Effects of Concurrent Administration of Bupivacaine on The Hypnosis of Thiopentone in Dogs
Abstract
This study evaluated the effect of bupivacaine pretreatment on certain indices of thiopentone hypnosis in unmedicated dogs. Five healthy, unmedicated dogs underwent two series of trials one week apart. In the first series of trials, each dog received intramuscular injection of 0.5mg/kg 0.5% bupivacaine , induced, 20 min later, with the intravenous injection of 25mg/kg 2% thiopentone and then endotracheally intubated. The procedure was repeated for the second series, replacing bupivacaine with 2ml normal saline solution as control. In all trials, analgesia was assessed at 2min intervals using pedal withdrawal response to haemostatic forceps closed to the first ratchet. Calculated indices were compared with control values using student’s ‘T’ test for paired data. Differences were considered significant at p<0.05. Time to intubation (11.2±2.0 min), onset of analgesia (11.1+1.9),duration of analgesia (19.4+7.2) and duration of hypnosis (50.0±5.2 min) in the experimental groups were significantly longer than the corresponding control values of 3.8±0.8 min, 3.4±0.7min, 8.4±1.5 min and 44.6±10.0 min. Duration of intubation (41.0+5.1), time to sternal posture (44.4±16.5 min) and time to standing (21.6±20.1 min) were not significantly different from corresponding control values of 8.7+7.8 min,18.2± 4.7 min and 13.4±4.5 min. It was thus concluded that the concurrent administration of bupivacaine with thiopentone resulted in prolonged hypnosis of 50.0 + 5.2 min duration.
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