Topics in Medicine and Surgery Anesthetic Considerations for Amphibians Mark A. Mitchell, DVM, MS, PhD Abstract The popularity of amphibians in research, zoological exhibits, and as pets is on the rise. With this increased popularity comes a need for veterinarians to develop methods for managing these animals for various diagnostic and surgical proce- dures. For many of these procedures, the provision of anesthesia is a must. Fortunately, there are a number of different anesthetics available to the veterinary clinician for anesthetizing amphibians, including tricaine methanesulfonate, clove oil, propofol, isoflurane, and ketamine. In addition to the variety of anesthetics at our disposal, there is also a wider range of methods for delivering the anesthetics than are generally available for higher vertebrates, including immersion, topical, and intracoelomic routes of delivery. The purpose of this article is to review the different methods that can be used to successfully manage an amphibian patient through an anesthetic event. Copyright 2009 Elsevier Inc. All rights reserved. Key words: amphibian; anesthesia; anesthetic; anuran; monitoring; urodelan mphibians are commonly used in research will respond to an anesthetic the same way. In cases and are popular exhibit animals in zoological in which there is no reference for a particular spe- Acollections. Although they are not as popular cies, special precautions should be taken to mini- as reptiles in the pet trade, they are being presented mize the likelihood of complications. to veterinarians in clinical practice with increased Regardless of the species, success with anesthesia frequency. Because veterinarians are being asked to can be achieved by following a consistent, well- work with these animals, it is important that we planned protocol. For the author, the most pressing develop standard protocols for managing them in points to consider when establishing a protocol are captivity. the preanesthetic examination, the selection of an Historically, anesthesia has been a specialty in anesthetic that will allow the veterinarian to perform herpetological medicine that has received little at- the desired procedure safely, an anesthetic-monitor- tention. Procedures were often completed with an ing protocol that will help to determine the level of animal being manually restrained or cooled to min- anesthesia, and a postanesthetic plan that considers imize movement. Because these methods would not the recovery and management of the animal af- be acceptable for birds or mammals, they should also not be considered acceptable for reptiles or amphib- ians. Fortunately, in the past 2 decades we have seen From the University of Illinois, College of Veterinary Medicine, an increase in the number of scientific studies eval- Department of Veterinary Clinical Medicine, Urbana, IL USA. uating anesthetics in amphibians. Although many of Address correspondence to: Mark A. Mitchell, DVM, MS, PhD, University of Illinois, College of Veterinary Medicine, Department these articles have been directed toward a specific of Veterinary Clinical Medicine, 1008 W. Hazelwood Dr, Urbana, species, Xenopus laevis, because of its value in re- IL 61802. E-mail: [email protected]. search, the information obtained does have applica- © 2009 Elsevier Inc. All rights reserved. tion across amphibian species.1-4 However, it should 1557-5063/09/1801-$30.00 not be assumed that all 4500ϩ species of amphibians doi:10.1053/j.jepm.2008.11.006 40 Journal of Exotic Pet Medicine, Vol 18, No 1 ( January), 2009: pp 40–49 Anesthetic Considerations for Amphibians 41 ter the completion of the procedure. The purpose require a high degree of restraint for an examina- of this article is to review the methods that can be tion. Urodelans can often be examined while being used to successfully manage anesthesia in captive held in an open hand. If restraint is required, then amphibians. the animal can be gently grasped behind the fore- limbs with an index finger and thumb, with the Preanesthetic Examination examiner’s remaining fingers encircling the rear body (legs and tail). Care should be taken when handling the tail, because tail autonomy can occur. A preanesthetic examination should be performed Because of their natural escape response, anurans on each patient to determine whether an animal is a need to be secured quickly. For most anurans, they suitable candidate for an anesthetic procedure. The can be secured by grasping them in front of their examination should include both a physical evalua- rear legs. For larger specimens, such as the horned tion of the patient and supportive diagnostic tests, frogs (Ceratophrys species), care should be taken to such as bloodwork, to help to characterize the phys- minimize the likelihood of being bitten. The iologic status of the patient. Before performing an amount of restraint required for a caecilian depends examination, however, it is important to consider the different techniques that can be used to safely on the species and general demeanor of the animal. restrain the animal for the examination. Some caecilians can be examined similar to snakes, Amphibians, like fish, require some special con- whereas others need to be chemically immobilized sideration when planning for a procedure that re- because they cannot be secured for an examination. quires restraint. The integument of both of these The hands-on examination of an amphibian groups of animals is an important component to should be done in a thorough but rapid manner. their innate immune system, and damage to the skin The oral cavity should be opened atraumatically. during an examination could compromise the pa- Processed radiograph film or a rubber spatula can be tient. To minimize the likelihood of causing prob- used to gently pry open the mouth of an amphibian. lems, an amphibian should be handled with care. The mucous membranes should be moist and pale Latex or vinyl examination gloves are strongly rec- pink in color. Increased tackiness may be an indica- ommended when handling an amphibian. The tor of dehydration. The integument of the amphib- smooth texture of the gloves will minimize the po- ian should be moist and free of defects. Animals that tential for injury to the amphibian’s integument. appear dry should be kept moistened with distilled The gloves should be premoistened with distilled or or dechlorinated water. Body condition can be used dechlorinated water. Wearing gloves also has a ben- to determine the general health status of the am- efit to the individual restraining the amphibian. phibian. The muscling over the limbs of anurans and Many amphibians can secrete toxins that can be urodelans and the tail of urodelans can be evaluated absorbed through the skin of the handler.5 The to assess body condition. In many amphibians, tran- integument of an amphibian can also be covered sillumination can be done to evaluate the coelomic with a variety of opportunistic pathogens (e.g., cavity/viscera. Positioning a pen light or transillumi- Pseudomonas species, Aeromonas species). The exami- nator on the lateral body wall will enable the exam- nation gloves can serve as a protective barrier against iner to see various organ systems. For most species, both potential toxins and pathogens. respirations can be measured by counting gular The physical examination of an amphibian movements or rib excursions. A Doppler ultrasound should include both a hands-off and hands-on review can be used to measure the heart rate. The probe of the patient. The hands-off examination will en- can be placed on the ventral aspect of the pectoral able the clinician to evaluate the breathing pattern, girdle to obtain the heart rate. general demeanor, and locomotion of the patient. Preanesthetic bloodwork can be used to assess the Animals that are dyspneic or depressed should be physiologic status of an amphibian patient. Unfortu- handled carefully. Amphibians should have a natural nately, many of the animals we work with in captivity escape response when approached. Anesthetic pro- present challenges for collecting samples or obtain- cedures should be delayed in animals displaying ab- ing sufficient volumes of samples for screening. normal behaviors. Blood samples can be collected from the ventral tail For the hands-on examination, the animal may be vein of larger urodelans, the ventral abdominal vein manually restrained. For small or fractious amphib- of anurans and urodelans, the femoral vein of an- ians, chemical restraint may be necessary to com- urans and urodelans, and the sublingual vessels of plete a hands-on examination without injuring the anurans. Cardiocentesis can be done, but can result patient or handler. Amphibians do not generally in cardiac arrest in some species. If only a small 42 Mitchell volume of blood can be collected, then a packed-cell PropofolT (PropoFlo; Abbott Animal Health, Abbott volume or blood smear can be done at a minimum. Park, IL USA), have also been used. This type of data can be used to determine the The water used to make anesthetic water for an general health of the patient and provide insight amphibian should be of high quality. The author into potential complications. For example, if a pa- always prefers to use water from the animal’s enclo- tient is anemic, then recovery from the anesthetic sure for the base of the anesthetic solution. To de- event might be expected to be prolonged and the termine the value of the water, it is important to clinician can plan for it. Plasma chemistries can pro- evaluate the ammonia and nitrite levels, hardness, vide insight into the hydration status of the amphib- alkalinity, and chlorine/chloramine levels. If the wa- ian and general organ function. In the past, there ter is deemed to be of good quality (e.g., no ammo- were often limitations with processing small sample nia, no nitrite, neutral pH, good buffering capacity volumes; however, there is now equipment that can and hardness, and no chlorine or chloramines), it provide complete biochemistry analysis on samples should be used as the base for the anesthetic.