The anatomical and physiological characteristics of the Nile hippopotamus (Hippopotamus amphibius) create many anesthetic challenges. Captive Nile hippopotamus anesthesia has historically been fraught with complications. Previous anesthetic protocols have explored the use of potent opioids alone and in combination with other anesthetic agents. Anesthetic events have commonly resulted in apnea, bradycardia, cyanosis, and even death.1 Over the last 12 years, Disney’s Animal Kingdom has explored alternative anesthetic protocols to potent opioids in captive hippopotami, including butorphanol, medetomidine (BM); butorphanol, azaperone, medetomidine (BAM); and ketamine, butorphanol, azaperone, medetomidine (KBAM).
In this retrospective investigation, 12 anesthetic events in captive Nile hippopotami (ranging from 270 kg to 1820 kg) were reviewed. Time to initial effect, time to intubation, and recovery time varied among the different anesthetic protocols. Intubation was achieved in the majority of clinical cases, and all patients received supplemental oxygen. Several venipuncture techniques and sites were explored with varied success. The patients were monitored using electrocardiography, capnography, pulse oximetry, and, in some cases, blood gas analysis. Findings suggest that blood gas data may be the most reliable tool for anesthetic monitoring in Nile hippopotami. The findings of this review suggest that anesthetic protocols using butorphanol, azaperone, and medetomidine may produce reliable anesthetic effects with low rates of complications in captive Nile hippopotami. Further investigation is recommended.
1. Ramsay EC, Loomis MR, Mehren KG, Boardman WS, Jensen J, Geiser D. Chemical restraint of the Nile hippopotamus (Hippopotamus amphibius) in captivity. J Zoo Wildl Med. 1998;29:45–49.