急診低血鈉的處置

Hyponatremia from Sun YaiCheng

Hyponatremia 定義：[Na⁺] < 135 mEq/L

• Clinical Signs of Hyponatrema: Nausea, vomiting, anorexia, muscle cramps, confusion, and lethargy, and culminate ultimately in seizures and coma. 
• Seizures are quite likely at [Na⁺] of 113 mEq/L or less.

Effects of Hyponatremia on the Brain and Adaptive Responses

Causes of Hyponatremia

Hypertonic Hyponatremia (Osmotic Pressure >295)

• Hyperglycemia
• Mannitol excess
• Glycerol therapy

Isotonic Hyponatremia (Osmotic Pressure 275 to 295)

• Hyperlipidemia
• Hyperproteinemia (e.g., multiple myeloma, Waldenström macroglobulinemia)

Hypotonic Hyponatremia (Osmotic Pressure < 275) 

• Hypovolemic 

Renal

Diuretic use
Salt-wasting nephropathy (renal tubular acidosis, chronic renal failure, interstitial nephritis)
Osmotic diuresis (glucose, urea, mannitol, hyperproteinemia)
Mineralocorticoid (aldosterone) deficiency 

Extrarenal

Volume replacement with hypotonic fluids
GI loss (vomiting, diarrhea, fistula, tube suction)
Third-space loss (e.g., burns, hemorrhagic pancreatitis, peritonitis) 

• Hypervolemic 

Urinary [Na⁺] >20 mEq/L

Renal failure

Urinary [Na⁺] < 20  mEq/L

Congestive heart failure
Nephrotic syndrome  
Cirrhosis

• Euvolemic

Urine [Na+] usually > 20 mEq/L

SIADH
Hypothyroidism (possible increased ADH or deceased glomerular filtration rate)
Pain, stress, nausea, psychosis (stimulates ADH)
Drugs: ADH, nicotine, sulfonylureas, morphine, barbiturates, NSAIDs, acetaminophen, carbamazepine, phenothiazines, tricyclic antidepressants, colchicine, clofibrate, cyclophosphamide, isoproterenol, tolbutamide, vincristine, MAOI.
Water intoxication
Glucocorticoid deficiency
Positive pressure ventilation
Porphyria
Essential (reset osmostat or sick cell syndrome—usually in the elderly)

Total Body [Na⁺] Deficit

= (desired plasma [Na⁺]－measured plasma [Na⁺]) ×TBW

Emergency Treatment of Severe Hyponatremia

• In the ED, there is generally little urgency to address the hyponatremia immediately when [Na+] is 120 mEq/L.
• Urine electrolytes are useful only before beginning treatment and therefore should be collected in the ED. 
• The rise in [Na+] should be no greater than 0.5 to 1.0 mEq/L per hour

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