Subcutaneous Alfaxalone-Xylazine-Buprenorphine for Surgical Anesthesia and Echocardiographic Evaluation of Mice (Mus musculus)

Abstract

Alfaxalone is a commonly used injectable anesthetic in dogs and cats due to its minimal cardiovascular side effects. Data for its use in mice are limited and demonstrate strain- and sex-associated differences in dose-response relationships. We performed a dose-comparison study of alfaxalone-xylazine-buprenorphine (AXB) in Crl:CFW(SW) mice. Subcutaneous injection of 50 mg/kg alfaxalone-10 mg/kg xylazine-0.1 mg/kg buprenorphine HCl consistently achieved a surgical plane of anesthesia (loss of toe pinch) for 48.6 ± 4.7 and 60.8 ± 9.6 min in females and males, respectively. The same dose and route of AXB induced a surgical plane of anesthesia in C57Bl/6NCrl (females: 42.3 ± 11.2 min; males: 51.6 ± 12.3 min), NCr-Foxn1nu (females: 76.8 ± 32.5 min; males: 80.0 ± 1.2 min), and NOD.Cg-PrkdcSCIDIl2rgtm1Wjl/SzJCr (females: 56.0 ± 37.2 min and males: 61.2 ± 10.2 min) mice. We found no significant difference in the duration of the surgical plane of anesthesia between males and females within the mouse strains Crl:CFW(SW), C57Bl/6NCrl, NCr-Foxn1nu, and NOD.Cg-PrkdcSCIDIl2rgtm1Wjl/SzJCr. We next performed an echocardiography study (n = 5 per group) of Crl:CFW(SW) mice (n = 5 per group) to compare subcutaneous AXB anesthesia with that produced by intraperitoneal injection of 100 mg/kg ketamine and 10 mg/kg xylazine (KX). AXB induced significantly less bradycardia (295.4 ± 29 bpm) than KX (185.8 ± 38.9 bpm) did, with no significant differences in cardiac output, ejection fraction, end-diastolic volume, end-systolic volume, or fractional shortening. These results suggest that subcutaneous administration of AXB is a viable alternative to KX for inducing a surgical plane of anesthesia in Crl:CFW(SW), C57Bl/6NCrl, NCr-Foxn1nu, and NOD.Cg-PrkdcSCIDIl2rgtm1Wjl/SzJCr mice, regardless of sex. AXB may also be a better injectable anesthetic option as compared with KX for avoiding adverse cardiac effects in mice.