Download 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 αadrenoceptor antagonists which are 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 α1adrenoceptor 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 αblockers) 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.
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