Surgery of Exotic Animals. Группа авторов
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Temperature should be kept within the preferred optimal temperature zone (POTZ) of the species throughout the procedure. Like reptiles, amphibians are poikilothermic, but they rarely need supplemental heat due to their lower POTZ. It is better to keep a low room temperature and to place sealed ice packs in the water to cool it.
When handling amphibians with toxin‐producing glands, the surgeon may need to wear protective eye wear as Bufo spp. can expel toxic parotidian secretions into the air (Wright 2006). The choice of gloves is important as many compounds are absorbed through amphibian skin. Gloves with talcum powder should be avoided (Wright 2006). Latex is toxic to tadpoles of some amphibian species, including common frogs (Rana temporaria) and African clawed frogs (Xenopus laevis) and may result in acute mortalities (Sobotka and Rahwan 1994; Gutleb et al. 2001). Nitrile gloves have been shown to kill chytrid fungi zoospores that can infect amphibian patients, while polyethylene gloves did not (Mendez et al. 2008). Powderless vinyl gloves are preferred by many practitioners (Norton et al. 2014).
Figure 6.1 A wound on the lateral aspect of the tarsus in a laboratory African clawed frog (Xenopus laevis) showing granulation tissue and formation of scar tissue around the outer edge of the lesion.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Like in other animals, perioperative antibiotics (Wright and Whitaker 2001a) and antinociception (Weber 2011) have been advocated. Antibiotics with a spectrum oriented toward Gram‐negative bacteria are preferred given the predominance of Gram‐negative bacteria in amphibian flora (Roth et al. 2013). Depending on the amphibian species, intravenous injections may be performed using the femoral vein, musculocutaneous vein (Sancho et al. 2012), popliteal plexus, ventral abdominal vein, or lingual venous plexus in frogs larger than 25 g (Whitaker and Wright 2001) (Figure 6.2). Alternatively, preoperative antibiotics may be administered topically (ciprofloxacin 10 mg/kg; Wright and Whitaker 2001b), subcutaneously (enrofloxacin 10 mg/kg; Wright and Whitaker 2001b) or intramuscularly (amikacin 5 mg/kg: Felt et al. 2013), or into the dorsal lymphatic sacs that are paired sacs accessible dorsally on each side of the urostyle.
Amphibian opioid receptors are similar to those of mammals (Newman et al. 2002). Amphibians appear to require higher doses of opioids to produce antinociception when compared to rodents (Koeller 2009). Opioid dosages up to hundred times the minimal dose have been reported for northern leopard frogs (Stevens 2011). Recommended opioid dosages need to be refined in amphibians. The reader is referred to review chapters about amphibian anesthesia regarding monitoring and choice of anesthetic agents (Mitchell 2009; Braitman and Stetter 2014; O'Rourke and Jenkins 2014).
Figure 6.2 Possible intravenous injection sites in amphibians.
Source: Delphine Grosset, Visual Conception Communication Creator.
Anurans may be more resistant to the effects of hemorrhage than some mammals (Chai 2015a) due to lymph regulation and a powerful baroreceptor reflex (Hedrick et al. 2015) as long as they are maintained at their POTZ of the species (Zena et al. 2015). Hemostasis can be accomplished using techniques similar to those employed in mammals, and some authors have also recommended using cyanoacrylate tissue adhesive as an hemostatic agent for internal organs (Wright and Whitaker 2001a), but no study has investigated adverse effects associated with this technique.
Patients with skin sutures may be kept isolated in a tank with a nonabrasive substrate such as a moist plastic lining. In aquatic species, water quality should be carefully monitored during the postoperative period, especially in patients with incisional secretions that may increase nitrogenous wastes in the tank water. Skin sutures may be removed after about three weeks (Green 2010). Similar to other patients, nutritional support and postoperative antinociceptive drugs may be needed depending on the procedure performed (Gentz 2007).
Wound Healing
Epithelialization, wound contraction, and tissue remodeling takes place in amphibians similar to in mammals (Poll 2009). In immature amphibians, skin healing involves contraction and regeneration of the skin, while postmetamorphic amphibians will form scar tissue devoid of dermal mucous and granular glands (Yannas et al. 1996).
During the inflammatory phase of wound healing, wet‐to‐dry bandages are contraindicated in amphibians because they may result in desiccation of the tissue surrounding the wound (Poll 2009). During the proliferative phase, becaplermin (Regranex®, 0.01% gel, Ortho‐McNeil Pharmaceutical Inc., Raritan, NJ, USA), recombinant human platelet‐derived growth factor has been suggested to accelerate healing (Walker and Whitaker 2003; Poll 2009). Apply the gel to the wound for 60 seconds every three weeks (Fleming et al. 2008). Before applying the gel, irrigate the wound with saline to loosen external debris, necrotic skin and exudates. Gently debride the area until a small amount of hemorrhage is observed and then rinse the wound again before applying a thin layer of gel (Poll 2009). After a contact time of 60–120 seconds, rinse the gel off or leave it on the wound. The use of hydrogel has also been recommended to accelerate wound granulation (Poll 2009).
Skin Surgery
There are a number of indications for skin biopsy. Perform a local anesthesia block with lidocaine 2 mg/kg and obtain the biopsy with