Echocardiographic and hemodynamic effects of alfaxalone or dexmedetomidine based sedation protocols in cats with hypertrophic cardiomyopathy: a pilot study

Objective: To report the effects of alfaxalone and dexmedetomidine based sedation protocols on echocardiographic and hemodynamic variables in cats with hypertrophic cardiomyopathy (HCM) during sedation and inhalational anesthesia. Study design: Prospective, randomized, experimental study. Animals: A group of 10 client-owned cats with subclinical HCM. Methods: Cats were administered one of two sedative intramuscular combinations: protocol ABM (alfaxalone 2 mg kg^–1, butorphanol 0.4 mg kg^–1, midazolam 0.2 mg kg^–1; n = 5) or protocol DBM (dexmedetomidine 8 μg kg^–1, butorphanol 0.4 mg kg^–1, midazolam 0.2 mg kg^–1; n = 5). General anesthesia was induced with intravenous alfaxalone and maintained with isoflurane in oxygen. Echocardiographic variables and noninvasive arterial blood pressures were obtained before sedation, following sedation, and during inhalational anesthesia. Sedation scores and alfaxalone induction dose requirements were recorded. Descriptive statistics are reported for cardiovascular variables. Results: During sedation, echocardiographic and hemodynamic variables remained within normal limits with protocol ABM, whereas protocol DBM was characterized by bradycardia, low cardiac index and elevated blood pressure. During isoflurane anesthesia, both protocols demonstrated similar hemodynamic performance, with heart rates of 98 ± 12 and 89 ± 11 beats min^–1, cardiac index values of 68 ± 17 and 47 ± 13 mL min^–1 kg^–1 and Doppler blood pressures of 72 ± 15 and 79 ± 20 mmHg with protocols ABM and DBM, respectively. A reduction in myocardial velocities were also observed during atrial and ventricular contraction with both protocols during isoflurane anesthesia. Conclusions and clinical relevance: An alfaxalone based protocol offered hemodynamic stability during sedation in cats with HCM; however, both dexmedetomidine and alfaxalone based protocols resulted in clinically relevant hemodynamic compromise during isoflurane anesthesia. Further studies are required to determine optimal sedative and anesthetic protocols in cats with HCM.