Electrolytes Clinical Pathology

Electrolytes Electrolytes and acid-base disorders may result from many different diseases. Correction of fluid, electrolytes, and acid- base disturbances is often more immediate benefit to patients than a specific diagnosis. Most common electrolytes that are measured are Na +, K +, Cl -, and HCO 3, as TCO 2. Serum is the best place to observe the electrolyte levels.

Anion Gap Used to determine metabolic acidosis (Na + +K + )- (Cl - + HCO 3 )

Sodium Most abundant electrolyte in blood. Functions: Maintain osmotic pressure Acid-base balance Transmit nerve impulses Essential for renal water retention (controls hydration status).

Hyponatremia Diabetes Mellitus (DM) Addison’s disease Diarrhea (foals and horses) Renal disease (cattle) Salt deficiency (cattle) Ruptured urinary bladder (horse, dog, cat) Saliva loss (horse) Psychogenic polydipsia

Hypernatremia Panting Sweating Diabetes insipidus Increased GI water in ruminants (grain overload acidosis, propylene glycol toxicity).

Normal Sodium Values Normal values: Dogs: mEq/L Cats: mEq/L Neurologic signs may occur at 170 mEq/L in dogs.

Serum Chloride Important in many secretions Saliva Sweat gastric Increases and decreases may parallel change in serum sodium Normal values: Dogs: mEq/L Cats: mEq/L Danger values are unknown

Potassium Serum potassium is maintained within narrow limits for normal neuromuscular and cardiac function. Potassium is released from platelets during clotting. Normal values: Dogs: mEq/L Cats: mEq/L Danger values are <2.5 mEq/L May result in cardiac conduction disturbances

Hyperkalemia and Hypokalemia Hyperkalemia Anuria Addison’s Parenteral administration Hypokalemia Loss through GI fluids, urine or anorexia.

Calcium Dietary intake rarely effects serum levels directly 99% of Calcium is stored in the bone, other in cells and extracellular fluid Functions: Main component of bones and teeth Cofactor for clotting Necessary for transmission of nerve impulses and muscle contraction

Hypercalcemia and Hypocalcemia Hypercalcemia Renal failure (horses) Neoplasia Certain plants Addison’s Hypocalcemia Hypoproteinemia Milk fever (eclampsia) Hypomangesmic tetany Panceatitis

Blood Gas Anaylsis Useful in any severely ill dog or cat (vomiting, diarrhea, etc) Analysis of proper evaluation of gas exchange and alterations of TCO 2 in patients with respiratory disorders Analyzers are equipped with specific electrodes to measure pH carbon dioxide tension (pCO 2 ), and oxygen tension (pO 2 ). Arterial blood is ideal but jugular vein blood may be used.

Blood Gas Analysis Continued Blood is collected in a heparinized syringe. The blood is immediately injected into the machine for analysis Test takes minutes Used to determine if animal is in metabolic acidosis/alkalosis or respiratory acidosis/alkalosis.

Metabolic Acidosis Characterized by decreased plasma HCO 3, decrease pH, and decrease pCO 2 Loss of HCO 3 usually occurs via the GI tract but may also occur via the kidneys

Respiratory Acidosis Due to decreased effective ventilation (increased pCO 2 ). Decrease pH and compensatory increase in HCO 3. Hypoventilation may occur from airway obstruction, cardiopulmonary arrest, and neuromuscular diseases.

Metabolic Alkalosis Increased plasma HCO 3, increased pH, and compensatory increased CO 2. Caused by loss of chloride rich fluid via the GI tract

Respiratory Alkalosis Results from increased ventilation. Decreased pCO 2, increased pH and decrease HCO 3. Caused by tachypnea due to hypoxemia usually secondary to a disease process.