Abstract

The use of alpha-2 agonists in great apes undergoing anesthesia for cardiovascular evaluation is controversial. This pilot study aimed to characterize the cardiopulmonary characteristics of two anesthetic protocols (tiletamine/zolazepam ±20 µg/kg medetomidine) and evaluate their suitability for the immobilization of healthy chimpanzees undergoing cardiac assessment.

Six chimpanzees (Pan troglodytes) (4 to 16 years old; 2 males, 4 females) were anesthetized on two occasions in a crossover design. Anesthesia was induced with intramuscular administration of zolazepam/tiletamine (3–4 mg/kg) (ZT) or zolazepam/tiletamine (2 mg/kg) plus medetomidine (20 µg/kg) (ZTM), and maintained with intermittent boluses of ketamine (0.2 mg/kg IV; 0.7–1.5 mg/kg IM) or zolazepam/tiletamine (0.7–1 mg/kg IM).

Quality of anesthesia (quality of induction, degree of muscle relaxation, ease of intubation), time to recumbency, number of supplemental boluses and recovery characteristics were recorded. Chimpanzees were continuously monitored and heart (HR) and respiratory (fr) rates, peripheral oxygen saturation (SpO₂), rectal temperature, indirect arterial blood pressure (SAP, MAP, DAP) and mucous membrane color recorded. Animals underwent full hematology, biochemistry and detailed echocardiographic examination (carried out by one observer, blinded to the treatment group). Data were compared using Student’s paired t-test or Wilcoxon rank tests as appropriate.

The ZTM protocol was associated with significantly lower HR (62±6 versus 87±3 beats/minute), MAP (85±11 versus 111±10 mm Hg), SAP (116±22 mm Hg versus 150±23 mm Hg) and SpO₂ (93±4 versus 98±1%) when compared with the ZT protocol. No significant differences in the echocardiographic measurements (including Ao, LA, IVSd, LVIDd/s, LVPW, EF) were identified between the two anesthetic protocols.

Quality of anesthesia score was significantly higher with ZTM, and no supplemental anesthesia was required during the duration (64±14 minutes). The median number of supplemental doses required during the TZ procedure was 3.5 (2–7).

This study concluded that both anesthetic combinations are suitable for the immobilization and cardiovascular evaluation of healthy chimpanzees. Further work is required to evaluate the effects of medetomidine in cardiovascular disease.

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