Fluid and Electrolyte Balance

By VeriScorePrep Team · 6 min

Fluid and electrolyte disturbances are common, often iatrogenic, and frequently tested because they endanger the heart and brain.

Sodium

• Hyponatremia (<135 mEq/L): confusion, headache, nausea, seizures. Severe hyponatremia corrected too fast causes osmotic demyelination. Treat slowly with fluid restriction or hypertonic saline only for severe symptoms.
• Hypernatremia (>145 mEq/L): thirst, agitation, dry mucous membranes, restlessness. Treat the cause and correct slowly with free water; rapid correction risks cerebral edema.

Potassium

• Hypokalemia (<3.5 mEq/L): weakness, cramps, U waves on ECG, arrhythmias. Common with diuretics and GI loss. Replace orally when possible; IV no faster than 10 mEq/hr through a central line for severe.
• Hyperkalemia (>5.0 mEq/L): peaked T waves, widened QRS, bradycardia — can progress to cardiac arrest. Treat: calcium to stabilize the myocardium, insulin+glucose to shift K into cells, albuterol, bicarbonate for acidosis, and removal via dialysis or GI binders.

Magnesium

Hypomagnesemia often accompanies hypokalemia and must be corrected first; otherwise the potassium will not normalize. Monitor deep tendon reflexes during IV replacement — depressed reflexes signal toxicity.

The general rule: correct slowly unless the airway, heart, or brain is acutely at risk.