Dynamics of skin blood flow in human sepsis

Objective The study was undertaken to determine if sepsis alters the pattern of vasomotion and reactive hyperaemia in the skin.Design This was a prospective, observational study.Setting: The study was performed in the medical and surgical intensive care units of a tertiary referral hospital.Patients and participants 11 patients with sepsis (using Bone's criteria [1]), were compared with 19 patients recovering from coronary artery bypass grafting who were used as non-septic controls. Nineteen normal volunteers were also studied.Measurements and results Skin blood flow was measured on the forearm using laser Doppler flowmetry at rest and after 2 min arterial occlusion with a tourniquet. The resting blood signal was analyzed by calculating the mean skin blood flow, the power of the skin blood flow signal (variance) and the power spectrum. The rate of recovery after arterial occlusion was determined by calculating the peak increase in skin blood flow and the time constant of the decay of skin hyperaemia back to baseline flow. Patients with sepsis had a mean skin blood flow of 6.24 (3.48) ml min^–1 per 100 g tissue compared with 4.35 (1.41) ml min^–1 per 100 g tissue for the patients after coronary artery bypass grafting (p<0.05). The septic patients also showed a marked increase in the fraction of total power in the 0.1–0.15 Hz frequency band (0.19 (0.17) versus 0.068 (0.033),p<0.05), a decreased peak hyperaemic response (40 (23)% increase in flow above baseline after cuff release versus 147 (19)% and a prolonged time constant for recovery from hyperaemia (22.8 (12.7) versus 11.7 (8.5) seconds,p<0.05). These results imply an increased local rather than central control of skin blood flow.Conclusion The laser Doppler flowmeter allows local rather than global haemodynamics to be studied. Abnormalities of skin blood flow control are found in sepsis, and this technique may prove useful to monitor the effects of treatment, especially if the use of laser Doppler flowmetry can be extended to other organs at risk of damage during sepsis such as gastro-intestinal mucosa.     

Mechanism of the postural vasoconstrictor response in the human foot

1. The mechanism of postural vasoconstriction in the skin of the foot was examined in 102 healthy subjects by using laser Doppler flowmetry. 2. In 45 subjects, when one foot was lowered 50 cm below heart level and the other foot kept horizontal, blood flow was progressively reduced in the dependent foot (by 79%) with a concomitant, but less pronounced, reduction in flow in the horizontal foot (by 18%), indicating that a central mechanism is involved. After lumbar sympathetic blockade (in 10 patients with epidural anaesthesia), the flow in the horizontal foot remained virtually constant, indicating that the central component is mainly mediated via efferent sympathetic nerves, whereas the postural fall in flow in the dependent foot, though partially attenuated, was preserved, indicating that a local mechanism is mainly involved. 3. On lowering one foot below heart level in 12 subjects, there was a small but significant reduction in systolic and mean arterial pressures during the first minute of dependency. During the fourth minute, systolic pressure decreased, diastolic pressure and heart rate increased, but the mean arterial pressure was maintained. 4. In 19 subjects postural vasoconstriction was nearly abolished during local nervous blockade (lignocaine 3.7 x 10(-4)-7.4 x 10(-2) mol/l), indicating that the local mechanism mediating the vasoconstriction is mainly neurogenic in nature. However, there was still a small fall (19%) in flow in the dependent foot during blockade, probably indicating a minor contribution of a local myogenic mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Local sympathetic reflex control of blood flow in human skin following topical corticosteroid treatment

Local positional vasomotor activity, or the veno-arteriolar reflex, was studied in normal human skin over 3 days of treatment with a potent corticosteroid under occlusion. Eight healthy subjects participated in the study. Using the atraumatic epicutaneous 133-Xe washout technique on the outer 2 mm of the skin fold between the first and the second finger, and covering the rest of the hand with a lead shield, blood flow in cutaneous tissue only was monitored. The veno-arteriolar reflex was elicited by inducing venous stasis. Before treatment, 40 mmHg venous stasis reduced cutaneous blood flow by 37.1% (95 percentile, 24.5-56.0). Following 24 h and 48 h of treatment, the reflex became weaker and at day 3, the blood flow reduction was 17.8% (7.6-42.6). The diminution was significant (p less than 0.05).     

静态直立时足位对眩晕患者姿势平衡的影响

目的：分析不同足位对眩晕患者静态直立时的姿势平衡影响。探讨足位在平衡控制和姿势描记中的作用。方法：眩晕组79例患者和正常组92例健康者进行如下静态直立试验：①标准Romberg试验，双足并拢站立；②双脚分开平行直立试验；③强化Romberg试验（踵趾位站立）；④单足直立试验。每种测试条件下分别睁眼和闭眼站立，用秒表记录①-④试验中维持平衡的时间，同时用SPG记录①、②条件下的人体足底压力中心的晃动速度（sway velocitv，SV）。结果：①维持平衡时间：眩晕组采取踵趾位和单足站立时，维持平衡时间较正常组降低．差异均有极显著性意义（P〈0．001）；②SV：采用标准Romberg位和双脚分开站立，眩晕组和正常组相比，睁眼时两组SV差异无显著性意义（P〉0．05）。而闭眼时，两组间差异均有显著性意义（P〈0．001）；③对于眩晕组和正常组，无论睁眼或闭眼，采用双脚分开站立时，SV较标准Romberg位时降低。差异有极显著性意义（P〈0．001）：④除眩晕组闭眼踵趾位下计时平衡试验结果与其睁眼时标准Romberg足位下的SV呈负相关性外（r=-0．244，P=-0．03），其他计时平衡测试结果与各足位下的SV均未发现有相关性。结论：静态直立时不同足位可影响人体平衡控制能力，踵趾位和单足直立测试是对姿势描记的补充．可结合应用于临床评价眩晕患者的平衡功能。     

Effect of local cold provocation on systolic blood pressure and skin blood flow in the finger

Demonstration of increased vascular cold reactivity in patients with Raynaud’s syndrome is difficult. For medico‐legal reasons, it is important to get objective measures of vasospasm in these patients. Evaluation of the degree of vasospasm also provides prognostic information which is useful for patient management. In this study, we compare two methods of arterial circulation measurement. The laser Doppler scanning is a new method, which uses the recently developed laser Doppler perfusion imaging (LDPI) instrument. The aim of the present study was to compare the effect on finger skin blood flow measured with LDPI with changes in finger systolic blood pressure during local cold provocation. The effect of such provocation, skin blood flow and systolic blood pressure, were studied in 15 healthy controls. Six patients with known traumatic vasospastic disease (TVD) were also tested with both methods. Finger skin blood flow was measured with LDPI on the distal phalanx of the index finger of the left hand, every minutes during 6 min of local heating at 40°C followed by local cooling for 3 min at 15°C and then for 3 min at 10°C. Finger systolic blood pressure was measured with strain‐gauge method before and after local cooling to 10°C with a cuff perfused with water of desired temperature. The test was performed in the same finger within a week of the laser Doppler scanning. Local finger cooling to 15°C and 10°C caused a significant decrease in blood flow, most marked at 10°C. There was, however, no correlation between the decrease in blood flow and blood pressure. In the TVD‐patients decreases in skin blood flow were similar compared with the healthy controls. In contrast, the changes in systolic blood pressure, were outside normal range (systolic quotient <0·65) in five of the six patients (83%), and also in 11 of the 15 healthy controls (73%). In conclusion, there is no correlation between the decrease in finger skin blood flow and systolic blood pressure during local cold provocation. For diagnosis of traumatic vasospastic disease (TVD), local cold‐induced changes in finger systolic blood pressure seems superior to changes in skin blood flow, but the ideal clinical method for demonstrating increased cold‐induced vasospasm is, however, still lacking.     

Cutaneous blood flow in the foot following lumbar sympathectomy

Cutaneous blood flow in the foot was assessed by 125I iodoantipyrine clearance in patients with peripheral vascular disease. Three groups were studied: group (a) consisted of 10 controls, Group (b) of 10 patients who had arterial reconstruction, and Group (c) of 10 patients having lumbar sympathectomy. Skin blood flow remained constant in the control patients. In Group (b) arterial reconstruction increased skin blood flow from mean 4.3 ml/100g/min to a mean of 14.9 ml/100g/min (p less than 0.001). In group (c) skin blood flow did not significantly change from a mean preoperative value of 7.6 ml/100g/min to a mean postoperative value of 8.1 (ml/100g/min). These results suggest that lumbar sympathectomy does not affect nutritional blood flow.     

Effect of lower-extremity muscle fatigue on postural control

OBJECTIVE: To examine the effects of fatigue of the lower extremity on postural control during single-leg stance. DESIGN: Pretest-posttest. SETTING: University research laboratory. PARTICIPANTS: Fourteen healthy volunteers (age, 21+/-2y) with no history of lower-extremity injury or neurologic deficits. INTERVENTIONS: Testing consisted of isokinetically fatiguing the sagittal plane movers of the ankle, knee, or hip with measures of static postural control. Postural control was assessed with three 30-second trials during unilateral stance with eyes open. MAIN OUTCOME MEASURES: Center of pressure excursion velocity (COPV) in the frontal and sagittal planes. RESULTS: Fatigue at the knee and hip led to postural control impairment in the frontal plane, whereas fatigue at the ankle did not. In the sagittal plane, fatigue at all 3 joints contributed to postural control impairment. CONCLUSIONS: Our results suggest that there is an effect of localized fatigue of the sagittal plane movers of the lower extremity on COPV. It appears that fatigue about the hip and knee had a greater adverse affect on COPV.     

A comparison of changes in rhythms of sacral skin blood flow in response to heating and indentation

OBJECTIVE: To differentiate blood flow control mechanisms associated with indentation from those associated with heating and to discern heat-induced and pressure-induced changes by comparing the effect of externally applied stress on skin blood flow (SBF) to the response to externally applied heat. DESIGN: Repeated-measures design. SETTING: A university research laboratory. PARTICIPANTS: Ten healthy, young adults (5 men, 5 women; mean age +/- standard deviation, 30.0+/-3.1y). Intervention Incremental heat (35 degrees -45 degrees C, 1 degrees step/min) and pressure (0-60 mmHg, 5 mmHg step/3 min) on the sacrum using a computer-controlled indenter. Sessions for heat and pressure protocols were separated by 7+/-2 days. MAIN OUTCOME MEASURES: We used a Laserflo Blood Perfusion Monitor 2 and Softip pencil probe to measure capillary blood perfusion and wavelet analysis to decompose the blood flow signal. The power spectrum was divided into 5 ranges corresponding to metabolic, neurogenic, myogenic, respiratory, and cardiac control mechanisms. The average relative (ie, normalized) power in each frequency range was computed to determine of the relative contribution of each control mechanism. RESULTS: Power in the myogenic frequency range was higher after incremental pressure and lower after incremental heating, whereas power in the metabolic frequency range was lower after incremental pressure and higher after incremental heating ( P <.01). Mean blood flow decreased as pressure increased from 0 to 15 mmHg; mean blood flow increased as pressure increased from 15 to 60 mmHg. CONCLUSIONS: SBF, as recorded by the laser Doppler, suggests that there may be a myogenic control mechanism mediating blood flow after incremental tissue loads and that a metabolic control mechanism may mediate blood flow after heat application to the tissue. The study of local blood flow control mechanisms and their response to pathomechanical perturbations may be possible using wavelet analysis of blood flow oscillations. More research is needed to establish the clinical utility of these findings in the development of support surfaces intended to reduce the risk of developing pressure ulcers.     

The influence of local skin heating and reactive hyperaemia on skin blood flow abnormalities in patients with reflex sympathetic dystrophy (RSD)

Abstract. Skin blood flow in reflex sympathetic dystrophy (RSD) patients has been reported to develop from an increase at an early stage to a decrease at later stages. So far, it remains unclear whether these abnormalities are solely of microcirculatory origin, and result from functional vasospasm or structural vessel wall changes. Eighty-seven RSD patients were categorized as follows: stage I in case of a stationary warmth sensation; stage II in case of an intermittent warmth and cold sensation; and stage III in case of a stationary cold sensation. Laser Doppler flowmetry (LDF) was used as a measure of total skin blood flow and transcutaneous oximetry (TCPO2) as a measure of vascular reactivity in the more superficial skin layers. Local skin heating and reactive hyperaemia were used to study the relative reserve capacity of skin microvessels. Finapres was used to assess digital arterial pressures. As compared to healthy volunteers ( n =16), LDF under control conditions demonstrated an increase in skin blood flow at stage I ( P <0.01). A decrease in skin blood flow under control conditions was seen at stages II ( P <0.05) and III ( P <0.05), but the relative flow reserve capacity, as measured with LDF, was not impaired at these stages. Regression analysis did not show a relation between LDF parameters and duration of the syndrome. TCPO2 revealed no differences between patient groups and controls. Regression analysis did not demonstrate a relation between TCPO2 parameters and duration of the syndrome. Digital systolic blood pressures were increased at stages II ( P <0.05) and III ( p <0.001). These findings indicate that abnormalities in skin blood flow, as observed in RSD patients, are of microcirculatory origin. The observed decrease in skin blood flow at stages II and III most likely results from functional vasospasm rather than from structural vessel wall changes.     

Local skin blood flow in hypokinesis

Functional indices of peripheral autonomic nervous system responsible for regulation of tissue circulation were studied with doppler laser-flowmetry in patients exposed to long-term hypokinesia. Valsalva test, orthostatic test, cold test, etc., have discovered shifts in the system regulating local skin blood flow. Compared to control, changes in the blood flow were considerable and its recovery went very slowly.     

Endogenous vasopressin affects postural control of blood pressure in man

1. Six healthy volunteers received intravenous infusions of isotonic (0.9% NaCl) and hypertonic (3% NaCl) saline on separate days. There were no significant changes in blood pressure or forearm blood flow, despite an increase in plasma arginine vasopressin (AVP) during hypertonic saline. 2. Immediately and 10 min after passive tilting to 50 degrees, mean forearm blood flow fell by 17.1 and 14.3% compared with the values in the supine position during isotonic saline and by 40.3 and 43.3% during hypertonic saline. Forearm vascular resistance rose by 23.6 and 17.8% with isotonic saline and by 80.2 and 88.2% with hypertonic saline for the two readings in the tilted compared with the supine position. 3. Tilting was associated with a 14.9 and 12.1% rise in diastolic blood pressure immediately and 10 min after assuming this position during hypertonic saline, and a rise of 6.4% in mean arterial pressure. 4. The results from this study are similar to those obtained previously, when small amounts of AVP were infused. They provide further evidence that AVP may have a physiological role in the postural regulation of blood pressure.     

Effects of contrast baths on skin blood flow on the dorsal and plantar foot in people with type 2 diabetes and age-matched controls

Contrast baths have been used for therapy for over 2,000 years. The basic concept is to alternate warm and cool water baths during a treatment session. It is believed that this will increase circulation better than just placing the limb in a warm water bath. However, there is little supportive evidence for this assertion. Further, for subjects with diabetes, with underlying impairments in their circulation, this may not work at all. Fourteen people with type 2 diabetes were compared to 14 age-matched controls. Skin blood flow of the foot (BF) was measured during 16 minutes of contrast baths at two different intervals: 3 minutes warm and 1 minute cold and 6 minutes warm and 2 minutes cold. In control subjects, warm and cold contrast baths with the ratio 3 minutes warm to 1 minute cold elicited significantly (p < 0.01) greater BF than placing the limb continuously in warm water or using a 6:2 ratio of warm to cold bath time. In control subjects, there was also a greater plantar than dorsal BF. For subjects with diabetes, there was no statistical difference between BF with contrast baths versus warm whirlpool; but in both cases BF was significantly less than that seen in control subjects under similar circumstances. There was also very little difference between BF on the plantar and dorsal aspects of the foot in the subjects with diabetes. Patients with diabetes do not show a vascular response to contrast bath therapy. The BF response to contrast temperatures may be a good diagnostic test for diabetic vascular impairment.     

Age-related changes in postural control associated with location of the center of gravity and foot pressure

The purpose of this study was to assess the limitations of the head and lumbar movements in relation to the center of gravity which is needed to maintain standing balance with aging. The subjects of the study were 22 healthy volunteers. The subjects were divided into two age categories, the young group (mean 21.7 +/- 2.9 years, 7 males and 6 females); and the elderly group (mean 71.3 +/-2.6 years, 3 males and 4 females). The instruments for measuring lumbar and head movements and the center of pressure (COP) were a three-dimensional motion analysis system and a force plate. In addition, the peak foot pressure was measured during standing using the F-Scan system. The subjects were first asked to stand relaxed for 10 s. They then shifted from the starting position to the four directions (sways); anterior, posterior, right, and left. They tried to maintain standing balance at the maximal possible distance position for each sway for 10 seconds. Analyzing parameters were performed by measuring the average maximal linear displacement (cm) of the head and lumbar markers, the COP (cm), and the peak foot pressure (percent of body weight per squared centimeters; BW%/cm2) in each subject. The data of the young group for lumbar maximal displacement were greater than those of the elderly group in the anterior, posterior, and lateral sways. A significant difference between the young and elderly data was found in the posterior sway. According to the data of the head's maximal displacement, the elderly group was greater than the young group in all sways except for the anterior side. For the data of peak foot pressure in the posterior sway, the elderly group's data was greater than the young group's data. The forefoot area data of the young group was significantly greater than that of the elderly group and the heel area data of the elderly was significantly greater than that of the young group in the right sway. The results suggest that evaluating the maximal displacement of head and lumbar positions and toe's activity in the forefoot are all important factors associated with the center of gravity in healthy adults.     

Influence of neuropathy on the microvascular response to local heating in the human diabetic foot.

1. The diabetic neuropathic foot exhibits excess arteriovenous anastomotic shunt flow due to a reduced sympathetic vasoconstrictor tone. Local axon reflexes (mediating postural vasoconstriction, for example) are preserved even in severe diabetic neuropathy. This excess shunt flow and its local neurogenic control may be important in the development of complications of the neuropathic limb. 2. The response of arteriovenous anastomoses to local heating was assessed in 13 diabetic patients with neuropathy (12 insulin-dependent), 10 diabetic control patients (seven insulin-dependent) and 10 normal control subjects. The aim was to study the local reflex control of arteriovenous flow when central sympathetic tone had been largely removed. 3. The change in skin blood flow on local heating to 44 degrees C was measured by using a laser Doppler flowmeter in standard environmental conditions with the foot at heart level. Two sites were assessed: (i) the plantar surface of the great toe (a site in which skin blood flow is dominated by arteriovenous shunt flow) and (ii) the dorsum of the foot (a site without anastomotic flow). 4. It was found that when heat was applied to the plantar surface of the great toe in the diabetic patients with neuropathy a paradoxical decrease in flow through arteriovenous anastomoses occurred, flow declining to 65% (P less than 0.05) of its resting value. This could be compared with an increase in flow over the same time period of 262% and 228% (P less than 0.01) in diabetic control patients and normal subjects, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Finger skin blood flow in response to indirect cooling in normal subjects and in patients before and after sympathectomy

Finger skin blood flow was measured in 80 healthy subjects, using laser Doppler imaging during basal vasodilatation at a local temperature of 40°C. The response to cooling of the contralateral hand at 15°C was studied. A vasoconstriction index was calculated in all subjects and a nomogram was constructed, taking age into consideration. Compared with these normal subjects, four patients operated on with transthoracic endoscopic sympathectomy due to hand hyperhidrosis showed clearly attenuated responses. The results indicate that the test can be used to assess disturbances in the sympathetic regulation of the peripheral blood flow.     

Nocturnal foot blood flow in patients with arterial insufficiency

Twenty-four hour continuous recording of xenon (133Xe) wash-out from the forefoot was performed on patients with normal circulations (n = 10) and on patients with different degrees of arterial insufficiency (n = 36). During day hours the calculated subcutaneous blood flow in the forefoot was on average the same in patients with normal circulations and in patients with different degrees of arterial insufficiency (mean: 2.0 +/- 0.8 ml min-1 100 g-1). During sleep the blood flow nearly doubled in patients with normal circulations; no systematic change was seen in patients with intermittent claudication. In patients with severe ischaemia, i.e. having rest pain, the blood flow decreased by approximately 50%. The changes in local blood flow may be due to changes in local sympathetic tone and to changes in local perfusion pressure.