VOL: 98, ISSUE: 02, PAGE NO: 32
Elizabeth Harbron, DipHealthStudies, is cardiac nurse practitioner, University Hospital of North Tees, North Tees and Hartlepool NHS TrustThere is still great uncertainty about the pathophysiology of hypertension (abnormally high blood pressure). In a small number of cases (2-5%) the condition is caused by underlying renal or adrenal disease, but for most patients there is no single identifiable cause and their condition is labelled as 'essential hypertension' (Beevers et al, 2001).
There is still great uncertainty about the pathophysiology of hypertension (abnormally high blood pressure). In a small number of cases (2-5%) the condition is caused by underlying renal or adrenal disease, but for most patients there is no single identifiable cause and their condition is labelled as 'essential hypertension' (Beevers et al, 2001).
Hypertension occurs more often in people with a family history of the condition, diabetes or obesity. The incidence is also higher in Afro-Caribbeans than in other ethnic groups, and in urban rather than rural dwellers (Drummond, 2000; O'Brien et al, 1995). It is one of the main risk factors for coronary and cardiovascular diseases in most developed countries and has been shown to be a public health problem in many developing countries since the 1970s (Fuentes et al, 2000).
All approved hypertensive drugs lower blood pressure (BP) but, in terms of reducing the risk of long-term complications such as myocardial infarction, stroke or heart failure, only low-dose diuretics and beta-blockers are consistently successful (Psaty and Furberg, 1999). This article evaluates the role of bendrofluazide (a low-dose diuretic) and metoprolol (a beta-blocker), which are considered the optimum treatment for hypertension. The use of non-pharmacological measures and hawthorn in the treatment of hypertension are also discussed.
In an attempt to improve the management of hypertension in the UK, Ramsay et al (1999) produced guidelines based on the best available evidence. They recommend low-dose thiazide diuretics or beta-blockers as first-line therapy for most hypertensive people (in the absence of contraindications or compelling indications for other antihypertensive agents). A combination of these drugs is usually required to achieve the recommended targets for BP control.
Optimal targets are systolic <140mmhg and="" diastolic="">140mmhg><85mmhg. the="" minimum="" acceptable="" level="" of="" control="" (audit="" standard)="" is="">85mmhg.><150>150><90mmhg. the="" guidelines="" state="" that="" the="" treatment="" of="" people="" with="" sustained="" systolic="" bp="" of="" 140-159mmhg="" or="" sustained="" diastolic="" bp="" of="" 90-99mmhg="" should="" also="" take="" into="" account="" the="" presence="" or="" absence="" of="" target-organ="" damage,="" cardiovascular="" disease="" or="" a="" 10-year="" coronary="" heart="" disease="" risk="" of="">15% (Ramsay et al, 1999).
It has been suggested that non-pharmacological advice should be offered to all hypertensive patients and people with a strong family history of hypertension. If it is implemented there may be no need for drug therapy or the dose and/or number of drugs may be reduced. In patients with mild hypertension but no cardiovascular complications or target-organ damage, the response to these measures should be monitored for the first four to six months of evaluation. If drug therapy has to be introduced more quickly, non-pharmacological measures should be continued alongside it.
Hypertensive patients are at increased cardiovascular risk and should be supported in attempts to stop smoking, achieve their ideal weight, improve their diet and increase exercise (Ramsay et al, 1999). Appel et al (1997) confirm that changes in diet and lifestyle lower BP and may also reduce cardiovascular risk.
Stamler (1998) recommends a diet high in fruit, vegetables, legumes and whole grains, with fat-free and low-fat dairy products, poultry, fish, shellfish and meat products. Intake of salt, total fat, saturated fat and cholesterol should be reduced, with no more than two or three units of alcohol a day, while calories should be controlled to prevent or reduce obesity. Appel et al (1997) suggest that this could lower BP as much as drug monotherapy or reduce the need for drug treatment, while reducing overall cardiovascular risk.
However, Wilding and Williams (2000) state that achieving ideal bodyweight is not a realistic goal for lifestyle intervention. This may be impossible in obese subjects and the evidence suggests that more modest (and achievable) reductions in weight of 5-10% can lower systolic and diastolic readings in the range of 4-7/3-6mmHg respectively.
Wasling (1999) found that although most people understand the concept of a healthy diet in terms of eating less saturated fat and more fibre, they are not always sure how to put this into practice. Many patients focus on fat reduction but fail to recognise the importance of increasing fruit and vegetable intake. Clear verbal and written advice should be provided for all hypertensive patients and those with high to normal BP or a strong family history.
These non-pharmacological measures require enthusiasm, knowledge, patience and time with patients and their families. Communication and rapport are vital to prevent the consequences of high BP.
Implications for resources
Eisenberg (2000) suggests that, by lowering the threshold for treatment, the guidelines have created vast numbers of new hypertensive patients. A conservative estimate is that, on average, newly identified patients need four appointments a year, especially in the first 12 months. In addition to new patients, there are also established patients who are no longer adequately controlled and new hyperlipidaemic patients. It is difficult to tell how many extra patients each GP and practice nurse will be expected to see each week. To prevent surgeries from spending increasing amounts of time and resources on patients receiving preventive care at the expense of those who are ill, one solution may be to give practices extra resources (mainly an increase in practice nursing hours).
Management of hypertension
All adults should have their BP measured at least every five years until the age of 80, while those with normal or high values (135-139/85-89mmHg) and those who have had high readings previously should be measured annually (Ramsay et al, 1999).
Only two groups of drugs - low-dose diuretics and beta-blockers - have been shown to reduce long-term mortality from the complications of hypertension. There is general support for their use as first-line treatments and concern that newer, more expensive drugs should not replace them until they have been shown to be as beneficial.
Since all antihypertensives reduce BP by about the same extent, the same long-term benefits might reasonably be expected regardless of which class of drug is used (National Prescribing Centre, 1995). However, replacing thiazides and beta-blockers with newer agents could cost millions of pounds and would not represent an evidence-based approach to treatment. Given the current emphasis on evidence-based practice, it seems logical to select antihypertensive agents that have been shown to prevent long-term complications (Hicks and Hennessy, 1997).
Bendrofluazide is a thiazide diuretic that is widely used, alone or with a beta-blocker, for mild, moderate and severe hypertension. However, it can provoke acute gouty arthritis as it raises serum uric acid by inhibiting renal urate excretion. Long-term therapy may also impair glucose tolerance by inhibiting the release of insulin from the pancreas, decreasing diabetic control (Reid et al, 1992).
The British National Formulary advises that bendrofluazide should not be used during pregnancy as it can cause neonatal thrombocytopenia. Increases in total cholesterol, low-density lipoprotein and triglyceride levels have also been reported after long-term use. Other side-effects include low magnesium levels, dizziness, headaches, nausea, vomiting, urticaria, blood dyscrasias and mild hypocalcaemia (Kee and Hayes, 2000).
Although beta-blockers are effective antihypertensives, their mode of action is not fully understood (Parish, 1992). They decrease the effects of the sympathetic nervous system by blocking the release of adrenaline and noradrenaline at the receptor site. Metoprolol is a competitive beta-adrenoceptor antagonist that inhibits beta1-adrenoceptors, is devoid of intrinsic sympathomimetic activity and possesses beta-adrenoceptor blocking activity comparable to propranolol.
A negative chronotropic effect on the heart is a consistent feature of metoprolol administration, so cardiac output and systolic BP rapidly decrease after acute administration. However, some beta-blockers are non-selective, blocking both beta1 and beta2 receptors, decreasing the heart rate and BP, and causing bronchoconstriction (Kee and Hayes, 2000).
Fat-soluble beta-blockers such as metoprolol can cross the blood-brain barrier and the placenta, and be distributed into breast milk. By entering the brain the drug may produce adverse effects such as poor sleep and nightmares (Parish, 1992).
Lundborg et al (1981) studied the newborn infants of mothers treated with metoprolol and found that none showed signs of beta-blockade. They concluded that only a small amount of metoprolol appears to be distributed into breast milk. The British National Formulary agrees, but recommends monitoring of the infant for possible beta-blocker toxicity.
To discontinue the use of metoprolol after long-term therapy, it is recommended that the dose be slowly reduced over about 14 days. Patients should be advised to avoid vigorous physical exercise or activity during this time to decrease the risk of cardiac dysrhythmia (Salerno, 1999).
Many practitioners, both orthodox and complementary, recommend that hypertensive patients take courses in relaxation. In the relaxed state adrenaline levels are lowered, which reduces muscle tension, induces regular diaphragmatic breathing and promotes mental calm. The body uses less energy than usual and there is less work for the heart, lungs and brain. Regular relaxation exercises have been shown to lower BP, but this is used mainly as an adjunct to treatment (Vincent and Furnham, 1997).
Complementary therapy is widely used in Australasia, Britain, Europe and the USA. The reaction of medical professionals has varied. Some have incorporated various therapies into their own practice, while others dismiss them as, at best, harmless forms of comfort and, at worst, dangerous quackery that may deprive people of effective medical treatment (Ernst, 1996).
Herbalism and hypertension
Herbalists aim to detect imbalances and restore normal function rather than acting to reverse pathology. Their approach is based on supporting the body's ability to correct its own imbalances. There are thousands of herbal remedies, some of which can provoke protective reactions within the body.
Hawthorn can protect against the development of hypertension and heart disease, provided it is used alongside other healthy habits, such as a balanced diet and plenty of exercise. The modern development of hawthorn extracts began with the discovery of the flavonoids in the plant. These compounds protect it from the harmful rays of the sun and fight free-radical damage.
Pharmacological and clinical studies indicate that regular, long-term use of hawthorn has a number of outcomes (Wichtl and Bisset, 1994):
- Improved coronary arterial output;
- Dilation of blood vessels;
- Reduced pressure in capillaries and pulmonary arteries;
- Enhanced blood supply to heart muscles;
- Enhanced contractility and resistance of the heart muscles to oxygen deficiency, reducing peripheral vascular resistance and increasing circulation to the extremities.
Hawthorn is considered a safe herb. It has no known interactions with prescription cardiac drugs or toxicity reports for pregnant or nursing mothers.
However, it should be remembered that self-diagnosis and self-treatment of such vital systems as the heart and blood vessels is dangerous.
Evidence indicates that lifestyle changes do reduce hypertension and should be encouraged. The medical approach supports the use of bendrofluazide and metoprolol in hypertensive patients. However, evidence suggests that these drugs are not the optimum choice for all patients, such as those with asthma, gout, symptoms of coronary heart disease (angina) or poor circulation, which may be treated with a calcium antagonist, while ACE inhibitors may be preferred in patients with diabetes (Luker and Wolfsen, 1999).
Finally, just as evidence-based medicine is coming to the fore, so must evidence-based complementary medicine. Critics point to the lack of evidence supporting these therapies, yet hawthorn has been shown to be effective in hypertension and angina. Also, the fact that so many people choose to attend complementary practitioners when health care is largely free at the point of delivery suggests that they are receiving something that is important to them (Vincent and Furnham, 1997) - perhaps a successful therapeutic relationship.90mmhg.>