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Fifth stage
Medicine
Lec-4
د . منوع
1/1/2014
HYPERTENSION
MEASUREMENT OF BLOOD PRESSURE
• Use a machine that has been validated, well maintained and properly calibrated
• Measure sitting BP routinely, with additional standing BP in elderly and diabetic patients
and those with possible postural hypotension
• Remove tight clothing from the arm
• Support the arm at the level of the heart
• Use a cuff of appropriate size (the bladder must encompass > two-thirds of the arm)
• Lower the mercury slowly (2 mm per second)
• Read the BP to the nearest 2 mmHg
• Use phase V (disappearance of sounds) to measure diastolic BP
• Take two measurements at each visit
TREATMENT OF HYPERTENSION
Antihypertensive drugs
1. Thiazide and other diuretics.
The mechanism of action of these drugs is incompletely understood, and it may take up to a
month for the maximum effect to be observed.
A daily dose of 2.5 mg bendroflumethiazide or 0.5 mg cyclopenthiazide is appropriate.
More potent loop diuretics, such as furosemide 40 mg daily or bumetanide 1 mg daily, have
few advantages over thiazides in the treatment of hypertension unless there is substantial
renal impairment or they are used in conjunction with an ACE inhibitor.
2. Beta-adrenoceptor antagonists (β-blockers).
Metoprolol (100-200 mg daily), atenolol (50-100 mg daily) and bisoprolol (5-10 mg daily)
are cardioselective and therefore preferentially block the cardiac β1-adrenoceptors, as
opposed to the β2-adrenoceptors that mediate vasodilatation and bronchodilatation.
Labetalol and carvedilol. Labetalol (200 mg-2.4 g daily in divided doses) and carvedilol
(6.25-25 mg 12-hourly) are combined β- and α-adrenoceptor antagonists which are
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sometimes more effective than pure β-blockers. Labetalol can be used as an infusion in
malignant phase hypertension.
3. Angiotensin-converting enzyme (ACE) inhibitors.
These drugs (e.g. captopril, enalapril 20 mg daily, ramipril 5-10 mg daily or lisinopril 10-40
mg daily) inhibit the conversion of angiotensin I to angiotensin II and are usually well
tolerated. They should be used with particular care in patients with impaired renal function
or renal artery stenosis because they can reduce the filtration pressure in the glomeruli and
precipitate renal failure. Electrolytes and creatinine should be checked before and 1-2
weeks after commencing therapy. Side-effects include first-dose hypotension, cough, rash,
hyperkalaemia and renal dysfunction.
Angiotensin receptor blockers: These drugs (e.g. losartan 50-100 mg daily, valsartan 40-160
mg daily) block the angiotensin II type I receptor and have similar effects to ACE inhibitors
but do not cause cough and are better tolerated.
4. Calcium antagonists:
The dihydropyridines (e.g. amlodipine 5-10 mg daily, nifedipine 30-90 mg daily) are
effective and usually well-tolerated antihypertensive drugs that are particularly useful in
the elderly. Side-effects include flushing, palpitations and fluid retention. The rate-limiting
calcium antagonists (e.g. diltiazem 200-300 mg daily, verapamil 240 mg daily) can be useful
when hypertension coexists with angina but they may cause bradycardia. The main side-
effect of verapamil is constipation
5. Other drugs.
A variety of vasodilators are used to treat hypertension. These include the α1-adrenoceptor
antagonists (α-blockers), such as prazosin (0.5-20 mg daily in divided doses), indoramin (25-
100 mg 12-hourly) and doxazosin (1-16 mg daily), and drugs that act directly on vascular
smooth muscle, such as hydralazine (25-100 mg 12-hourly) and minoxidil (10-50 mg daily).
Side-effects include first-dose and postural hypotension, headache, tachycardia and fluid
retention. Minoxidil also causes increased facial hair and is therefore unsuitable for female
patients.
Centrally acting drugs, such as methyldopa (initial dose 250 mg 8-hourly) and clonidine
(0.05-0.1 mg 8-hourly), are effective antihypertensive drugs but cause fatigue and are usually
poorly tolerated
Choice of antihypertensive treatment
Trials that have compared the major classes of antihypertensive drug (thiazides, β-blockers,
calcium antagonists, ACE inhibitors and α-blockers) have shown no consistent or important
differences in outcome, efficacy, side-effects or quality of life . The choice of
antihypertensive therapy is therefore usually dictated by cost, convenience, the response
to treatment and freedom from side-effects.
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comorbid conditions may have an important influence on initial drug selection ; for
example, a β-blocker might be the most appropriate treatment for a patient with angina
unless there is also a history of asthma. Thiazide diuretics and dihydropyridine calcium
antagonists are the most suitable drugs for the treatment of high blood pressure in elderly
people.
Although some patients can be satisfactorily treated with a single antihypertensive drug, a
combination of drugs is often required to achieve optimal blood pressure control.
Combination therapy may be desirable for other reasons; for example, low-dose therapy
with two or three drugs may produce fewer unwanted effects than treatment with the
maximum dose of a single drug.
• Some drugs have complementary or synergistic actions . for example, thiazides
increase activity of the renin-angiotensin system while αCE inhibitors block it.
The emergency treatment of accelerated phase or malignant hypertension
In accelerated phase hypertension, it is unwise to lower blood pressure too quickly because
this may compromise tissue perfusion (due to altered autoregulation) and can cause
cerebral damage, including occipital blindness, and precipitate coronary or renal
insufficiency. Even in the presence of cardiac failure or hypertensive encephalopathy, a
controlled reduction, to a level of about 150/90 mmHg, over a period of 24-48 hours is
ideal.
In most patients it is possible to avoid parenteral therapy and bring blood pressure under
control with bed rest and oral drug therapy. Intravenous or intramuscular labetalol (2
mg/min to a maximum of 200 mg), intravenous glyceryl trinitrate (0.6-1.2 mg/hour),
intramuscular hydralazine (5 or 10 mg aliquots repeated at half-hourly intervals) and
intravenous sodium nitroprusside (0.3-1.0 μg/kg body weight per minute) are all effective
remedies but require careful supervision, preferably in a high-dependency unit.
REFRACTORY HYPERTENSION
The common causes of treatment failure in hypertension are non-adherence with drug
therapy, inadequate therapy, and failure to recognise an underlying cause such as renal
artery stenosis or phaeochromocytoma; of these, the first is by far the most prevalent.
There is no easy solution to compliance problems, but simple treatment regimens,
attempts to improve rapport with the patient and careful supervision may all help.
Adjuvant drug therapy
• Aspirin.
• Statins. Treating hyperlipidaemia can also produce a substantial reduction in
cardiovascular risk. These drugs are strongly indicated in patients who have
established vascular disease, or hypertension with a high (> 15% in 10 years) risk of
developing coronary heart disease