LAS CUATRO PREGUNTAS DE LA INVESTIGACION CIENTIFICA

• Hypertensive crisis is defined as a substantial acute increase in blood pressure, usually with diastolic blood pressure over 120 mmHg with or without end-organ damage.

• It can be further classified into:

(i) Hypertensive emergencies - increased blood pressure with evidence of end-organ damage or dysfunction.

• End-organ manifestations include [1] retinal eg. papilloedema [2]

cardiac eg. pulmonary oedema, myocardial ischaemia such as unstable angina or infarction [3] neurological eg. severe headache, mental status changes, seizure, coma and [4] renal eg. acute renal failure.

(ii) Hypertensive urgencies - elevation of blood pressure to a level which may be potentially harmful, but without signs, symptoms or other evidence of end-organ dysfunction.

A. Management 1. General principles:

• In hypertensive emergencies, blood pressure control should be

accomplished within a few hours to reduce the risk of permanent damage or death (diastolic of 100-110 mmHg may be adequate for the first 24 hours). IV antihypertensive agents should be used.

• In hypertensive urgencies, blood pressure control can be accomplished more slowly with oral antihypertensive agents within 24-48 hrs to a diastolic level of 100-110 mmHg initially. Excessive or rapid decreases in BP should be avoided to minimize the risk of cerebral hypoperfusion or coronary insufficiency.

• BUSE, creatinine, urinalysis, CXR and ECG should be performed urgently.

• Drugs of choice for management:

a. Coronary artery disease and heart failure: IV nitroprusside or nitroglycerin

b. Pheochromocytoma: IV phentolamine or alpha-blocker eg. prazosin c. Aortic dissection: IV beta-blockers or labetalol +/- nitroprusside d. Pulmonary oedema: IV frusemide, IV nitroprusside, ACE inhibitors e. Hypertension in pregnancy: Hydralazine, labetalol and magnesium

sulphate

f. Stroke: Beta-blockers, diuretics or ACE inhibitors.

• Sublingual nifedipine SHOULD BE AVOIDED.

• IV diazoxide should be discouraged.

2. Oral antihypertensive agents:

• Can be used in patients with hypertensive crisis when urgent but not immediate reduction of BP is indicated. Combination therapy is necessary for most cases when diastolic blood pressure is > 110 mmHg.

• Beta-blockers eg. atenolol 100mg with or without diuretics, or oral captopril 12.5mg with or without diuretics may be all that is required. If

nifedipine is contemplated, it should be used with careful monitoring of blood pressure to avoid precipitous drop.

3. Parenteral antihypertensive agents:

• Indicated in hypertensive emergencies or individuals with hypertensive urgencies who are in need of emergency surgery.

a. Sodium nitroprusside:

• A direct-acting arterial and venous vasodilator, is the treatment of choice for virtually all hypertensive crises.

• It reduces BP rapidly, is easily titratable, and its action is short-lived when discontinued.

• Dosage - (mix 50mg in 250ml of D5%= 200mcg/ml; 10mcg/min = 3 ml/hr), start at 0.5mcg/kg/min and titrate until the desired blood pressure has been achievedor maximal dose is reached, which ever comes first. Average effective dose is 3mcg/kg/min (range from 0.5-8mcg/kg/min). Stop if marked response not obtained with max. dose in 10 minutes.

• Contraindications are severe coronary disease, advanced hepatic or renal insufficiency.

• Therapy for more than 24 hours, in high doses, or in the presence of renal and hepatic insufficiency may cause thiocyanate toxicity as manifested by tinnitus, blurred vision, seizures, or delirium.

• Side effects include headache, dizziness, nausea, abdominal pain and renal impairment

b. Nitroglycerin:

• Drug of choice for moderate hypertension complicating unstable angina or myocardial infarction or when sodium nitroprusside is contraindicated.

• Dosage - (50mg in 250ml of NS or D5% = 200mcg/ml; 10mcg/ml = 3ml/hr) start at 5-10mcg/min and titrate until the desired BP is achieved or up to 200mcg/min.

c. Labetalol:

• Alpha-1 and beta blocker with beta-alpha ratio of 7:1.

• Can be given by slow boluses or continuous infusion.

• The usual precautions for beta blockers should be observed.

• (i) Bolus - IV 50 mg over 1-5 min and can be repeated every 5-10min till maximum doses of 200-300mg or until desired BP is achieved.

Maximum response occur in 5-10 min and may last for up to 6 hours.

Oral dosing can then be started at eg. 200mg 12hourly (max 2400mg/day).

(ii) Infusion - Mix 200mg in 200ml of D5% and run at 1-2mg/min (1-2ml/min). When goal blood pressure is achieved, the infusion should be stopped and oral medication can be started.

• Excessive bradycardia can be countered with IV atropine 0.5-2mg in divided doses of 0.5mg.

d. Hydralazine:

• A direct arteriolar dilator, with an onset of action within 10 min after an IV dose and a duration of action of 3-8 hours.

• 5-20mg IV may be given, repeated if necessary at about 15-30min intervals, to a maximum of 50mg. Alternately it can be given as infusion (eg. 50mg of hydralazine in 500 ml of normal saline = 100mcg/ml; 50mcg/min = 30ml/hr) start with 50 mcg/min and titrate to reduce the BP gradually (usually 50-150mcg/min).

• This drug is best avoided in the presence of coronary arterial disease because of reflex tachycardia.

e. Esmolol:

• This is a relatively cardioselective beta blocker with a very short duration of action, used intravenously for the short term treatment, particularly in the perioperative period.

• Dilute 2.5g in 250ml of normal saline or 5% dextrose solution to a concentration of 10 mg/ml.

• A loading dose of 500mcg/kg/min for 1 min should be given followed by maintenance dose starting at a dose of 50mcg/kg/min and titrate within a range of infusion of 50-200 mcg/kg/min.

• Usual precautions for beta blockers should be observed.

4. Subsequent therapy:

• Investigate for possible underlying causes.

• If parenteral agents are used initially, oral medications should be

administered often in combination shortly thereafter to facilitate weaning from parenteral therapy (over 1-2 days).

_ ATRIAL FIBRILLATION