The prevalence of hypertension in adults of 16 years or older is 31.5% in men and 29% in women. In general practice the diagnosis and care of hypertensive patients is determined largely by NICE 2011 hypertension guidance, with GPs taking into account individual patient factors. This NICE guidance changed the methods of diagnosing hypertension in primary care and established diagnosis through clinic blood pressure readings (CBP), followed by either ambulatory 12- hour BP monitoring (ABPM) or home blood pressure monitoring (HBPM). This excludes patients with white coat hypertension from diagnosis and treatment and prevents unnecessary treatment for anxious patients, who are normotensive outside of the GP clinic. A recent article in the British Journal of General Practice (BJGP) noted that nurses and healthcare assistants are more likely to monitor blood pressure (BP) nowadays, than GPs. Also, nurses altered BP therapy in 26% of practices. However, 1 in 10 practices were not using ABPM or HBPM in the diagnosis of hypertension. There are special hypertensive populations to consider in general practice. These are hypertensive women wanting to conceive, women in pregnancy, and the elderly who are over 80 years old. These groups are explored in more detail later. In addition, GPs look after populations with multimorbidity and polypharmacy. This article refreshes knowledge of hypertension at all population life stages.
A Cochrane Review of treatment of hypertension in 2009 concluded that in a primary prevention population with moderate and severe hypertension (CBP ≥ 160/100mmHg), treatment caused an absolute risk reduction (ARR) of total cardiovascular events of about 5% over 5 years. This means that about 20 patients need to be treated for 5 years to prevent one adverse cardiovascular event. The team concluded that secondary prevention of stroke or myocardial infarction over the age of 55 years old had moderate evidence of treatment benefit if the patient’s CBP ≥ 140/90mmHg. The review pointed out that 40% of patients did not reach their target BP despite therapy. A further Cochrane Review of evidence in 2012 looking at the benefits and harms of 4-5 years of drug treatment in mild hypertension, i.e. systolic 140-159mmHg and/ or diastolics of between 90-99mmHg, did not show a significant improvement in total mortality or events of coronary heart disease, stroke or total cardiovascular events and had a 9% drug discontinuation rate. This is reflected in the advice from NICE in which BP is divided into stages in order to recommend therapy where there is evidence of benefit, and is discussed below. GPs are recommended to subdivide mild stage 1 hypertension (CBP ≥ 140-160/ 90-100mmHg) into requiring antihypertensive medication and not requiring antihypertensive drug therapy. Furthermore, GPs are recommended to treat hypertensives with BP stages 2 and severe (CBP≥ 160/100mmHg and ABPM/HBPM daytime average ≥ 150/95mmHg).
Population for ‘usual’ hypertensive care
This section relates to patients under the age of 80 years old who are not embarking on, or in, pregnancy. There are 3 causes of hypertensive patients in general practice:
- Patients with white coat hypertension, largely excluded by ABPM or HBPM
- Patients with primary hypertension
- Patients with secondary hypertension.
In order to distinguish these, GPs measure the CBP with an appropriate size cuff. Many obese patients will have their CBP raised by small BP cuffs. The BP bladder on the cuff should cover 80% of the arm and Table 1 guides BP cuff size by arm circumference. For GPs, remembering that an arm circumference over 33cm requires a large cuff size is most useful.
BP should be estimated manually in patients with atrial fibrillation and electronic machines should be checked against a standard annually to maintain accuracy.
Clinic BP is taken with the patient sitting and two readings are taken a minute or two apart. BP is also checked in the other arm to exclude arterial stenosis or coarctation of the aorta. The lowest reading is selected. Although there is no ‘no risk’ BP, as risk sits on an escalator, expert bodies have created guidelines to define higher risk populations. Hypertension for most people is defined as CBP≥ 140/90mmHg followed by a 12- hour waking ABPM, or if not convenient, a HBPM for 7 days. The British Hypertension Society has a free download HBPM diary for patients to complete which is convenient to print off in clinics. To calculate HBPM the patient takes their BP at home twice and twice a day. The first day of readings are discarded and the lowest of each of the morning and evening readings is taken and BP is averaged from the remaining 12 readings. Target ABPM or HBPM for diagnosis of hypertension is an average ≥ 135/85mmHg; note that this is lower than the CBP reading.
There are two difficult scenarios; one is patients with arm lymphoedema and the other is patients with orthostatic (postural) hypotension but with coexisting hypertension.
Taking the BP of a patient with lymphoedema of the arm is controversial. For many years, patients have been trained by specialists to ask GPs not to take BP on the lymphoedema affected arms, and this is particularly problematic in patients with bilateral arm lymphoedema, usually after bilateral lymphatic surgery for breast cancer. This topic has resurfaced in the literature with varying views. It is thought by some authorities that a manual BP taken transiently and with a cuff compression just above systolic is unlikely to cause harm, but it is difficult to do this when a patient has been specifically advised to avoid it. There is no information about electronic BP machine use, in which there may be higher and more sustained pressures applied by the cuff and these are best avoided at present until evidence is clearer.
Patients with orthostatic hypotension may be asymptomatic or may present with postural dizziness. This is defined as a 20mmHg systolic drop or a 10mmHg diastolic drop when BP is taken standing for one minute (though some definitions suggest subtyping and standing the patient for 3 minutes) compared to the supine or sitting BP reading. It is very common in people with autonomic neuropathy, perhaps as a complication of Parkinson’s disease, dementia, oldage, diabetes and a number of medications. Some patients are symptomatic and dizzy and others have no symptoms. Preventing orthostatic hypotension may prevent syncope, improve the patient’s functioning and dizziness so judgements on treatment of these patients, if they also have hypertension as a comorbidity, is difficult. Lifestyle measures to prevent dehydration and waiting 30 seconds before standing from lying, i.e. sitting on the side of the bed, helps. NICE recommends subsequent measurement of BP in these patients standing. Starting antihypertensives, or deciding to stop antihypertensives, in patients with orthostatic hypotension can be difficult and GPs may request specialist opinions to help with individualised decision making.
After taking a history, usually focussed on family history and lifestyle factors, examination and investigation are performed to look for both sequelae of hypertension and uncommon causes of secondary hypertension. NICE guidance suggests that anyone under the age of 40 years old is screened in specialist clinics for secondary causes. Secondary causes might be metabolic, endocrine or renal. Table 2 suggests possible examination findings and recommended investigations.
A patient with white coat hypertension will need to continue to use HBPM/ABPM to assess BP control intermittently as they will otherwise be misdiagnosed as hypertensive in the GP clinic. Hypertension, once diagnosed and investigated, is treated by lifestyle measures and often by long- term medications. The aim of therapy is to optimise individual health through lifestyle, stop smoking interventions, stop excess alcohol and maintain an active weight with regular exercise. Lowering BP reduces risks of stroke, cardiovascular disease including heart failure and secondary renal disease. Antihypertensive medications are used to bring CBP down to <140/90mmHg if required. In considering medication hypertensive patients are sub-grouped by future risk into:
- Primary prevention of hypertensive sequelae in people at ‘low’ risk of future CVD
- Primary prevention of hypertensive sequelae in people at ‘high’ risk of future CVD In England QRISK2 is the recommended risk scoring tool for 10-year coronary risk assessment (CRA)
- Secondary prevention in people with pre-existing CVD
- A subgroup of patients under specialist care with unusual conditions in whom BP reduction to stated specialist recommended BP targets is required. This group is not discussed in this article as targets are individualised by specialists for their patients.
Hypertension levels are categorised as:
Stage 1 hypertension:
- CBP ≥ 140/90mmHg and ABPM/HBPM average≥ 135/85mmHg but CBP <160/100mmHg
- 1a: NICE 2011 guideline suggests life-style measures only in patients at low risk of CVD but hypertensive. These people have no target organ damage, no CVD, no renal disease and a CRA of <20% over 10 years. Medication has not been shown to improve health outcomes
- 1b: This group have the same lower BP figures, but have existing evidence of hypertensive disease or CVD or renal disease or a CRA of >20% over 10 years. This group are recommended to have antihypertensive drug treatment as well as life-style measures.
Stage 2 hypertension:
- CBP ≥ 160/100mmHg and ABPM or HBPM daytime average is ≥ 150/95mmHg but CBP <180/110mmHg. This group are recommended to have antihypertensive drug treatment as well as lifestyle measures.
- CBP is ≥180 mmHg and/or CBP diastolic BP is ≥110mmHg but not for same day referral as no retinal or renal signs and asymptomatic (see below). This group are recommended to have antihypertensive drug treatment as well as lifestyle measures.
Patients to refer that day
- Accelerated (or malignant) hypertension: This occurs in 2-3 people per 100,000 per year. CBP ≥180/110mmHg: levels as the NICE classification of severe hypertension but with signs of retinal haemorrhage or papilloedema: refer that day. 50-60% of these people have symptoms of accelerated hypertension, such as headache and visual disturbance and may also have haematuria and/or proteinuria.
- Suspected phaeochromocytoma: These patients have labile or postural hypotension, headache, palpitations, pallor and diaphoresis (sweating).
Recommended drug treatment varies with the age and ethnicity of the patient. Control of BP is monitored by CBP once the diagnosis of hypertension has been made. This article discusses first line therapy of hypertension.
First line antihypertensives for people <55 years old and not of Black Afro- Caribbean ethnicity
This group are recommended to start with an angiotensin converting enzyme (ACE-I) or angiotensin receptor blocker (ARB). Complications of ACE-I and ARBs, apart from hypotension, are hyperkalaemia and/or renal impairment or acute kidney injury (AKI). Therefore, before starting an ACEI or ARB the patient’s eGFR should be checked and again 7-14 days afterwards, as well as 7-14 days after each dose increase. A pre-therapy high potassium or low eGFR excludes general practice ACEI or ARB use. Patients with low eGFRs at outset of monitoring should be referred to a specialist clinic for renal assessment. On starting ACE-I or ARB there may be an ‘acceptable’ reduction in eGFR. A reduction in eGFR of ≥15%, or a rise in serum creatine ≥20%, would lead GPs to stop the ACE-I and refer to a nephrology clinic. There are a group of patients with protein-losing nephropathies but with good renal perfusion who benefit from ACEI and ARBs, e.g. diabetes or nephrotic syndrome. Some patients taking ACE-Is have an increased cough reflex causing troublesome dry cough in 5-35% of patients, sometimes months after therapy commencement, and this can take about 1-4 weeks to resolve on stopping the ACE-I, sometimes longer. A more unusual side-effect is angio-oedema, affecting less than 1% of ACE-I taking patients. Patients with cough or angio-oedema benefit from changing to an ARB. However, renal complications of ACE-Is will also occur with ARBs. Starting ACE-I and ARBs in patients on diuretics requires specialised consideration as hypovolaemic patients may develop AKI from the drop in their BP.
Once the BP is stable, annual bloods are required. If a patient develops an acute illness associated with possible renal hypoperfusion, like diarrhoea or vomiting induced dehydration, the GP should temporarily stop the ACE-I or ARB and urgently check U&Es and eGFR, unless admitting the patient.
First line antihypertensives for people ≥ 55 years old and all patients of Black Afro-Caribbean ethnicity
Thiazide-like diuretics, such as indapamide or chlortalidone, or a calcium channel blocker, like amlodipine, are recommended and all are dosed as once a day. Diuretics require base-line U+Es and eGFR assessment, and a repeat one month after starting to exclude new onset dehydration or hypokalaemia. After that, unless the patient is unwell, annual monitoring is required. Amlodipine benefits from not requiring blood tests as it does not disturb water and electrolyte balance. It has an incidence, through skin vasodilation, of flushing, headache and leg oedema.
Second line therapy
Failure to lower BP successfully results in patients additionally using second-line drugs. For someone <50 years old and not Afro-Caribbean, and who is on maximum dose ACEI or ARB, this would be adding in amlodipine or indapamide. Adding in a thiazide-like diuretic requires electrolyte and renal function monitoring after commencement.
For the Afro-Caribbean patient or those hypertensives ≥55 years old who are already on maximum recommended or tolerated doses of either amlodipine or a thiazide like diuretic, an ACE-I or ARB is added. For the Afro-Caribbean hypertensive patient, NICE recommends an ARB in preference to an ACE-I due to an increase in side-effects on an ACE-I in this ethnic group. Electrolyte and renal function should be checked at baseline and 7-14 days after starting and each dose increase. ARBs and ACE-I are not recommended together due to the risk of hyperkalaemia and subsequent cardiac dysrhythmia.
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Mennatella Gharib MRes intercalation student, year 4/5 University of Liverpool School of Medicine.
Dr Jane Wilcock Year assessment lead and clinical community tutor, University of Liverpool School of Medicine, Part-time GP Silverdale Medical Practice, Pendlebury Health Centre