Does pregnancy increase the efficacy of lumbar epidural anesthesia?

Pregnancy has been reported to enhance the sensitivity of nerves to local anesthetics and to decrease anesthetic requirements during regional anesthesia. In this study, whether pregnancy increased the efficacy of lumbar epidural anesthesia was evaluated. Two populations (14 pregnant and 14 non-pregnant women) undergoing lumbar epidural anesthesia were studied and received 17 mL of 2% lidocaine-epinephrine (1:200,000). The pain threshold response after repeated electrical stimulation was used to assess sensory blockade at the L2, S I and S3 dermatomes. Motor blockade was evaluated using the Bromage score. Demographic data except for weight were comparable between the two groups. There was a significant difference in cephalad spread of anesthesia between the groups. No significant differences in pain threshold or onset of sensory blockade at the L2, S1 or S3 segments were found between the groups. The pain thresholds at the S1 and S3 dermatomes were significantly lower than that at L2 within each group. The mean onset times at the S1 and S3 dermatomes were significantly longer than that at L2 within each group. No differences in Bromage score were found between the groups. In pregnant women, cephalad spread of epidural anesthesia was facilitated but latency of blockade, density and motor blockade were not. It takes over 25 min to achieve satisfactory blockade at sacral segments. Those who perform lumbar epidural anesthesia alone for cesarean section should consider the use of additives (e.g. fentanyl, bicarbonate) to enhance the block, or a greater volume of local anesthetic. (C) 2004 Elsevier Ltd. All rights reserved.