ICU · Cardiovascular / hypertension
Hypertensive Emergencies
Also known as Hypertensive emergency · Hypertensive crisis · Hypertensive encephalopathy · Malignant hypertension · Hypertensive urgency · Labetalol · Nicardipine · Nitroprusside · Posterior reversible encephalopathy syndrome · PRES
A hypertensive emergency is severe blood pressure elevation with acute target-organ damage (encephalopathy, stroke, intracerebral haemorrhage, ACS, pulmonary oedema, aortic dissection, acute kidney injury, or eclampsia) — it requires IV therapy and ICU monitoring. A hypertensive urgency is severe BP without target-organ damage — it requires oral therapy and follow-up. The principle is a controlled, monitored BP reduction: lower the MAP by 10-20 per cent in the first hour, then to 160/100 within 2-6 hours, then gradually to baseline. Do NOT crash the BP — the chronic hypertensive's autoregulation curve is shifted right, and a sudden reduction causes cerebral, coronary, and renal hypoperfusion. The exceptions are aortic dissection (rapid to SBP 100-120) and eclampsia (SBP below 160). The drugs: labetalol, nicardipine, nitroprusside, GTN, and hydralazine.
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Overview & definition
The distinction is critical:[1]
- Hypertensive emergency — severe BP elevation (typically SBP over 180 and/or DBP over 120) with acute target-organ damage. Requires IV therapy and ICU monitoring.
- Hypertensive urgency — severe BP elevation without target-organ damage. Requires oral therapy and close follow-up — NOT an ICU emergency.
The absolute BP number is less important than the presence of target-organ damage — a patient with a BP of 220/130 and a normal examination has urgency; a patient with a BP of 180/120 and an encephalopathy has an emergency.[1]
The target-organ damage presentations
The type of target-organ damage determines the drug and the BP target:[1]
- Hypertensive encephalopathy — headache, confusion, visual disturbance, seizures, coma; the MRI shows PRES (posterior reversible encephalopathy syndrome).
- Acute ischaemic stroke — do NOT aggressively lower the BP unless it is over 220/120 (or over 185/110 if for thrombolysis).
- Intracerebral haemorrhage — controlled BP reduction to SBP about 140.
- ACS — reduce the BP to reduce the afterload and the myocardial oxygen demand.
- Acute pulmonary oedema — reduce the preload (GTN, furosemide) and the afterload.
- Aortic dissection — rapid BP reduction to SBP 100-120 (the most aggressive target — the wall stress must be reduced immediately).
- Acute kidney injury / malignant hypertension — proteinuria, haematuria, microangiopathic haemolysis.
- Pre-eclampsia / eclampsia — magnesium sulphate, labetalol or hydralazine; SBP below 160.[1]
The management principle — controlled reduction
Lower the BP in a controlled, monitored way — NOT a sudden reduction:[1]
- In chronic hypertension, the cerebral, coronary, and renal autoregulation curves are shifted to the right — the organs are accustomed to the higher pressures, and a sudden reduction to a "normal" BP causes hypoperfusion (a cerebral infarction, a coronary ischaemia, or an AKI).
- The standard target: reduce the MAP by 10-20 per cent in the first hour, then to about 160/100 within 2-6 hours, then gradually to baseline over 24-48 hours.
- The exceptions (rapid reduction):
- Aortic dissection — SBP to 100-120 immediately.
- Eclampsia / severe pre-eclampsia — SBP below 160.
- Intracerebral haemorrhage — SBP to about 140.[1]
The IV drugs
| Drug | Mechanism | Best for | Notes |
|---|---|---|---|
| Labetalol | Alpha + beta-blocker | Most emergencies; pregnancy; stroke | Versatile; first-line |
| Nicardipine | DHP calcium channel blocker | Stroke; renal emergencies; encephalopathy | Titratable; no tachycardia |
| Nitroprusside | Direct vasodilator | Aortic dissection (after a beta-blocker); refractory | Cyanide toxicity with prolonged use |
| GTN | Venous + arterial vasodilator | ACS; pulmonary oedema | Reduces the preload and the afterload |
| Hydralazine | Direct vasodilator | Pregnancy (pre-eclampsia) | Reflex tachycardia |
| Clevidipine | Ultra-short DHP CCB | Any; titratable | Very rapid onset and offset |
| Esmolol | Ultra-short beta-blocker | Aortic dissection (first-line) | Rapid onset and offset |
The aortic dissection rule: always give a beta-blocker first (esmolol or labetalol) to control the heart rate and the contractile force, THEN the vasodilator (nitroprusside or nicardipine). Giving a vasodilator without a beta-blocker causes a reflex tachycardia that increases the sheer stress on the dissection flap and worsens the dissection.[1]
[1]
Red flags
Cerebral autoregulation — the central physiological principle
The single concept that governs every blood-pressure decision in a hypertensive emergency is the autoregulation curve — and its rightward shift in chronic hypertension.[4]
Blood-pressure reduction targets — scenario by scenario
The default target for most neurological and renal emergencies is the staged, gradual reduction; the exceptions demand aggressive or permissive strategies. The target is dictated by the specific emergency, never by habit.[1][2]
BP reduction targets by clinical scenario — the bedside prescription
| Scenario | First hour | Next 2-6 hours | Rationale / evidence |
|---|---|---|---|
| Most emergencies (default) | Reduce MAP by 10-20 per cent | Gradually to ~160/100 mmHg | Protect the rightward-shifted autoregulation curve; avoid cerebral/coronary/renal hypoperfusion.[4] |
| Hypertensive encephalopathy | Reduce MAP by 10-20-25 per cent | To ~160/100 over 2-6 h | Restore autoregulation, relieve PRES; watch the GCS for over-shoot (a falling GCS = you have crossed the floor). |
| Acute intracerebral haemorrhage | SBP to 140 mmHg (within 1 h) | Maintain SBP 130-150 | INTERACT2: intensive lowering (SBP <140) produced a significant ordinal shift to better functional outcome; ATACH2 confirmed that going lower (110-139) added no benefit and more renal harm. Target 130-150.[5][6] |
| Acute ischaemic stroke (not for thrombolysis) | Do NOT lower unless >220/120 | Permissive hypertension | The ischaemic penumbra depends on collateral flow driven by systemic pressure; lowering BP worsens the infarct. |
| Acute ischaemic stroke (for thrombolysis) | Lower to <185/110 before lysis | Maintain <180/105 for 24 h | Thrombolysis eligibility requirement; permissive thereafter. |
| Aortic dissection (EXCEPTION — rapid) | SBP to 100-120 mmHg rapidly; HR 60-80 | Maintain 100-120 | Reduce dP/dt (the rate of pressure rise) to halt propagation; beta-blocker FIRST, then vasodilator. |
| Pre-eclampsia / eclampsia | SBP <160 / DBP <110 | Maintain | Prevent maternal stroke (the killer); magnesium FIRST, then BP control. |
| ACS / acute pulmonary oedema | Prompt reduction to relieve ischaemia/congestion | Titrate to symptoms | Nitroglycerin preferred; do not drop coronary perfusion. |
| Phaeochromocytoma crisis | Controlled reduction after alpha-blockade | Titrate | Alpha-blockade first to avoid unopposed alpha stimulation. |
| Acute kidney injury / malignant HTN | MAP -10-20 per cent, gradual | Gradual to 160/100 | Avoid further ischaemic insult; no ACE inhibitors acutely. |
IV antihypertensive agents — pharmacology in depth
The choice of agent is dictated by the target organ, the scenario, and the patient's comorbidity — not by habit. The STAT registry documented that agents were frequently chosen for convenience, contributing to over-rapid or inappropriate reductions; modern practice is deliberately scenario-driven.[7]
IV antihypertensive agents — class, dosing, onset, indications, cautions
| Agent | Class / mechanism | Dosing | Onset / duration | Best indications | Key cautions |
|---|---|---|---|---|---|
| Labetalol | Combined alpha-1 (non-selective) + non-selective beta-blocker (alpha:beta ~1:7 IV) | Bolus 10-20 mg over 2 min, repeat q10 min (max 300 mg); or infusion 1-2 mg/min (up to 8 mg/min) | 2-5 min / 2-4 h | The versatile default: encephalopathy, pregnancy (pre-eclampsia), post-stroke, aortic dissection (with esmolol), post-operative | Avoid in severe asthma/COPD, heart block, bradycardia, severe acute LV failure; lowers HR (helpful in dissection) |
| Nicardipine | Dihydropyridine calcium-channel blocker (arteriolar vasodilator) | Infusion 5 mg/h, titrate by 2.5 mg/h q5 min (max 15 mg/h) | 5-15 min / 4-6 h (post-cessation) | Smooth and titratable — preferred for ICH, renal impairment, stroke, encephalopathy | Caution in advanced heart failure (negative inotropy at high dose); phlebitis at peripheral line |
| Hydralazine | Direct arteriolar smooth-muscle relaxant | Bolus 5-10 mg IV q20-30 min; or infusion 0.5-10 mg/h | 10-20 min / 3-6 h (unpredictable) | Pregnancy (pre-eclampsia/eclampsia) — long-established safety record | Reflex tachycardia; increases ICP (avoid in neurological emergencies); unpredictable onset/duration — hard to titrate; lupus-like syndrome (chronic) |
| Sodium nitroprusside | Potent arterial + venous vasodilator (NO donor) | Infusion 0.3-3 mcg/kg/min (max 10 mcg/kg/min) | Seconds / 1-2 min | Historically the "gold standard"; now AVOIDED — reserve for refractory dissection/phaeochromocytoma | Cyanide/thiocyanate toxicity (renal failure, >48 h, high dose); increases ICP; coronary steal; mortality signals |
| Phentolamine | Non-selective alpha-1/alpha-2 antagonist | Bolus 1-5 mg IV, repeat; infusion 0.2-0.5 mg/min | 1-2 min / 10-30 min | Phaeochromocytoma crisis (the definitive alpha-blocker); cocaine (refractory) | Reflex tachycardia; flush; nasal stuffiness; follow with beta-blocker once alpha-blockade established |
| Esmolol | Ultra-short cardioselective beta-1 blocker | Bolus 500 mcg/kg, infusion 50-300 mcg/kg/min | 1-2 min / 10-20 min | Aortic dissection (titratable beta-blockade to HR 60-80, FIRST, before vasodilation) | Asthma, heart block, bradycardia; hypotension |
| Nitroglycerin (GTN) | Venodilator (preload) + mild arteriolar (afterload); coronary vasodilator | Infusion 5-200 mcg/min | 2-5 min / 5-10 min | ACS, acute pulmonary oedema (hypertensive ADHF) | Headache; tachyphylaxis; weak arteriolar dilator — not first-line for pure BP crises; PDE-5 interaction |
| Clevidipine | Ultra-short-acting dihydropyridine CCB (arteriolar) | Infusion 1-2 mg/h, double q90 sec (max 32 mg/h) | 1-2 min / 5-15 min | Ultra-short, exquisite titratability; perioperative, acute severe HTN | Lipid emulsion — avoid in egg/soy allergy, defective lipid metabolism |
| Fenoldopam | Selective DA-1 receptor agonist (arteriolar + renal vasodilator, natriuretic) | Infusion 0.1-1.6 mcg/kg/min | 5-10 min / 10-15 min | Renal-protective profile; AKI/pre-renal impairment | Reflex tachycardia; headache; intraocular pressure rise (avoid glaucoma) |
Scenario → preferred agent(s) → target — the bedside prescription
Emergency → preferred IV agent(s) → first-hour target → avoid
| Emergency | Preferred IV agent(s) | BP target (first hour) | Avoid |
|---|---|---|---|
| Hypertensive encephalopathy / PRES | Nicardipine OR labetalol | MAP -10-20 per cent (to ~160/100 over 2-6 h) | Nitroprusside (raises ICP); rapid normalisation |
| Acute intracerebral haemorrhage | Nicardipine (preferred); labetalol | SBP to 140 (INTERACT2); maintain 130-150 | Nitroprusside; over-rapid drop below 130 (ATACH2 harm) |
| Ischaemic stroke (no thrombolysis) | None unless SBP >220/120 — then labetalol/nicardipine cautiously | Permissive hypertension | Aggressive reduction (worsens infarct) |
| Ischaemic stroke (thrombolysis) | Labetalol or nicardipine | <185/110 before; <180/105 after | Nitroprusside |
| Aortic dissection | Esmolol (or labetalol) FIRST → then nicardipine/nitroprusside | SBP 100-120, HR 60-80 | Vasodilator BEFORE beta-blockade (reflex tachycardia, propagation) |
| ACS / hypertensive pulmonary oedema | Nitroglycerin (+ low-dose loop diuretic); labetalol | Prompt reduction to relieve ischaemia | Nitroprusside (coronary steal); pure beta-blocker in acute LV failure |
| Pre-eclampsia / eclampsia | Labetalol or hydralazine; magnesium FIRST | SBP <160 / DBP <110 | ACE inhibitors (fetotoxic); nitroprusside; sublingual nifedipine |
| Phaeochromocytoma crisis | Phentolamine (alpha) FIRST → then beta-blocker | Controlled reduction | Beta-blocker BEFORE alpha-blockade (unopposed alpha) |
| Cocaine / sympathomimetic | Benzodiazepines first → then phentolamine/nicardipine | Gradual reduction | Pure beta-blockers (unopposed alpha); labetalol debated |
| AKI / malignant HTN | Nicardipine, labetalol, fenoldopam | MAP -10-20 per cent, gradual | Diuretics unless volume-overloaded; ACE inhibitors acutely |
| Post-operative / perioperative | Clevidipine, nicardipine | Per surgical target | Long-acting oral agents in fasted patient |
Specific emergencies in depth
Hypertensive encephalopathy and PRES
Hypertensive encephalopathy presents with severe headache, nausea, vomiting, visual disturbance (blurred vision, cortical blindness), confusion, seizures, and progression to coma. Fundoscopy shows papilloedema and retinal flame haemorrhages (Keith-Wagener-Barker grade IV retinopathy). The mechanism is breakthrough of the (rightward-shifted) cerebral autoregulation ceiling: at extreme pressures, cerebral resistance vessels are forced open, producing hyperperfusion, blood-brain-barrier disruption, and vasogenic oedema. The MRI signature is posterior reversible encephalopathy syndrome (PRES) — T2/FLAIR white-matter oedema in the parieto-occipital regions, which (true to its name) reverses with controlled BP reduction. Management is nicardipine or labetalol to reduce MAP by 10-20 per cent in the first hour; avoid nitroprusside (raises ICP); treat seizures with IV benzodiazepines then levetiracetam or phenytoin. Symptoms typically resolve within 24-48 h of BP control — failure to improve demands re-imaging for stroke or haemorrhage.[1][4]
Acute intracerebral haemorrhage — INTERACT2 and ATACH2
In spontaneous intracerebral haemorrhage the haematoma expands in the first hours, driven by the arterial pressure, and haematoma growth is the strongest predictor of death and disability. The INTERACT2 trial (Anderson, NEJM 2013, 2,839 patients) randomised ICH patients (SBP 150-220) within 6 h to intensive BP lowering (target SBP <140 within 1 h) versus standard (SBP <180). Intensive lowering did not significantly reduce the primary outcome of death or major disability (52.0 per cent vs 55.6 per cent; odds ratio 0.87, P=0.06), but it DID produce a statistically significant shift in ordinal modified Rankin scores favouring better functional outcome, with no increase in serious adverse events — establishing SBP ~140 mmHg as the target. The subsequent ATACH2 trial (Qureshi, NEJM 2016) refined this: lowering to 110-139 versus 140-179 showed no benefit and more renal adverse events, so the safe target band is SBP 130-150 mmHg, achieved within 1 h using nicardipine (preferred) or labetalol. The earlier dogma ("reduce by 15-20 per cent, never to normal, for fear of the perihaematomal ischaemic penumbra") is superseded by the trial evidence, but the principle of controlled (not precipitous) reduction remains.[5][6]
Acute ischaemic stroke — permissive hypertension
In acute ischaemic stroke, the ischaemic penumbra is perfusion-dependent; collateral flow relies on systemic pressure, so permissive hypertension is the default — do NOT lower the BP unless it exceeds 220/120 mmHg, or unless the patient is receiving thrombolysis (in which case lower to <185/110 beforehand and maintain <180/105 for 24 h). Use labetalol or nicardipine cautiously. Avoid nitroprusside (increases ICP, may worsen cerebral oedema). [1]
Aortic dissection — the rapid-reduction exception
Aortic dissection is the prototypical exception to the gradual-reduction rule: propagation of the dissection flap is driven by the rate of rise of arterial pressure (dP/dt) and the sheer stress on the aortic wall, so the immediate goal is to reduce both the pressure and the impulse. The sequence is critical — beta-blockade FIRST (esmolol or labetalol) to lower heart rate to 60-80/min and blunt dP/dt, THEN an arteriolar vasodilator (nicardipine, or nitroprusside in refractory cases) to bring SBP to 100-120 mmHg. Giving a vasodilator without prior beta-blockade causes reflex tachycardia and an increased dP/dt that can extend the dissection — a classic and lethal error. [1]
Acute coronary syndrome and hypertensive pulmonary oedema
In ACS the goals are to reduce myocardial oxygen demand (afterload and preload), relieve ischaemia, and unload the failing ventricle. Nitroglycerin is the agent of choice (coronary vasodilation + preload reduction + afterload reduction), combined with a low-dose loop diuretic and standard anti-ischaemic therapy (dual antiplatelet, anticoagulation, statin, reperfusion as indicated). In hypertensive acute pulmonary oedema (the warm-wet hypertensive phenotype), nitroglycerin, NIV (which dramatically reduces preload and afterload), and a loop diuretic are combined; nicardipine or clevidipine are alternatives. Avoid nitroprusside (coronary steal) and avoid pure beta-blockade in acute LV failure. [1]
Pre-eclampsia and eclampsia — magnesium FIRST
Pre-eclampsia is new hypertension (BP >140/90) with proteinuria or end-organ dysfunction after 20 weeks' gestation; eclampsia is pre-eclampsia with seizures. The maternal killer is stroke from uncontrolled BP; the fetal imperative is seizure prevention and timely delivery. The Magpie trial (Lancet 2002, >10,000 women) established magnesium sulphate as the standard of care for seizure prophylaxis and treatment in pre-eclampsia/eclampsia.[8]
The management priorities: (1) MAGNESIUM SULPHATE FIRST — it is an anticonvulsant, NOT an antihypertensive. Loading 4-6 g IV over 20 min; maintenance 1-2 g/h. Monitor reflexes, respiratory rate, urine output; the antidote for toxicity is calcium gluconate 10 per cent (10 mL IV). (2) BP control with labetalol or hydralazine to SBP <160 / DBP <110 — the target that prevents maternal stroke. (3) Delivery is the definitive treatment. AVOID ACE inhibitors/ARBs (fetotoxic), nitroprusside (fetal cyanide toxicity), and sublingual nifedipine (precipitous fall, uteroplacental hypoperfusion).[8]
Phaeochromocytoma crisis — alpha before beta
A phaeochromocytoma secretes catecholamines (adrenaline, noradrenaline), presenting with episodic hypertension, throbbing headache, sweating, and palpitations — sometimes provoked by anaesthesia, abdominal palpation, micturition, or certain drugs. The critical management rule: establish ALPHA-blockade FIRST (phentolamine IV acutely — 1-5 mg bolus then infusion; phenoxybenzamine orally for elective pre-operative preparation, titrated over 10-14 days) BEFORE giving ANY beta-blocker. Why? A beta-blocker first blocks beta-2-mediated peripheral vasodilation while leaving alpha-1-mediated vasoconstriction unopposed — producing catastrophic, refractory hypertension, stroke, MI, or aortic dissection. Once alpha-blockade is established, add a beta-blocker to control reflex tachycardia; surgical resection follows adequate blockade. [1]
Cocaine and sympathomimetic-induced crisis
Cocaine and amphetamines provoke a surge of sympathetic outflow, producing hypertension, tachycardia, vasoconstriction, agitation, and a risk of ACS, aortic dissection, and stroke. First-line therapy is BENZODIAZEPINES (diazepam or lorazepam), which calm the central sympathetic surge and lower BP and heart rate. Avoid pure beta-blockers — they leave alpha-mediated vasoconstriction unopposed (the same mechanism as in phaeochromocytoma) and may worsen hypertension and coronary vasoconstriction; add a vasodilator (nitroglycerin for chest pain/ischaemia, phentolamine for refractory hypertension, nicardipine as an alternative). Labetalol (mixed alpha + beta) is debated and generally avoided in pure cocaine toxicity. [1]
Hypertensive urgency — oral agents and outpatient management
Hypertensive urgency is severe BP elevation without acute target-organ damage. It does NOT require ICU admission or IV therapy. The management is oral antihypertensive therapy with a goal of gradual reduction over 24-48 hours, arranged close follow-up (within 24-72 h), and reinstitution or uptitration of the chronic regimen. The danger in urgency is not the high pressure — it is the over-treatment: a precipitous fall from sublingual nifedipine or an unnecessary IV infusion causes the very cerebral or myocardial ischaemia the clinician is trying to prevent.[1][2]
Oral agents for hypertensive urgency — gradual reduction over 24-48 h
| Agent | Class | Dose | Onset / duration | Notes |
|---|---|---|---|---|
| Captopril | ACE inhibitor | 12.5-25 mg PO | 15-30 min / 6-8 h | Short-acting, titratable; watch for AKI in bilateral renal artery stenosis; avoid in pregnancy |
| Labetalol | Alpha + beta-blocker | 200-400 mg PO | 30-120 min / 8-12 h | Useful when tachycardia or migraine coexist; avoid in asthma, heart block |
| Amlodipine | Dihydropyridine CCB | 5-10 mg PO | hours / 24 h+ | Smooth, long-acting; well tolerated; oedema the main side-effect |
| Felodipine | Dihydropyridine CCB | 5-10 mg PO | 2-5 h / 24 h | Alternative to amlodipine |
| Clonidine | Central alpha-2 agonist | 0.1-0.2 mg PO q1h (max 0.6 mg) | 30-60 min / 6-8 h | Effective but AVOID — sedation, rebound hypertension on withdrawal, bradycardia; largely abandoned |
| Prazosin / doxazosin | Alpha-1 blocker | 1-2 mg / 2-4 mg PO | 1-2 h / 12-24 h | Useful in heart failure or BPH; first-dose hypotension |
| Furosemide | Loop diuretic | 20-40 mg PO | 1-2 h / 6-8 h | Only if volume-overloaded; avoid in volume-depleted patient |
| Sublingual nifedipine | DHP CCB | — | — | NEVER — unpredictable, precipitous fall → stroke/MI; withdrawn from guidelines worldwide |
The principles of urgency management: (1) confirm the absence of target-organ damage by history, examination, ECG, urine dipstick, and creatinine — if any is present, reclassify as an emergency; (2) identify and address the precipitant — the commonest is medication non-adherence, followed by cocaine/amphetamines, NSAIDs, steroids, erythropoietin, oral contraceptives, and clonidine withdrawal; (3) start or reinstate oral therapy and arrange follow-up within 24-72 hours; (4) never use sublingual nifedipine; (5) do not admit to ICU unless there is an emergency.[1]
Stepwise ICU management
Stepwise ICU management of a hypertensive emergency
- RECOGNISE AND TRIAGE (the first 5-10 minutes). (a) Establish that this is a true EMERGENCY (severe BP + acute target-organ damage) and not urgency — the answer dictates IV vs oral therapy. (b) Identify the SPECIFIC emergency, because drug selection and the BP target are scenario-driven. Actively seek: hypertensive encephalopathy, intracerebral haemorrhage, ischaemic stroke, ACS, acute pulmonary oedema, aortic dissection, severe AKI/microangiopathy, and (in pregnancy) pre-eclampsia/eclampsia. (c) Place the patient in ICU/HDU with continuous cardiac monitoring and large-bore IV access.[1]
- ESTABLISH ACCURATE BLOOD-PRESSURE MEASUREMENT. (a) Insert an ARTERIAL LINE — cuff pressures are unreliable at extremes and during rapid titration. (b) Confirm the reading in both arms (a >20 mmHg systolic differential suggests aortic dissection or subclavian stenosis). (c) Treat the patient, not the number: many patients are volume-depleted from pressure natriuresis and have a true MAP lower than it appears.[1]
- RAPID FOCUSED ASSESSMENT. (a) Neurological: GCS, pupils, focal deficits, fundoscopy (papilloedema, flame haemorrhages). (b) Cardiovascular: heart sounds, new aortic regurgitant murmur (dissection), pulse and BP in all four limbs, JVP, lung fields, abdominal bruit. (c) Investigations: 12-lead ECG (ischaemia, LVH with strain), CXR (mediastinal widening, pulmonary oedema), urine dipstick (proteinuria/haematuria — malignant HTN), FBC (schistocytes — microangiopathic haemolysis), U&E/creatinine, troponin, lactate, and a pregnancy test in any woman of reproductive age. (d) Cross-sectional imaging dictated by the syndrome: CT brain for any neurological emergency, CT angiography of the chest for suspected dissection.[1]
- START A TITRATABLE IV AGENT — CHOSEN BY THE SPECIFIC EMERGENCY. (a) Default versatile agents: labetalol or nicardipine. (b) Both given by infusion, titrated every 5-15 minutes against an arterial-line BP and a defined target. (c) AVOID oral/sublingual agents, and AVOID sodium nitroprusside except in exceptional circumstances. (d) Drug-specific guidance in the tables above.[7]
- REDUCE BP GRADUALLY TO THE SCENARIO-SPECIFIC TARGET. (a) For most emergencies, reduce MAP by 10-20 per cent in the first hour, then gradually to ~160/100 over 2-6 h. (b) Do NOT normalise. (c) EXCEPTIONS — aortic dissection (rapid to SBP 100-120, beta-blocker first), ICH (SBP to 140 within 1 h per INTERACT2), pre-eclampsia (SBP <160 / DBP <110, magnesium first). (d) Continuously reassess: a falling GCS during BP reduction means you have crossed below the autoregulatory floor — allow the pressure to rise.[4][5]
- IDENTIFY AND TREAT THE PRECIPITANT AND THE CAUSE. (a) Common precipitants: medication non-adherence (the commonest), cocaine/amphetamines, NSAIDs/steroids/erythropoietin, clonidine withdrawal, renovascular disease, CKD. (b) Screen for SECONDARY hypertension in every patient — plasma metanephrines (phaeochromocytoma), aldosterone:renin ratio (primary hyperaldosteronism), renal artery Doppler/CTA (renovascular), urinary drug screen. (c) Plan transition from IV to oral therapy once stable and the target maintained for 6-12 h.
- MONITOR AND PREVENT COMPLICATIONS. (a) Continuous arterial-line BP, hourly GCS and urine output, serial creatinine/electrolytes, cardiac monitoring. (b) Watch for over-shoot hypotension (the commonest iatrogenic harm). (c) Watch for rebound hypertension if an infusion is stopped abruptly. (d) Address volume status — many patients benefit from a cautious crystalloid bolus; vasodilating an empty patient causes collapse.
Exam practice
SAQ — Malignant hypertension with posterior reversible encephalopathy syndrome
10 minutes · 10 marks
A 52-year-old man with a 10-year history of untreated hypertension presents to the emergency department with a 24-hour history of severe throbbing headache, nausea, blurred vision and progressive confusion, culminating in two generalised tonic-clonic seizures in the ambulance. On arrival he is post-ictal, GCS 13 (E3V4M6), BP 224/138 confirmed by arterial line, HR 108 sinus, SpO2 96 per cent on room air. Fundoscopy shows bilateral papilloedema with flame-shaped retinal haemorrhages and cotton-wool spots. He has no focal limb deficit. Bloods: creatinine 186 micromol/L (baseline 95), potassium 3.4, Hb 112, platelets 90, blood film shows schistocytes, lactate dehydrogenase 720 IU/L, troponin 24 ng/L. Urine dipstick: protein 2+, blood 3+. Non-contrast CT brain is unremarkable; MRI brain demonstrates symmetric T2/FLAIR hyperintensity in the parieto-occipital white matter, consistent with posterior reversible encephalopathy syndrome (PRES).
SAQ — Acute type A aortic dissection with severe hypertension
10 minutes · 10 marks
A 64-year-old man with poorly controlled hypertension (baseline 165/95, on no medication for 6 months) presents with sudden, instantaneous, tearing central chest pain radiating through to the interscapular region, described as the worst pain he has ever experienced. On arrival he is diaphoretic and distressed. BP 192/112 in the right arm and 156/96 in the left arm, HR 118 sinus, SpO2 96 per cent on room air, GCS 15. Cardiovascular examination reveals a soft early diastolic murmur at the left sternal edge consistent with new aortic regurgitation, equal femoral pulses, and no pulse deficit. ECG shows sinus tachycardia with non-specific T-wave flattening; troponin 18 ng/L. Chest X-ray shows a widened mediastinum of 9.6 cm and a small left pleural effusion. CT aortogram confirms a Stanford type A aortic dissection with an intimal flap in the ascending aorta extending into the arch, a moderate haemopericardium without tamponade physiology, and the right renal artery arising from the true lumen. The cardiothoracic surgeon is 90 minutes away.
Clinical pearls — high-yield points for the exam
Errors to avoid — the classic pitfalls
Evidence — the landmark trials
Hypertensive emergency — the landmark trials, registries, and guidelines
2017 ACC/AHA Hypertension Guideline (Whelton, JACC 2018): redefined hypertension (SBP ≥130 or DBP ≥80), reframed staging, and codified the emergency/urgency distinction and the staged, scenario-driven BP-reduction targets.[1] ESC Council on Hypertension position document (van den Born, EHJ-CVP 2019): the contemporary European consensus on hypertensive emergencies — definitions, specific syndromes, agent pharmacology, and scenario-driven drug selection.[2] Cochrane review (Perez, Musini, Wright, 2008): the rigorous systematic review demonstrating the thin evidence base for IV antihypertensive choice; no agent proven superior for mortality/morbidity.[3] Immink (Circulation 2004): the seminal demonstration that cerebral autoregulation is impaired/shifted in malignant hypertension — the physiological basis for gradual, sub-normalisation BP reduction.[4] INTERACT2 (Anderson, NEJM 2013): 2,839 ICH patients; intensive SBP lowering to <140 within 1 h produced a significant ordinal shift to better functional outcome, no excess harm — target SBP 130-150.[5] ATACH2 (Qureshi, NEJM 2016): lowering to 110-139 vs 140-179 added no benefit and more renal harm — set the ICH floor at ~130.[6] STAT registry (Katz/Gore/Amin, Am Heart J 2009): >2,500 patients with acute severe hypertension; documented real-world over-rapid reduction and habit-driven agent choice — the case for scenario-driven therapy.[7] Magpie trial (Altman/Duley, Lancet 2002): >10,000 women; established magnesium sulphate as the standard for seizure prophylaxis and treatment in pre-eclampsia/eclampsia.[8]
Hypertensive emergency — outcomes and key numbers
Prognosis
With prompt, scenario-driven ICU management the in-hospital mortality of hypertensive emergency is roughly 5-10 per cent, driven by the underlying syndrome (highest in aortic dissection, massive ICH, and pulmonary oedema) rather than the pressure itself. Long-term cardiovascular morbidity is high, and recurrence is common if the precipitant is not addressed and the chronic regimen not re-established. The strongest modifiable protections are accurate triage (emergency vs urgency), a controlled scenario-specific BP target, an appropriately chosen titratable IV agent, identification and treatment of the cause, and a structured transition to effective oral therapy with close follow-up. The STAT registry's lessons — that real-world practice too often delivers over-rapid reduction and habit-driven agent choice — remain the clearest argument for disciplined, protocol-driven care.[1][1][7]
References
- [1]Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines J Am Coll Cardiol, 2018.PMID 29146535
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