Electrolytes & Acid-Base

Sodium's primary role

Major determinant of effective circulating volume and tonicity.

Mechanism of change for sodium and chloride concentrations

Changes in free water.

Hormone that causes water retention in the kidneys

Antidiuretic hormone (ADH).

Effect of aldosterone on renal tubules

Causes Na absorption and K excretion by renal distal tubules.

Role of Parathormone (PTH)

Regulates Ca, P, Mg and works to increase serum calcium.

Emergency hormone to bring down blood calcium

Calcitonin.

Electrolyte movement during acidosis

Potassium and magnesium move extracellularly in exchange for H+.

Effect of alkalosis on ionized calcium

Decreases ionized calcium because there is less competition for albumin binding sites.

Two main plasma volume factors related to proteins and fluid shifts

Oncotic pressure due to albumin concentration and sodium concentration (tonicity of blood).

Most accurate method for measuring electrolytes

Ion-selective electrodes (ISE), as they measure directly without dilution and are unaffected by proteins or lipids.

Dominant extracellular anion

Chloride.

Most likely cause of hyperchloremia

Dehydration.

Electrolyte imbalance seen with duodenal vomiting

Hyponatremia and Hypochloremia.

Dominant intracellular cation

Potassium.

Effect of hypoaldosteronism on potassium

Causes hyperkalemia due to reduced K excretion.

Acid-base status that causes hyperkalemia due to extracellular shift

Acidosis.

Mechanism by which insulin therapy can cause hypokalemia

Insulin drives potassium inside the cell.

Total Carbon Dioxide (TCO2) as a clinical marker

Used as an approximation for bicarbonate concentration.

Biologically active portion of calcium

Ionized calcium.

Three ways PTH increases serum calcium

Increases bone reabsorption, increases vitamin D formation by the kidney, and promotes the resorption of bone.

Protein produced by tumors that mimics PTH effects and causes hypercalcemia

PTH-related Protein (PTHrP).

Mechanism of hypocalcemia in pancreatitis

Fat necrosis leads to soap formation (saponification) with precipitation of calcium around the pancreas.

Main regulators of phosphorus in the body

Parathormone (PTH) and Vitamin D.

High Anion Gap (KLUE mnemonic)

Ketone bodies, Lactate, Uremic acids, Ethylene Glycol poisoning.

Major particle in blood responsible for tonicity

Sodium (and also glucose).

Purpose of the Osmolal Gap calculation

To detect unmeasured particles in serum.

Role of the respiratory system in acid-base homeostasis

Fast response (minutes-hours) to 'blow off' CO2 to correct acidosis or retain CO2 to correct alkalosis.

Most common acid-base disturbance in non-ruminant domestic animals

Metabolic acidosis.

Expected compensation for metabolic acidosis

Decreased pCO2 (respiratory alkalosis), characterized by panting or hyperventilation.

Cause of paradoxical aciduria in a cow with abomasal displacement

Loss of H+ and Cl- into the trapped abomasum, leading to metabolic alkalosis, hypovolemia-induced RAAS activation, and subsequent excretion of H+ by the kidneys in exchange for Na+ due to K+ depletion.