A silent killer : Hypertension
In children and adolescents, hypertension is generally defined as systolic and/or diastolic blood pressure consistently >95th percentile for age, gender, and height.
Blood pressures between the 90th and 95th percentiles are considered prehypertensive and are an indication for lifestyle interventions.
A recent classification recommends blood pressure criteria for defining normal blood pressure, prehypertension, hypertension (stages I and II), and isolated systolic hypertension, which is a common occurrence among the elderly.
Blood Pressure Classification
Causes of secondary hypertension
Alcohol
Obesity
Pregnancy (pre-eclampsia)
Renal disease (Ch. 17) Renal vascular disease,Parenchymal renal disease, particularly glomerulonephritis , Polycystic kidney disease
Endocrine disease Phaeochromocytoma, Cushing's syndrome, Primary hyperaldosteronism (Conn's syndrome), Hyperparathyroidism, Acromegaly, Primary hypothyroidism, Thyrotoxicosis, Congenital adrenal hyperplasia due to 11-β-hydroxylase or 17-hydroxylase deficiency, Liddle's syndrome,11-β-hydroxysteroid dehydrogenase deficiency.
Drugs e.g. Oral contraceptives containing oestrogens, anabolic steroids, corticosteroids, non-steroidal anti-inflammatory drugs, carbenoxolone, sympathomimetic agents
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
Patient's Relevant History
Duration of hypertension
Previous therapies: responses and side effects
Family history of hypertension and cardiovascular disease
Dietary and psychosocial history
Other risk factors: weight change, dyslipidemia, smoking, diabetes, physical inactivity
Evidence of secondary hypertension: history of renal disease; change in appearance; muscle weakness; spells of sweating, palpitations, tremor; erratic sleep, snoring, daytime somnolence; symptoms of hypo- or hyperthyroidism; use of agents that may increase blood pressure
Evidence of target organ damage: history of TIA, stroke, transient blindness; angina, myocardial infarction, congestive heart failure; sexual function.
History and Examination
History- family history, life style (exercise, salt intake, smoking habit), and other risk factors. Drug or alcohol consumption, other features of secondary hypertension causes eg. Pheochromocytoma (paroxysmal headache, palpitation and sweating.)
Examination- measure blood pressure, look for radio-femoral delay, enlarged kidneys (PKD), abdominal bruits (renal artery stenosis), and characteristic facies and habitus of Cushing’s syndrome, central obesity and xanthomas.
Target organ damage
Retinal changes in hypertension. Grade 4 hypertensive retinopathy showing swollen optic disc, retinal haemorrhages and multiple cotton wool spots (infarcts). Central retinal vein thrombosis showing swollen optic disc and widespread fundal haemorrhage, commonly associated with systemic hypertension.
Hypertensive encephalopathy-
A rare condition characterised by high blood pressure and neurological symptoms.
Includs transient disturbances of speech or vision, paraesthesiae, disorientation, fits and loss of consciousness. Papilloedema is common.
A CT scan of the brain often shows haemorrhage in and around the basal ganglia; however, the neurological deficit is usually reversible if the hypertension is properly controlled.
‘Malignant’ or ‘accelerated’ phase hypertension
A rare condition which may complicate hypertension of any etiology.
Characterized by accelerated microvascular damage with necrosis in the walls of small arteries and arterioles (fibrinoid necrosis) and by intravascular thrombosis.
Diagnosis based on- high blood pressure and
Rapidly progressive end organ damage- such as retinopathy of grade 3 or 4, renal dysfunction (proteinuria), and/or hypertensive encephalopathy.
Left ventricular failure may occur and if not treated death may occur within months.
Investigation of all patients
Urinalysis for blood, protein and glucose
Blood urea, electrolytes and creatinine
Blood glucose
Serum total and high-density lipoprotein (HDL) cholesterol
12-lead ECG (left ventricular hypertrophy, coronary artery disease)
Investigations in selected patients
Chest X-ray: to detect cardiomegaly, heart failure, coarctation of the aorta
Ambulatory BP recording: to assess borderline or 'white coat' hypertension
Echocardiogram: to detect or quantify left ventricular hypertrophy
Renal ultrasound: to detect possible renal disease
Renal angiography: to detect or confirm presence of renal artery stenosis
Urinary catecholamines: to detect possible phaeochromocytoma.
Treatment
Lifestyle Modifications to Manage Hypertension
Antihypertensive drugs
Thiazide and other diuretics- mechanism of action is incompletely understood. A daily dose of 2.5 mg bendroflumethiazide or 0.5 mg cyclopenthiazide is appropriate. Furosemide(loop diuretics) have few advantages over thiazides in hypertension.
Beta-adrenoceptor antagonists (β-blockers)- Metoprolol (100-200 mg daily), atenolol (50-100 mg daily) and bisoprolol (5-10 mg daily) are cardioselective.
Labetalol and carvidilol- are combined β- and α-adrenoceptor antagonists. Labetalol (200 mg-2.4 g daily in divided doses) and carvedilol (6.25-25 mg 12-hourly).
Angiotensin-converting enzyme (ACE) inhibitors: e.g. enalapril 20 mg daily, ramipril 5-10 mg daily or lisinopril 10-40 mg daily. 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.
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.
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.
Other drugs- 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.
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.
Adjuvant drug therapy – Aspirin and Statins.
It is unwise to lower blood pressure too quickly because this may compromise tissue perfusion (due to altered autoregulation) which may lead to 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.
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.
