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