Cardiorespiratory effects of four alpha(2)-adrenoceptor agonist-ketamine combinations in captive red wolves

Objective-To evaluate the cardiopulmonary effects of immobilizing doses of xylazine-ketamine (XK), medetomidine-ketamine (MK), medetomidine-ketamine-a cepromazine (MKA), and medetomidine-butorphanol-ketamine (MBK) in captive r ed wolves. Design-Prospective study. Animals-32 adult captive red wolves. Procedure-Wolves were randomly assigned to 1 of 4 treatment groups: XK, MK, MKA, or MBK. Physiologic variables measured included heart rate, blood pre ssure, respiratory rate, tidal volume, oxygen-hemoglobin saturation (Spo(2) ), end-tidal CO2, arterial blood gases, and rectal temperature. Induction t ime, muscle relaxation, and quality of recovery were assessed. Results-Heart rates were lower in wolves in the MBK group than for the othe r groups. All 4 drug combinations induced considerable hypertension, with d iastolic pressures exceeding 116 mm Hg. Blood pressure was lowest in wolves receiving the MBK combination. Respiratory rate was significantly higher i n wolves receiving XK, MK, and MKA. Tidal volumes were similar for all grou ps. Wolves receiving XK, MK, and MKA were well-oxygenated throughout the pr ocedure (Spo(2) > 93%), whereas those receiving MBK were moderately hypoxem ic (87% < Spo(2) < 93%) during the first 20 minutes of the procedure. Hyper thermia was detected initially following induction in all groups. Conclusions and Clinical Relevance-The alpha (2)-adrenoceptor agonist-ketam ine combinations provide rapid reversible anesthesia for red wolves but cau se severe sustained hypertension. Such an adverse effect puts animals at ri sk for development of cerebral encephalopathy, retinal hemorrhage, pulmonar y edema, and myocardial failure. Although the MBK combination offers some a dvantages over the others, it is advised that further protocol refinements be made to minimize risks associated with acute hypertension.