Plasma bupivacaine concentrations and effects of epinephrine after superficial cervical plexus blockade in patients undergoing carotid endarterectomy

Objective: To determine if epinephrine (EPI) added to a solution of bupivacaine (BUP) injected for use in superficial cervical plexus blockade (SCPB) lowers plasma BUP concentrations after injection and whether this addition of EPI resulted in tachycardia, cardiac arrhythmias, or both. Design: Randomized, unblinded prospective clinical interventional study. Participants: Patients scheduled to undergo carotid endarterectomy using SCPB consenting to study. Setting: University-affiliated tertiary care hospital operating room. Interventions: Twenty patients were given SCPB with BUP 0.5% and were randomized to receive either no EPI or 1: 300,000 EPI. This study block was followed by a second period in which 20 patients were given SCPB with BUP 0.25% randomized to receive either no EPI or 1: 300,000 EPI. Continuous electrocardiogram monitoring was performed during and after the block and analyzed for heart rate and rhythm changes. Measurements and Main Results: Arterial plasma BUP concentrations were measured 2.5 to 120 minutes after initiation of SCPB. Plasma BUP concentrations were highest in the 0.5% no EPI group, followed by the 0.5% EPI, 0.25% no EPI, and 0.25% EPI groups. The use of EPI did not significantly affect heart rate or change the incidence of cardiac arrhythmias. Conclusions: BUP 0.25% consistently produced the lowest plasma BUP concentrations, particularly when EPI was added to the solution. BUP 0.5% without EPI can produce plasma BUP concentrations previously reported to be associated with central nervous system effects. The use of EPI in this setting does not produce untoward cardiac side effects.