Does systemic verapamil potentiate subarachnoid block?

Abstract

It has been experimentally shown that intrathecal administration of calcium channel blocker and local anaesthetic combination produces more potent sensory and motor blockade. However, the effects of systemically administered calcium channel blockers on subarachnoid block are unknown. Our aim in this study was to determine whether systemic administration of verapamil potentiates subarachnoid saddle block.. 20 ASA I-II adult patients, were randomly divided into two equal groups. Either verapamil of 5 mg or 1 ml. normal saline control were administered intravenously 30 minutes before the blockade, and then spinal saddle blockade was performed using 2 ml bupivacaine of 0.5 %. Sensory blockade was assessed with pin-prick test, and voluntary control of anal sphincter was used to assess motor blockade. The time from the intrathecal administration of bupivacaine to the beginning, completion and resolution of sensory and motor blockade were recorded. Arterial blood pressures and heart rates were monitorized. Student's-t, Chi- square and ANOVA tests were used for statistical evaluation. Both groups were comparable for demographic features. There were no statistically significant differences between the groups with regard to the times of blockade. Arterial blood pressure was lower in verapamil group when compared with the control group at 30th min (P<0.05). No potentialization of spinal anaesthesia in our study may be explained with the systemic dose of verapamil can not produce enough concentrations required for interaction with local anaesthetic in spinal cord. We concluded that the systemic administration of 5 mg verapamil does not potentiate spinal anaesthesia.