Atipamezole Reverses Cardiovascular Changes Induced by High-Dose Medetomidine in Cats Undergoing Sedation for Semen Collection

SIMPLE SUMMARY: Medetomidine is a sedative agent widely used in veterinary medicine. It acts on alpha2 adrenoreceptors and thus also affects the cardiovascular system. Most frequently observed changes include a reduction in the heart rate and an increase in arterial blood pressure. In higher dosages, medetomidine can be used as sole agent for semen collection via urethral catheterisation in cats. Due to the marked haemodynamic effects, the potential risk of the repeated administration of high-dose medetomidine in breeding cats needs to be considered. Sedation with medetomidine can be reversed through its antagonist atipamezole. In this study, echocardiography was used to assess the cardiovascular changes after medetomidine administration. Different parameters were measured during sedation and after reversal with atipamezole. To further investigate the potential negative effects of repeated sedation on the heart muscle, the concentrations of a specific cardiac biomarker were determined. Medetomidine administration markedly altered cardiovascular function and led to a reduction in the heart rate and heart performance. However, reversal with atipamezole resulted in a normalization of haemodynamics. Repeated sedation did not lead to any adverse effects and no sustained damage of the heart muscle by means of elevated cardiac biomarker concentrations could be detected. ABSTRACT: This study aimed at describing the change in echocardiographic variables after high-dose medetomidine and the reversal with atipamezole in six cats undergoing sedation for semen collection. Further cardiac Troponin I (cTnI) concentration and the effect of repeated sedation were assessed. Echocardiography was performed before and 20 min after sedation with 0.1 mg/kg medetomidine intramuscularly (IM) for urethral catheterisation. Prior to epididymectomy, S-ketamine was administered intravenously. Twenty minutes after reversal with 0.5 mg/kg atipamezole IM, the third echocardiography was performed. Sedation with medetomidine and reversal with atipamezole was repeated on day 7, 14, 21 and 28. Heart rate (HR) and rhythm were monitored throughout all sedations. On day 0 and 28 cTnI concentrations were measured before and after the procedure. After normality testing, the values were compared over time. The administration of medetomidine led to a marked reduction in HR, cardiac output and ventricular systolic function and a significant increase in left ventricular dimensions. Rhythm abnormalities, such as ventricular premature complexes and idioventricular rhythm, could be observed. The administration of atipamezole completely reversed sedation and the changes in haemodynamic variables. No significant increase in cTnI concentrations could be detected, although two out of six cats showed values above the reference range.