Related Experiment Videos
Comparison of clonidine and epinephrine in lidocaine for cervical plexus block
R R Molnar1, M J Davies, D A Scott
1Department of Anesthesia, St. Vincent's Hospital, Melbourne, Australia.
Background And Objectives:
Carotid endarterectomy under cervical plexus block offers the advantage of awake neurologic assessment. The hypothesis was tested that the addition of clonidine 5 micrograms/mL to lidocaine 1.5% for the block is as effective clinically as the addition of epinephrine 5 micrograms/mL but without the associated tachycardia.
Methods:
In a double-blind, randomized, prospective trial of 40 patients, local anesthetic solutions of lidocaine 1.5% containing either clonidine 5 micrograms/mL or epinephrine 5 micrograms/mL were compared for cervical plexus block in patients undergoing carotid endarterectomy. Each solution was administered to 20 patients with a total lidocaine dose of 7 mg/kg. The electrocardiogram, heart rate, and arterial pressure (radial artery catheter) were continuously monitored. Blood samples were drawn for determination of serum lidocaine levels during the first hour.
Results:
The block onset time (8.4 +/- 0.6 minutes for epinephrine, 8.8 +/- 0.8 minutes for clonidine) and duration (139 +/- 6.7 minutes for epinephrine, 148 +/- 5.8 minutes for clonidine) were not different between the two groups. During the period from completion of the block until incision there was a significant heart rate increase in the epinephrine group (23% mean rise) as compared with the clonidine group (4% mean rise) (P < .003). There was no difference in blood pressure between the two groups. The maximum plasma concentrations of lidocaine were 2.5-7.6 micrograms/mL (mean, 4.5 +/- 0.3 micrograms/mL) for the epinephrine group and 4.7-18.4 micrograms/mL (mean, 7.5 +/- 0.7 micrograms/mL) for the clonidine group (P < .0002). The maximum concentrations were reached 0-30 minutes (mean, 8 +/- 1.4 minutes) after injection for the epinephrine group and 0-10 minutes (mean, 4.5 +/- 7.1 minutes) for the clonidine group (P < .03).
Conclusions:
Clonidine 5 micrograms/mL is a useful additive to lidocaine 1.5% for cervical plexus block to reduce the incidence of tachycardia; however, omission of epinephrine results in higher serum lidocaine levels.