The effect of lumbar epidural anesthesia on maternal middle cerebral artery blood flow in normal pregnancy: A prospective, randomized, double- blind comparison study

OBJECTIVE: Lumbar epidural anesthesia is associated with a transient elevation in intracranial pressure in both animals and humans and decreased cerebral blood flow in animals. We sought to determine the effect of medium- onset and slow-onset local anesthetic lumbar epidural anesthesia on maternal cerebral blood flow in normal human pregnancy. STUDY DESIGN: In an Institutional Review Board-approved, double-blind study, 24 healthy, normotensive, nonlaboring, term gravida women undergoing elective cesarean section were prospectively placed into random groups to receive either 2% lidocaine with 8.4% sodium bicarbonate (1:10) or 0.5% bupivacaine lumbar epidural anesthesia. After prehydration with 20 mL/kg crystalloid and 15- degree left-wedged supine positioning with 15-degree head tilt, transcranial Doppler ultrasound (Nicolet Pioneer EME) and simultaneous electrocardiogram, automatic blood pressure (Dinamap), and end-tidal CO₂ (SAR-Trans) monitoring were performed. Pulse, blood pressure, respiratory rate, end-tidal CO₂, middle cerebral artery blood flow velocity, and pulsatility index were measured at (1) baseline (once supine positioning was assumed); (2) immediately after administration of 20 mL local anesthetic; and (3) every 5 minutes for 25 minutes. Timing of the attainment of a T4 dermatome anesthetic level was noted. Comparisons were made by t test, rank sum tests, χ², and repeated measures analysis of variance. P < .05 was considered significant. RESULTS: Maternal heart rate, blood pressure, respiratory rate, and end- tidal CO₂ were not significantly different within or between groups. No significant difference was found in baseline middle cerebral artery blood flow velocity or pulsatility index values between groups. Neither middle cerebral artery blood flow velocity nor pulsatility index changed significantly within or between groups up to 25 minutes after institution of epidural anesthesia. CONCLUSIONS: Maternal middle cerebral artery blood flow velocity, as measured by transcranial Doppler ultrasonography, is maintained in normotensive, nonlaboring term gravida women receiving either lidocaine or bupivacaine lumbar epidural anesthesia, which supports intact cerebrovascular autoregulation in normal pregnancy.