The cardiopulmonary effects of a peripheral alpha-2-adrenoceptor antagonist, MK-467, in dogs sedated with a combination of medetomidine and butorphanol

ObjectiveTo compare the cardiopulmonary effects of intravenous (IV) and intramuscular (IM) medetomidine and butorphanol with or without MK-467. Study designProspective, randomized experimental cross-over. AnimalsEight purpose-bred beagles (two females, six males), 3-4years old and weighing 14.51.6kg (meanSD). MethodsAll dogs received four different treatments as follows: medetomidine 20gkg(-1) and butorphanol tartrate 0.1mgkg(-1) IV and IM (MB), and MB combined with MK-467,500gkg(-1) (MBMK) IV and IM. Heart rate (HR), arterial blood pressures (SAP, MAP, DAP), central venous pressure (CVP), cardiac output, respiratory rate (f(R)), rectal temperature (RT) were measured and arterial blood samples were obtained for gas analysis at baseline and at 3, 10, 20, 30, 45 and 60minutes after drug administration. The cardiac index (CI), systemic vascular resistance index (SVRI) and oxygen delivery index (DO2I) were calculated. After the follow-up period atipamezole 50gkg(-1) IM was given to reverse sedation. ResultsHR, CI and DO2I were significantly higher with MBMK after both IV and IM administration. Similarly, SAP, MAP, DAP, CVP, SVRI and RT were significantly lower after MBMK than with MB. There were no differences in f(R) between treatments, but arterial partial pressure of oxygen decreased transiently after all treatments. Recoveries were uneventful following atipamezole administration after all treatments. Conclusions and clinical relevanceMK-467 attenuated the cardiovascular effects of a medetomidine-butorphanol combination after IV and IM administration.