Dural Puncture Epidural Technique: Not So Fast
The primary outcome (onset of analgesia) was defined as time until verbal numeric pain score ≤1. Many parturients appear to not have achieved the primary outcome, as defined, within the first 2 hours, presumably necessitating use of survival curve presentation and the Cox proportional hazard statistic for comparisons. It may have been preferable to avoid the numerical surrogate and define “onset” in the parturient’s terms—no request for top-up early after block initiation.
Of over 80 secondary outcomes evaluated, differences favoring DPE over EPL included block asymmetry, sacral sensory block, and physician top-ups. Although incidence of block asymmetry (defined as sided differences greater than 2 dermatomes) is reported, magnitude of asymmetry is not, and so clinical significance is difficult to assess. That no catheters (single orifice, inserted 5 cm in nonobese parturients) were replaced and only 7.5% were adjusted suggests limited clinical significance. In contrast to their prior report,2 the initial epidural volume was very large (20 mL), producing high thoracic sensory blocks in each group (median sensory levels of T4 at 30 minutes, range T2 to midthoracic). Differences in early sacral block onset were reported, but this is unnecessary in early labor, and it appears that only 2 patients did not achieve S2 block at a later point. Their results suggest that CSE is the technique of choice when rapid sacral block is needed.
Physician top-ups, defined in binary terms (yes or no), were reported as more common in the EPL group. The number of top-ups was not reported or compared, limiting appraisal of clinical significance. It is possible that differences between groups in duration and intensity of labor pain, and ultimately cesarean delivery rates, are confounders responsible for observed top-up intervention differences. We think that the women in the EPL group may have had more painful and longer labors, suggested by that group’s higher cesarean delivery rate. Unlike in their prior study,2 cesarean rates were vastly different among groups, likely a chance result of randomization. The overall cesarean rate among these 120 low-risk women in early labor was not unexpectedly 14%. However, the EPL group experienced a much higher cesarean rate (27%), 5.5-fold higher than in the CSE group (5%), and nearly 3-fold higher than in the DPE group (10%). Given these differences, comparisons between top-up rates must be adjusted for mode of delivery. Additionally, duration of epidural infusion was not reported, unlike previously.2 Top-up rates should also be adjusted for duration of infusion, as they did for motor block comparisons.1 These analysis issues, along with the acknowledged exclusion of a correction for multiple comparisons, limit conclusions regarding differences in secondary outcomes between groups.
While it is tempting to embrace potential advantages of DPE, especially given appealing explanatory theory, we think that routine adoption of this technique remains premature and in need of further corroborating evidence.