Past medical history revealed BMI 89, heart failure with reduced ejection fraction (HFrEF), OSA, acute on chronic hypercapnic respiratory failure, moderate pulmonary edema on chest X-ray, baseline shortness of breath, asthma, diabetes type 2, chronic kidney disease stage 3, history of old and now new pulmonary embolisms, and now new onset atrial fibrillation. A transthoracic echocardiogram (TTE) showed LVEF 30% and RVEF 30%-40%. Previous TTE showed EF of 55%-60% within the last month.
Due to the multitude of risk factors, the patient was diverted to an electrophysiology lab with full anesthesia capabilities. Upon meeting the patient, the SpO2 was 91% on 6L NC with moderate dyspnea and tachypnea, heart rate 130-150, and she was extremely anxious. The cardiologist entered and a discussion ensued on the risk of any sedation and/or general anesthesia due to the patient’s extreme morbid obesity with concomitant severe cardiac comorbidities.
Minimal sedation was agreed upon by all three parties, with a high potential for intraprocedural memory and patient movement. Viscous lidocaine was used to anesthetize the pharynx. Low dose ketamine and very low dose propofol infusion were used for the procedure, with very gradual sedation. Right ventricular EF was under 20% and massively dilated with “smoke” on the TEE. The LVEF was 20% and dilated. Cardioversion was successful after no clot was found, and patient was in normal sinus rhythm.
Obesity is defined by the World Health Organization (WHO) as excessive or abnormal fat accumulation that poses negative health risks to patients. It is based on body mass index (BMI) and broken down into three categories, starting at a BMI of 30 kg/m2 and above. Class I is a BMI of 30-34.9, class II is a BMI of 35-39.9, and class III is a BMI of greater than 40. Some break down class III further into “super obese,” with a BMI of 50-59, and “super-super obesity,” with a BMI of 60 and higher (J Diabetes Res 2018;2018:3407306). The patient in the above scenario had a BMI of 89. Interestingly, Asian and South Asian populations have a downward shifted scale, with obesity starting at a BMI of greater than 25 instead of 30. As the BMI increases, so does the overall risk of a patient experiencing adverse outcomes.
Worldwide, the prevalence of adult obesity has nearly doubled, and quadrupled in adolescents, since 1990. In 2022, 43% (2.5 billion) adults 18 years and older were overweight, including over 890 million adults who were living with obesity (43% of men and 44% of women). Prevalence of overweight varied by region, from 31% in the WHO South-East Asia Region and African Region, to 67% in the Region of the Americas (asamonitor.pub/3U8f40K). The 2017-2018 National Health and Nutrition Examination Survey (NHANES) reports 43.4% of adults were identified as obese in the United States alone. In 2019, approximately 38.2 million children under 5 years old were overweight or obese. In 2016, over 340 million were overweight or obese in the 5-19 year-old category, with its incidence increasing over time. The prevalence of obesity is associated with several comorbid conditions, including dyslipidemia, type 2 diabetes, hypertension, coronary heart disease, obstructive sleep apnea (OSA), osteoarthritis, several cancers, and several other chronic conditions (Cureus 2023;15:e41565).
Caring for patients in the extreme morbidly obese classification (class III) can be challenging as they are at an increased risk across almost categories during an anesthetic. This patient subclass can be particularly challenging when the case typically does not require a secured airway; or if one does secure the patient’s airway, it may not be easy to extubate. Additionally, when these patients have concurrent comorbidities that can accompany morbid obesity, the complexity and risk of the anesthetic only increases. Certain “simple” cases turn daunting in patients who have not only severe cardiopulmonary compromise, but who also present with an acute exacerbation of one or more coexisting conditions on top of being morbidly obese.
Though the present case brings up several points, two main discussion topics stand out. First is the need to change plans on the fly in the face of patient complexity, and sometimes needing to use the “less is more” approach with certain high-risk patients. Collegial discussions as a “consultant in anesthesia” go a long way in helping proceduralists and patients understand the reasoning behind unconventional plans.
Second, we come to the topic of caring for our super morbid obese population. Airway management can be anatomically difficult due to an increased lingual fat content and tongue volume, causing airway obstruction and difficult intubation. Statistically, people with class III obesity tend to have shorter and more muscular necks, creating difficulties in mobility, both active and passive. Brodsky et al. showed that a neck circumference of 60 cm is associated with a 35% chance of having a difficult intubation. Another study by Riad et al. showed the cut off for a statistically significant difficult intubation was 33.5 cm with 100% sensitivity and 50% specificity (Saudi J Anaesth 2018;12:77-81). Technological advances with handheld videolaryngoscopes may help improve these statistics.
Obese patients also have relatively greater intra-abdominal pressure, with a resultant decrease in functional residual capacity, leading to higher degrees of pulmonary atelectasis. With increasing incidence of obesity, OSA also increases. This fact has several implications with anesthetics, including narcotic sensitivity, cardiac effects, and the need for postoperative ventilation.
Obesity itself – but also due to the chronic effects of secondary OSA – can lead to cardiac morphology changes, including increased risk of atrial fibrillation, other dysrhythmias, and function depression. The duration of morbid obesity is also closely correlated to the development of heart failure (Am J Cardiol 1997;80:736-40). After 20 years of obesity, the prevalence of heart failure grows by 70%, and after 30 years, the prevalence rises by 90% (J Diabetes Res 2018;2018:3407306).
Intraoperative ventilation, positioning, monitoring, and other issues can occur due to obesity. Even with advanced computer-driven anesthesia machines and newer ventilation modes, obese patients can be a challenge to ventilate and oxygenate. Dybec et al. showed that high BMI is an independent risk factor for pressure injury development as well (Plast Surg Nurs 2004;24:118-22). Noninvasive monitoring has its limitations, and blood pressure measurements in particular can be difficult to trust with the anatomic challenges and limitations of the blood pressure cuff in patients who are obese. One study by Schumann et al. showed that while trending capabilities between invasive and noninvasive methods were generally good, the absolute values were not interchangeable, and there was high interpatient variability (Anesthesiology 2021;134:179-88). An arterial line is sometimes necessary to obtain accurate blood pressure readings.
Postoperative care can have its challenges due to several factors, and the overall incidence of adverse events in the obese is higher than in patients with lower BMI. Atelectasis is common, and noninvasive positive pressure airway support devices may be helpful in the postoperative period. Nonanesthetic-related adverse events include increased risk of deep vein thrombosis, impaired immune system, and increased wound infection rates.
Finally, with the ever-increasing prevalence of obesity, anesthesia professionals should be keenly aware of the numerous implications this patient population spectrum literally brings to the table. Tailoring our anesthetics individually is a great academic and practical challenge, making our jobs that much more interesting. In the case above, the patient awakened within five minutes, crying, repeatedly thanking the staff for helping her. She had no memory of the procedure.