Rabbits are common research subjects and popular household pets, and demand for their veterinary care, including surgical procedures requiring general anesthesia, has increased in the United States in recent years.1 In 1 study,2 the mortality rate of rabbits undergoing anesthesia was significantly higher than that of dogs and cats. The exact reason for this is unknown, but 1 proposed mechanism may be hypotension associated with inhalation anesthesia in this species.3,4
In some species, μ-opioid receptor agonists, such as fentanyl, reduce the amount of inhalation anesthetic required to prevent movement in response to a noxious stimulus, as evidenced by a reduction in MAC.5,6 In addition to their analgesic effects, the reduction in inhalation anesthetic dose afforded by opioid receptor agonists is associated with reduced magnitude of cardiovascular depression in some species.6,7
Fentanyl has been shown to reduce isoflurane MAC in rabbits8; however, to our knowledge, whether this provides cardiovascular benefits has not been investigated. The aim of the study reported here was to determine the effects of equipotent immobilizing doses of isoflurane alone and in combination with fentanyl at 3 targeted plasma concentrations on cardiovascular variables in New Zealand White rabbits (Oryctolagus cuniculus). We hypothesized that combinations of isoflurane and fentanyl would result in significantly less cardiovascular depression than an equipotent concentration of isoflurane alone.
Supported by the University of California-Davis Center for Companion Animal Health.
Presented in abstract form at the American College of Veterinary Anesthesia and Analgesia Annual Meeting, Indianapolis, September 2014.
Central venous pressure
Minimum alveolar concentration
Mean arterial blood pressure
Systolic arterial blood pressure
Systemic vascular resistance index
High Fiber Rabbit Diet No. 5326, PMI Nutrition International, Brentwood, Miss.
Oxbow Animal Health, Murdock, Neb.
Suburban Surgical, Wheeling, Ill.
RUGLOOP I, Demed, Temse, Belgium.
Harvard PhD 22/2200, Harvard Apparatus, Hollister, Mass.
Abbott Animal Health, Abbott Park, Ill.
Intracan Safety Catheter, B Braun Melsungen AG, Melsungen, Germany.
Baxter Healthcare, Deerfield, Ill.
Fentanyl citrate, Hospira Inc, Lake Forest, Ill.
Insyte catheter, Becton-Dickinson, Sandy, Utah.
GE Healthcare, Helsinki, Finland.
Hotdog, Augustine Temperature Management, Eden Prairie, Minn.
Hallowell EMC, Pittsfield, Mass.
Grass Instrument Co, Quincy, Mass.
Check-Flo, Cook Inc, Bloomington, Ind.
Thermodilution balloon catheter, Arrow International, Reading, Pa.
DTX-Plus, Argon Medical Devices, Plano, Tex.
PowerLab, ADInstruments, Dunedin, New Zealand.
LabChart, ADInstruments, Dunedin, New Zealand.
COM-1, American Edwards Laboratories, Irvine, Calif.
Clinitube, Radiometer Medical, Copenhagen, Denmark.
i-STAT CG4+ Abbott Point of Care, Abbott Laboratories, Abbott Park, Ill.
Fisherbrand, ThermoFisher Scientific, Waltham, Mass.
Robinul, West-Ward Pharmaceuticals, Eatontown, NJ.
Buprenex injectable, Reckitt Benckiser, Richmond, Va.
Ethicon, Somerville, NJ.
Loxicom, Norbrook Laboratories Ltd, Newry, Northern Ireland.
Prism, version 6, GraphPad Software Inc, La Jolla, Calif.
Critical Care, Oxbow Animal Health, Murdock, Neb.
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