Effects of Combining Nitroprusside with Medetomidine-Azaperone-Alfaxalone in Captive White-Tailed Deer (Odocoileus virginianus)
Wildlife immobilization has experienced much refinement, but there is still room for improvement in induction time. Medetomidine causes profound vasoconstriction; this may limit its absorption locally and have an impact on induction time. This study aimed to determine if adding the vasodilator nitroprusside to medetomidine-azaperone-alfaxalone combination anesthesia resulted in a more rapid induction of anesthesia. In a crossover study, nine captive female white-tailed deer were hand-injected intramuscularly with either control (0.15 mg/kg medetomidine, 0.2 mg/kg azaperone, and 0.5 mg/kg alfaxalone) or treatment (0.07 mg/kg nitroprusside added) and released into an enclosure for observation. Once recumbent, monitoring equipment was placed; arterial blood gas (ABG) was analyzed at 15 min post injection (PI); heart and respiratory rate, SpO2, rectal temperature, and direct systolic, mean, and diastolic arterial blood pressures were recorded every 5 min; and after 60 min PI, deer were reversed with intramuscular atipamezole (0.75 mg/kg). Statistical analysis was performed using ANOVA and descriptive statistics with a significance level of p<0.05. Induction with nitroprusside (time to lateral recumbency 5.5±3.0 sec) was not significantly different from control (7.1±3.3 sec). Direct systolic, mean, and diastolic blood pressures were significantly lower with nitroprusside treatment. Interestingly, a significant improvement in oxygenation was observed with the nitroprusside treatment, as evidenced by an increased PaO2 (52.8±3.1 mm Hg for control; 61.4±2.5 mm Hg for treatment) in ABG samples. Although nitroprusside induced no significant reduction in induction time, the significant increase in oxygenation is worthy of further investigation.