Comparison of co-administration of clonidine and pethidine with bupivacaine during spinal anesthesia

The aim of this study was to evaluate using the combination of pethidine and clonidine in order to produce synergistic effect for blocking of pain pathways in spinal cord and decrease the adverse effects of each drug and comparison it with bupivacaine. This is a randomized double blind controlled clinical trial which was approved by the ethics committee of Iran University of Medical Sciences. Fifty patients (25 patients in each groups) in ASA class 1 or 2 which were selected for surgery on lower limbs, entered into the study. The patients were randomly allocated in two groups and received following regimens: CP (spinal anesthesia with combination of clonidine 0.75 µgr/kg and pethidine 0.75 mg/kg) and B (spinal anesthesia with bupivacaine 0.5%, 15 mg). The onset time of sensory block on T10 in group CP (5.9±1.6 min) was significantly less than group B (9.2±2.3 min) [p<0.001]. The time to complete motor block in group CP (38.8±5.7 min) was significantly longer than group B (19.6±4.7 min) [p<0.001]. The time to the first analgesic request was significantly longer in the group CP (11.6±2 h) than the group B (6±0.8 h) [p<0.001]. Mean drop in the systolic blood pressure in group CP (22.6%±2.4%) was significantly more than group B (11%±4.3%) (p<0.001). It is recommended to use bupivacaine for anesthesia in operations on pelvis and lower limbs but it is better to co-administer clonidine and pethidine in patients who must be avoided from raising blood pressure and heart rate and with less than two hours operation time.