Today's Veterinary Practice

MAR-APR 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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55 MARCH/APRIL 2018 ● TVPJOURNAL.COM FEATURES Although select cases may require higher supplementation, in most patients it is important that the total potassium administration rate not exceed 0.5 mEq/kg per hour because rapid fluctuations in potassium levels and hyperkalemia can precipitate cardiac arrhythmias. The replacement fluids that are frequently used in hospitalized patients do not contain sufficient potassium if the patient is anorexic. a TABLE 2 provides general guidelines on how much potassium to add to fluids based on serum potassium concentration. Administration of fluids with >60 mEq/L (15 mEq/250 mL) of potassium through peripheral catheters is not recommended because phlebitis can result. 3 HYPOPROTEINEMIA Hypoproteinemia is commonly seen in small animals and may be secondary to losses through the gastrointestinal tract or kidneys (such as with protein-losing enteropathies or nephropathies), decreased hepatic production (as seen in sepsis, acute inflammation, or liver disease), or sequestration secondary to vasculitis or effusions. Albumin is the most abundant plasma protein and is essential to maintaining normal colloid osmotic pressure (COP). Normal whole blood COP is 19.9 ± 2.1 in dogs and 24.7 ± 3.7 in cats. 5 Hypoalbuminemia can result in increased loss of fluid from the intravascular space to the interstitium, causing pulmonary and peripheral edema, as well as body cavity effusions and volume depletion. In patients with significant hypoalbuminemia and ongoing albumin losses or anorexia, colloid administration may be indicated as part of a fluid therapy plan. Administration of colloid solutions to patients will not necessarily pull fluid back into the intravascular space, but by raising COP, it will counteract hydrostatic pressure and reduce fluid loss into the interstitium. 6 CARDIAC DISEASE Administration of fluids to patients with underlying cardiac disease is generally contraindicated; however, some of these patients cannot meet their fluid needs because of underlying comorbidities and/ or anorexia. In patients that can tolerate enteral fluids but are unwilling to drink, a nasoesophageal, nasogastric, esophagostomy, or gastrostomy tube can be used to administer fluid. This can be particularly helpful in patients that develop azotemia secondary to diuretic administration but continue to require diuretic therapy. Fluid needs can be calculated in the same manner as IV fluids (ie, dehydration plus maintenance plus ongoing losses). In patients that cannot tolerate enteral water and have underlying cardiac disease but no overt heart failure, cautious IV fluid therapy may be instituted. Starting at low rates (eg, 1 mL/kg per hour) with diligent monitoring is recommended. Use of 0.45% saline can be considered because the higher amount of free water and lower sodium content theoretically has a lower risk of causing fluid overload. OLIGOANURIA AND POLYURIA Oligoanuria Patients with decreased urine output secondary to acute kidney injury, end-stage chronic kidney disease, or postrenal obstruction of the urinary tract are at high risk for hypervolemia and fluid overload. Patients that are dehydrated and oligoanuric may still benefit from IV fluid therapy, but low rates of fluid administration (1 to 2 mL/kg per hour) with close monitoring are recommended. Once the patient appears clinically euhydrated, discontinuation of IV fluids is recommended until adequate urine output can be restored because overhydration results in organ edema and dysfunction, in addition to pulmonary edema and worsening kidney injury. a See TABLE 2 in "Fluid Therapy in Hospitalized Patients: Patient Assessment and Fluid Choices," [TVP JanFeb18], for potassium concentrations of common fluids. TABLE 2 Guidelines on Amount of Potassium to Add to Fluids SERUM POTASSIUM CONCENTRATION (MEQ/L) MEQ KCL TO ADD TO 250 ML OF FLUID MAXIMAL FLUID RATE (ML/KG/HR)* <2.0 20 6 2.1–2.5 15 8 2.6–3.0 10 12 3.1–3.5 7 18 3.6–5.0 5 25 Adapted from reference 4. *So as not to exceed 0.5 mEq/kg per hour.

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