What is a hypertensive emergency?

Definition of Hypertensive Emergency

A hypertensive emergency is defined as severely elevated blood pressure (typically >180/120 mmHg) associated with evidence of new or worsening acute hypertension-mediated organ damage requiring immediate BP reduction to prevent progressive organ failure. 1

Key Components of Hypertensive Emergency

Target Organ Damage

Hypertensive emergency is characterized by damage to one or more of the following target organs:

• Brain: Hypertensive encephalopathy, cerebral hemorrhage, acute ischemic stroke
• Heart: Acute coronary syndrome, acute left ventricular failure with pulmonary edema
• Blood vessels: Aortic dissection/aneurysm
• Kidneys: Acute renal failure
• Eyes: Advanced retinopathy (hemorrhages, cotton wool spots, papilledema)
• Microvasculature: Thrombotic microangiopathy 1

Specific Clinical Presentations

1. Malignant hypertension: Severe BP elevation (commonly >200/120 mmHg) with advanced bilateral retinopathy (hemorrhages, cotton wool spots, papilledema) 1

2. Hypertensive encephalopathy: Severe BP elevation with neurological manifestations such as lethargy, seizures, cortical blindness, or coma in the absence of other explanations 1

3. Hypertensive thrombotic microangiopathy: Severe BP elevation with hemolysis and thrombocytopenia that improves with BP-lowering therapy 1

4. Other presentations: Severe BP elevation associated with:

   • Cerebral hemorrhage
   • Acute ischemic stroke
   • Acute coronary syndrome
   • Cardiogenic pulmonary edema
   • Aortic dissection
   • Eclampsia and severe preeclampsia 1

Distinction from Hypertensive Urgency

It's important to distinguish hypertensive emergency from hypertensive urgency:

• Hypertensive urgency: Severely elevated BP (>180/120 mmHg) without evidence of acute or impending target organ damage or dysfunction 1
• These patients typically do not require hospitalization and can be managed with oral antihypertensive therapy 1, 2

Management Principles

Hypertensive emergencies require:

1. Immediate admission to an intensive care unit for continuous BP monitoring and parenteral administration of appropriate antihypertensive agents 1

2. Controlled BP reduction:

   • For compelling conditions (aortic dissection, severe preeclampsia/eclampsia, pheochromocytoma crisis): Reduce SBP to <140 mmHg during the first hour and to <120 mmHg in aortic dissection
   • For other conditions: Reduce BP by no more than 25% within the first hour, then to 160/100 mmHg within 2-6 hours, and cautiously to normal over 24-48 hours 1, 3

3. Choice of medication based on the specific type of organ damage 1, 4

Common Pitfalls to Avoid

• Excessive BP reduction: Can precipitate renal, cerebral, or coronary ischemia due to altered autoregulation 1, 3
• Inappropriate medication selection: Short-acting nifedipine is no longer considered acceptable in the initial treatment of hypertensive emergencies 1
• Failure to identify secondary causes: Secondary causes can be found in 20-40% of patients with malignant hypertension and should be investigated 1

Clinical Implications

The mortality rate associated with untreated hypertensive emergencies is extremely high, with a 1-year death rate >79% and median survival of only 10.4 months if left untreated 1. Therefore, prompt recognition and appropriate management are critical to improving outcomes.