Tintinalli's Emergency Medicine - Just the Facts, 3ed.

28. SYSTEMIC AND PULMONARY Zo HYPERTENSION

David M. Cline

images Classification of acute systemic hypertension into categories facilitates management.

images Hypertensive emergency: elevated blood pressure (BP) associated with target organ dysfunction such as aortic dissection, acute pulmonary edema, acute coronary syndrome, acute renal failure, severe preeclampsia, hypertensive encephalopathy, subarachnoid hemorrhage, intracranial hemorrhage, acute ischemic stroke, and sympathetic crisis.

images Immediate recognition and treatment are required for the conditions above but therapeutic goals (percentage reduction or target pressures) for hypertensive emergencies vary considerably.

images Hypertensive urgency: a clinical presentation associated with severe elevations in blood pressure without progressive target organ dysfunction. The arbitrary numerical criterion of ≥ 180/110 mm Hg is often cited as an indication for treatment, when in fact the clinical benefit of such treatment not well defined (see Emergency Department Care section).

images The clinician must ensure that the BP cuff size is appropriate for the patient’s size; a small cuff relative to the arm size produces a falsely elevated reading.

PATHOPHYSIOLOGY

images Although poorly understood, one mechanism of severe hypertension is a sudden increase in systemic vascular resistance secondary to circulating humoral vasoconstrictors.

images There appears to be a critical arterial pressure that overwhelms the target organ’s ability to compensate for the increased arterial pressure, which limits blood flow.

images These initial events trigger mechanical wall stress and endothelial injury, leading to increased permeability, activation of the coagulation cascade and platelets, and deposition of fibrin. Ultimately fibrinoid necrosis of the arterioles ensues, which potentially can be recognized clinically by hematuria (when the kidney is involved) or arterial hemorrhages or exudates on findus examination (when the eye is involved).

images The renin-angiotensin system is activated, which leads to further vasoconstriction. Volume depletion may occur through pressure natriuresis, prompting further release of vasoconstrictors from the kidney.

images These combined effects produce hypoperfusion of the end-organs with ischemia and dysfunction.

CLINICAL FEATURES

images Essential historic features include a prior history of HTN; noncompliance with BP medications; cardiovascular, renal, or cerebrovascular disease; diabetes; hyperlipidemia; chronic obstructive pulmonary disease or asthma; and a family history of HTN.

images Precipitating causes such as pregnancy, illicit drug use (cocaine and methamphetamines), or decongest-ants should be considered.

images Patients should be asked about central nervous system symptoms (headaches, visual changes, weakness, seizures, and confusion), cardiovascular symptoms (chest pain, palpitations, dyspnea, syncope, pedal edema, or tearing pain radiating to the back or abdomen), and renal symptoms (anuria, edema, or hematuria).

images The patient should be examined for evidence of papilledema, retinal exudates, neurologic deficits, seizures, or encephalopathy; the presence of these findings may constitute a hypertensive emergency in the setting of elevated blood pressure.

images The patient also should be assessed for carotid bruits, heart murmurs, gallops, asymmetrical pulses or unequal blood pressures (coarctation vs aortic dissection), pulsatile abdominal masses, and pulmonary rales.

images Hypertensive encephalopathy is characterized by altered mental status in the setting of acute hypertension, and may be accompanied by headache, vomiting, seizures, visual disturbances, papilledema, or hematuria.

images In the pregnant (or postpartum) patient, the clinician should look for hyperrefiexia and peripheral edema, suggesting preeclampsia.

DIAGNOSIS AND DIFFERENTIAL

images Testing should be guiding by presenting symptoms, the most cost effective test is urinalysis.

images Renal impairment may present as hematuria, pro-teinuria, red cell casts, or elevations in blood urea nitrogen, creatinine, and potassium levels.

images An electrocardiogram may show ST- and T-wave changes consistent with coronary ischemia (see Chapter 20), electrolyte abnormalities, or left ventricular hypertrophy.

images A chest x-ray may help identify congestive heart failure (see Chapter 24), or aortic dissection (see Chapter 29).

images In patients with neurologic compromise, computed tomography of the head may show ischemic changes, edema, or blood (see Chapter 143).

images A urine or serum drug screen may identify illicit drug use. A pregnancy test should be done on all hypertensive women of childbearing potential.

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images Patients with hypertensive emergencies require O2 supplementation, cardiac monitoring, and intravenous access. After attention to the ABCs of resuscitation, the treatment goal is to reduce arterial pressure gradually in the following clinical situations, with attention to the therapeutic goal.

AORTIC DISSECTION

images For aortic dissection reduce force of contraction and sheer forces first with β-blockers, reduce heart rate to approximately 60 beats per minute, reduce BP below 140 mm Hg systolic, and ideally, below 120 systolic (100–120 mm Hg) if tolerated by the patient.

images Recommended first agents include esmolol (300 micrograms/kg IV bolus followed by a 50 micrograms/kg per min infusion) or labetalol (20 milligrams IV over 2 min followed by subsequent doses of 20–40 milligrams IV g over 10 min as needed up to 300 milligrams maximum).

images If β-blockers are contraindicated, use verapamil 5 to 10 milligrams IV, or diltiazem 0.25 milligrams/kg IV over 2 minutes, to reduce heart rate. Follow β-blockers with vasodilators as needed to achieve desired blood pressure reduction.

images Nicardipine can be started by IV infusion: start at a rate of 5 milligrams/h. If target BP is not achieved in 5 to 15 minutes, increase dose by 2.5 milligrams/h every 5 to 15 minutes until target pressure or the maximum dose of 15 milligrams/h is reached.

images Alternatively, use nitroprusside IV infusion: 0.3 to 0.5 micrograms/kg/min initial infusion, increase by increments of 0.5 micrograms/kg/min; titrate to desired effect.

ACUTE HYPERTENSIVE PULMONARY EDEMA

images For acute hypertensive pulmonary edema, reduce BP by no more than 20% to 30%.

images First agent of choice is nitroglycerin, sublingual 0.4 milligrams, up to three doses, paste 1 to 2 inches, or IV infusion, start 5 micrograms/min, increase by 5 micrograms/min every 3 to 5 minutes to 20 micrograms/min; if no response at 20 micrograms/min, increase by 10 micrograms/min every 3 to 5 minutes, up to 200 micrograms/min.

images Alternatives include enalaprilat IV, 0.625 to 1.25 milligrams over 5 minutes every 4 to 6 hours, titrate at 30 minutes intervals to a maximum of 5 milligrams every 6 hours, nicardipine (see dose above) or nitroprusside (see dose above).

ACUTE CORONARY SYNDROME

images For acute coronary syndrome, if BP is above 160 mm Hg systolic, reduce BP no more than 20% acutely.

images Start with nitroglycerin (see dose above) or meto-prolol 50 to 100 milligrams PO every 12 hours, or 5 milligrams IV every 5 to 15 minutes up to 15 milligrams. Avoid IV β-blockers if patient is at risk for cardiogenic shock.

ACUTE SYMPATHETIC CRISIS

images In acute sympathetic crisis, treat to relieve symptoms, start with benzodiazepines first.

images Follow with nitroglycerin (see dose above), or phen-tolamine, bolus load: 5 to 15 milligrams IV

ACUTE RENAL FAILURE

images For BP above 180/110 mm Hg, reduce BP by no more than 20% acutely.

images Recommend agents include labetalol (see dose above), nicardipine (see dose above) or fenoldopam, start 0.1 microgram/kg/min, titrate to desired effect every 15 minutes, range 0.1 to 1.6 micrograms/kg/min.

PREECLAMPSIA

For preeclampsia with BP above 160/110 mm Hg, use labetalol (see dose above). Hydralazine, 5 to 10 milligrams IV, is less predictable, but commonly used.

HYPERTENSIVE ENCEPHALOPATHY

images For BP above 180/110 (in the setting of immuno-suppressive drugs, symptomatic BP may be lower), reduce BP by no more than 20% acutely.

images Recommended agents include nicardipine (see dose above), labetalol (see dose above), fenoldopam (see dose above), or nitroprusside (see dose above).

SUBARACHNOID HEMORRHAGE

images Reduce systolic pressure below 160 mm Hg or MAP below 130 mm Hg to prevent rebleeding.

images Recommended agents include nicardipine (see dose above), labetalol (see dose above), or esmolol (see dose above).

INTRACRANIAL HEMORRHAGE

images To reduce hemorrhage growth, for patients with evidence of increased intracranial pressure (decreased level of consciousness, evidence of midline shift, or hematoma volume >30 mL on CT imaging), reduce MAP to 130mmHg.

images In patients for whom there is no suspicion of increased intracranial pressure, treatment may be intensified to a MAP of 110 mm Hg, or a systolic pressure of 150 to 160mmHg.

images Recommended agents include nicardipine (see dose above), labetalol (see dose above), or esmolol (see dose above).

ACUTE ISCHEMIC STROKE

images If fibrinolytic therapy is planned, reduce BP below 185/110 mm Hg; if no fibrinolytic therapy is planned and BP remains elevated on repeat measures, reduce BP below 220/120 mm Hg. More intensive lowering can be accomplished safely (however, pharmacologic reduction below 160/100 is not advised).

images Recommended agents include labetalol (see dose above), nicardipine (see dose above), or nitroglycerin paste, 1 to 2 inches.

HYPERTENSIVE URGENCY

images For hypertensive urgency, useful agents include oral labetalol 200 to 400 milligrams, repeated every 2 to 3 hours; oral captopril 25 milligrams every 4 to 6 hours; sublingual nitroglycerin spray or tablets (0.3–3.0 milligrams); or clonidine, 0.2 milligrams oral loading dose, followed by 0.1 milligrams/h until the DBP is below 115 mm Hg, or a maximum of 0.7 milligrams.

images For asymptomatic patients with severe hypertension, with BP above the 180/200 systolic range, or above 110/120 diastolic range, starting an oral agent at discharge should be considered.

images The choice of the oral agent should be based on coexisting conditions, if any. Diuretics, such as hydrochlo-rothiazide 25 milligrams/d, should be used in most patients with uncomplicated HTN.

images For patients with angina, postmyocardial infarction, migraines, or supraventricular arrhythmias, a β-blocker should be considered, such as metoprolol 50 milligrams orally 2 times daily.

images Angiotensin-converting enzyme inhibitors such as lisinopril, start at 10 milligrams daily, can be used in those with heart failure, renal disease, recurrent strokes, or diabetes mellitus.

images Restarting a noncompliant patient on a previously established regimen is a recommended strategy.

CHILDHOOD HYPERTENSIVE EMERGENCIES

images Children often will have nonspecific complaints such as throbbing frontal headache or blurred vision.

images Physical findings associated with HTN are similar to those found in adults.

images The most common etiologies in pre-teenage children are renovascular lesions and pheochromocytoma.

images The decision to treat a hypertensive emergency in a child is based on the BP and associated symptoms. Urgent treatment is required if the BP exceeds prior measurements by 30%.

images Alternatively, if prior measurements are not known, childhood hypertension is defined as diastolic or systolic blood pressure > the 95th percentile on a standardized table.

images The goal is to reduce the BP by 25% within an hour in acutely symptomatic patients.

images Preferred medications for the control of hypertensive emergencies in children include labetalol, 0.2 to 1.0 milligram/kg per dose, up to 40 milligrams/dose, or an infusion of 0.25 to 3.0 milligrams/kg/h; nicardipine, 1 to 3 micrograms/kg/min; or, if prior drugs fail, nitroprusside, 0.5 to 10.0 micrograms/kg/min.

images The treatment of pheochromocytoma is surgical excision and managing the BP with α-adrenergic blockers such as phentolamine. Pediatric HTN that requires intervention in the emergency department will likely require admission.

PULMONARY HYPERTENSION

images Although the diagnosis of pulmonary hypertension cannot be made in the ED, suspicion of primary or secondary pulmonary hypertension as a cause of dyspnea, chest pain, or syncope can affect ED evaluation, consultation, or disposition.

images Pulmonary hypertension is a pathologic condition characterized by elevation of the pulmonary vascular pressure, which compromises right ventricular function.

images There can be an isolated increase in pulmonary arterial pressure or an elevation of both arterial and venous pressure.

images The hemodynamic parameter that defines pulmonary hypertension is a median pulmonary artery pressure of >25 mm Hg at rest or >30 mm Hg during effort.

images The most common symptoms are dyspnea, fatigue, syncope, and chest pain.

images Typically, this disorder will be seen in association with other cardiovascular or pulmonary disorders such as chronic obstructive pulmonary disease, left ventricular dysfunction, or disorders associated with hypoxemia.

images Treatment of the underlying disorder is the only management indicated in the emergency setting, for example, oxygen for conditions producing hypoxia.

images Patients may be on calcium channel blockers chronically, or for primary pulmonary hypertension, patients may have arrangements for home infusions of epo-prostenol (prostacyclin).


For further reading in Emergency Medicine: A Comprehensive Study Guide, 7th edition., see Chapter 61, “Systemic and Pulmonary Hypertension,” by David M. Cline, and Alberto J. Machado.