Should we take cerebral perfusion into consideration when treating hypertensive diabetics?

A tight blood pressure control is known to have beneficial impacts in patients with diabetes and hypertension. In patients with moderate hypertension, an antihypertensive treatment does not seem to have a negative influence on brain blood flow. Indeed, the cerebrovascular autoregulatory capacity (CA) of these patients remains intact notwithstanding a chronic elevation in blood pressure. So, cerebral vasculature of patients with moderate hypertension has the capacity to protect the brain from changes in blood pressure (an elevation in blood pressure could be associated with brain hyperperfusion if CA is altered and conversely, a reduction in blood pressure induced by antihypertenisve treatment, for example, could be associated with brain hypoperfusion if CA is impaired). Of interest, CA is affected in patients with severe hypertension, which leads to a reduction in brain blood flow with antihypertensive treatment.

Patients with diabetes have an impaired CA and the impact of an intensive control of blood pressure on cerebral perfusion in these patients was unknown…until a couple of months ago. In a study published recently *, researchers tested the hypothesis that intensive blood pressure control over a 6-month period has a negative influence on brain perfusion in hypertensive patients with diabetes and microvascular complications (microalbuminuria, retinopathy and/or sensorimotor neuropathy).

Patients with diabetes and microvascular complications were compared to patients with diabetes without microvascular complications and hypertensive patients paired for age, sex and ethnicity. Following baseline measurements, hypertension was treated using ACEi and diuretic or calcium channel blocking agent if targeted blood pressure was not reached with ACEi. The antihypertensive treatment lasted a period of 6 months and the targeted blood pressure was <130/80 mmHg for patients with diabetes and <140/90 mmHg for patients with hypertension. Cerebrovascular and cardiovascular responses were then evaluated after the treatment.

The authors reported that for a similar reduction in blood pressure in the 3 groups of patients following that 6-month antihypertensive treatment, cerebral perfusion (Vmean) was lower in diabetics with (black circle) vs. without microvascular complications (gray circle) and hypertensive patients (white circle). They also found that the degree of CA impairment observed in diabetics seemed associated with the presence of microvascular complications.

According to the authors, the reduction in cerebral perfusion in patients with diabetes and microvascular complications observed in response to this antihypertensive treatment could be partly explained by the jeopardized capacity of the cerebral vasculature of these patients to efficiently dampen sudden changes in blood pressure. The authors also suggest that for patients with vascular complications, blood pressure treatment should be individualized, aiming at obtaining a balance between the reduction in blood pressure and maintenance of cerebral perfusion. In fact, we should target an optimal blood pressure instead of the lowest possible blood pressure especially in diabetic patients with vascular complications.

Should we take cerebral perfusion into consideration when treating hypertensive diabetics ? I think so !

* Kim YS, Davis SC, Truijen J, Stok WJ, Secher NH, van Lieshout JJ. Intensive blood pressure control affects cerebral blood flow in type 2 diabetes mellitus patients. Hypertension 57(4):738-45, 2011

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