What labs do you order for a hypertensive emergency and what do you look for?

Laboratory Evaluation in Hypertensive Emergency

In hypertensive emergency, a comprehensive laboratory panel should include hemoglobin, platelets, creatinine, sodium, potassium, lactate dehydrogenase (LDH), haptoglobin, urinalysis for protein, and urine sediment to assess target organ damage and guide management. 1

Definition and Clinical Context

Hypertensive emergency is defined as severe blood pressure elevation (>180/120 mmHg) with evidence of new or worsening target organ damage 1. This condition requires immediate intervention to prevent progressive organ failure, with a 1-year mortality rate exceeding 79% if left untreated 2.

Essential Laboratory Tests

Basic Laboratory Panel

• Complete blood count (hemoglobin, platelets) to assess for evidence of microangiopathic hemolytic anemia 1
• Basic metabolic panel including creatinine, sodium, and potassium to evaluate renal function and electrolyte abnormalities 1
• Lactate dehydrogenase (LDH) and haptoglobin to detect hemolysis in hypertensive thrombotic microangiopathy 1
• Urinalysis for protein and urine sediment examination to identify renal damage 1

Additional Testing Based on Clinical Presentation

• Troponins for patients with chest pain to evaluate for acute coronary syndrome 1
• Electrocardiogram (ECG) to assess for cardiac involvement 1
• Chest X-ray for patients with dyspnea to evaluate for pulmonary edema 1
• Brain imaging (CT/MRI) for patients with neurological symptoms to rule out cerebral hemorrhage or stroke 1
• CT-angiography of thorax/abdomen for suspected aortic dissection 1
• Fundoscopy to assess for hypertensive retinopathy 1
• Echocardiogram to evaluate cardiac structure and function when cardiac involvement is suspected 1

What to Look For in Laboratory Results

Evidence of Target Organ Damage

• Elevated creatinine indicating acute kidney injury 1
• Proteinuria and abnormal urine sediment suggesting renal damage 1
• Thrombocytopenia and elevated LDH with decreased haptoglobin indicating thrombotic microangiopathy 1
• Elevated troponins suggesting myocardial injury 1

Indicators of Secondary Hypertension

• Secondary causes can be found in 20-40% of patients with malignant hypertension, warranting appropriate diagnostic workup 1
• Electrolyte abnormalities may suggest endocrine causes of hypertension 1

Organ-Specific Laboratory Evaluation

Renal Assessment

• Creatinine, BUN, electrolytes, and urinalysis to evaluate for acute kidney injury 1
• Significant proteinuria may indicate hypertensive nephropathy 1

Cardiac Assessment

• Troponins and BNP for evidence of myocardial injury or heart failure 1
• ECG to assess for left ventricular hypertrophy or ischemia 1

Neurological Assessment

• If neurological symptoms are present, brain imaging is essential to differentiate between ischemic stroke, hemorrhagic stroke, and hypertensive encephalopathy 1

Hematologic Assessment

• Complete blood count, peripheral smear, LDH, and haptoglobin to identify microangiopathic hemolytic anemia associated with malignant hypertension 1

Clinical Pitfalls to Avoid

• Do not delay laboratory testing in hypertensive emergency - immediate assessment is crucial for appropriate management 1
• Avoid focusing solely on blood pressure numbers; the presence of target organ damage is the critical factor differentiating hypertensive emergency from urgency 2
• Remember that laboratory findings must be interpreted in the clinical context - not all abnormalities are directly related to the hypertensive crisis 1
• Do not overlook the possibility of secondary hypertension, which requires specific diagnostic workup after stabilization 1

By systematically evaluating these laboratory parameters, clinicians can effectively assess the extent of target organ damage, guide appropriate management, and improve outcomes in patients with hypertensive emergencies.