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 HCO3, as TCO2.

• Serum is the best place to observe the electrolyte levels.

Anion Gap

• Used to determine metabolic acidosis

• (Na++K+)- (Cl- + HCO3)

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: 140-150 mEq/L• Cats: 150-160 mEq/L

Neurologic signs may occur at <120 or >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: 105-115 mEq/L• Cats: 115-125 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: 3.5-5.5 mEq/L• Cats: 3.5-5.5 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 TCO2 in patients with respiratory disorders

• Analyzers are equipped with specific electrodes to measure pH carbon dioxide tension (pCO2), and oxygen tension (pO2).

• 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 15-30 minutes• Used to determine if animal is in metabolic

acidosis/alkalosis or respiratory acidosis/alkalosis.

Metabolic Acidosis

• Characterized by decreased plasma HCO3, decrease pH, and decrease pCO2

• Loss of HCO3 usually occurs via the GI tract but may also occur via the kidneys

Respiratory Acidosis

• Due to decreased effective ventilation (increased pCO2).

• Decrease pH and compensatory increase in HCO3.

• Hypoventilation may occur from airway obstruction, cardiopulmonary arrest, and neuromuscular diseases.

Metabolic Alkalosis

• Increased plasma HCO3, increased pH, and compensatory increased CO2.

• Caused by loss of chloride rich fluid via the GI tract

Respiratory Alkalosis

• Results from increased ventilation.

• Decreased pCO2, increased pH and decrease HCO3.

• Caused by tachypnea due to hypoxemia usually secondary to a disease process.