The purpose of the present study was to compare the effects of endothelium-dependent acetylcholine (ACh) and endothelium-independent sodium nitroprusside (SNP) vasodilators on the oscillatory ...components of the cutaneous blood perfusion signals in humans. The unstimulated basal blood perfusion and the blood perfusion during iontophoretically delivered ACh and SNP were measured using laser Doppler flowmetry (LDF). The wavelet transform was calculated before spectral analysis of the measured signals. In the frequency interval from 0.0095 to 1.6 Hz the LDF signal consists of oscillations with five different characteristic frequencies. In addition to the cardiac (1 Hz) and respiratory (0.3 Hz) rhythms, three other oscillations in the regions around 0.1, 0.04, and 0.01 Hz were detected. The oscillations with the different frequencies were observed in unstimulated blood flow and also during stimulation with ACh and SNP. Compared to the unstimulated blood flow, both ACh and SNP increased the mean amplitude of the total spectrum (P< 0.005 for both substances). The only significant difference between the effects of ACh and SNP was observed in the amplitude of oscillations with the frequency of around 0.01 Hz. ACh increased the absolute amplitude of this frequency to a greater extent than SNP in athletes (P= 0.03), whereas only a trend was observed in controls (P= 0.2). The relative amplitude, defined as the ratio between the absolute amplitude of a particular frequency interval and the mean amplitude of the total spectrum, was also higher for ACh compared to SNP both in controls (P= 0.008) and in athletes (P= 0.004), only for oscillations with the frequency of around 0.01 Hz. We conclude that ACh selectively influences the oscillatory component of around 0.01 Hz in the cutaneous blood perfusion signal to a greater extent than SNP. This finding indicates that endothelium-mediated vasodilatation is manifested as oscillations with a repetition time of approximately 1 min. The mechanisms for the endothelial dependency of this frequency remain to be elucidated. Our data indicate that spectral analysis based on wavelet transform of the cutaneous perfusion signal can be used clinically to investigate endothelial function. The described noninvasive method might be used to evaluate endothelial function for research, for diagnostic purposes, and maybe also to assess effects of therapy in cardiovascular diseases.
Erythromelalgia is a clinical diagnosis characterized by erythema, increased temperature and burning pain in acral skin. The pain is relieved by cooling and aggravated by warming. The symptoms have ...been hypothesized to be caused by skin hypoxia due to increased arteriovenous shunting. We examined skin microvascular perfusion in response to vasoconstrictory and vasodilatory stimuli, to characterize local and central neurogenic reflexes as well as vascular smooth muscle and vascular endothelial function, using laser Doppler perfusion measurements in 14 patients with primary erythromelalgia and healthy control persons. Skin perfusion preceding provocative stimuli was significantly reduced in patients with erythromelalgia (p < 0.01). The laser Doppler flowmetry signal after sympathetic stimulation of reflexes mediated through the central nervous system, was significantly diminished in patients with erythromelalgia as compared with healthy controls (Valsalva's maneuver p < 0.01; contralateral cooling test p < 0.05). Local neurogenic vasoconstrictor (venous cuff occlusion and dependency of the extremity) and vasodilator reflexes (local heating of the skin), as well as tests for vascular smooth muscle and vascular endothelial function (postocclusive hyperemic response) were maintained. These results indicate that postganglionic sympathetic dysfunction and denervation hypersensitivity may play a pathogenetic role in primary erythromelalgia, whereas local neurogenic as well as endothelial function is unaffected.
Non-invasive imaging techniques are increasingly used to objectively quantify anterior segment structures of the eye. In this study, we apply the novel oxygen delivery index (ODIN) concept that, ...quantifies microvascular capacity for oxygen delivery, to the ocular surface in healthy humans.
The purpose of the study was to test the applicability of the technologies used for data acquisition from the human ocular surface. We also validated whether the ODIN concept has sufficient sensitivity to detect and differentiate between microvascular structure and function in limbal and bulbar conjunctiva.
Multiple ocular surface measurements using computer-assisted video microscopy (field of view: 1.6 mm × 0.9 mm) and diffuse reflectance spectroscopy (measuring volume: ∼0.1 mm3) were obtained from limbal and bulbar conjunctiva in 20 healthy volunteers. Three parameters were extracted during analyses: Functional capillary density, capillary flow velocity, and microvascular oxygen saturation.
Functional capillary density was higher at limbus than in bulbar conjunctiva (11.2 ± 1.8 c/mm versus 5.2 ± 1.2 c/mm, p < 0.01), and microvascular oxygen saturation was lower at limbus (77 ± 8%) as compared to bulbar conjunctiva (89 ± 6%), p < 0.01. More than 80% of scored capillaries had continuous blood flow and no difference was seen between the recording sites (p = 0.68).
In conclusion, the ODIN concept is applicable for the assessment of human ocular surface microvascular function and has sufficient sensitivity to detect increased capillary density and oxygen extraction at limbus as compared with bulbar conjunctiva.
Erythromelalgia is characterized by burning pain, erythema, and increased temperature in acral skin. The pain is aggravated by warming and relieved by cooling. Increased microvascular arteriovenous ...shunting in deep dermal plexa has been hypothesized as the pathogenetic mechanism of pain in affected skin, inducing hypoxia during pain attacks. The aim of this study was to quantify skin capillary density in erythromelalgic patients before and after heat provocation, as increased skin temperature should increase the need for nutritive blood supply by the capillaries. Fourteen patients and 10 healthy control subjects were studied using an enhanced technique of computer-assisted analysis of capillary bed morphology and temperature measurements before and after central body heating. The increase in acral skin temperature was significantly higher (p <0.05) in the eight patients where symptoms were induced after heat provocation, compared to asymptomatic patients and healthy control subjects. The number of visible capillaries in a field of view (1.7 mm2) decreased significantly (p =0.01) in erythromelalgia patients from 105 (62–137) (median with total range) to 89 (49–118) after warming in areas with numerous arteriovenous anastomoses (nail bed region). In symptomatic patients an even more significant reduction was observed (p =0.01). The capillary size was also significantly reduced (p <0.05) from 41.0 (31.5–50.5) (arbitrary units) to 37.3 (33.0–46.0) in symptomatic patients. The change in capillary density in the nail bed area was significantly larger in erythromelalgia patients -17 (-49 to 39) compared to controls 0 (-47 to 13) (p <0.05), and in symptomatic patients -19 (-49 to -12) compared to asymptomatic patients -8 (-48 to 39) (p <0.05) and controls (p <0.01). The reduced skin capillary density after heating is compatible with increased microvascular arteriovenous shunting of blood and a corresponding relative deficit in nutritive perfusion (steal phenomenon) with skin hypoxia, causing the symptoms in erythromelalgia.
Objective
Clinical assessments and laser Doppler perfusion measurements (LDPM) of skin microcirculation have limited value, as they fail to capture events regulated by local metabolic needs at a ...papillary capillary level. This study aimed to examine the ability of computer‐assisted video microscopy (CAVM) and diffuse reflectance spectroscopy (DRS) to assess skin nutritive perfusion—compared to LDPM.
Methods
Healthy volunteers (n = 10) were examined after (≈1 and ≈24 h) an incision (5 × 1 mm) on the forearm, at 0.1 mm (only with CAVM), 2−3 mm, and 30 mm from the trauma.
Results
No changes were detected by CAVM after ≈1 h. After ≈24 h, 0−1 mm from the trauma, both CAVM parameters were increased: functional capillary density (capillary crossings/mm, 11.8 ± 1.4 vs. 7.3 ± 1.2, p < .01) and capillary flow velocities (CFV, %capillaries with brisk flow, 10 ± 6.8 vs. 1 ± 1, p < .01). At a distance of 2−3 mm, only CFV was increased (6.2 ± 6.1 vs. 1 ± 1, p < .05). DRS and LDPM measurements increased 2−3 mm from the trauma line in relation to baseline after both ≈1 and ≈24 h, that is, with DRS (%microvascular oxygen saturation): 45.8 ± 7.4% (baseline), 70.0 ± 12.5% (≈1 h), and 73.1 ± 10.4% (≈24 h), p < .01 and with LDPM (a.u.): 7.2 ± 2.5 (baseline), 28.3 ± 18.7 (≈1 h), and 45.9 ± 16.3 (≈24 h), p < .01.
Conclusions
≈24 h after skin trauma, an increased function of the nutritive papillary capillaries can be detected by CAVM.
Microvascular remodeling following skin injury Wikslund, Liv Kristin; Kaljusto, Mari‐Liis; Amundsen, Vivian Shubira ...
Microcirculation,
October 2022, Volume:
29, Issue:
6-7
Journal Article
Peer reviewed
Open access
Objective
The aim of this study was to describe possible remodeling (i.e., dilatation and elongation) of papillary capillaries induced by increased oxygen demand for the repair process following a ...skin wound.
Methods
Computer‐assisted video microscopy was used to examine 10 healthy volunteers before (baseline) and after (≈1 h and ≈24 h) an incision (5 mm long and 1 mm deep) on the forearm, 0–1 mm and 30 mm (control site) from the incision. We defined categories from 0 (low) to 3 (high) to grade dilatation and elongation of the nutritive papillary capillaries, as well as the visibility of the superficial vascular plexus. Approximately 10 000 capillaries from 200 films were scored.
Results
The nutritive papillary capillaries were dilated and elongated (p < 0.01) after ≈24 h; that is, elongation (score 1.9 ± 0.9) vs baseline (score 0.9 ± 0.6), p < 0.01 and dilatation (score 2.2 ± 0.7) vs baseline (score 0.3 ± 0.3), p < 0.01. Superficial plexus visibility increased (p < 0.01) after ≈1 h (score 2.0 ± 0.7) and ≈24 h (score 2.7 ± 0.3) vs baseline (score 0.8 ± 0.4).
Conclusion
The superficial vascular skin plexus showed enhanced visibility already ≈1 h after the skin trauma. Morphological remodeling in the nutritive papillary capillaries—dilatation and elongation after ≈24 h—facilitate increased O2 supply.
Background
Non‐pulsatile cardiopulmonary bypass (CPB) may induce microvascular dysregulation. In piglets, we compared ocular surface microcirculation during pulsatile versus continuous flow (CF) ...bypass.
Methods
Ocular surface microcirculation in small tissue volumes (~0.1 mm3) at limbus (high metabolic rate) and bulbar conjunctiva (low metabolic rate) was examined in a porcine model using computer assisted video microscopy and diffuse reflectance spectroscopy, before and after 3 and 6 h of pulsatile (n = 5 piglets) or CF (n = 3 piglets) CPB. Functional capillary density, capillary flow velocity and microvascular oxygen saturation were quantified.
Results
At limbus, velocities improved with pulsatility (p < 0.01) and deteriorated with CF (p < 0.01). In bulbar conjunctiva, velocities were severely reduced with CF (p < 0.01), accompanied by an increase in capillary density (p < 0.01). Microvascular oxygen saturation decreased in both groups.
Conclusion
Ocular surface capillary densities and flow patterns are better preserved with pulsatile versus CF during 6 h of CPB in sleeping piglets.
Non‐pulsatile cardiopulmonary bypass (CPB) may induce microvascular dysregulation. In sleeping piglets, we found that ocular surface microcirculation is better preserved with pulsatile versus continuous flow during a 6 h cardiopulmonary bypass procedure.
Background: Non- pulsatile cardiopulmonary bypass (CPB) may induce micro-vascular dysregulation. In piglets, we compared ocular surface microcirculation during pulsatile versus continuous flow (CF) ...bypass.Methods: Ocular surface microcirculation in small tissue volumes (~0.1 mm3) at limbus (high metabolic rate) and bulbar conjunctiva (low metabolic rate) was ex-amined in a porcine model using computer assisted video microscopy and diffuse reflectance spectroscopy, before and after 3 and 6 h of pulsatile (n = 5 piglets) or CF (n = 3 piglets) CPB. Functional capillary density, capillary flow velocity and microvascular oxygen saturation were quantified.Results: At limbus, velocities improved with pulsatility (p< 0.01) and deterio-rated with CF (p< 0.01). In bulbar conjunctiva, velocities were severely reduced with CF (p< 0.01), accompanied by an increase in capillary density (p< 0.01). Microvascular oxygen saturation decreased in both groups.Conclusion: Ocular surface capillary densities and flow patterns are better pre-served with pulsatile versus CF during 6 h of CPB in sleeping piglets.
Anastomotic leakage is a common complication following large abdominal surgery, often developing to life-threatening abdominal sepsis due to late diagnosis. Currently, diagnostics rely on systemic ...hemodynamic and infection monitoring. We hypothesized that intraperitoneal microdialysis allows detection of peritonitis prior to changes in standard clinical parameters in a pig model.
We included six pigs; five underwent intraperitoneal fecal contamination, one had sham surgery for a total of 10 h. Microdialysis was established in four intraabdominal quadrants and two hepatic lobes. All pigs were hemodynamically monitored with pulmonary artery and femoral artery catheters. Blood samples were assessed for inflammatory markers, terminal complement complex (TCC), interleukin (IL)-6, IL-10, and plasminogen activator inhibitor-1 (PAI-1).
Microdialysis showed intraperitoneal lactate increase during the first two hours after fecal contamination, which remained elevated throughout the observation time with concurrent decrease of glucose. Arterial lactate remained within reference range (<1,6mM). Systemic inflammatory markers TCC, IL-6, IL-10 and PAI-1 increased significantly after minimum four hours. Mean arterial pressure, stroke volume variation and cardiac output were not compromised the first five hours. Sham surgery did not influence any of the parameters.
Intraperitoneal fecal contamination leads to a rapid and pronounced intraperitoneal increase in lactate, decrease in glucose while pyruvate and glycerol levels remain unchanged. This distinct metabolic pattern of peritoneal inflammation can be easily detected by microdialysis. Observation of this pattern may minimize time to safe diagnosis of intestinal perforations after intraperitoneal fecal contamination.
In piglets we tested the applicability of digital video microscopy and diffuse reflectance spectroscopy for non-invasive assessments of limbal and bulbar conjunctival microcirculation. A priori we ...postulated that the metabolic rate is higher in limbal as compared to bulbar conjunctiva, and that this difference is reflected in microvascular structure or function between the two locations. Two study sites, Oslo University Hospital (OUH), Norway and Cleveland Clinic (CC), USA, used the same video microscopy and spectroscopy techniques to record limbal and bulbar microcirculation in sleeping piglets. Recordings were analyzed with custom-made software to quantify functional capillary density, capillary flow velocity and microvascular oxygen saturation in measuring volumes of approximately 0.1 mm3. The functional capillary density was higher in limbus than in bulbar conjunctiva at both study sites (OUH: 18.1 ± 2.9 versus 12.2 ± 2.9 crossings per mm line, p < 0.01; CC: 11.3 ± 3.0 versus 7.1 ± 2.8 crossings per mm line, p < 0.01). Median categorial capillary blood flow velocity was higher in bulbar as compared with limbal recordings (CC: 3 (1–3) versus 1 (0–3), p < 0.01). Conjunctival microvascular oxygen saturation was 88 ± 5.9% in OUH versus 94 ± 7.5% in CC piglets.
Non-invasive digital video microscopy and diffuse reflectance spectroscopy can be used to obtain data from conjunctival microcirculation in piglets. Limbal conjunctival microcirculation has a larger capacity for oxygen delivery as compared with bulbar conjunctiva.
•Digital microscopy and spectroscopy can record microvascular data from conjunctiva.•Analyzed results quantify oxygen delivery from capillaries.•Capacity for capillary oxygen delivery is higher in limbus compared with bulbus.
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