Major intracellular cation (only 2% circulates in plasma), single most important analyte in terms of an abnormality being immediately life threatening
Reference value for potassium: 3.5-5.2 mmol/L
Factors affecting potassium levels
Hemolysis
Muscular activity
Prolonged contact of serum and red cells
Prolonged tourniquet application
High bicarbonate levels
Causes of hyperkalemia
Decreased renal excretion
Extracellular shift
Increased intake
Artifactual
Causes of hypokalemia
Gastrointestinal loss
Intracellular shift
Renal loss
Magnesium
Second most abundant intracellular cation, 4th most abundant cation, essential cofactor of more than 300 enzymes, involved in cardiovascular and neuromuscular functions
Reference value for magnesium: 1.2-2.1 mEq/L
Forms of magnesium
Free or ionized (55%)
Complexed with ions (15%)
Bound to proteins (30%)
Causes of hypermagnesemia
Decreased excretion
Increased intake
Causes of hypomagnesemia
Decreased intake
Decreased absorption
Increased excretion
Chloride
Major extracellular anion (counterpart of Na in extracellular fluid), promotes maintenance of osmolality, blood volume and electric neutrality, only anion to serve as an enzyme activator
Reference value for chloride: 98-107 mmol/L
Factors affecting chloride levels
Hemolysis
Reduced intake
Increased excretion
Bicarbonate
2nd most abundant anion in the ECF, accounts for 90% of total CO2 at physiologic pH, buffers excess hydrogen by combining with acid, major component in buffering system of blood
Reference value for bicarbonate: 21-28 mEq/L (venous blood plasma or serum)
Calcium
Present almost exclusively in the plasma, involved in blood coagulation, enzyme activity, excitability of skeletal and cardiac muscle, maintenance of BP