Comparison of block characteristics of spinal anesthesia following intravenous dexmedetomidine and clonidine.

BACKGROUND AND AIMS: Different routes of administration of α2 adrenergic receptor agonists have been found to prolong the duration of spinal block.

MATERIAL AND

METHODS

One hundred and twenty patients, aged 18-60 years, of ASA physical status I or II posted for elective fixation of fractures of lower limb under spinal anesthesia were selected. Spinal anesthesia was administered with 2.5 ml of 0.5% bupivacaine mixed with 10 μg fentanyl. The patients were randomized to receive intravenous (IV) dexmedetomidine 1 μg/kg/h for 15 min followed by infusion of 0.3 μg/kg/h (Group I), IV Clonidine 2 μg/kg/h for 15 min followed by infusion of 0.5 μg kg/h (Group II) or 15 ml of normal saline for 15 min followed by infusion at 50 ml/h (Group III). Motor and sensory blockade was evaluated using bromage score and pin prick method respectively.

RESULTS

The median block height in all groups was T8. Time to achieve block height was fastest in Group I. Time of regression of sensory block to T12/L1 dermatome was 230.75 ± 21.25 min (Group I), 196.25 ± 20.27 min (Group II) and 163.88 ± 15.46 min (Group III) respectively. Regression of motor blocks to Bromage 0/1 was 274 ± 21.25 min, 234.25 ± 32.41 min and 130.12 ± 20.70 min in Groups I, II and III respectively. Bradycardia was seen in one patient in Group I and two patients in Group II. Hypotension was seen in five patients in Group I and seven patients in Group II. First requirement for postoperative analgesic was after 353.13 ± 39.60 min, 314.38 ± 30.64 min and 193.25 ± 17.74 min in Groups I, II and III respectively.

CONCLUSION

IV α2 agonists are useful adjuvants for prolongation of the duration of spinal block. IV dexmedetomidine produces a better clinical profile compared to clonidine.