Hypertension

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Introduction

Hypertension is a persistent elevation of the blood pressure above normal values (≥140/90 mmHg) taken 2 to 3 times on at least two different occasions.

It is the commonest non-communicable disease in the world.

Clinical features

  • Largely asymptomatic until complications arise (“silent killer”)
  • Symptoms and signs of target organ diseases e.g. cardiac failure, stroke and chronic kidney disease

Complications

  • Heart: Heart failure, ischaemic heart disease
  • Brain: Stroke (ischaemic, hemorrhagic)
  • Eye: Hypertensive retinopathy
  • Kidney: Renal failure
  • Peripheral artery disease

Investigations

  • Urinalysis; urine microscopy
  • Electrolytes, Urea and Creatinine.
  • Uric acid
  • Fasting blood glucose
  • Lipid profile
  • Chest radiograph
  • Electrocardiography
  • Others as may be indicated:
    • Echocardiography
    • Abdominal ultrasound
    • Renal angiography

Treatment objectives

  • Educate patient about disease and need for treatment adherence
  • Reduce blood pressure to acceptable levels
  • Prevent complications (primary, secondary, tertiary)

Non-drug treatment (lifestyle modification)

  • Low salt diet: Not more than 1 level teaspoon of salt per day; No added salt; Avoid food preserved with salt
  • Achieve/maintain ideal body weight (BMI 18.5-24.9 Kg/m²)
  • Stop smoking years
  • Reduce alcohol intake
  • Regular exercise
  • Reduce polysaturated fatty acid intake

Drug treatment

Principles of drug treatment

  • Treatment should be individualized
  • Most patients will require combination chemotherapy using drug from different classes
  • Fixed dose combination is desirable when 2 or more drugs are required
  • Drugs with at least 24 hours duration of action to ensure once daily dosing
  • Diuretics should be included unless contraindicated
  • ACEI and beta blockers are ineffective when used as monotherapy in blacks
  • Treat coexisting cardiovascular risk factors
  • All patients require lifestyle modifications

Choice of drugs

Diuretics:

Thiazides

  • Bendroflumethiazide 2.5 – 10 mg orally daily

Or:

  • Hydrochlorothiazide 12.5- 50 mg orally daily

Or:

  • Hydrochlorothiazide/amiloride 25/2.5 mg daily

Beta Blockers:

  • Atenolol 25-100 mg orally daily

Calcium channel antagonists:

  • Nifedipine retard 20-40 mg orally once or twice daily

Or:

  • Amlodipine 2,5-10 mg orally once daily

Angiotensin converting enzyme inhibitors:

  • Captopril 6.25-50 mg orally once or every 8 – 12 hours

Or:

  • Lisinopril 2.5-20 mg orally once daily

Angiotensin receptor blockers:

  • Losartan 50-100 mg orally daily
  • Valsartan 80-160 mg daily

Other vasodilators:

  • Hydralazine 25-100 mg orally once daily or every 12 hours

Or:

  • Prazosin 0.5-1 mg orally daily

Centrally acting drugs:

  • Alpha methyldopa 250 – 500 mg orally twice, three or four times daily

Hypertensive emergencies

  • Treatment should be done by the experts. This involves the administration of antihypertensives by the parenteral route (usually intravenous hydralazine or sodium nitoprusside)

Notes on anti-hypertensive medicines

  • Any of the five classes of major antihypertensive drugs can be used as first-line treatment. These are:
    1. Thiazide Diuretics
    2. Calcium Channel Blockers
    3. Angiotensin Converting Enzyme Inhibitors
    4. Angiotensin Receptor Blockers
    5. Beta-blockers
  • In the general black population, thiazide diuretics or calcium channel blockers, either as monotherapy or in some combination therapy, is preferrable.
  • Angiotensin converting enzyme Inhibitors are not recommended as first-line drugs for uncomplicated hypertension in black patients.
  • Dual therapy should be started earlier when the blood pressure exceeds 180/110 mmHg.
  • Additional anti-hypertensive drugs should be used if target blood pressure levels are not achieved.
  • Add-on drugs should be chosen from first-line choices bearing in mind compelling indications and contraindications.

Compelling indications for the choice of antihypertensives.

  • Left ventricular hypertrophy: ACE-I or ARB, CCB preferably Amlodipine
  • Renal dysfunction: ACE-I or ARB; Caution-if eGFR <15min/ml without renal replacement therapy
  • Microalbuminuria: ACE-I or ARB
  • Previous stroke: Any of the first-line drugs, especially ACE-I
  • Coronary artery disease (Angina/Myocardial infarction): ACE-I or ARB, Beta-blocker, CCB.
  • Heart failure: ACE-I or ARB, Cardio-selective B-Blockers- bisoprolol, metoprolol, carvedilol; Loop diuretics, Spironolactone in advanced heart failure
  • Peripheral artery disease: CCB, ACE-I or ARB
  • Diabetes mellitus: ACE-I or ARB
  • Atrial fibrillation: ARB or ACE-I or

Compelling Contraindications

  • Gout: Thiazide diuretics
  • Beta-blockers: Asthma, 2 and 3 AV block
  • Heart failure: CCB
  • Bilateral renal artery stenosis and hyperkalaemia: ACE-I or ARB

Supportive measures

  • Patient/caregiver education

Notable adverse drug reactions, caution and contraindications

Angiotensin converting enzyme inhibitors, angiotensin receptor blockers:

  • angioedema;
  • dry cough with ACEIS.

Alpha methyldopa, thiazides and potentially other anti-hypertensive drugs may cause erectile dysfunction.

Alpha methyl dopa may cause postural hypotension.

SLE-like syndrome: hydralazine.

Do not use beta blockers in asthmatics and heart failure

Prevention

  • Weight reduction
  • Exercise moderately and regularly
  • Public education
  • Individual and Population based approaches
  • Advocacy for the positive lifestyle change
  • Target blood pressure: BP<140/90 mmHg for general population, BP < 130/80 mmHg for patients with diabetes or end stage renal
    disease

Hypertension in pregnancy

  • ACEI and ARB are terratogenic, contraindicated in pregnancy & to be used with caution in women in reproductive age group.
  • Alpha methyl dopa, hydralazine, calcium channel blockers are safe in pregnancy.
  • Diuretics are relatively safe.

Referral Criteria

Refer the following categories of hypertensive patients to an
appropriate specialist:

  • Those not achieving the target blood pressure (BP) level after several months of treatment
  • Those on three or more anti-hypertensive drugs, yet have poor BP control
  • Those with worsening of BP over a few weeks or months
  • Those with plasma creatinine levels above the upper limit of normal
  • Those with diabetes mellitus
  • Those with multiple risk factors (diabetes, dyslipidaemia, obesity,
    family history of heart disease)
  • Those not on diuretics but have persistently low potassium on
    repeated blood tests
  • All children, young adults and pregnant women with elevated BP

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