What are the characteristic laboratory findings on a comprehensive metabolic panel (CMP) in an adrenal crisis?

Laboratory Findings in Adrenal Crisis on Comprehensive Metabolic Panel

The characteristic laboratory findings on a comprehensive metabolic panel (CMP) in adrenal crisis include hyponatremia, hyperkalemia, increased creatinine due to prerenal renal failure, hypoglycemia (especially in children), and sometimes mild hypercalcemia. 1

Electrolyte Abnormalities

• Hyponatremia is present in approximately 90% of newly presenting cases, though serum sodium levels may be only marginally reduced 1
• Hyperkalemia is found in approximately 50% of patients at diagnosis, caused by aldosterone deficiency, impaired glomerular filtration, and acidosis 1
• Important exception: In the presence of severe vomiting, patients may paradoxically present with hypokalaemia and alkalosis rather than the expected hyperkalemia 1
• Mild to moderate hypercalcemia occurs in 10-20% of patients at presentation 1

Other Laboratory Abnormalities

• Increased creatinine and BUN due to prerenal renal failure from volume depletion 1
• Hypoglycemia is common in children but less frequent in adults 1, 2
• Metabolic acidosis may be present due to impaired renal function and aldosterone deficiency 1
• Elevated liver transaminases can occur in some patients 1
• Anemia, mild eosinophilia, and lymphocytosis may also be present 1

Hormonal Findings (Not Part of Standard CMP)

• Serum cortisol is typically below the normal range 1
• Plasma ACTH level is markedly elevated in primary adrenal insufficiency 1
• Plasma renin activity (PRA) is increased 1
• Serum aldosterone and dehydroepiandrosterone sulfate (DHEAS) levels are low 1

Clinical Context

• These laboratory abnormalities should raise suspicion of adrenal crisis in patients presenting with unexplained collapse, hypotension, vomiting, or diarrhea 1
• Treatment should never be delayed by diagnostic procedures when adrenal crisis is suspected 1, 2
• Initial treatment includes immediate IV hydrocortisone 100 mg bolus and rapid intravenous administration of 0.9% saline (1 L over an hour) 1, 2

Common Pitfalls

• Relying solely on the classic combination of hyponatremia and hyperkalemia for diagnosis is unreliable, as potassium may be normal in many cases 1
• In patients with severe vomiting, the expected hyperkalemia may be absent or even reversed to hypokalemia 1
• Waiting for laboratory confirmation before initiating treatment can be fatal - treatment should begin immediately upon clinical suspicion 1, 2
• Failure to recognize that adrenal crisis may be the first presentation of previously undiagnosed adrenal insufficiency 3

Diagnostic Approach

• In suspected acute adrenal insufficiency, serum cortisol <250 nmol/L with increased ACTH is diagnostic of primary adrenal insufficiency 1
• Serum cortisol <400 nmol/L with increased ACTH during acute illness raises strong suspicion of primary adrenal insufficiency 1
• Blood for diagnostic testing (cortisol, ACTH, electrolytes, glucose) should be drawn before treatment, but treatment must not be delayed waiting for results 1, 2