Hypertension

Hypertension is a blood pressure >140/90mmHg.

Background

  • Around 30% of adults have a BP of >140/90mmHg
  • Prevalence increases with age (30% aged 45-54; about 70% in peopler ages 75+ years)
  • More common in African-Caribbean than in Caucasian people
  • Hypertension is one of the most common conditions seen in patients and one of the most common reason for prescribing medications
    • Accounts for >£1 billion worth of drugs per year

Aetiology/Pathophysiology

  • In the majority of individuals, a specific cause of hypertension is not found (essential hypertension)
  • There are many factors that are thought to contribute to primary hypertension:
    • renal dysfunction (via RAAS as well as salt/water excretion)
    • peripheral resistance and vessel tone
    • endothelial dysfunction
    • autonomic tone
    • insulin resistance
    • neurohumoral/immunological factors
    • genetic factors
  • Secondary hypertension can be caused by
    • Alcohol
    • Obesity
    • Pregnancy
    • Renal disease
    • Endocrine disease
    • Drugs
      • e.g. OCP, anabolic/cortico-steroids, NSAIDs, sympathomimetic agents

NB It is important to take a full history from a patient with hypertension to rule out any underlying causes for secondary hypertension and to evaluate whether the patient has any target organ damage.  E.g. Full drug hx; do they have any symptoms e.g. headache, sweats/palpitations (could this be a phaeochromocytoma?).  Is there a family history of renal disease? Does the patient appear cushingoid?

Diagnosis/Classification

  • Note that “white coat” hypertension can be confounding.  This is blood pressure that is unusually high simply due to the anxiety and/or concerns about seeing the doctor.
  • Measuring blood pressure
    • It is important to try and keep the environment constant whilst measuring blood pressure e.g. relaxed, quiet, seated with arm outstretched and supported at heart level (ideally the arm should be bare)
    • If there is a difference of >20mmHg between arms, record measurements from the arm with higher BP
    • If the first reading is >140/90mmHg, take a second after a minute interval.  If this is substantially different, record a third measurement too.  Use the lower of the last two measurements.
    • If all measurements are consistently >140/90mmHg, recheck BP on 2-3 occasions over the next few weeks
      • If clinic BPs are persistently above 140/90mmHg, offer ambulatory blood pressure monitoring or home blood pressure monitoring
  • Classification
    • Mild (Stage I)
      • clinic BP >140/90mmHg and ABPM average is >=135/85mmHg
    • Moderate (Stage II)
      • clinic BP >160/100mmHg and ABPM average is =>150/95mmHg or there is isolated SBP of >=160mmHg
    • Severe (Stage III)
      • clinic BP >180/110mmHg
      • NB if a patient has this high a BP, check the retina for hypertensive retinopathy (papilloedema and/or retinal haemorrhage).  Also take bloods (FBC, U&Es and LFTs), urinalysis and do an ECG for signs of other system failure e.g. acute kidney injury
        • Malignant hypertension is defined as grade III hypertension with signs of secondary organ damage

Other investigations

  • As well as BP, ECG, Bloods and urinalysis
    • Test glucose (diabetes)
    • Test cholesterol for cardiac risk

Management

  • Lifestyle advice
    • Alcohol consumption; caffeine consumption; salt consumption
    • Smoking
    • Stress
    • Don’t take electrolyte supplements
    • Exercise/physical activity
    • Weight loss
    • Diet
  • Assess cardiac risk
    • There are several ways of assessing risk
      • QRISK2 (see here)
      • ASSIGN score (see here– more commonly used in Scotland)
      • In general, a score of >20(% in 10 years) and age >50 years suggests intervention, including low-dose aspirin (75mg), statin treatment
  • Antihypertensive medication
    • Offer if
      • <80yo; mild hypertension and one or more of
        • Target organ damage, established CVD, renal disease, diabetes and/or a 10 year CV risk of 20% or more (using ASSIGN or QRISK2)
      • Moderate Hypertension (all)
    • If <55yo (and not African-Caribbean)
      • start an ACE inhibitor or (if intolerant/contraindicated) an Angiotensin-II-receptor blocker
        • In Moderate to severe renal disease, reduce the dose of ACEIs (cleared by the kidney)
        • Relatively contraindicated in bilateral renal artery stenosis
        • Drug interactions (important ones): DO NOT CO-PRESCRIBE ACEI, NSAID +/-  ARB
      • Alternatively, a beta-blocker can be used in young patients
        • who can’t tolerate ACEIs/ARBs
        • women who might become pregnant or are planning a pregnancy
        • NOTE that whilst beta-blockers are recommended by NICE for the treatment of hypertension, SIGN does not recommend their use first line (only after 3-combination therapy has been tried)
          • this is because ‘beta blockers were the least clinically and cost effective drug at preventing major CV events’
        • Use can be limited by side effects: cool peripheries, fatigue and impotence are common.  Headache/postural hypotension is also possible.
    • If >55yo or Afro-Caribbean
      • Offer a calcium-channel blocker (dihydropyridine type e.g. amlodipine) unless there is evidence of oedema, heart failure (or risk of heart failure), or drug intolerance
        • In this case, offer a thiazide diuretic or a thiazide-like diuretic
    • Note that if BP remains uncontrolled on one drug
      • Offer combination of CCB/TD/TLD and ACEI/ARB*/BB
        • Preferred in African/Caribbean patients
      • If the patient’s BP remains high with 2 drugs at optimal doses
        • consider ACEI/ARB + CCB + TD/TLD
      • If still resistant to treatment (resistant hypertension)
        • sensible to refer to a specialist
        • It is possible to combine all 3 drug types.  Alternatively, low dose spironolactone can be added (or higher dose thiazide diuretic)
          • the former if K < 4.5 and the latter if >4.5
          • patients require close monitoring of their U&Es (particularly K+)
  • Admit a patient if they have
    • Malignant hypertension
    • Hypertensive encephalopathy
    • Suspected phaeochromocytoma and severe hypertension
    • Severe hypertension and high risk of vascular complications
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