The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.
OBJECTIVE
To determine the cardiorespiratory and anesthetic effects of 0, 5, 15, and 50 mg kg(-1) intravenous (IV) alfaxalone in hydroxypropyl beta cyclodextrin (Alfaxan; Jurox Pty Ltd, Rutherford, NSW, Australia) in cats.


METHODS
Four treatments of alfaxalone were administered in sequential order.


METHODS
Eight healthy adult cats (four male; four female) weighing between 3.71 and 5.91 kg.


METHODS
Cats were instrumented for hemodynamic measurements. Four (0, 5, 15, and 50 mg kg(-1)) IV doses of alfaxalone were administered over one minute, with a 3-hour washout period between doses 0, 5, and 15 mg kg(-1) on Day 0. The 50 mg kg(-1) treatment was administered 24 hours later. Measurements of heart rate, aortic systolic, mean, and diastolic blood pressures, pulmonary arterial and right atrial mean pressures, cardiac output, respiratory rate, tidal and minute volumes, and arterial blood pH and blood gases (PaO(2), PaCO(2)) were performed at pre-determined intervals. Systemic vascular resistance and rate pressure product were calculated. The quality of induction, maintenance, and recovery from anesthesia and the response to noxious stimulation were categorically scored.


RESULTS
Alfaxalone administration resulted in dose-dependent cardiorespiratory depression. Decreases in arterial blood pressure and increases in heart rate occurred at higher doses. Most variables returned to baseline by 15-30 minutes. Respiratory rate, minute volume, and PaO(2) decreased. Apnea was the most common side effect. Induction and maintenance quality were judged to be good to excellent at all doses and quality of recovery good to excellent at all but the 50 mg kg(-1) dose. The duration of anesthesia and unresponsiveness to noxious stimulation increased with dose. The administration of the 50 mg kg(-1) dose produced marked cardiorespiratory depression and apnea.


CONCLUSIONS
Alfaxalone produced dose-dependent anesthesia, cardiorespiratory depression and unresponsiveness to noxious stimulation in unpremedicated cats. Hypoventilation and apnea were the most common side effects.
Muir
William
W
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, OH, USA. muirww111@gmail.com
Lerche
Phillip
P
Wiese
Ashley
A
Nelson
Laura
L
Pasloske
Kirby
K
Whittem
Ted
T
D000771:Anesthesia, Intravenous / Q000662:veterinary*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D002415:Cats; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D011277:Pregnanediones / Q000008:administration & dosage* / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects*
D018686:Anesthetics, Intravenous; D011277:Pregnanediones; C006477:alphaxalone