Spinal anesthesia with clonidine and bupivacaine in young humans: interactions and effects on the cardiovascular system.

BACKGROUND: Clonidine, an alpha 2 agonist, is known to prolong the action of local anesthetics, and to provide a satisfactory analgesia; hypotension and bradycardia have been observed after its intrathecal administration. The aim of our study was to determine whether intrathecal administration of clonidine can reduce the dose of local anesthetic, and the effects of clonidine on the cardiovascular system, and on arousal level.

METHODS: In a prospective, randomized study we evaluated 56 patients scheduled for minor surgical procedure (spermatic vein ligature) under unilateral spinal anesthesia with hyperbaric bupivacaine 1%. One half of patients received clonidine (105 micrograms) in addition to bupivacaine. Mean arterial pressure, heart rate were recorded baseline until 1 hour after surgery. Cardiac output, stroke volume, ejection fraction, systemic vascular resistance and left cardiac work were measured, by thoracic electric bioimpedance method, baseline until 1 hour after surgery. Sensory block, motor block and sedation level were measured at the beginning of anesthesia and for 6 hours after the end of surgery.

RESULTS: In the clonidine treated group we did not observe variations of cardiovascular parameters; in the same group we did observe sensory block and motor block significantly prolonged, a higher sedation level and a significant postoperative analgesia.

CONCLUSIONS: In summary, the addition of clonidine to hyperbaric bupivacaine seems to be particularly useful in unilateral spinal anesthesia, exerting minimal influence on haemodynamic parameters, and guaranting a satisfactory postoperative analgesia.