Anesthesia & Analgesia, Vol 87, 1336-1339, Copyright © 1998 by International Anesthesia Research Society
Oral clonidine premedication enhances the pressor response to ephedrine during spinal anesthesia
T Goyagi, M Tanaka and T Nishikawa
Department of Anesthesia and Critical Care Medicine, Tsuchiura Kyodo General Hospital, Ibaraki, Japan.
Clonidine premedication enhances the pressor effects of ephedrine in awake
and anesthetized patients. To test the hypothesis that clonidine augments
the pressor response to ephedrine during spinal anesthesia, 48 ASA physical
status I or II patients were randomly assigned to either the clonidine
group (n = 23), receiving oral clonidine approximately 5 microg/kg 90 min
before spinal anesthesia, or the control group (n = 25), receiving no
clonidine. Spinal anesthesia was performed at either the L2-3 or the L3-4
interspace using 0.5% hyperbaric tetracaine solution 1.4-3.0 mL. Blood
pressure (BP), heart rate, and the upper dermatomal level of analgesia were
determined at 1-min intervals with the patient in the supine position after
tetracaine injections. When systolic BP decreased to <80% of the
prespinal value or <100 mm Hg, IV ephedrine 0.2 mg/kg was administered
as a bolus. There were no differences in the duration until the first dose
of ephedrine after tetracaine injections, and the upper level of analgesia
between groups (control group 8.5+/-3.7 min, T5; clonidine group 7.7+/-2.7
min, T6). Although prespinal and preephedrine BP values were higher in the
control group, the magnitude of increases in mean BP after ephedrine was
significantly greater in the clonidine group (P < 0.05). We conclude
that oral clonidine premedication augments the pressor response to IV
ephedrine during spinal anesthesia. IMPLICATIONS: The pressor effect of
ephedrine is enhanced in patients given oral clonidine premedication during
spinal anesthesia.
