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Medetomidine-ketamine-isoflurane anaesthesia in pygmy hippopotami (Choeropsis liberiensis) – a case series


Tim Bouts, Zoological Society London, ZSL Whipsnade Zoo, Veterinary Department, Whipsnade, Bedfordshire, LU6 1DP, UK. E-mail:


History  Medical knowledge of pygmy hippopotami is limited. Anaesthesia has been considered a challenge because of the anatomy, semi-aquatic life style and aggressive behaviour. Polycystic kidney disease (PKD) has been described and can contribute to active kidney disease potentially affecting anaesthesia.

Physical examination and Management  Fourteen pygmy hippopotami were anaesthetized for general health assessment and reproductive procedures. Animals (estimated bodyweight 250 kg) were darted intramuscularly with 0.08 mg kg−1 medetomidine and 1.2 mg kg−1 ketamine. After endotracheal intubation, anaesthesia was maintained with isoflurane delivered either by circle system (100% oxygen) or by Triservice apparatus (air or air/oxygen admixture). Heart rate (HR) respiratory rate (fR), oxygen saturation (SpO2) and end tidal CO2 were recorded at 5-minute intervals. Atipamezole was administered intramuscularly (0.4 mg kg−1) at the end of the procedure. Statistical analysis was performed using anova (< 0.05).

Most animals rapidly became recumbent although five hippopotami needed additional drugs to assure acceptable immobilization. There were no statistical differences in mean HR between animals with or without PKD (PKD: 34 ± 8 beats minutes−1; no PKD: 33 ± 6 beats minutes−1), fR (PKD: 15 ± 7 breaths minutes−1; no PKD; 12 ± 5 breaths minutes−1) and end tidal CO2 (PKD: 7.1 ± 1.3 kPa; no PKD: 7.8 ± 1.4 kPa). SpO2 was higher in animals receiving 100% oxygen or air with oxygen (92 ± 8% and 91 ± 9% respectively) compared with animals receiving air only (77 ± 5%) (= 0.003). Recovery was uneventful after atipamezole administration.

Follow-up  There were no apparent adverse effects after anaesthesia during a 24-hour follow-up period.

Discussion and conclusions  Medetomidine-ketamine-isoflurane induced satisfactory anaesthesia in this species. Incremental induction doses were related to remote injection and the animals’ thick skin. There were no differences in anaesthetic parameters in animals with or without PKD. Supplemental oxygen should be mandatory during anaesthesia in this species.