What labs should be drawn during an Addisonian crisis?

Laboratory Testing During Addisonian Crisis

Draw blood for cortisol, ACTH, and basic metabolic panel (sodium, potassium, creatinine, glucose) immediately before administering hydrocortisone, but never delay treatment to wait for results. 1, 2, 3

Essential Labs to Draw Immediately

Hormonal Studies (Priority)

• Serum cortisol - A level <250 nmol/L with elevated ACTH during acute illness is diagnostic of primary adrenal insufficiency 2, 4
• Plasma ACTH - Markedly elevated in primary adrenal insufficiency; helps distinguish primary from secondary causes 2, 3, 4
• These samples must be secured before giving hydrocortisone if possible, though treatment takes absolute priority 1

Electrolytes and Metabolic Panel

• Sodium - Hyponatremia is present in approximately 90% of cases, though levels may be only marginally reduced 2, 3, 4
• Potassium - Hyperkalemia occurs in only 50% of cases, so its absence does not exclude the diagnosis 2, 3, 4
• Creatinine and BUN - Elevated due to prerenal renal failure from volume depletion 3, 4
• Glucose - Hypoglycemia is common in children but less frequent in adults 3, 4

Additional Useful Labs

• Calcium - Mild to moderate hypercalcemia occurs in 10-20% of patients 3, 4
• Arterial blood gas - May show metabolic acidosis due to impaired renal function and aldosterone deficiency 3, 4

Critical Clinical Pitfall

The absence of hyperkalemia does NOT rule out Addisonian crisis - it is present in only half of cases, while hyponatremia is far more common at 90%. 3 However, if vomiting is severe, patients may paradoxically present with hypokalemia and alkalosis rather than the expected hyperkalemia. 4

Etiologic Workup (After Stabilization)

Once the patient is stabilized, determine the underlying cause: 1, 3

• 21-hydroxylase autoantibodies (21OH-Ab) - Positive in autoimmune Addison disease, which accounts for approximately 85% of cases in Western Europe 1, 3
• CT scan of adrenals - If 21OH-Ab is negative, evaluate for hemorrhage, tumor, tuberculosis, or infiltrative processes 1, 3
• Very long chain fatty acids (VLCFA) - Test in males to screen for adrenoleukodystrophy 1
• Plasma renin activity - Increased in primary adrenal insufficiency 4
• Serum aldosterone and DHEAS - Low in primary adrenal insufficiency 4

Diagnostic Thresholds

• Cortisol <250 nmol/L with elevated ACTH during acute illness is diagnostic 2, 3, 4
• Cortisol <400 nmol/L with elevated ACTH during acute illness raises strong suspicion 2
• Note: Approximately 10% of patients with primary adrenal insufficiency may present with normal cortisol concentrations in the presence of clearly elevated ACTH, so clinical context is paramount 5

Treatment Protocol

While awaiting lab results, immediately administer: 1, 3

• Hydrocortisone 100 mg IV bolus
• 0.9% isotonic saline at 1 liter over the first hour
• Continue hydrocortisone 100 mg IV every 6-8 hours until recovered