RETROSPECTIVE REVIEW OF DEXMEDETOMIDINE-BUTORPHANOL-MIDAZOLAM OR MEDETOMIDINE-BUTORPHANOL-MIDAZOLAM FOR ANESTHESIA OF SEA OTTERS (ENHYDRA LUTRIS) UNDER PROFESSIONAL CARE

A retrospective review of anesthetic events using dexmedetomidine-butorphanol-midazolam (DBM) or medetomidine-butorphanol-midazolam (MBM) for northern (<i>Enhydra lutris kenyoni</i>) and southern (<i>Enhydra lutris nereis</i>) sea otters under professional care was performed. From 2010 to 2023, 96 anesthetic procedures in total were reported across 32 sea otters for various diagnostic, surgical, or preventive health procedures. A subset of 57 anesthetic procedures in 28 apparently heathy sea otters was evaluated to report anesthetic milestones, physiologic values, and perianesthetic observations. Included induction protocols involved IM injection of DBM or MBM, and injectable agents were reversed with IM atipamezole and naltrexone ± flumazenil. Anesthetic events were compared from a subset of sea otters anesthetized with both MBM and fentanyl-midazolam (FM) on separate occasions. Individuals were manually restrained for injection (45/57, 78.9%) or received voluntary injections (12/57, 21.1%); those with voluntary injections had faster time to intubation (<i>P</i> = 0.017) and longer time to extubation (<i>P</i> = 0.015) than those manually restrained. Duration of inhalant anesthesia and antagonism of midazolam with flumazenil had no significant effect on recovery milestones. Physiologic values were within established cutoffs considered by the authors to be clinically acceptable for most sea otters. The most common perianesthetic observation was hypothermia (<37.2°C; 7/57, 12.3%); however, it was only seen in procedures lasting >54 min. Sea otters immobilized with MBM had significantly lower HR (MBM, 114 ± 8 breaths per minute [brpm]; FM, 153 ± 30 brpm; <i>P</i> = 0.03), lower partial pressure of end-tidal CO₂ readings (MBM, 56.8 ± 5.4 mmHg; FM, 92.3 ± 10.8 mmHg; <i>P</i> = 0.002), higher RR (<i>P</i> = 0.03), and higher pulse oximetry readings (<i>P</i> = 0.02) compared with sea otters immobilized with FM. DBM and MBM appear to be safe, reliable protocols with smooth induction and recovery; clinically acceptable physiologic values across various age classes, sexes, and subspecies; and a low rate of complications. Furthermore, MBM appears to be a reliable alternative to FM with more favorable respiratory values.