Clinical Chemistry Tests

Question 1

Causes of hyponatremia

Answer 1

• Relative water excess (loss of sodium-containing fluid, diarrhea, excessive sweating, blood loss, fluid drainage, high-volume gastric reflux, high-volume pleural drainage)
• Adrenal insufficiency
• Sequestration of fluid (third-space problems - peritonitis, ascites, pleuritis, ruptured bladder, torsion or volvulus of the gut, excessive admin. of 5% dext)
• Water retention with normal effective circulating volume (psychogenic polydipsia, renal dz)

Question 2

Causes of hypernatremia

Answer 2

• Pure water losses (panting, water deprivation)
• Sodium excess (water restriction - salt poisoning, feeding only lytes no free water)
• Water loss exceeds electrolyte loss

Question 3

Causes of hypokalemia

Answer 3

• Altered external balance (vomiting, vagal indigestion, diarrhea, third-space problems, excessive sweat losses, dietary deficiency, prolonged anorexia)
• Altered internal balance (metabolic alkalosis)

Question 4

Causes of hyperkalemia

Answer 4

Altered external balance