Hypertension Types and Causes

Hypertension

Hypertension is defined by 2 or more measurements of blood pressure greater than 140/90 mmHg. The degree of end-organ damage and morbidity and mortality correlate with the duration and severity of hypertension (HTN). Ischemic heart disease is the most common form of organ damage associated with HTN. Heart failure, renal failure, and cerebrovascular disease (stroke) are also common complications in hypertensive patients.

Systemic hypertension is characterized as essential or primary hypertension (95% all cases of systemic hypertension)) when a cause for the increased blood pressure cannot be identified. It is termed secondary hypertension (5% of all cases of systemic hypertension) when an identifiable cause is present such as pheochromocytoma (tumor of the symatho-adrenal system that produce adrenaline which causes hypertension), renal vascular stenosis, hyperaldestronism, etc.

Treatment of Essential Hypertension

Decreasing blood pressure by lifestyle modification and pharmacologic therapy is intended to decrease morbidity and mortality. The standard goal of therapy is to decrease systemic blood pressure to lower than 140/90 mm Hg. Treatment resulting in normalization of blood pressure has been particularly successful in decreasing the incidence of cerebrovascular accidents, ischemic heart disease, congestive heart failure and renal failure.

• Life style modification: Lifestyle modifications of proven value for lowering blood pressure include weight reduction or prevention of weight gain, moderation of alcohol intake, increased physical activity, and moderation in dietary salt intake. Smoking cessation is critical because smoking is an independent risk factor for cardiovascular disease.
• Sodium restriction: sodium restriction can minimize diuretic-induced hypokalemia and may enhance the ease of blood pressure control with diuretic therapy. Salt substitutes in which sodium is replaced with potassium are useful for hypertensive patients who do not have renal dysfunction.
• Drug therapy: A large variety of antihypertensive drugs are available, and many of these drugs present unique and potentially significant advantages and side effects (Table 1.2).
Diuretics: They are often the first line drugs, and reduce extra cellular fluid volume. Hydrochlorothiazide 25 mg PO daily and may be increased gradually. Side effects of thiazide diuretics include hypokalemia, hyperuricemia (abnormal amount of uric acid in the blood) and hyperglycemia.
Beta (β)-adrenergic blocking agents: reduce cardiac output and rennin release. β-blockers commonly used are Propranolol 20 mg PO /day to Maximum of 120 mg PO 4X/day, Metoprolol 25 - 150 mg PO BID, Atenolol25-100 mg PO/day. Side effects of beta blockers are bronchospasm, bradycardia, worsening of heart failure, impotence and depression. Not used in the presence of asthma and severe peripheral vascular disease.
Centrally acting agents: e.g., methyldopa: 250 mg -1000 mg PO BID, TID or QID. This agent inhibit sympathetic out flow from the central nervous system. Side effects include postural hypotension, depression and gynaecomastia
Vasodilators: e.g., hydralazine: 10-50 mg IV or PO every 6 hours dilate arterioles and arteries, reducing peripheral vascular resistance which in turn reduces high blood pressure. Side effect includes head ache
Calcium channel blockers: e.g., Nifedipine: 30 - 90 mg PO daily, by modulating calcium release in smooth muscles, calcium channel blockers reduces smooth muscle tone, resulting vasodilatation. Not used in heart block, heart failure.
Angiotensin converting enzyme (ACE) inhibitors: e.g., captopril, 12.5 -75 mg PO BID, Enalapril 2.5-40 mg daily inhibits the conversion of angiotensin I to angiotensin II (a potent vasoconstrictor). Side effects include cough, leucopenia, angioedema, hyperkalemia. Not used in renal failure.

Table 1.2 Commonly Used Antihypertensive Drugs for Emergency Treatment of Hypertension