The SA Journal Diabetes & Vascular Disease Vol 11 No 4 (November 2014)

VOLUME 11 NUMBER 4 • NOVEMBER 2014

143

SA JOURNAL OF DIABETES & VASCULAR DISEASE

REVIEW

as are seen in hypertensive emergencies. Ideally, all patients with

hypertensive urgency should be treated in hospital.

Commence treatment with two oral agents and aim to lower the

diastolic BP to 100 mmHg slowly over 48 to 72 hours. This BP lowering

can be achieved with the use of: (1) long-acting CCBs; (2) ACEI, initially

used in very low doses, but avoid if there is severe hyponatraemia

(serum Na < 130 mmol/l indicates hyper-reninaemia and BP may fall

dramatically with ACEI); (3)

- blockers; and (4) diuretics.

• Hypertensive emergency

A hypertensive emergency is severe, often acute elevation of BP

associated with acute and ongoing organ damage to the kidneys,

brain, heart, eyes (grade 3 or 4 retinopathy) or vascular system.

These patients need rapid (within minutes to a few hours) lowering

of BP to safe levels. Hospitalisation is ideally in an intensive care unit

(ICU) with experienced staff and modern facilities for monitoring.

If an ICU is unavailable, the patient may be closely monitored and

treated in the ward.

Intravenous antihypertensive therapy, tailored to the specific

type of emergency, has become the standard of care. Labetalol,

nitroprusside or nitroglycerin are the preferred intravenous agents.

Overzealous lowering of BP may result in stroke. A 25% reduction

in BP is recommended in the first 24 hours. Oral therapy is instituted

once the BP is more stable. Although most adult patients with a

hypertensive emergency will have BP > 220/130 mmHg, it may

also be seen at modest BP elevations; for example, in a previously

normotensive woman during pregnancy (eclampsia) or in the

setting of acute glomerulonephritis, especially in children.

Severe HTN associated with ischaemic stroke and intracerebral

haemorrhageshouldbemanagedaccordingtotherecommendations

of the Neurological Association of South Africa.

Great caution

should be exercised in lowering BP after an ischaemic stroke due to

the risk of extending the ischaemic penumbra.

Resistant hypertension

HTN that remains > 140/90 mmHg despite the use of three

antihypertensive drugs in a rational combination at full doses and

including a diuretic (hydrochlorothiazide 25 mg or indapamide

2.5 mg) is known as resistant HTN. Common causes of resistant

HTN are listed in Table 8.

The therapeutic plan must include measures to ensure adherence

to therapy and lifestyle changes. Unsuspected causes of secondary

HTN are less common, but need to be considered based on history,

examination and special investigations. It is essential to exclude

pseudo-resistance by performing SBPM or 24-hour ABPM. Referral

to a specialist is often indicated for a patient with resistant HTN.

Once the issues relating to lifestyle, adherence to therapy, white

coating, etc. outlined in Table 7 have been satisfactorily managed,

then consideration should be given to the addition of the fourth-

and fifth-line drug. Currently spironolactone (25–50 mg only) with

careful monitoring of serum potassium, beta-blockers and/or long-

acting doxazasin is recommended.

27,28

Other choices include direct-

acting vasodilators (hydralazine, minoxidil), or centrally acting drugs

(methyldopa, moxonidine, reserpine).

Initial studies of renal denervation in patients with resistant HTN

showed very promising results.

29,30

The recent publication of the

Simplicity 3 study showing no significant effect on BP compared

to sham procedure, the place of renal denervation in the treatment

of resistant HTN remains to be established and is not supported by

this guideline.

Special considerations for hypertension in certain

populations

Blacks and Asians

Blacks are more prone to complications of stroke, heart failure and

renal failure, while the incidence of coronary heart disease, although

increasing in frequency, is less common compared with that in whites

and Asians.

The prevalence of diabetes mellitus and the metabolic

syndrome is higher in Asians compared to other racial groups.

Compared to whites, blacks respond poorly to ACEI and

-blockers as monotherapy, but this difference disappears once

these drugs are combined with diuretics. Overall, CCBs show the

most consistent response in blacks compared to other classes of

drugs used as monotherapy.

23,34

However there is a higher incidence

of angioedema in blacks treated with an ACEI.

Hypertension in children and adolescents

36,37

HTN in children is an important issue beyond the scope of this

guideline. In adolescents, the HTN is increasingly linked to obesity

and affects up to 10% of people between the ages of 15 and

Table 8.

Causes of resistant hypertension in South Africa

Non-adherence

to therapy

• Instructions not understood

• Side effects

• Cost of medication and/or cost of attending at

healthcare centre

• Lack of consistent and continuous primary care

• Inconvenient and chaotic dosing schedules

• Organic brain syndrome (e.g. memory deficit)

Volume overload • Excess salt intake

• Inadequate diuretic therapy

• Progressive renal damage (nephrosclerosis)

Associated

conditions

• Smoking

• Increasing obesity

• Sleep apnoea

• Insulin resistance/hyperinsulinaemia

• Ethanol intake of more than 30 g (three standard

drinks) daily

• Anxiety-induced hyperventilation or panic attacks

• Chronic pain

• Intense vasoconstriction (Raynaud’s

phenomenon), arteritis

Identifiable

causes of

hypertension

• Chronic kidney disease

• Renovascular disease

• Primary aldosteronism

• Coarctation

• Cushing’s syndrome

• Phaeochromocytoma

Pseudoresistance • ‘White coat hypertension’ or office elevations

• Pseudohypertension in older patients

• Use of regular cuff in obese patients

Drug-related

causes

• Doses too low

• Wrong type of diuretic

• Inappropriate combinations

• Rapid inactivation (e.g. hydralazine)

Drug actions

and interactions

• Non-steroidal anti-inflammatory drugs (NSAIDs)

• Sympathomimetics: nasal decongestants, appetite

suppressants

• Cocaine, Tik and other recreational drugs

• Oral contraceptives

• Adrenal steroids

• Liquorice (as may be found in chewing tobacco)

• Cyclosporine, tacrolimus, erythropoietin

• Antidepressants (monoamine oxidase inhibitors,

tricyclics)