Cardiovascular effects of alfaxalone on hemodynamic function in pigs

Nadine Pfeiffer,¹ Johanna Ebner,¹ Anne-Kathrin von Thaden,¹ Tibor Schuster,² Wolf Erhardt,³ Christine Baumgartner<sup>1

1</sup>Center of Preclinical Research, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany; ²Institute for Medical Statistics and Epidemiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany; ³Institute for Experimental Oncology and Therapeutic Research, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany

Background: The purpose of this study was to investigate the short-term cardiovascular effects of intravenous (IV) alfaxalone bolus injections in healthy pigs.
Materials and methods: Each pig was sedated with ketamine, azaperone, and atropine intramuscularly, mixed in one syringe. Anesthesia was induced and maintained intravenously with alfaxalone. Then, three defined test bolus injections of alfaxalone were given intravenously. Vascular ultrasonography and pulse-induced contour cardiac output thermodilution monitoring were used to evaluate the direct cardiovascular effects after bolus injection. The following vascular and hemodynamic variables were recorded at the right common carotid artery (CCA) for 10 minutes after each alfaxalone injection by ultrasonography, pulse oximetry, and capnometry: peak systolic, minimum diastolic, end-diastolic, and time-averaged blood flow velocities; average volumetric flow; resistance index and vessel diameter; heart rate (HR); arterial oxygen saturation; and end-tidal carbon dioxide (PETCO₂). In addition, pulse contour-derived cardiac output recorded cardiac output, contractility, and volumetric variables for preload and afterload, as well as extravascular lung water, blood temperature, arterial blood pressure, and central venous pressure.
Results: Alfaxalone bolus injections caused an initial short-lasting (0.25 minutes) decrease in diameter at the CCA after each bolus. During this very acute reaction, peak systolic blood flow velocity, thermodilutional cardiac output, and HR increased significantly. Average volumetric flow decreased, but not significantly. Mean arterial blood pressure decreased significantly at a time point of 0.25 minutes. Stroke volume, end-diastolic blood flow velocity, and resistance index did not change significantly. No cumulative effect was seen when three bolus injections of alfaxalone were given.
Conclusion: Alfaxalone bolus injections produced two-phased short-lasting vascular (vasoconstriction at the CCA, vasodilation in the peripheral vessels) and hemodynamic changes (HR, mean arterial pressure), which were easily compensated by young healthy pigs. Because of those very short changes, alfaxalone is a safe hypnotic agent in healthy pigs; however, it may be used carefully in patients with ventricular dysfunction.

Keywords: anesthetics, cardiovascular, alfaxalone, ultrasonography, pigs