Hypertensive Crisis & Special Populations Study Guide

Comprehensive vocabulary flashcards covering the pathophysiology, clinical targets, pharmacology, resistant hypertension management, and special population considerations in hypertensive crisis.

Hypertensive Crisis

An acute, severe elevation in blood pressure defined as a systolic blood pressure $\text{SBP} \ge 180\,\text{mmHg}$ and/or diastolic blood pressure $\text{DBP} \ge 120\,\text{mmHg}$.

Severe Hypertension

An acute, severe blood pressure elevation ($\text{BP} > 180/120\,\text{mmHg}$) presenting without evidence of acute target organ damage, formerly termed hypertensive urgency.

Hypertensive Emergency

An acute, severe blood pressure elevation ($\text{BP} > 180/120\,\text{mmHg}$) presenting with evidence of acute, progressive target organ damage affecting the brain, heart, kidneys, or vascular system.

Vascular Shear Stress

Physical mechanical stress exerted by extremely high intravascular pressure against arterial walls that strips endothelial cells, triggering increased vascular permeability, platelet and fibrin deposition, and fibrinoid necrosis.

Spontaneous Natriuresis

Renal sodium and water excretion triggered by marked elevations in systemic vascular resistance, culminating in intravascular volume depletion.

Normal Cerebral Autoregulation

The physiological mechanism in healthy individuals that maintains cerebral blood flow at approximately $700\text{--}750\,\text{mL/min}$ within a mean arterial pressure range of $60\text{ to }120\,\text{mmHg}$.

Right-Shift of Cerebral Autoregulation

Arteriolar remodeling occurring in chronic, uncontrolled hypertension that shifts the cerebral autoregulation curve to higher pressure ranges to protect brain tissue from excessive hydrostatic pressure.

Iatrogenic Stroke Mechanism

Cerebral ischemia resulting from lowering blood pressure too rapidly into a conventional "normal" range in a patient with chronic hypertension, which drops cerebral blood flow below $\le 300\,\text{mL/min}$.

Cerebral Vascular Collapse Threshold

The critical hemodynamic threshold where cerebral blood vessels collapse completely, occurring when mean arterial pressure falls below $30\,\text{mmHg}$.

Fibrinoid Necrosis

Structural arterial damage caused by endothelial disruption and plasma protein leakage, leading to luminal narrowing, microvascular occlusion, and tissue ischemia.

Maladaptive Neurohormonal Surge

A compensatory release of renin-angiotensin-aldosterone system hormones and catecholamines accompanied by a reduction in nitric oxide and prostacyclin in response to intravascular volume depletion, perpetuating a vicious cycle of blood pressure elevation.

Hypertensive Encephalopathy

An acute central nervous system manifestation of target organ damage characterized by altered mental status and papilledema.

Target Organ Damage: Cardiovascular Manifestations

Acute cardiovascular injuries precipitated by hypertensive crisis, including acute coronary syndrome (myocardial infarction, unstable angina), acute pulmonary edema with bilateral crackles, and acute aortic dissection.

Target Organ Damage: Renal Manifestations

Acute kidney injury or acute renal failure evidenced by acute elevations in serum creatinine, blood urea nitrogen, and serum potassium.

Hypertensive Emergency General BP Goal

In patients without a compelling condition, reduce systolic blood pressure by no more than $25\%$ within the first hour, achieve $\text{SBP} < 160/100\,\text{mmHg}$ within $2\text{--}6\,\text{hours}$, and reach $130\text{--}140\,\text{mmHg}$ over $24\text{--}48\,\text{hours}$.

Acute Aortic Dissection BP Target

Rapid reduction of systolic blood pressure to $< 120\,\text{mmHg}$ within $20\,\text{minutes}$, with maintenance of systolic blood pressure between $100\text{--}120\,\text{mmHg}$.

Acute Aortic Dissection Treatment Sequence

The mandatory administration of a parenteral beta-blocker (e.g., esmolol or labetalol) prior to initiating a vasodilator (e.g., nicardipine or nitroprusside) to prevent reflex tachycardia and shear stress.

Acute Intracranial Hemorrhage BP Target

Rapid reduction of systolic blood pressure to $140\,\text{mmHg}$ within the first hour while maintaining stable intracranial pressure and mean arterial pressure.

Permissive Hypertension

The strategy in acute ischemic stroke of allowing elevated blood pressure to maintain cerebral perfusion, intervening to lower blood pressure by $15\%$ only if $\text{BP} \ge 220/120\,\text{mmHg}$, or keeping $\text{SBP} < 180/105\,\text{mmHg}$ for $24\,\text{hours}$ if tPA is administered.

Acute Coronary Syndrome BP Target

Immediate reduction of systolic blood pressure to $< 140\,\text{mmHg}$ with an ultimate goal of normotension.

Acute Pulmonary Edema BP Management

Immediate reduction of blood pressure targeting normotension using intravenous vasodilators (nitroglycerin, clevidipine, or nitroprusside), while strictly avoiding beta-blockers.

Eclampsia / Preeclampsia BP Target

Reduction of blood pressure to $< 160/110\,\text{mmHg}$ within $30\text{--}60\,\text{minutes}$, maintained below $160/110\,\text{mmHg}$ until delivery.

Catecholamine Excess BP Management

Rapid reduction of blood pressure and symptom control using phentolamine as first-line therapy, clevidipine, or nicardipine; unopposed beta-blockers are contraindicated.

Severe Hypertension (Urgency) Strategy

Adjustment or reinstitution of oral outpatient antihypertensive regimens over $24\text{--}48\,\text{hours}$ while withholding acute intravenous or oral loading doses to prevent post-discharge hypotension and stroke.

Nicardipine

An intravenous dihydropyridine calcium channel blocker with an onset of $5\text{--}15\,\text{minutes}$ and duration of $30\text{--}40\,\text{minutes}$, contraindicated in advanced aortic stenosis.

Clevidipine

A lipid-emulsion dihydropyridine calcium channel blocker with an onset of $2\text{--}4\,\text{minutes}$ and duration of $5\text{--}15\,\text{minutes}$, contraindicated in soy allergy, egg allergy, hyperlipidemia, and pancreatitis.

Sodium Nitroprusside

A parenteral nitric oxide vasodilator with immediate onset and $1\text{--}2\,\text{minute}$ duration that increases intracranial pressure and carries a risk of cyanide and thiocyanate toxicities.

Cyanide and Thiocyanate Toxicity Risk Factors

Complications associated with sodium nitroprusside infusions occurring in patients with chronic kidney disease, infusion rates $> 3\,\text{mcg/kg/min}$, or administration durations $> 3\,\text{days}$.

Nitroglycerin (IV)

A parenteral nitrate vasodilator with an onset of $2\text{--}5\,\text{minutes}$ and duration of $3\text{--}5\,\text{minutes}$, contraindicated with PDE-5 inhibitors or volume depletion, and prone to tachyphylaxis.

Labetalol (IV)

A combined $\alpha_1$ and non-selective $\beta_{1,2}$ blocker with an onset of $2\text{--}5\,\text{minutes}$ and duration of $2\text{--}4\,\text{hours}$, contraindicated in severe asthma, COPD, second- or third-degree heart block, and decompensated heart failure.

Esmolol

A cardioselective $\beta_1$ blocker with an onset of $1\text{--}2\,\text{minutes}$ and duration of $10\text{--}20\,\text{minutes}$, preferred in aortic dissection, acute coronary syndrome, and perioperative hypertension.

Phentolamine

A parenteral non-selective alpha-adrenergic antagonist with an onset of $1\text{--}2\,\text{minutes}$ and duration of $10\text{--}30\,\text{minutes}$, indicated as first-line therapy for catecholamine crises (cocaine toxicity, pheochromocytoma, clonidine withdrawal).

Fenoldopam

A dopamine DA-1 agonist with an onset of $5\text{--}10\,\text{minutes}$ and duration of $30\text{--}60\,\text{minutes}$, indicated for acute kidney injury but contraindicated in glaucoma, elevated intraocular pressure, and sulfite allergy.

Hydralazine (IV)

A direct parenteral vasodilator with an onset of $10\text{--}30\,\text{minutes}$ and duration of $2\text{--}4\,\text{hours}$ that produces an unpredictable blood pressure reduction, making it undesirable as a general first-line emergency agent.

Resistant Hypertension

Blood pressure remaining uncontrolled ($\ge 130/80\,\text{mmHg}$) despite concurrent adherence to $\ge 3$ full-dose antihypertensive agents of different classes (including a diuretic), or controlled blood pressure requiring $\ge 4$ medications.

Pseudoresistance

Apparent treatment resistance attributable to inaccurate cuff size, white-coat effect, or medication non-adherence.

SYMPATHY Trial

A clinical trial documenting a $50\text{--}80\%$ prevalence of medication non-adherence among patients evaluated for apparent resistant hypertension.

NSAID-Induced Hypertension

The leading drug-induced cause of resistant hypertension, mediated by renal cyclooxygenase inhibition that reduces prostaglandins, induces sodium and water retention, and blunts antihypertensive efficacy.

Chlorthalidone Optimization

The substitution of hydrochlorothiazide with chlorthalidone ($12.5\text{--}25\,\text{mg}$ daily) to achieve superior 24-hour and overnight blood pressure control, which requires close monitoring of serum potassium.

Spironolactone (in Resistant HTN)

A mineralocorticoid receptor antagonist added at $25\text{--}50\,\text{mg}$ daily as the preferred fourth-line agent for resistant hypertension, requiring serum creatinine and potassium monitoring within $3\text{ to }7\,\text{days}$.

Chronotherapy

The clinical practice of shifting $1$ or $2$ antihypertensive medications to bedtime to improve nocturnal blood pressure dipping and decrease cardiovascular events.

MEPAC Trial

The clinical trial demonstrating that bedtime dosing of antihypertensive medications improves nocturnal blood pressure dipping and reduces cardiovascular events.

"He Loves My Neonate"

A clinical mnemonic identifying the first-line antihypertensive medications considered acceptable during pregnancy: Hydralazine, Labetalol, Methyldopa, and Nifedipine.

Gestational Blood Pressure Nadir

The expected physiological low point in maternal blood pressure occurring between $16\text{--}18\,\text{weeks}$ of gestation.

Fetotoxic Antihypertensive Classes

Antihypertensive agents contraindicated in pregnancy: ACE inhibitors, ARBs, direct renin inhibitors, mineralocorticoid receptor antagonists (spironolactone/eplerenone), atenolol, and nitroprusside.

Atenolol in Lactation

A beta-blocker to avoid during breastfeeding due to extensive milk excretion that causes infant bradycardia and lethargy.

Candesartan (in Migraine Prophylaxis)

An angiotensin receptor blocker demonstrating superior efficacy for comorbid hypertension and migraine prophylaxis, characterized by a number needed to treat (NNT) of $3\text{--}4$.

Unopposed Alpha-Stimulation

Severe paradoxical vasoconstriction and blood pressure elevation caused by administering a pure beta-blocker (such as propranolol) in the setting of cocaine toxicity or pheochromocytoma, leaving alpha-1 receptors unchecked.

Beta-Blocker Withdrawal Syndrome

Rebound tachycardia, elevated myocardial oxygen demand, angina, or infarction resulting from abrupt cessation of chronic beta-blocker therapy due to beta-receptor upregulation.

Beta-Blocker Tapering Protocol

The protocol used to prevent withdrawal rebound by reducing the beta-blocker dose by $50\%$ every $3\text{--}7\,\text{days}$ while restricting physical exertion.

Clonidine Withdrawal Rebound

Severe rebound hypertension ($\text{BP} > 190/110\,\text{mmHg}$) caused by the sudden cessation of central alpha-2 agonists, which removes negative feedback and triggers excessive norepinephrine release onto upregulated alpha-1 receptors.

Reflex Tachycardia (from Vasodilators)

A compensatory sympathetic reflex response to rapid arterial vasodilation (from short-acting/crushed nifedipine, hydralazine, or minoxidil) that increases heart rate, myocardial oxygen demand, and ischemic risk.

Fatal Triple AV Block ("Triple Whammy")

Complete heart block, profound bradycardia, and cardiogenic shock produced by the combined, synergistic AV-nodal suppression of digoxin, a beta-blocker, and a non-dihydropyridine calcium channel blocker (verapamil or diltiazem).

Preload-Mediated Iatrogenic Heart Failure

Volume overload and heart failure exacerbation caused by renal sodium and water retention from medications such as NSAIDs, COX-2 inhibitors, corticosteroids, thiazolidinediones, and high-sodium OTC products.

Negative Inotropic Iatrogenic Heart Failure

Direct suppression of myocardial contractility precipitating heart failure decompensation, caused by non-DHP CCBs (verapamil, diltiazem), nifedipine, non-approved beta-blockers (propranolol), or antiarrhythmics (disopyramide, flecainide).