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CHAPTER 12
HYPERTENSIVE EMERGENCIES DEFINITIONS Hypertensive Emergencies A severe elevation of blood pressure is considered an emergency if there is evidence of rapid or progressive central nervous system, myocardial, hematologic or renal deterioration. Patient requires an immediate reduction in blood pressure generally by intravenous therapy. Hypertensive Urgency - Severe elevation of blood pressure without evidence of progressive end organ damage. - Require a gradual reduction in blood pressure over a period of 24-48 hours usually with an oral agent. Most cases of severe blood pressure elevation do not constitute a hypertensive crisis, e.g., · Chronic asymptomatic severe hypertension with grade 0, I or II fundi. · Acute blood pressure elevation associated with anxiety. · Pseudohypertension. · Systolic hypertension in elderly. Mode of Presentation of Hypertensive Crisis 1. Chronic hypertension, e.g., accelerated or malignant hypertension. 2. Hypertensive Emergencies Acute blood pressure rise in previously normotensive patient, e.g. acute glomerulonephritis, preeclampsia. 3. Blood pressure elevation that precipitates or aggrevates an underlying medical condition, e.g. acute myocardial infarction or acute aortic dissection. HYPERTENSIVE EMERGENCIES 1. Hypertensive encephalopathy. 2. Hypertension with intracranial hemorrhage. 3. Hypertension with stroke. 4. Hypertension with pulmonary edema. 5. Hypertension with acute myocardial infarction. 6. Adrenergic crisis. 7. Dissecting aortic aneurysm. 8. Eclampsia. HYPERTENSIVE URGENCIES 1. Malignant hypertension. 2. Hypertension with left ventricular failure. 3. Hypertension with unstable angina. 4. Perioperative hypertension. 5. Pre-eclampsia. Causes of Hypertensive Crisis 1. Renovascular and renal parenchymal disease. 2. Drugs: Cocaine, amphetamines, diet pills, tricyclic antidepressants, monoamine oxidase inhibitor + tyramine, oral contraceptives. 3. Withdrawal from antihypertensives, e.g., clonidine 4. Pre-eclampsia and eclampsia. 5. Head injury. 6. Pheochromocytoma.
HYPERTENSIVE ENCEPHALOPATHY · Neurologic manifestations with severe hypertension (usually DBP > 140 mmHg). · Clinical Findings: - Headache. - Altered mental status: confusion, coma. - Visual impairment. - Convulsions, nausea, vomiting. - Focal neurologic deficit: weakness, asymmetric reflexes. - Syndrome resolves within few hours of blood pressure reduction. · Pathologic Findings: - Micro infarctions. - Hemorrhages. - Cerebral edema. · In patients without previous history of hypertension, encephalopathy can develop at diastolic blood pressure less than 140 mmHg. Plan of Management of Hypertensive Emergency 1. Make sure of blood pressure level: Measure blood pressure accurately 3 or 4 times using the appropriate cuff size. 2. Exclude pseudohypertension (chapter 3) in the elderly or in the obese. 3. Exclude severe anxiety state with hypertension. Hypertensive Emergencies 4. Optic fundus examination is essential. 5. Identify conditions that require special management: · Aortic dissection. · Acute myocardial infarction. · Withdrawal from antihypertensive drugs. · Monoamine oxidase inhibitor reactions. · Eclampsia. · Scleroderma and other collagen vascular diseases. · Pheochromocytoma. 6. Differentiate hypertensive encephalopathy from other causes of encephalopathy with hypertension, e.g., stroke, subarachenoid hemorrhage, brain tumour, vasculitis, encephalitis. 7. Differentiate between hypertensive emergency and urgency. 8. Hospitalization and parenteral therapy is required in emergencies. 9. Diagnose underlying medical conditions. 10. Define the required target blood pressure. 11. In patients with stroke, intracerebral hemorrhage, subarachenoid hemorrhage or cerebral infarction, use antihypertensive therapy only if blood pressure is above 200/130 mmHg. Reduce blood pressure gradually by 20 to 25% during the first 24 hours. 12. After reduction of blood pressure give oral antihypertensive agents with relatively rapid onset of action, e.g., calcium antagonists, sympatholytics (clonidine, methyldopa) or prazosin. 13. Blood volume expansion can limit the hypotensive efficacy of many agents. Frusemide (Lasix) in large and frequent (2-3 times) daily administrations is usually needed.
Hypertensive Emergencies 1. Sodium Nitroprusside - Drug of choice in most hypertensive emergencies. - Allows controlled reduction of blood pressure. - Given by continuous intravenous infusion. - Very potent vasodilator, can reduce blood pressure to hypotensive levels in few minutes if increase the dose. - Requires careful monitoring of blood pressure; check blood pressure every minute or use intra arterial line. - Onset of hypotensive action is immediate and action disappears within few minutes when stop the infusion. Excessive fluctuations of blood pressure are likely. - Dosage: 0.5-10 mg/Kg/min. - Side effects: Nausea, vomiting, cyanide toxicity. - Drug should be protected from light. - When used in aortic dissection, parentral beta blocker must be given first (i.v. Propranolol 1 mg/5 min). 2. Diazoxide - Arterial vasodilator with the following advantages: 1. No need for minute to minute monitoring. 2. Has sustained action, no excessive blood pressure fluctuations. - Onset of action in 1-5 minutes and duration of action 6-12 hours. - Dosage: 50-100 mg i.v. bolus every 5-10 minutes up to 600 mg or 10-30 mg/min i.v. infusion. - Side effects: reflex sympathetic stimulation, tachycardia, fluid retention, hyperglycemia, exacerbate myocardial ischemia and aortic dissection. 3. Labetalol - Combined beta and alpha adrenergic blocker. - i.v. infusion 0.5-2.0 mg/min. - Dosage: i.v. bolus 20-80 mg every 5-10 minutes up to 500 mg. - Hypertensive Emergencies - Onset of action is 5-10 minutes and duration is 3-6 hours. - Indicated in hyperadrenergic states, perioperative hypertension, pheochromocytoma, clonidine withdrawal, aortic dissection and abuse of sympathomimetics. 4. Parentral Drugs Given in Special Situations a. i.v. nitroglycerine: Indicated in unstable angina, acute myocardial infarction, left ventricular failure, perioperative hypertension. Dose: 5-100 mg/min as i.v. infusion. Duration of action is 3-5 minutes. b. Phentolamine: Indicated in the adrenergic crisis of catecholamine excess, such as pheochromocytoma, combined intake of monoamine oxidase inhibitors with tyramine rich foods (old cheese, wine, beans, etc.) or sympathomimetics, sudden hypertension following clonidine (or similar drugs) withdrawal. Dose: i.v. bolus 5-10 mg every 5 to 15 minutes. c. Hydralazine: Indicated in eclampsia. Dose: i.v. bolus 5-10 mg every 20 minutes. Action starts in 10-20 minutes and lasts for 3-6 hours. Oral Medications · Used in patients with hypertensive urgencies. · Aim is to achieve reduction of mean arterial pressure by 20% or a diastolic pressure below 120 mmHg. Preparations 1. Nifedipine: Sublingual or buccal, has onset of action in 5-10 minutes with a duration of 3-6 hours. Dose: 10-20 mg repeated at 10-15 minutes. 2. Clonidine: Given orally with onset of action in 30-60 minutes and duration of action 8-12 hours.
Dose: 0.1-0.2 mg, then 0.05-0.1 mg every hour up to 0.7 mg. Should be avoided in patients with bradycardia, heart block or sick sinus syndrome. 3. Converting Enzyme Inhibitors: Captopril. Drug of choice in renal vasculitis and scleroderma hypertensive crisis. Action depends on blood volume status – significant hypotensive action is produced in volume depletion and hyponatremia. Dose: 10-50 mg with onset of action 15-30 minutes, can be given oral or sublingual. Summary of Treatment of Hypertensive Crisis 1. Labetalol (best all-around choice): 20 mg intravenously, then 40 to 80 mg intravenously every 10 minutes as needed (maximum 300 mg) or continuous infusion at 2 to 5 mg/h. 2. Nitroprusside: 0.5 to 10 µg/Kg/min; avoid in MI (use nitroglycerin); side effects include thiocyanate poisoning, which usually occurs at levels above 12 mg/dl (see somnolence, weakness, aphasia, twitching, diaphoresis, and tinnitus); minimize risk by avoiding in renal failure and limiting use to 24 to 48 hours. 3. Esmolol: (short acting beta blocker) 500 µg/Kg loading dose, then 50 to 300 µg/Kg/min; side effects include wheezing. 4. Phentolamine (specific uses include monoamine oxidase inhibitor/tyramine crisis, pheochromocytoma and cocaine toxicity): 5 to 10 mg intravenously, repeated as needed up to 20 mg. 5. Enalaprilat (use in scleroderma crisis): 1.25 to 5.0 mg every 6 hours; when converting to oral agent, high-doses are often beneficial (e.g., captopril 100-150 four times daily). Hypertensive Emergencies 6. Propranolol (useful in thyroid storm): 2 to 10 mg intravenously every 3 to 4 hours, 0.5 to 1.0 mg/min continuous intravenous infusion, or 40 to 80 mg orally every 6 hours. 7. Other: Clonidine 0.1 to 0.2 mg orally then 0.05 to 0.1 mg every hour until DBP is below 110 mmHg, nimopidine (Ca channel blocker) 60 mg every 4 hours (useful in subarachnoid hemorrhage).
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