Five chimpanzees (Pan troglodytes) initially received oral
droperidol sedation (1.25 mg for a juvenile chimpanzee, body wt = 18.5 kg, and 2.5 mg for adults, body wt >20 kg, range: 18.5-71 kg) followed by transmucosal
carfentanil administration at 2.0 microg/kg. This preinduction regimen was developed to produce heavy sedation or even light
anesthesia in order to eliminate the need for or at least minimize the stress of darting with
tiletamine/zolazepam at 3 mg/kg i.m. This study was designed to assess the safety and efficacy of transmucosal
carfentanil. Once each animal was unresponsive to external 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 administered at 100 times the
carfentanil dose in milligrams. For comparison, two chimpanzees received only
droperidol, 2.5 mg p.o., followed by
tiletamine/zolazepam, 3 mg/kg i.m. The preinduction period for all animals receiving
carfentanil was characterized as smooth, with chimpanzees becoming gradually less active and less responsive to external stimuli. Two animals became very heavily sedated at 24 and 35 min, respectively, and were hand injected 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 injection with minimal response. Rectal body temperatures, pulse and respiratory rates, arterial
oxygen hemoglobin saturation, and arterial blood
gases were measured at initial contact (t = 0 min) and at 10-min intervals thereafter.
Respiratory depression was present in all chimpanzees, regardless of protocol. Mean
hemoglobin saturation was 91% for both groups. Mean partial pressure of
oxygen, arterial values for
carfentanil-treated and control animals were 64.4 +/- 7.6 and 63.5 +/- 6.0 at t = 0, respectively. Only the partial pressure of
carbon dioxide, arterial (Paco2) and pH showed significant differences between treated and control animals. Mean Paco2 was greater and mean pH lower for the
carfentanil-treated group compared with the controls 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 effectively as a
premedication regimen to produce profound sedation, which limits the stress of darting during parenteral
anesthetic induction with
tiletamine/zolazepam in chimpanzees. The main side effect of
respiratory depression appears to be adequately managed by reversing the
carfentanil at the time of induction.