Evaluation of skin vasomotor reflexes in response to deep inspiration in diabetic patients by laser Doppler flowmetry. A new approach to the diagnosis of diabetic peripheral autonomic neuropathy

The peripheral vascular responses in non-freezing cold injury and matched controls

NEW FINDINGS

What is the central question of this study? Does non-freezing cold injury (NFCI) alter normal peripheral vascular function? What is the main finding and its importance? Individuals with NFCI were more cold sensitive (rewarmed more slowly and felt more discomfort) than controls. Vascular tests indicated that extremity endothelial function was preserved with NFCI and that sympathetic vasoconstrictor response might be reduced. The pathophysiology underpinning the cold sensitivity associated with NFCI thus remains to be identified.

ABSTRACT

The impact of non-freezing cold injury (NFCI) on peripheral vascular function was investigated. Individuals with NFCI (NFCI group) and closely matched controls with either similar (COLD group) or limited (CON group) previous cold exposure were compared (n = 16). Peripheral cutaneous vascular responses to deep inspiration (DI), occlusion (PORH), local cutaneous heating (LH) and iontophoresis of acetylcholine and sodium nitroprusside were investigated. The responses to a cold sensitivity test (CST) involving immersion of a foot in 15°C water for 2 min followed by spontaneous rewarming, and a foot cooling protocol (footplate cooled from 34°C to 15°C), were also examined. The vasoconstrictor response to DI was lower in NFCI compared to CON (toe: 73 (28)% vs. 91 (17)%; P = 0.003). The responses to PORH, LH and iontophoresis were not reduced compared to either COLD or CON. During the CST, toe skin temperature rewarmed more slowly in NFCI than COLD or CON (10 min: 27.4 (2.3)°C vs. 30.7 (3.7)°C and 31.7 (3.9)°C, P < 0.05, respectively); however, no differences were observed during the footplate cooling. NFCI were more cold-intolerant (P < 0.0001) and reported colder and more uncomfortable feet during the CST and footplate cooling than COLD and CON (P < 0.05). NFCI showed a decreased sensitivity to sympathetic vasoconstrictor activation than CON and greater cold sensitivity (CST) compared to COLD and CON. None of the other vascular function tests indicated endothelial dysfunction. However, NFCI perceived their extremities to be colder and more uncomfortable/painful than the controls.

Impaired dermal microvascular reactivity and implications for diabetic wound formation and healing: an evidence review

Diabetic foot ulcers (DFUs) are among the most consequential and costly complications faced by patients with diabetes and the global healthcare system. Acknowledged risk factors for DFUs include diabetic peripheral neuropathy (DPN), peripheral arterial disease (PAD), microtrauma and foot deformities. Research on additional risk factors for DFUs has recently focused on dysregulated, autonomic vasomotor control in the skin of patients with DPN. In particular, impaired dermal microvascular reactivity (IDMR) with its attendant reduction in nutritive capillary blood flow has been identified as an emerging risk factor. This especially relates to refractory wounds noted in patients without overt PAD signs. In this paper, evidence will be reviewed supporting the evolving understanding of IDMR and its impact on DFU formation and healing. Advances in diagnostic instrumentation driving this research along with the most promising potential therapies aimed at improving microvascular function in the diabetic foot will be discussed in brief.

A systematic evaluation of cutaneous microcirculation in the foot using post-occlusive reactive hyperemia

OBJECTIVES

Cutaneous microcirculatory impairments are associated with skin injury to the foot. Post-Occlusive reactive hyperemia (PORH) is one of the quick and easy methods to assess microcirculatory function. However, there are variations in the protocols currently used. Hence, this study aimed to systematically investigate the reproducibility of PORH protocols with minimal occlusion time in the foot.

METHODS

Post-Occlusive reactive hyperemia was measured using 12 different protocols (three occlusion times, two occlusion sites and with or without temperature control) in 25 healthy adults. Each of the 12 different protocols was repeated three times, and the intraclass correlation coefficient (ICC) was calculated.

RESULTS

Intraclass correlation coefficient showed that that ankle level occlusion produced moderate to excellent reproducibility for most PORH measures. In the right foot, 30- and 60-s ankle level occlusion without temperature control showed ICC of >0.40 for all parameters except the area of hyperemia (ICC = -0.36) and biological zero to peak flow percent change (ICC = -0.46). In the left foot, 30-s ankle level occlusion without temperature control showed ICC of >0.40 for all parameters except time to latency (ICC = 0.29), after hyperemia (ICC = 0.37), and max (ICC = -0.01), and area of hyperemia (ICC = -0.36). But the 60-s protocol showed ICC > 0.40 for all except time to max (ICC = 0.38). In the hallux protocols, all three 10-, 30-, and 60-s protocols without temperature control showed moderate to excellent reproducibility (ICC > 0.40). In most cases, the temporal and area under the perfusion-time curve parameters showed poor reproducibility.

CONCLUSION

Post-Occlusive reactive hyperemia can be tested efficiently with a minimal occlusion time of 10 s with hallux occlusion and 30 s with ankle occlusion in the foot. This can suggest that microcirculatory assessment is feasible in routine practice and can potentially be included for routine assessment of foot in people with diabetes.

A Real-Time Blood Flow Measurement Device for Patients with Peripheral Artery Disease

PURPOSE

To evaluate the feasibility of a new optical device that measures peripheral blood flow as a diagnostic and monitoring tool for patients with peripheral artery disease (PAD).

MATERIALS AND METHODS

In this prospective study, 167 limbs of 90 patients (mean age, 76 y; 53% men) with suspected PAD were evaluated with the FlowMet device, which uses a new type of dynamic light-scattering technology to assess blood flow in real time. Measurements of magnitude and phasicity of blood flow were combined into a single-value flow-waveform score and compared vs ankle-brachial index (ABI), toe-brachial index (TBI), and clinical presentation of patients per Rutherford category (RC). Receiver operating characteristic curves were constructed to predict RC. Area under the curve (AUC), sensitivity, and specificity were compared among flow-waveform score, ABI, and TBI.

RESULTS

Qualitatively, the FlowMet waveforms were analogous to Doppler velocity measurements, and degradation of waveform phasicity and amplitude were observed with increasing PAD severity. Quantitatively, the flow, waveform, and composite flow-waveform scores decreased significantly with decreasing TBI. In predicting RC ≥ 4, the flow-waveform score (AUC = 0.83) showed a linear decrease with worsening patient symptoms and power comparable to that of TBI (AUC = 0.82) and better than that of ABI (AUC = 0.71). Optimal sensitivity and specificity pairs were found to be 56%/83%, 72%/81%, and 89%/74% for ABI, TBI, and flow-waveform score, respectively.

CONCLUSIONS

The technology tested in this pilot study showed a high predictive value for diagnosis of critical limb ischemia. The device showed promise as a diagnostic tool capable of providing clinical feedback in real time.

Prospects of Laser Doppler flowmetry application in assessment of skin microcirculation in diabetes

This review includes results of scientific and clinical use of laser Doppler flowmetry (LDF) in patients with diabetes mellitus. LDF is a non-invasive method for the quantitative evaluation of microcirculation, which can assess microcirculatory rhythms and conduct functional tests with various impacts, allowing the exploration of regulatory mechanisms of microcirculation. LDF reveals specific diabetes changes in the regulatory function of microcirculation. Microcirculation disturbances, which are traditionally associated with the pathogenesis of complications, also occur in patients with early disorders of carbohydrate metabolism and may precede the manifestation of diabetes. However, this method is still not applied in clinical practice. In this review, we analysed factors limiting the implementation of LDF in practical medicine and suggest ways to improve its clinical significance.

The Effect of Different Physiological Stimuli on Skin Vasomotor Reflexes above and below the Lesion in Human Chronic Spinal Cord Injury

Objective. Spinal cord injury (SCI) results in disruption of descending tonic activation of sympathetic circuits in the spinal cord. The authors determined whether different stimuli that increase sympathetic activity induced cutaneous vasoconstriction (skin vasomotor reflex, SkVR) above and below the level of lesion in subjects with clinically complete SCI. Methods. Baseline skin blood flow (SkBF) and SkVR reduction rate in the pulp of the finger and great toe was measured by laser Doppler probes in chronic complete SCI and in controls. Results. In the finger, baseline SkBF was similar in SCI and controls. The SkVR was elicited by all stimuli in controls but was significantly diminished to gasp, mental arithmetic, tactile stimulation, cutaneous cold, and deep breathing in high SCI compared to controls. In the toe, baseline SkBF was less stable in both controls and SCI. SkVR trends were identified in controls, and responses were not present or greatly reduced in high and low SCI. Conclusions. Measurements of skin vasomotor reflexes to physiological stimuli may be a noninvasive method to evaluate the extent of sympathetic adrenergic pathways in chronic SCI. This is of clinical relevance in monitoring recovery of sympathetic adrenergic function either spontaneously or following repair interventions.

Barriers to the management of Diabetes Mellitus - is there a future role for Laser Doppler Flowmetry?

Diabetes Mellitus (DM) is a chronic disease that carries a significant disease burden in Australia and worldwide. The aim of this paper is to identify current barriers in the management of diabetes, ascertain whether there is a benefit from early detection and determine whether LDF has the potential to reduce the disease burden of DM by reviewing the literature relating to its current uses and development. In this literature review search terms included; laser Doppler flowmetry, diabetes mellitus, barriers to management, uses, future, applications, vasomotion, subcutaneous, cost. Databases used included Google Scholar, Scopus, Science Direct and Medline. Publications from the Australian government and textbooks were also utilised. Articles reviewed had access to the full text and were in English.

Comparison of laser speckle contrast imaging with laser Doppler for assessing microvascular function

OBJECTIVE

To compare the inter-day reproducibility of post-occlusive reactive hyperaemia (PORH) and sympathetic vasomotor reflexes assessed by single-point laser Doppler flowmetry (SP-LDF), integrating-probe LDF (IP-LDF) and laser speckle contrast imaging (LSCI), and the spatial variability of PORH assessed by IP-LDF and LSCI. We also evaluated the relationship between IP-LDF and LSCI perfusion values across a broad range of skin blood flows.

METHODS

Eighteen healthy adults (50% male, age 27 ± 4 years) participated in this study. Using SP-LDF, IP-LDF and LSCI, indices of skin blood flow were measured on the forearm during PORH (1-, 5- and 10-min occlusions) and on the finger pad during inspiratory gasp and cold pressor tests. These tests were repeated 3-7 days later. Data were converted to cutaneous vascular conductance (CVC; laser Doppler flow/mean arterial pressure) and expressed as absolute and relative changes from pre-stimulus CVC (ΔCVC(ABS) and ΔCVC(REL), respectively), as well as normalised to peak CVC for the PORH tests. Reproducibility was expressed as within-subjects coefficients of variation (CV, in %) and intraclass correlation coefficients.

RESULTS

The reproducibility of PORH on the forearm was poorer when assessed with SP-LDF and IP-LDF compared to LSCI (e.g., CV for 5-min PORH ΔCVC(ABS)=35%, 27% and 19%, respectively), with no superior method of data expression. In contrast, the reproducibility of the inspiratory gasp and cold pressor test responses on the finger pad were better with SP-LDF and IP-LDF compared to LSCI (e.g., CV for inspiratory gasp ΔCVC(REL)=13%, 7% and 19%, respectively). The spatial variability of PORH responses was poorer with IP-LDF compared to LSCI (e.g., CV ranging 11-35% versus 3-16%, respectively). The association between simultaneous LSCI and IP-LDF perfusion values was non-linear.

CONCLUSION

The reproducibility of cutaneous PORH was better when assessed with LSCI compared to SP-LDF and IP-LDF; probably due to measuring larger skin areas (lower inter-site variability). However, when measuring sympathetic vasomotor reflexes on the finger pad, reproducibility was better with SP-LDF and IP-LDF, perhaps due to the high sensitivity of LSCI to changes in skin blood flow at low levels.

New finger-occlusion plethysmograph for estimating peripheral blood flow and vascular resistance

BACKGROUND

The aim of the present study was to measure peripheral blood flow (BF) with a new finger-occlusion plethysmograph (FOP) and to compare this to BF measured with a laser Doppler flowmeter (LDF). An additional objective was to investigate the relationship between hypertension-related clinical parameters and peripheral vascular resistance (PVR) estimated from BF and mean blood pressure (BP) (PVR=mean BP/BF) in young subjects.

METHODS AND RESULTS

The present study employed 101 young volunteers (61 males, 40 females, mean age 23.2+/-2.5 years). The FOP was attached to the third finger and an LDF to the fourth fingertip of each subject. BF was measured simultaneously by the 2 devices. A multi-biomedical recorder (TM2425) measured 24-h BP. A high correlation was observed between BF measured by the FOP and LDF (r=0.79, p<0.001). In multiple linear regression analysis, PVR was independently correlated with a family history of hypertension (p<0.01) and with base diastolic BP during sleep (p<0.01), which is a sensitive predictor of severity of hypertension.

CONCLUSIONS

Our newly developed FOP can estimate peripheral absolute BF easily. Furthermore, BF determined by the FOP can be used to calculate PVR, and an elevated PVR may be a useful predictor of hypertension.

Measurements of sweat response and skin vasomotor reflex for assessment of autonomic dysfunction in patients with diabetes

AIMS

Some physical or arousal stimuli induce a rise in sweat secretion (sympathetic sweat response or SSwR) and a reduction in skin blood flow (skin vasomotor reflex or SkVR) to the palm. We recorded SSwRs and SkVRs in diabetic patients and assessed the usefulness of these parameters for evaluating autonomic dysfunction in diabetes.

METHODS

We studied 42 diabetic patients (58+/-12 years) and 42 normal control subjects (59+/-11 years). Focal sweat secretion and skin blood flow were measured on the palm by a sudorometer and a Doppler flowmeter, respectively. SSwRs and SkVRs to deep inspiration, mental arithmetic, and isotonic exercise were recorded. SSwR amplitude was measured from baseline to peak, and SkVR amplitude (reduction rate) was calculated as: (blood flow reduction/basal blood flow)x100%. We also conducted head-up tilt tests and R-R interval variation tests (coefficient of variation of R-R intervals or CV(R-R)).

RESULTS

The SSwR or SkVR amplitudes in the diabetic group were significantly lower than those in the control group for any stimulus. CV(R-R) in the diabetic group was significantly less than that in the control group. The diabetic group showed a significantly greater reduction in systolic blood pressure during head-up tilt compared with the control group. In the diabetic group, there were significant correlations in SSwR or SkVR amplitudes versus blood pressure falls during the head-up tilt test, and CV(R-R) values.

CONCLUSION

We believe that SSwR and SkVR are useful indexes for the evaluation of autonomic involvement in diabetic patients.

Non-invasive methods and stimuli for evaluating the skin's microcirculation

Vessels in the skin are arranged into superficial and deep horizontal plexuses and they are involved in thermoregulation, oxygen and nutritional support. The skin has a large number of functions and broad appeal spanning basic mechanistic and clinical research. Indeed, the skin can be used as a marker of normal and impaired vascular control and, owing to its accessibility and frequent involvement, is easy to investigate non-invasively. A large number of non-invasive methods are available for investigating the skin, ranging from those that permit the visualisation of microvessels, to those that monitor blood flow or one of its derivatives (e.g., skin temperature and transcutaneous oxygen). Such methods can be combined with non-invasive, dynamic stimuli (e.g., the use of cold or warm stimuli, activation of the peripheral nervous system or local neuronal systems, and the topical application of vasoactive drugs) and this potentially enables the differentiation of underlying disorders (e.g., primary from secondary Raynaud's phenomenon) and also to quantify changes over time or following intervention. The present article outlines the non-invasive methods and dynamic tests that can be used to investigate the microcirculation of the skin.

Reflex vasoconstrictor responses of the healthy human fingertip skin. Normal range, repeatability, and influencing factors

Skin vasoconstrictor reflexes (SVCRs) are mediated by sympathetic vasoconstrictor nerve fibers and used to test sympathetic function of the extremities. Since there is a dearth of published systematic data on inspiratory gasp-induced SVCR, we studied its range, repeatability, and influencing factors in 64 healthy subjects (mean age 41.9 years, range 20-78 years, 32 males). Mean vasoconstriction for the second digit was 54% (+/-19)/54% (+/-19) (right/left) and 69% (+/-16)/68% (+/-15) for the fourth digit. Forth digit vasoconstriction was significantly larger than the second digit (P < 0.01), but second and fourth digit correlation was good (Pearson: 0.521-0.741). Repeatability using single measure intraclass correlation was good with 0.62/0.69 for the second digit and 0.64/0.80 for the fourth digit (right/left). A trend for decreasing SVCR was seen with increasing age and weight, no effect was seen for gender, height, or blood pressure. The SVCR repeatability and range of variation seen in this study compare favorably with tests of heart rate variability, thermal threshold detection, and motor nerve conduction.

Relationship of inspiratory flow rate and volume on digit tip skin and ulnar artery vasoconstrictor responses in healthy adults

Reflex vasoconstrictive responses are commonly used to assess sympathetic nerve function of the extremities. A regularly used reflex trigger is deep and rapid inspiration. However, little is known about the relationship between respiratory effort and the magnitude of the resultant vasoconstrictor response. This study investigates the association of inspiratory flow rate and volume to the level of vasoconstrictor reflexes in the 4th digit tip skin and the ulnar artery in 12 healthy volunteers (age range 21-65, mean 38.1 years). The effects of Peak Inspiratory Flow (PIF) and Forced Inspiratory Vital Capacity (FIVC) on blood flow were measured at three levels of respiratory effort: low (PIF < 1.0 l/min; FIVC < 1.0 l), medium (PIF = 1.0-1.5 l/min; FIVC = 1.0-1.5 l), and high (PIF > 1.5 l/min; FIVC > 1.5 l) at two separate occasions. Ulnar vasoconstrictor responses showed good correlation with all levels of respiratory effort. Skin digit tip responses showed good correlation at medium and high levels but not at low respiratory effort. Repeatability of both tests was good. Correlation of inspiratory flow rate to vasoconstriction was consistently better than with inspiratory volume. Both digit tip and ulnar vasoconstrictor responses were maximal with greatest respiratory effort.

Relationship between sympathetic skin response and power spectral analysis of heart rate variation in patients with type 2 diabetes

We measured sympathetic skin response (SSR), a measure of sympathetic sudomotor function, and compared SSR with other quantitative neurological tests including power spectral analysis (PSA) of heart rate variations in 60 type 2 diabetic subjects. SSR was detected in all 20 age-matched healthy subjects but was absent in 17 patients with type 2 diabetes (28%) (P<.01). Even after exclusion of diabetic patients with absent SSR, the SSR amplitude in diabetic patients was significantly lower than in healthy subjects (P<.05). Both the low frequency power of R-R intervals, which reflects both cardiac sympathetic and parasympathetic function, and the postural fall in systolic blood pressure were significantly lower in the diabetic patients with absent SSR than in those with present SSR (P<.05 and.001, respectively). However, we found no significant difference in the high frequency power of R-R intervals, which reflects accurately cardiac parasympathetic function, between the diabetic patients with absent SSR and those with present SSR. In the diabetic patients with present SSR, SSR amplitude was also positively correlated with the postural fall in systolic blood pressure, low-frequency (LF) power, and high-frequency (HF) power. These results suggest that SSR is a useful and sensitive method for evaluating diabetic autonomic neuropathy, and that sympathetic sudomotor neuropathy may be preceded by cardiac parasympathetic neuropathy in patients with type 2 diabetes.

Relationship between sympathetic reactivity and body weight loss in morbidly obese subjects

OBJECTIVE

To investigate the possible role of peripheral sympathetic activity in gastric bypass-induced body weight loss.

SUBJECTS AND METHODS

In 42 morbidly obese patients (sex: 36 f/6 m; BMI: 46.0+/-0.7 kg/m(2)) undergoing a gastric bypass, the skin vasoconstrictor reflex in answer to a deep inspiration was measured by laser Doppler fluximetry. The extent of vasoconstriction, measured at the second finger of the left hand, was expressed as percent reduction of the basal blood flux (% vasoconstriction). Insulin sensitivity was assessed before surgery in a subset of patients (n=11), by the method of euglycemic, hyperinsulinemic clamp. Body weight and composition were evaluated before, and 3, 6 and 12 months after surgery. At the same time points, energy intake (kJ/day) was evaluated by means of both food record diary and alimentary anamnesis.

RESULTS

The % vasoconstriction, which was significantly (P=0.01) greater in normoglycemic subjects than in diabetic ones, was also significantly (P=0.03) related to the extent of insulin sensitivity measured during the euglycemic clamp. The % vasoconstriction showed a significant (P>0.0001), positive correlation with weight reduction obtained between the 6th and 12th months following surgery; as a consequence, % vasoconstriction was significantly (P=0.0004) related to the overall body weight loss achieved during the year following the operation. These correlations remained significant in multiple regression analysis with adjustment for age, initial body weight, plasma glucose and insulin (P=0.0007 and 0.006, respectively). The % vasoconstriction was also significantly (P=0.0006), negatively related to energy intake measured 12 months after surgery.

CONCLUSIONS

In conditions of stable body weight, the sympathetic nervous system (SNS) reactivity is influenced by the degree of insulin resistance. A high capacity to activate the SNS, measured before surgery, is associated with both a larger gastric bypass-induced weight loss and a lower energy intake, at the phase of weight stabilization.

Brachial-Ankle Pulse Wave Velocity Is Useful for Evaluation of Complications in Type 2 Diabetic Patients

Pulse wave velocity (PWV) is useful for the evaluation of aortic stiffness. The brachial-ankle PWV (baPWV) and carotid PWV (from heart to carotid) were compared to study the relation of these two types of PWVs to diabetic complications in patients with type 2 diabetes mellitus. The baPWV was determined by oscillometrically measuring the pulse volume record at the upper arm and ankles. The carotid PWV was measured tonometrically. Ninety patients with type 2 diabetes mellitus were divided into tertile groups on the basis of baPWV or carotid PWV. The correlations of these variables with albuminuria, peripheral neuropathy, coefficient of variation of R-R intervals (CV R-R) on the electrocardiogram at rest, and retinopathy were examined by logistic regression analysis. After adjustment for age, systolic blood pressure, and duration of diabetes, logistic regression analysis showed that baPWV was directly related to the frequencies of albuminuria, decreased CV R-R, peripheral neuropathy, and retinopathy. In contrast, carotid PWV did not significantly correlate with any diabetic complications. We conclude that oscillometrically determined baPWV is related to the risk of diabetic microvascular disease in patients with type 2 diabetes mellitus and suggested to be useful for assessing risk factors of diabetic complications.

Sympathetic mediated vasomotion and skin capillary permeability in diabetic patients with peripheral neuropathy

AIMS/HYPOTHESIS

A loss of sympathetic function could lead to changes in capillary fluid filtration in diabetic patients. We investigated whether a decreased sympathetically mediated vasomotion in the skin in diabetic patients with peripheral neuropathy is associated with an abnormal capillary leakage.

METHODS

Three matched groups were studied: 18 diabetic patients with documented peripheral neuropathy (DN), 18 diabetic patients without peripheral neuropathy (D), and 18 healthy control subjects (C). Sensory and motor nerve function of the distal extremities were assessed by standard neurography, and expressed in a sensory-motor nerve function score. Sympathetic vasomotion of the skin microcirculation was assessed by determining the power of blood flow variability in the low-frequency (0.02-0.14 Hz) band by spectral analysis of laser Doppler flowmetry at the median ankle. Skin capillary leakage was evaluated by sodium fluorescein videodensitometry at the same site of the foot.

RESULTS

Sympathetically mediated vasomotion of the foot skin microcirculation was lower in diabetic patients with documented peripheral neuropathy compared with diabetic patients without peripheral neuropathy and control subjects (p<0.001). Capillary sodium fluorescein leakage was larger in 18 diabetic patients with documented peripheral neuropathy than in diabetic patients without peripheral neuropathy (p<0.02) and C (p<0.005). Multiple regression analysis disclosed that a reduced sympathetically mediated vasomotion, together with a lower sensory-motor nerve function score, independently contributed to the variance in sodium fluorescein leakage, for 30% (p<0.001) and 17% (p<0.01), respectively.

CONCLUSIONS

A loss of sympathetic tone, apart from sensory-motor nerve dysfunction, seems to be a major determinant of an increased capillary permeability in diabetic patients with neuropathy.

Early decrease of skin blood flow in response to locally applied pressure in diabetic subjects

Pressure ulcers are common debilitating complications of diabetes that are caused by tissue ischemia. Skin blood flow in response to locally applied pressure might be impaired in diabetic patients because of the combined effects of a typically low skin temperature and alterations in microcirculatory function, and could be worsened by neuropathy. We measured skin blood flow by laser Doppler flowmetry over the internal anklebone in response to local pressure applied at 5.0 mmHg/min in three groups of diabetic patients (with clinical and subclinical neuropathy and without neuropathy) and in healthy matched control subjects at usual room temperature. Compared with in matched control subjects with comparable skin temperatures (29.3 +/- 0.4 vs. 28.7 +/- 0.4 degrees C), in diabetic patients the skin blood flow response to locally applied pressure was further impeded, even in those without neuropathy. Indeed, skin blood flow decreased significantly from baseline at much lower applied pressure (7.5 mmHg) in diabetic subjects, again even in those without neuropathy, than in control subjects (48.8 mmHg). The large difference between these pressures could partially explain diabetic patients' high risk of developing decubitus and plantar ulcers.

Elevation of von Willebrand factor in plasma in diabetic patients with neuropathic foot ulceration

AIMS

The present study examines the relationship between markers of endothelial dysfunction and diabetic neuropathy or consequent neuropathic foot ulceration in patients with Type 2 diabetes mellitus.

METHODS

We studied 65 Type 2 diabetic patients including 25 diabetic patients without neuropathy, 27 with neuropathy but no history of foot ulceration, and 13 with neuropathic ulceration. Plasma concentrations of von Willebrand factor (vWF) and soluble thrombomodulin (TM), measures of endothelial dysfunction, were determined by enzyme immunoassays. We performed various tests quantifying aspects of diabetic neuropathy including vibration perception threshold (VPT; for sensory neuropathy), coefficient of variation of R-R intervals (CVR-R; for cardiac autonomic neuropathy), and cold-induced vasodilation in the great toe for peripheral sympathetic neuropathy.

RESULTS

CVR-R and cold-induced vasodilation were significantly diminished in patients with neuropathic foot ulceration compared with patients with neuropathy but no history of foot ulceration. Plasma vWF concentrations were positively correlated with VPT and cold-induced vasodilation test, and were inversely correlated with CVR-R. Multivariate analysis disclosed that VPT and percentage vasodilation were independent factors for plasma vWF. Plasma vWF was significantly elevated in patients with foot ulceration compared with patients without neuropathy or those with neuropathy but not foot ulceration. However, plasma TM concentrations did not differ between the three groups.

CONCLUSIONS

Diabetic patients with neuropathic foot ulceration had severe impairment of cardiac autonomic and peripheral sympathetic nerves. Elevation of vWF in plasma was associated with neuropathic foot ulceration, linking endothelial dysfunction to foot ulceration.

Autonomic nervous function assessment using thermal reactivity of microcirculation

There are only a few reliable objective methods of diagnosing peripheral neuronal damage suitable for routine use; the most important is based on measurement of nerve conduction velocity, which only shows changes when severe disturbances are already present. However, it is precisely at this stage that the possibilities of therapy are no longer satisfactory. As small fibres are affected earlier in the course of most forms of PNP than the large ones, assessment of afferent as well as efferent C-fibre function gains importance in the management of this widespread disease. In assessment of autonomic dysfunction, variability of the heartbeat with deep breathing or the Valsalva manoeuvre is a good and generally accepted test, although not strongly associated with other PNP test abnormalities. However, axonal degeneration starts in the most distal parts of the axon due to impaired axonal transport. Therefore, the longest C-fibres, i.e. in the lower extremities, are affected first, and incipient changes are most prominent there. For this reason HLDF, a reflex response of the skin blood flow stimulated by heat, has advantages in assessment of early C-fibre dysfunction. Considering the fact that the afferent and efferent sympathetic C-fibres are involved in regulation of microcirculation, the skin blood flow regulation is investigated by means of laser Doppler flowmetry. The microcirculation is stimulated by heat and the reaction of microcirculation is assessed as a value for the function of afferent and efferent (sympathetic) C-fibres. The results of this method are in close correlation with electrophysiologic tests, which is not achieved with sudomotor function.

Evaluation of gut motility in type II diabetes by the radiopaque marker method

BACKGROUND

The clinical usefulness of the radiopaque marker method for detecting diabetic gastrointestinal motility disturbances, was evaluated by examining 21 type II diabetes subjects who did not have any neuropathic symptoms.

METHODS

After administration of a Sitzmark capsule, markers were located using plain abdominal radiographs, and the transit time of the markers through seven areas of digestive tract was calculated by Arhan's methods. The plasma concentration of acetaminophen at 45 min after oral administration was measured to evaluate gastric emptying time. The coefficient of variation of R-R intervals on the electrocardiograms (CV(R-R)) was measured to evaluate parasympathetic autonomic function.

RESULTS

In the diabetics, the average (+/- SD) transit time through upper digestive tracts was slightly but not significantly elongated compared with control subjects (14.4 +/- 8.3 vs 9.9 +/- 6.1 h). Significant elongation was observed in transit time through the lower digestive tracts or the whole gut (44.6 +/- 20.9 and 57.9 +/- 22.3 h, respectively) compared with control subjects (23.3 +/- 8.5 and 33.2 +/- 11.0 h). The transit time of the markers from stomach to small intestine was highly correlated (r = 0.693) with plasma concentration of acetaminophen. The transit time through either the whole colon (r = 0.564) or the whole gut (r = 0.630) was highly correlated with CV(R-R).

CONCLUSIONS

These findings suggest that the radiopaque marker method is a useful tool for detecting the sections of the digestive tract responsible for gut motility disturbances. In type II diabetics with no neuropathic symptoms, the lower digestive tracts may deteriorate prior to the impairment of upper digestive tracts.