Medetomidine, midazolam, and butorphanol anesthesia with preoxygenation enables magnetic resonance imaging and cerebrospinal fluid examination in rabbits.

Abstract

Objective: To evaluate the feasibility of medetomidine, midazolam, and butorphanol (MMB) anesthesia with oxygen supplementation for neurological procedures.

Methods: Five adult male rabbits underwent a randomized crossover study comparing oxygen (OG; 3 L/min via mask before and during anesthesia) and air (AG; room air) groups (experiment 1) during IM MMB (medetomidine, 0.15 mg/kg; midazolam, 1.0 mg/kg; and butorphanol, 1.5 mg/kg), with atipamezole and flumazenil as antagonists. Arterial blood gases, oxygen saturation, and anesthesia scores were assessed. In experiment 2, MRI and cerebrospinal fluid (CSF) collection were performed under the same protocol to evaluate feasibility.

Results: All rabbits recovered uneventfully. In experiment 1, oxygen saturation remained at 98% to 100% in the OG but was significantly lower in the AG (least median, 86%; IQR, 78.5% to 91.5%). The Pao2 was markedly higher in the OG, whereas it remained below 88 mm Hg, which has been defined as hypoxemia, in the AG. Hypoxemia occurred only in the AG, and 4 of 5 rabbits required supplemental oxygen. The Paco2 was significantly higher both in the OG and in the AG after 5 minutes post-MMB administration. Adequate immobilization was achieved in both groups, and all rabbits recovered from the antagonist. In experiment 2, MRI and CSF procedures were successfully completed under MMB with oxygen supplementation.

Conclusions: Intramuscular MMB anesthesia with preoxygenation and continuous oxygen supplementation prevents hypoxemia while providing adequate immobilization for MRI and CSF examinations in rabbits.

Clinical relevance: This protocol may be useful for performing MRI and CSF examinations in rabbits.