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All you need to know about hypertension

Hypertension is a major contributor to cardiovascular diseases such as stroke and heart attacks, but lifestyle changes and pharmacological interventions can make a significant difference. Hypertension specialist nurse Alison Campbell explains …

Alison Campbell
RGN Nurse Prescriber
Hypertension Specialist Nurse
University Hospitals of Leicester NHS Trust

High blood pressure affects over 16 million people in the UK, but is adequately treated in less than a third of those affected. Persistently raised blood pressure (hypertension) can be detected, monitored and treated by practice and community nurses with the necessary knowledge and experience. Hypertension is a silent condition that may have no symptoms for many years until the damage is done. It is the most important risk factor for stroke, and is one of the three major risk factors, along with cholesterol and smoking, for coronary heart disease.
Hypertension is also one of the most controllable conditions in primary care with many different classes of antihypertensive medications available as well as lifestyle changes that can make a positive difference to the risk of heart attacks and strokes.
Blood pressure is regulated by a number of
physiological systems such as the vasomotor centre, reninangiotensin system and baroreceptor reflexes. If the blood pressure is persistently high there is damage to the arterial walls and the organs that the blood vessels supply. This first noticeably affects the heart (left ventricular hypertrophy [LVH]), eyes (hypertensive retinopathy) and kidneys (renal impairment).
Up to 95% of all hypertension in adults is essential hypertension, which has no known underlying cause and is probably a result of genetics, environmental and lifestyle factors (see Box 1). Patients can often be reassured that their blood pressure can be controlled by a combination of lifestyle changes and medication. Rarely secondary causes are found (see Box 2).

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Blood pressure measurement
Measuring blood pressure accurately is vital to diagnosing and managing hypertension. This measurement may result in a lifetime of medication and has implications for those applying for insurance and with occupations such as HGV driving or flying.
Blood pressure (BP) should be measured with a validated and currently calibrated monitor (see www.bhsoc.org). You may find it impossible to measure BP with an automatic monitor in someone with an irregular pulse, and it is essential to have an alternative available using mercury or a pressure device designed to use with a stethoscope.
Make sure the arm circumference is measured and the appropriate sized cuff is used. The inner bladder of the cuff should surround 80% of the arm. Take blood pressure readings in both arms while your patient is sitting - use the higher reading arm for future measurements. Measure the standing blood pressure in anyone with symptoms of postural hypotension (falling or dizzy when sitting up or standing) (see Box 3).

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Initial screening for hypertension
Measure the blood pressure on any patient with no recorded readings in the past five years. There is no actual blood pressure below which there is no risk of cardiovascular disease. However, the threshold at which blood pressure is treated has been agreed as the level above which the benefits of treatment outweigh the risks (see Box 4).

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Take three readings with one-minute intervals on at least three occasions if your patient has raised blood pressure before diagnosing hypertension. The interval for recalling patients depends on their blood pressure level. Fortnightly or monthly repeat visits may be fine for confirming established hypertension. However, for those with blood pressure > 220/120 mmHg a practitioner experienced in examining for papilloedema and retinal haemorrhage needs to assess the patient urgently to exclude malignant hypertension. If no such person is immediately accessible, refer urgently to the emergency department. If confirmed as malignant, hospital admission is required for close monitoring and treatment.

What else needs to be done?
When blood pressure is first found to be raised it is worth assessing the patient's own and family history of cardiovascular disease or diabetes. Current medications such as the combined oral contraceptive pill, steroids, nonsteroidal anti-inflammatory drugs, antidepressants and nasal decongestants can increase BP, as can certain herbal or complementary medicines. Each time blood pressure is measured, take the opportunity to assess any lifestyle issues and encourage patients to make changes where necessary.

If hypertension is confirmed what next?
Cardiovascular risk assessment is essential for anyone with hypertension using recognised risk charts such as those found in the British National Formularly (BNF) based on age, gender, pretreatment BP, smoking status and pretreatment total cholesterol to HDL ratio. These are useful for making the decision for initiating antihypertensives, cholesterol therapy and aspirin.
Essential investigations for newly-diagnosed hypertensives include:

  • Blood tests for U&Es, glucose and lipid profile.
  • Urinalysis for glucose/protein.
  • Electrocardiograph (ECG) can detect left ventricular hypertrophy: the sum of the S-wave in lead V1 or V2 and the R-wave in lead V5 or V6 is 35 mm or more, or atrial fibrillation (no visible P-waves and a normal QRS occurring at irregular intervals).

Lifestyle assessment at each visit needs to cover smoking, diet, exercise and alcohol intake (see Table 1). A motivated person who is encouraged to make modifiable lifestyle changes may be able to reduce their blood pressure to below threshold levels.

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Treatment
NICE/BHS has introduced a simple ACD algorithm (see Figure 1). Only 30-40% of patients are likely to reach their blood pressure target with monotherapy and additional treatment is often necessary (see Box 5). Thiazide diuretics are suitable firstline treatment in essential hypertension in the over 55 years age group and black patients of any age.

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Calcium channel blockers (CCBs) are also suitable firstline agents for patients over 55 years and black patients of any age. The dihydropyridine CCBs have an effect on vascular smooth muscle causing vasodilation, which can result in headache and ankle swelling.
Angiotensin-converting enzyme (ACE) inhibitors have an effect on the renin-angiotensin system and NICE recommends them as initial therapy for those under 55 years unless they are black.(1) The white, Asian and young (ARBs are more specific and prevent angiotensin-II binding at the receptor site so the cough associated with ACE inhibitors is unlikely. The precautions taken with ARBs are the same as with ACE inhibitors.

Review and future monitoring
Hypertension patients should have their blood pressure reviewed six to eight weeks following any change in treatment. A minimum six-monthly BP check and annual review is required for all hypertension patients. This could include urinalysis and BP check as above and relevant blood tests; urea and electrolytes need to be measured annually for those taking diuretics and monitoring is recommended to detect in particular hypokalaemia or raised urate levels. Patients taking ACE/ARBs require their renal function to be checked one to two weeks after starting therapy, with increased doses and annually. There is a small risk of hyperkalaemia, especially in patients with renal impairment or those taking potassium-sparing diuretics or potassium supplements, including sodium salt replacements.
Reinforce lifestyle advice and give encouragement to continue with changes. Ask about the side-effects of medication (see Box 6).

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Antihypertensives are generally well tolerated, but, as with many chronic diseases, these medications are not always taken as prescribed. Once-daily doses of medications should be used to help concordance. Provide information on the benefits and risks of taking lifelong antihypertensive medication, and explain how taking medication will significantly reduce their risk of developing a heart attack, stroke, renal failure or heart failure. Patients may have issues around their prescribed medications such as side-effects, perceived risk and benefit. These will need to be explored in more depth to involve the patient in the decision and to enable them to make an informed choice.
Patients with apparently resistant hypertension could be encouraged to monitor their own blood pressure at home to exclude a white coat effect. Advise this with caution for the anxious patient. All patients will benefit from education on their current and target blood pressures and can find take-home literature beneficial. The Blood Pressure Association (BPA) will provide a comprehensive information pack free of charge to patients (see Resources).
Individual practices aiming for the maximum QOF points in hypertension should have an established register of their hypertension patients and ensure that they are recalled and measured every six months with blood pressures

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Consider referral to a specialist hypertension clinic if:

  • Under 30 years old.
  • Pregnant at any stage or hypertensive and planning pregnancy.
  • Headache, palpitations and pallor - possible phaeochromocytoma.
  • Serum levels of potassium  144 nmol/l may indicate primary or secondary hyperaldosteronism (Conn's syndrome).
  • Creatinine > 120 µmol/l or greater than 50% increase after starting ACE inhibitor or ARB may indicate bilateral renal artery stenosis.
  • Renal impairment - protein in urine (infection excluded).
  • Reached step 4 of ACD step treatment with blood pressure not controlled (see Figure 1).
  • Multiple drug intolerance or contraindications.

Conclusion
Detecting, treating and managing hypertension is a growing workload for many nurses. With an increasing elderly and more prevalent obese population this is set to continue. National and local guidelines are readily available, but sometimes it is easy to lose sight of the fact that for most patients reducing blood pressure effectively is more important than the method of blood pressure reduction. Remember to treat the patient not the blood pressure!

References

  1. National Institute for Health and Clinical Excellence. Clinical Guideline CG34. Hypertension: management of hypertension in adults in primary care. London: NICE; 2006. Available from: http://www.nice.org.uk/CG034
  2. Williams B, Poulter NR, Brown MJ, et al. Guidelines for management of hypertension: report of the fourth working party of the British Hypertension Society, 2004-BHS IV. J Hum Hypertens 2004;18:139-85.


Resources

Nurses Hypertension Association: www.nha.uk.net
Network of  nurses hypertension association with special
interest in hypertension

British Hypertension Society: www.bhsoc.org
medical and scientific society website . Contains current
validated blood pressure monitors and guidelines

NICE: www.nice.org.uk
Guidance on cost-effective hypertension management

Blood Pressure Association: www.bpassoc.org.uk
Patient website with useful downloadable literature

National Prescribing Centre: www.npci.org.uk
Information for nurse prescribers with useful aids for
concordance