• Saad S Enouri, Carolyn L Kerr, Wayne N McDonell, and Doris H Dyson.
• Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1H 2W1, Canada.
• Am. J. Vet. Res. 2008 May 1;69(5):586-95.

ObjectiveTo evaluate the cardiopulmonary effects of anesthetic induction with thiopental, propofol, or ketamine hydrochloride and diazepam in dogs sedated with medetomidine and hydromorphone.Animals6 healthy adult dogs.ProceduresDogs received 3 induction regimens in a randomized crossover study. Twenty minutes after sedation with medetomidine (10 microg/kg, IV) and hydromorphone (0.05 mg/kg, IV), anesthesia was induced with ketamine-diazepam, propofol, or thiopental and then maintained with isoflurane in oxygen. Measurements were obtained prior to sedation (baseline), 10 minutes after administration of preanesthetic medications, after induction before receiving oxygen, and after the start of isoflurane-oxygen administration.ResultsDoses required for induction were 1.25 mg of ketamine/kg with 0.0625 mg of diazepam/kg, 1 mg of propofol/kg, and 2.5 mg of thiopental/kg. After administration of preanesthetic medications, heart rate (HR), cardiac index, and PaO(2) values were significantly lower and mean arterial blood pressure, central venous pressure, and PaCO(2) values were significantly higher than baseline values for all regimens. After induction of anesthesia, compared with postsedation values, HR was greater for ketamine-diazepam and thiopental regimens, whereas PaCO(2) tension was greater and stroke index values were lower for all regimens. After induction, PaO(2) values were significantly lower and HR and cardiac index values significantly higher for the ketamine-diazepam regimen, compared with values for the propofol and thiopental regimens.Conclusions And Clinical RelevanceMedetomidine and hydromorphone caused dramatic hemodynamic alterations, and at the doses used, the 3 induction regimens did not induce important additional cardiovascular alterations. However, administration of supplemental oxygen is recommended.

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