Sidestream Dark Field (SDF) imaging: a novel stroboscopic LED ring-based imaging modality for clinical assessment of the microcirculation.

Sidestream Dark Field (SDF) imaging, a stroboscopic LED ring-based imaging modality, is introduced for clinical observation of the microcirculation. SDF imaging is validated by comparison to Orthogonal Polarization Spectral imaging. Nailfold capillary diameters and red blood cell velocities were measured using both techniques and equal quantitative results were obtained. An image quality system was developed to quantitatively compare the quality of sublingually-acquired microcirculatory images using OPS and SDF imaging. Venular contrast, sharpness, and quality were shown to be comparable for OPS and SDF imaging. However, capillary contrast and quality were shown to be significantly higher using SDF imaging. Venular granularity, in addition, was more clearly observable using SDF imaging.

The effect of storage time of human red cells on intestinal microcirculatory oxygenation in a rat isovolemic exchange model.

OBJECTIVE: To determine whether the storage time of human leukodepleted red blood cell concentrates compromises intestinal microvascular oxygen concentration oxygen (muPo(2)) during isovolemic exchange transfusion at low hematocrit. DESIGN: Prospective, randomized, controlled study. SETTING: University research institute laboratory. SUBJECTS: Male Wistar rats. INTERVENTIONS: Intestinal muPo(2) was determined by Pd-porphyrin phosphorescence life-time measurements. MEASUREMENTS AND MAIN RESULTS: Rats were brought near to a state of oxygen supply dependency by hemodilution with a pasteurized plasma protein solution to a hematocrit of 14.3 +/- 1.1% (n = 24). Subsequently, an isovolemic exchange transfusion with human leukodepleted red blood cells, stored for 2-6 days (fresh, n = 8), 2-3 wks (intermediate, n = 8), or 5-6 wks (old, n = 8), was performed to determine whether intestinal muPo(2) would be preserved. Immunologic reactions were avoided by washing the red blood cell concentrates three times before use. Isovolemic exchange with fresh and intermediate red blood cells maintained muPo(2) whereas old cells decreased muPo(2) with 26%. Subsequent transfusion with red blood cells (hematocrit approximately 60%) until reaching a hematocrit of 32.4 +/- 2.1 % (n = 24) increased intestinal muPo(2) in all three groups to the same extent between 28% and 32%. No changes in red blood cell deformability, as determined by a Laser-assisted Optical Rotational Cell Analyzer, could be demonstrated during 5 wks of storage. CONCLUSION: This study shows that at low hematocrit, the oxygen-delivering capacity of human red blood cells stored 5-6 wks is reduced compared with fresh cells and red blood cells stored for an intermediate period. Although red blood cells stored for 2-3 wks are completely devoid of 2,3-diphosphoglycerate, their oxygen-delivering capacity to the intestines was the same as fresh red blood cells. Our study showed that red blood cell deformability was preserved during storage, suggesting that other mechanisms may account for the observed decrease in oxygen delivery by red blood cells stored 2-3 wks.

Inhibition of the pentose phosphate pathway decreases ischemia-reperfusion-induced creatine kinase release in the heart.

OBJECTIVE: The oxidative pentose phosphate pathway (oxPPP) produces NADPH, which can be used to maintain glutathione in its reduced state (anti-oxidant; beneficial effects) or to produce radicals or nitric oxide (NO) through NADPH oxidase/NO synthase (detrimental effects). Changes in cytosolic redox status have been implicated in ischemic preconditioning (PC). This study investigates whether (1) PC affects mitochondrial redox state, (2) the oxPPP plays a protective or detrimental role in ischemia (I)-reperfusion (R) injury in the intact heart and (3) PPP is altered with PC. METHODS: Isolated rat hearts were subjected to 40-min global I and 30-min R (CO, control). Ischemia was either preceded by three 5-min I/R periods (PC) and/or oxPPP inhibition by 6-aminonicotinamide (6AN) or NADPH oxidase/NO synthase inhibition by diphenyleneiodonium (DPI). NADH videofluorometry was used to determine mitochondrial redox state. PPP intermediates were determined in CO and PC hearts using tandem mass spectrometry. RESULTS: PC reduced ischemic damage (creatine kinase, CK, release from 337+/-64 to 147+/-41 U/R/gdw) and contracture (from 59+/-5 to 31+/-3 mm Hg) and increased recovery of contractility (from 48+/-10% to 88+/-8%), as compared to CO. PC was without effect on NADH fluorometry. Inhibition of the oxPPP reduced injury (CK release: 91+/-24 U/R/gdw) to similar levels as PC, without improving contractility. Inhibition of NADPH oxidase/NO synthase mimicked the effects of oxPPP inhibition on injury (CK release: 140+/-22 U/R/gdw). Although levels of ribose-5P and (ribulose-5P+xylulose-5P) rose several fold during ischemia with minor changes in sedoheptulose-7P, demonstrating an active PPP in the heart, PC did not affect these levels. CONCLUSIONS: (1) PC can attenuate cardiac reperfusion injury without alterations in mitochondrial redox state; (2) inhibition of the oxPPP protects the heart against I/R-induced CK release; and (3) PC does not result in altered activity of the PPP.

Differences in peripheral arterial and venous hemorheologic parameters.

To evaluate the comparability of hemorheologic parameters in arterial and venous blood, we measured hematocrit, whole blood viscosity, plasma viscosity, erythrocyte deformability, erythrocyte aggregation, and erythrocyte indices in both arterial and venous blood from 20 consecutive patients scheduled for coronary artery surgery and/or valve replacement surgery. Hematocrit, whole blood viscosity at three shear rates (0.05 s-1, 0.5 s-1, and 70 s-1), plasma viscosity, and erythrocyte aggregation factor were statistically significantly higher in venous blood than in arterial blood. The differences may be explained by the difference in hematocrit. Erythrocyte deformability did not differ significantly. With the availability of more precise rheological measurement techniques, differences such as those encountered in this study may be of importance in clinical studies. It is concluded that arterial and venous blood samples are not entirely rheologically comparable.

Erythrocyte deformability, endothelin levels, and renal function in cyclosporin-treated renal transplant recipients: effects of intervention with fish oil and corn oil.

Twenty nine stable renal transplant recipients, 10 receiving cyclosporin, 10 cyclosporin-prednisolone and nine azathioprine-prednisolone were supplemented in a double blind randomization cross-over study with fish oil and corn oil for a period of 4 months each. Erythrocyte deformability was reduced in the cyclosporin-treated patients and returned to normal values after supplementation of either oil. The oil supplementation resulted in an increased polyunsaturated fatty acid content in the plasma phospholipids. An increased erythrocyte membrane polyunsaturated fatty acid content might correct the lower erythrocyte deformability in cyclosporin treated patients. Therefore, it is probable that these changes are membrane-related. The oil supplementation had no effect on glomerular filtration rate, effective renal plasma flow, filtration fraction or blood pressure, which does not exclude effects of the cyclosporin-induced rigidified erythrocytes in the acute phase of renal transplantation. Decreased erythrocyte deformability could play a role in the cyclosporin-induced deterioration of renal haemodynamics. This may enhance the effects of endothelin, as these patients also had elevated endothelin levels.

Transient aggregation resistance of human blood platelets in fresh plasma. II. Physiological relevance: influence of fish oil.

In order to evaluate the physiological relevance of the blood platelet "transient aggregation resistance" (TAR) test we studied the effect on this test of two different amounts of fish oil, corresponding to .75 g g (2.5 mmol) and 1.5 g (5 mmol) of eicosapentaenoic acid respectively, added in a cross-over design to the normal diet of 16 healthy male volunteers. It appeared that the "baseline aggregation resistance" (BAR), equivalent to the classic platelet aggregation ADP-threshold, was not influenced by Maxepa while, in contrast, a significant prolongation of TAR occurred. Apparently platelet aggregation analysed early after blood withdrawal, measures aspects of physiological relevance which, due to their short half life, are missed in the original method.

Transient aggregation resistance of human blood platelets in fresh plasma. I. Methodology.

A novel analytical method, using turbidometry, for reporting the time-dependent decay in the threshold concentration of adenosine diphosphate (ADP), required to elicit a secondary aggregation response in fresh human citrated platelet-rich plasma (PRP), is described. The phenomenon, called "transient aggregation resistance" (TAR) ends, usually within one hour after venepuncture, in a steady state or "baseline aggregation resistance" (BAR). Back extrapolation of the mathematically transformed data to t = 0, yields a maximal threshold concentration of ADP, representing the initial aggregation resistance (TARmax) at the time of blood withdrawal, which threshold is usually many orders of magnitude higher than the BAR-value. The exponential decay of TAR can be characterized by its half-life (t1/2). Mixing fresh, rapidly prepared, plasma with PRP, kept long enough to show only the stable low BAR-value, could restore the initial high (transient) aggregation resistance found in fresh PRP, suggesting that it concerns a natural, labile plasmatic factor. One hour old PRP, deliberately made refractory to ADP, did not show the TAR phenomenon again, but had a higher BAR-value. It is suggested that the level of clinical relevance of these early in vitro aggregation measurements is higher than that of classical, delayed aggregometry (e.g. BAR-values).

Relationship between blood viscosity and cerebral ischemia after surgical treatment of ruptured intracranial aneurysms.

To determine the role of blood viscosity after surgical treatment of ruptured intracranial aneurysms, the relationship between blood viscosity and clinical condition was examined in 17 patients. A total of 213 blood samples were analyzed. An inverse correlation was found between blood viscosity and level of consciousness; in addition, blood viscosity was higher when focal neurologic deficit was observed. Hematocrit was similarly related to clinical condition, although the correlations observed were less strong. Postoperative plasma viscosity was higher in patients with focal neurologic deficit. Regular blood viscosity measurements are of value in patients at risk for developing cerebral ischemia.

Demonstration of labile platelet desaggregation-promoting substance(s) in human blood, using the donor's own blood platelets ("DOP assay") as indicator cells, with special reference to the possibility of measuring diet-induced alterations.

A method is described for the semi-quantitative biological determination of labile platelet desaggregation-promoting substance(s) in human platelet suspensions and in platelet-free fresh plasma by using the donor's own platelets ("DOP assay"). Using the donor as his own control it is possible to demonstrate a dose-related increase of the platelet desaggregation-promoting potency in response to cod-liver oil. The labile platelet desaggregation-promoting activity can also be observed in fresh platelet-free plasma. Circumstantial evidence is presented for the prostaglandin-like nature of these labile platelet desaggregation-promoting substance(s).