Oral induction of anesthesia with droperidol and transmucosal carfentanil citrate in chimpanzees (Pan troglodytes)

Five chimpanzees (Pan troglodytes) initially received oral droperidol sedat ion (1.25 mg for a juvenile chimpanzee, body wt = 18.5 kg, and 2.5 mg for a dults, body wt >20 kg, range: 18.5-71 kg) followed by transmucosal carfenta nil administration at 2.0 mu g/kg. This preinduction regimen was developed to produce heavy sedation or even light anesthesia in order to eliminate th e need for or at least minimize the stress of darting with tiletamine/zolaz epam at 3 mg/kg i.m. This study was designed to assess the safety and effic acy of transmucosal carfentanil. Once each animal was unresponsive to exter nal stimuli, or at approximately 25 min (range 24-34 min) after carfentanil administration, naltrexone and tiletamine/zolazepam (N/T/Z) were combined into one intramuscular injection for anesthetic induction. Naltrexone was a dministered at 100 times the carfentanil dose in milligrams. For comparison , two chimpanzees received only droperidol, 2.5 mg p.o., followed by tileta mine/zolazepam, 3 mg/kg i.m. The preinduction period for all animals receiv ing carfentanil was characterized as smooth, with chimpanzees becoming grad ually less active and less responsive to external stimuli. Two animals beca me very heavily sedated at 24 and 35 min, respectively, and were hand injec ted with N/T/Z. The other three chimpanzees became sternally recumbent but retained some response to stimuli, and N/T/Z was administered by remote inj ection with minimal response. Rectal body temperatures, pulse and respirato ry rates, arterial oxygen hemoglobin saturation, and arterial blood gases w ere measured at initial contact (t = 0 min) and at 10-min intervals thereaf ter. Respiratory depression was present in all chimpanzees, regardless of p rotocol. Mean hemoglobin saturation was 91% for both groups. Mean partial p ressure of oxygen, arterial values for carfentanil-treated and control anim als were 64.4 +/- 7.6 and 63.5 +/- 6.0 at t = 0, respectively. Only the par tial pressure of carbon dioxide, arterial (PaCO2) and pH showed significant differences between treated and control animals. Mean Pace, was greater an d mean pH lower for the carfentanil-treated group compared with the control s at t = 0 (58.9 +/- 3.7 and 50.3 +/- 3.1 for PaCO2 and 7.33 +/- 0.02 and 7 .40 +/- 0.30 for pH, respectively). The results of this study suggest that oral droperidol followed by transmucosal carfentanil can be used effectivel y as a premedication regimen to produce profound sedation, which limits the stress of darting during parenteral anesthetic induction with tiletamine/z olazepam in chimpanzees. The main side effect of respiratory depression app ears to be adequately managed by reversing the carfentanil at the time of i nduction.