Today's Veterinary Practice

JAN-FEB 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 66 FLUID THERAPY enteral water but is not willing to drink an adequate amount, a feeding tube can be used to provide fluids. An esophagostomy tube placed for feeding can also be used for water intake. Alternatively, a nasoesophageal tube can be placed to provide water and liquid diets ( FIGURE 4 ). This is particularly useful in patients that cannot tolerate IV fluids, such as those with cardiac and/or renal disease. TYPES OF FLUIDS Crystalloids Crystalloids are fluids containing small solutes (<500 Da), most of which are electrolytes, in particular sodium and chloride. 3 The electrolytes and water in these solutions move easily across the endothelium into the interstitial space. More than 60% to 80% of a crystalloid solution distributes out of the intravascular space within 20 to 30 minutes. 3,4 Crystalloid solutions can be classified as isotonic, hypotonic, or hypertonic. Isotonic Isotonic crystalloids have an osmolarity and sodium concentration similar to those of plasma. They are commonly used to treat interstitial dehydration and hypovolemia because fluid losses are typically isotonic or hypotonic. Isotonic solutions are considered balanced (or buffered) if their electrolyte composition and pH closely mirror those of plasma. Common balanced isotonic crystalloids include Plasmalyte-A ( baxter.com ), Normosol-R ( hospira.com ), and lactated Ringer's solution (LRS) ( TABLE 2 ). Metabolism of these FIGURE 4. A mixed-breed dog with neurologic disease and a nasoesophageal tube placed to administer water. The dog was unable to drink on its own and had developed hypernatremia. The tube allows administration of free water to correct the hypernatremia. TABLE 2 Comparison of Various Crystalloid Solutions 7 CRYSTALLOID OSMOLARITY, MOSM/L SODIUM, MEQ/L CHLORIDE, MEQ/L POTASSIUM, MEQ/L MAGNESIUM, MEQ/L BUFFER (MEQ/L) Plasmalyte-A 295 140 98 5 3 Acetate (27) Gluconate (23) Plasmalyte-56 and 5% dextrose 362 40 40 13 3 Acetate (16) Normosol-R 295 140 98 5 3 Acetate (27) Gluconate (23) Normosol-M and 5% dextrose 363 40 40 13 3 Acetate LRS 273 130 109 4 0 Lactate (28) D5W 253 0 0 0 0 0 0.45% NaCl 154 77 77 0 0 0 0.9% NaCl 310 154 154 0 0 0 3% NaCl 1026 513 513 0 0 0 7.5% NaCl 2566 1283 1283 0 0 0

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