How Changing Lumbar Epidural Pressure Affects the Distribution of Local Anesthetics and the Level of Spinal Anesthesia

Abstract

Background: More than 20 factors including increased intra-abdominal pressure, as in term pregnancy or in patients with ascites, may alter spinal anesthetic block height unexpectedly. The object of this study was to observe the change of spinal anesthetic block height following the change of direct lumbar epidural pressure.Methods: Forty orthopedic patients (ASA physical status I or II) scheduled for spinal anesthesia with bupivacaine utilizing a combined spinal epidural set were divided into two groups randomly; Group C (control, n = 20) and Group S (saline, n = 20) Group S was injected with 10 ml saline to increase epidural pressure via an epidural needle after subarachnoid injection of bupivacaine. The change of epidural pressure was observed in the saline group and then the level of sensory block 5, 10, and 15 minutes after bupivacaine injection was measured in both groups. Statistical analysis was done using the Student's t-test.Results: There were significant changes in sensory block level between the two groups (P ＜ 0.05). The peak epidural pressure generated by epidural saline injection was 20-53 mmHg.Conclusions: Epidural pressure generated by epidural saline injection affects the sensory block level.