Hypertension

Hypertension is the term used to describe high blood pressure. 

The NICE guidelines on hypertension (updated 2022) suggest a diagnosis of hypertension with a blood pressure above 140/90 in the clinical setting, confirmed with ambulatory or home readings above 135/85. 

Causes of Hypertension 

Essential hypertension accounts for 90% of hypertension. This is also known as primary hypertension. It means a high blood pressure has developed on its own and does not have a secondary cause. 

Secondary causes of hypertension can be remembered with the “ROPED” mnemonic:

• R – Renal disease
• O – Obesity
• P – Pregnancy-induced hypertension or pre-eclampsia
• E – Endocrine
• D – Drugs (e.g., alcohol, steroids, NSAIDs, oestrogen and liquorice)

Renal disease is the most common cause of secondary hypertension. When the blood pressure is very high or does not respond to treatment, consider renal artery stenosis. Renal artery stenosis can be diagnosed with duplex ultrasound or an MR or CT angiogram.

Most endocrine conditions can cause hypertension. Hyperaldosteronism (Conn’s syndrome) is an important cause and may be present in 5-10% of patients with hypertension.

Specialist investigations should be considered in patients with a potential secondary cause for their hypertension or aged under 40 years.

Complications

High blood pressure increases the risk of:

• Ischaemic heart disease (angina and acute coronary syndrome)
• Cerebrovascular accident (stroke or intracranial haemorrhage)
• Vascular disease (peripheral arterial disease, aortic dissection and aortic aneurysms)
• Hypertensive retinopathy
• Hypertensive nephropathy
• Vascular dementia
• Left ventricular hypertrophy
• Heart failure

Patients with hypertension may develop left ventricular hypertrophy. The left ventricle is straining to pump blood against increased resistance in the arterial system, so the muscle becomes thicker. On examination, there may be a sustained and forceful apex beat. It can be seen on an ECG using voltage criteria and is best diagnosed with an echocardiogram.

Diagnosis

NICE recommend measuring blood pressure every 5 years to screen for hypertension. It should be measured more often in borderline cases and every year in patients with type 2 diabetes.

Patients with a clinic blood pressure between 140/90 mmHg and 180/120 mmHg should have 24-hour ambulatory blood pressure or home readings to confirm the diagnosis. Having blood pressure taken by a doctor or nurse often results in a higher reading. This is commonly called “white coat syndrome”. The white coat effect involves more than a 20/10 mmHg difference in blood pressure between clinic and ambulatory or home readings. 

NICE recommend measuring blood pressure in both arms, and if the difference is more than 15 mmHg, using the reading from the arm with the higher pressure.

Stages

End Organ Damage 

NICE recommend all patients with a new diagnosis should have:

• Urine albumin:creatinine ratio for proteinuria and dipstick for microscopic haematuria to assess for kidney damage 
• Bloods for HbA1c, renal function and lipids
• Fundus examination for hypertensive retinopathy
• ECG for cardiac abnormalities, including left ventricular hypertrophy

NICE recommend calculating the QRISK score, which estimates the percentage risk that a patient will have a stroke or myocardial infarction in the next 10 years. When the result is above 10%, they should be offered a statin, initially atorvastatin 20mg at night.

Management

Lifestyle advice includes a healthy diet, stopping smoking, reducing alcohol, caffeine and salt intake and taking regular exercise.

Medications used in management are:

• A – ACE inhibitor (e.g., ramipril)
• B – Beta blocker (e.g., bisoprolol)
• C – Calcium channel blocker (e.g., amlodipine)
• D – Thiazide-like diuretic (e.g., indapamide)
• ARB – Angiotensin II receptor blocker (e.g., candesartan)

Angiotensin receptor blockers (ARBs) are recommended by NICE instead of ACE inhibitors in patients of Black African or African-Caribbean family origin. In the steps below, you can replace A with ARB for these patients.

ARBs are an alternative if the person does not tolerate ACE inhibitors (commonly due to a dry cough). ACE inhibitors and ARBs are not used together.

Thiazide-like diuretics are used as an alternative if the patient does not tolerate calcium channel blockers (commonly due to ankle oedema).

The NICE recommendations vary for patients under 55 or over 55, type 2 diabetics and patients of Black African or African-Caribbean family origin: 

• Step 1: Aged under 55 or type 2 diabetic of any age or family origin, use A. Aged over 55 or Black African use C.
• Step 2: A + C. Alternatively, A + D or C + D.
• Step 3: A + C + D
• Step 4: A + C + D + fourth agent (see below)

Step 4 depends on the serum potassium level:

• Less than or equal to 4.5 mmol/L consider a potassium-sparing diuretic, such as spironolactone
• More than 4.5 mmol/L consider an alpha blocker (e.g., doxazosin) or a beta blocker (e.g., atenolol)

Remember to check adherence. Specialist management is indicated for uncontrolled blood pressure at step 4.

Potassium Balance

Spironolactone is a potassium-sparing diuretic. It works by blocking the action of aldosterone in the kidneys, resulting in sodium excretion and potassium reabsorption. It can be helpful when thiazide diuretics are causing hypokalaemia. 

Using spironolactone increases the risk of hyperkalaemia. ACE inhibitors can also cause hyperkalaemia. Thiazide-like diuretics can also cause electrolyte disturbances. Therefore, it is essential to monitor U+Es regularly with these drugs.

Treatment Targets

Hypertensive Emergency

Accelerated hypertension, also called malignant hypertension, refers to extremely high blood pressure, above 180/120, with retinal haemorrhages or papilloedema.

The NICE guidelines recommend a same-day referral for patients with accelerated hypertension. Therefore, patients with a blood pressure above 180/120 require a fundoscopy examination to look for these key findings. Additional complications also warrant same-day assessment, such as confusion, heart failure, suspected acute coronary syndrome or acute kidney injury. 

Patients admitted with a hypertensive emergency are assessed for secondary causes and end-organ damage. Their blood pressure is closely monitored while medications bring it under control. 

Intravenous options in a hypertensive emergency (guided by an experienced specialist) include:

• Sodium nitroprusside 
• Labetalol
• Glyceryl trinitrate
• Nicardipine

How rapidly the blood pressure should be reduced depends on the individual patient. Elderly frail patients may be at risk of ischaemic if the blood pressure is reduced too quickly, as the higher pressure may be required to force blood through narrowed vessels.

Last updated March 2023