Abstract

Giraffe (Giraffa camelopardalis) anesthesia remains a major challenge due to their unique anatomy and physiology, which predisposes them to life-threatening, anesthesia-related complications.^1,3,15 Historic verbal and published reports describe the use of several drugs and drug combinations for giraffe anesthesia.^1-5,9,13-15 The most widely used anesthetic regimens have involved use of opioids alone or in combination with sedatives (e.g., xylazine) or tranquilizers (e.g., azaperone).^{1-3,5,9,13-15} Current methods for field anesthesia generally involve darting giraffe with very high doses of an opioid (etorphine, thiafentanil, or carfentanil) combined with hyaluronidase for rapid induction and then reversing the opioid as soon as the giraffe is recumbent to reduce consequences of the opioid overdose.^14,15 This anesthetic technique greatly limits what can safely be done to a giraffe while it is recumbent. A combination of medetomidine and ketamine is currently considered a safe and reliable alternative to opioid combinations for captive giraffe but is considered less than optimal for capture of free-ranging giraffe.^1,2,4

A newer drug combination, thiafentanil(A3080)-medetomidine-ketamine, has safely and successfully been used for chemical restraint of other difficult hoof stock species in the field.^6-8,10 Currently, a total of 50 anesthetic events with this combination have been performed on giraffe: 12 captive; 29 free-ranging, ground-darted; and 9 free-ranging helicopter-darted. Dosing requirements are markedly different between the three study groups:

1.  Captive: thiafentanil 5.8±1.5 µg/kg + medetomidine 12.9±5.1 µg/kg + ketamine 0.65±0.18 mg/kg.

2.  Free-ranging, ground-darted: thiafentanil 6.6±1.5 µg/kg + medetomidine 15.9±3.7 µg/kg + ketamine 0.50±0.19 mg/kg.

3.  Free-ranging, helicopter-darted: thiafentanil 10.0±4.0 µg/kg + medetomidine 14.0±9.4 µg/kg + ketamine 0.39±0.20 mg/kg.

Weights of giraffe were estimated by body measurements as previously described.¹¹ The degree of excitement associated with helicopter darting appears to negate the effects of medetomidine, so at least twice the dose of thiafentanil is required to slow giraffe in the field.

Onset of action was ultra-rapid in all three groups (<1.5 minutes) but time to recumbency varied greatly (three minutes in captive giraffe to 12 minutes in free-ranging, helicopter-darted giraffe). Nine of 29 free-ranging, ground-darted giraffe and seven of nine free-ranging, helicopter-darted giraffe needed to be cast with ropes. Most giraffe were rated to have good muscle relaxation once recumbent and were considered safe to work around for all ground personnel during the monitoring period. Most study animals exhibited an accentuated apneustic breathing pattern. Significant physiologic alterations seen during the study were mild to severe hypoxemia, mild hypercarbia, and a moderate mixed acidosis. The hypoxemia was persistent throughout the monitoring period while the hypercarbia and acidosis improved through the monitoring period.

Anesthesia was reversed with 30 mg naltrexone for each mg thiafentanil and atipamezole at 3–5 times the medetomidine mg dose, half IV and half IM in most cases. Arousal time was rapid in most animals. It was necessary to give the giraffe ample time to gain full awareness before stimulating them to rise or they would tend to be ataxic when they stood and would often fall back down. Once standing, most blind-folded, haltered, free-ranging giraffe were calm during chariot loading with very little kicking, rearing, or bolting attempts. Evidence of medetomidine-associated re-sedation was seen in some giraffe post-reversal requiring additional supplements of atipamezole.

In conclusion, thiafentanil-medetomidine-ketamine is a useful anesthetic combination for captive and free-ranging, ground-darted giraffe, especially for longer procedures and when good muscle relaxation and analgesia are required. As with most anesthetic protocols, oxygen supplementation or respiratory support should be available when using this drug combination on giraffe. Re-sedation in giraffe given medetomidine has been reported before,¹² is worrisome, and requires further study.

Acknowledgments

This study was funded through a grant from the Morris Animal Foundation (#D03ZO-63). The authors wish to thank Dr. Peter Buss and David Zimmerman of South African National Parks, JJ van Altena of CatchCo Africa, and the South African National Parks and CatchCo capture teams for their assistance with this study, and Dr. Cobus Raath of Wildlife Pharmaceuticals, South Africa for supplying many of the drugs used in this study.

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