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Impaired microvascular flow motion in subclinical diabetic feet with sudomotor dysfunction.
Sun PC, Chen CS, Kuo CD, Lin HD, Chan RC, Kao MJ, Wei SH. Microvasc Res. 2012 Mar;83(2):243-8.
Impaired cutaneous blood flow and sweating dysfunction might be among the earliest manifestations of diabetic autonomic neuropathy. This study assessed the pathophysiological basis underlying skin vasomotion changes and their relation with progressive sudomotor dysfunction and other autonomic and somatic measures in subclinical diabetic feet. Laser Doppler skin perfusion was assessed on 68 diabetic and 25 control subjects. The low-frequency vasomotion was transformed into three frequency intervals 0.0095-0.021, 0.021-0.052 and 0.052-0.145 Hz, respectively, for the investigation of endothelial, neurogenic and myogenic effects on microcirculatory alterations. The diabetic patients were categorized into three groups by increasing severity of sudomotor dysfunction: SSR+ (sympathetic skin response present; 27 patients), SSR- (SSR absent; 23 patients) and at-risk (SSR absent and of preulcerative cracked skin; 18 patients). All diabetic patients underwent nerve conduction and cardiovascular autonomic studies. The total spectral and endothelial activity was significantly decreased only in the at-risk group. The SSR- group had lower neurogenic vasomotion than the SSR+ group (p<0.05). Although no statistical difference was noted between any group in absolute myogenic spectrum, the SSR- group had higher normalized myogenic activity than the SSR+ group (p<0.01). The larger drop in orthostatic pressure was paralleled by a reduction in the myogenic amplitude (r=-0.33, p<0.01). These results suggested that early impairment of low-frequency flow motion correlated closely with the presence of sudomotor dysfunction of subclinical feet mainly in neurogenic and endothelial components. Impaired systemic vascular tone as manifested by orthostatic hypotension was proportional to the degree of myogenic dysregulation in diabetic patients.
Radioisotope method with (99m)Tc pertechnetate is proposed for evaluation of the microcirculatory status of patients with the diabetic foot syndrome. The isotope (70-90 MBq) in 0.3-0.5 ml saline was injected subcutaneously into the interdigital spaces of the foot symmetrically on both sides. The severity of microcirculatory changes was evaluated by the rate of the radiopharmaceutical resorption using a computer-aided gamma counter. The data on the radiopharmaceutical half-resorption obtained by radioisotope study, serve as additional criteria for prediction of the disease course and choice of the treatment strategy for patients with the diabetic foot syndrome and diabetic gangrene of the lower limb.
The microcirculation—arterioles, venules, and capillaries—is critical for gas exchange, delivery of nutrients, and removal of waste products at the tissue level. Perfusion of the microcirculation is tightly controlled and highly regulated. Diabetes has a profound effect on the entire cardiovascular system and the microcirculation is particularly impacted. Diabetes induces basement membrane thickening impairing diffusion. Capillary perfusion is ultimately reduced producing local tissue ischemia despite normal pedal pulses. Diabetes disrupts the nerve–axon reflex, increases oxidative stress, and results in endothelial dysfunction. These effects of diabetes on the microcirculation have important clinical significance for practitioners caring for patients with diabetes. Understanding the effects of diabetes on the microcirculation impacts preventative care, diagnosis of the complications of diabetes, managing wounds, and ultimately has implications for the surgical treatment of complications of diabetes.