How ketamine changes heart and lung effects of dog sedation drugs

Abstract

OBJECTIVE: To compare the cardiorespiratory effects of IM administration of dexmedetomidine-buprenorphine (DB) and dexmedetomidine-buprenorphine-ketamine (DBK) in dogs with subsequent reversal with atipamezole. DESIGN: Prospective, randomized crossover study. ANIMALS: 5 healthy dogs. PROCEDURES: Dogs were instrumented for cardiac output (CO) measurement and received DB (15 &#x3bc;g of dexmedetomidine/kg [6.8 &#x3bc;g/lb] and 40 &#x3bc;g of buprenorphine/kg [18.2 &#x3bc;g/lb]) or DBK (DB plus 3 mg of ketamine/kg [1.36 mg/lb]) in randomized order while breathing room air. Atipamezole (150 &#x3bc;g/kg [68.2 &#x3bc;g/lb], IM) was administered 1 hour later. Hemodynamic data were collected in the conscious dogs and then at 5, 10, 15, 20, 30, 45, and 60 minutes after drug administration. Lactate concentration was measured in mixed venous blood samples. Oxygen delivery (Do(2)) and oxygen consumption ([Formula: see text]o(2)) were calculated. RESULTS: Heart rate (HR), CO, and Do(2) decreased after DB and DBK administration. The [Formula: see text]o(2) did not change in the DB group but decreased in the DBK group. The HR was higher in the DBK group than in the DB group throughout the study, but the CO, Do(2), and [Formula: see text]o(2) values were similar for the 2 groups. Blood lactate concentrations remained low (< 1 mmol/L) throughout the study. Arterial hypoxemia and hypercapnea occurred in both groups. Mean arterial blood pressure and pulmonary artery wedge pressure were markedly increased in both groups, but to a greater extent in the DBK group. After atipamezole administration, HR, CO, and Do(2) returned to the baseline values. CONCLUSIONS AND CLINICAL RELEVANCE: Adding ketamine to the DB combination allowed dogs to maintain a higher HR and delayed the onset of sinus arrhythmias but failed to provide a significantly higher CO because of a reduction in stroke volume.