Hypertensive Emergencies

A hypertensive emergency is characterized by a severe elevation in blood pressure (BP), usually >180/120 mmHg, accompanied by acute end-organ damage. This damage may affect the brain, heart, kidneys, or eyes, and requires immediate BP reduction to prevent morbidity and mortality.

Pathophysiology:

Hypertensive emergencies occur due to the failure of autoregulation in the vascular system, leading to abrupt elevations in BP. This results in endothelial injury, increased vascular permeability, and subsequent end-organ ischemia or damage.

Common Causes:

• Primary Hypertension: Uncontrolled or poorly managed chronic hypertension.
• Secondary Hypertension: Caused by conditions such as pheochromocytoma, renal artery stenosis, eclampsia, or hyperaldosteronism.
• Drug-Related Causes: Cocaine, amphetamines, or withdrawal from antihypertensive medications.
• Other Causes: Acute glomerulonephritis, autonomic dysreflexia (in spinal cord injury), or head trauma.

Clinical Presentation:

1. Neurological Symptoms: Severe headache, confusion, altered consciousness, seizures, or visual disturbances (signs of hypertensive encephalopathy, stroke, or intracerebral hemorrhage).
2. Cardiac Symptoms: Chest pain, dyspnea, or palpitations (associated with myocardial infarction, heart failure, or aortic dissection).
3. Renal Symptoms: Oliguria or hematuria (signs of acute kidney injury).
4. Ophthalmic Symptoms: Blurred vision or retinal hemorrhage (indicative of hypertensive retinopathy).

Diagnostic Approach:

Blood Pressure Measurement: Confirm severe BP elevation in multiple readings in different settings.

Laboratory Investigations:

• Electrolytes, Urea, Creatinine: To assess renal function.
• Complete Blood Count (CBC): To check for hemolysis or thrombocytopenia.
• Cardiac Enzymes (e.g., Troponin): If myocardial infarction is suspected.
• Urinalysis: To detect proteinuria or hematuria.

Imaging:

• Chest X-ray: For signs of heart failure or aortic dissection.
• Head CT/MRI: If neurological symptoms suggest stroke or hemorrhage.
• ECG: To detect ischemic changes or left ventricular hypertrophy.
• Echocardiography: For assessing left ventricular function or aortic root dilation.

Ophthalmologic Examination: To check for hypertensive retinopathy.

Management:

1. Goals of Treatment:

• Initial BP Reduction: Reduce mean arterial pressure (MAP) by 20-25% within the first hour, except in certain conditions (e.g., aortic dissection, eclampsia, or pheochromocytoma), where more rapid reduction is necessary.
• Subsequent Reduction: Target BP of 160/100-110 mmHg over the next 2-6 hours, then gradual reduction to normal over the next 24-48 hours.
• Exceptions: In ischemic stroke, do not lower BP unless it is >185/110 mmHg for thrombolysis candidates or >220/120 mmHg in non-thrombolysis cases.

2. Intravenous (IV) Antihypertensive Agents:

The choice of medication depends on the specific end-organ damage present.

Neurological Emergencies (e.g., Hypertensive Encephalopathy, Stroke)

• Labetalol: 20 mg IV bolus over 2 minutes, followed by 40-80 mg every 10 minutes (max 300 mg), or a continuous infusion at 1-2 mg/min.
• Nicardipine: Start at 5 mg/hour IV infusion, titrate up by 2.5 mg/hour every 5-15 minutes (max 15 mg/hour).
• Clevidipine: Start at 1-2 mg/hour, double every 90 seconds to a maximum of 32 mg/hour.

Cardiac Emergencies (e.g., Acute Coronary Syndrome, Heart Failure):

• Nitroglycerin: 5-10 mcg/min IV infusion, titrate to achieve desired effect (mainly for acute coronary syndrome).
• Sodium Nitroprusside: 0.25-0.5 mcg/kg/min, titrated up to a maximum of 10 mcg/kg/min (used cautiously due to risk of cyanide toxicity).
• Esmolol: Initial bolus of 500 mcg/kg over 1 minute, followed by 50-200 mcg/kg/min infusion.

Aortic Dissection:

• Esmolol: As above, to rapidly reduce heart rate (<60 bpm) and BP.
• Labetalol: 20 mg IV bolus, followed by continuous infusion if required.
• Add Vasodilator (e.g., Sodium Nitroprusside) if additional BP reduction is needed.

Renal Emergencies (e.g., Acute Kidney Injury):

• Fenoldopam: 0.1-0.3 mcg/kg/min IV infusion, titrate every 15 minutes.
• Nicardipine: 5 mg/hour, titrate up as needed. e. Eclampsia/Pre-eclampsia:
• Labetalol: 20 mg IV bolus, titrate every 10 minutes.
• Hydralazine: 5-10 mg IV bolus, repeated every 20-30 minutes.
• Magnesium Sulfate: For seizure prophylaxis (4-6 g IV loading dose, followed by 1-2 g/hour).

3. Non-Pharmacological Interventions:

• Supportive Care: Monitor vital signs, cardiac function, urine output, and neurologic status.
• Oxygen Therapy: For patients with respiratory distress or heart failure.

Complications of Hypertensive Emergencies:

• Neurological: Stroke, intracerebral hemorrhage, hypertensive encephalopathy.
• Cardiac: Myocardial infarction, heart failure, aortic dissection.
• Renal: Acute kidney injury, nephrosclerosis.
• Ophthalmic: Retinal detachment, vision loss.

Special Considerations:

• Pregnancy-Related Hypertension: Special management protocols are required for pre-eclampsia and eclampsia, with drugs like labetalol, nifedipine, and hydralazine preferred.
• Pheochromocytoma Crisis: Use alpha-blockers (e.g., phentolamine) before beta-blockers to avoid unopposed alpha stimulation.