Epidural volume expansion: is there a ceiling effect?

Abstract

Aim: The optimal volume of epidural saline administration on spinal anesthesia is not clear. The aim of this study was therefore to evaluate the block characteristics of 5, 10, 15, and 20 mL epidural saline after spinal anesthesia.

Methods: This prospective, randomized double-blind study was conducted in the operation room setting of a university hospital. Seventy-five healthy adult patients electively undergoing limb surgery under regional anesthesia were investigated. Spinal anesthesia was performed, and plain bupivacaine (10 mg) was administered within one minute using combined spinal and epidural anesthesia. Epidural catheters were introduced, and patients were allocated to one of five groups to receive 0, 5, 10, 15 or 20 mL saline through the catheter (N=15 in each group). The patient was assessed every minute for motor and sensory block levels until a maximum level was reached. In addition, the patient was assessed thereafter in five-minute intervals using Bromage's scale for motor block and pinprick/cold sensation for sensory block.

Results: The maximum level of spinal analgesia was significantly lower in the control group compared to the saline treatment groups, but there was no significant difference between the epidural saline groups. The periods for motor block resolution were the same. The duration of analgesia was significantly longer in patients receiving 15 mL saline compared to other groups. The time to regression to the L1 level was significantly longer with 15- and 20-mL treatment groups compared to the 5- and 10-mL groups.

Conclusion: The present results indicate that a ceiling effect was observed on the duration of spinal analgesia using plain bupivacaine with epidural saline loading (maximum--15 mL).