Treatment of high blood pressure – Dr. Gnana Sankaralingam
Heart beats to push blood into the arteries to supply tissues and organs, and when doing so encounters resistance which results in building up of pressure within blood vessels. What is called blood pressure is the measurement of force exerted against walls of arteries during pumping action of the heart. There are two forces: Systolic blood pressure recorded during contraction of the heart and Diastolic blood pressure recorded when heart relaxes to refill. Due to ageing process, walls of arteries become calcified and stiff which increases the resistence leading to elevation of blood pressure (Hypertension). Initially there may not be any complaint but as the problem persists, patients experience various symptoms.
According to WHO criteria, normal blood pressure is Systolic 120 and Diastolic 80. If it is 120 to 130 by 80 to 85 it is elevated blood pressure, if it is 130 to 140 by 85 to 90 it is grade 1 hypertension, if it is above 140 by 90 it is grade 2 hypertension and if it is above 180 by 110 it is hypertensive crisis. To label a person as having high blood pressure, at least two readings should be taken and on two separate occasions. More accurate method would be ambulatory blood pressure monitoring over 24 hours on seven days. Blood pressure should be checked for all middle aged and if it is normal, follow up done after an year. If it is 120 to 130 by 80 to 85, only life style modification advised and followed up in six months.
Hypertension can be essential where there is no known cause or secondary where there is an underlying condition. Prolonged hypertension may cause damage to organs such as heart (left ventricular hypertrophy), eyes (retinopathy) and kidneys (albuminuria leading to chronic kidney disease). Various life style factors such as stress, smoking, alcohol, lack of exercise and unhealthy diet can predispose to hypertension. Once diagnosed, person should be investigated for causative factors as well as end organ damage with ECG, cholesterol and sugar level, urine for albumin and creatinine, calcium (hyperparathyroidism) and potassium (Conn’s syndrome) level and 24 hour urine catecholamine excretion (Phaeochromocytoma). Treatment depends according to findings of causative factor or end organ damage.
Due to raised blood pressure, heart has to exert more force to pump blood which causes the left ventricle muscles to enlarge (hypertrophy). After some time heart will not be able to cope with it and starts to fail (left ventricular failure). High blood pressure affects the small arteries in the kidneys leading to leaking of albumin in the urine which predisposes to chronic kidney failure. Eye changes in hypertension begins with generalised constriction of small arteries followed by focal narrowing and arterio-ventricular nicking. In the next grade, there will be flame shaped haemorrhages, cotton wool spots and hard exudates. Until this stage it is usually asymptomatic. If blood pressure rises above 180 systolic and 110 diastolic (malignant hypertension) there will be swelling of optic disc (papiloedema) causing blurring of vision, visual field defects and sudden painless loss of vision due to vessel occlusion. High blood pressure can weaken walls of large arteries leading to aneurysmal dilatation prone to rupture. It also causes changes in brain due to thickening of cerebral vessels predisposing to hypertensive encephalopathy (unconsciousness and fits) and haemorrhagic stroke. Life style modification includes exercise, diet control, wieght loss and cessation of smoking and alcohol intake. Exercise should be for 30 mins a day such as jogging, swimming, cycling or Yoga. Dietary measures are by limiting salt intake to 5gm per day and controlling sugar and cholestrol levels. Increased potassium intake may be beneficial, other than those with kidney impairment. Weight should be monitored regularly and be maintained.
In the first visit, categorise the patient according to blood pressure reading. If at any time, those who were found to be normal and kept under observation, or those labelled as having elevated blood pressure and advised life style modification, the blood pressure is now higher (systolic >130 and diastolic >85), drug treatment has to be initiated. This is the same for those who recorded this reading at their first visit. Assess for risk factors and end organ damage, and if none advise life style modification and review in three months, but if present start on single drug and review in a month. If control is achieved with a single drug continue with it, if not you could increase the dosage, change to a new drug or add another drug. Continue with it if control is achieved or else consider alternate drug regimen.
If at the first visit or at any time blood pressure is constantly over 140 systolic and 90 diastolic, drug treatment is started together with life style modification. Begin with two drugs: Calcium channel blocker and either ACE inhibitor or Angiotensin receptor blocker in small doses and review in 3 months. If controlled continue with it and if not, increase doses and review in 3 months. If controlled continue with it and if not, increase doses add Thiazide diuretics and review in 3 months. If still not controlled you could try adding Spironolactone. If still no response, check for compliance of drugs and life style and consider centrally acting drugs as Clonidine or Methyl Dopa. Target blood pressure in those with co-morbidity or end organ damage is 130 systolic by 80 diastolic and those without 140 systolic and 90 diastolic. Beta blockers are preferable for heart problems like heart failure, angina or palpitation and ACE inhibitors are preferable for diabetes, albuminurea or kidney disease except stage 4. In elderly (>80 years), drug of choice is Thiazide diuretics or Calcium channel blockers.
If blood pressure is over 180 systolic or 110 diastolic, it is called hypertensive crisis common causes of which are resistant hypertension (not controlled by three dugs or at end stage chronic kidney disease). If no end organ damage, it becomes an urgency and if present it becomes an emergency. For urgency, controlled reduction of blood pressure is done over several days as immediate drop could cause ischaemic stroke. Bed rest with oral medication such as beta blockers or calcium channel blockers is prescribed. For emergency, controlled reduction of blood pressure is done during course of hours with intra-arterial blood pressure monitoring. It is brought down to 160 systolic and 100 diastolic slowly in six hours and then gradually brought to normal range. Drugs used are Labetolol 50mg IV over 1 min repeated if necessary every 5 mins to a maximum of 200mg or Sodium Nitroprusside infusions.
New treatment is in the horrizon called “Renal denervation”, in which a catheter is passed through arteries into renal artery and ultrasound or radiofrequency energy beamed, whose pulses pass along arteries in kidney to selectively target surrounding nerves.
