Resistant hypertension: when blood pressure stays high despite treatment

High blood pressure, or hypertension, is usually defined by the NHS as a reading of 140/90 or higher when checked by a healthcare professional, or 135/85 or higher when checked at home. NICE guideline NG136 sets out a stepwise approach to treatment, starting with one medicine and adding others if blood pressure stays above target.

Resistant hypertension is the label NICE gives to the point at which that approach has been pushed as far as step 3. If hypertension is not controlled in adults taking the optimal tolerated doses of an ACE inhibitor or an angiotensin receptor blocker (ARB), a calcium-channel blocker and a thiazide-like diuretic, they are regarded as having resistant hypertension.

The wording matters. It does not mean that nothing will work, and it does not mean the person has done anything wrong. It is a signal to double-check the basics and then think about additional medicine or a search for an underlying cause.

NICE sets out three things to do before considering further treatment for resistant hypertension: confirm the raised clinic readings using ambulatory or home blood pressure recordings, assess for postural hypotension, and discuss adherence. Each of these can change the picture.

NICE CKS describes white-coat hypertension as blood pressure that is unusually raised during consultations but normal in other situations, which is one reason ambulatory or home monitoring is used to confirm readings. For ambulatory monitoring, NICE says at least 2 measurements per hour should be taken during waking hours. NICE also asks that blood pressure is measured with a properly validated device, with the person seated and relaxed, and with the right size of cuff.

NICE asks clinicians to discuss with the person whether they are taking their medicine as prescribed and to support adherence. This is a routine part of every step, not an accusation. Telling the GP or pharmacist honestly what you actually take, and any side effects that make it hard to keep going, is the most useful thing you can do.

The NHS lists age, close relatives with high blood pressure, ethnic background, an unhealthy diet high in salt, being overweight, smoking, heavy drinking and long-term stress as factors that increase the chance of high blood pressure. Any of these can make it harder to bring pressure down.

NICE CKS notes that around 10 per cent of hypertension is secondary, meaning it has a known cause such as a kidney, hormone or blood vessel disorder or the use of certain drugs. This is why the guideline advises specialist evaluation for secondary causes in some situations, and NICE says to consider this for adults under 40 with hypertension. If blood pressure is hard to control, looking again for such a cause is a standard step.

Everyday habits can also work against treatment. NICE advises discouraging excessive consumption of coffee and other caffeine-rich products, encouraging reduced alcohol intake in people who drink excessively and keeping dietary sodium low. A pharmacist or GP can review everything you take and drink.

NICE describes the steps as follows. Step 1 is an ACE inhibitor or ARB, or a calcium-channel blocker depending on age, diabetes and family origin. Step 2 adds a second class and step 3 combines an ACE inhibitor or ARB with a calcium-channel blocker and a thiazide-like diuretic. Step 4 is for resistant hypertension.

For step 4, NICE says to consider further diuretic therapy with low-dose spironolactone for adults whose blood potassium level is 4.5 mmol/l or less, using particular caution in people with reduced kidney function because of the risk of high potassium (hyperkalaemia). If blood potassium is above 4.5 mmol/l, NICE says to consider an alpha-blocker or beta-blocker instead.

Blood sodium, potassium and kidney function are monitored within a month of starting step 4 treatment and then as needed. If blood pressure remains uncontrolled on the optimal tolerated doses of four drugs, NICE says to seek specialist advice, which in the NHS usually means a hypertension clinic or a hospital physician with an interest in blood pressure.

NICE CKS gives the target clinic blood pressure as below 140/90 mmHg for people under 80 and below 150/90 mmHg for people aged 80 or over. Home or ambulatory targets are 135/85 and 145/85 mmHg respectively. For people with postural hypotension, the target is based on standing blood pressure, and for frailty or multiple conditions clinical judgement is used.

NICE asks for an annual review of care for adults with hypertension, to monitor blood pressure, support the person and discuss lifestyle, symptoms and medication. Many people with resistant hypertension are seen more often than that while the regimen is being adjusted.

The NHS recommends a healthy, balanced diet, regular exercise of at least 150 minutes a week, losing weight if overweight, not eating too much salt, drinking no more than 14 units of alcohol a week, avoiding too much caffeine and not smoking. These steps reduce blood pressure and the strain on the heart and kidneys, and they continue to help even when several medicines are needed.

NICE adds that calcium, magnesium or potassium supplements should not be used as a way of reducing blood pressure, and that salt substitutes containing potassium chloride should not be used by older people, people with diabetes, pregnant women, people with kidney disease or people taking some antihypertensive drugs such as ACE inhibitors and ARBs.

The reason for persevering is that, as the NHS says, lowering blood pressure even a small amount can help reduce the risk of heart disease, heart attacks, strokes, heart failure, kidney disease and vascular dementia.

The NHS advises calling 999 for sudden chest pain or discomfort that does not go away, pain spreading to the arm, neck, jaw, stomach or back, or chest pain with sweating, sickness, light-headedness or breathlessness, as this could be a heart attack. It says to get help from NHS 111 if you often have headaches or blurred vision, or chest pain that comes and goes.

NICE CKS says that a clinic reading of 180/120 mmHg or higher together with signs of retinal haemorrhage or swelling of the optic nerve, or with life-threatening symptoms such as new confusion, chest pain, signs of heart failure or acute kidney injury, calls for same-day specialist assessment.

On the NHS, resistant hypertension is first managed by the GP or practice team, with referral to a hypertension specialist or renal or endocrine clinic if needed. Tests for secondary causes are arranged in the same pathway.

Some people choose to see a private cardiologist or hypertension specialist to shorten the wait or get a second opinion. The diagnostic tests and the medicines are the same, and the main differences are speed of access and choice of clinician. Bring a record of home readings and a list of your medicines to any appointment.