Efeitos da associação da clonidina à bupivacaína hiperbárica na anestesia subaracnóidea alta

Abstract

BACKGROUND AND OBJECTIVES: Published data suggest that clonidine, an α2-adrenergic agonist, in association with bupivacaine, may increase the incidence of intraoperative hypotension and bradycardia during high-level spinal anesthesia. This study aimed at determining the synergistic potential of two clonidine doses (45 and 75 μg) and hyperbaric bupivacaine on. characteristics and hemodynamic effects of high-level (T4) spinal anesthesia. METHODS: Participated in this randomized double-blind study, 60 ASA I patients scheduled for lower abdominal and limb surgery. Spinal anesthesia was induced with 17.5 mg (3.5 ml) of 0.5% hyperbaric bupivacaine plus the association of the following drugs: Control group (n = 20) - 0.5 ml isotonic saline solution; Clon 45 group (n = 20) - 45 μg (0.3 ml) clonidine + 0.2 ml isotonic saline solution; and Clon 75 (n = 20) - 75 μg (0.5 ml) clonidine. Surgery was only started when high-level (T4) analgesia was consistently obtained, RESULTS: Sensory and motor block onset did not significantly differ among groups (p > 0.05). Both clonidine doses significantly prolonged analgesic block at T8 and motor block level 3 duration (determined by modified Bromage scale) (p < 0.05). Intraoperative arterial hypotension was observed only in Clon 75 group as compared to Control group (p < 0.05), while Clon 45 group had intermediate incidence between both groups. There was no significant difference among groups in bradycardia (p > 0.05). Both clonidine doses prolonged postoperative analgesia (time from spinal block to first postoperative analgesic request) (p < 0.05). CONCLUSIONS: High clonidine dose (75 μg) associated to hyperbaric bupivacaine during high-level spinal anesthesia (T4) induces a higher incidence of arterial hypotension but prolongs sensory block and postoperative analgesia similar to lower clonidine dose (45 pg) during upper spinal anesthesia.