Fluid Administration in Reptiles

Key Points

  • Administer pre-warmed fluids.
  • Maintenance requirements are estimated at 10-30 ml/kg/day in reptiles.
  • Plasma osmolarity may be helpful in the selection of fluids that will be isotonic for an individual patient.
  • Fluids may be administered subcutaneously or per os for mild to moderate dehydration.
  • Fluids can be administered intracoelomically, intravenously, or intraosseously for moderate to severe dehydration.

Introduction

The basic principles of fluid therapy are the same in the reptile as seen in birds and mammals (Fig 1). However reptile anatomy and physiology make some features of this crucial supportive care procedure unique.

Subcutaneous fluid administration in a bearded dragon

Figure 1. The basic principles of fluid therapy are the same in all species. Shown here, subcutaneous fluid administration in a bearded dragon (Pogona vitticeps). Photo credit: Dr. Ariana Finklestein. Click on image to enlarge.

 

Fluid resuscitation

Reptiles are able to maintain hemodynamic stability in the face of substantial hemorrhage because of a rapid shift of interstitial fluid into the vascular space (Box 1) (Roberts 2016, Martinez-Jimenez and Hernandez-Divers 2007, Smits and Kozubowski 1985, Smits and Lillywhite 1985b). Fluid resuscitation is required in cases of hypovolemic shock, severe blood loss, septic shock, and/or severe acid-base disturbances.

Box 1. Clinical signs of hypovolemic/hemorrhagic/septic shock
  • Prolonged capillary refill time
  • Pale mucous membrane color
  • Weakness
  • Tachycardia or bradycardia
  • Hypothermia (appendages cool to the touch)

Evaluation of pallor can be problematic in reptiles, because mucous membranes may normally be pale or variably colored in many reptiles. Evaluation of heart rate is also tricky since heart rare varies with the species and the temperature.

Warm fluids to the mid-preferred optimum temperature zone for your species of interest. Use crystalloids along with colloids in hypovolemic shock and other perfusion deficits Bolus 5-10 ml/kg of isotonic crystalloid solution IV or IO followed by colloid solution 3-5 ml/kg IV/IO over 5-10 minutes (Martinez-Jimenez and Hernandez-Divers 2007).

 

Dehydration

Replacement fluids are indicated for ongoing loss caused by vomiting, diarrhea, or diuresis and for dehydration. Until the problem is quite advanced, recognition of dehydration in the reptile can be challenging (Box 2). Suspect dehydration in any reptile that presents with a history of substandard care. Constipation can be indicative of chronic dehydration in all species (Music and Strunk 2016).

Box 2. Clinical signs of dehydration in reptiles
  • Tacky mucous membranes
  • Dry, ropy mucus in the oral cavity
  • Weight loss
  • Sunken eyes

Reptile skin is not supple or elastic, however the lateral body wall is the best place to detect delayed skin turgor in snakes and lizards. Prolonged capillary refill time may also be observed by placing a cotton-tipped applicator on the palatine vessel of snakes and lizards.

Blood work is often the best way to identify and monitor hydration in reptiles (Box 3).

Box 3. Blood work clues to hydration status in reptiles
  • Packed cell volume/total protein
  • Sodium
  • Chloride
  • Plasma osmolarity

Many reptiles have a high tolerance for dehydration and increases in plasma sodium and osmolarity have been documented. In fact, many arid species cope with dehydration by major elevations in plasma osmolarity that would be fatal to mammals. A wide range has also been documented in packed cell volume (20% -35%) and total protein (3-7 g/dL) in normal reptiles (Fleming 2015, Martinez-Jimenez 2007).

Although the significance of plasma osmolarity is debated, normal values typically range from 250-400 mOsm/L (Sanchez-Migallon Guzman et al 2011, Dallwig et al 2010, Kirchgessner 2009, Nevarez 2009, Martinez-Jimenez and Hernandez-Divers 2007, Wilkinson 2004, Maxwell 2003, Christopher 1994).

Box 4. Mean osmolarity values reported in reptiles
Species mOsm/L
Bearded dragon (Pogona vitticeps) 295.4
Corn snake (Elaphe guttata) 344.5
Desert iguana (Dipsosaurus dorsalis) 300
Desert tortoise (Gopherus agassizii) summer hydrated 291
Desert tortoise summer dehydrated 334
Greek tortoise (Testudo graeca) summer 290
Greek tortoise hibernation 404
Green iguana (Iguana iguana) 330
Red-eared slider (Trachemys scripta elegans) 260

Osmolarity should be calculated using an osmometer whenever possible, however osmolarity may also be estimated using one of the following formulas (Box 5).

Box 5. Estimating osmolarity*
2 x (Na + K)
or
2 x (Na + K) + glucose + urea

*All measurements in mmol/L

 

Fluid selection

The osmolality of apparently healthy reptiles can vary widely making selection of an appropriate isotonic fluid challenging. The majority of crystalloid solutions used in mammals may be hypertonic or hypotonic depending on the individual reptile (Box 6)(Mitchell 2009).

Box 6. Osmolarity of crystalloid solutions
Type of Fluid mOsm/L
2.5% Dextrose 126
5% Dextrose 253
Lactated Ringer’s solution 272
Jarchow’s modification 278
2.5% Dextrose in 0.45% saline 280
Normosol-R 294
0.9% Sodium Chloride 308
5% Dextrose in Lactated Ringer’s 525

Jarchow’s modification consists of two parts 2.5% dextrose in 0.45% saline and one part lactated Ringer’s solution (Mader 2006).

 

Maintenance fluids

Maintenance requirements are lower in reptiles when compared to dogs and cats because of their lower metabolic rate. Depending on the species, maintenance fluids for reptiles are estimated at 10-30 ml/kg/day (Music and Strunk 2016, Mitchell 2009, Nevarez 2009). Replace deficits over 48 to 96 hours (Box 7) (Martinez-Jimenez and Hernandez-Divers 2007).

Box 7. Volume of fluid required for rehydration
Hydration deficit x body weight (kg) x 1000 ml

 

Routes of fluid administration

Subcutaneous and/or oral fluids are appropriate for mild to moderate dehydration. Administer fluids intracoelomically, intravenously, or intraosseously for moderate to severe dehydration. Regardless of the route selected, pre-warm fluids.

Soaking

Soaking a reptile in warm water bath can be a supplemental part of fluid therapy. Water absorption may take place through the cloaca (Campbell 2014, Martinez-Jimenez and Hernandez-Divers 2007, Minnich 1982). Soaking can also stimulate drinking, particularly in chelonians.

Oral fluids

Oral fluids are a preferred route for fluid therapy, particularly in snakes and lizards, however it relies on the presence of a functional gastrointestinal tract and an appropriate body temperature (Music and Strunk 2016). Administration of oral fluids requires passage of a stainless steel feeding tube or flexible rubber tube into the stomach. Aspiration is rare since the glottis is normally closed in reptiles except during breathing (Ackerman and Aspinall 2016, Mader 2006).

Visit Nutritional Support in Reptiles for advice on tubing a snake, lizard, or chelonian.

Subcutaneous

Subcutaneous fluids are typically administered into the subcutaneous space above the lateral body wall in snakes and lizards (Fig 1). In chelonians, use the inguinal region or prefemoral fossa.

Intracoelomic

Although intracoelomic fluid therapy was favored in the past, this route is no longer recommended except in select cases as fluid can enter the lungs, urinary bladder, and gastrointestinal tract directly (Music and Strunk 2016, Gibbons 2014). It is particularly important to avoid the intracoelomic route if the lungs can be compromised as with a carapacial fracture (Sykes 2006). Administer subcutaneous fluids whenever possible.

To perform an intracoelomic injection…

  1. Position squamates (snakes and lizards) in dorsal recumbency and chelonians in lateral recumbency.
  2. Clean the area with alcohol or another topical disinfectant.
  3. To prevent injection of fluids or drugs into the lungs or air sacs, insert the needle in the caudal one-fourth of the coelom in snakes and the caudal third in chelonians and lizards. Avoid the ventral midline in lizards to prevent laceration of the ventral abdominal vein.
  4. Carefully introduce the needle parallel to the body wall; point the needle cranially. Advance the needle between the ventral belly scutes near the junction between the lateral and ventral scales in snakes. (Scutes are specialized external plates or scales). In chelonians, insert the needle where skin folds attach to the bridge at the prefemoral fossa.
  5. Take care not to introduce the needle too far, especially in gravid females. Always aspirate the needle first to make sure the needle did not enter the respiratory tract.
  6. Infuse no more than
  7. 20-30 ml/kg/day.

Epicoelomic fluid administration may be a better option in chelonians. The injection is made between the plastron and the coelomic membrane. Insert the needle laterodorsal to head and neck and just dorsal to plastron and slightly below the pectoral muscles. Up to 10-20 ml/kg may be safely administered in this area.

Intravenous

Intravenous catheter placement requires a surgical cut-down in snakes and lizards therefore local or general anesthesia as well as preemptive analgesia are required (Antinoff 2016, Music and Strunk 2016). If clinical condition allows, warm the patient before IV catheter placement since reptiles have the ability to shunt blood away from the periphery during periods of dehydration and debilitation (Roberts 2016, Mader 2006). Catheters may be used for bolus or constant rate infusions. As in other species, IV catheters require 24-hour monitoring since disconnection can lead to fatal hemorrhage (Box 8).

Box 8. Sites for intravenous fluid administration
Vein Snakes Lizards Chelonians
Cephalic X*
Jugular X* X* X
Caudal tail X X
Ventral abdominal X**

*Surgical cut-down required
**Utilize in anesthetized patients only as movement can be associated with vessel laceration and profound intracoelomic hemorrhage

 

The cephalic vein is the best vessel to catheterize in lizards. The cephalic vein runs mediolaterally across the antebranchium as in dogs and cats. Carefully perform a transverse cut-down that begins at the medial antebrachium using the tip of an 18-or 20-gauge needle or a number 11 surgical blade. Take care as the cephalic is superficial and easily nicked. Then expose the vessel with blunt dissection (Mader 2006).

Either the right or left jugular vein can be catheterized, however the right vessel tends to be larger. In chelonians, some clinicians perform a small cut-down or at least create a relief hole. The jugular vein is entered in the distal one-half to one-third of the neck (Antinoff 2016, Mader 2006). Select a flexible, Teflon catheter long enough to reach the thoracic inlet to minimize the risk of kinking when the turtle bends its neck.

To catheterize a snake jugular vein (de la Navarre 2006, Mader 2006):

  1. Place the snake in dorsal recumbency.
  2. Identify the apex beat of the heart.
  3. Count cranially 9-10 ventral scales.
  4. Aseptically prepare the skin.
  5. Make a small (2-3 scutes or 0.5-1.0 cm) incision between the scales.
  6. Bluntly dissect at the medial margin of the ribs to reveal the jugular vein as it runs parallel and medial to the free margin of the ribs.
  7. Use sterile mosquito hemostats and atraumatic forcep to manipulate the vessel as needed.
  8. Insert a catheter of appropriate size.
  9. Surgically close the skin.
  10. Secure the catheter with tape and monofilament suture material or suture glue.

Catheterization is more difficult in snakes. Jugular catheterization can be accomplished under sedation. The jugular vein is approached 10 scutes cranial to the heart, at the junction of the scutes and scales (Antinoff 2016). Intracardiac catheter placement has also been described for short-term, emergency delivery of fluids directly into the ventricle of the moribund snake (Antinoff 2016, Battaglia and Steele 2015, de la Navarre 2006, Mader 2006, Martinez-Jimenez and Hernandez-Divers 2007).

To place an intracardiac catheter in the snake…

  1. Place the animal in dorsal recumbency.
  2. Identify the apex beat of the heart.
  3. Aseptically prepare the skin.
  4. Direct a catheter of appropriate size between the scutes into the ventricle.
  5. Secure the catheter with tape.

The thick wall of the ventricle , the relatively low blood pressure of the snake combined with its slow heart beat means that hemorrhage and tamponade are “generally not a problem” (Mader 2006).

Intraosseous

Intraosseous (IO) catheter placement in lizards requires heavy sedation, local anesthesia or general anesthesia paired with pre-emptive analgesia. The preferred site is the medial tibial crest. Enter at the craniomedial aspect of the bone to prevent invasion of the joint capsule (Ackerman and Aspinall 2016, Antinoff 2016, de la Navarre 2006, Mader 2006). Use of the femur in a retrograde fashio has also been described but insertion invades the stifle joint (Antinoff 2016, de la Navarre 2006). Catheter placement is contraindicated with sepsis or metabolic bone disease. A fluid or syringe pump will be necessary for the IO catheter to flow.

Jugular catheter placement is generally a lot easier than IO catheter placement in chelonians, however in many species the tibial crest and gular plastron are the two primary sites (Ackerman and Aspinall 2016). Although this is a relatively difficult procedure, the bony bridge may also be catheterized. There is some controversy as to whether the bridge communicates with vasculature (Martinez-Jimenez and Hernandez-Divers 2007).

There are no sites for IO catheter placement in snakes.

 

Patient monitoring

Blood pressure in reptiles is controlled by mechanisms similar to those described in mammals (Chiu et al 1986, Martinez-Jimenez and Hernandez-Divers 2007, Stephens et al 1983). Blood pressure screening has been described in a variety of reptile species (Schumacher and Mans 2014, Hernandez et al 2011). Although direct blood pressure measurement can be valuable, indirect values are unlikely to be accurate. Nevertheless, trends or changes in blood pressure can be helpful in guiding fluid therapy (Martinez-Jimenez and Hernandez-Divers 2007, Lichtenberger 2007).

Weigh patients receiving fluids at least once or twice daily, and monitor urine output. Also monitor the reptile closely for evidence of overhydration (Box 9)(Gibbons 2014, Silverstein 2009, Macintire 2006).

Box 9. Signs of overhydration
  • Serous nasal discharge
  • Jugular venous distension (when visible)
  • Tachypnea secondary to pulmonary edema
  • Peripheral edema
  • Weight gain

Visit Exotic ICU: Nursing Care for Reptiles for additional information on monitoring the reptile patient.

 

References

References

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To cite this page:

Pollock C, Arbona N. Fluid administration in reptiles. September 30, 2017. LafeberVet Web site. Available at https://lafeber.com/vet/fluid-administration-in-reptiles/