Laboratory Evaluation for Episodes of Hypotension
For episodes of hypotension, a comprehensive laboratory panel should include complete blood count, serum electrolytes, renal function tests, blood glucose, liver function tests, thyroid-stimulating hormone, cardiac biomarkers, and arterial blood gases. 1
Initial Laboratory Tests
Essential Tests
- Complete Blood Count (CBC): Assess for anemia, infection, or other hematologic abnormalities that may cause or contribute to hypotension 1, 2
- Serum Electrolytes: Identify electrolyte imbalances (particularly sodium, potassium, calcium) that may cause or worsen hypotension 1
- Renal Function Tests:
- Blood Glucose: Rule out hypoglycemia as a cause of hypotension 1
- Liver Function Tests: Assess hepatic function and potential causes of hypotension 1
- Thyroid-Stimulating Hormone (TSH): Screen for thyroid dysfunction 1, 3
- Electrocardiogram (ECG): Evaluate for cardiac arrhythmias or ischemia 1, 3
Additional Critical Tests
- Cardiac Biomarkers: Measure troponin to rule out myocardial ischemia 1
- Lactate Levels: Evaluate tissue perfusion and identify potential shock states 1
- Urinalysis: Screen for infection and assess kidney function 3, 1
- Arterial Blood Gases: Assess oxygenation and acid-base status in severe cases 1
Secondary Evaluation Tests
- Coagulation Studies: PT, INR, aPTT, and fibrinogen to evaluate for coagulopathy 1
- Lipid Profile: For cardiovascular risk assessment 3, 1
- Echocardiography: In patients with suspected cardiac dysfunction or unclear etiology 1
Specialized Tests for Suspected Secondary Causes
- Plasma Aldosterone/Renin Ratio: For suspected hypoaldosteronism or adrenal insufficiency 4
- Cortisol Levels: When adrenal insufficiency is suspected 4
- Plasma Metanephrines: If pheochromocytoma is suspected 3
Monitoring Recommendations
- Serial Monitoring: Electrolytes and renal function should be monitored regularly in patients with ongoing hypotension 1
- Orthostatic Vital Signs: Measure blood pressure after 5 minutes of rest in supine position, followed by measurements at 1 and 3 minutes after standing 3, 1
- Volume Status Assessment: Through serial weight measurements, jugular venous pressure estimation, and evaluation for peripheral edema 1
Important Considerations
- Point-of-care testing can provide rapid results for critical parameters (pH, electrolytes, lactate, glucose, hemoglobin) in emergency situations 5
- Don't delay treatment while waiting for laboratory results in severely hypotensive patients 1
- A single hematocrit measurement has low sensitivity for detecting significant hemorrhage 1
- Consider secondary causes of hypotension in patients with persistent or recurrent episodes, particularly endocrine disorders 4
By systematically evaluating these laboratory parameters, clinicians can identify the underlying cause of hypotension and guide appropriate management strategies to improve patient outcomes.