Effects of Increasing Body Mass Index on Epidural Placement Difficulty and Failure: A Retrospective Chart Review of Prospectively Collected Quality Assurance Data
Abstract Number: 113
Abstract Type: Original Research
The global obesity epidemic brings unique difficulties to the anesthesiologist on labor and delivery.1 While earlier studies defined some factors associated with difficulty or failure of neuraxial anesthesia,2 few have focused on the obese parturient, or precisely defined "difficulty" and "failure."3,4 Yet these patients may benefit most from regional anesthetic management. We hypothesized that increasing body mass index (BMI) would be associated with increased neuraxial anesthetic failure and difficulty.
After IRB approval, we retrospectively reviewed prospectively collected quality assurance (QA) data and anesthesia records for parturients receiving epidural analgesia between January and July of 2008. Data collected included age, height, weight, BMI, co-morbidities, anesthetic technique, and training level of the anesthesiologist. Epidural failure was defined as inadequate analgesia after adequate dosing, or positive test dose. Specifically, epidurals were considered inadequate if: the catheter needed to be replaced, the chart or QA form stated that the catheter failed but was not replaced, or a change of technique was needed (usually for cesarean section). Epidural difficulty was defined as either more than 6 redirections of the epidural needle, or a note of difficulty in the anesthesia record or QA form. Wet taps were recorded as a separate complication.
Data from 1565 patients receiving epidural anesthesia for labor, cesarean section (CS), or both, were analyzed. Median BMI was 31 kg/m2, range 18 - 72. Overall epidural failure and difficulty rates for all patients were 3.8% and 2.8% respectively. Patients were divided into two groups above and below our median BMI=31. Using Chi-square analysis, the higher BMI group had a significantly higher chance of both failure (p=0.003) and difficulty (p=0.046). The higher BMI group was also associated with factors known to be prevalent in obese parturients: HTN, asthma, obstructive sleep apnea, GERD, DM, and risk of CS (all p<0.05). Multiple logistic regression, using BMI as a continuous variable, indicated that failure was best predicted by BMI (p=0.002) and younger age (p=0.038); while difficulty was best predicted by BMI (p<0.001). The overall wet tap rate in our population was 0.3%, was not counted as a "failure," and did not differ between BMI groups (p=0.618). In multiple logistic regression, wet tap was best predicted by PIH (p=0.020).
Higher BMI is associated with both increasing technical difficulty and failure of epidural anesthesia. Practitioners should consider allotting extra time for obese parturients in order to solve potential problems.
1.Saravanakumar K, et al. Anaesthesia 2006;61:36-48.
2.Ellinas EH, et al. Anes & Analg, 2009;109:1225-31.
3.Pan et al. Int J Obstet Anes 2004;13:227-33.
4.Bamgbade OA, et al. Int J Obstet Anes 2009;18:221-5.