Management of Reptiles

The head of an aggressive snake or a snake of unknown disposition should be identified and restrained before opening the transportation bag to remove the animal. In general, the head of the snake is held behind the occiput using the thumb and middle finger to support the lateral aspects of the cranium. The index finger is placed on top of the head. The other hand is used to support the body. Restraining the snake’s head in this manner supports the cranial-cervical junction, which, having only a single occiput, is prone to dislocation. When dealing with large boids, a second, third, or even fourth handler is required to support the body during the examination. It is usually safer and more convenient to sedate a large, pugnacious snake than to risk injury to the snake, owner, or staff.

Nonvenomous species should be supported using one or two hands, depending on size. Nervous or aggressive snakes can be restrained using plexiglass tubes or sedated before examination. The clinician should attempt to gauge muscle tone, proprioception, and mobility. Systemically ill serpents will often be limp, lack strength, and be less mobile. Head carriage, body posture, cloacal tone, proprioception, skin pinch, withdrawal, and papillary and righting reflexes can be used to assess neurologic function.

The entire integument, particularly the head and ventral scales, should be thoroughly examined for evidence of dysecdysis (poor shedding), trauma, parasitism (especially the common snake mite, Ophionyssus natricis, and ticks), and microbiologic infection. Any recently shed skin should also be examined, if available, for evidence of retained spectacles. Skin tenting and ridges may indicate cachexia (“poverty lines”) or dehydration; ticks and mites may congregate in skin folds, infraorbital pits, nostrils, and corneal rims. The infraorbital pits (where present) and the nostrils should be free from discharges or retained skin. The eyes should be clear, unless ecdysis is imminent. The spectacles covering the eyes should be smooth; any wrinkles usually indicate the presence of a retained spectacle. The spectacle represents the transparent fused eyelids, and therefore the cornea is not normally exposed. The subspectacular fluid drains through a duct to the cranial roof of the maxilla. When blocked, the buildup of fluid causes a subspectacular swelling that often becomes infected. Damage to the underlying cornea can result in panophthalmitis and ocular swelling. Retrobulbar abscessation results in protrusion of a normal-sized globe. Other ocular pathologies can include uveitis, corneal lipidosis, and spectacular foreign bodies, including slivers of wood or other vivarium materials.

Working from cranial to caudal, the head and body are palpated for swellings, wounds, and other abnormalities. The position of any internal anomalies, noted as a distance from the snout and interpreted as a percentage of snout-vent length, enables an assessment of possible organ involvement. Recently fed snakes have a midbody swelling associated with the prey within the stomach; handling such individuals may well lead to regurgitation. Preovulatory follicles, eggs, feces, enlarged organs, and masses may be palpable. The cloaca can be examined using a dedicated otoscope or by digital palpation.

Examination of the oral cavity is often left until last, because many snakes object to such manipulation. However, even before the mouth is opened, the tongue should be seen flicking in and out of the labial notch with regularity. The mouth can be gently opened using a plastic or wooden spatula to permit an assessment of mucous membrane color and the buccal cavity for evidence of mucosal edema, ptyalism, hemorrhage, necrosis, and inspissated exudates. White deposits may indicate uric acid deposition due to visceral gout. The pharynx and glottis should be examined for hemorrhage, foreign bodies, parasites, and discharges. Open-mouth breathing is a reliable indicator of severe respiratory compromise. The patency of the internal nares and the state of the polyphyodontic teeth should be noted.

Lizards vary considerably in size, strength, and temperament; therefore, a variety of handling techniques are required. The tegus and monitors are renowned for their powerful bites, whereas other species, particularly the green iguana, are much more likely to use their claws and tail. The main problem when handling small lizards is restraining them before they flee. The lizard should be transported in a securely tied cloth bag, so that the position of the lizard can be identified and the lizard held before the bag is opened. Large lizards are best restrained with the forelimbs held laterally against their coelom and the hindlimbs held laterally against the tail base. The limbs should never be held over the spine, because fractures and dislocations can occur. Nervous lizards can be wrapped in a towel to aid restraint. Smaller lizards can be restrained around the pectoral girdle, holding the forelimbs against the coelom, although care is required not to impair respiratory movements. A lizard should never be grasped by the tail, because many species can drop the tail (autotomy) in an attempt to evade capture. Restricting the vision of a lizard (eg, a towel placed over the head) is often the simplest way to facilitate handling and examination. A useful restraint technique for iguanid or monitor lizards uses the vasovagal response: gentle digital pressure applied to both orbits causes many lizards to enter a state of stupor for up to 45 min (or until a painful or noisy stimulus is applied). This technique enables the mouth to be gently opened without the need for excessive force. If possible, the lizard should be observed unrestrained to check for neurologic problems. Calm lizards may be permitted to walk around the examination table or on the floor. However, if in any doubt, the lizard should be placed in a large plastic enclosure to prevent escape during observation.

The integument should be examined for parasites (essentially mites and ticks) and trauma due to fighting, mating, and burns. Lizards tend to shed their skin in stages. Classically, dysecdysis and skin retention occurs around the digits and tail, causing ischemic necrosis. Extensive skin folding and tenting may indicate cachexia and dehydration.

The head should be examined for abnormal conformation. The mouth can be opened using a blunt spatula or, in iguanas, by gently applying pressure to the dewlap. The buccal cavity and glottis should be examined thoroughly for evidence of trauma, infection, neoplasia, and edema, especially pharyngeal edema. The internal extent of any rostral abrasions should be evaluated. The nostrils, eyes, and tympanic scales should be clean and free of discharges. The presence of dry, white material around the nostrils of some iguanid lizards is normal, because some species excrete salt through specialized nasal glands. The rostrum should be examined for trauma, often caused by repeated attempts to escape from a poorly designed vivarium or to evade cagemates. The head, body, and limbs should be palpated for masses or swellings, which can be abscesses or metabolic bone disorders. Lizards suffering from severe hypocalcemia and hyperphosphatemia may exhibit periodic tremors and muscle fasciculations. The coelomic body cavity of most lizards can be gently palpated. Food and fecal material within the GI tract, fat bodies, liver, ova, and eggs are usually appreciable. Cystic calculi, fecoliths, enlarged kidneys, impactions, retained eggs or ova, and unusual coelomic masses may also be noted.

The cloaca should be free from fecal staining, with visual and digital examination considered routine. In the green iguana, renomegaly can be appreciated by digital cloacal palpation. The high incidence of dystocia necessitates a need to identify gender during examination. Many species of lizards are sexually dimorphic, although sexing juveniles can be difficult.

Small to medium-sized tortoises are not difficult to handle, although their strength and uncooperative nature can hinder examination. Patiently holding the tortoise with its head down will often persuade a shy individual to protrude the head from the shell. Placing the thumb and middle finger behind the occipital condyles prevents retraction of the head. However, with larger species, it may be physically impossible to prevent a strong individual from pulling free. In such cases, sedation or use of a neuromuscular blocking agent may be necessary. The more aggressive aquatic species should be held at the rear of the carapace. Some species (eg, snapping turtles) have long necks and an extremely powerful bite, necessitating great care. Certain species also have functional hinges at the front and/or back of the plastron, and care should be exercised not to trap a finger when the hinge closes.

Examination of the head should include the nostrils for any discharges and the beak for damage and overgrowth. The eyelids should be open and not obviously distended or inflamed, and the eyes should be clear and bright. Conjunctivitis, corneal ulceration, and opacities are frequent presentations. The tympanic scales should be examined for signs of swelling associated with aural abscessation. Applying steady distractive pressure to the maxilla and mandible can open the mouth, and a mouth gag can be inserted to prevent closure. Aggressive chelonians, generally aquatic species, often threaten by open-mouth displays, which provide a good opportunity to examine the buccal cavity with minimal handling. Mucus membrane coloration is normally pale; hyperemia may be associated with septicemia or toxemia. Icterus is rare but may occur with biliverdinemia due to severe liver disease. Pale deposits within the oral membranes may represent infection or urate tophi associated with visceral gout. The glottis is positioned at the back of the fleshy tongue and may be difficult to visualize; however, it is important to check for any inflammation and glottal discharges consistent with respiratory disease.

The integument should be free of damage. Subcutaneous swellings are usually abscesses. Aquatic species appear more susceptible to superficial and deep mycotic dermatitis, especially around the head, neck, and limbs. The withdrawn limbs can be extended from the shell of small to medium-sized chelonians by applying steady traction. Because the coelomic space within the shell is restricted, gently forcing the hindlimbs into the shell will often lead to partial protrusion of the forelimbs and head, and vice versa. A wedge or mouth gag can be used to prevent complete closure of a hinge. No chelonian will close a hinge on an extended limb. The integument should be examined for parasites (particularly ticks and flies), dysecdysis, trauma, and infection that may arise due to predator attacks. Aggressive conflicts and courting trauma must also be considered in the communal environment. Limb fractures are less common in chelonians than in other reptiles, but when they do occur they are often associated with rough handling and secondary nutritional hyperparathyroidism. Focal subcutaneous swellings are usually abscesses, but grossly swollen joints or limbs are more often cases of fracture, osteomyelitis, or septic arthritis.

The prefemoral fossae should be palpated with the chelonian held head-up. Gently rocking the animal may enable palpation of eggs, cystic calculi, or other coelomic masses. The shell should be examined for hardness, poor conformation, trauma, or infection. Soft, poorly mineralized shells are usually a result of secondary nutritional hyperparathyroidism resulting from dietary deficiencies of calcium, excess phosphorus, or a lack of full-spectrum lighting. Pyramiding of the shell appears to be more associated with inappropriate humidity than dietary imbalances. Shell infection may present as loosening and softening of the scutes with erythema, petechiae, purulent or caseous discharges, and a foul odor.

Prolapses through the vent are obvious, but it is necessary to determine the structure(s) involved. Prolapses may include cloacal tissue, shell gland, colon, bladder, or phallus. Internal examination using digital palpation and an endoscope is recommended.

All reptiles should be hospitalized and maintained at their preferred optimal temperature zone at all times to minimize physiologic disturbance, facilitate recovery, and maintain immunocompetence. Although hypothermia will reduce movement, it does not provide analgesia and is therefore unacceptable as a means of anesthesia on welfare grounds. It can also dramatically affect the pharmacokinetics of any drugs administered and greatly prolong recovery.

A full clinical examination should be performed and the animal accurately weighed, although this may not be practical or possible in some cases. The hydration status of all reptiles should be assessed, especially if debilitated or post-hibernation. For elective procedures (eg, neutering), underweight, dehydrated, or debilitated animals should be nursed for days, weeks, or months until their condition improves. For nonelective surgery, dehydration should be corrected before anesthesia. Even the most moribund egg-bound reptile will usually benefit from stabilization for 24–48 hr before surgery is performed. Reptiles that have not been stabilized before surgery tend to succumb intra- or postoperatively. Although oral fluids are least invasive to administer and provide the most physiologically normal method of rehydration, they are sufficient only for mildly dehydrated animals and are contraindicated immediately before surgery because of the risks associated with regurgitation. Intracoelomic fluids are more suitable, but uptake can take many hours and their use is problematic if coeliotomy or coelioscopy is planned. For dehydrated surgical candidates, IV or intraosseous fluid therapy should be administered before, during, and after surgery as necessary.

Reptiles should be fasted before all elective surgery to avoid the compression of lung(s) associated with large meals and potential regurgitation. Fasting depends on the feeding regimen of the reptile, but in general one feeding cycle should be skipped before surgery. Premedication with sedatives such as acepromazine and atropine is generally rare in reptiles, although midazolam has been advocated in large chelonians. However, presurgical administration of analgesics should be considered routine (see Table: Analgesics, Sedatives, and Anesthetics Used in Reptiles).

IV or intraosseous propofol provides a rapid, controlled mode of induction. It is relatively nontoxic, and there is reduced risk of thrombophlebitis if it is injected perivascularly. This is of particular concern, because IV access may be relatively difficult, especially in active animals undergoing elective procedures. Alfaxalone has been licensed in the USA; it is an excellent IV induction agent and is also effective when used IM.

If IV access is impractical or dangerous to attempt, IM agents can be used to induce sufficient chemical restraint for intubation. For IM injections in lizards and chelonians, the forelimb muscles are preferred, whereas for snakes, the epaxial muscles are used. An IM combination of ketamine, medetomidine (or dexmedetomidine), and morphine or hydromorphone has proved effective for a variety of chelonians; this can be readily reversed using atipamezole and, if necessary, naloxone or naltrexone.

Squamates can also be induced by inhalation agents in an induction chamber or by mask. However, breath holding tends to occur in turtles and crocodilians, which can respire anaerobically for prolonged periods. Induction may take 10–30 min in cooperative lizards and snakes. Intubation of conscious patients has been suggested after local lidocaine spray, but the adverse effects of increased stress and catecholamine release should always be considered. There is also the potential danger of being bitten.

Isoflurane or sevoflurane are the agents of choice for maintenance of anesthesia. These volatile inhalation agents have faster modes of action, are more controllable, and facilitate faster recoveries than most alternatives. Furthermore, their lack of reliance on hepatic metabolism or renal excretion reduces the anesthetic risk to debilitated reptiles or those with questionable renal or hepatic function.

Intubation of reptiles is relatively simple. Small-gauge endotracheal tubes or catheters are easily inserted through the glottis immediately caudal to the tongue; this may be aided by forcing the tongue up and forward by pressing a finger into the intermandibular space from under the jaw. The reptilian glottis is actively dilated, and therefore its movement will often be abolished in anesthetized animals; a guiding stylet can be useful to facilitate endotracheal tube placement. The bifurcation of the trachea may be far craniad in some chelonians, and gaseous exchange has also been reported within the tracheal lung of some snakes; care should be taken to use a short endotracheal tube that is securely taped in position.

Noncrocodilian reptiles lack a diaphragm; skeletal intercostal muscles (Squamata) or limb movements (Chelonia) control breathing. The action of these muscles is abolished at a surgical plane of anesthesia, and intermittent positive-pressure ventilation is required. Ventilation rates should initially mirror preanesthesia evaluations and then be adjusted to maintain end-tidal capnography readings of 15–25 mmHg. Electrical ventilators enable precise control of ventilation rates and pressures.

Monitoring anesthesia in reptiles differs considerably from doing so in mammals. Palpebral and corneal reflexes are reliable in those species in which they can be elicited (ie, all chelonians, all crocodilians, most lizards, but no snakes). However, corneal reflexes are abolished at toxic doses, and pupillary diameter may bear little relation to the depth of anesthesia (unless fixed and dilated, which indicates excessive anesthetic depth or brain anoxia and death). Jaw tone and withdrawal reflexes (tongue, limb, or tail) are abolished only at a surgical plane of anesthesia. This also correlates with full loss of the righting reflex, loss of spontaneous movement, and complete muscle relaxation.

Heart rate may be monitored by auscultation or by visualization or palpation of the heart beat in most snakes and some lizards. Pulse oximetry, using either an esophageal or cloacal reflectance probe, is useful to monitor pulse rate and strength. Although the blood oxygen saturation (SpO₂) readings are often low and have not been validated for reptiles, monitoring the trend in SpO₂ is often helpful. Doppler ultrasonography can also be used over peripheral arteries or the heart. Blood gas estimations are often affected by intracardiac or pulmonary shunts, especially in aquatic species. However, end-tidal capnography has proved effective.

Toward the end of surgery, the anesthetic gas should be discontinued while maintaining ventilation for another 5–10 min to facilitate excretion. At this point, oxygen should be discontinued in favor of room air delivered by bag-valve mask to encourage spontaneous respiration.

Once it is breathing spontaneously, the reptile can be returned to an incubator or vivarium to fully recover. Continued monitoring is essential until righting reflexes return and the animal is ambulatory. Additional analgesia, fluid, and nutritional support should be provided as indicated.

Several anatomic differences make it difficult to obtain quality radiographs in reptiles. The relatively small size of most pet reptiles and the lack of diffuse body fat often produce images of poor contrast. Thick, highly keratinized scales, osteoderms, or shells can severely hinder the x-ray beam, necessitating greater power and a subsequent loss of fine soft-tissue detail.

Despite these difficulties, most high-capacity units can be set to produce quality radiographs of reptiles. High-detailed screen/film combinations (eg, mammography film) are essential to obtain sufficient detail and contrast, especially in smaller animals. Various agents can be used to improve contrast. Barium sulfate (30%) can be used for GI studies. Water-soluble iodine compounds such as iohexol can be used for GI, urogenital, and IV techniques. The injection of air into the coelom of a lizard can greatly improve the appreciation of preovulatory follicles.

A useful and often underrated technique, ultrasonography has gained popularity as a diagnostic technique for reptiles. It is particularly useful for examining tissue parenchyma, guiding biopsy needles, and, with color flow Doppler, investigating cardiac disease. Unfortunately, the equipment tends to be expensive, and several probes with small footprints are required, given the variation in reptile size and ultrasound applications. Ultrasound waves cannot penetrate through mineralized tissue or air and, therefore, ultrasonography has obvious limitations to investigate respiratory and GI diseases.

The giant species require a 5-MHz probe, whereas a 7.5-MHz probe suffices for most reptiles. When examining very small specimens (or for ultrasonography of eyes), a 10–20 MHz probe is more appropriate. Good contact and imaging generally require copious quantities of gel or a water bath. It is helpful to maintain the animal in a normal position or, failing that, at least appreciate the complications associated with organ displacement. Ultrasonography can be a useful adjunct to radiography, especially to assess the reproductive tract (evaluating ovarian activity and distinguishing between pre- and postovulatory egg stasis), liver and gallbladder, urinary system, soft-tissue masses, and heart. Ultrasonography has been used to guide liver biopsy, although iatrogenic trauma has been reported in snakes.

CT offers excellent, high-resolution, detailed images. Potentially, it would be the diagnostic imaging technique of choice for the respiratory system and skeleton of reptiles. MRI produces primarily high-detailed images of soft-tissue structures and is useful to diagnose neurologic, hepatic, renal, and reproductive diseases in reptiles. Disadvantages of these techniques are the need for general anesthesia to completely eliminate motion, equipment availability, and cost.

Endoscopy has proved to be a most useful diagnostic tool in reptile medicine, and given the small and delicate nature of many species, continued development of minimally invasive techniques is likely. Flexible endoscopes are useful for respiratory endoscopy in snakes or GI endoscopy in many species. The main disadvantage of the flexible, fiberoptic endoscope is the poorer image quality than for those obtained using rigid scopes of a similar diameter. However, the continued development of smaller videoscopes looks likely to redefine flexible endoscopy in reptiles. The compact body size of most pet reptiles, coupled with their coelomic body design, makes rigid endoscopy useful in many situations. Although equipment must be matched to size of the reptile, in general the 1.9-mm and 2.7-mm telescope and sheath systems work well for most pet species, enabling gas insufflation, fluid irrigation, and biopsy capability.

Insufflation is essential to provide the lens-organ distance required for visualization. For GI endoscopy, air and/or saline is used; for coelioscopy, medical grade CO₂ or saline is preferred. Coelomic pressures seldom need to be >5 mmHg. When performing endoscopy in small neonates or within a hollow viscus (eg, bladder, oviduct, cloaca, stomach), warmed sterile saline irrigation often provides better clarity than gas insufflation.

General anesthesia is recommended for all endoscopy procedures. Certain examinations (eg, buccal cavity and cloaca) may be possible in a conscious or sedated animal using a mouth gag or other appropriate restraint, but complete immobilization is preferred to avoid risking damage to patient, staff, or equipment. Anesthesia is mandatory for coelioscopy.

Venipuncture is generally a blind technique in reptiles. Up to 0.5 mL/100 g may be safely collected from healthy reptiles, less in debilitated animals. There is a relative lack of hematologic or biochemical data for most reptiles. In addition, blood values can vary dramatically with species, environment, nutrition, age, breeding, and hibernation. Given this variability, published ranges may be of limited value. More reliance should be placed on establishing an individual’s observed range and using serial sampling to monitor the progress of hematologic and biochemical changes. The use of a toenail clip to obtain blood may result in fecal or urate contamination, increased tissue enzymes, and hemogram and electrolyte changes due to the peripheral nature of the sample and the crushing artifact of collection. Of even greater concern are the ethical and welfare issues associated with toenail clipping.

The two common sites for venipuncture in snakes are the caudal vein and the heart. The caudal vein is accessed caudal to the cloaca, between 25% and 50% down the tail, and avoiding the paired hemipenes of males. In lizards, the most clinically useful vessel is the ventral midline caudal vein, best accessed 20%–80% down the tail. The most clinically useful vessels in chelonians appear to be the jugulars, subcarapacial sinus, and dorsal coccygeal veins. The left and right jugular veins are preferred because of the reduced risk of lymphatic contamination.

A detailed necropsy should be undertaken whenever possible, because it often provides a definitive diagnosis. When managing a disease outbreak in a population, elective euthanasia and necropsy of one or more individuals is often the most efficient and cost-effective means of diagnosis. Fresh necropsies can provide organ biopsies, blood, and other bodily fluids for laboratory examination. The submission of microbiology samples, especially bacteriology, from reptiles that have died and remained within a heated enclosure must, however, be interpreted with caution.

Numerous pharmacokinetic studies have been published for reptiles, and these should be considered the most reliable source for information on drug dosages. When species-specific information is not available, it is possible to extrapolate from closely related species. If there are no pharmacokinetic data or reliable clinical experience for a particular species, it may be necessary to extrapolate pharmacokinetic data from other animals. Allometric scaling calculates the drug dose and dosing frequency using metabolic rate rather than body weight. The basic allometric equations are shown below, in which W = body weight (kg) and K = energy constant, which is 10 for reptiles. These equations can be used to calculate a dose and dose frequency for a species for which no data are available, by using pharmacokinetic data from a known species (control), whether another reptile or mammal or bird:

Minimum energy cost = K (W^0.75)

Specific minimum energy cost = K (W^-0.25)

Many bacterial infections in reptiles are caused by gram-negative bacteria, particularly Pseudomonas, Aeromonas, Citrobacter, Klebsiella, and Proteus spp. Bacterial resistance to many commonly used antibacterials is seen, and many gram-negative bacteria can have unexpected sensitivity to particular antibacterials; therefore, sampling for Gram stain, cytology, culture, and sensitivity testing should be done before starting therapy. Antibacterial therapy must usually be given while awaiting the results of bacterial sensitivity tests. In these circumstances, amikacin, ceftazidime, and enrofloxacin or ciprofloxacin are often preferred (see Table: Antimicrobial Drugs Used in Reptiles). In severe infections, amikacin may be combined with ampicillin or amoxicillin for respiratory tract infections or with ceftazidime for generalized or systemic infections. Chloramphenicol in combination with neomycin may be given for GI infections. Penicillin, metronidazole, lincomycin, or clindamycin can be used for anaerobic infections.

Fungal and yeast infections commonly occur in reptiles. GI and skin mycoses are particularly common in reptiles maintained on inappropriately longterm broad-spectrum antibacterials. Cutaneous mycoses can often be treated by debridement and topical application of antifungals. GI infections can be treated with nystatin, whereas systemic infections may require itraconazole or fluconazole. In cases of pulmonary mycoses, antifungal medication may be given by nebulization or intratracheal or intrapulmonary injection.

Herpesviruses can cause severe morbidity and mortality in chelonians. Acyclovir has been used with some success during the early stages.

Parasiticides used commonly in reptiles are listed in Parasiticides Used in Reptiles. Parasiticide overdosage may lead to drug toxicity, which may be seen as neurologic signs, including seizures. Ivermectin is contraindicated in chelonians, and adverse reactions have been reported in some iguanid lizards, skinks, and indigo snakes. Milbemycin has been successfully used in box tortoises and terrapins, but it is recommended that ivermectins and milbemycins be avoided in all chelonians because safer alternatives are available. Permethrin is licensed for use in reptiles and appears safe and effective against mites and ticks.

Dosages for medications used for a variety of other disorders of reptiles are listed in Miscellaneous Drugs for Reptiles.

Dehydration in reptiles is usually associated with prolonged anorexia and water loss, deprivation, or an inability to drink, rather than mixed electrolyte losses through frequent vomiting or diarrhea. Water balance in reptiles differs from that in mammals, because, per unit body weight, reptiles have a higher percentage of total body water (63.0%–74.4%) and a higher percentage of intracellular water (45.8%–58.0%). These values appear to be highest in freshwater species, lower in terrestrial reptiles, and lowest in marine reptiles, with the concentration of isotonic saline in nonmarine reptiles being 0.8%. This has led to the conclusion that normal 0.9% saline may be too concentrated for most reptiles. Balanced crystalloid fluids containing dextrose (260–290 mOsm/L) appear to be effective. As a general guide, maintenance requirements are about 5–15 mL/kg/day, and rehydration should proceed at 35–40 mL/kg/day, although in cases of shock, rates of 3–5 mL/kg/hr can be used for several hours.

In many instances, simply permitting a reptile to bathe in shallow, warm water within a vivarium maintained at the species-specific preferred optimal temperature zone will promote drinking. Such a method is acceptable when reptiles are able and willing to drink voluntarily. However, in many cases oral fluids must be delivered via a stomach tube. For oral rehydration, mammalian electrolyte solutions can be used but are best diluted by a further 10%–15% to produce a slightly hypotonic solution. Significant amounts of water may also be absorbed via the cloaca when chelonians (and possibly other species) bathe. Oral fluid therapy works well to provide maintenance requirements, rehydrate mildly dehydrated reptiles, and as a vehicle to give oral medications and food. For alert and active reptiles, this method is preferred because it facilitates GI activity, and fluids are rapidly absorbed when the reptile is maintained at correct temperatures. Repeated stomach tubing is stressful and can be difficult in strong chelonians; therefore, esophagostomy tubes are recommended for longterm oral therapy. Small fluid volumes can be given SC, but in moderate to severe cases, intracoelomic, IV, or intraosseous routes are favored.

Intracoelomic administration of fluids is faster, less stressful, and allows delivery of a larger volume than stomach tubing. Large volumes of intracoelomic fluid could compromise lung function and may be slowly absorbed; however, IV catheterization is not easy, and cut-down procedures are often required. In emergencies with larger snakes, it is possible to place an intracardiac catheter. Fluid infusion is best controlled by a syringe driver or infusion pump. If such devices are not available, the total daily fluid volume can be divided into three or four bolus injections, each given slowly over 10–20 min. IV catheters can usually be left in place for up to 72 hr; intracardiac catheters up to 24 hr. Intraosseous infusion is an easier technique in lizards, small crocodilians, and chelonians. The needle is directed into the medullary cavity of a long bone, and aspiration of marrow or radiography can verify correct positioning. Great care must be exercised when dealing with osteodystrophic lizards to avoid limb fractures. Infusion rates for IV and intraosseous administration are similar. As a general guide, 0.8–1.2 mL/kg/hr is suitable for rehydration purposes, but in cases of severe dehydration or shock or during surgery, 3–5 mL/kg/hr can be given for 2–3 hr.

Colloids are less frequently used in reptiles because much of the water loss is from the intracellular space rather than plasma, but they can be used in cases of acute hemorrhage. If severe hemorrhage occurs (ie, PCV <5%), whole blood may be given by IV and intraosseous routes. Cross-matching does not appear necessary, at least for a single transfusion. Ideally the donor and recipient are of the same species.