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CRITICAL CARE NUTRITION AND FLUID THERAPY IN REPTILES

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Abstract

Gibbons PM. Critical care nutrition and fluid therapy in reptiles. Proceedings of the 15th Annual International Veterinary Emergency & Critical Care Symposium. September 9-13, 2009. Chicago, Illinois. Pp. 91-94.
CRITICAL CARE NUTRITION AND FLUID THERAPY IN REPTILES
Paul M. Gibbons, DVM, MS, Dipl. ABVP (Avian)
Animal Emergency Center & Specialty Services, Milwaukee, WI
Start every reptile case by identifying the species and providing an appropriate hospital environment. It is
not sufficient to call the patient a “turtle” or a “lizard” because the needs of each species are unique. For example,
the hospital care for an African spurred tortoise differs substantially from that of an ornate wood turtle, Western box
turtle, and red-eared slider turtle. Take a few minutes to learn about the particular species’ natural history including
nutritional and habitat needs. There is no singular reference for species identification, but animal caretakers usually
know a common name that can be used to begin an Internet search for information about the species. Bartlett PP,
Griswold B, and Bartlett RD, Reptiles, Amphibians, and Invertebrates: An Identification and Care Guide
1
is one
handy text to keep on the shelf for quick reference. After the species is identified without question, then Internet
sources of husbandry information (e.g., www.anapsid.org and www.chelonia.org) may be consulted. The hospital
environment must meet temperature, humidity, lighting, substrate, and water requirements. Husbandry methods
must be modified for patient status. For example, a water turtle with a fracture of the carapace should not be
submerged until after the fracture is sealed, because water could enter the body cavity and lead to coelomitis.
After the species is identified and an appropriate hospital environment has been provided, gradually warm
the patient to within its optimal body temperature range before initiating further therapy. As a general guideline for
most of the common pet species of reptiles, therapy can begin when the cloacal temperature is between 26°C and
30°C. Raise the body temperature over the course of several hours using radiant heat such as an incandescent lamp
or incubator for terrestrial or arboreal species, or a shallow water bath for aquatic species. Support the head to
prevent drowning.
Then begin the process of rehydrating patients that are dehydrated and/or volume depleted. Diagnosis and
treatment of the primary (i.e., most diagnostic) problem may not need to begin for many hours or days, which may
be long after the patient has left the emergency and critical care setting.
Finally, do not feed a dehydrated reptile. Nutritional support is rarely needed in the initial 24 hours of care
for reptiles that are presented in serious to critical condition.
Hydration and perfusion status
Assess hydration using eyelid turgor, position of the eyes (sunken/bright), mucous membrane moisture or
tackiness, tenaciousness of saliva (does it form durable strands or not), skin turgor/dermal elasticity (thickness and
durability of skin tent or folds), abdominal doughiness, PCV, TP (e.g., total protein by refractometer), BUN, plasma
sodium, and plasma chloride. Rapid weight loss (in less than a few weeks) can be a sign of fluid loss. Reptile urine
is normally hyposthenuric and urine specific gravity does not rise above isosmotic with plasma (~1.008–1.012)
during dehydration. Severely dehydrated reptiles (≥10%) may have any combination of the following signs: saliva
that forms durable strands, durable skin wrinkles, sunken eyes, doughy abdomen, PCV >40%, refractometer TP >8
g/dL, plasma sodium >165–180 mEq/L (depending upon species), and plasma chloride >120 mEq/L.
Perfusion is generally difficult to estimate. Anuria will occur with decreased glomerular filtration rate, but
urination patterns are not easy to recognize and reptile caretakers may not be able to differentiate urination from
defecation. Arterial blood flow can sometimes be detected with a Doppler probe in extremities including the limbs
and tail, but flow cannot always be detected, even in well perfused reptiles. Non-invasive blood pressure can
sometimes be measured in reptile species using a sphygmomanometer and Doppler probe, but readings are not
consistent and are confusing. Blood pressure measurements with a non-invasive oscillometric monitor can
sometimes be useful in the hands of veterinarians and technicians who are highly experienced with reptiles, but
should not be relied upon by novices.
2,3
The Doppler probe can be used to directly measure heart rate, but rate is
closely related to body temperature, so the patient should be warmed to the optimal temperature range before
interpreting the heart rate. Normal, resting, thermally stable heart rate can be roughly estimated with this formula:
heart rate=33.4(weight in kilograms
-0.25
), which calculates out to approximately 25 to 80 beats per minute.
Nutritional status and body condition score
Body condition can be scored on a scale of 1 to 9 (1=emaciation; 5=excellent condition; 9=morbid obesity).
Estimate condition in lizards and snakes by palpating the muscling over pelvis and tail; characterizing abdominal
distension; and palpating abdominal fat bodies. Cachexia, like severe dehydration, can lead to sunken eyes and loss
of skin elasticity. Estimate condition of chelonians by subjective assessment of density: they should have reasonable
heft for the size. Formulae to calculate chelonian body condition based on weight and size have been reported, but
the information resulting from these calculations has not proven to be clinically useful.
4
Obese turtles and tortoises
may have fat bodies visible beneath bulging, unpigmented skin, whereas markedly underweight individuals may
have obvious tendons on the limbs with muscle wasting. Larger reptiles generally eat less frequently than smaller
reptiles. Carnivores generally eat less frequently than omnivores and herbivores. In general, most reptiles can
withstand weeks to months of anorexia, so body condition score is more useful than history of appetite to judge
nutritional status. Keep in mind that blood glucose concentration less than 20 mg/dl can be normal for some
reptiles, so it is important to check a reference for normal values.
5
Methods of fluid administration
Fluids may be administered 1) per os, 2) via oro-gastric intubation, 2) subcutaneously, 3) intracoelomically,
4) intravenously, or 5) intraosseously. If a patient will not drink voluntarily when offered water, then the author
prefers subcutaneous fluid administration over intracoelomic for several reasons. First, fluids are absorbed rapidly
from the subcutaneous space in individuals with normal oncotic pressure and appropriate body temperature.
Secondly, when fluids are placed into the subcutaneous space, it is possible to visually identify when they have not
been absorbed because pitting edema will occur, whereas ultrasound or other imaging technique is required to
monitor the absorption of fluids placed into the coelomic cavity. Third, the subcutaneous location avoids the risk of
accidental placement into internal organs because the exact location and size of the organs is not predictable among
species, between the sexes, and even in the same individual at different times. Accidental fluid administration into
lungs, gastrointestinal tract, reproductive tract, urinary bladder, or other organ is common with intracoelomic
administration and the person who administered the fluids is not aware of the mistake unless exploratory surgery or
necropsy is performed. Some authors recommend avoiding subcutaneous fluids in snakes because in some animals
the subcutaneous space does not readily accept large volumes; this is, however, species specific and small volumes
can be administered in multiple subcutaneous locations if necessary.
Many reptiles voluntarily drink when placed into a shallow, tepid (27–30°C) water bath for 10 min. Ensure
the patient is strong enough to avoid drowning and monitor the water bath temperature with a thermometer. There is
no evidence to support the hypothesis that reptiles might “drink” via the cloaca, though some authors have
misreported the results of studies on the hypothesis.
6-8
Orogastric intubation is used commonly in patients that
require feeding, but is usually not attempted for fluid therapy alone because it is more stressful than other methods.
Administer subcutaneous fluids under the skin that overlies the scapula in lizards or the epaxial muscles of the body
in snakes and lizards. Administer subcutaneous fluids under the skin overlying the humerus or femur in turtles and
tortoises. Catheterize the jugular vein in chelonians; a cut-down may be necessary to identify and secure the vein.
Use heavy sedation if necessary and local anesthesia; secure the catheter in place with skin sutures. Catheterize the
ventral caudal vein in large lizards. Jugular catheterization is possible in some lizards, though it requires surgical
dissection in species with a short, muscular neck. Use local and/or general anesthesia and sterile technique to place
intraosseous catheters distoproximally into the femur or proximodistally into the tibia of lizards or chelonians. In
snakes, perform a ventrolateral surgical approach to expose the jugular vein within the cranial 1/5
th
of the coelomic
cavity under general anesthesia. A catheter can be placed into the cardiac ventricle of snakes without surgery.
Other vascular access sites are available, but they are generally not as useful as those recommended here.
Methods of nutritional support
Feed only well-hydrated reptiles with reasonably good mentation; never feed a dehydrated reptile. Start by
offering an array of species-appropriate food items presented in a manner that is appropriate for the species. Then
try assisted feeding either by holding food items in front of the reptile’s nose (with tongs or forceps) or by placing
small volumes of feed paste into the mouth with a rubber-tipped syringe. If the patient refuses to eat for several
days after it is well hydrated, then consider orogastric tube feeding. No clinical trial of total parenteral nutrition has
been reported, though glucose can safely be added to parenteral fluids for short-term support.
Long-term nutritional support can be provided via esophagostomy tube in anorectic chelonians, and may be
attempted in lizards and snakes with oral or facial lesions that preclude use of the mouth. Use chemical restraint in
all but the most obtunded patients, and always use local anesthesia. Pre-measure the tube to the midpoint of the
body in lizards and chelonians or to ½ the distance from the snout to the vent in snakes. Perform percutaneous
esophagotomy with a scalpel blade over the tips of hemostats placed from the mouth approximately ½ the way
between the head and the thoracic inlet (about twice the length of the head in snakes). Avoid incising the jugular
vein; use ultrasound to identify the major vessels if needed. Ensure the tube is within the lumen of the esophagus by
passing it orally before redirecting it aborally back into the distal esophagus. Secure the tube to the skin with sutures
using tape butterfly or “finger trap” pattern on tube.
Fluid therapy: when, what, and how much
Many of the reptiles that are presented for emergency care are chronically dehydrated and volume depleted.
These patients require fluid therapy and parenteral routes should be used in those with signs of moderate to severe
signs. Intravenous or intraosseous routes are reserved for cases of acute volume depletion or those that need colloids
or glucose. Calculate maintenance (10 to 20 ml/kg/day) plus deficit (relative acute body weight loss); replace losses
over 72 to 96 hours because rapid expansion of the intravascular space and hydration of the interstitial space are not
necessarily followed by rapid rehydration of the intracellular space.
9,10
Warm fluids to the optimal body temperature
and provide approximately 25 to 30 ml/kg/day; avoid rates in excess of 40 ml/kg/day. Some authors recommend
directed free water replacement in reptiles with plasma sodium >160 mEq/L,
9
but this hypothesis has not been
tested, and clinical success with mixed electrolyte solutions indicates this is probably unnecessary. Use a metered
pump to deliver intra-osseous or intravenous fluids; use a burette to prevent accidental delivery of excess fluids.
Select the type of fluids using data from the minimum objective database (e.g., blood albumin, electrolytes,
glucose) and standard pathophysiological rationale. Parenteral crystalloid options include Plasma-Lyte A (294
mOsmol/L; Baxter Healthcare, Deerfield, IL), Normosol-R (294 mOsmol/L; Abbott Laboratories, North Chicago,
IL), lactated Ringer’s solution (273 mOsmol/L; LRS; Abbott Laboratories), 5% dextrose (253 mOsmol/L; D
5
W),
0.9% NaCl (308 mOsmol/L), and combinations. Some authors recommend diluting crystalloids with dextrose in
water to more closely approximate “normal” reptile blood osmolality because it has been postulated that
commercially available crystalloids might be hypertonic and therefore detrimental.
6
This hypothesis is not clinically
useful because reptiles are adapted to tolerate severe dehydration and widely ranging plasma osmolality (e.g., 250
400 mOsm/L) and electrolyte concentrations.
7,11
Dilution of crystalloids is not encouraged by the author, though
half-strength LRS/D
2.5
W (263 mOsmol/L) or 0.45% NaCl/D
2.5
W (280 mOsmol/L) would be reasonable during the
initial stages of therapy for moderately hyperkalemic (K
+
=8.0-10.0), severely dehydrated reptile patients. Some
authors also postulae that lactated crystalloids may be detrimental, but reptiles tolerate high blood lactate levels
(e.g., 20 mmol/L)
12
so the amount of lactate in commercially available crystalloids is not clinically relevant.
Natural colloids include whole blood, plasma, concentrated albumin, and polymerized bovine hemoglobin
(Oxyglobin, Biopure, Cambridge, MA, USA); synthetic colloids include hydroxyethyl starches (hetastarch), and
dextrans. Colloids (3 to 5 ml/kg bolus) should be used in addition to crystalloids in reptiles with hypoalbuminemia,
increased capillary permeability, hypovolemic perfusion deficits, or conditions with less tolerance for large volume
infusion (e.g., brain and pulmonary disease and cardiac insufficiency).
9
Homologous (same species) whole blood or
plasma transfusion is reasonable in cases of severe acute blood loss anemia or hypoalbuminemia. The safety and
efficacy of heterologous (different species) transfusions have not been reported. Although a transfusion may not
approximate a return to normal levels of plasma constituents such as coagulation proteins and albumin, even a small
amount may be sufficient to rescue a critical patient or provide sufficient protection for a surgical procedure.
The goal of fluid therapy is to restore normal tissue perfusion and cellular fluid/electrolyte balance.
Monitor for improvement in mucus membrane moisture and color, eyelid and skin turgidity, eye position, and
behavior (e.g., activity & appetite). Heart rate at a stable body temperature is a useful parameter (rate will slow with
improving pressure), but non-invasive, indirect blood pressure measurements should not be relied upon to make
decisions about fluid therapy. Measure PCV, total protein by refractometer, BUN, and electrolytes over time; adjust
therapy accordingly. Body weight is very useful because it can be used to determine whether estimated deficits have
been replaced (i.e., 10% dehydrated patient should gain 10% of body weight with fluid therapy). Urination is an
indirect measure of hydration and renal perfusion. Monitor urine output, but consider behavioral influences on
urination patterns. Adequately hydrated chelonians should void urine approximately every other day and the
volume is reported to be approximately 0.5 to 3.0% of body weight per day.
13
Urinating less than once every five
days can occur with hyperuricemic or hyperkalemic renal failure in chelonians, even when bathed and treated with
appropriate fluids.
13
Urine specific gravity is not useful for monitoring hydration.
Nutritional support: when and what
Anorexia is one of the most common presenting complaints from reptile owners, and nutritional support is
frequently included in the long-term medical management of reptile diseases. Proper hydration and body
temperature must pave the way for nutritional supplementation to avoid potentially fatal “refeeding syndrome”
characterized by hypokalemia and hypophosphatemia. DO NOT RUSH TO FEED. It is often better to wait several
days before providing nutritional support beyond diluted simple carbohydrates and electrolytes. Ensure normal
muscle strength before attempting to assist feeding a reptile, or risk regurgitation and aspiration pneumonia.
Nutritional needs vary among herbivores, omnivores, insectivores, and carnivores, and feeds must be chosen to meet
nutritional needs. Several commercially available products are available for assisted enteral feeding of reptiles. The
following list includes the products that the author uses and recommends. Nutritional support begins by feeding the
enterocytes with either half-strength Pedialyte (Abbott Laboratories) or Gatorade (Stokely-VanCamp, Inc., Oakland,
CA). Herbivores may then be fed a variety of species-appropriate vegetables that have been processed in a blender
or Critical Care for Herbivores (Oxbow Animal Health, Murdock, NE). Carnivores may be fed insects or whole,
skinned rodents that have been processed in a blender, or Carnivore Care (Oxbow Animal Health, Murdock, NE).
Omnivores may be fed a combination of vegetables and appropriate prey items that have been processed in a blender
or Emeraid Psittacine Omnivore (Lafeber Co., Cornell, IL). Refer to Donoghue
14
for detailed nutrition information.
Estimate nutritional needs based on feeding history, body condition, energy requirements for maintenance,
and additional energy requirements for reproduction, growth, recovery from illness, or wound healing. The energy
required for maintenance in kcal/day can be designated “standard metabolic rate,” or SMR. The energy required for
maintenance in kcal/day can be designated “standard metabolic rate,” or SMR. In reptiles this is calculated
according to body weight (BW) in kilograms by this formula: SMR=10(BW
0.75
). This equals 2.4 kcal/day for a 150
g lizard. Estimate additional energy needs and multiply SMR by a factor between 0.2 and 4.0 to calculate
requirements. Begin by feeding most sick reptiles about 1 kcal/100 grams body weight/day. It is reasonable to
estimate that the ultimate goal of nutritional supplementation will be about 5 kcal/100 grams body weight/day
during the recovery period, though this will probably not be achieved during the hospital stay.
Begin feeding warmed, hydrated, anorectic patients with a small volume of diluted electrolyte and simple
carbohydrate solution. After several days of this, move up to water-diluted meals containing 25–50% of SMR.
Keep initial volume less than 1% of body weight (w:v). Increase calories, concentration, and volume gradually over
the course of several days. In these early stages it is appropriate to divide total daily needs into several small meals
spaced evenly over 24 hours. If regurgitation occurs, try further dilution with water and smaller meal volumes. Over
time the volume can increase to as much as 3% of the body weight, and meals should be given less often. In fact,
most lizards and chelonians only need to eat about 3 times a week. Begin to encourage voluntary feeding as soon as
mentation is appropriate and activity levels rise. Discontinue assisted feeding when the patient feeds voluntarily.
References
1. Bartlett PP, Griswold B, Bartlett RD. Reptiles, Amphibians, and Invertebrates: An Identification and Care
Guide. Hauppage, NY: Barron's Educational Series, Inc.; 2001.
2. Chinnadurai SK, Wrenn A, Devoe RS. Evaluation of noninvasive oscillometric blood pressure monitoring
in anesthetized boid snakes. J Am Vet Med Assoc 2009; 234:625-630.
3. Chinnadurai S, Devoe R, Koenig A, Gadsen N, Hernandez-Divers S. Comparison of an implantable
telemetry device and an oscillometric monitor for measurement of blood pressure in anesthetized and unrestrained
green iguanas (Iguana iguana). Proceedings of the Association of Reptilian and Amphibian Veterinarians, 15
th
Annual Conference 2008; 94-95.
4. Barrows M, McArthur S, Wilkinson R. Diagnosis. In: McArthur S, Wilkinson R, Meyer J, editors.
Medicine and Surgery of Tortoises and Turtles. Oxford, England: Blackwell Publishing, Ltd.; 2004. pp. 109-140.
5. Diethelm G. Reptiles. In: Carpenter J, editor. Exotic Animal Formulary, 3
rd
edition. St. Louis, Missouri:
Elsevier Saunders; 2005. pp. 53-132.
6. Martinez-Jimenez D, Hernandez-Divers SJ. Emergency care of reptiles. Vet Clin North Am Exot Anim
Pract 2007; 10:557-585.
7. Minnich JE. The use of water. In: Gans C, Pough FH, editors. Biology of the Reptilia: Volume12,
Physiology C. New York: Academic Press; 1982. pp. 325-395.
8. Peterson CC, Greenshields D. Negative test for cloacal drinking in a semi-aquatic turtle (Trachemys
scripta), with comments on the functions of cloacal bursae. J Exp Zool 2001; 290:247-254.
9. Mader DR, Rudloff E. Emergency and critical care. In: Mader, DR, editor. Reptile Medicine and Surgery,
2
nd
edition. St. Louis, Missouri: Saunders Elsevier; 2006. pp. 533-548.
10. Mitchell MA. Therapeutics. In: Mader DR, editor. Reptile Medicine and Surgery, 2
nd
edition. St. Louis,
Missouri: Saunders Elsevier; 2006. pp. 631-664.
11. Munsey LD. Water loss in five species of lizards. Comp Biochem Physiol A Physiol 1972; 43:781-794.
12. Jackson DC. Surviving extreme lactic acidosis: the role of calcium lactate formation in the anoxic turtle.
Respir Physiol Neurobiol 2004; 144:173-178.
13. McArthur S. Problem solving approach to common diseases of terrestrial and semi-aquatic chelonians. In:
McArthur S, Wilkinson R, Meyer J, editors. Medicine and Surgery of Tortoises and Turtles. Oxford, UK: Blackwell
Publishing Ltd; 2004. pp. 309-377.
14. Donoghue S. Nutrition. In: Mader, DR, editor. Reptile Medicine and Surgery, 2
nd
edition. St. Louis,
Missouri: Saunders Elsevier; 2006. pp. 251-298.
... Intracelomic fluid was also administrated to correct the mild dehydration. Ringer's solution for reptiles (Hartmann's solution and 0.45% sodium chloride with 2.5% glucose in a ratio of 1:2) was administered (9,11,23) by 25 mL/kg/day for the initial two days, then 15 mL/kg/day for next six days. ...
... Generally, soaking reptiles in fluid is not advisable when the lizard is debilitated as it cannot lift up its head, so oral administration of fluid was done. Fluids were administered as a combination of warm water with oral rehydration powder (electrolyte powder) and multivitamin syrup @ 10ml/kg/day (2,5). This fluid treatment was continued for a week orally (Figure 2). ...
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Chapter
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Chapter
EmaciationAnorexiaInactivity/lethargyGeneralised WeaknessExcessive weight gainUnderweightParesisAtaxia, Convulsion, CirclingAbnormal mucous membrane colourApparent anaemiaMucous membrane pallorJaundiceAbnormal flotationPost-Hibernation anorexiaBlepharoedemaBlepharospasmCorneal lesionsBlindnessOcular DischargeNasal DischargeDyspnoeaExcessive Extension of NeckStomatitisPharyngeal oedemaExcessive salivationVomiting/regurgitationGastrolithsDiarrhoeaFailure to DefecateSubcutaneous SwellingGeneralised OedemaCoelomic SwellingCoelomic MassDystociaPenile ProlapseCloacal organ prolapseCloacal haemorrhageJoint swellingLamenessTraumaExcessive odourDermatitisExcessive sloughing of skinExcessive shedding of scutesExcessive skin sheddingShell UlcerationShell fractureShell distortionPyramiding of shellFlat shellSoft shellShell discolourationOvergrowth of beak and nailsPlastronal lesionsPlastronal discolourationSwelling of lateral headBurnsDeflated limbsSunken eyesDecreased skin elasticityFailure to urinateUrolithsLimb TraumaGreen Urine
Chapter
AnorexiaCloacal Organ ProlapseCutaneous and Subcutaneous LesionsCystic CalculiDiarrhoeaDystociaEar InfectionsEctoparasitesEndoparasitesFollicular StasisFrost DamageGoutHeat DamageHepatic DiseaseHepatic LipidosisHypervitaminosis AHypothyroidism/HypoiodinismHypovitaminosis AHypovitaminosis B1 (THIAMINE)Lower Digestive Tract DiseaseIntestinal Impaction/ObstructionEnteritis and ColitisFungal EnteritisAmoebiasisBalantidium and NyctotherusCoccidiansCryptosporidiosisTrichomonas/FlagellatesHexamitaMetazoan ParasitesAscaridsOxyurids (PINWORMS)ProatractisOther Metazoan ParasitesNeoplasia of the Digestive TractLower Respiratory Tract InfectionsMaladaptationMetabolic Bone Disease (MBD) and Nutritional Secondary HyperparathyroidismMetastatic Calcinosis/PseudogoutPosterior Paresis or WeaknessPost-Hibernation Anorexia (PHA)Renal DiseaseSepticaemiaSight ProblemsSteatitisStomatitisUpper Respiratory Tract Disease (URTD)/Runny-Nose Syndrome (RNS)Viral DiseaseWeight Abnormalities—OverweightWeight Abnormality—UnderweightYolk Coelomitis
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