Evaluation of butorphanol, medetomidine and midazolam as a reversible narcotic combination in free-ranging African lions (Panthera leo)

Abstract

ObjectiveTo evaluate the effects of the combination butorphanol, medetomidine and midazolam (BMM) and its reversibility in lions. Study designProspective clinical trial. AnimalsThirty free-ranging lions, 10 male and 20 female, weighing 81-210 kg. MethodsLions were immobilised with butorphanol mean 0.31 ± SD 0.034 mg kg−1, medetomidine 0.052 ± 0.006 mg kg−1, midazolam 0.21 ± 0.024 mg kg−1 and hyaluronidase 1250 IU administered intramuscularly with a dart gun. Upon recumbency, physiological parameters and anaesthetic depth were monitored 10-15 minutes after darting (T1) and repeated every 10 minutes for a further 30 minutes (T2, T3, T4). Arterial blood gas analyses were performed at T1 and T4. At the end of the procedure, 45-60 minutes after initial darting, immobilisation was reversed with naltrexone 0.68 ± 0.082 mg kg−1, atipamezole 0.26 ± 0.031 mg kg−1, and flumazenil 0.0032 ± 0.0007 mg kg−1 administered intravenously and subcutaneously. ResultsThe BMM combination rapidly induced immobilisation and lateral recumbency was reached within 7.25 ± 2.3 minutes. Median induction score [scored 1 (excellent) to 4 (poor)] was 1.4 (range 1-2). Cardio-respiratory parameters were stable. Heart rate varied from 32 to 72 beats per minute, respiratory rate from 14 to 32 breaths minute−1 and rectal temperature from 36.6 to 40.3 °C. No sudden arousals were observed. Arterial blood gas analyses revealed a mean pH of 7.33, PaCO2 of 33 mmHg and PaO2 of 87 mmHg. Mild to moderate hypoxemia was seen in four lions. Recovery was smooth and lions were walking within 4.4 ± 4.25 minutes. Median recovery score [scored 1 (excellent) to 4 (poor)] was 1.3 (range 1-2). Conclusion and clinical relevanceThe drug combination proved to be effective in immobilising free-ranging healthy lions of both sexes with minimal cardio-respiratory changes.