A patient with Addison's disease presents in Addisonian crisis. After initial resuscitation with IV normal saline and hydrocortisone, laboratory results show Na 128 mEq/L. What is the most appropriate further management?

• A Add fludrocortisone 0.1 mg orally immediately
• B Continue IV hydrocortisone; hyponatraemia will correct with adequate glucocorticoid replacement ✓
• C Administer 3% saline to rapidly correct hyponatraemia
• D Add desmopressin to reduce free water loss

Explanation

In Addisonian crisis, hyponatraemia results from mineralocorticoid deficiency (salt wasting) and elevated ADH (due to volume depletion and cortisol deficiency stimulating ADH). IV hydrocortisone at stress doses (100 mg bolus then 50-100 mg q6-8h) has sufficient mineralocorticoid activity at high doses, and volume resuscitation with normal saline corrects the hyponatraemia. Fludrocortisone is added only after transitioning to oral replacement. Hypertonic saline carries risk of osmotic demyelination and is not indicated here. Desmopressin would worsen hyponatraemia.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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