Dexmedetomidine low dose followed by constant rate infusion and antagonism by atipamezole in isoflurane-anesthetized cats: an echocardiographic study.

OBJECTIVE: To investigate the effects of a low dose of dexmedetomidine (DEX) followed by constant rate infusion (CRI) and reversal with atipamezole on systolic and diastolic functions in isoflurane-anesthetized healthy cats.

STUDY DESIGN: Prospective cohort study.

ANIMALS: A group of 11 client-owned adult cats.

METHODS: Baseline transthoracic echocardiography (TTE) was performed, followed by intramuscular (IM) administration of DEX (5 μg kg-1 ). After 10 minutes, sedation was scored, adverse effects were recorded and another TTE performed. Approximately 40 minutes after DEX administration, anesthesia was induced by isoflurane mask and maintained with 1.2% end-tidal isoflurane and DEX CRI (1 μg kg-1  hour-1 ) for 80 minutes. Physiological variables were recorded every 10 minutes, and TTE was repeated 10, 30 and 60 minutes after the start of anesthesia. CRI was stopped, atipamezole (30 μg kg-1 ) was administered IM and a final TTE was performed after 10 minutes. Repeated measures over time were submitted to one-way analysis of variance or Kruskal-Wallis test according to data distribution; significance was assumed at p < 0.05.

RESULTS: After DEX premedication, mild sedation and a slight but significant increase in systolic arterial pressure occurred, and vomiting was a common adverse effect. The cardiac output (CO) and heart rate decreased during anesthesia, with no changes after administration of atipamezole. Trivial valvular insufficiencies were commonly seen after DEX premedication and during CRI. Myocardial radial and longitudinal systolic functions were not affected by sedation or by anesthesia. The late phase of diastole on both right and left ventricles was affected by isoflurane-DEX CRI. Global left ventricular myocardial performance was not impaired.

CONCLUSIONS: and clinical relevance Decreased CO and late diastolic impairment were observed in healthy cats administered a low dose of DEX for premedication followed by anesthesia with isoflurane and DEX CRI.