Hypertensive EMERGENCY

Hypertensive EMERGENCY

The situation is a true hypertension emergency when there is acute and life-threatening organ damage, such as hypertensive encephalopathy (headache, lethargy, seizures, coma), intra-cranial haemorrhage, aortic dissection, acute coronary syndromes (unstable angina/acute myocardial infarction), acute left ventricular failure with pulmonary oedema, or pre-eclampsia/eclampsia. The initial aim of treatment is to lower blood pressure in a rapid (within 2-6 hours), controlled but not overzealous way, to safe (not normal) levels – about 160mmHg systolic and 100mmHg diastolic, with the maximum initial fall in blood pressure not exceeding 25% of the presenting value. Too rapid a fall in pressure may precipitate cerebral or myocardial infarction, or acute renal failure.

Hypotensive agents should be administered intravenously when organ damage is potentially life-threatening. All patients should be admitted to a high dependency or intensive care bed, for continuous BP monitoring. The choice of drug will frequently depend on the underlying cause or the organ most compromised. In many instances, patients will be salt and water deplete and will require fluid replacement with normal saline in addition to antihypertensive agents. 

Antihypertensive Agents

Sodium nitroprusside 

Arteriolar and venous dilator. Considered to be the most effective parenteral drug for most hypertensive emergencies (except myocardial ischemia or renal impairment). It dilates both arteries and veins, and it reduces afterload and preload. Onset: within seconds. Duration: 2-3 minutes. Constant monitoring of the blood pressure is required. Alternatives to nitroprusside include intravenous labetalol, nicardipine, and fenoldopam. Hypotension is uncommon with these drugs and cyanide toxicity is not an issue. 

Dosing (Adults): Initial: 0.3-0.5 mcg/kg/minute. Increase in increments of 0.5 mcg/kg/minute -- titrating to the desired hemodynamic effect or the appearance of headache or nausea. Usual dose: 3 mcg/kg/minute (rarely need >4 mcg/kg/minute). Maximum: 10 mcg/kg/minute. 

When treatment is prolonged (>24 to 48 hours) or when renal insufficiency is present, the risk of cyanide and thiocyanate toxicity is increased. Doses > 2 mcg/kg/min exceed the capacity of the body to detoxify cyanide. Maximum doses of 10 mcg/kg/min should never be given for more than 10 minutes. An infusion of sodium thiosulfate can be used in affected patients to provide a sulfur donor to detoxify cyanide into thiocyanate. 

Glyceryl trinitrate (GTN) 

Primarily a venous dilator (lesser degree - arteriolar dilator). It may be most useful in patients with symptomatic coronary disease and in those with hypertension following coronary bypass. Drug of choice for hypertensive emergencies with coronary ischemia. It should not be used with hypertensive encephalopathy because it increases ICP. Tolerance may occur within 24-48 hours. Nitrate-free interval (10-12 hours/day) is recommended to avoid tolerance development.

Dosing (Adults): (IV): Initial dose: 5 mcg/min IV infusion. Increase by 5 mcg/minute every 3-5 minutes to 20 mcg/minute. If no response at 20 mcg/minute increase by 10 mcg/minute every 3-5 minutes, up to a maximum of 200 mcg/minute. 

Onset: 2 to 5 minutes. Duration: 5 to 10 minutes. 

Labetolol

Combined beta-adrenergic (B1 and B2) and alpha-adrenergic blocker. Its rapid onset of action (~ 5 minutes) makes it the only beta-blocker that is useful in the treatment of hypertensive emergencies. Safe in patients with active coronary disease, since it does not increase the heart rate. Labetalol should generally be avoided in patients with asthma, COPD, CHF, bradycardia, or greater than first-degree heart block. Causes marked orthostatic effects.

Dosing (Adult): can be given as an IV bolus or infusion. The bolus dose is 20 mg initially (over 2 min), followed by 20 to 80 mg every 10 minutes to a total dose of 300 mg. The infusion rate is 0.5 to 2 mg/min. Onset/duration: 5-10 min/2-6 hr. Peak effect in 30 minutes. 

Hypertension (Oral): Initial: 100 mg twice daily - may increase as needed every 2-3 days by 100 mg until desired response is obtained. Usual dose: 200-400 mg twice daily - not to exceed 2.4 grams/day. 

Hydralazine

Direct arteriolar vasodilator with little or no effect on the venous circulation. Precautions are needed in patients with underlying coronary disease or an aortic dissection. Beta-blocker should be given concurrently to minimize reflex sympathetic stimulation. The hypotensive response to hydralazine is less predictable than that seen with other parenteral agents.

Dosing (Adult): Initial (Acute hypertension): 10 mg slow IV bolus (maximum dose being 20 mg) every 4 to 6 hours as needed. May increase to 40 mg/dose (generally speaking - do not exceed 20mg/dose). Change to oral therapy as soon as possible. The fall in blood pressure begins within 10 to 30 minutes and lasts 2 to 4 hours. May also be given IM. 

Phentolamine

 A short-acting a-blocker, can be used in the first instance when a phaeochromocytoma is known or strongly suspected. It is given by slow intravenous injection, in doses of 2-5mg over 1 minute, repeated as necessary every 5-15 minutes. 

Beta-1 selective blocker. Rapidly metabolized by blood esterases (short half-life ~ 9 minutes) and total duration of action ~ 30 minutes. Its effects begin almost immediately. 

  

Dosing (Adult): 500 mcg/kg IV bolus over 1 minute, and start infusion at 50 - 100 mcg/kg/min => repeat bolus dose of 500 mcg/kg if no effect within 5 minutes and increase dose by 50 mcg/kg/min. Repeat cycle every 5 minutes until maximum infusion dose of 300 mcg/kg/min. 

Contraindicated in cocaine toxicity (if used alone) and LVF and COPD/asthma and high-grade heart block. Causes phlebothrombophlebitis - use large vein's. Causes local necrosis if extravasation occurs. 

Onset/duration:1-5 min/15-30 min. 

Fenoldopam

A rapid-acting vasodilator. It is an agonist for D1-like dopamine receptors and binds with moderate affinity to 2-adrenoceptors. Fenoldopam: effective as nitroprusside, however, it has the advantages of increasing renal blood flow (6 times as potent as dopamine in producing renal vasodilitation) and sodium excretion, of not being associated with the accumulation of toxic metabolites, and not requiring shielding from light. Fenoldopam can be safely used in all hypertensive emergencies, and may be particularly beneficial in patients with renal insufficiency. 

Dosing (Adult): After a starting dose of 0.1 to 0.3 mcg/kg/minute, the dose is titrated at 15 minute intervals, depending on the BP response. May be increased in increments of 0.05 to 0.1 mcg/kg/minute every 15 minutes until target blood pressure is reached. Maximal infusion rate reported in clinical studies: 1.6 mcg/kg/minute. Onset/duration: 5-10 minutes/~ 1 hour 

Nicardipine Dihydropyridine calcium channel blocker. Advantages: Does not depress LV function; does not adversely increase ICP (acceptable choice in stroke patients). Major limitation: longer half-life, which precludes rapid titration. Contraindicated in heart block, recent AMI, and renal failure. 

(Acute hypertension) - The initial dose is 5 mg/hour and can be increased to a maximum of 15 mg/hour. Effects seen within 15 minutes. Initial dose of 5 mg/hr can be increased by 2.5 mg/hour every 15 minutes to the previously listed maximum of 15 mg/hour. Consider reduction to 3 mg/hour after response is achieved. Monitor and titrate to lowest dose necessary to maintain stable blood pressure. 

Malignant Hypertension 

Malignant (accelerated) hypertension is a syndrome characterised by severely elevated blood pressure accompanied by retinopathy (retinal haemorrhages, exudates or papilloedema), nephropathy (malignant nephrosclerosis) with or without encephalopathy and microangiopathic haemolytic anaemia. It is usually a consequence of untreated essential or secondary hypertension. Most patients who present with malignant hypertension have volume depletion secondary to pressure naturesis. Therefore further diuresis may exacerbate the hypertension and may cause further deterioration in kidney function.

Aortic Dissection 

Aortic dissection must be excluded in any patient presenting with severe hypertension and chest, back, or abdominal pain. It is life-threatening with very poor prognosis if not treated. The initial treatment is a combination of IV b-blocker (e.g. labetalol) and a vasodilator (e.g. sodium nitoprusside or dihydropyridine CCB) to decrease systolic blood pressure below 120 mmHg if tolerated.

Drug Of Choice According To Clinical Diagnosis

Increased intracranial Pressure Or Renal Disease :

• Labetolol 
• Nicardipine 
• Fenoldopam

Normal Intracranial Pressure And Renal Function

• Sodium nitroprusside 
• Nicardipine

Acute Ischaemic Stroke

• Labetolol 
• Nicardipine 
• Sodium nitroprusside

Myocardial Ischaemia/Infarction

• Esmolol and Glyceryl Trinitrate 
• Labetalol and Glyceryl trinitrate 
• Sodium Nitroprusside

Left Ventricular Failure And/Or Pulmonary Oedema

• Glyceryl Trinitrate and Furosemide
• Sodium Nitroprusside and Furosemide 

Aortic Dissection

• Labetolol 
• Esmolol 
• Sodium Nitroprusside

Acute Renal Failure

• Fenoldopam 
• Nicardipine

Eclampsia

• Hydralazine
• Labetalol
• Nicardipine
• Magnesium