What laboratory tests should be ordered for a patient in cardiogenic shock?

Laboratory Tests for Cardiogenic Shock

Order serial measurements of cardiac biomarkers (troponin), lactate, renal function (BUN/creatinine), hepatic biomarkers, electrolytes, complete blood count, and arterial blood gases immediately upon suspicion of cardiogenic shock. 1, 2

Essential Initial Laboratory Panel

The following tests should be obtained immediately in all patients with suspected cardiogenic shock:

Cardiac Biomarkers

• Cardiac troponin to assess for acute myocardial injury/infarction, which is the most common cause of cardiogenic shock 1, 2
• Troponin elevation guides the need for urgent coronary angiography within 2 hours 3, 2

Perfusion Markers

• Serum lactate is mandatory—levels >2 mmol/L indicate tissue hypoperfusion and are part of the diagnostic criteria for cardiogenic shock 1, 4
• Lactate should be measured every 2-4 hours during the acute phase; normalization within 24 hours correlates with improved survival 3, 2
• Mixed venous oxygen saturation (SvO₂) or central venous oxygen saturation (ScvO₂) should be measured—SvO₂ <65% or ScvO₂ <70% indicates inadequate tissue perfusion 1, 3, 4

Renal Function

• Blood urea nitrogen (BUN) and creatinine must be measured daily to monitor end-organ dysfunction 1
• Oliguria (urine output <30 mL/hour) is a clinical sign of hypoperfusion, but laboratory confirmation of renal function is essential 1, 3, 4

Hepatic Function

• Hepatic biomarkers (AST, ALT, bilirubin) should be obtained to assess for hepatic hypoperfusion and shock liver 1
• Concomitant hepatic dysfunction may prolong the action of vasoactive medications, particularly in older adults 1

Electrolytes and Metabolic Status

• Electrolytes (sodium, potassium, chloride, bicarbonate) should be measured daily 1
• Arterial blood gases to assess for metabolic acidosis, which is a sign of end-organ hypoperfusion 1, 4
• Respiratory acidosis may indicate need for intubation and mechanical ventilation 1

Hematologic Studies

• Complete blood count (CBC) to assess for anemia, infection, or other hematologic abnormalities 1

Serial Monitoring Strategy

Repeat laboratory measurements daily (at minimum) to monitor response to therapy and detect progression to worsening stages of shock. 1

• Lactate should be measured every 2-4 hours initially until normalized 3, 2
• Renal function and electrolytes require daily monitoring at minimum 1
• Cardiac biomarkers should be trended to assess for ongoing myocardial injury 1

Critical Pitfalls to Avoid

• Do not rely solely on blood pressure for diagnosis—tissue hypoperfusion must be documented through laboratory markers (lactate >2 mmol/L, metabolic acidosis, SvO₂ <65%) as hypotension alone is insufficient for the diagnosis of cardiogenic shock 1, 4
• Do not delay laboratory assessment—early recognition through biomarkers is essential for timely intervention and improved outcomes 2, 5
• Recognize that reduced metabolism and clearance of medications can occur with renal or hepatic dysfunction, particularly in older adults, requiring careful attention to drug dosing 1

Integration with Other Diagnostic Modalities

While laboratory tests are essential, they must be obtained concurrently with:

• 12-lead ECG to identify acute coronary syndrome 1, 2
• Echocardiography to confirm cardiac dysfunction and identify mechanical complications 1, 2
• Continuous hemodynamic monitoring with arterial line placement 1, 3, 2