroptosis possibly via regulating immune cells infiltration and inhibiting STING signaling pathway.

Uncover A Great CRNA and Anesthesiologist Opportunity in Lubbock TX

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We are seeking a dedicated anesthesia care team to join our new anesthesia care team contract at Lubbock Heart and Surgery Hospital in Lubbock TX.

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Note: Agencies, please do not contact us as we do not use your service

Discover The Best Anesthesiologist Opportunity in New Mexico

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We are seeking a dedicated anesthesiologist to join our all-anesthesiologist group. Our team will consist of 4 full-time providers and 1 for vacation relief, managing 3 operating rooms.

Position Highlights:

  • Zero call for 3 weeks, followed by 1 week of call without daytime work only call after 7 PM therefore you may not work the entire week.
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Interested? Please contact me at 660-596-2224 or drrob@anesthesiaexperts.com if you or anyone you know would like to apply.

Note: Agencies, please do not contact us as we do not use your service

Prolonged Lower Limb Dystonia and Dysphonia Following General Anesthesia in a Patient on Hydroxyzine

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 Author: Wijerathne T

Cureus 16(8): e67263.

Abstract

We present a case of prolonged lower limb movement disorder following general anesthesia in a female patient in her early forties. She presented with vigorous, regular synchronous, rhythmic, and jerky movements during the immediate postoperative period lasting around forty minutes. Her past anesthetic history suggests varying degrees of postoperative movement disorders. Our patient was on long-term hydroxyzine for her skin condition. She had uneventful anesthetics before the prescription of hydroxyzine for her skin condition. All post-anesthetic dystonic events were reported while she was on hydroxyzine. Dystonic reactions during the perioperative period are rare and mostly occur during induction and emergence, which usually be transient. Our patient had prolonged lower limb dystonia resulting in severe muscular pain and lethargy for a few days. Further, she once developed transient aphasia and prolonged dysphonia following total intravenous anesthesia. This clinical finding could be a part of spasmodic laryngeal dystonia, which has not been reported previously. We correlate this rare postoperative dystonic reaction with propofol and possibly with the concurrent use of hydroxyzine.

As differential diagnosis can widely vary, the correlation of clinical findings with movement disorders is important for the diagnosis. Alterations of anesthetic techniques avoiding propofol and holding hydroxyzine are advisable in such rare clinical situations. Early diagnosis of perioperative movement disorders will prompt specific treatments, such as anticholinergic medications, for dystonia.

Introduction

We report a case of prolonged dystonia on multiple occasions in a patient following general anesthesia. Movement disorders are rare during the perioperative period. However, transient movement disorders have been reported during induction and emergence from general anesthesia [1,2]. Severe and prolonged dystonic reactions following general anesthesia are rare, especially in patients with no other risk factors, and are frequently misinterpreted as convulsions.

Voice changes can be due to Laryngeal dystonia [3]; however, it has not been reported following general anesthesia. Our patient previously had aphasia and dysphonia following total intravenous anesthesia in the past which can be a presentation of laryngeal dystonia. Although hydroxyzine can rarely cause movement disorders [4], dystonia in patients on hydroxyzine has never previously been reported following general anesthesia. Even though not conclusive, we try to correlate dystonia as a possibility of concurrent use of hydroxyzine in our patient.

Case Presentation

A female patient in her early forties presented to us with severe sciatica pain for primary posterior fusion and decompression in the lumbar region. She had a medical history of chronic pain and skin psoriasis and had undergone a total of eight surgical procedures, including hand surgeries, arthroscopic shoulder surgeries, posterior decompression in the lumbar region, and partial gastrectomy as an emergency surgery in the past.

The patient experienced abnormal movements in her lower limbs during most of her postoperative periods. These were described as vigorous, painful, involuntary movements of the lower limbs lasting for a couple of hours. The use of midazolam and magnesium transiently reduced her signs and symptoms.

A year ago, she received total intravenous anesthetics for hand surgery, where she experienced aphasia for a couple of hours and dysphonia lasting for a couple of months. Dysphonia was explained as a stuttering and difficulty in controlling her voice with excessive loudness. She had no sore throat or structural anomaly on endoscopy. Her CT and MRI brain were essentially normal at that time and her symptoms as functional expressive dysphasia after referring to a neurologist.

She had no history of any movement disorders in the past except during the emergence of anesthetics. She had no family history of movement disorders or problems that could relate to anesthetics. She was on hydroxyzine for her skin condition as a long-term medication and took bisacodyl, co-codamol, lansoprazole, and methotrexate as regular medications.

On examination, she weighed 101 kg (BMI 38 kg/m²), was euthermic, and did not appear anxious. Her heart rate was 78 beats per minute, and her cardiovascular and respiratory systems were unremarkable. Apart from a foot drop on her left side, her neurological examination was normal. Her laboratory investigations, including electrolytes, were also normal.

Anesthesia was induced with 200 mg of propofol and 60 mg of rocuronium. During the 40 minutes of operative time, her vital parameters remained within normal ranges, and she was euthermic. Anesthesia was maintained with sevoflurane in oxygen and air. The patient received 4 mg of ondansetron, 6.6 mg of dexamethasone, a total of 15 mg of morphine, 1 g of paracetamol, 40 mg of parecoxib, 1 g of magnesium, and 1 mg of intrathecal morphine intraoperatively. After tracheal extubation, the patient was sent to the recovery area.

When she was fully awake, her legs began exhibiting regular, synchronous, rhythmic, and jerky movements. They were vigorous enough to cause her body to move or slide down the bed. The movements occurred in clusters of 4 to 5 jerks every 10 to 15 seconds. Her torso was also involved, with her abdominal and erector spinae muscles experiencing intermittent spasms. The patient’s lower limb muscles were spastic. She received 2 mg of midazolam, which transiently relieved her symptoms for about 2 to 3 minutes. The patient complained of severe pain in her lower limbs and was subsequently administered an additional 10 mg of morphine intravenously. No other abnormal movements or body positions were noted. She was fully conscious and cooperative throughout. Her heart rate increased to 140 beats per minute and remained above 120 beats per minute. The highest body temperature recorded was 36.8 °C.

After 40 minutes of dystonic movements, she was moved into an assisted sitting position with both legs hanging down, where complete cessation of her symptoms was noted. She experienced excessive sweating and muscle pain for a couple of hours, which were treated symptomatically.

The patient was discharged home on the second day, and no further abnormal movements were reported. She felt weak and fatigued for the following few days. Successive follow-up visits were carried out, and after multidisciplinary meetings with the anesthetic, acute medical, and specialist neurology teams, an anesthetic alert was raised and detailed communication was forwarded to her family physician. We suggested avoiding propofol and withholding hydroxyzine for at least three preoperative days in the future.

Discussion

Dystonia is considered a movement disorder classically present with sustained muscle contractions and repetitive or patterned movements in varying body parts. It often produces a twisting posture and interestingly follows a task-specific movement, frequently called a sensory trick. Among the other hyperkinetic movement disorders like chorea, myoclonus, akathisia, tics, and tremors, our patient’s signs and symptoms tallied with dystonic movement disorder. She presents with this movement disorder only after anesthetics, therefore, it can be considered as a dystonic reaction to anesthetics or as a complex interaction of anesthetic with medication she is already on.

Sustained or patterned contractions of agonist and antagonistic muscles in limbs, trunk, and neck result in involuntary movements and twisting posture. She presented with lower limb dystonia; however, she suffered from dysphonia following anesthetics in the past, which can be a form of adductor laryngeal spasmodic dystonia resulting in voice tremors and affecting loudness of the voice. Further, spasticity in the neck and facial muscles could result in life-threatening airway emergencies with upper airway obstruction. To our knowledge, this is the first case report describing laryngeal dystonia following anesthetic.

Dystonic reactions during the perioperative period are rare and mostly occur during induction and emergence, which usually be transient [1,2]. The majority of the cases of perioperative movement disorders were correlated to propofol or antiemetic agents such as metoclopramide or ondansetron. In our case, ondansetron had been used without any ill effects previously. Propofol was used as the induction agent in all her previously reported dystonic events and, on one occasion, as part of total intravenous anesthesia, where severe lower limb dystonia and aphasia were reported.

A clear pattern of worsening severity and duration of the dystonic reaction after each anesthetic was noted in our case, and such a graded response following anesthesia has been described previously.

Even though the pathophysiology of dystonia is not clearly understood, several mechanisms have been described by various authors. The classic description is an imbalance between inhibitory dopaminergic and excitatory cholinergic systems in the basal ganglia. Recent research suggests that dystonia is a motor circuit disorder rather than a simple neurochemical imbalance confined to the basal ganglia. Further, studies involving tonic vibration reflex stimulus suggest that muscle spindle afferent pathways carry kinaesthetic inputs to the cerebellum [5]. Sensory inputs are directed to the basal ganglia and mainly to the striatum via the thalamus. These pathways could explain the sensory elements of dystonia.

A compartment model in the striatum could explain some of the findings related to our patient’s presentation. Striosomes and matrices are considered neurochemically distinct compartments in the striatum (Figure 1). Of that, a much larger compartment, the matrix, comprises direct excitatory and indirect inhibitory neurons [5]. Excitatory outputs mediate via dopamine 1 (D1) receptors and indirect inhibitory outputs involve D2 receptors. Neurons in the ribosome get inputs from the limbic system. Cholinergic neurons influence the activation of striosomes. These ribosomal neurons have inhibitory projections into substantia nigra pars compacta (SNc) which act via gamma-aminobutyric acid (GABA) receptors. Outputs from SNc have feedback into striosome and matrix mediated via dopamine. It activates predominantly the direct pathway of matrix via D1 receptors giving rise to an excitatory motor response.

 

Three-compartmental-model-of-basal-ganglia-circuit-with-direct-and-indirect-motor-outputs.-
Figure 1: Three compartmental model of basal ganglia circuit with direct and indirect motor outputs.

Source: [5].

GABA, gamma-aminobutyric acid; SNc, substantia nigra pars compacta

Various extrapyramidal side effects have been reported about the use of propofol. The mechanism of such movement disorders is largely unknown but commonly relates to an imbalance of cholinergic and dopaminergic effects in basal ganglia. Propofol is known to inhibit fatty amide hydrolase, which metabolizes the endocannabinoid anandamide (AEA). This leads to a significant increase in the whole brain content of AEA following propofol administration [6]. The endocannabinoid system has a fundamental role in the control of movements. Therefore, changes in the endocannabinoid system could partly explain the effects on movement disorders after propofol administration.

Hydroxyzine is a first-generation antihistamine that acts as an H1 receptor inverse agonist. It is commonly used in the treatment of itchiness, insomnia, motion sickness, and anxiety. Further, it has an antagonistic effect on D2 receptors. That could result in an inhibition of the indirect inhibitory pathway at the striatum, resulting predominance of excitatory direct motor output. There are cases of dystonia following hydroxyzine administration in the literature [4], and involuntary motor activities reported in hydroxyzine (ATARAXTM) product information. Studies have shown that long-term prescription of hydroxyzine can cause tardive dyskinesia [7].

Our patient was on hydroxyzine for her skin condition as a long-term medication. The patient had undergone a few general anesthetics without dystonic reactions before taking the treatment with hydroxyzine. However, since starting on hydroxyzine, she subsequently had dystonic reactions after each general anesthetic she had undergone. It is unclear how hydroxyzine interacts with general anesthetics, and we could not find previously published cases highlighting such interaction.

Acute dystonia is commonly treated with anticholinergic medications such as benztropine and procyclidine. Symptoms generally improve within 10 to 30 minutes. Intravenous benzodiazepines are effective in acute dystonic reactions.

Conclusions

Movement disorders during the perioperative period are rare and transient. Atypical presentations of dystonic reactions can occur in the form of laryngeal dystonia and dysphonia. Even though postoperative dystonic reactions are commonly attributed to propofol and antiemetic medications, we conclude that they can be related to other dopamine antagonists like hydroxyzine. Therefore, detailed patient history, consideration of possible drug interactions, and correlation of clinical findings with movement disorders are all important for the diagnosis. Alterations of anesthetic techniques avoiding propofol and holding hydroxyzine are advisable in such rare clinical situations. Early diagnosis of perioperative movement disorders will prompt specific treatments, such as anticholinergic medications for acute postoperative dystonia.

References

  1. Ananthanarayan C, Blight K: Dystonic reaction after anesthesia. Can J Anaesth. 2001, 48:101. 10.1007/BF03019825
  2. Patel M, Park BL: Acute dystonic reaction in the upper extremity following anesthesia. Cureus. 2022, 14:e31166. 10.7759/cureus.31166
  3. Simonyan K, Berman BD, Herscovitch P, Hallett M: Abnormal striatal dopaminergic neurotransmission during rest and task production in spasmodic dysphonia. J Neurosci. 2013, 33:14705-14. 10.1523/JNEUROSCI.0407-13.2013
  4. Gunduz S,Karacayir N, Ozkan M: Hydroxyzine induced dystonia. Austin Pediatr. 2016, 3:1026.
  5. Kaji R, Bhatia K, Graybiel AM: Pathogenesis of dystonia: is it of cerebellar or basal ganglia origin?. J Neurol Neurosurg Psychiatry. 2018, 89:488-92. 10.1136/jnnp-2017-316250
  6. Patel S, Wohlfeil ER, Rademacher DJ, et al.: The general anesthetic propofol increases brain N-arachidonylethanolamine (anandamide) content and inhibits fatty acid amide hydrolase. Br J Pharmacol. 2003, 139:1005-13. 10.1038/sj.bjp.0705334
  7. Clark BG, Araki M, Brown HW: Hydroxyzine-associated tardive dyskinesia. Ann Neurol. 1982, 11:435. 10.1002/ana.410110423

Peri-Operative Anesthetic Management of Left Atrial-Esophageal Fistula

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Author: Shakibai N et al

Cureus 16(7): e65520.

Abstract

Atrial-esophageal fistulas are rare and potentially fatal complications that can occur from radiofrequency ablation for the treatment of atrial fibrillation. Due to the proximity of the right atrium to the esophagus, thermal injuries can involuntarily lead to connections between the heart and esophagus. In this case study, a 67-year-old male developed an atrial-esophageal fistula following atrial fibrillation ablation. After discharge, the patient first presented with melena with a range of complications including aspiration, fever, atrial fibrillation, and neurological symptoms. The fistula was repaired promptly after diagnosis requiring meticulous planning by the anesthesia and surgical teams. The major consideration from anesthesiology was providing adequate oxygenation during one-lung ventilation via continuous positive airway pressure on the non-dependent lung. This case also highlights the need for recognizing and managing potential complications associated with catheter ablation procedures. A thorough understanding of these rare but critical events is essential for optimizing patient outcomes and minimizing mortality rates, and physicians and healthcare professionals must remain vigilant regarding such complications.

Introduction

Atrial-esophageal fistulas are a rare complication arising from atrial fibrillation radiofrequency ablation. They have an incidence of about 0.1%. This intervention can lead to thermal injuries affecting adjacent structures such as the esophagus as it is proximal to the site of endocardial ablation. Such injuries carry the risk of causing cerebral air embolism, gastrointestinal bleeding, and septic shock, often resulting in mortality rates ranging from 40% to 100% [1-2]. Current therapeutic modalities primarily involve surgical repair and placement of esophageal stents.

This case report discusses a patient diagnosed with an atrial-esophageal fistula following radiofrequency ablation. Early detection and prompt treatment initiation enhanced the patient’s chances of survival. We will discuss the signs and symptoms, treatment options, and anesthesia considerations related to atrial-esophageal fistulas. This case emphasizes the importance of meticulous preoperative planning, discusses different approaches to handling hypoxia during one-lung ventilation, and clarifies the risks of radiofrequency catheter ablations.

Case Presentation

A 67-year-old male with a pertinent medical history of obstructive sleep apnea, a prior history of tobacco use, a remote esophageal ulcer, and atrial fibrillation managed with metoprolol and rivaroxaban, underwent atrial fibrillation ablation. The procedure was performed under general anesthesia, utilizing endotracheal intubation and esophageal temperature monitoring. The peak temperature recorded during the surgery was 35.78 degrees Celsius. Following the procedure, he experienced no complications and was discharged home on the same day.

He presented to the emergency department (ED) seven days later with complaints of melena. Notably, he had taken his rivaroxaban dose the night before. There was a decrease in his hemoglobin level, dropping from a baseline of 13 to 10.8. Consequently, he received a transfusion of two units of packed red blood cells in the ED, and four-factor complexes were administered for the reversal of rivaroxaban. Subsequently, he underwent an esophagogastroduodenoscopy (EGD). During the procedure, intubation was challenging due to bleeding from the esophagus obscuring the airway, raising concerns for aspiration. Further examination revealed bleeding from an ulcer in the lower third of the esophagus, necessitating the placement of four stents.

Following the procedure, he remained intubated due to the possibility of aspiration during intubation, prompting a bronchoscopy which confirmed the presence of aspirated blood and clots. Post procedure, he developed a fever and was initiated on piperacillin-tazobactam and vancomycin. Additionally, he experienced episodes of atrial fibrillation with rapid ventricular response, for which labetalol was initiated. Due to a subsequent drop in blood pressure, he was transitioned to an amiodarone drip and briefly required pressors. Over the course of several days, his condition improved, he was extubated and later discharged.

Five days post discharge, he presented with acute left-sided weakness, near syncope, and palpitations, which spontaneously resolved. Upon evaluation, atrial fibrillation with rapid ventricular response was diagnosed, and he was initiated on a diltiazem drip. A computed tomography (CT) scan of the head ruled out a stroke. Shortly after, he became unresponsive and required intubation. Subsequent CT and barium swallow (Figures 1, 2) revealed an atrial esophageal fistula, implicating an air embolus as the likely cause of his transient neurological symptoms. A right thoracotomy was performed to repair the atrial-esophageal fistula, with significant emphasis placed on preoperative planning. Detailed discussions among the surgical and anesthesiology teams ensured alignment regarding the procedure’s execution and anticipated outcomes, with the perfusionist team on standby. Anticipating the possibility of cardiopulmonary bypass during the procedure, femoral venous and arterial access were established preemptively prior to surgery, in readiness for a potential cannulation. Furthermore, his endotracheal tube was exchanged for a double-lumen tube to facilitate lung isolation.

Computed-tomography-angiography-of-chest/abdomen/pelvis-with-contrast-showing-the-atrial-esophageal-fistula-
Figure 1: Computed tomography angiography of chest/abdomen/pelvis with contrast showing the atrial esophageal fistula
Esophageal-barium-swallow-showing-irregularity-in-the-mid-posterior-wall-of-the-esophagus,-associated-with-a-large-leak-if-contrast-in-the-mediastinum
Figure 2: Esophageal barium swallow showing irregularity in the mid posterior wall of the esophagus, associated with a large leak if contrast in the mediastinum

Despite various attempts to improve oxygen saturation intraoperatively, a collapsed lung necessitated continuous positive airway pressure mode, resulting in improved oxygen saturation (SpO2) levels. The surgical repair proceeded without complications. However, post procedure, he exhibited an inability to follow commands or perform purposeful movements, prompting the decision to maintain intubation. Subsequently, his double-lumen tube was replaced with a single-lumen tube using a cook catheter under video visualization. Given his esophageal condition, transesophageal echocardiography was not performed. Instead, a transthoracic echocardiogram performed in the intensive care unit (ICU) revealed normal biventricular function, absence of pericardial effusion, and an ejection fraction of approximately 60%.

Within two days, he was successfully extubated in the ICU; however, his left-sided weakness remained. Brain magnetic resonance imaging (MRI) (Figure 3) findings indicated features consistent with an acute embolic stroke affecting multiple areas of the anterior and posterior circulation, along with involvement of the left posterior temporal lobe. Concurrently, blood cultures yielded streptococcal growth, raising concerns for sepsis and potential infective endocarditis.

MRI-findings-suggestive-of-acute-embolic-stroke
Figure 3: MRI findings suggestive of acute embolic stroke
His hospitalization was further complicated by the development of an esophageal leak, necessitating the placement of esophageal stents. Following the stabilization of his medical condition, he transitioned to the inpatient rehabilitation unit for comprehensive care. Ultimately, upon achieving medical stability and functional improvement, he was discharged to undergo outpatient physical and occupational therapy.

Discussion

Atrial esophageal fistulas are rare complications of catheter ablations, occurring in 0.1% of cases [3]. Although infrequent, they pose a significant risk of mortality, with reported incidences ranging from 40% to 100%. It is imperative for anesthesiologists and surgeons to be cognizant of this complication and to devise a strategic plan for its treatment and the management of any unforeseen events that may arise.

These fistulas develop when heat generated by the catheter causes thermal damage to the esophagus and compromises its blood supply, resulting in ischemic injury [4]. Esophageal temperature probes are employed to monitor the temperature of the esophagus during the procedure. Studies indicate that temperatures exceeding 41°C are more likely to induce damage [4]. Despite variations in the literature, some studies have suggested a lack of correlation between esophageal injury and esophageal temperature [5].

One-lung ventilation is a commonly employed technique in thoracic surgery to optimize visualization of the surgical field. Hypoxia, while infrequent during one-lung ventilation (approximately 4% incidence), may escalate in cases of hemodynamic compromise. It can arise due to right-to-left intrapulmonary shunting and heightened atelectasis in the dependent lung, exacerbating hypoxemia. This decrease in ventilation can stimulate hypoxic pulmonary vasoconstriction, leading to pulmonary vasoconstriction and further exacerbating intrapulmonary shunting. Consequently, this hinders blood flow to the well-oxygenated and dependent lung [6].

In the event of hypoxia, the fraction of inspired oxygen (FiO2) should be escalated to 1.0 and the positive end-expiratory pressure (PEEP) should be increased. Verification of the proper positioning of the bronchial blocker or double-lumen tube should be conducted using a flexible fiberoptic bronchoscope. Utilizing passive oxygenation to the non-dependent lung or even application of continuous positive airway pressure, as was employed for our patient during hypoxemia, can facilitate resolution. This mechanism is believed to operate passively, enabling oxygen uptake by the alveoli. If the patient continues to desaturate, then it needs to be discussed with the surgeon, and the patient should be transitioned to two-lung ventilation.

Conclusions

While atrial esophageal fistulas constitute a rare yet significant concern in catheter ablation procedures, other potential adverse outcomes encompass vascular complications, stroke or ischemic attack, pericardial effusion, tamponade, pulmonary vein stenosis, and phrenic nerve injury. Physicians and healthcare professionals must remain vigilant regarding such complications.

References

  1. Ghia KK, Chugh A, Good E, et al.: A nationwide survey on the prevalence of atrioesophageal fistula after left atrial radiofrequency catheter ablation. J Interv Card Electrophysiol. 2009, 24:33-6. 10.1007/s10840-008-9307-1
  2. Dagres N, Kottkamp H, Piorkowski C, et al.: Rapid detection and successful treatment of esophageal perforation after radiofrequency ablation of atrial fibrillation: lessons from five cases. J Cardiovasc Electrophysiol. 2006, 17:1213-5. 10.1111/j.1540-8167.2006.00611.x
  3. Gupta A, Perera T, Ganesan A, et al.: Complications of catheter ablation of atrial fibrillation: a systematic review. Circ Arrhythm Electrophysiol. 2013, 6:1082-8. 10.1161/CIRCEP.113.000768
  4. Dagres N, Anastasiou-Nana M: Prevention of atrial-esophageal fistula after catheter ablation of atrial fibrillation. Curr Opin Cardiol. 2011, 26:1-5. 10.1097/HCO.0b013e328341387d
  5. Cummings JE, Schweikert RA, Saliba WI, et al.: Assessment of temperature, proximity, and course of the esophagus during radiofrequency ablation within the left atrium. Circulation. 2005, 112:459-64. 10.1161/CIRCULATIONAHA.104.509612
  6. Open Anesthesia: Hypoxia during one-lung ventilation. (2023). Accessed: March 29, 2024: https://www.openanesthesia.org/keywords/hypoxia-during-one-lung-ventilation/.

Factor Eight Inhibitor Bypass Activity use in cardiac surgery: A propensity matched analysis of safety outcomes

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AUTHORS: Joshua A. Nicholas, MD et al 
Anesthesiology  August 2024.
BACKGROUND

Bleeding during cardiac surgery may be refractory to standard interventions. Off-label use of Factor Eight Inhibitor Bypass Activity (FEIBA) has been described to treat such bleeding. However, reports of safety, particularly thromboembolic outcomes, show mixed results and reported cohorts have been small.

METHODS

Adult patients undergoing cardiac surgery on cardiopulmonary bypass between July 1, 2018 and June 30, 2023 at Stanford Hospital were reviewed (n=3335). Patients who received FEIBA to treat post-cardiopulmonary bypass bleeding were matched with those who did not by propensity scores in a 1:1 ratio using nearest neighbor matching (n= 352 per group). The primary outcome was a composite outcome of thromboembolic complications including any one of deep vein thrombosis (DVT), pulmonary embolism (PE), unplanned coronary artery intervention, ischemic stroke, and acute limb ischemia, in the postoperative period. Secondary outcomes included renal failure, reoperation, postoperative transfusion, ICU length of stay (LOS), and 30-day mortality.

RESULTS

704 encounters were included in our propensity matched analysis. The mean dose of FEIBA administered was 7.3 ±5.5 units/kg. In propensity matched multivariate logistic regression models there was no statistically significant difference in odds ratios for thromboembolic outcomes, ICU LOS, or mortality. Patients who received >750 units of FEIBA had an increased odds ratio for acute renal failure (OR 4.14; 95% CI 1.61 to 10.36, p <0.001). In multivariate linear regression, patients receiving FEIBA were transfused more plasma and cryoprecipitate postoperatively. However, only the dose range of 501-750 units was associated with an increase in transfusion of RBCs (β 2.73; 95% CI 0.68 to 4.78; p=0.009), and platelets (β 1.74; 95% CI 0.85 to 2.63; p <0.001).

CONCLUSIONS

Low dose FEIBA administration during cardiac surgery does not increase risk of thromboembolic events, ICU LOS, or mortality in a propensity matched cohort. Higher doses were associated with increased acute renal failure and postoperative transfusion. Further studies are required to establish the efficacy of activated factor concentrates to treat refractory bleeding during cardiac surgery.

Assessing the Risks and Benefits of Hypotensive Anesthesia and Piezosurgical Instruments in Bimaxillary Surgery

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Authors: Yamamura K et al

Cureus 16(8): e67394.

Abstract

The challenge in bimaxillary surgery lies in significant intraoperative bleeding, prompting various strategies to minimize blood loss. Among the methods considered for controlling intraoperative bleeding, hypotensive anesthesia and the use of piezosurgical instruments (Osada, Tokyo, Japan) have been explored. However, hypotensive anesthesia may have adverse effects on cardiac function, and surgical time is likely to be prolonged when using piezosurgical instruments. This study retrospectively examined whether the combined use of hypotensive anesthesia and piezosurgical instruments reduces intraoperative bleeding and whether the combination impacts cardiac function. The combination of hypotensive anesthesia and piezosurgical instruments significantly reduced intraoperative bleeding. Furthermore, the combination was associated with a significantly higher incidence of tachycardia, particularly with the use of nicardipine. Additionally, the combination significantly lengthened the duration of the surgery and may have increased the burden on cardiac function. Landiolol was effectively employed to manage tachycardia. When selecting hypotensive anesthesia as a means to limit bleeding, proactive preparation and preventive small-dose administration of landiolol could be beneficial in managing the potential occurrence of tachycardia.

Introduction

Orthognathic surgery is a well-established method for correcting dentofacial deformities, often necessitating bimaxillary surgery [1]. Bimaxillary surgery, which combines mandibular and maxillary osteotomies, allows for the alteration of the occlusal plane and the three-dimensional repositioning of the jaws. Many of the patients undergoing bimaxillary surgery are healthy young adults with minimal systemic complications [2]. However, in recent years, there has been an increasing incidence of elderly patients undergoing bimaxillary surgery, potentially making perioperative management more challenging [3].

Bimaxillary surgery can be associated with significant blood loss and the need for transfusion, emphasizing the growing importance of exploring alternative measures with minimal adverse effects to reduce intraoperative hemorrhage [2,4].

One approach to mitigating blood loss during bimaxillary surgery involves the use of hypotensive anesthesia [1]. Hypotensive anesthesia is a technique in which blood pressure is intentionally lowered during surgery to reduce bleeding and improve surgical field visibility [1,5]. While its potential for reducing intraoperative bleeding has been recognized, studies examining its efficacy specifically in bimaxillary surgery have produced conflicting findings [1]. Moreover, concerns regarding vital organ hypoperfusion during hypotensive anesthesia have been raised in other studies [1,5]. Notably, cardiovascular complications significantly contribute to postoperative morbidity and mortality following non-cardiac surgeries [6]. These complications extend hospital stays, escalating healthcare costs, and constitute a leading cause of perioperative mortality [7]. Elderly patients, in particular, exhibit a higher prevalence of coronary artery disease, amplifying the risk of cardiac events during the perioperative period [8].

Piezoelectric instruments utilize ultrasonic microvibrations of 60-200 μm/s at frequencies of 24-29 kHz to cut mineralized tissue while leaving soft tissue unharmed. These instruments provide an alternative strategy for bleeding management, albeit with potential challenges such as prolonged surgical duration [9]. Further investigation is warranted to understand their impact on increased bleeding and cardiac function in relation to the extended surgical time. Both hypotensive anesthesia and piezoinstruments are being explored as distinct approaches, and a comprehensive, sequential evaluation of both methods is unprecedented in the existing literature.

Therefore, the aim of this study was to investigate whether the combination of hypotensive anesthesia and piezosurgical instruments affects blood loss during bimaxillary surgery while ensuring intraoperative safety. Particular attention was paid to changes in circulatory function during surgery to assess whether the combination of hypotensive anesthesia and piezosurgical instruments imposes undue cardiac stress.

Materials & Methods

This study received approval from the Ethics Committee of the Defense Medical University Hospital, Japan Permit Number, 4859. Data were collected from the medical records of 30 patients who underwent bimaxillary surgery between 2015 and 2023. To be included in the study sample, patients had to meet the following criteria: they were classified as having American Society of Anesthesiologists (ASA) physical status I or II and had no significant systemic illnesses, such as severe cardiovascular, respiratory, renal, or hepatic diseases, which were excluded from the ASA categorization. Examples of excluded conditions include uncontrolled hypertension, severe asthma, chronic obstructive pulmonary disease, and advanced diabetes mellitus. Additionally, preoperative electrocardiogram (ECG) examinations confirmed the absence of waveform patterns suggestive of severe ischemic heart disease in all patients, who were aged between 18 and 80 years and included both males and females.

In all cases, continuous monitoring of patients’ vital signs, including electrocardiography, pulse oximetry, temperature probe, and capnography, was conducted during surgery and the recovery period. A transducer connected to an indwelling arterial catheter was used to continuously monitor mean arterial pressure (MAP) in subjects during surgery. In hypotensive anesthesia, the target MAP was set between 50 and 65 mmHg.

The anesthesia induction technique was uniform across all cases, with an induction dose of propofol administered at 2 to 2.5 mg/kg. Fentanyl at 1 μg/kg was used to suppress intubation responses. Rocuronium at 0.6 mg/kg was administered as a muscle relaxant. All patients received cefmetazole 1 g or cefazolin 1 g immediately after induction, and the same antimicrobial agent in the same dose was administered every three hours.

The primary anesthesia maintenance agents included propofol, sevoflurane, and desflurane. Remifentanil at 0.2 to 0.35 μg/kg/minute was administered for analgesia maintenance. In the hypotensive anesthesia group, medications such as nicardipine, a calcium channel blocker, or alprostadil alfadex, a prostaglandin E1 preparation, were continuously infused to maintain the target MAP and bolus dose as needed.

All patients underwent a Le Fort I osteotomy and a bilateral sagittal split osteotomy (BSSO). Xylocaine 2% with 1:80,000 epinephrine was used for local infiltration anesthesia of the lower jaw and upper jaw. Firm fixation of bone segments was achieved using plates and screws, with no intermaxillary fixation applied postoperatively. Piezosurgical instruments were used in all cases in the hypotensive anesthesia group (Osada, Tokyo, Japan). Dexamethasone 6.6 mg or betamethasone 2 mg was administered before the conclusion of surgery in all cases. No transfusions were administered to any of the patients.

Intravenous fluid, urine output, and blood loss were measured. Intravenous fluid measurements were taken and recorded by the anesthesia team, while urine output and blood loss were measured by nurses and recorded by the anesthesia team. To measure intraoperative blood loss, a consistent method was applied to all cases. It involved subtracting the volume of saline used for irrigation during suctioning, both during washing and cutting, from the total volume in the suction canister. Additionally, the increase in weight of the gauze used (1 g = 1 ml) was added to determine the amount of blood loss. Furthermore, preoperative and postoperative day one blood tests were conducted, and using the Hct value, the estimated perioperative blood loss was calculated according to the equation proposed by Gross [10].

Statistical analysis was performed using GraphPad Prism 8 (MDF, Boston, USA). The two anesthesia groups were compared using a one-way analysis of variance (ANOVA), with unpaired t-tests used as post hoc tests for age and BMI. Fisher’s exact test was employed for the analysis of sex, while the Mann-Whitney U test was used for other variables. Fisher’s exact test was also utilized for the analysis of the occurrence of intraoperative tachycardia and the use of hypotensive agents. All values are presented as the mean ± standard deviation (± SD). Statistical significance was defined as p < 0.05.

Results

An overview of the data is presented in Tables 1, 2, and Figure 1. There were no significant differences between the two groups in terms of age, BMI, or fluid replacement. The operative and anesthetic times were significantly longer in the hypotensive anesthesia group compared to the normal anesthesia group. Additionally, the urinary output in the hypotensive anesthesia group was significantly lower than in the normal anesthesia group. Concerning blood loss, the hypotensive anesthesia group exhibited significantly less bleeding compared to the normal anesthesia group. The estimated perioperative blood loss calculated from Hct values in preoperative and postoperative day one blood tests did not show a significant difference between the two groups.

Hypotensive anesthesia group (n = 13) Normal anesthesia group (n = 17) p-value
Variables Mean ± SD Mean ± SD
Age (year) 27.5 ± 6.8 23.8 ± 5.6 0.1062
BMI (kg/m2) 22.4 ± 1.8 20.0 ± 4.7 0.0817
Fluid replacement (ml) 2635.7 ± 709.7 2462.5 ± 575.5 0.3291
Urinary output (ml) 684.1 ± 325.2 1170.6 ± 550.7 0.0045
Operative time (minutes) 447.2 ± 39.6 303.2 ± 90.8 < 0.0001
Anesthetic time (minutes) 521.2 ± 40.1 375.9 ± 107.3 < 0.0001
Blood loss (ml) 227.8 ± 112.2 387.8 ± 171.6 0.0059
Estimated perioperative blood loss calculated from Hct (ml) 174.6 ± 46.2 208.0 ± 69.9 0.3291
Table 1: Comparisons of the outcome variables.

BMI: Body mass index, Hct: Hematocrit

Variables Time after landiolol start (min)
0 10
Mean ± SD Mean ± SD
MAP (mm Hg) 61.3 ± 4.8 60 ± 1.6
Heart rate (bpm) 114.5 ± 6.6 94.3 ± 5.7
Table 2: Details on the use of landiolol for tachycardia.

Landiolol maintenance dose (Mean ± SD): 6.75 ± 2.4 μg/kg/min

MAP: Mean arterial pressure

Comparisons-of-the-outcome-variables.
Figure 1: Comparisons of the outcome variables.

HA: Hypotensive anesthesia, NA: Normal anesthesia, *p < 0.05 (Mann-Whitney U test).

The hypotensive anesthesia group had a significantly higher incidence of tachycardia compared to the normal anesthesia group. Among the six cases where nicardipine was used, tachycardia occurred in three cases, suggesting a tendency for tachycardia to occur when nicardipine was used. No cases of tachycardia occurred when alprostadil alfadex was used. In the four cases where tachycardia occurred, adequate analgesia was confirmed before the administration of landiolol, and heart rate control was excellent in all cases.

As for postoperative complications, only one case of postoperative infection was observed in the hypotensive anesthesia group, and no other significant complications, except for nerve damage, were noted in either group.

Discussion

Bimaxillary surgery involves various innovations to minimize blood loss, including the use of induced hypotensive anesthesia, ultrasonic cutting instruments, tranexamic acid, and local anesthesia [2,4].

In bimaxillary surgery, induced hypotensive anesthesia is administered using inhaled anesthetics, intravenous drug therapy, or a combination of both, taking advantage of the blood pressure-lowering effects of agents such as propofol and sevofluran [11,12]. Maintaining the desired hypotension during bimaxillary surgery can often be challenging, and in such cases, the concurrent use of drugs such as nicardipine, nitroprusside, labetalol, nitroglycerin, diltiazem, and prostaglandin E1 derivatives may be necessary [1,13,14]. Among these drugs, nicardipine is commonly used due to its affordability, accessibility, and ease of use [13]. Additionally, the use of piezosurgical instruments in bimaxillary surgery minimizes soft tissue damage and intraoperative blood loss but may extend surgical time, which is a drawback [4,15]. The extension of surgical time in bimaxillary surgery is known to significantly increase relative intraoperative blood loss [15]. In this study, the combination of hypotensive anesthesia and piezosurgical instruments resulted in significantly longer surgical times, likely attributed to the use of piezosurgical instruments, but did not result in increased blood loss. From these findings, it is suggested that the extension of surgical time with piezosurgical instruments may not be associated with an increase in intraoperative blood loss. This study used propofol and sevoflurane as maintenance anesthetics, and in cases where the target hypotension was not achieved, alprostadil alfadex (a prostaglandin E1 derivative) was used. The MAP was maintained at 50-70 mmHg during hypotensive anesthesia, which was consistent with values reported in other studies [1,16].

In this study, the hypotensive anesthesia group had significantly less blood loss compared to the normal anesthesia group, suggesting that the combination of hypotensive anesthesia and piezosurgical instruments was effective in reducing blood loss. While visual estimation is the most widely used method for measuring blood loss during surgery, it is not always accurate, especially in cases of hidden bleeding [17]. In such cases, several formulas using blood test results are used to estimate blood loss [17,18]. In this study, preoperative and postoperative hematocrit values were used to estimate blood loss, with the result that there was no significant difference in the estimated blood loss between the normal and hypotensive anesthesia groups. This outcome may be attributed to the fact that both groups received equivalent volume infusions; however, the normal anesthesia group exhibited a higher urinary output, resulting in an elevated postoperative hematocrit value, consequently leading to a lower calculated blood loss.

Hypotensive anesthesia, particularly in non-cardiac surgery patients, has been associated with adverse effects when the MAP falls below 60-70 mm Hg, even for short durations [19]. Prolonged maintenance of the MAP below 65 mmHg during surgery is known to increase the risk of organ dysfunction, with longer durations associated with higher postoperative mortality rates and organ dysfunction incidence [20]. Furthermore, a threshold estimated to cause a gradual increase in the odds of myocardial injury is reported to be a MAP of 65 mmHg during surgery [21]. It is recommended to maintain the MAP above 65 mmHg during surgery, especially after induction [22]. To avoid increasing oxygen consumption and causing ischemia in the unprepared heart, it is crucial to maintain a balance between myocardial oxygen supply and demand, which is best achieved by avoiding hypotension, tachycardia, and hypertension [23]. Maintaining cardiac output is particularly important for non-cardiac surgery patients [24]. The use of nicardipine has been associated with a relatively high incidence of reflex tachycardia, occurring in 17.2% of cases over a short period of time [13]. In this study, nicardipine was continuously administered for a relatively long period, leading to increased myocardial oxygen consumption and potentially a higher risk of circulatory dysfunction.

Beta-blockers are the preferred agents for managing tachycardia-induced arrhythmias, but their use can increase side effects such as stroke and severe bradycardia in low-risk patients, potentially worsening patient outcomes [25]. Among beta-blockers, esmolol and landiolol are short-acting, beta-1 selective agents, have no bronchoconstrictive effects, have very short half-lives, and provide rapid onset, allowing for continuous intravenous infusion and excellent adjustability [26]. Esmolol may be risky in cases with unstable hemodynamics due to its blood pressure-lowering effect, while landiolol effectively lowers heart rate without lowering blood pressure, making it favorable for rate control [27]. The landiolol group had a significantly higher rate of returning to sinus rhythm compared to the diltiazem group, with a lower incidence of hypotension and bradycardia, indicating safety [28]. Preventive landiolol administration has been suggested to be effective in preventing tachycardia in non-cardiac surgery cases [29,30]. However, there have been no reports of landiolol administration for intraoperative tachycardia in orthognathic surgery. In this study, landiolol was administered for the management of tachycardia, resulting in early improvement in circulatory function. Therefore, the administration of landiolol may be effective for patients undergoing orthognathic surgery who present with tachycardia.

Limitations of this study include the inability to discern the individual impacts of hypotensive anesthesia and the use of piezosurgical instruments, as they were employed concurrently. Consequently, it remains unclear which factor primarily contributed to the observed reduction in blood loss. Additionally, this study, being retrospective and relatively small in scale with a sample size of 30 patients, is inherently constrained by its methodology. Variations in anesthesia methods and hypotensive techniques further introduce potential confounding variables, both known and unknown. Moreover, the absence of a universally accepted gold standard for accurately calculating blood loss and estimating total blood volume necessitated the adoption of the formula proposed by Gross, which, while widely utilized, does not fully address the challenge of precise measurement in this context.

Conclusions

The combination of hypotensive anesthesia and piezosurgical instruments during bimaxillary surgery effectively reduced blood loss. However, tachycardia may occur during hypotensive anesthesia, especially when nicardipine is used, and may lead to a strain on cardiac function. The study demonstrated the effectiveness of landiolol in managing tachycardia. For patients undergoing orthognathic surgery who present with tachycardia, the preparation and preventive use of landiolol may be beneficial.

References

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From Dollars to Sustainability: A Reinvigorated Goal for Anesthesiologists

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Authors: Radhika Chalasani, MD, MS et al 
ASA Monitor September 2024, Vol. 88, 1–5.

The inexorable rise in health care costs has brought ever-greater emphasis on cost reduction in all aspects, including anesthesia care. Intraoperative anesthesia-related expenditures comprise upward of 6% of the total hospital cost for an inpatient procedure (Curr Opin Anaesthesiol 2012;25:221-5). We describe efforts at Ohio State to reduce both direct and environmental procedural costs while maintaining environmental stewardship.

We initially focused on curbing the use of desflurane. Desflurane’s rapid action and its favorable pharmacokinetic profile make it a desirable volatile anesthetic. However, it has both direct costs (it is approximately 10 times more expensive than isoflurane and four times more expensive than sevoflurane) and environmental costs (BMJ 2022;377:o1301). The global warming potential (GWP) of desflurane is about 3,700, approximately 10 times greater than sevoflurane and twice that of isoflurane. Even more daunting is the fact that yearly emissions of inhaled anesthetic agents in CO2 equivalents are comparable to those emitted from 1 million cars or one coal-fired power plant (Br J Anaesth 2010;105:760-6).

Current recommendations to reduce the environmental burden from waste anesthesia gases highlight the importance of avoiding desflurane and nitrous oxide, lowering fresh gas flows, and considering total intravenous anesthesia (TIVA) and regional anesthesia techniques where applicable (ASA Monitor 2023;87:24).

Our efforts to reduce desflurane use were initially unsuccessful. Our departmental communications were focused on reducing pharmaceutical costs of desflurane. Despite repeated messaging from 2014 to 2017, our desflurane expenditures continued to rise, reaching their peak in 2017 (Figure 1).

Figure 1: Timeline of communication within the Department of Anesthesiology at The Ohio State University Wexner Medical Center from 2014-19, with initial emphasis on cost reduction, and later years bringing environmental awareness.

Figure 1: Timeline of communication within the Department of Anesthesiology at The Ohio State University Wexner Medical Center from 2014-19, with initial emphasis on cost reduction, and later years bringing environmental awareness.

In 2018, we started to include the environmental costs of desflurane, focusing on sustainable anesthesia practice. We first launched an informative Grand Rounds presentation, followed by a survey to assess knowledge and willingness of anesthesia professionals to change practice to reduce negative impacts on the environment (Figures 2 and 3). We found that through direct interaction, 90% of our anesthesiologists were willing to change practice. Now we had an opportunity for significant change to occur! We added visual aids to the OR, most notably on the anesthesia machine, to cue anesthesiologists to reduce desflurane usage. This included a “weeping” polar bear sticker (Figure 4) highlighting CO2 equivalents.

Figure 2: Survey results – barriers to reducing environmental impact from anesthesia gas usage.

Figure 2: Survey results – barriers to reducing environmental impact from anesthesia gas usage.

 

Figure 3: Survey results – anesthesia professionals' willingness to change practice to reduce environmental impact of anesthetic gases.

Figure 3: Survey results – anesthesia professionals’ willingness to change practice to reduce environmental impact of anesthetic gases.

Figure 4: Sticker placed on anesthesia machines to serve as a visual cue. Includes table with tropospheric lifetime and 20-year global warming potential of inhaled anesthetics (Jt Comm J Qual Patient Saf 2015;41:522-8).

Figure 4: Sticker placed on anesthesia machines to serve as a visual cue. Includes table with tropospheric lifetime and 20-year global warming potential of inhaled anesthetics (Jt Comm J Qual Patient Saf 2015;41:522-8).

In the first year after this initiative, desflurane use decreased by 31%, with an overall decrease of 46% in the CO2 equivalents per minute of OR time. This momentum continued to carry over, as there was a steady decline of 70% in the following years (Figure 5).

“Desflurane’s rapid action and its favorable pharmacokinetic profile make it a desirable volatile anesthetic. However, it has both direct costs (it is approximately 10 times more expensive than isoflurane and four times more expensive than sevoflurane) and environmental costs.”

Figure 5: Desflurane spend from 2014-23 at the Department of Anesthesiology, The Ohio State University Wexner Medical Center.

Figure 5: Desflurane spend from 2014-23 at the Department of Anesthesiology, The Ohio State University Wexner Medical Center.

An additional effort focused on reducing the use of inhaled volatile anesthetics and nitrous oxide. Recent randomized controlled trials comparing TIVA and inhaled anesthetics in obstructive sleep apnea (OSA) surgery demonstrated improved recovery times and decreased need for supplemental oxygen requirements in the TIVA cohort (Laryngoscope 2023;133:984-92). Now that remifentanil is generic, the direct costs of TIVA are comparable to inhaled anesthetics, while the environmental cost is substantially less (Anesth Analg 2019;128:13-5).

“Even more daunting is the fact that yearly emissions of inhaled anesthetic agents in CO2 equivalents are comparable to those emitted from 1 million cars or one coal-fired power plant.”

Further sustainability and cost-reduction strategies are on the way. Newer anesthesia machines with capabilities to automatically titrate end-tidal concentrations of volatile anesthetic agent and flow rates are enabling cost reductions while improving sustainability by automating green practices. Evolving technology improvements with enhanced reporting metrics and dashboards that provide information on volatile agent costs and CO2 equivalents per case and per anesthesiologist can drive accountability in the future.

In conclusion, we found that anesthesiologists were not motivated by the hospital’s requests to reduce costs. However, anesthesiologists were highly motivated by environmental sustainability. Perhaps the latter was seen as more meaningful, potentially impacting their personal lives and those of their families. Reducing direct and environmental costs while maintaining patient safety are mutually compatible goals. Our experience may help other institutions align patient care priorities with economically and environmentally responsible provision of anesthesia care.

9 pediatric hospitals cut gas emissions from anesthetics over 50%

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Author: Claire Wallace
Becker’s ASC Review

Project Spruce, a consortium of nine pediatric hospitals, has successfully cut greenhouse gas emissions from inhaled anesthetics by over 50% across its nine partners.

The consortium aims to improve anesthesia protocols, increase knowledge of the environmental impact of anesthesia and provide data-driven feedback, according to a Sept. 19 press release.

Across the consortium 3,900 metric tons of carbon dioxide have been stopped from entering the atmosphere. That is the equivalent of driving a gas-powered car about 10 million miles.

The healthcare sector is currently a major contributor to climate change, producing 2 gigatons of carbon dioxide equivalents each year.

Inhaled anesthetics contribute greatly to the issue, as several major systems nationwide have discontinued the use of desflurane, which remains in the atmosphere for 14 years and has a global warming impact 2,500 times greater than that of carbon dioxide.

According to Health Care Without Harm’s 2019 Climate Footprint report, healthcare accounts for 8.5% of U.S. greenhouse gas emissions and 4.4% globally. The operating room is a major emissions hotspot, responsible for up to 40% of a hospital’s emissions, largely due to the use of long-lasting anesthetic gasses like nitrous oxide, according to the release.

Project Spruce was launched in 2021 by founding site Seattle Children’s, which has reduced its anesthesia emissions tenfold by eliminating over 500,000 kilograms of carbon dioxide equivalents annually. The system has also seen a cost savings of $180,000 per year by increasing inhaled anesthetic efficiency and reducing waste.

The founding members of the Project Spruce consortium are Akron (Ohio) Children’s, Boston Children’s Hospital, BC Children’s Hospital in Vancouver, British Columbia, Children’s Hospital Colorado of Aurora, Dayton (Ohio) Children’s, Johns Hopkins Children’s Center in Baltimore, Nemours Children’s Health of Jacksonville, Fla., Seattle Children’s and The Children’s Hospital at Westmead, Australia.

Several additional institutions have recently joined the consortium as well.

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