Ultrasound dilution cardiac output and echocardiography findings in anesthetized mature alpacas (Vicugna pacos) during normotension, hypotension and hypertension

Alpacas (Vicugna pacos) have physiologic adaptations to live at high altitude. These adaptations may result in unexpected responses to changes in cardiac performance and blood pressure during general anesthesia. There are few studies evaluating cardiovascular variables in anesthetized alpacas. The purpose of this study was to report cardiovascular performance in anesthetized mature alpacas during normotension, hypotension, and hypertension using ultrasound dilution and echocardiography. Six adult alpacas, 3 females and 3 castrated males, weighing 62.6 to 88.7 kg were anesthetized and maintained with isoflurane and placed in right lateral recumbency. Each alpaca underwent ultrasound dilution and echocardiography measurements during three cardiovascular phases, normotension, hypotension via increased isoflurane concentration, and hypertension via phenylephrine infusion. Variables were analyzed with a Friedman test and a post hoc Dunn’s test when significant. A p < 0.05 was used for significance. Cardiac output, cardiac index, systemic vascular resistance, stroke volume, total ejection fraction, left ventricular internal diameter during diastole, and total stroke volume indexed to body weight were greater for hypertension compared to hypotension. Total ejection fraction, stroke volume, and left ventricular ejection time were greater for hypertions compared to normotension. There was no difference between ultrasound dilution and echocardiography determined cardiac output measurements within each cardiovascular phase. Phenylephrine appeared to have increased ventricular performance and/or increased preload in anesthetized, mature alpacas. For detecting change in cardiovascular status in anesthetized alpacas, ultrasound dilution and echocardiography may be useful.