Treatment

Depends upon the cause and whether total body sodium stores are normal, low or elevated and body water is normal or low.

Rate of correction

• If hyperacute (<12 h), correction can be rapid.

• Otherwise, aim for gradual correction of plasma sodium levels (over 1-3 days), particularly in chronic cases (>2 days' duration), to avoid cerebral oedema through sudden lowering of osmolality. A rate of plasma sodium lowering <0.7 mmol/h has been suggested.

Hypovolaemia

• If hypovolaemia is accompanied by haemodynamic alterations, use colloid initially to restore the circulation. Otherwise, use isotonic saline.

• Artificial colloid solutions consist of hydroxyethyl starches (e.g. Hespan, EloHAES) or gelatins (e.g. Gelofusin, Haemaccel) dissolved in isotonic saline.

Normal total body Na (water loss)

• Water replacement either PO (addition to enteral feed) or as 5% glucose IV. Up to 5l/day may be necessary.

• If cranial diabetes insipidus (CDI): restrict salt and give thiazide diuretics. Complete CDI will require desmopressin (10pg bd intranasally or 1-2pg bd IV) whereas partial CDI may require desmopressin but often responds to drugs that increase the rate of ADH secretion or end-organ responsiveness to ADH, e.g. chlorpropamide, hydrochlorthiazide

• If nephrogenic DI: manage by a low salt diet and thiazides. High dose desmopressin may be effective. Consider removal of causative agents, e.g. lithium, demeclocycline.

Low total body Na (Na and water losses)

• Treat hyperosmolar non-ketotic diabetic crisis, uraemia as appropriate.

• Otherwise consider 0.9% saline or hypotonic (0.45%) saline. Up to 5 l/day may be needed.

Increased total body Na (Na gain)

• Water replacement either PO (addition to enteral feed) or as 5% glucose IV. Up to 5l/day may be necessary.

• In addition, furosemide 10-20 mg IV prn may be necessary.

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