Abstract
The effects of midazolam (0.3 mg/kg IV) alone or with the addition of butorphanol (0.0125, 0.025, 0.05, and 0.1 mg/kg IV, groups A, B, C, D, and E, n = 40 each) as combinations for premedication before inhalation anes-thesia were evaluated in 200 dogs [ASA Classes I (n= 89), II (n= 86), and III (n = 25)]. Surgical anesthesia was induced by ketamine (5mg/kg IV) and maintained with 50% nitrous oxide-50% oxygen -sevoflurane. All dogs of ASA Class III grew calm and relaxed and assumed a sternal position after premedication. Dogs of Class-es I and II demonstrated mild to moderate sedation and dose-dependent sedative effects caused by butor-phanol. In several dogs of ASA Class I in each group, intratracheal intubation was impossible after ketamme injection. In these cases, mask-induced oxygen-sevoflurane anesthesia was followed by intubation. Heart and respiratory rates decreased minimally after premedication; and, in groups D and E, respiratory rate decreased significantly after induction to anesthesia. End-tidal sevoflurane concentrations during surgery varied from 2.4-2.6% in group A, 2.0-2.1% in group B, 2.3-2.4% in group C, 2.0-2.2% in group D, and 2.1-2.2% in groupE. In all instances, during surgery, heart rate (130 bpm), mean arterial blood pressure (90-110 mmHg), res-piratory rate (30 bpm), and partial pressure of end-tidal CO2 (40 50 mmHg) remained with normal canine lim-its. Recovery from anesthesia was rapid, and most dogs were extubated by 10 minutes after anesthesia cessa-tion. The combination of midazolam and butorphanol is useful premedication for dogs of ASA Classes II and III
