Reduced hyperaemia following skin trauma: evidence for an impaired microvascular response to injury in the diabetic foot

Diabetologia, Oct 1989

D. Walmsley, J. K. Wales, P. G. Wiles

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Reduced hyperaemia following skin trauma: evidence for an impaired microvascular response to injury in the diabetic foot

Diabetologia Reduced hyperaemia following skin trauma: evidence for an impaired microvascular response to injury in the diabetic foot D. Walmsley 0 1 J. K. Wales a n d P. G. Wiles 0 1 0 University Department of Medicine, The General Infirmary , Leeds , UK 1 Dr. D.Walmsley University Department of Medicine The General Infirmary Leeds LS1 3EX UK Summary.The hyperaemic response to standard needle injury within dorsal foot skin was investigated in normal and Type 1 (insulin-dependent) diabetic subjects using laser Doppler flowmetry. The normal response was maximal within 15 min, localised, prolonged and biphasic. In 20 normal subjects and three groups of long-duration Type1 diabetic patients (20 without complications; 20 with laser-treated retinopathy; 15 with neuropathy and retinopathy), the median (interquartile range) peak hyperaemic responses were 1.766 (1.220-1.970), 1.485 (1.342-1.672), 0.997 (0.705-1.203) and 1.030 (0.718-1.369) arbitrary units, respectively. Compared to normal and uncomplicated diabetic groups, peak flow was significantly reduced in the retinopathic (p< 0.0001) and neu- Injury; hyperaemia; laser Doppler flowmeter; Type 1 (insulin-dependent) diabetes mellitus; diabetic angiopathies - 9 Spfinger-Verlag 1989 T h e triple r e s p o n s e to a needle p r i c k injury to the skin consists o f a local n e u r o l o g i c a l l y - i n d e p e n d e n t vasodilatation, a m o r e w i d e s p r e a d but transient n e u r o g e n i c flare, a n d a weal [ 1 ]. T h e s e v a s c u l a r responses are integral parts o f n o r m a l healing a n d m a y b e i m p a i r e d in diabetic patients [ 2 ]. Recently, using laser D o p p l e r flowm e t r y [ 3, 4 ], diabetic patients h a v e b e e n f o u n d to h a v e a wide range o f a b n o r m a l m i c r o v a s c u l a r responses [ 5, 6 ], including r e d u c e d h y p e r a e m i a to needle t r a u m a in the a b d o m i n a l skin [ 7 ]. Thus, a generalised a b n o r m a l i t y o f v a s c u l a r r e s p o n s e to injury m a y b e present in diabetes, which could i m p a i r healing. T h e p r o b l e m o f p o o r w o u n d healing, infection [ 8 ] a n d ulceration is particularly centred on the feet o f diabetic patients [ 9 ]. T h e aims o f this study accordingly were: to characterise the h y p e r a e m i c r e s p o n s e to a s t a n d a r d needle injury in the skin o f the foot using laser D o p p l e r f l o w m e t r y ; to assess the local r e s p o n s e to m e c h a n i c a l injury in the feet o f patients with l o n g - t e r m T y p e 1 (insulin-dependent) diabetes; a n d to define the relationship o f i m p a i r m e n t in the r e s p o n s e to other m i c r o v a s c u l a r a n d n e u r o p a t h i c c o m p l i c a t i o n s o f diabetes. ropathic (p= 0.001 and 0.007, respectiwely) groups. There was no significant difference between the normal and uncomplicated diabetic groups, nor between the retinopathic and neuropathic groups. There was no association of the hyperaemic response with blood sugar, HbAlc, or duration of diabetes. Diabetic patients who have microvascul[ar complications, with or without neuropathy, have an associated impairment of microvascular response to mechanical injury which might predispose to infection and poor wound healing. Subjects and methods M e N o ~ After subjects had acclimatised lying supine in a constant temperature room at 24~ for 30 rain, relative cutaneous blood flow was measured by a PFld laser Doppler flowmeter (Perimed, Stockholm, Sweden) [ 3 ]. This non-invasive technique avoids many disadvantages of other methods [ 7 ]and has been validated using synchronous dynamic capillaroscopy [ 10 ]. However, the laser Doppler signal can be affected by factors such as skin thickness, pigmentation and vesselgeometry. Furthermore, blood flow in the sub-papillary plexus and arterio-venous anastomoses is measured as well as that in nutritional capillaries [ 11, 12 ]. Therefore, the laser probe was positioned on the dorsal foot, over the first two proximal metatarsal shafts, where there are no arteriovenous anastomoses [13]or callus. Thus, readings represent only capillary and subpapillary plexus flow. Other variables were limited,by recruitment criteria. Local skin temperature also influences cutaneous capillary blood flow independent of the sympathetic nervous system [ 14-17 ]. Therefore, local conductive heating with a thermostaticallycontrolled probe-holder (PF2b model) was used to maintain a standard skin temperature of 32-33~ measured by electronic thermometer (Comark, Rustington, W.Sussex, UK). This temperaturel is near the top of the normal range, below that required for rapid vasodilatation ([181and our unpublished observations) and does not interfere with neurovascular responses [191. o 1"6- Mean resting blood flow was calculated from a stable 2 min period, then standard needle trauma was produced using a 25 Gauge hypodermic needle centred on the axis of (...truncated)


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D. Walmsley, J. K. Wales, P. G. Wiles. Reduced hyperaemia following skin trauma: evidence for an impaired microvascular response to injury in the diabetic foot, Diabetologia, 1989, pp. 736-739, Volume 32, Issue 10, DOI: 10.1007/BF00274533