- Diagnosis, Pathology and Management of Hypertension
- Normal Control of BP
Diagnosis, Pathology and Management of Hypertension
WHO criteria for defining hypertension:
- Under 50 – should try to get it under 140/90
- Over 50 – should try to get it under 160/95
NICE guidelines
Offer treatment to patients with:
- Blood pressure >160/100 – on a one-off occasion
- Blood pressure >140/90 – one two consecutive visits to the GP
- Systolic of greater than 160
- Blood pressure >140/90 – and 10 year CVD risk of >20%, OR, existing CVD organ damage
The aim of treatment is to get BP to less than 140/90.
Remember:
- Cardiovascular risk increases with BP, even in the ‘normal limit’
- Using the WHO criteria, up to 25% of the population have hypertension
- Hypertension produces structural changes in the heart and cardiovascular system. This causes complications that are referred to as target organ damage.
- Be wary of white coat hypertension – the phenomenon is real! It exists with doctors, and to a lesser extent, nurses. You may weed out many cases of this by taking several readings on different occasions – in cases of white coat hypertension, the readings will gradually approach the normal level. You could also try a 24 hour BP monitor. If white coat hypertension is treated, as ‘real hypertension’, then the patient can suffer serious hypotension when away from the GP’s surgery – and this can be dangerous!
- When you start somebody on antihypertensive medication, it is likely they will be on it for life! Thus you shouldn’t make the decision lightly, and should ensure you have sounds readings as a basis.
- Up to 20% of individuals suffer white coat hypertension
- The risk of cardiovascular complications of those with white coat hypertension is much less than those with ‘proper’ hypertension, but still greater than those that exhibit no white coat hypertension.
- 24 hour BP measurements are chronically lower than those in a clinical setting – by approximately 12/7mmHg, and as such, they must be adjusted. Also, note that you take an average of the BP during the day not during the night
- The ‘ideal blood pressure’ is 120/80 – however, the actual distribution of blood pressures is like a bell curve, so ‘normal’ for some people is very low (or perhaps even very high!)
- You cant take a BP of a person with atrial fibrillation with an electronic machine! The machine just comes up error.
When taking a reading
- Patient should be relaxed, but not talking
- Read to the nearest 2mmHg
- Repeat after 5 minutes if the first reading is raised
- Repeat on at least 2 separate visits to the GP if still raised
- Remove tight clothing from the arm
- Support the arm at the level of the heart
- Use an appropriate size cuff – the bladder in the cuff must be at least 2/3 the circumference of the arm
- Use phase 5 of the korotkoff sounds to measure diastolic BP
- Phase 4 – this is where the sounds become muffled
- Phase 5 - this is where the sounds completely disappear
- Adults should have their BP measured at least every 5 years up the age of 80
- You should take sitting and standing readings in those with diabetes and the elderly to exclude orthostatic hypotension
- You need at least 2 consistently high results (on separate occasions), or 3+ high results (when numbers vary between each reading) to diagnose hypertension.
Epidemiology
- BP rises with age (up to the 7th decade). This rise is more pronounced in the systolic pressure, and more common in men
- Hypertension is present in roughly 30-40% of the population
- Hypertension is more common in black Africans – 40-45% of adults
Classification
It is important to distinguish the tow types because in secondary hypertension you can treat the cause but in essential hypertension, you cannot.
Essential hypertension
This is where no underlying cause can be found, and it accounts for 90-95% of cases of hypertension.
It has multifactorial aetiology
Genetic factors – high blood pressure tends to run in families. 40%-60% have a genetic component
Foetal factors – low birth weight is associated with hypertension (and also CVD) in later life. This could be due to adaptive changes the foetus makes in the uterus to under nutrition. These changes could change the structure of arteries, resulting in hypertension later in life. Hormonal systems may also be altered
Environmental factors:
- Obesity – fat people have a higher blood pressure than thin people. However – there is also a tendency to overestimate the BP when it is measured with a small cuff. Sleep disordered breathing is also seen with obesity, and may be an additional risk factor
- Alcohol intake – there is a very strong correlation between alcohol intake and blood pressure. However – people who consume small amounts of alcohol tend to have a lower BP than those who consume none at all – the ‘one glass of red wine a day’ thing
- Sodium intake – this is controversial. There is currently no strong evidence that consuming a high sodium diet is causal in hypertension, only that it exacerbates existing hypertension. Nevertheless, those with a high sodium diet have a higher BP than those with a low sodium diet. High sodium diet is also associated with a western, urbanised lifestyle.
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