Effects of Oral Clonidine Premedication on the Spinal Anesthesia

Han, Kyung Ream; Han, Jong In; Kim, Chi Hyo; Lee, Choon Hi

Abstract

Oral clonidine premedication appears to inhibit the outflow of sympathoadrenal activity and adrenocortical hormone release, thereby decreasing the minimum alveolar anesthetic concentration of inhaled anesthetics and stabiliring cardiovascular system. It has been reported that oral clonidine premediacation for spinal anesthesia, similar to intrathecal administration of clonidine, has prolonging effect of sensory and motor blocks. The purposes of this study are to assess the effects of oral clonidine premedication on the duration of tetracaine spinal anesthesia, and the hemodynamic changes during spinal anesthesia. Twenty patients undergoing hemorrhoidectomy, TURP, and device removal of lower extremity under spinal anesthesia (0.5% hyperbaric tetracaine), were given diazepam 10 mg orally (Group 1, n=10) or clonidine 150 ug orally (Group 2, n=10) 1 hour before tbe anestbesia. The results were the following, (1) No significant differences was noted between two groups in either the maximum level of sensory extension or time to maximum level of sensory blockade between two groups. In Group 2, the time for two-segment regression was prolonged compared with group 1, but not significant. The time for regression to L1 was significantly prolonged in Group 2 (238+/-37.74min) compared with Group 1 (167.6+/-25.85min)(P<0.05). (2) The number of patient in Bromage's scale score 3 of motor blockade between 180min and 260min after spinal anesthesia was 10 times higher in Group 2 compaired with Group 1 (P<0.05). (3) In Group 1, the lowest systolic blood pressure during spinal anesthesia was significantly low compared with that before premedication (P<0.05). In Group 2, systolic blood pressure before spinal anesthesia, mean systolic blood pressure during first 20mins of spinal anesthesia and the lowest systolic blood pressure were significantly reduced respectively comparing with those before premedication. Significant difference (P<0.05) was noted between Group 1 and 2 in mean systolic blood pressure during the first 20 mins of spinal ansthesia and in lowest systolic blood pressure during spinal anesthesia. In both groups, the lowest heart rate was significantly lower after than before premedication (P<0.01), but the difference in the amount of heart rate change between two groups was not significant. In conclusion, prolongation of sensory and motor blocks of spinal anesthesia with hyperbaric 0.5% tetracaine may be accomplished with oral premedication of 150 ug clonidine without serious clinieal complication.