Dr Alan Begg shares some key points for diagnosing and managing hypertension in primary care

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Read this article to learn more about:

  • taking accurate blood pressure measurements and making a diagnosis of hypertension
  • controlling blood pressure in patients with hypertension.

Raised blood pressure (BP) is a major modifiable risk factor for stroke, myocardial infarction, heart failure, chronic kidney disease, cognitive decline, and premature death. There is good evidence from randomised trials of the effectiveness of BP lowering therapy in reducing associated risks. Hypertension represents a significant cost so it is important that we adopt a standardised and structured approach to all aspects of diagnosis and management.

1 Ensure BP readings are reliable

Blood pressure should be measured in a relaxed, standardised fashion, and at a comfortable temperature.1,2

Determining BP is one of the most frequently performed measurements in clinical practice, yet natural variation can potentially make it unreliable. Blood pressure should be measured in everyone over the age of 40 every 5 years, certainly up to the age of 80 years.1 All healthcare professionals taking BP measurements need adequate initial training and periodic review of their performance.2 Practitioners should aim to reduce measurement errors as much as possible.

The pulse rate and rhythm should be recorded before BP is measured.

Using a manual BP monitor, the patient should be seated for 5 minutes with the arm supported at heart level. An appropriate cuff that encircles 80% of the arm should be used, and there should be no restriction from tight clothing.

The systolic blood pressure (SBP) should be estimated by recording when the brachial pulse disappears followed by reinflating the cuff to 30 mmHg above this level. The rate of deflation should be 2–3 mmHg per second and, auscultating the brachial artery with the stethoscope diaphragm, the SBP recorded when the pulse appears (Korotkoff sound phase 1); diastolic blood pressure (DBP) is recorded when the pulse disappears (Korotkoff sound phase 5). In pregnancy the Korotkoff sounds may persist and so phase 4 should be recorded instead. An electronic monitor will automatically record the BP but the preparation should be similar to when using a manual monitor.3

2 Check your equipment

Devices used to measure BP should be properly validated, maintained, and regularly calibrated according to the manufacturer's instructions.1,2

Mercury sphygmomanometers are in the process of being withdrawn from clinical use but remain the gold standard against which the accuracy of new BP monitors is judged. The detection of pressure oscillations in the cuff during deflation is the most common method used in semi-automatic and automatic devices. Aneroid devices require more regular maintenance and calibration to maintain their accuracy.1

Rhythm disturbances, especially atrial fibrillation, can affect BP measurement, particularly if using oscillometric techniques that depend on successive waveforms having a similar smooth profile.1 NICE recommends that if the pulse is irregular, the BP should be measured using direct auscultation over the brachial artery.2 If the heart rate is below 50 beats/min, even if the rhythm is regular, a semi-automatic device may be unable to reduce the deflation rate sufficiently, leading to an underestimation of SBP and overestimation of DBP.1

3 Confirm the diagnosis

A diagnosis of hypertension should be confirmed using ambulatory blood pressure monitoring (ABPM) if BP is ≥140/90 mmHg,2 see Box 1, below.

Measure BP in both arms. If the difference in readings between the two arms is greater than 20 mmHg, take a second measurement. If the difference is confirmed, measure the BP in the arm with the higher reading.

If BP measured in the clinic is ≥140/90 mmHg, repeat the measurement and take a third reading if the second is substantially different from the first. Record the lower of the last two measurements as clinic BP.

Home blood pressure monitoring (HBPM) is a suitable alternative to ABPM.2

A diagnosis of hypertension is made on the average of at least 14 BP measurements taken during usual waking hours, with at least two measurements taken per hour. If using HBPM, the person should take two readings each time 1 minute apart while seated, and record BP twice daily in the morning and evening. The recordings should continue for at least 4 days but ideally for 7 days. The first-day measurements are discarded and the average of all the remaining measurements are used to confirm a diagnosis.2

Investigations should be carried out to determine evidence of target organ damage and evidence of possible underlying cause:2

  • test for haematuria and estimate urinary albumin:creatinine ratio
  • measure plasma glucose, electrolytes, creatinine, estimated glomerular filtration rate (eGFR), serum total cholesterol, and high-density lipoprotein cholesterol
  • examine fundi for presence of hypertensive retinopathy
  • perform 12-lead ECG.

Box 1: Definitions of hypertension2

In NICE Clinical Guideline 127 the following definitions are used:

  • Stage 1 hypertension—clinic BP is 140/90 mmHg or higher and subsequent ABPM daytime average or HBPM average blood pressure is 135/85 mmHg or higher
  • Stage 2 hypertension—clinic blood pressure is 160/100 mmHg or higher and subsequent ABPM daytime average or HBPM average blood pressure is 150/95 mmHg or higher
  • Severe hypertension—clinic systolic blood pressure is 180 mmHg or higher or clinic diastolic blood pressure is 110 mmHg or higher.

4 Measure CVD risk

A formal estimation of cardiovascular disease (CVD) risk should be performed in those with hypertension.2

Blood pressure is an independent risk factor for CVD and as the BP increases so does the risk of a stroke, coronary heart disease, or heart failure. An absolute measurement of risk is usually performed using a risk tool such as QRISK® 2 or the ASSIGN score in Scotland. Absolute risk estimation is dependent on age and gender so that younger people and especially women may escape treatment despite having high levels of modifiable risk factors. The JBS3 risk calculator estimates both the 10-year risk of CVD and the risk of CVD over a lifetime.4

A measurement of CVD risk should be taken in those individuals with raised BP and used to discuss prognosis and the need for management of other risk factors, including lifestyle and raised lipid levels.

5 Advise lifestyle change

Lifestyle modification is important to help reduce CVD risk and will help reduce BP.

Making changes to lifestyle can help reduce BP and may in certain cases avoid the need for drug therapy, or reduce the number of drugs required to control BP in those on therapy.

Measures to lower BP include:4

  • reducing weight (use a multidisciplinary approach if the patient is obese)
  • reducing salt intake to <6 g/day
  • limiting alcohol consumption to <21 units per week for men and <14 units per week for women (although recent proposed government guidance would suggest that we should recommend even lower levels5)
  • increasing physical activity—an overall increase of sustained activity and reduction in sedentary behaviour is required
  • increasing fruit and vegetable consumption to five portions per day
  • reducing total fat and saturated fat intake—saturated fat should be <10% of total fat intake.

Additional measures to reduce CVD risk include:4

  • smoking cessation—with support from professional and smoking cessation services
  • replacing saturated fats with monounsaturated fats
  • increasing oily fish consumption—at least two servings of fish per week.

A diet with reduced refined carbohydrates (such as white bread, processed cereals, sugar sweetened beverages, and calorie rich snacks) is associated with the lowest risk of CVD.

6 Use the ACD algorithm

The NICE/BHS Treatment of hypertension algorithm6 should be used to sequence antihypertensive drug therapy choice (see Figure 1, below).

Drug therapy should be offered to those aged <80 years with stage 1 hypertension and any of the following:2

  • target organ damage
  • established CVD
  • renal disease
  • diabetes
  • a 10-year CVD risk of ≥20%.

People of any age with stage 2 hypertension should be offered drug treatment. Ideally, drugs that are taken only once daily should be prescribed, and if appropriate, nonproprietary ones to minimise cost.2

Hypertension treatment should follow the four steps of the treatment algorithm in Figure 1, see below.

A low-cost angiotensin II receptor blocker (ARB) may be used if an angiotensin-converting enzyme (ACE) inhibitor is not tolerated, for example, because of a cough.

Beta blockers are not a preferred initial therapy but may be considered in: younger people who do not tolerate an ACE inhibitor or an ARB; women of child-bearing potential; or if there is evidence of increased sympathetic drive.2

Figure 1: The NICE/BHS treatment of hypertension algorithm6
The NICE/BHS treatment of hypertension algorithm

7 Resistant hypertension

Classify clinic BP that remains higher than 140/90 mmHg after step 3 treatment as 'resistant hypertension' (see Figure 1, above).6

If the patient's BP remains >140/90 mmHg after treatment with optimal or best tolerated doses of either an ACE inhibitor or ARB in combination with a calcium channel blocker (CCB) and a diuretic, consider adding a fourth antihypertensive drug and/or seeking expert medical advice.

Consider low-dose spironolactone 25 mg daily if blood potassium level is ≤4.5 mmol/l, but use with caution if the eGFR is reduced because of increased risk of hyperkalaemia. As spironolactone is not licensed for this indication, informed consent should be obtained and documented.2

NB spironolactone does not have marketing authorisation for this indication. The prescriber should follow relevant professional guidance, taking full responsibility for the decision. Informed consent should be obtained and documented. See the General Medical Council's Good practice in prescribing and managing medicines and devices for further information.7

When using further diuretic therapy at step 4 (see Figure 1, above), check creatinine and electrolytes within 1 month and repeat as required thereafter. If this further diuretic therapy is ineffective or contraindicated, consider an alpha or beta blocker.2

8 Monitoring and adherence to therapy

People with hypertension should be reviewed annually to monitor BP and discuss lifestyle and medication.

Clinic BP measurements should be used to monitor response to therapy and lifestyle modifications. Aim for a target of <140/90 mmHg in those aged <80 years and 150/90 mmHg in those aged ≥80 years (see Box 2, below).2

Either ABPM or HBPM can be used to monitor response to treatment including in those identified as having a 'white coat effect'—aim for a target during waking hours of <135/85 mmHg if <80 years and <145/85 mmHg if ≥80 years (see Box 2, below).2

Patient education can help improve adherence to treatment. Interventions can be used to overcome practical problems associated with non-adherence. Interventions may include:2

  • suggesting that patients record their medicine-taking as well as self monitoring
  • simplifying the dosing regimen
  • using a multi-compartment medicines system.

If BP remains uncontrolled with the optimal or maximum tolerated doses of four drugs, expert advice should be sought, as with any of the other indications for specialist referral given below:

  • indications requiring urgent treatment:4
    • accelerated hypertension (severe hypertension and grade III–IV retinopathy)
    • particularly severe hypertension (>220/120 mmHg)
    • impending complications, e.g. transient ischaemic attack, left ventricular failure
  • indications suggesting a possible underlying cause:4
    • any clue in history or examination of a secondary cause, such as hypokalaemia with increased or high normal plasma sodium (Conn's syndrome)
    • elevated serum creatinine
    • proteinuria or haematuria
    • sudden onset or worsening of hypertension
    • resistance to multidrug regimen (≥3 drugs)
    • young age (any hypertension <20 years; needing treatment <30 years)
  • indications suggesting therapeutic problems:4
    • multiple drug intolerance
    • multiple drug contraindications
    • persistent non-adherence or non-compliance.

Box 2: Monitoring treatment and blood pressure targets2

  • Use clinic BP measurements to monitor the response to antihypertensive treatment with lifestyle modifications or drugs
  • Aim for a target clinic BP below 140/90 mmHg in people aged under 80 years with treated hypertension
  • Aim for a target clinic BP below 150/90 mmHg in people aged 80 years and over, with treated hypertension
  • For people identified as having a 'white-coat effect', consider ABPM or HBPM as an adjunct to clinic BP measurements to monitor the response to antihypertensive treatment with lifestyle modification or drugs
  • When using ABPM or HBPM to monitor response to treatment (for example, in people identified as having a 'white coat effect' and people who choose to monitor their BP at home), aim for a target average BP during the person's usual waking hours of:
    • below 135/85 mmHg for people aged under 80 years
    • below 145/85 mmHg for people aged 80 years and over.

9 Contraception

Combined oral contraceptive (COC) pills tend to increase BP by an average of 5/3 mmHg.8

The rise in BP due to the COC appears to be idiosyncratic. In a small proportion of women, around 1%, severe hypertension may be induced. No particular subgroup of women has been identified as particularly susceptible, and BP may rise months or years after first using a COC. Observational data suggest that the progesterone-only pill and hormone replacement therapy (HRT) do not, on average, raise BP and are the preferred choice for women with hypertension. Similarly, women with hypertension should not be denied access to HRT as long as BP levels are effectively controlled.8

Blood pressure should be checked before commencing the COC and should be checked again 3 months later.9 A yearly follow up is recommended, although 6-monthly checks have also been suggested.8,9

10 Elective surgery

Primary care teams should ensure that patients being admitted to hospital for elective surgery have a mean SBP level of <160 mmHg and DBP level of <100 mmHg in the previous 12 months.10

In order to minimise cancellations and postponement of non-urgent surgery, there is a requirement for primary care to provide BP readings from the last 12 months in the referral letter. A level of <180 mmHg SBP and <110 mmHg DBP at preoperative assessment should not preclude elective surgery, and only those with a BP above this level should be returned to their GP for assessment and appropriate management of their BP. 10 The management should follow best practice as outlined in NICE Clinical Guideline 127.2

References

  1. British Hypertension Society. Blood pressure measurement fact file 01/2006. BHS, 2006. Available at: bhsoc.org/files/6813/4398/9702/BHS_BP_Measurement_Factfile_2006.pdf
  2. NICE. Hypertension in adults: diagnosis and management. Clinical Guideline 127. NICE, 2011. Available at: www.nice.org.uk/guidance/CG127
  3. British Hypertension Society. Blood pressure measurement with electronic blood pressure monitors. BHS. Available at: bhsoc.org/files/8413/4390/7770/BP_Measurement_Poster_-_Electronic.pdf
  4. JBS3 Board. Joint British Societies' consensus recommendations for the prevention of cardiovascular disease (JBS3). Heart 2014; 100: ii1–ii67.
  5. Department of Health. UK Chief Medical Officers' alcohol guidelines review: summary of the proposed new guidelines. DoH, 2016. Available at: www.gov.uk/government/uploads/system/uploads/attachment_data/file/489795/summary.pdf
  6. NICE. Full guideline: Hypertension: the clinical management of primary hypertension in adults. Clinical Guideline 127. Methods, evidence, and recommendations. National Clinical Guideline Centre, 2011. Available at: www.nice.org.uk/guidance/cg127/evidence/full-guideline-248588317
  7. General Medical Council. Good practice in prescribing and managing medicines and devices. GMC, 2013. Available at: www.gmc-uk.org/Prescribing_guidance.pdf_59055247.pdf
  8. Williams B, Poulter N, Brown M, et al. British Hypertension Society guidelines for management of hypertension: report of the fourth working party of the British Hypertension Society, 2004-BHS IV. J Hum Hypertens 2004; 18 (3): 139–185.
  9. Faculty of Sexual & Reproductive Healthcare. Clinical Effectiveness Unit. Combined hormonal contraception. FSRH, 2011 (updated 2012). Available at: www.fsrh.org/pdfs/CEUGuidanceCombinedHormonalContraception.pdf
  10. Hartle A, McCormack T, Carlisle J et al. The measurement of adult blood pressure and management of hypertension before elective surgery. Anaesthesia 2016; 71: 326–337 G