[Prolongation of Bupivacaine spinal anaesthesia by oral and intramuscular Clonidine]. / Wplyw doustnej i domiesniowej premedykacji klonidyna na czas trwania analgezji podpajeczynówkowej.

ABSTRACT

The effect of oral and intramuscular clonidine premedication on the duration of sensory and motor blockade and postoperative analgesia during bupivacaine spinal anaesthesia was studied in 102 ASA physical status I-II patients scheduled for lower limbs orthopaedic surgery. In all cases one hour before anaesthesia midazolam (0.1-0.15 mg/kg) was applied orally and isotonic saline solution (10 ml/kg) was infused intravenously. The patients were randomly allocated into one of the following groups oral (A) or intramuscular (B) clonidine premedication (0.15 mg) (n = 33) and oral or intramuscular premedication by placebo (C) (n = 36). All patients received 10-20 mg of 0.5% hyperbaric bupivacaine intrathecally. Sensory blockade (SB) was evaluated by pinprick and motor blockade (MB) according to Bromage's scale. The following parameters were measured duration of motor and sensory block, requirement for postoperative analgesia (buprenorfine); systolic, diastolic and mean blood pressures; heart rate; oxyhemoglobin saturation (SpO2) and adverse events. As far as sex, body weight, age, height, ASA grade, dose of midazolam and bupivacaine, the onset of sensory and motor blockade, level of sensory analgesia, type of surgery and its average duration between groups were concerned, no differences were observed (p > 0.05). Both oral and intramuscular premedication with clonidine increased significantly the duration of motor (A--185.9 +/- 59.3; B--190.9 +/- 66.3 min) and sensory (A--216.2 +/- 69.4; B--254.2 +/- 76.8 min) blockade in comparison with placebo (MB--141.9 +/- 56.6; SB--156.7 +/- 62.9 min) (p < 0.01). The effect was more pronounced at the parenteral vs oral administration (p < 0.05). The intramuscular premedication with clonidine intensified the sedative effect of midazolam (p < 0.01). Hypotension, bradycardia and the decrease of SpO2 were significantly greater in B compared to C group (p < 0.05). Dose of buprenorfine applied in the first 24 postoperative hours was in both groups receiving clonidine (A--0.6 +/- 0.2; B--0.5 +/- 0.2 mg) nearly twice as small as than in a control group (1.1 +/- 0.2 mg) (p < 0.01). The authors conclude that prolongation of bupivacaine sensory analgesia may be produced by premedication with 0.15 mg of oral and intramuscular clonidine. The application of clonidine reduces the early postoperative analgesic requirements. The side effects are more pronounced with the intramuscular route of administration.