Abstract

In recent years, tiletamine-zolazepam has emerged as a preferred safe anesthetic for use in European wild boars.^3,11 Tiletamine-zolazepam alone may cause rough and prolonged recoveries in both domestic pigs and wild boars^3,5,8,10 and the combination may not produce muscle relaxation and analgesia adequate for invasive procedures.³ Addition of an alpha₂-adrenergic agonist, improves analgesia and muscle relaxation, and smoother recoveries are achieved.^3-5,8,9

The addition of butorphanol, a synthetic opioid agonist-antagonist, may enhance the sedative effect of medetomidine⁶ and is likely to produce more efficient preemptive analgesia. By adding medetomidine to tiletamine-zolazepam, alone or in combination with butorphanol, a lower dose of tiletamine-zolazepam is likely to be needed to achieve surgical anesthesia. Due to the lower dose of this drug, rough and prolonged recoveries characteristic for residual activity of tiletamine-zolazepam would likely be minimized after reversal of medetomidine with atipamezole.

The purpose of this study was to evaluate the physiologic effects of medetomidine/tiletamine-zolazepam and medetomidine/butorphanol/tiletamine-zolazepam anesthesia and reversal with atipamezole in juvenile wild boars undergoing surgical implantation of intraperitoneal radiotransmitters under field conditions.

Individual juvenile wild boars were captured in baited cage traps. In all sows, anesthesia was induced by injection of the anesthetic drugs into the cervical musculature. The medetomidine/tiletamine-zolazepam (MTZ) group, consisting of eight pigs, received 0.1 mg/kg of medetomidine (Domitor® 1 mg/ml, Orion Corporation Animal Health, Turku, Finland) and 5 mg/kg of tiletamine-zolazepam (Zoletil® 125 mg tiletamine + 125 mg zolazepam dry substance/vial, Virbac Laboratories, Carros, France). The medetomidine/butorphanol/tiletamine-zolazepam (MBTZ) group, consisting of eight pigs, received 0.05 mg/kg of medetomidine, 0.2 mg/kg of butorphanol (Torbugesic® 10 mg/ml, Fort Dodge Laboratories, Fort Dodge, IA, USA) and 3 mg/kg of tiletamine-zolazepam. Relative arterial oxygen saturation and pulse rate were monitored using a pulse oximeter. Rectal temperature was recorded immediately after induction and just prior to reversal.

The surgical procedure for implantation of radiotransmitters into the peritoneal cavity has been described previously.^1,2 After surgery, anesthesia was reversed with atipamezole (Antisedan® 5 mg/ml, Orion Corporation Animal Health, Turku, Finland) at 0.5 mg/kg IM in the MTZ group and 0.25 mg/kg in the MBTZ group.

Mean ± SD (standard deviation) body weight, induction time, procedure time, body temperature, blood oxygen saturation, and heart rate in the MTZ and MBTZ groups are listed in Table 1. Induction of anesthesia was smooth and rapid in both groups. Analgesia was sufficient during the entire length of anesthesia in both treatment groups. At no time during anesthesia did the mucous membranes of the animals appear cyanotic. Recovery results could only be obtained from three pigs in each group due to reasons of time constraint and logistics. The recoveries were characterized by paddling movements and unsuccessful attempts to rise. The standing times recorded in the MTZ group were 32, 57, and 63 minutes and in the MBTZ group 20, 20, and 23 minutes. At this time pigs were able to walk but showed severe ataxia and evidence of hind-limb weakness.

Table 1. Body weight, induction time, procedure time, body temperature, blood oxygen saturation, and heart rate in medetomidine/tiletamine-zolazepam (MTZ) and medetomidine/butorphanol/tiletamine-zolazepam (MBTZ) treated wild boars. Data are given as mean ± SD

^a Time from injection to complete immobilization.
^b Time from initial injection to time of injection of atipamezole.
^c Recorded immediately after induction of anesthesia.
^d Recorded immediately prior to injection of atipamezole.
^e At 16 minutes post-injection.

A significantly lower mean pulmonary arterial pressure and higher pulmonary vascular resistance is reported in atropinized pigs receiving a combination of medetomidine and butorphanol than in those receiving medetomidine only.⁷ These findings may explain the lower pulse oximetry values seen in the MBTZ group.

The rough recoveries seen in this study are attributed to residual tiletamine-zolazepam activity. The data are not sufficient for definite conclusions to be drawn, but the results suggest that combining medetomidine with butorphanol, decreases the requirement for tiletamine-zolazepam and reduces the length of the recovery period.

In conclusion, MTZ and MBTZ constitute satisfactory alternatives for anesthesia in wild boars but should ideally be used with supplemental oxygen at hand. In the opinion of the authors, the disadvantageous depression in heart rate and blood oxygen saturation seen in the MBTZ group are outweighed by the advantage of butorphanol-mediated analgesia. The rough recoveries seen after both anesthetic regimens in this study warrant further investigation into these and into new drug combinations.

Acknowledgments

The authors wish to thank Bo Söderberg for technical and field assistance, Leif Fredriksson for providing housing at the study site, Dr. Görel Nyman and Dr. Jean Paré for reviewing the manuscript, and Dr. Brenda Bonnett for useful comments on statistics.

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