Cutaneous Red Cell Flux Research Articles

Impact of cutaneous blood flow on NIR-DCS measures of skeletal muscle blood flow index.

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical technique for estimating relative changes in skeletal muscle perfusion during exercise but may be affected by changes in cutaneous blood flow, as photons emitted by the laser must first pass through the skin. Accordingly, the purpose of this investigation was to examine how increased cutaneous blood flow affects NIR-DCS blood flow index (BFI) at rest and during exercise using a passive whole body heating protocol that increases cutaneous, but not skeletal muscle, perfusion in the uncovered limb. BFI and cutaneous perfusion (laser-Doppler flowmetry) were assessed in 15 healthy young subjects before (e.g., rest) and during 5 min of moderate-intensity handgrip exercise in normothermic conditions and after cutaneous blood flow was elevated via whole body heating. Hyperthermia significantly increased both cutaneous perfusion (∼7.3-fold; P ≤ 0.001) and NIR-DCS BFI (∼4.5-fold; P ≤ 0.001). Although relative BFI (i.e., fold-change above baseline) exhibited a typical exponential increase in muscle perfusion during normothermic exercise (2.81 ± 0.95), there was almost no change in BFI during hyperthermic exercise (1.43 ± 0.44). A subset of eight subjects were subsequently treated with intradermal injection of botulinum toxin-A (Botox) to block heating-induced elevations in cutaneous blood flow, which 1) nearly abolished the hyperthermia-induced increase in BFI and 2) restored BFI kinetics during hyperthermic exercise to values that were not different from normothermic exercise (P = 0.091). Collectively, our results demonstrate that cutaneous blood flow can have a substantial, detrimental impact on NIR-DCS estimates of skeletal muscle perfusion and highlight the need for technical and/or pharmacological advancements to overcome this issue moving forward.NEW & NOTEWORTHY We used passive whole body heat stress, in combination with local intradermal botulinum toxin type A treatment, to experimentally manipulate cutaneous blood flow and investigate its impact on NIR-DCS measures of skeletal muscle BFI at rest and during exercise. Collectively, the results show that cutaneous blood flow, which was augmented in response to passive whole body heat stress, markedly affects NIR-DCS-derived BFI, such that the BFI signal becomes dominated by changes in cutaneous red blood cell flux.

Regional Cutaneous Vasodilator Responses to Rapid Local Heating in Young Women and Men

The cutaneous vasodilator response to rapid, non‐painful, local skin heating is commonly used to test microvascular reactivity in health and disease states. The response is characterized by a transient initial vasodilatory peak that is primarily mediated by cutaneous sensory nerves, followed by a sustained plateau phase that is mainly nitric oxide dependent. While this test is most often performed on the forearm due to ease of administration, examining how local neurovascular (initial peak) and endothelium‐dependent (sustained plateau) vasodilator function varies across the body may provide important knowledge underlying regional differences in cutaneous perfusion. Thus, the purpose of this study was to characterize regional cutaneous vasodilator responses to rapid local skin heating in young adults and to determine if sex modulates these responses. In twenty‐nine (14 women) young adults, cutaneous red blood cell flux (AU, arbitrary units) was measured via laser‐Doppler flowmetry on the anterior calf, anterior thigh, abdomen, dorsal forearm, arm, and chest. Participants rested in the supine position for 30 min with skin sites in all regions controlled at 33°C. Following a 10 min baseline period all sites were rapidly heated to 42°C (1°C×20−s) with local heaters and maintained until a stable plateau was achieved (20–30 min). Sites were then heated to 44°C (20–30 min) to achieve maximum vasodilation. Blood pressure was measured manually every 10 min throughout. Cutaneous vasodilator responses were presented as cutaneous vascular conductance (CVC, AU×mmHg−1), normalized to maximum local heating (%CVCmax). Statistical significance was set at P<0.05 and all comparisons are presented as mean differences (95%CI) relative to the forearm. Baseline, initial peak, and plateau responses represent the combined group (n=29) since there were no sex differences across body regions (all P>0.05). At baseline, only responses at the chest (+5.0[2.2,7.8]%CVCmax), thigh (+4.8[1.9,7.6]%CVCmax), and calf (+4.8[1.4,8.2]%CVCmax) differed from the forearm (all P<0.05). For the initial peak, only the arm (+6.5[0.5,12.5]%CVCmax) and abdomen (−10.0[−17.2,−2.8]%CVCmax) differed from the forearm (both P<0.05). During the sustained plateau phase only the abdomen (−13.7[−19.4,−7.9]%CVCmax) and thigh (−6.0[−9.5,−2.4]CVCmax) differed from the forearm (both P<0.05). During maximum local heating, there was a significant sex by region interaction for absolute CVC (P<0.05). No regional differences in maximum responses were found for women, while for men maximum responses were greater at the thigh (−1.3[−2.1,−0.4] AU×mmHg−1) and calf (−1.3[−2.1,−0.5] AU×mmHg−1) relative to the forearm (both P<0.05). Our findings demonstrate that neurovascular (initial peak) and endothelium‐dependent (sustained plateau) cutaneous vasodilator responses to rapid local heating across the body are similar to the forearm, except for the abdomen, which was attenuated. Further, sex does not modulate these responses in young adults.Support or Funding InformationFunding support: Natural Sciences and Engineering Research Council of Canada (held by Dr. Kenny).

Seven Consecutive Days of Remote Ischemic Preconditioning Improved Cutaneous Vascular Reactivity Induced by Post Occlusive Reactive Hyperemia

ObjectiveRemote ischemic preconditioning (RIPC), induced by brief periods of ischemia followed by reperfusion, elicits strong cardioprotection from ischemia reperfusion injury in animal models. However, recent clinical trials in humans have yielded mixed results that may be explained by coexisting conditions and other experimental factors. Using human skin as an alternative model to study RIPC, we hypothesized that cutaneous vascular reactivity to post‐occlusive reactive hyperemia (PORH) will be increased following repeated RIPC.MethodsYoung healthy participants (26 ± 1 years; 4 male, 5 female) performed RIPC for seven consecutive days. Each daily RIPC session consisted of 4 repetitions of 5 minutes of upper arm blood flow occlusion interspersed by 5 minutes non‐occlusion. Pre‐ and 24 hours post‐RIPC training, an index of skin microvascular blood flow (i.e., cutaneous red blood cell flux) was measured from the ventral forearm using laser speckle contrast imaging. Flux was measured continuously during baseline, 5 minutes of arm blood flow occlusion with 200 mmHg of cuff pressure, and during 5 minutes of PORH. Peak flux during hyperemia, Max (peak after subtracting baseline), Time to peak (Tp) (index of vascular resistance), Max/Tp (indicator of early vascular changes), and area under curve (AUC) were analyzed from collected data. Data are presented as cutaneous vascular conductance (CVC), which was calculated as flux/mean arterial pressure.ResultsSeven consecutive days of RIPC increased Max/Tp (Pre: 0.10 ± 0.02 vs. Post: 0.12 ± 0.02 CVC/sec, p<0.05). Although not statistically different, other indices of PORH were increased; AUC (Pre: 89.7 ± 13.5 vs. Post: 107.2 ± 10.4 CVC·sec, p=0.10), Peak (Pre: 2.18 ± 0.02 vs. Post: 2.28 ± 0.20 CVC, p=0.33), Max (Pre: 1.68 ± 0.20 vs. Post: 1.79 ± 0.20 CVC, p=0.18), and Time to peak (Tp) (Pre: 18.6 ± 1.1 vs. Post: 17.0 ± 1.3 sec, p=0.11).ConclusionsSeven consecutive days of RIPC augmented cutaneous microvascular reactivity to PORH. Collectively, these data support repeated RIPC as a means to improve microvascular function in humans.All experimental procedures were approved by the Institutional Review Board at Des Moines University and conformed to the standards set by the Declaration of Helsinki (IRB#: 08‐15‐05)Support or Funding InformationFunding source: Des Moines University, IOER #03‐14‐01 (PI: J. Lang)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Comparison in young White European (WE) and South Asian (SA) men of endothelium‐dependent cutaneous vasodilator responses: contribution of cyclooxygenase (COX) products

It is established that cardiovascular disease is more prevalent in South Asians (SA) than White Europeans (WE). The prevalence of diabetes central obesity and metabolic syndrome is particularly high in SAs, disorders that are associated with endothelial dysfunction. It is not known whether early markers of endothelial dysfunction can be detected even in young healthy SAs. Thus, we have compared responses evoked in recreationally‐active WE and SA men (18–25 years; n=10 in each case). SAs were 1st or 2nd generation residents in the UK with mother and father originating from India, Sri Lanka, Bangladesh or Pakistan; WEs were UK residents with WE parents. By using laser Doppler fluximetry, we monitored changes in cutaneous red cell flux (RCF) evoked in the cutaneous circulation of the forearm by iontophoresis of the endothelium‐dependent dilator acetylcholine (ACh, 8 × 20s pulses: 7 at 100 μA, 8th at 200 μA, at 60s intervals) and by release of arterial occlusion for 3 min (reactive hyperaemia). Responses were tested before and after aspirin (600mg p.o.) to assess the role of COX products. Mean arterial blood pressure (ABP) was continuously monitored by photoplethysmography using a finger cuff. Resting ABP was similar in WEs and SAs (124±1.8/70±1.7 vs 116.6±2.0/65.4±1.6 mmHg) and did not change during the protocol. Baseline RCF was also similar in WEs and SAs: 19.7±1.9 vs 12.3±0.9 perfusion units (PU), respectively. Further, ACh evoked similar dilator responses in WEs and SA, maximum RCF reaching 192.2±5.5 and 182.83 ± 5.20 perfusion units (PU) respectively. Aspirin had no net effect on ACh‐induced dilatation in either group (WEs: 182.6±4.5 and SAs: 193.0± 7.7 PU) indicating any influence of COX dilator and vasoconstrictor products was balanced in both WEs and SAs. By contrast, before aspirin, reactive hyperaemia was substantially larger in WEs than SA, peak RCF being 92.9±2.5 vs 74.2±3.1*PU, *: P<0.01 RMANOVA). Further, aspirin attenuated reactive hyperaemia in WEs, peak RCF being only 75.1 ± 2.6§PU: §: P<0.001 vs control response, but enhanced reactive hyperaemia in SAs, peak RCF reaching 84.7±2.7§PU. These results suggest that in young SA men, who have no overt signs of cardiovascular disease and are normotensive, there are already signs of endothelial dysfunction. Agonist‐evoked endothelium‐dependent dilatation is apparently normal in SAs with no net contribution from COX dilator or vasoconstrictor products, suggesting that nitric oxide and/or Endothelium‐dependent hyperpolarising factor are the main contributors in both ethnicities. However, reactive hyperaemia, which is induced by the combination of shear‐stress and metabolic stimuli, is blunted in young SAs relative to WEs and this is attributable to a predominating influence of vasoconstrictor COX products in SAs, but vasodilator COX products in WEs.Support or Funding InformationAlexander S. Onassis Public Benefit Foundation

Experimental investigation of non‐freezing cold‐induced injury: are young Asian males more susceptible than young white Caucasians and are cyclooxygenase products involved? (1106.5)

Prolonged or repeated exposure to cold conditions can induce NFCI; Afro‐Caribbeans are more susceptible than white Caucasians. We compared in Caucasian and Asian males (20‐22 years, n=6), responses evoked by 3 immersions of the right leg in water at 15°C for 10 min with 10‐min intervals, the left leg was ~horizontal. In Caucasians, cutaneous red cell flux in right foot (rRCF) fell from 12.8±2.4 to 11.6±1.3, 9.2±1.6* and 8.6±1.5PU in immersions 1, 2 and 3 with some recovery to11.3±2.4, 9.7±2.3* and 9.6±1.6* PU (*: P<0.05 vs baseline). By contrast, in Asians, rRCF fell from 11.1±2.4 to as low as 7.0±0.9*, 6.3±0.8* and 5.8±0.7*PU, with no recovery: 6.8±0.8*, 6.6±0.8*, 6.8±0.7*PU. Caucasians showed no change in contralateral left RCF whereas in Asians, left RCF fell from 25.3±4.2 to 20.1±0.0.9, 20.4±2.8 and 20.5±0.7PU. After COX inhibition (aspirin; 600mg p.o), rRCF fell from 18.0±4.8 to 13.6±4.9*, 11.8±3.7* and 10.9±3.8* during 1st, 2nd and 3rd immersions in Caucasians, with no recovery: 13.5±4.0*, 13.2±4.7* and 11.7±4.0* PU. In Asians, rRCF fell from 7.7±0.9 to 5.9±0.7*, 5.6±0.6* and 5.8±0.6* PU, with no recovery: 5.8±0.9*, 5.6±0.7* and 5.6±0.7*PU. We suggest that young Asians show greater and more persistent local and reflex cutaneous vasoconstrictor responses to cool water immersion than Caucasians and so may be more vulnerable to NFCI; vasodilator COX products may limit cold‐induced vasoconstriction in Caucasians.

Effect of voluntary hypocapnic hyperventilation on cutaneous circulation in resting heated humans

Hypocapnia attenuates the sweat response normally seen in hyperthermic resting subjects, but its effect on the blood flow response in their nonglabrous skin under the same hyperthermic conditions remains unclear. In the present study, we investigated whether hypocapnia induced by voluntary hyperventilation affects the blood flow response to heat stress in the nonglabrous skin of resting humans. Nine healthy male subjects were passively heated using legs-only hot water immersion and a water-perfused suit, which caused esophageal temperature (T(es)) to increase by as much as 1.0°C. During normothermia and at +0.6°C T(es) and +1.0°C T(es), the subjects performed two voluntary 7-min hyperventilation (minute ventilation = 40 l/min) trials (hypocapnic and eucapnic) in random order. End-tidal CO(2) pressure was reduced by 23-25 torr during hypocapnic hyperventilation, but it was maintained at the spontaneous breathing level during eucapnic hyperventilation. Cutaneous blood flow was evaluated as the cutaneous red blood cell flux in the forearm (CBF(forearm)) or forehead (CBF(forehead)) and was normalized to the normothermic spontaneous breathing value. Hypocapnic hyperventilation at +0.6°C T(es) was associated with significantly reduced CBF(forearm), compared with eucapnic hyperventilation, after 5-7 min of hyperventilation (395 to 429 vs. 487 to 525% baseline, P < 0.05). No significant difference in CBF(forehead) was seen during hypocapnic hyperventilation compared with eucapnic hyperventilation at +0.6°C T(es) or +1.0°C T(es). These results suggest that in resting humans, hypocapnia achieved through voluntary hyperventilation attenuates the increase in cutaneous blood flow elicited by moderate heat stress in the nonglabrous skin of the forearm, but not the forehead.

The effect of voluntary hypocapnic hyperventilation on thermoregulatory responses in exercising humans

We tested the hypothesis that voluntary hypocapnic hyperventilation (VHH) attenuates thermoregulatory responses in exercising humans. 10 healthy active males performed cycling exercise at 120W (30°C, 50%RH) during 1) spontaneous breathing, 2) eucapnic voluntary hyperventilation, and 3) VHH. Cutaneous vascular conductance was evaluated as cutaneous red blood cell flux measured by laser‐Doppler flowmeter/mean arterial blood pressure at forearm (CVCforearm) and forehead (CVCforehead). Forearm sweat rate was measured by ventilated capsule method. Our results indicated that esophageal temperature (Tes) threshold for increases in CVCforearm and CVCforehead was significantly or tended to be higher, while slope relating Tes with CVCforearm was significantly or tended to be lower in VHH than in the other two conditions. Neither Tes threshold nor slope for sweat rate was different among conditions. These results suggest that in exercising humans, although VHH does not affect sweat response, it attenuates cutaneous vasodilation response, and this attenuation is greater for forearm than forehead skin.This study was supported by grants from the Ministry of Education, Science, and Culture of Japan. N. Fujii is the recipient of a research fellowship for young scientists from Japan Society of the Promotion of Science.

Effects of cyclooxygenase inhibition on vascular responses evoked in fingers of men and women by iontophoresis of α1‐ and α2‐adrenoceptor agonists

In 10 men and nine women aged 20-23 years, we aimed to establish whether endogenous prostanoids synthesised by cyclooxygenase (COX) affect responses evoked in the finger by α(1)- or α(2)-adrenoceptor agonists. Cutaneous red cell flux (cRCF) was recorded in dorsal finger during iontophoresis of phenylephrine (PE) or clonidine (0.5 mm, seven 0.1 mA pulses followed by one 0.2 mA pulse: 30 s each at 60 s intervals) before and after the COX inhibitor aspirin (600 mg p.o.). In men, PE evoked a biphasic mean increase/decrease in cRCF before but a monophasic mean decrease in cRCF of 30-40% after aspirin (P < 0.05). In women in the low oestrogen (E(2)) phase of the menstrual cycle, PE evoked a decrease in cRCF (30-40%; P < 0.05) that was unchanged by aspirin, whereas in the high E(2) phase, PE evoked no change before but a graded decrease in cRCF (30-40%; P < 0.05) after aspirin. Clonidine evoked a decrease in cRCF (∼30%; P < 0.05) in men before, but not after, aspirin. Clonidine evoked both increases and decreases in cRCF before and after aspirin in women in the low and high E(2) phases (P > 0.05). We propose that finger vasoconstriction evoked by extraluminal α(1)-adrenoceptor stimulation is blunted by vasodilator COX products in young men and overcome by their action in women in the high, but not low E(2), phase of the menstrual cycle. By contrast, α(2)-adrenoceptor stimulation evokes finger vasoconstriction that is mediated by vasoconstrictor COX products in young men, but evokes no consistent response in women in the low or high E(2) phases of the menstrual cycle.

Endothelium-dependent and endothelium-independent vasodilatation of the cutaneous circulation in sickle cell disease

Whilst there is evidence of endothelial dysfunction in sickle cell disease (SCD), whether this affects regulation in the microcirculation is not known. We studied 19 patients with SCD, eight with sickle cell-haemoglobin C (HbSC), 11 with homozygous sickle cell (HbSS) disease and 11 matched control subjects with normal haemoglobin genotype (HbAA). Vasodilator responses were evoked by iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) in finger and forearm, cutaneous red cell flux (RCF) being measured by laser Doppler fluximetry. Increases in RCF evoked in the finger by ACh were not different between SCD and HbAA subjects (P = 0·789), but were smaller in patients with HbSS than HbSC (P < 0·05). By contrast, increases in RCF evoked in forearm by ACh were greater in SCD than HbAA subjects (P < 0·05) and similar in patients with HbSC and HbSS. Increases in RCF evoked by SNP did not differ between patients with SCD and HbAA subjects in finger or forearm. Our results indicate that endothelium-dependent cutaneous vasodilatation is augmented in forearm of patients with SCD relative to HbAA subjects, but impaired in the finger of SCD patients with the more severe HbSS genotype. Thus, endothelial dysfunction associated with SCD is not accompanied by generalised impairment in endothelium-dependent dilatation, but with more localised impairment that includes the fingers of patients with HbSS.

Hypertonic saline attenuates cutaneous vasodilation in response to local heating

Salt may have a direct effect on vascular function by reducing nitric oxide (NO) production.PURPOSEThe purpose of this study was to examine the effects of hypertonic saline on NO‐mediated cutaneous vasodilation in response to local heating.METHODSNine healthy subjects (23 ± 2 years) were studied. We measured cutaneous red blood cell flux via laser Doppler in conjunction with intradermal microdialysis of 1) Ringer's solution (R), 2) 0.9% normal saline (NS), 3) 3% hypertonic saline (HS), and 4) 10 mM NG‐nitro‐L‐arginine methyl ester (L‐NAME) during local heating to 42°C. Microdialysis of 28 mM sodium nitroprusside (SNP) at 43°C was used for assessment of maximum cutaneous vascular conductance (CVCmax) and data was expressed as a percentage of CVCmax (%CVCmax).RESULTSBaseline %CVCmax did not differ between the four microdialysis sites (HS: 9 ± 4, R: 11 ± 6, NS: 7 ± 4, L‐NAME: 7 ± 2%; p = 0.9). Hypertonic saline significantly attenuated the plateau %CVCmax compared to Ringer's and 0.9% normal saline (HS: 74 ± 12, R: 89 ± 4, NS: 89 ± 5%; p&lt; 0.01) and L‐NAME reduced the plateau %CVCmax compared to other three sites (47 ± 7%, p&lt; 0.01).CONCLUSIONHypertonic saline attenuates the cutaneous vasodilation response to local heating suggesting a direct effect of salt on microvascular function. This effect may be mediated through a decreased production and/or availability of NO.Supported by Grant DK080469.

The effect of increasing doses of norepinephrine on tissue oxygenation and microvascular flow in patients with septic shock*

To investigate the effect of escalating doses of norepinephrine, aimed at achieving incremental increases in mean arterial pressure (MAP), on microvascular flow and tissue oxygenation in patients with septic shock. Single-center interventional study. University hospital intensive care unit. Sixteen patients with established septic shock. The norepinephrine dose was escalated to achieve incremental increases in the MAP from 60 to 70, 80, and 90 mm Hg. In addition to routine clinical measurements, cardiac output was determined using lithium dilution and arterial waveform analysis, cutaneous tissue Pto2 was measured using a Clark electrode, cutaneous red blood cell flux was assessed using laser Doppler flowmetry, and sublingual microvascular flow was evaluated using sidestream darkfield imaging. The mean (sd) norepinephrine dose increased from 0.18 (0.18) microg x kg(-1) x min(-1) at 60 mm Hg to 0.41 (0.26) microg x kg(-1) x min(-1) at 90 mm Hg (p < 0.0001). During this period, global oxygen delivery increased from 487 (418-642) to 662 (498-829) mL x min(-1) x m(-2) (p < 0.01), cutaneous Pto2 increased from 44 (11) to 54 (13) mm Hg (p < 0.0001) and cutaneous microvascular red blood cell flux increased from 26.1 (16.2-41.9) to 33.3 (20.3-46.7) perfusion units (p < 0.05). No changes in sublingual microvascular flow index, vessel density, the proportion of perfused vessels, perfused vessel density, or heterogeneity index were identified by sidestream darkfield imaging. In patients with septic shock, targeting higher MAP by increasing the dose of norepinephrine resulted in an increase in global oxygen delivery, cutaneous microvascular flow, and tissue oxygenation. There were no changes in preexisting abnormalities of sublingual microvascular flow. Further research is required to clarify the optimal end points for vasopressor therapy in patients with septic shock.

Microvascular flow and tissue oxygenation after major abdominal surgery: association with post-operative complications

To evaluate the relationship between global oxygen delivery (DO(2)I), microvascular flow and tissue oxygenation in patients who did and did not develop complications following major abdominal surgery. Prospective observational study. Post-operative critical care unit. Twenty-five patients receiving standard peri-operative care following major abdominal surgery. Data were collected before, and for 8 h after surgery. DO(2)I was measured by lithium dilution and arterial waveform analysis. Cutaneous PtO(2) was measured at two sites on the abdominal wall using a Clark electrode. The sublingual microcirculation was visualised using sidestream darkfield imaging. Cutaneous red cell flux was measured using laser Doppler flowmetry. Fourteen patients (56%) developed complications with two deaths. Small vessel (<20 microm) microvascular flow index in those patients who developed complications was lower before (P < 0.05) and after surgery (P < 0.0001) compared to patients who did not develop complications. Both the proportion and density of perfused small vessels were also lower in patients who developed complications after surgery (P < 0.01) but not before surgery. DO(2)I was low in all patients but did not differ between patients who did and did not develop complications. Similarly, there were no associated differences in cutaneous red cell flux or PtO(2). In a group of patients with low DO(2)I following major abdominal surgery, microvascular flow abnormalities were more frequent in patients who developed complications. However, there were no differences in DO(2)I, cutaneous PtO(2) or red cell flux between the two groups. Impaired microvascular flow may be associated with the development of post-operative complications.

Contribution of prostanoids to endothelium-dependent vasodilatation in the digital circulation of women with primary Raynaud's disease

In 15 women with PR (primary Raynaud's) disease and in 15 matched control women, ACh (acetylcholine) was delivered by iontophoresis to the dorsum of the finger (seven 20 s pulses of 0.1 mA, followed by one 20 s pulse of 0.2 mA, applied at 60 s intervals). Cutaneous RCF (red cell flux) was recorded from the same site by the laser Doppler technique. ACh evoked progressive increases in RCF that were comparable in pre- and post-menopausal women with PR [maxima of 294+/-113 and 259+/-59 pu (perfusion units) respectively, n = 7 and 8 respectively], and in pre-menopausal controls (225+/-92 pu, n = 7), but smaller in post-menopausal controls (140+/-63 pu, n = 8; P < 0.05). Aspirin (600 mg, orally), a COX (cyclo-oxygenase) inhibitor, potentiated the ACh-evoked dilator responses in pre- and post-menopausal women with PR (343+/-129 and 311+/-48 pu respectively) and post-menopausal controls (277+/-124 pu; P < 0.05), but had no effect in pre-menopausal controls (225+/-92 pu). These results suggest that vasoconstrictor COX products limit ACh-evoked endothelium-dependent cutaneous dilatation in the digits in pre- and post-menopausal women with PR and in post-menopausal, but not pre-menopausal, control women. We propose that PR disease is associated with abnormality in the ability of oestrogen to modulate the synthesis of endothelium-dependent vasodilator and/or vasoconstrictor COX products.

Tissue oxygenation and perfusion in patients with systemic sepsis.

Multiple organ dysfunction is associated with systemic sepsis. To investigate whether this is attributable to peripheral tissue hypoperfusion and/or cellular hypoxia, simultaneous measurements of tissue perfusion and oxygenation were made in patients with severe sepsis and in controls. Prospective, observational study. Adult intensive care unit, tertiary referral center. Volunteers (group C, n = 7), patients undergoing cardiopulmonary bypass (group B, n = 6), and patients with severe sepsis (group S, n = 6). Limb ischemia and reperfusion. Tissue oxygenation and microvascular flow were measured by using microelectrodes inserted into brachoradialis muscle and overlying subcutaneous tissue. Forearm cutaneous red cell flux and regional blood flow were measured simultaneously. Responses to 20 mins of limb ischemia and subsequent reperfusion were observed. Baseline muscle tissue oxygenation was greater in sepsis (1.7 +/- 0.2, 1.5 +/- 0.7, and 4.4 +/- 0.6 kPa for groups C, B, and S, respectively, mean +/- sem, p <.05), although baseline subcutaneous tissue oxygenation did not vary between groups. During ischemia tissue oxygenation, values decreased in muscle (to 1.3 +/- 0.2, 1.0 +/- 0.4, and 1.5 +/- 0.4 kPa for groups C, B, and S, respectively) and subcutaneous tissue (to 2.0 +/- 0.3, 1.7 +/- 0.5, and 2.3 +/- 0.2 kPa for groups C, B, and S, respectively). Decline in tissue oxygen tension was initially more rapid in septic muscle compared with controls (25% decrease, 68 +/- 23 vs. 176 +/- 38 for group S vs. group C, p <.05, and 50% decrease, 126 +/- 34 vs. 398 +/- 72 secs for group S vs. group C, p <.01). However, overall rate of tissue decline was similar (95% decrease, 444 +/- 122 vs. 614 +/- 96 for group S vs. group C, p >.05). After reperfusion, significant differences in muscle tissue oxygenation reappeared between groups (2.0 +/- 0.3, 1.5 +/- 0.7, and 4.0 +/- 0.4 kPa for groups C, B, and S, respectively, p <.05). There were no differences in time to 25%, 50%, or 95% tissue oxygen recovery. Whole limb reperfusion was significantly less in patient groups compared with controls (10.6 +/- 0.9, 4.5 +/- 1.2, and 4.3 +/- 1.6 mL x 100 mL(-1) x min(-1) for groups C, B, and S, respectively, p <.05). Significant differences in tissue oxygenation distribution between muscle and subcutaneous tissues occur in patients with severe sepsis. High baseline muscle tissue oxygen levels are accompanied by rapid extraction of oxygen during stagnant ischemia.

Abnormal venous function in patients with homozygous sickle cell (SS) disease and chronic leg ulcers

Chronic leg ulceration is a major cause of morbidity in homozygous sickle cell (SS) disease in Jamaica. These ulcers have features in common with venous ulcers in patients with a normal haemoglobin genotype (AA). Thus we sought to determine whether there is abnormal venous function in the legs of patients with SS disease who have ulcers. Experiments were performed on 15 SS patients with ulcers, and on 15 SS patients and 15 AA subjects with no history of leg ulcers. Changes in venous blood volume of the bottom one-third of the leg induced by venous occlusion and release were studied by air plethysmography, providing indices of segmental venous capacitance (SVC), maximal venous outflow (MVO) and venous emptying time (VET). The changes in volume (ambulatory volume change; AVC) induced by a period of leg exercise were also measured at the ankle (AVCa) and calf (AVCc); venous refilling times at these sites (RTa and RTc respectively) were also measured. Finally, cutaneous red blood cell flux recovery time (FRT) after ankle exercise was assessed by laser Doppler flowmetry. Measurements were also made of haematological variables. SVC, MVO and VET did not differ between the groups, indicating no deep venous obstruction in the SS patients with ulcers. AVCc, AVCa and RTc did not differ among the three subject groups. However, compared with AA subjects, SS patients with ulcers had reduced RTa and FRT. Moreover, RTa and FRT were further shortened in SS patients with ulcers relative to SS patients without ulcers. Since the levels of anaemia were similar in SS patients with and without ulcers, these differences cannot be attributed to differences in arterial flow secondary to anaemia. These results suggest abnormal venous function in SS patients with ulcers, relative to both AA subjects and SS patients without ulcers. We propose that there is incompetence of venous valves draining the ankle region of SS patients with ulcers: the consequent raised venous pressure contributes to the slow healing and, possibly, to the onset of leg ulceration in SS disease.

The cutaneous vasoconstrictor response to venous stasis is normal in subjects with primary Raynaud's disease.

In control subjects and in subjects with primary Raynaud's disease, sudden sound or a mild cool stimulus evokes the pattern of alerting response that includes cutaneous vasoconstriction but vasodilatation in forearm muscle. In control subjects, response habituates on repetition of these stimuli both within experimental sessions and over successive days. However, in subjects with primary Raynaud's disease, the cutaneous vasoconstriction and the muscle vasodilatation persist. We have now tested whether a similar disparity exists for the cutaneous vasoconstriction evoked by venous stasis, a response considered to be a veno-arteriolar reflex mediated by sympathetic fibers, but not requiring transmission through the spinal cord. In 10 subjects with primary Raynaud's disease and in 10 matched controls, a sphygmomanometer cuff on the left arm was inflated to 40 mm Hg for 2 minutes, five times on each of three experimental sessions on days 1, 3, and 5. Cutaneous red cell flux (RCF) was recorded from the pulp and dorsum of the left index finger by using a laser Doppler meter; digital vascular conductance (DCVC) was computed as RCF divided by arterial pressure. The first venous stasis, in session 1, evoked a decrease in pulp and dorsum DCVC in the control and primary Raynaud's subjects. There were no differences between the groups in the magnitudes or durations of these responses. Within session 1, the magnitude of the decrease in DCVC diminished on repetition of venous stasis in the dorsum in controls and in the pulp in primary Raynaud's subjects. We propose these effects reflected the similar reductions in baseline DCVC over time; there was no change in the duration of the responses. Repetition of venous stasis had similar effects in both groups of subjects within sessions 2 and 3. Further, judging from the mean of the responses evoked in each Session the decreases evoked in pulp and dorsum DCVC by venous stasis were fully consistent in magnitude and duration over the three sessions in both groups. These results indicate that the direct constrictor influence of sympathetic fibers upon cutaneous blood vessels is similar in magnitude and similarly reproducible in controls and subjects with primary Raynaud's disease. This reinforces our view that the lack of habituation of the cutaneous vasoconstrictor component of the alerting response in subjects with primary Raynaud's disease reflects impairment of the central neural process of habituation, rather than a peripheral phenomenon, and that this lack of habituation predisposes these subjects to vasospasm.

Postural Vasoconstriction and Leg Ulceration in Homozygous Sickle Cell Disease

1. Chronic leg ulceration is a major cause of morbidity in patients with homozygous sickle cell disease; the ulcers commonly resolve on bed rest. We have therefore compared the cutaneous vascular response to dependency in three groups of eight patients with sickle cell disease (those with an active ulcer, with an ulcer scar and with no history of ulceration) and in eight subjects with normal haemoglobin and no history of leg ulceration. 2. We monitored, with a laser Doppler flowmeter, the change in red cell (erythrocyte) flux induced in the skin of the leg, at two sites proximal to the malleoli, with the leg horizontal and 5 and 10 min after moving the leg to the dependent position. 3. With the leg horizontal, mean cutaneous red cell flux was substantially higher in normal skin of patients with sickle cell disease than in normal subjects and was higher still at the site of the ulcer or scar. On dependency, red cell flux fell not only in normal subjects but also in the patients with sickle cell disease, both in the normal skin and at the site of the ulcer or scar; there was no difference in any group between the 5- and 10-min values. The fall in red cell flux in normal skin of patients with sickle cell disease was smaller than in normal subjects when considered as a percentage of the control values (32%, 36%, 30% and 61% respectively in sickle cell patients with an active ulcer, with an ulcer scar and with no history of ulceration and in normal subjects), but in absolute terms the falls in red cell flux were similar in sickle cell patients and normal subjects. By contrast, the fall in red cell flux at the ulcer or scar site was greater than in normal skin from sickle cell patients whether considered as a percentage of the control value (48% and 49% respectively in those with an active ulcer or ulcer scar) or in absolute terms. 4. We propose that high resting perfusion is important in patients with sickle cell disease to maintain normal integrity of cutaneous tissue and that pronounced vasoconstriction on dependency hinders the healing and encourages recurrence of leg ulcers.

Reproducible Measurements to Quantify Cutaneous Involvement in Scleroderma

Because the current assessment of scleroderma through clinical skin scoring is subjective and imprecise, we devised fully quantitative measures of cutaneous involvement. First, we developed image analysis software for calculating the density of dermal collagen from 58 scleroderma and 327 control biopsy specimens. Second, using a durometer gauge, we obtained measurements of skin hardness over 12 body regions for 13 patients with scleroderma and 100 controls. We obtained serial durometer measurements at 2-cm intervals over the arms of four patients with scleroderma, correlating them with blinded assessments of skin score. Third, we produced two-dimensional laser Doppler maps of cutaneous blood flow over the dorsal aspect of the hands of 10 patients with scleroderma and 16 controls and, with software, we determined the mean red blood cell flux, density of arteriolar islands, and percentage of avascular area at each measured site. Average collagen density was significantly higher in patients with scleroderma (88.5% +/- 6.9%) compared with that in controls (75% +/- 9.3%) (P < .001). Durometer measurements were significantly greater for patients with scleroderma (P < .05) over the finger, hand, wrist, forearm, and ventral aspect of the arm. In individual patients, the measurements paralleled with skin score. In patients with scleroderma, mean red blood cell flux (483.2 +/- 421.2 mV) and arteriolar island density (1.4 +/- 0.5/cm2) were significantly greater than were the control averages (276.3 +/- 146.3 mV [P < .03] and 1.0 +/- 0.5/cm2 [P < .013], respectively). Dermal collagen density and durometer measurements of skin hardness accurately quantify skin sclerosis in scleroderma and permit the determination of sclerotic borders, respectively. Increased cutaneous red blood cell flux and greater use of microvascular reserve reflect defects in vascular regulation inherent to the disease. These reproducible measurements will allow us to more precisely monitor the progression of scleroderma, evaluate its response to experimental treatments, and investigate its pathogenetic origins.

Influence of intense sound stimuli on skin microcirculation

Sound influences not only the organ of hearing but also other systems including the circulation. The purpose of the present study was to investigate the effect of strong sound on the skin microcirculation of the palmar area of the hand and of the plantar area of the foot, which are areas of dense microvasculature and rich sympathetic innervation. The laser Doppler technique was used for measuring cutaneous red cell flux (RCF). Eighteen normal subjects were studied. The results indicate that a pure tone sound of 1500 Hz, with an intensity of 100 dBA and duration 5 s, applied by earphones caused a significant decrease in RCF in 14 out of 18 subjects in the finger but not in the foot skin. A higher intensity (110 dBA) tone caused a stronger decrease of RCF in the finger. The latency and the duration of the reaction showed a dependence on the intensity of the sound, i.e. the reaction to the stronger stimulus was of shorter latency (p < 0.01) and longer duration (p < 0.05). The duration of the reaction did not show significant change when a longer stimulus of 30 s was applied. Repetitive stimuli evoked habituation (p < 0.05).

Daily variability in resting levels of cardiovascular variables in normal subjects and those with homozygous sickle cell disease

Measurements were made of cardiovascular variables and oral temperature in 16 male subjects with homozygous sickle cell disease (SS) and in 17 matched controls (AA) at 10.00 a.m., 1.00 p.m. and 4.00 p.m. All subjects were in a rested state throughout. At 10.00 a.m., mean arterial pressure was lower, while heart rate, total forearm blood flow and cutaneous red cell flux in the forearm were higher in SS than AA. Vascular resistance in total forearm and forearm skin, calculated by dividing arterial pressure by blood flow or red cell flux, were lower in SS but hand cutaneous red cell flux and vascular resistance were not significantly different in SS and AA. In both SS and AA, there were parallel increases over the three sessions, in mean arterial pressure (by approximately 12 and 10%, respectively) forearm vascular resistance (by approximately 17 and 27%) and hand cutaneous vascular resistance and hand cutaneous resistance (by approximately 2240 and 350%) whereas forearm blood flow and hand cutaneous red cell flux fell. By contrast, forearm cutaneous resistance showed no change during the day in SS, but increased progressively in AA (by approximately 75%). These results indicate that, during the day, there is progressive vasoconstriction in forearm muscle and hand skin in SS and AA and also in forearm skin of AA that contributes to a progressive rise in the resting level of mean arterial pressure. We suggest this daily variability should be considered in studies of cardiovascular function: within a given study they should be performed at the same time of day.