Feyce Peralta, Nicole Higgins, Elizabeth Lange, Cynthia A. Wong, Robert J. McCarthy

Unintentional dural puncture is a known risk after epidural or combined spinal-epidural procedures, occurring in approximately 1% of labor epidural catheters placed in parturients with normal body habitus but may be as high as 4% in morbidly obese parturients. Anecdotal experience and limited publications suggest that an inverse relationship between body mass index (BMI) and postdural puncture headache (PDPH) may exist. We hypothesized that parturients with increased BMI have a lower incidence of PDPH than those with a lower BMI after unintentional dural puncture. After IRB approval, we performed a retrospective cohort study by medical record review. Case logs from our institution were searched for patients with documented unintentional dural puncture during attempted neuraxial analgesia between January 1, 2004, and December 13, 2013. The primary outcome was the incidence of PDPH. The association between BMI and PDPH was assessed using binary logistic regression, and the Wilcoxon-Mann-Whitney odds and confidence intervals (CIs) for a random pair of BMI values from a PDPH subject compared with a non-PDPH subject were calculated from the area under the receiver operator characteristics curve. Classification tree analysis was used to determine the BMI cutoff value for the risk of developing a PDPH. The presence or absence of second-stage labor pushing and placement of an intrathecal catheter after unintentional dural puncture were compared in parturients with and without PDPH using the Fisher exact test. BMI groups were dichotomized at the cutoff value (low and high BMI groups). We compared the incidence of a PDPH between high and low BMI groups using the Fisher exact test after controlling for pushing during labor and placement of an intrathecal catheter at the time of unintentional dural puncture. Secondary analysis evaluated the highest reported numeric rating of pain scores for headache and the need for an epidural blood patch between BMI groups. Unintentional dural puncture was identified in 518 (0.53%) patients (95% CI, 0.48%-0.58%). The overall incidence of PDPH after unintentional dural puncture was 51% (95% CI, 46%-55%). The Wilcoxon-Mann-Whitney odds for a random pair of BMI values from a PDPH subject compared with a non-PDPH subject was 0.74 (95% CI, 0.60-0.90, P = 0.001). The odds ratio for developing a PDPH in women who pushed during delivery was 2.4 (95% CI, 1.2-3.9, P = 0.001) compared with women who did not push. Classification tree analysis identified a BMI cutoff value of 31.5 kg/m for prediction of a PDPH. The incidence of PDPH in parturients with a BMI ≥31.5 kg/m (39%) was lower than in parturients with a BMI <31.5 kg/m (56%; difference -17%; 95% CI, -7% to -26%, P = 0.0004). The odds ratio for a PDPH in the high BMI compared with the low BMI group was 0.36 (95% CI, 0.14-0.92, P = 0.04) in parturients who pushed during labor and 0.62 (95% CI, 0.41-0.97, P = 0. 04) in parturients who did not push. After the unintentional dural puncture, 112 (22%) parturients had an intrathecal catheter placed. The incidence of PDPH in parturients with an intrathecal catheter was 59% (95% CI, 49%-68%) compared with 48% (95% CI, 43%-54%) in women with an epidural catheter (P = 0.06). Median (interquartile range) headache severity (0-10 verbal rating scale) was 8 (6-9) and did not differ between parturients in the high versus low BMI groups (P = 0.61). The rate of epidural blood patch administration for PDPH treatment was similar in BMI groups (difference -12%; 95% CI, 4 to -27, P = 0.13). The findings are consistent with previous reports of decreased PDPH incidence after unintentional dural puncture in parturients with an increased BMI, even after controlling for pushing during labor. Severity of headache and need for epidural blood patch treatment were similar in low and high BMI groups.