Relevance of culturing Candida species from intravascular catheters

The significance of isolating Candida species from intravascular catheters was examined retrospectively. Our findings demonstrate that these organisms are encountered among patients with proven invasive candidiasis or as an isolated finding. Febrile patients with yeasts in two or more additional sites may be at risk for invasive cadidiasis and may benefit from treatment.     

Oral verapamil inhibits platelet thrombus formation in humans

BACKGROUND: Calcium antagonists such as verapamil are potent coronary and systemic vasodilators that are used in the treatment of coronary disease. They have also been shown to inhibit platelet aggregation in vitro, but whether they have beneficial antithrombotic effects in humans is unclear, and whether they can potentiate the antithrombotic effects of aspirin is unknown. METHODS AND RESULTS: Platelet thrombus formation and whole blood platelet aggregation were measured in 18 stable coronary patients on three separate occasions: at baseline when receiving no active medications, after 7 days of receiving oral verapamil SR (240 mg/d), and after 7 days of receiving a combination of oral verapamil SR and aspirin (325 mg/d). Thrombus formation on porcine aortic media that were placed into cylindrical flow chambers and exposed to flowing antecubital venous blood for 3 minutes was assessed morphometrically at a shear rate of 2546 s-1, which is typical of arterial flow at sites of stenoses. Thrombus formation under basal conditions was 7.0 +/- 1.6 microns 2, and this was decreased to 3.1 +/- 0.5 microns 2 (P < .05) after 7 days of treatment with oral verapamil SR and to 2.6 +/- 0.5 microns 2 (P < .05) after 7 days of treatment with oral verapamil and aspirin. Whole blood platelet aggregation levels in response to 0.050 and 0.075 U of thrombin at baseline were 10.8 +/- 1.0 and 11.9 +/- 1.0 omega; aggregation was inhibited after 7 days of treatment with verapamil to 6.5 +/- 1.1 and 7.8 +/- 0.9 omega (P < .05 versus baseline) and after 7 days of treatment with verapamil and aspirin to 6.1 +/- 1.1 and 7.2 +/- 1.0 omega (P < .05), respectively. CONCLUSIONS: The present study demonstrates that part of the benefit of verapamil in ischemic heart disease may occur by inhibition of platelet aggregation and thrombus formation. This beneficial antithrombotic effect may be important in preventing acute coronary ischemic events resulting from thrombus formation at sites of plaque rupture.     

Crystalline cholesterol as a factor in thrombus formation

The model using crystalline cholesterol as the thrombogenic process inductor was developed. Thrombi that are morphologically equivalent to the human arterial thrombi under atherosclerosis were created in experiment on standard animals. It was shown that the "head" (conglutinational part) of such thrombi includes the thrombocyte mass, organised into the system of branched trabeculae surrounded by leucocytal limbus. The "caudal" (coagulational part) of the experimentally obtained thrombi consists of fibrin and erythrocytes. Data obtained make it possible to consider crystalline cholesterol of atheromatous plaques as the most probable trigger factor of thrombogenesis during atherosclerotic process.     

Intracardial thrombus formation in heparin-associated thrombocytopenia type II

Deep vein thrombosis of the right leg occurred in a 77-year-old woman after percutaneous cardiac catheterization via the right femoral vein, performed to assess mitral valve disease with atrial fibrillation. She thereupon received intravenous heparin (1,000 IU/h; partial thromboplastin time 60-70s). 13 days later she developed a transient incomplete right brachiofacial hemiparesis with motor aphasia. Transthoracic echocardiography revealed a fresh left atrial thrombus. Platelet count fell from initially normal levels to 20 x 10(9)/l. Because type II heparin-associated thrombocytopenia was suspected heparin administration was discontinued and phenprocoumon administered. Heparin-dependent antibodies were demonstrated with the heparin-induced platelet activation test. Cross reactions occurred in vitro against all low-molecular heparins and heparinoid ORG 10172. The platelet count had become normal 17 days later, the leg veins had recanalized and the intraatrial thrombus had become much smaller. The patient declined cardiac surgery and was discharged on the 41st hospital day in satisfactory general condition on maintenance anticoagulant dosage.     

Inhibitory effect of piracetam on platelet-rich thrombus formation in an animal model

Intravenous administration of piracetam to hamsters reduced the formation of a platelet-rich venous thrombus induced by a standardised crush injury, in a dose-dependent fashion with an IC50 of 68 +/- 8 mg/kg. 200 mg/kg piracetam also significantly reduced in vivo thrombus formation in rats. However, in vitro aggregation of rat platelets was only inhibited with piracetam-concentrations at least 10-fold higher than plasma concentrations (6.2 +/- 1.1 mM) obtained in the treated animals. No effects were seen on clotting tests. In vitro human platelet aggregation, induced by a variety of agonists, was inhibited by piracetam, with IC50's of 25-60 mM. The broad inhibition spectrum could be explained by the capacity of piracetam to prevent fibrinogen binding to activated human platelets. Ex vivo aggregations and bleeding times were only minimally affected after administration of 400 mg/kg piracetam i.v. to healthy male volunteers, resulting in peak plasma levels of 5.8 +/- 0.3 mM. A possible antiplatelet effect of piracetam could be due to the documented beneficial effect on red blood cell deformability leading to a putative reduction of ADP release by damaged erythrocytes. However similarly high concentrations were needed to prevent stirring-induced "spontaneous" platelet aggregation in human whole blood. It is concluded that the observed antithrombotic action of piracetam cannot satisfactorily be explained by an isolated direct effect on platelets. An additional influence of piracetam on the rheology of the circulating blood and/or on the vessel wall itself must therefore be taken into consideration.     

Coronary thrombosis. Effects of blood flow on the mechanism of thrombus formation

The mechanism of arterial thrombosis, including coronary thrombosis, is different from that of thrombosis which occurs at sites of blood stasis such as deep venous thrombosis. Considering the onset of arterial thrombus formation, soluble coagulant factors may not play important roles for its onset since they are diluted by the effect of blood flow and cannot reach high enough concentrations to form insoluble fibrin. Platelets, which can stick to damaged vascular lumen even in the presence of shearing effects of blood flow, may play a crucial role in the onset of arterial thrombus formation. Thus, the mechanism of platelet thrombus formation should be assessed in the presence of blood flow. However, current dogma that fibrinogen binding to activated GP IIb/IIIa is the final common pathway for platelet thrombus formation was developed by using the function assay system of aggregometer, in which the effects of blood flow were not seriously considered. We are proposing in this review that plasma ligand protein of von Willebrand factor (vWF) and its interactions with platelet GP lb and GP IIb/IIa, which become apparent only in assays systems under influence of high shear rates of flow condition such as flowchambers or coneplate viscometers, are the key events leading to the onset of arterial thrombosis. A better understanding of the vWF-mediated mechanism of platelet thrombus formation is important for the development of better clinical tools to prevent ischemic heart disease as well as for a complete understanding of the mechanism of coronary thrombosis.     

Platelet thrombus formation in microvessels of young spontaneously hypertensive rats

We have previously shown an increase in platelet-to-endothelial cell adhesion in microvessels of spontaneously hypertensive rats (SHR) during the established stage of hypertension (12 weeks). The objective of the current study was to determine if the platelet-to-endothelial cell interaction would be altered in the early developmental phase of hypertension. Male weanling (3 weeks old) SHRs (n=6) and age matched normotensive Wistar-Kyoto (WKY) rats (n=6) were used to study platelet thrombus formation. Intravascular fluorescein isothiocyanate tagged to bovine serum albumin was activated with 450-490 nm light to induce thrombus formation in microvessels. Plasma concentrations of von Willebrand factor (vWF), fibrinogen and fibronectin (FN) were measured in rats during both early (3 week) and established stages of hypertension development. Thrombus initiation time in both arterioles (847+/-85 sec) and venules (222+/-40 sec) of young SHRs was significantly shorter (p<0.05) than in arterioles (1270+/-88 sec) and venules (630+/-72 sec) of age matched WKY rats respectively. After thrombus appearance, however, overall time for vessel occlusion in arterioles (2590+/-90 sec) and venules (935+/-131 sec) of SHRs was not different compared to that in arterioles (2650+/-191 sec) and venules (1240+/-93 sec) of age matched WKY rats. The plasma concentration of FN was increased (p<0.05) in both the young (0.9+/-0.1 mg/ml) and mature (1.1+/-0.2 mg/ml) hypertensive rats (n=5) compared to that in young (0.6+/-0.03 mg/ml) and mature (0.5+/-0.1 mg/ml) WKY rats (n=5), while fibrinogen content (3.6 +/-0.3 mg/ml) was elevated (p<0.05) only in mature SHRs (n=5) compared to that (2.7+/-0.02 mg/ml) in age matched WKY rats (n=5). The plasma concentration of vWF was similar to that of controls in either age group of hypertensive animals. These results suggest that changes in platelet-to-endothelial cell interactions occur in the early phase of genetic hypertension development in rats, and appears to result from alteration of plasma concentration of adhesion proteins.     

Anti-P-selectin antibody decreases inflammation and thrombus formation in venous thrombosis

PURPOSE: Venous thrombosis and inflammation are interrelated. P-selectin contributes to activation of leukocyte-mediated inflammation. Therefore, we hypothesized that the neutralization of P-selectin would decrease vein wall inflammation and thrombosis. METHODS: Twelve baboons underwent infrarenal inferior vena caval balloon occlusion to induce thrombosis. Two groups of four baboons received neutralizing intravenous anti-P-selectin antibody (PSab) GA6 or CY1748 before occlusion and at days 2 and 4. Four baboons received saline control injections. One baboon per group was killed at days 2, 6, and 13, and at 2 months. Analysis included phlebography, ultrasound, gadolinium (Gd)-enhanced magnetic resonance venography (reflecting vein wall inflammation), and histologic, morphometric, and protein evaluation of the vein wall. Thrombus presence or absence was assessed. RESULTS: By day 2 in PSab baboons, vein wall Gd enhancement was decreased in the mid-inferior vena cava and the right iliac vein (p < 0.05; GA6 vs control baboons), normalizing by 2 months. The mid-inferior vena cava revealed fewer neutrophils and total leukocytes in PSab baboons; however, for GA6 in the right iliac vein these decreases were not present despite the absence of Gd enhancement; they were decreased with CY1748. PSab baboons demonstrated significantly less thrombus than control baboons (p < 0.01, GA6 and CY1748 vs control baboons). CONCLUSIONS: Anti-P-selectin antibody decreases vein wall inflammation and thrombus formation. Inhibition of P-selectin may be useful in venous thrombosis prophylaxis.     

Specific synergy of multiple substrate-receptor interactions in platelet thrombus formation under flow

Eosinophils are known to express cytokines capable of promoting fibrosis. Interleukin-5 (IL-5) is important in regulating eosinophilopoiesis, eosinophil recruitment and activation. Lung IL-5 expression is elevated in pulmonary fibrosis, wherein the eosinophil is a primary source of fibrogenic cytokines. To determine the role of IL-5 in pulmonary fibrosis, the effects of anti-IL-5 antibody were investigated in a model of bleomycin-induced pulmonary fibrosis. Fibrosis was induced in mice by endotracheal bleomycin treatment. Animals were also treated with either anti-IL-5 antibody or control IgG. Lungs were then analyzed for fibrosis, eosinophil influx, chemotactic activity, and cytokine expression. The results show that a primary chemotactic activity at the height of eosinophil recruitment is IL-5. Furthermore, anti-IL-5 antibody caused significant reduction in lung eosinophilia, cytokine expression, and fibrosis. These findings taken together suggest an important role for IL-5 in pulmonary fibrosis via its ability to regulate eosinophilic inflammation, and thus eosinophil-dependent fibrogenic cytokine production.     

Activated protein C inhibits thrombus formation in a system with flowing blood

We studied the effect of increasing concentrations of protein C (PC) and activated protein C (APC) on haemostasis in an in vitro thrombosis model. Blood from healthy donors was anticoagulated with citrate-phosphate-dextrose (final citrate concentration 19 mM) or a low molecular weight heparin (LMWH, 20 IU/ml). Enzymatically denuded rabbit aorta segments were exposed to flowing blood for 10 min in an annular perfusion chamber. PC and APC were added to the perfusate immediately prior to exposure. In citrated blood at a shear rate of 800/s, PC and APC induced a statistically significant decrease in platelet deposit at 16 micrograms/ml and 32 micrograms/ml. In perfusions performed with blood anticoagulated with LMWH, there was no effect on platelet deposition at 16 and 32 micrograms/ml either at shear rates of 300/s or 800/s. Addition of PC showed no effect on fibrin deposition at a shear rate of 300/s; in contrast, a nonstatistically significant 40% reduction was seen at a shear rate of 800/s, compared to controls. Addition of APC caused a 100% reduction in fibrin formation at 16 and 32 micrograms/ml at both shear rates studied. PC and APC inhibited platelet deposition on the exposed subendothelial surface, in a dose-dependent manner. Effects of PC and APC on platelet function might be mediated through inhibition of thrombin generation at the platelet microenvironment.     

Effect of low dose aspirin on thrombus formation at arterial and venous microanastomoses and on the tissue microcirculation

In free flap/replantation surgery, failure is usually associated with thrombotic occlusion of a microvascular anastomosis (risk zone I) or, on occasion, flow impairment in the microcirculation of the transferred or replanted tissue (risk zone II). The objective of this study is to describe the effect of low dose aspirin on blood flow at both risk zones in microvascular surgery. Risk zone I: In rat femoral arteries and veins, thrombus formation was measured at the anastomoses using transillumination and videomicroscopy. Forty male Wistar rats were assigned in equal numbers to four groups: either arterial or venous injury with either aspirin (5 mg/kg systemically) or saline treatment. We found that aspirin significantly reduces thrombus formation at the venous anastomosis (p = 0.001). Risk zone II: In the isolated rat cremaster muscle downstream from an arterial anastomosis, we measured capillary perfusion, arteriolar diameters, and the appearance of platelet emboli for 6 hours in the muscle microcirculation. Sixteen male Wistar rats in two equal groups received either aspirin (5 mg/kg systemically) or saline. We found that in aspirin-treated animals, capillary perfusion is significantly (p = 0.002) improved, whereas arteriolar diameters and emboli only slightly increased. In conclusion, low dose aspirin inhibits anastomotic venous thrombosis and improves microcirculatory perfusion in our rat model. These studies provide quantitative data confirming and clarifying the beneficial effects of low dose aspirin in microvascular surgery.     

Measurement of plaque volume using three-dimensional intravascular ultrasound: in vitro study]

Sunlight causes acute toxic effects such as sunburn, local and systemic immune suppression, and long-term adverse effects including photoaging and skin cancer. The degree of damage depends on the overall exposure-dose and individual susceptibility. Various strategies should be employed to minimize sun-exposure damage, including proper use of sunscreens and exposure avoidance. Public education might best be focused on protecting children and promoting awareness of photoaging changes in adults.     

Intracoronary artery thrombus formation in unstable angina: a clinical, biochemical and angiographic correlation

OBJECTIVES: We examined the relation between the level of urinary fibrinopeptide A and the presence of angiographic intracoronary thrombus in patients with unstable angina to determine whether this marker predicts active thrombus formation. BACKGROUND: Although it is known that thrombus plays a role in acute ischemic syndromes, a noninvasive method to predict its presence in individual patients with unstable angina has not been determined. Fibrinopeptide A is a polypeptide cleaved from fibrinogen by thrombin and thus is a sensitive marker of thrombin activity and fibrin generation. METHODS: Angiographic thrombus, graded 0 to 4, and the presence of ST segment depression or T wave inversions, or both, on the electrocardiogram (ECG) were related to fibrinopeptide A levels in 24 patients with rest angina of new onset, 18 with crescendo angina, 19 with stable angina and 9 with chest pain but without coronary artery disease. All patients had chest pain within the 24 h of sample acquisition. RESULTS: The angiographic incidence of thrombus was significantly higher in patients with new onset of rest angina (67%, p < 0.001) and crescendo angina (50%, p < 0.001) as were fibrinopeptide A levels (p = 0.002). Fibrinopeptide A levels correlated significantly (p < 0.001) with the presence of a filling defect (grade 4 intracoronary thrombus) or contrast staining (grade 3). All patients with fibrinopeptide A > or = 8 ng/mg creatinine showed grade 3 to 4 thrombus and 15 of 16 patients with levels > or = 6.0 ng/mg creatinine exhibited angiographic evidence of thrombus (13 with grades 3 to 4). Patients with reversible ST changes on the ECG had significantly higher levels of fibrinopeptide A (p < 0.001), and ST changes correlated significantly with the presence of angiographic thrombus (p < 0.001). Nonetheless, a significant minority of patients with unstable angina had neither angiographic nor biochemical evidence of thrombus. CONCLUSIONS: Elevated fibrinopeptide A levels in unstable angina reflected active intracoronary thrombus formation and were present in patients with angina of new onset as well as crescendo angina. Reversible ST changes are accompanied by thrombin activity and angiographic thrombus formation. However, a sizable percentage of patients with unstable angina had no evidence of thrombus and these patients may have had transient platelet aggregation without fibrin thrombus formation.     

Effect of urokinase on disseminated intravascular coagulation

Our study evaluated the possible therapeutic effect of urokinase in treating the microthrombiotic effects of disseminated intravascular coagulation by assisting the activation of endogenous plasminogen. Twenty-six pigs were anesthetized, intubated, mechanically ventilated, and surgically catheterized. Septic shock was induced in all 26 pigs by an intravenous infusion of heat-killed Escherichia coli. The pigs were divided into two sets of experiments: in experiment 2 (n = 14), one-half received an intravenous dose of urokinase 1 h after heat-killed E. coli infusion and in experiment 3 (n = 12) one-half received an intravenous bolus dose and a continuous drip of urokinase 2 h after heat-killed E. coli infusion. The untreated pigs served as controls. Hemodynamic parameters, blood chemistries, and blood gases were analyzed. Urokinase given 1 h after bacterial toxin infusion significantly restored blood flow, resulting in an increase in cardiovascular and pulmonary function and improved survival rate (43% control vs. 100% treated, 24-h experimental period). Treatment given after 2 h showed some significant effect on pulmonary function; however, within 10 h of E. coli infusion, mortality rates in control and treated groups were 100 and 83%, respectively. Early administration of urokinase after onset of disseminated intravascular coagulation restored blood flow and helped resolve organ damage.     

Effects of gallstone solvents on commonly used catheters

PURPOSE: To determine what interaction and effect different cholesterol gallstone solvents have on catheters used for gallstone chemolysis. MATERIALS AND METHODS: Five types of catheters used for biliary procedures were chosen: polyethylene, Percuflex, silicon, Silitek, and polyurethane. The solvents chosen were methyl tert-butyl ether, ethyl propionate, isopropyl acetate, and N-propyl acetate. After incubation of the catheters in the solvents for 72 hours, they were air dried. Weight and area changes were determined for each catheter. Additionally, carbon-13 nuclear magnetic resonance (NMR) spectroscopy was performed for analysis of composition changes. RESULTS: Three catheters--silicone, Silitek, and polyurethane--showed changes in their physical characteristics that would make them less desirable for stone chemolysis. The silicone catheter showed changes in elastic texture as well as marked weight reduction. The Silitek and polyurethane catheters had similar, but less dramatic changes. C-13 NMR analysis of collected solvents showed that commonly used plasticizers were leached out of some catheters. CONCLUSION: These results suggest that all catheters are not suitable for use with all solvents. The choice of catheter should be made based on the solvent in use. The polyethylene catheter performed best under the conditions and endpoints used in this study.     

Effect of coronary thrombus age on fibrinogen uptake

A study was carried out to define the time limits during which an experimental coronary thrombus remains capable of incorporating fibrinogen. 131I-fibrinogen was given to intact anesthetized dogs at different time intervals, up to 67 hours, following the formation of a coronary thrombus by catheter-electrode. Radioactivity of the recovered thrombi as a whole and segmentally divided, was determined following variable time intervals of exposure to circulating fibrinogen and was expressed as thrombus/blood ratio. The results indicate that coronary thrombi formed in a normal coronary vessel remain capable of incorporating fibrinogen for at least eighteen hours, with no significant differences in the segmental distribution of radioactivity. These findings do not support the view that the recovery of isotopic fibrinogen, which was given after the onset of coronary symptoms, in thrombi from patients with myocardial infarction establishes that the thrombus was initiated after the ischemic process.