Fluid Therapy in Small Ruminants and Camelids

Fluid Therapy in Small Ruminants and Camelids a, b Meredyth Jones, DVM, MS *, Christine Navarre, DVM, MS KEYWORDS Fluid therapy Sheep Goat Llama Alpaca Crystalloid Colloid Parenteral nutrition KEY POINTS Animals estimated to be more than 8% dehydrated should receive intravenous resuscita- tion at least initially, and then may be maintained on intravenous or oral fluid therapy. Hypoglycemia, hyperkalemia, and acidosis are the most life-threatening abnormalities, and require most immediate correction. Crystalloid solutions should be used cautiously in animals with hypoproteinemia because of the risk of pulmonary edema. Synthetic or natural colloid solutions are preferred in these patients. Hypertonic solutions are useful for short-term improvement of cardiac output, drawing water from the interstitium into the vasculature; they are contraindicated in hyperosmolar syndromes such as carbohydrate overload. Dextrose-containing solutions are indicated for use in hypoglycemic animals or those with hepatic lipidosis syndromes, but must be administered judiciously to achieve energy sup- plementation without inducing glucose diuresis. Insulin may be indicated to improve glucose utilization. Parenteral nutrition is indicated in patients with anorexia, those with severe systemic disease, and those with evidence of protein loss, and should be initiated early in the thera- peutic period to achieve maximum efficacy. INTRODUCTION Body water, electrolytes, and acid-base balance are important considerations in the evaluation and treatment of animals with any disease process, with restoration of these a priority as adjunctive therapy. The goals of fluid therapy should be to maintain cardiac output and tissue perfusion, and to correct acid-base and electrolyte abnormalities. The authors have no disclosures. a Food Animal Field Services, Department of Large Animal Clinical Sciences, College of Veter- inary Medicine, Texas A&M University, 4475 TAMU, College Station, TX 77843, USA; b LSU AgCenter, 105 Francioni Hall–LSU, Baton Rouge, LA 70803-4210, USA * Corresponding author. E-mail address: [email protected] Vet Clin Food Anim 30 (2014) 441–453 http://dx.doi.org/10.1016/j.cvfa.2014.04.006 vetfood.theclinics.com 0749-0720/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved. 442 Jones & Navarre PATIENT EVALUATION A thorough physical examination is an important component of the evaluation of any patient, aiding in the diagnosis of the primary disease condition and the extent to which fluid and electrolyte therapy is indicated. Hydration Deficit Hydration deficit is best determined by reduction in body weight from the normally hy- drated state, but this baseline body weight is infrequently available when the dehydrated patient is evaluated. Mental state, skin turgor, color and texture of mucous membrane, temperature of the extremities, and recession of the globe are all used in combination to estimate hydration status, but these criteria have not been validated in ruminants or camelids (Table 1). Alterations in packed cell volume (PCV) and total plasma protein (TPP) may also be used as indicators of hydration status, but are limited in their utility. The reference interval for PCV is fairly wide, making it an insensitive indicator of hydration, and baseline values for an individual are rarely available. Moreover, owing to the prevalence of diseases in sheep, goats, and camelids that alter PCV and TPP (internal parasitism, failure of passive transfer, chronic inflammatory disease), these values must be interpreted in light of the history and physical examination findings. Electrolyte and Acid-Base Alterations Serum biochemistry and blood gas analysis are the most appropriate tools for assessment of electrolyte, glucose, and acid-base abnormalities. Results of this testing may help prioritize fluid components for replacement. In general, hypoglycemia, hyperkalemia, and acidosis represent abnormalities that are most life-threatening and require the most immediate correction. Fluid Administration Route The first decision to be made when initiating fluid therapy is whether fluids should be administered parenterally or enterally. In ruminants and camelids, large volumes of fluids may be administered into the rumen or first compartment, allowing for effective treatment of mild to moderate dehydration. In camelids specifically, the benefit of repeated oral fluid therapy should be weighed against the risks. Oral intubation is stressful in camelids and may induce cortisol-mediated lipolysis, particularly if repeated.1 Therefore, the authors rarely use oral fluid therapy in camelids. In general, the animals most likely to benefit from oral fluid therapy are those that are mentally alert, have good gastrointestinal motility, and are less than 8% dehydrated. Animals Table 1 Physical examination parameters for estimation of hydration deficit in ruminants and camelids Mild, 4%–6% Moderate, 7%–9% Severe, >10% Cervical skin tent 4–5 s 5–7 s >7 s Globe recession 2–3 mm 3–4 mm 6–8 mm Oral mucosa Moist, warm, pink Tacky, warm, pale Dry, cool, pale Extremities Warm Cool Cold Demeanor Standing, bright Sternal, slow Lateral, depressed Adapted from Constable PD, Walker PG, Morin DE, et al. Clinical and laboratory assessment of hydration status of neonatal calves with diarrhea. J Am Vet Med Assoc 1998;212:991–6; and Roussel AJ. Fluid therapy in mature cattle. Vet Clin N Am Food Anim Pract 1990;6(1):111–23. Fluid Therapy in Small Ruminants and Camelids 443 not meeting these criteria are best managed with at least initial parenteral fluid resus- citation and correction of acid-base and electrolyte abnormalities. In small ruminants, jugular catheterization is the most practical means of admin- istering intravenous fluid therapy. In sheep and goats, over-the-needle catheters are typically used and placed with relative ease. In camelids, placement of jugular catheters can be more challenging and, although over-the-needle catheters are acceptable, peel-away catheters (Fig. 1) or J-wire catheters may result in easier and more reliable placement. A stab incision made with a #15 scalpel blade helps facilitate the placement of over-the-needle catheters in these species, particularly camelids. Recommended catheter sizes for jugular catheterization are summarized in Table 2. Volume and rate When determining appropriate fluid volume and rate to be administered, one must consider: Replacement of hydration deficit Maintenance fluid needs Replacement of ongoing losses Plasma protein concentration Replacement of hydration deficit The volume required for hydration replacement is calculated using the following formula: (estimated % dehydration) Â (body weight in kg) 5 liters of fluid needed to replace deficit As a general rule, hydration replacement should occur over approximately 4 hours, with maintenance and ongoing losses administered over the remaining hours in the day. In animals with low total protein and in camelids, hydration replacement may need to be slower, with half of the volume replaced in 4 to 6 hours and the remainder given over 12 to 24 hours. Maintenance fluid requirement Maintenance fluid requirements account for normal water losses attributable to urination, defecation, respiration, sweat, and other Fig. 1. Placement of a peel-away catheter. A sheath is placed into the jugular vein, as in an over-the-needle catheter setup, and the needle is removed. The long, soft catheter is fed into the sheath, which is then peeled into two halves and out of the vein, leaving the catheter in place. 444 Jones & Navarre Table 2 Recommended catheter sizes for jugular catheterization Patient Adult Sheep, Goat Kid, Lamb Adult Llama, Alpaca Cria Catheter size 16 gauge 18 gauge 14–16 gauge 16–18 gauge 3.2500 (8.3 cm) 200 (5.1 cm) 3.25–5.500 (8.3–14 cm) 2–3.500 (5.1–8.9 cm) evaporation, and differ based on physiologic status (lactation, pregnancy) and age. Neonates have higher total body water volume than adults, and require a higher maintenance fluid volume. Maintenance fluid needs can be estimated using the following general guidelines: Adults: 50 mL/kg/24 hours or 1 mL/lb/h Neonates: 70 to 80 mL/kg/24 h or 2 mL/lb/h These numbers are typically used in all species and are supported by established water requirements of goats, which range from 30 to 66.6 mL/kg/d with a mean of 44.8 mL/kg/d.2 Neonates are typically assigned a higher maintenance volume, with 70 mL/kg found to be acceptable in calves.3 If fluid rates are difficult to control or are in animals likely to disrupt the fluid line, replacement fluids may be divided and administered every 3 hours by calculating the total volume needed for a 3-hour period and providing this as a single bolus. This approach is not appropriate with solutions that contain greater than 2% dextrose or with parenteral nutrition (PN) solutions. Ongoing losses Ongoing losses include fluid, protein, and electrolytes, which are lost as a result of a continuing disease process, such as diarrhea or internal or external loss of fluid. Quantifying ongoing losses can be challenging and, in the absence of the abil- ity to measure these directly, parameters such as PCV, TPP, serum electrolyte panel, and body weight may be used to monitor the success of fluid therapy to sustain body fluid, protein, and electrolyte balance. FLUID TYPE The 4 basic types of solutions used in clinical practice, which vary in composition, cost, and usefulness depending on the pathologic processes, are crystalloid solutions, colloid solutions,

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