The increased prevalence of morbid obesity presents numerous analgesic challenges, including respiratory- and cardiovascular-related issues. According to a recent Wake Forest study, higher body mass index (BMI) also is associated with the reliability of epidural catheters during labor.
The retrospective analysis of labor neuraxial procedures found that catheter failure for both epidural and combined spinal–epidural techniques was related to parturient BMI.
At the 2016 World Congress of Anaesthesiologists, lead author of the study, Joshua Pan, MD, said these findings support greater vigilance of catheter function during labor analgesia and noted that use of combined spinal– epidural techniques would reduce catheter failure risk, especially in morbidly obese patients (abstract PR213).
“Morbid obesity, especially with BMI greater than 35 kg/m2, was associated with increased risk of labor epidural catheter failure regardless of combined spinal–epidural or epidural [techniques],” said Dr. Pan, an anesthesiologist at Wake Forest School of Medicine, in Winston-Salem, N.C. “However, compared to epidural, combined spinal–epidural [techniques] reduced the risk of catheter failure for labor and cesarean delivery at all BMI levels [Table].
“BMI did not increase failed conversion of catheter for cesarean delivery if the catheters were functional for labor analgesia,” Dr. Pan added.
As Dr. Pan reported, epidural and combined spinal–epidural techniques have become the mainstay of labor analgesia, but the incidence of epidural catheter failure is still 5% to 10%. An increase in prevalence of morbid obesity, however, has led to greater frequency of cesarean delivery, placing added importance on the reliability of epidural catheters for patient safety.
In an interview with Anesthesiology News, Dr. Pan observed that the ratio of combined spinal–epidural to epidural techniques at his own institution has risen in recent years from “approximately 50:50” to “closer to 65:35 in favor of combined spinal–epidural [techniques],” but cautioned that use of epidural anesthesia may be significantly higher at other institutions.
Although clinicians have expressed concern that combined spinal–epidural techniques may be more likely to lead to catheter failure or delayed recognition of failure compared with straight epidural anesthesia, a recent study by Booth et al (Anesthesiology 2016;125:516-524) demonstrated a lower incidence of failure with combined spinal–epidural techniques. As a result, Dr. Pan said this technique can now be chosen with less concern.
However, he added, combined spinal–epidural techniques may be associated with increased fetal bradycardia shortly after the procedure, and should thus be avoided in patients with poor fetal heart rate tracing.
Increasing BMI, Increasing Catheter Failure
Dr. Pan and his colleagues retrospectively analyzed anesthetic, obstetric and quality assurance records from 2,362 labor neuraxial procedures performed at Forsyth Medical Center during a six-month period. The BMIs of parturient women ranged from 16 to 69 kg/m2.
After controlling for covariates, the multivariable regression model showed that increases in BMI significantly raised the risk for catheter failure (hazard ratio [HR], 1.02; 95% CI, 1.004-1.04; P=0.02). According to the data, for every 1-kg/m2increase in BMI, there was a 2% increase in risk for catheter failure.
Compared with epidural, combined spinal–epidural techniques reduced the risk for catheter failures at all BMI levels (HR, 0.61; 95% CI, 0.44-0.83; P=0.002).
Regardless of technique used, BMI greater than 35 kg/m2 was significantly associated with increased rates of cesarean delivery and the number of supplemental epidural top-ups needed. However, when only cesarean deliveries were considered, BMI did not affect success of catheter conversion.
“Catheter failure might have been recognized and sorted out earlier during labor course … before the need of cesarean delivery arrived,” Dr. Pan speculated, “or the sample size of those needing cesarean delivery may be underpowered to show the statistical significance in the difference in failure associated with BMI.”