Evaluation of induction by use of a combination of oxymorphone and diazepam or hydromorphone and diazepam and maintenance of anesthesia by use of isoflurane in dogs with experimentally induced hypovolemia.

OBJECTIVE

To compare induction with hydromorphone and diazepam (HydroD) or oxymorphone and diazepam (OxyD) followed by maintenance with isoflurane in dogs with induced hypovolemia.

ANIMALS

6 healthy mixed-breed dogs.

PROCEDURE

The study used a crossover design. Measurements were obtained in normovolemic dogs during isoflurane. Hypovolemia was induced (blood loss of 30 mL/kg) and measurements repeated following recovery from anesthesia, after HydroD (hydromorphone, 0.1 mg/kg; diazepam, 0.2 mg/kg; i.v.) or OxyD (oxymorphone, 0.05 mg/kg; diazepam, 0.2 mg/kg; i.v.), after another dose of the same opioid, during administration of isoflurane (end-tidal concentration, 0.9%), and after glycopyrrolate (0.01 mg/kg, i.v.). Significant changes were identified.

RESULTS

Induction effect was evident within 1 minute. All dogs were intubated after the second dose of opioid. No significant differences were found between inductions. The HydroD decreased heart rate (mean +/- SEM, -41 +/- 9.8 beats/min), whereas both inductions increased stroke index (0.4 +/- 0.09 mL/kg/beat) and caused moderate respiratory depression. Cardiac index was decreased (-30.2 +/- 6.04 mL/kg/min) and there was minor metabolic acidosis during isoflurane following HydroD, compared with values for anesthetized normovolemic dogs. Glycopyrrolate increased heart rate (50 +/- 8.6 beats/min) and decreased systolic blood pressure (-23.2 +/- 4.87 mm Hg) in dogs induced with HydroD and decreased stroke index (-0.3 +/- 0.08 mL/kg/beat) for both inductions.

CONCLUSIONS AND CLINICAL RELEVANCE

Similar effects were detected after administration of HydroD or OxyD in hypovolemic dogs. Either combination should be safe for use in hypovolemic dogs. Administration of glycopyrrolate was not beneficial.