Guidelines And Recommendations

Current national and international guidelines on the management of hypertension emphasise the need for effective lowering of blood pressure in diabetic subjects to reduce the high risk of cardiovascular complications such as stroke and myocardial infarction. Both JNC-VI and WHO-ISH 1999 specifically recommend a lower threshold for institution of blood pressure lowering treatment, and a lower target blood pressure for such treatment, in diabetics than in hypertensive patients without diabetes [52,53]; both recommend that drug treatment be initiated for diabetic subjects with blood pressure in the "high normal range" (systolic blood pressure 130-139mmHg and diastolic blood pressure 85-89mmHg) and both emphasise the need to normalise blood pressure in these subjects to levels below 130/85mmHg.

Number of strokes/ Favours total patients with diabetes more

More intensive Less intensive intensive

Favours

Insensive (95% CI)

Relative Risk

ABCD hypertensive ABCD normotensive HOT* UKPDS

9/237 4/237 12/499 38/758

9/233 13/243 17/501 34/390

0.98 (0.40-2.43) 0.30 (0.10-0.94) 0.70 (0.33-1.47) 0.56 (0.35-0.89)

Figure 4: Results of trials that compared blood pressure lowering strategies of different intensity and included participants with diabetes

Relative risks of fatal and non-fatal stroke among diabetic participants in trials that compared blood pressure lowering strategies of different intensities. The size of each box is proportional to the number of strokes that occurred and horizontal lines represent 95% confidence intervals. *For HOT, the risk of stroke in the most intensive group (target diastolic BP <80mmHg) is compared with that in the least intensive group (target <90mmHg) [49]. CI, confidence interval

As a result of these recommendations, one of the major challenges facing clinicians responsible for the care of diabetic patients will be to achieve adequate blood pressure control at a time when blood pressure is lowered to below 140/90mmHg in less than one quarter of the hypertensive population [54,55]. Given that the target blood pressure is even more stringent in the diabetic patient, it is clear that therapy with combinations of blood pressure lowering drugs will be needed in the majority of diabetic patients [49,50].

While there has been extensive debate about the merits of different classes of blood pressure lowering drug, there is now substantial evidence that any of five major classes of drug (diuretics, beta-blockers, ACE inhibitors, calcium antagonists and angiotensin receptor blockers) is effective in the primary prevention of stroke (i.e. the prevention of initial stroke) in hypertensive subjects. While there is less direct evidence in individuals with diabetes, with or without hypertension, the available evidence supports the use of each class of drug to lower blood pressure in such patients.

There is even less evidence that particular drug classes have specific advantages over one another in the primary prevention of stroke among diabetics. Randomised trials that have compared different classes of drug suggest that any differences are likely to be less important than lowering blood pressure with any effective agent rather than none. Furthermore, the evidence from comparative studies of blood pressure lowering drugs confirms that diuretics are at least as effective in preventing stroke as newer agents. This is likely to be confirmed in the next round of prospectively designed overview analyses conducted by the Blood Pressure Lowering Treatment Trialists' Collaboration [51], publication of which is anticipated in 2003. In the light of this evidence, and of their cost advantage over newer and more expensive drugs, it seems reasonable to recommend that diuretics should be included in any blood pressure lowering regimen in diabetic subjects, unless coexistent conditions in particular patients favour the use of other classes of drugs [52,53].

As documented in an ISH Statement on Blood Pressure Lowering and Stroke Prevention [56], recent evidence also confirms the value of reducing blood pressure for the prevention of recurrent stroke, though data are currently limited to diuretics and ACE inhibitors [23,25,26]. These studies demonstrated similar relative reductions in the risk of recurrent stroke in patients with and without hypertension, and in those with and without diabetes. There is currently little evidence regarding differential effects across drug classes and, once again, such differences as might exist are likely to be less important than the benefits conferred by any treatment compared with none [56].

Finally, while lifestyle measures for lowering blood pressure are beyond the scope of this chapter, it must be emphasised that attention to non-drug factors such as weight control, restriction of alcohol consumption, and adequate physical activity are even more important in diabetics than in hypertensive subjects without diabetes, and form an indispensable foundation for drug treatment.

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Reducing Blood Pressure Naturally

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