Induction and maintenance of general anesthesia were studied in six healthy sheep weighing 32.9 ±1.43 Kg (Mean ± SD). Each sheep anesthetized three times with 7 day intervals. Animals were premedicated with I.V administration of atropine (0.03 mg/kg), diazepam (0.5mg/kg), and morphine (0.2mg/kg). Anesthesia was induced with diazepam (0.2mg/kg) and lidocaine (4 or 6mg/kg). Lidocaine infusion (300-500 . µg /kg/min) was administered to maintain anesthesia. In addition, diazepam (8-12 µg/kg/min) was given by intermittent injection (group 1) approximately every 10 mintes, or infusion (group2) of lidocaine-diazepam mixture (8
out of 18 cases). The quality of anesthesia, swallowing, palpebral and comeal reflexes and pain sensation as well
as muscle relaxation were evaluatea during one hour anesthesia. Heart rate respiratory rate and mean arterial blood pressure (mmHg) were determined and ECG was recorded every 15 minutes. Hematological tests (CBC, PCV and methemogobin concentration) were performed before drug administration and at recovery. Quality of recovery (sternal & standing times) were recorded. Effect of I.V administration of na.loxone (0.04mg/kg) on recovery times was studied in 4 sheep. Following induction the swallowing reflex disappeared and intubation was performed easily. Analgesia was complete during anesthesia and quality of muscle relaxation was good. In group 2, heart rate and respiratory rate significantly decreased but mean arterial blood pressure changes were not significant. Electrocardiogram demonstrated increase in amplitude of QRS complex and T wave in all cases. Postanesthetic methemoglobin concentration increased significantly (4.9 ± 1.3% vs. 0.7 ± 0.18%). The quality of recovery was good. In group I and 2 mean standing times were 49.5 ± 4.27 and 43.25 ± 7.28 mm, respectively. In “naloxone treatment” group, mean standing time (19.5 ± 3.86 mm) significantly decreased compared to group I and 2. Our results demonstrate that lidocaine is a suitable drug for total intravenous anesthesia in healthy sheep. Excessive CNS depression can be reversed by naloxone.
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