No aping around after anesthetic combination

Aug 15 2012

By Sarah Guy, MedWire Reporter

A combination of medetomidine and ketamine administered intramuscularly to chimpanzees, orangutans, and gorillas results in reliable immobilization for both the animals and personnel handling them, report researchers.

However, the team stresses that this anesthetic approach should only be used to carry out minor procedures due to the short-term anesthetic effect.

"When longer clinical procedures are planned, it is suggested to prolong the duration of anesthesia with isoflurane," write Chiara Adami (University of Berne, Länggasstrasse, Switzerland) and colleagues in Veterinary Record.

A total of 20 great apes were anesthetized prior to transportation to temporary accommodation, including six orangutans that were given medetomidine 40 µg/kg and ketamine 5 mg/kg, and eight chimpanzees and six lowland gorillas that were all given medetomidine 50 µg/kg and ketamine 5 mg/kg via dart.

The mean time to anesthesia for chimpanzees, orangutans, and gorillas was 12.1, 18.5, and 22.2 minutes, respectively, with a mean duration of 10, 20, and 16 minutes, respectively.

When the researchers noted an increase in hand or jaw muscle tone or an enhancement of the palpebral reflex, the anesthetic was considered to have become superficial and they administered isoflurane in 100% oxygen via a face mask. In all 12 animals required this, most of which underwent further, lengthier, or painful procedures including castration and a computed tomography scan.

Adami and co-researchers report that all apes breathed spontaneously during anesthesia, and their capnography and pulsoxymetry as well as cardiovascular parameters, including pulse quality and heart rate, all remained in the normal ranges. Furthermore, none showed complications and recovery was "smooth and uneventful in all animals."

They suggest that the short duration of anesthetic effect could result from the pharmacology of these drugs in apes, or an incomplete delivery from the dart.

"The main concern when anesthetizing great apes not trained to be handled is the risk for the personnel; their large size and physical strength create the potential for severe human injury," explain the authors.

"For these reasons, when administering a chemical restraint to great apes, effectiveness and safety of the anesthetic protocol are both of paramount importance," they conclude.

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