摘要:

The importance of the dynamic nature of perfusion pressure within the peripheral microcirculation is increasingly recognised. Capillary pressure is determined not only by arterial inflow pressure, but is also subject to a variety of local and systemic influences which have been shown to affect both mean pressure and the capillary pulse waveform. To what extent changes in central pulse waveform influence capillary pressure has yet to be determined. By using a dynamic technique of capillary pressure measurement in human subjects with aortic stenosis, we have been able to show that the characteristics of the pulse waveform typically associated with large vessels in this condition are also readily detectable at a capillary level despite local influences. However, changes in the rate of pulse wave transmission described in large arteries were not apparent at a microvascular level. Unlike mean capillary pressure and capillary pulse pressure, pulse waveform in the capillary mimics central haemodynamics.

ISSN:0167-6865    

DOI:10.1159/000178837

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Disturbed hemodynamic reactions to insulin-induced hypoglycemia have been documented in diabetic patients and considered related to hyperinsulinemia and impairment of autonomic nervous functions. In the present study we investigated the effect on skin microcirculation of insulin-induced hypoglycemia obtained during moderate hyperinsulinemia, in 7 men with type 1 diabetes and in 8 healthy age- and sex-matched controls. The patients had all normal cardiovascular reflexes as assessed by respiratory sinus arrhythmia and Valsalva ratio. The skin microcirculation of the left fourth finger nailfold was investigated by laser Doppler fluxmetry, and the skin temperature within the same area was measured by a thermistor. Hypoglycemia was induced by a constant insulin infusion of Actrapid Human®, 0.034 U kg-1 h-1 during 120 min. Plasma adrenaline, noradrenaline and pancreatic polypeptide increased significantly in both groups during hypoglycemia and the insulin levels never exceeded 50 mU1-1. A close to identical arterial hypoglycemia was obtained in the two groups 60 min after onset of insulin infusion. During hypoglycemia the control subjects revealed a significant decrease in laser Doppler flux (p < 0.025), while it was unchanged in the diabetic patients. Simultaneously, the skin temperature decreased (p < 0.05) in the controls, but was unchanged in the diabetic patients. The present study indicates that type 1 diabetic patients with normal cardiovascular reflexes have an abolished vasoconstrictor response in skin microcirculation of fingers during insulin-induced hypoglycemia, despite the fact that neurogenic and neuroglucopenic symptoms developed in these patients during hypoglycemia

ISSN:0167-6865    

DOI:10.1159/000178838

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

A newly designed triple probe is introduced for measurements of transcutaneous oxygen tension, laser Doppler flowmetry (LDF) and microangiodynamics of skin capillaries by dynamic video microscopy with and without fiuorochromes. The performance of the triple probe was checked in 9 healthy volunteers (6 women, 3 men; mean age: 34 years) and 9 patients (5 women, 4 men; mean age: 67 years) with peripheral arterial occlusive disease (PAOD). The mean Doppler ankle/arm pressure ratio was 0.54 ± 0.30. Six patients suffered from severe claudication, 2 from rest pain and 1 patient had toe and forefoot necrosis. The foot dorsum was selected as measuring site. After recording baseline values of skin surface PO2 (ssPO2) at 37°C, LDF and capillary images, a suprasystolic compression at the ankle level was performed for 4 min. Thirty seconds before cuff opening 0.2 ml/l1 blood volume of 20% sodium fluorescein was injected in an antecubital vein. Sodium fluorescein arrival times, filling times and maximum fluorescent light intensity times were measured, and ssPO2 and LDF were recorded continuously during postocclusive reactive hyperemia (PORH). The results indicate an adequate function of the triple probe. The mean resting ssPO2 was 2.0 ± 1.9 mm Hg in PAOD patients and 4.0 ± 3.9 mm Hg in controls (p = 0.185). Maximum SSPO2 during PORH was significantly reduced (p = 0.008) in patients (3.1 ± mm Hg) compared to healthy subjects (11.8 ± 7.7 mm Hg). Resting LDF values were 6.5 ± 6.4 perfusion units (PU) in PAOD patients versus 10.3 ± AU in controls (p = 0.295). Peak LDF during PORH was significantly reduced (p = 0.005) in patients (19.5 ± 6.4 PU) versus healthy subjects (33.8 ± 11.5 PU). The mean sodium fluorescein appearance time and maximum fluorescent light intensity time during PORH were significantly delayed (p = 0.006; p = 0.003) in PAOD patients (11.1 ± 9.0 s; 330.6 ± 69.4 s) versus healthy subjects (1.6 ± 0.9 s; 220.7 ± 60.6 s), respectively. Microvascular flow distribution during PORH estimated by the mean sodium fluorescein filling time was not different in both groups. The main advantage of the combined device is the simultaneous performance of all three techniques at the almost identical sensing site under the same measuri

ISSN:0167-6865    

DOI:10.1159/000178839

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:0167-6865    

DOI:10.1159/000178840

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Oxygen saturation of hemoglobin (HbSO2) in skin vessels may be determined with photometric methods. However, the optical complexity of the skin makes quantitative measurements difficult. A possible approach is the analysis of reflectance spectra using the two-flux theory of Kubelka and Munk. The final equation of this theory which describes the transformation between absorbed and reflected light has been approximated by a hyperbola. Based on this approximation we evaluated skin spectra obtained from the forearm of 23 healthy subjects with a fast scanning reflection photometer (Oxyscan) applying visible light (535-620 nm). The hyperbola was used in a multicomponent analysis in which the measured spectrum is recalculated using reference spectra of oxygenated and deoxygenated hemoglobin (gaussian least-square method). A crucial requirement for the evaluation is the subtraction of the individual skin spectrum, obtained by clearing a spot of skin of hemoglobin exerting external pressure. At rest HbSO2 was in the range between 42 and 89% (mean ± SD:72.9 ± 12.2%). Pharmacological and thermal generation of hyperemia combined with respiration of pure oxygen raised the values to 86-100% (97.9 ± 4.6%). This was in good agreement with capillary ex vivo analysis yielding 96-100% (98.7 ± 0.4%). Under arterial occlusion HbSO2 fell below 30% (14.5 ± 7.8%). Our method allows rapid determinations of absolute HbSO2 values in the skin. The evaluation error is estimated to be between 5% for oxygenated and 10% for deoxygenated va

ISSN:0167-6865    

DOI:10.1159/000178841

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Due to the high flexibility of the micro-light guides used with the Erlangen micro-light guide spectrophotometer (EMPHO) the instrument can be coupled to the lung surface without interfering with the local lung mechanics. The local pressure exerted on the lung varies between 45 and 47 mg/cm2. This enables the continuous investigation of local haemoglobin oxygenation and relative local haemoglobin concentration. The effect of different inspired oxygen concentrations on local oxygen saturation of intravascular haemoglobin and relative local haemoglobin concentration was investigated in 6 rabbits. The animals were anaesthetized, intubated and artificially ventilated. After thoracotomy, a light guide was placed on the pleural lung surface and haemoglobin spectra were measured at a frequency of 5 Hz using the EMPHO. Two types of changes in the local haemoglobin concentration were observed; one was correlated with the respiratory cycle. During inspiration a decrease in relative local haemoglobin concentration was observed. Opposite changes occurred during expiration. These changes were observed with simultaneous changes in local haemoglobin oxygenation. The oxygenation increased during inspiration and decreased during expiration. The amplitude of the oxygenation changes depended on the fraction of inspired oxygen FiO2 A second type of reaction in local haemoglobin concentration was observed when the inspired oxygen concentration was decreased or increased by changing the FiO2. A decrease in the oxygen partial pressure in the inspired gas mixture (PiO2) was associated with an increase in relative local haemoglobin concentration, whereas an increase in PiO2 was accompanied by a decrease in relative local haemoglobin concentration. The hypoxic increase could be due to an increase in perfusion in the upper part of the lung induced by a hypoxic pulmonary hypertension.

ISSN:0167-6865    

DOI:10.1159/000178842

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The dynamic changes in microcirculation were investigated with laser Doppler flowmetry in two selected regions of interest (ROI) of a stroke lesion during ischemia and early reperfusion using a rat model of temporary middle cerebral artery (MCA) occlusion. In each ROI measurements were made either during 30 min or 2 h of MCA occlusion followed by 1 h of reperfusion. On the periphery of the MCA territory, an area of mild ischemia with a mean reduction of flow to 38% (39.9% in the group with 30 min MCA occlusion and 35.9% in the group with 2 h MCA occlusion) of preischemic values was demonstrated. Closer to the center of the MCA territory, more severe ischemia with a mean reduction of flow to 21 % (19.9% in the 30-min group and 22.9% in the 2-hour group) was seen. In the two groups with laser Doppler flowmetry in the ROI of mild ischemia, a compensatory increase in flow during the first 3-6 min after MCA occlusion could be seen. All rats displayed a peak hyperperfusion immediately after re-establishing of flow which then stabilized above, below, or equal to the preischemic level. This peak hyperemia was most abundant in the group in which flow was measured in the ROI of more severe ischemia after the 30-min MCA occlusion. In the same area a short hyperemic peak was followed by a significant hypoperfusion of 60% of preischemic flow after 2 h of MCA occlusion. In the groups with flow measurements in the ROI of mild ischemia, there was a return to preischemic flow after the 30-min ischemia and a tendency of preserved hyperemia after 2 h of MCA occlusion.

ISSN:0167-6865    

DOI:10.1159/000178843

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:0167-6865    

DOI:10.1159/000178844

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

With the use of intravital fluorescence microscopy and the dorsal skinfold chamber model we studied the effect of buflomedil hydrochloride on micro-vascular reperfusion injury after 4 h of tourniquet-induced ischemia in hamster striated muscle. Animals (n = 15) received 3 mg/kg buflomedil (i.v. bolus) 5 min before onset of reperfusion, and 3 mg/kg buflomedil (continuous i.v. infusion) during the first 20 min of reperfusion. Animals (n = 13) receiving equivalent volumes of saline served as controls. Tourniquet-induced ischemia resulted in (a) a marked decrease of functional capillary density and (b) accumulation and adherence of leukocytes in postcapillary venules after 30 min and 2 h of reperfusion. This was associated with an increased microvascular permeability (leakage of macromolecules), reflecting the alteration of endothelial cell integrity. Treatment with buflomedil significantly reduced both postischemic capillary perfusion failure and leukocyte adherence in venules. Concomitantly, the increase of microvascular permeability in postcapillary venules was almost prevented, indicating the beneficial effect of buflomedil on the manifestation of microvascular reperfusion injury following tourniquet ischemia in striated muscle.

ISSN:0167-6865    

DOI:10.1159/000178845

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The aim of this study was to investigate the characteristics of the microcirculatory blood flow with laser-Doppler fiowmetry (LDF) in skeletal muscle during both regional and systemic infusions of adenosine. A laser-Doppler flowmeter probe was placed on the left gastrocnemius muscle in anesthetized rats. Adenosine was given either systemically in the jugular vein (group A) or administered regionally in the iliac artery (group B). The infusion of adenosine was increased stepwise by 50 µg/kg/min, every 10 min, up to 400 µg/kg/min. In group A there was a dose-dependent decrease in mean arterial pressure as well as in LDF flow; flowmotion of the LDF signal with a frequency of 1.6 cycles/ min was seen at a mean adenosine dose of 240 µg/kg/min at a blood pressure of 60 mm Hg. In group B there was a dose-dependent decrease of mean arterial blood pressure but not as marked compared to group A, meanwhile the LDF flow was unchanged; flowmotion was seen at a mean adenosine dose of 220 µg/kg/min at a blood pressure of 72 mm Hg, with a frequency of 1.5 cycles/min. This study demonstrates that adenosine, given either regionally intraarterially with maintained blood flow, or intravenously with reduced blood flow, induces flowmotion in skeletal muscle microcirculation with a frequency of approximately 1.5 cycles/

ISSN:0167-6865    

DOI:10.1159/000178846

出版商:S. Karger AG    

年代:1994

数据来源: Karger