Reversing the Effects of a Peripheral Nerve Block with Normal Saline: A Randomised Controlled Trial

OBJECTIVE: The objective of the present study was to determine whether or not the effects of peripheral nerve block can be reversed by flushing normal saline down a peripheral nerve block catheter following the completion of arteriovenous (AV) fistula surgery. METHODS: In the present study, 38 patients undergoing AV fistula surgery were recruited, and a brachial plexus block with a peripheral nerve catheter was established. Following surgery, the patients were randomised to either the control group or the washout group, where 10 mL of normal saline was flushed down the peripheral nerve catheter at 15-minute intervals for 1 h while the patients were in the postoperative recovery room. An observer blinded to the patient group allocation assessed motor and sensory functions in all patients at 15-minute intervals for 1 h, and pain scores were recorded. RESULTS: There was no difference in time to resolution of motor or sensory block in the two groups. The median changes in the motor score were 1.5 out of 10 for the control group and 2 for the washout group (p=0.95). The median changes in the sensory score were 3 out of 10 for the control group and 1 for the washout group (p=0.14). There were no differences in pain scores over the study period in either group (p=0.44). CONCLUSION: We were unable to show any useful improvement in block resolution with normal saline washout of supraclavicular or infraclavicular brachial plexus blocks following AV fistula surgery.