Predictors of impaired blood pressure homeostasis during acute and sustained orthostasis in patients with type 2 diabetes

Abstract

Aim: Sympathetic failure with acute postural hypotension is a common feature of advanced autonomic neuropathy in type 2 diabetes. It is unknown, however, whether: a) the presence of sympathetic autonomic neuropathy is also a powerful predictor of postural blood pressure changes during sustained orthostasis and b) other factors affecting baroreceptor and neuro-hormonal control might play a role.

Methods: Systolic blood pressure (SBP) was measured during supine rest and after 2, 5, and 20 min of active orthostasis in 45 males with type 2 diabetes (age 56.4+/-8.2 years, mean+/-SD) and different degrees of autonomic neuropathy (absence of neuropathy, n=26, parasympathetic neuropathy, n=9, and sympathetic neuropathy, n=10). Eight healthy subjects (50.1+/-11.6 years) served as controls. A multiple backward regression analysis was performed to identify independent predictors of SBP changes during orthostasis. The regression model included presence/absence of sympathetic autonomic neuropathy, age, diabetes duration, presence/absence of hypertension, baseline SBP and neuro-hormonal parameters (plasma adrenaline, noradrenaline, plasma renin activity, and aldosterone).

Results: Sympathetic autonomic neuropathy (P=0.005), baseline SBP (P=0.001), and adrenaline (P=0.003) independently predicted SBP changes after 2 min (R2=0.64); sympathetic autonomic neuropathy (P<0.001), baseline adrenaline (P=0.008), and plasma renin activity (P=0.006) predicted SBP changes after 5 min (R2=0.58); whereas sympathetic autonomic neuropathy (P<0.001) and baseline SBP (P<0.001) predicted SBP changes after 20 min orthostasis (R2=0.65).

Conclusions: The presence of sympathetic autonomic neuropathy and higher supine SBP values remain strong and independent predictors of SBP fall not only during the acute transition from supine to standing position but also during sustained orthostasis in type 2 diabetes. Lower baseline plasma adrenaline concentrations and plasma renin activity are also involved, though to a lesser extent, in the genesis of this haemodynamic response.