Hypertensive Emergency and Urgency
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Direct answer
Hypertensive emergency is severe blood pressure elevation with acute target-organ damage, requiring controlled intravenous lowering in a monitored setting, whereas hypertensive urgency is severe elevation without such damage that is managed with oral drugs over hours to days. In an emergency, mean arterial pressure should fall by no more than about 25 per cent within the first hour, because abrupt drops can cause cerebral, coronary or renal hypoperfusion.
What you must remember
- Threshold: severe elevation is conventionally systolic above 180 or diastolic above 120 mmHg, but emergency is defined by new or progressive target-organ damage, not the number alone.
- Target-organ damage: hypertensive encephalopathy, acute heart failure with pulmonary oedema, acute coronary syndrome, aortic dissection, acute stroke, acute kidney injury, pre-eclampsia or eclampsia, and catecholamine crisis.
- Safe lowering: reduce mean arterial pressure by no more than 25 per cent in the first hour, then aim for about 160 over 100 mmHg over two to six hours and normal values over 24 to 48 hours.
- Aortic dissection: beta blockade first, with esmolol or labetalol, to reduce shear stress, then a vasodilator such as nitroprusside or nicardipine; systolic target 100 to 120 mmHg with heart rate below 60.
- Acute heart failure: intravenous nitroglycerin is first-line, with nitroprusside for refractory pulmonary oedema.
- Pregnancy: labetalol, hydralazine or nifedipine lower pressure, magnesium sulphate treats seizures, and delivery is the definitive treatment.
- Ischaemic stroke: pressure is left alone unless it exceeds about 220 over 120 mmHg, and thrombolysis requires pressure below 185 over 110 mmHg.
- Special crises: phentolamine for pheochromocytoma crisis; benzodiazepines for cocaine, with beta blockers avoided alone because alpha effects go unopposed.
A worked scenario with headache and confusion
A 45-year-old man presents with blood pressure 230 over 130 mmHg, severe headache, confusion and papilledema. The presentation is hypertensive encephalopathy, an emergency. The first steps are the same as for any critical patient: airway, breathing and circulation, cardiac monitoring, intravenous access and urgent CT head to exclude haemorrhage, because a haemorrhagic stroke changes the target. Intravenous labetalol, given as a bolus followed by infusion, or nicardipine, is the usual choice, titrated to bring mean arterial pressure down by about a quarter within the first hour.
Neurological observations continue at frequent intervals, since over-rapid lowering can precipitate cerebral hypoperfusion and worsen the very encephalopathy being treated. After the first hours, pressure reaches around 160 over 100 mmHg, and oral therapy takes over over the following day or two. Contrast a second patient with sudden tearing chest pain and a pulse deficit: suspected aortic dissection, so beta blockade comes before any vasodilator, reducing the force of ventricular contraction and shear stress on the aortic wall. The difference between the two scenarios is the organ at risk, and the drug follows the organ.
Where the exam tries to catch you
The most common error is treating hypertensive urgency with intravenous nitroglycerin or a sublingual short-acting calcium channel blocker. Oral agents suit urgency, and precipitous falls from sublingual nifedipine are a recognised hazard. Examiners also test the aortic dissection rule: giving a vasodilator alone before beta blockade is wrong, because reflex tachycardia increases shear force.
A second trap is prolonged nitroprusside. It releases cyanide, so infusion beyond a few days or in renal impairment needs thiocyanate monitoring. In Indian district hospitals where nitroprusside is unavailable, nicardipine or labetalol are the usual substitutes, and the viva answer names the drug by scenario rather than by familiarity.
Frequently asked questions
What blood pressure threshold defines hypertensive emergency?
Severe elevation is conventionally above 180 over 120 mmHg, but hypertensive emergency requires acute target-organ damage in addition to that level. Without organ injury the same pressure is classed as hypertensive urgency and managed with oral drugs.
Which drug is first-line in suspected aortic dissection with hypertension?
Beta blockade with esmolol or labetalol comes first to reduce heart rate and shear stress on the aortic wall. A vasodilator such as nicardipine or nitroprusside is added afterwards to reach the systolic target of 100 to 120 mmHg.
How quickly should blood pressure be lowered in hypertensive emergency?
Mean arterial pressure should fall by no more than about 25 per cent in the first hour. Pressure is then brought towards 160 over 100 mmHg over two to six hours, and normal values are reached over 24 to 48 hours.
Which drug treats catecholamine crisis from pheochromocytoma?
Phentolamine, an alpha blocker, is the standard agent for pheochromocytoma crisis, and beta blockers are given only after adequate alpha blockade. Starting a beta blocker first can cause dangerous rises in pressure through unopposed alpha stimulation.