Blood flow patterns in painful diabetic neuropathy

Abstract

Summary.Peripheral blood flow is known to be qualitatively increased in diabetic patients with neuropathy. We have measured the actual blood flow in the feet of diabetic patients with neuropathy using non-invasive mercury strain gauge plethysmography and Doppler sonogram techniques and shown that it is increased on average five times above normal at an ambient temperature of 20 ~ -22 ~ Moreover, reduction of this high flow by sympathetic arousal stimuli proved possible in those with severe painful neuropathy contrasting strongly with failure to reverse it in those with severe non-painful sensory neuropathy. Reduction of blood flow was associated with reduction in neuropathic pain. We studied 22 diabetic patients with severe sensory neuropathy and eight with painful neuropathy. High resting foot blood flows were demonstrated in both groups with neuropathy. The big toe flow in those with severe sensory neuropathy was 29.3 + 9.2 ml. rain-1. 100m1-1 (mean+-SD) and in the painful neuropathy group, 25.9+_7.5, compared with 5.2+2.4ml.min -1. 100m1-1 in the non-diabetic control subjects (p<0.001). High foot skin temperatures were also recorded in the groups with neuropathy, reflecting the high blood flow. The subjects with painful neuropathy retained the ability to constrict peripheral blood vessels in response to arousal stimuli, and reduce peripheral flow on average by 32% compared with the patients with sensory neuropathy who responded on average by only 10%. The demonstration of a peripheral sympathetic defect, responsible for the high blood flow and the potential reversal of such flow in painful neuropathy may be important in our further understanding of the aetiology of such pain and its treatment.Key words: Diabetes mellitus, peripheral blood flow, sensory neuropathy, painful neuropathy, peripheral sympathetic neuropathy.During the nineteenth century, the feet of diabetic patients with peripheral neuropathy were observed to be hot and erythematous [1] and the blood flow in such feet was considered to be increased. This increase is now thought to be due to the dilation of denervated arteriovenous shunts [2-9] normally controlled by sympathetic nerves.Measurement of actual blood flow in diabetic neuropathic feet has only been undertaken in one previous study [10]. Blood flow was not found to be increased in neuropathic subjects probably because the studies were conducted by waterbath plethysmography at 32~ causing vasodilatation and increased flow in the control subjects.The aim of this study was to measure the magnitude of resting foot blood flow in a group of diabetic patients with severe sensory neuropathy and to discover whether the hot, burning foot, so characteristic of distal painful neuropathy, also has a high resting flow resulting from a peripheral sympathetic defect. In addition, the sympathetic responses of both types of neuropathy were tested to discover whether either retained the ability to reduce peripheral flow by vasoconstriction, and whether any benefits might result from this. Subjects and metho...

Increased sural nerve epineurial blood flow in human subjects with painful diabetic neuropathy

“…Further evidence to support the assertion that increased blood flow is relevant to the cause of pain is gained from the observation that painful symptoms might improve with maneouvres that reduce blood flow to the limb [16]. In the process of studying blood flow in neuropathy, it was observed that, on inflation of a sphygmomanometer cuff to measure blood flow in the limb, subjects with painful neuropathy often reported that symptoms improved in that limb.…”

“…The fluctuant nature of painful neuropathic symptoms might suggest a more dynamic underlying cause, such as metabolic or haemodynamic factors, rather than structural lesions. Furthermore, it is recognized that manoeuvres that reduce lower limb blood flow, including vessel occlusion and cooling of the limb, can reduce painful neuropathic symptoms [16]. The aim of this study was to compare sural nerve epineurial haemodynamics in subjects with chronic painful and painless DSP.…”

Streptozotocin-induced diabetes differentially affects sympathetic innervation and control of plantar metatarsal and mesenteric arteries in the rat

“…These studies have demonstrated that both type 1 (insulin dependent) and type 2 (noninsulin dependent) diabetic patients with signs of sensory and/or autonomic neuropathy (e.g., orthostatic hypertension) have increased skin blood flow under basal conditions (2,33) and attenuated reductions in skin blood flow (i.e., vasoconstriction) in response to sympathetic arousal [e.g., produced by mental arithmetic (2) or postural stimuli (29)]. Importantly, deficits in sympathetic vasoconstriction of arterial vessels supplying plantar skin can be demonstrated in both type 1 and type 2 diabetic patients at an early phase of diabetic neuropathy (31,35), perhaps suggesting that sympathetic neurons supplying these vessels are particularly vulnerable to the effects of diabetes.…”

Impaired Skin Microvascular Reactivity in Painful Diabetic Neuropathy

“…Many years ago, Archer et al (6) showed that diabetic patients with PDN have altered blood flow patterns in the lower limbs. More recently, we found an increase in sural nerve epineurial blood flow in patients with PDN (7).…”