Cardiovascular effects of epidurally administered oxymorphone and an oxymorphone-bupivacaine combination in halothane-anesthetized dogs

Objective-To evaluate cardiovascular effects of epidurally administered oxy morphone (OXY) and an OXY-bupivacaine combination (O/B) in halothane-anesth etized dogs. Animals-6 dogs. Procedure-In a randomized crossover design study, dogs were anesthetized wi th halothane and given OXY, O/B, and saline solution (SAL). Eucapnia and en d-tidal halothane concentration of 1.2% were established. Heart rate (HR), systemic and pulmonary arterial pressures, central venous pressure (CVP), a nd cardiac output were measured at baseline and 5, 15, 30, 45, 60, and 75 m inutes after treatment. At 90 minutes, glycopyrrolate was administered IV, and measurements were repeated at 95 minutes. Cardiac index (CI), stroke vo lume, stroke index, systemic vascular resistance (SVR), and left ventricula r work were calculated. End-tidal halothane concentration was decreased to 0.8% from 17 to 45 minutes and to 0.5% from 47 to 95 minutes for OXY and O/ B, whereas for SAL, it was maintained at 1.5 and 1.2%, respectively. Sample s were obtained at 0, 2, 5, 15, 30, 45, 60, and 95 minutes for measurement of serum opiate concentration and comparison with values after IM administr ation of OXY. Results-HR decreased, but CVP and SVR increased in response to OXY and O/B. These changes were reversed after IV administration of glycopyrrolate, res ulting in significant increase in CI, compared with that in response to SAL . Serum opiate concentration increased markedly and peaked within 15 minute s after OXY and O/B administration but did not differ from values after IM administration. Conclusions-Epidural administration of OXY results in rapid systemic uptake and decreased HR. Glycopyrrolate administration improves HR, resulting in improved CI at equipotent halothane concentrations.