Abstract
A non-opiate drug combination of a potent alpha2 agonist and a dissociative anesthetic was evaluated for capture of 10 free-ranging giraffes (Giraffa camelopardalis) in the Kruger National Park, South Africa. A medetomidine and ketamine combination was given at a ratio of 1:20 via a dart containing 7500 IU of hyaluronidase. The study animals included five males and five females with estimated weights of 190 to 850 kg.
The dosages for medetomidine ranged from 41 to 116 µg/kg with the corresponding 0.8 to 2.3 mg/kg of ketamine (1 to 20 ratio). The time from darting to the onset of signs varied from 1 to 5.5 minutes (average 2.33 minutes), while the time from darting to recumbency varied from 2.75 to 13 minutes (average 7 minutes). Both the time of onset and time to recumbency were related to the dosage. Eight of 10 giraffes became recumbent. Two adult females receiving 48 and 61 µg/kg medetomidine and 1 and 1.2 mg/kg ketamine did not become recumbent, while two others receiving 41 and 50 µg/kg medetomidine and 0.8 and 1 mg/kg ketamine did. All giraffes receiving 78 to 116 µg/kg medetomidine and 1.6 to 2.3 mg/kg ketamine became recumbent in less than 9 minutes.
There was minimal excitement during the induction phase as the giraffe tended to stand and went down in a controlled manner. Once recumbent, the giraffes were monitored every 5 minutes during a 30-minute period for heart rate, respiration rate, rectal temperature, indirect blood pressure, and blood gases. Hyperventilation was present in all giraffes during the procedure, with an average of 74 breaths/minute (range of 24 to 126). There was a snoring respiration that was not corrected by repositioning the head and neck. Heart rates remained above 30 beats/minute in all animals, with an average rate of 44 beats/minute. The blood pressure was well maintained, with an average systolic pressure of 190 mm Hg and a diastolic pressure of 110 mm Hg. There was no elevation in body temperature during the procedure. The blood gas evaluation showed an initial slight acidosis, which corrected itself by the end of the recumbency.
The giraffes were given atipamezole IM at dosages of 114 to 222 µg/kg (average 189 µg/kg) to antagonize the medetomidine, which produced a smooth and rapid recovery in an average of 6 minutes and 40 seconds (range 2 to 14 minutes). Four of these giraffes were observed 24 hours later, and they appeared normal.
There were major differences noted when comparing anesthetic protocols which use opiates (etorphine or carfentanil).1-3 Giraffes given a medetomidine and ketamine combination: 1) are aware of ground personnel and would avoid or strike out at them, so it was not possible to use a rope to contain and cast them; 2) did not exhibit a forced pacing behavior and went down in a controlled manner rather than crashing down or going over backward; 3) did not show respiratory depression, but instead hyperventilated; and 4) are sedated and not anesthetized since they respond to minor manipulation with increased heart rates, and therefore supplemental anesthetic agents would be required prior to any painful procedure and to obtain complete muscle relaxation.
A medetomidine (78 to 116 µg/kg) and ketamine (1.6 to 2.3 mg/kg) combination proved to be a safe and effective combination for capture of free-ranging giraffes. This combination should greatly improve the safety and reliability of anesthesia in captive giraffes. The use of concurrent anesthetics is indicated in potentially painful manipulations.
Literature Cited
1. Bush, M. 1993. Anesthesia of high-risk animals: giraffe. In: Zoo and Wild Animal Medicine—Current Therapy 3. Fowler M.E., ed. W.B. Saunders Co., Philadelphia. Pp 545–547.
2. Bush, M. and de Vos, V. 1987. Observations on field immobilization of free-ranging giraffe (Giraffa camelopardalis) using carfentanil and xylazine. J. Zoo Anim. Med. 18:135–140.
3. Bush, M., Ensley, P.K., Mehren, K., and Rapley, W. 1976. Immobilization of giraffes with xylazine and etorphine hydrochloride. J. Am. Vet. Med. Assoc. 169(9):884–885.