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Results for “Platelet Function Tests”

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At least 1,243 records · Page 69Linked to original sources
PubMed1981

Enhanced in vivo platelet release reaction and malondialdehyde formation in patients with hyperlipidemia.

Plasma level of beta-thromboglobulin (beta TG), a useful marker of in vivo platelet "release reaction,"was determined by radioimmunoassay in 69 patients, with three types of primary hyperlipidemia (IIa, IIb, IV) and compared with the findings in age- and sex-matched healthy controls and 57 patients with established atherosclerosis and peripheral vascular disease. Malondialdehyde (MDA) formation, used for assessment of prostaglandin synthesis, was determined in 51 and plasma platelet factor 4 (PF4), measured by radioimmunoassay, in 48 of the patients with hyperlipidemia. Results were correlated to five serum lipids and lipoprotein levels in the patients with hyperlipidemia. beta TG was significantly increased in the patients with hyperlipidemia and peripheral vascular disease, compared to those in the controls (p < 0.001); it was significantly higher in the patients with hyperlipidemia than in those with peripheral vascular disease. PF4 and MDA formation were also increased in the patients with hyperlipidemia, and significantly higher levels of MDA were obtained in patients with type IIb and type IV hyperlipidemia than in those with type IIa hyperlipidemia (p < 0.02). beta TG and MDA correlated weakly with total serum cholesterol triglycerides and very low density lipoprotein-triglyceride. There was also a significant correlation between beta TG and PF4, and MDA production. These results indicate that in vivo platelet "release reaction" and MDA formation are increased in hyperlipidemic patients. The release reaction is more enhanced in those with hyperlipidemia than in the patients with peripheral vascular disease. They suggest that the abnormal platelet function is related to the elevated levels of serum lipids and lipoproteins in the hyperlipidemic patients and not only to the atherosclerotic changes associated with hyperlipidemia.

Aged↗
PubMed1989

Factors influencing hemostasis after umbilical vein puncture in vitro.

Bleeding from the site of cordocentesis can be detected by ultrasound examination, but significant hemorrhage into the amniotic fluid rarely occurs. To evaluate the relative contribution of amniotic fluid thromboplastins and the quantity of Wharton's jelly in facilitating coagulation at the puncture site, amniotic fluid samples and umbilical cord segments were obtained at cesarean section from 20 patients. After puncture of the umbilical vein, bleeding times were measured in amniotic fluid and 0.9% sodium chloride. The quantity of Wharton's jelly was assessed by measuring umbilical cord circumference. Mean bleeding times were significantly shorter in amniotic fluid compared with saline solution, but there was no consistent relationship between bleeding times and umbilical cord circumference. We conclude that properties of amniotic fluid facilitate coagulation at the site of umbilical vein puncture.

Amniotic Fluid↗
PubMed1993

Different anticoagulants and platelet reactivity in cardiac surgical patients.

A technique for assessing platelet reactivity to shear stress from nonanticoagulated blood samples was employed to compare the relative effects of an unfractionated heparin, a low-molecular-weight heparin, and hirudin. The in vitro platelet effect of unfractionated heparin (5 U/mL) was measured in 290, the effect of a low-molecular-weight heparin (1 anti-Xa unit/mL) in 74, and the effect of hirudin (8 micrograms/mL) in 50 cardiac surgical patients. The relative proportions of patients exhibiting an enhanced platelet reactivity, a mild to moderate inhibition, and a severe inhibition were, respectively: 8.6%, 58.6%, and 32.8% for unfractionated heparin; 22%, 66%, and 12% for the low-molecular-weight heparin; and 6%, 66%, and 28% for hirudin. At the concentrations examined, a significantly greater proportion (p < 0.01) of the patients exhibited enhanced platelet reactivity and a significantly smaller proportion (p < 0.01) showed severely inhibited platelet reactivity associated with the low-molecular-weight heparin versus the unfractionated heparin, whereas there was no significant difference between the patients treated with hirudin and unfractionated heparin. Although the relevance of this study is limited because the clinically appropriate concentration of the alternative anticoagulants and comparative doses are unknown, it can be inferred that low-molecular-weight heparin may reduce the blood loss associated with cardiopulmonary bypass.

Anticoagulants↗
PubMed1993

Platelet protection by low-dose aprotinin in cardiopulmonary bypass: electron microscopic study.

To evaluate the effect of low-dose aprotinin during cardiopulmonary bypass on platelet function and clinical hemostasis, 30 patients undergoing various cardiopulmonary bypass procedures employing bubble oxygenators were randomized to receive either low-dose aprotinin (2 x 10(6) KIU in the cardiopulmonary bypass priming solution, 15 patients [group A]) or placebo (15 patients [group B]). Blood samples were collected before and after cardiopulmonary bypass to assess platelet count and aggregation on extracellular matrix, which was studied by a scanning electron microscope. On a scale of 1 to 4 preoperative mean platelet aggregation grades were similar in both groups (3.8 +/- 0.5 and 3.5 +/- 0.5 for groups A and B, respectively). Postoperatively, platelet aggregation on extracellular matrix decreased slightly in group A (2.8 +/- 1.3; p < 0.01) and significantly in group B (1.3 +/- 0.5; p < 0.001). Eleven of the 15 patients in group A remained in aggregation grade 3 or 4 compared with none of the group B patients. Platelet count was similar in both groups preoperatively and postoperatively. Total 24-hour postoperative bleeding and blood requirement were lower in the aprotinin group (487 +/- 121 mL and 2.3 +/- 1.0 units) than in the placebo group (752 +/- 404 mL and 6.8 +/- 5.1 units; p < 0.01). These results show that the use of low-dose aprotinin during cardiopulmonary bypass provides improved postoperative hemostasis, which might be related to the protection of the platelet aggregating capacity.

Aged↗
PubMed1994

Relationship of platelet aggregation to bleeding after cardiopulmonary bypass.

Excessive bleeding after cardiopulmonary bypass operations is a persistent problem. This study assessed the influence of platelet function on blood loss for 134 patients undergoing cardiopulmonary bypass. Platelet function was measured by platelet aggregation in platelet-rich plasma and whole blood using collagen as the agonist. Adenosine triphosphate release was assessed concurrently. Measurements were made 1 day before operation and 1 hour after the cessation of cardiopulmonary bypass. Three important findings were made. First, statistically significant correlations were shown between preoperative and postoperative platelet aggregation and blood drainage for the first 3 hours postoperatively. Second, correlations were greatest when preoperative measurement was performed on whole blood and postoperative measurement was performed on platelet-rich plasma. Third, patients with reduced postoperative platelet aggregation in platelet-rich plasma had significantly greater transfusion requirements in the first 24 hours postoperatively. In defining the 16 patients who bled excessively among the 134 patients studied, the preoperative aggregation in whole blood had a sensitivity of 62%, specificity of 75%, positive predictive value of 26%, and negative predictive value of 94%. The postoperative aggregation in platelet-rich plasma had a sensitivity of 86%, specificity of 69%, positive predictive value of 28%, and negative predictive value of 97%. These results indicate that preoperative and postoperative measurement of platelet aggregation may provide a rationale for the prophylaxis or treatment of patients to reduce blood loss after cardiopulmonary bypass.

Adenosine Triphosphate↗
PubMed1986

Impaired cAMP metabolism associated with abnormal function of thrombopathic canine platelets.

The effects of forskolin and 1-Methyl-3-isobutyl-xanthine on thrombopathic platelet function and cyclic AMP accumulation were examined. The concentration of forskolin required to inhibit gamma-thrombin- induced platelet aggregation and secretion by 50% was significantly lower for thrombopathic than for normal platelets. This inhibition was accompanied by a marked elevation of cyclic AMP. 1-Methyl-3-isobutyl-xanthine, alone or in combination with forskolin, augmented both the cyclic AMP accumulation and the inhibition of platelet function. These results demonstrate that cyclic AMP metabolism is abnormal in thrombopathic platelets and imply that cyclic AMP-phosphodiesterase activity is impaired.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Phytosterolemia in children with parenteral nutrition-associated cholestatic liver disease.

BACKGROUND: Lipid emulsions used for parenteral nutrition (PN) contain phytosterols. Our hypothesis was that these phytosterols can accumulate and contribute to cholestatic liver disease and other complications of PN, e.g., thrombocytopenia (which occurs in hereditary phytosterolemia). METHODS: Using gas chromatography-mass spectrometry, plasma concentrations of sterols were measured in 29 children aged 2 months to 9 years receiving PN and in 29 age-matched controls. The children receiving PN fell into two subgroups: 5 with severe PN-associated cholestatic liver disease (bilirubin level, > 100 mumol/L; aspartate aminotransferase [AST] level, > 200 U/L) and 24 with a bilirubin level of < 100 mumol/L and/or AST level of < 200 U/L. RESULTS: The 5 children with severe PN-associated liver disease had plasma concentrations of phytosterols and sitostanol that were as high as those seen in patients with hereditary phytosterolemia (total phytosterols 1.3-1.8 mmol/L). All 5 had intermittent thrombocytopenia. A reduction in intake of lipid emulsion to < 50 mL.kg-1.wk-1 was associated with a decrease in plasma phytosterol concentrations and an improvement in liver function tests and platelet counts in two patients. Children with less severe PN-associated liver disease had lower plasma phytosterol concentrations than the 5 with severe disease. CONCLUSIONS: Children receiving PN who have high plasma phytosterol concentrations also have cholestatic liver disease and thrombocytopenia; phytosterolemia might contribute to the pathogenesis of complications of PN.

Aspartate Aminotransferases↗
PubMed1992

Cytomegalovirus hepatitis in late pregnancy.

A case of pregnancy complicated by cytomegalovirus hepatitis is represented. The mother had a fulminant disease, but she delivered spontaneously at 31 weeks of gestation. The baby was unaffected.

Adult↗
PubMed1982

Further observations on the effects of dietary fatty acid composition on platelet reactivity and blood coagulation in man and the influence of methodology on findings.

Eight human subjects were fed diets enriched in saturated fat (SF), or polyunsaturated fat (PUF) and after each dietary regimen the plasma heparinthrombin clotting time (HTCT) was determined. The HTCT of citrated plasma indicated reduced heparin-neutralizing activity (HNA) after PUF feeding compared with SF feeding. Platelet factor 4 (PF4) levels in the citrated plasma samples demonstrated an inverse correlation with the HTCT (r = 0.62). Experiments with purified PF4 indicated that the PF4 present in citrated plasma could only account for approximately 10% of the HNA. Plasma prepared in a manner which minimized in vitro release of platelet constituents contained significantly less PF4 after PUF feeding and indicated that most of the PF4 found in citrated plasma resulted from in vitro release. The factor Xa inhibitory activity of citrated plasma was not significantly altered by either of the dietary regimens.

Adult↗
PubMed1984

The long-term effect of dietary supplementation with fish lipid concentrate on serum lipids, bleeding time, platelets and angina.

The effect of a fish lipid concentrate rich in eicosapentaenoic acid was studied in 107 subjects for periods up to 2 years. Ninety-two had heart disease or hyper-lipidaemia and 15 had no history of heart disease. Serum triglyceride levels were rapidly reduced, cholesterol fell more slowly but high density lipoprotein (HDL) cholesterol was increased. Bleeding time increased significantly and the consumption of glyceryl trinitrate (GTN) tablets decreased together with a reduction in anginal attacks. The data are consistent with a reduction in hepatic triglyceride synthesis rather than an increased rate of triglyceride clearance. Total and HDL cholesterol changes are suggestive of an enhanced removal of cholesterol from the tissues. Increased bleeding time and changes in GTN consumption are consistent with decreased platelet aggregation.

Adult↗
PubMed1987

Fish oil in angina pectoris.

The effect of 12 weeks supplementation with fish oil on the number of anginal attacks and consumption of glyceryltrinitrate in 36 patients with stable angina pectoris was evaluated in a clinically controlled trial using a vegetable oil as placebo. Fish oil caused a decrease in frequency of angina, but was not significantly superior to placebo. However, due to the small sample size and a high spontaneous variation in number of anginal attacks, a risk of up to 50% of overlooking a 30% reduction in anginal attacks could be estimated. A significant inhibition of the epinephrine-induced platelet aggregation and a significant increase in intraplatelet cyclic AMP were induced by fish oil.

Angina Pectoris↗
PubMed1986

Improved graft patency associated with altered platelet function induced by marine fatty acids in dogs.

Female mongrel dogs fed a marine fish diet rich in long-chain polyenoic fatty acids had improved patency of small-diameter arterial prosthetic grafts as compared to controls. Also, in vivo platelet function as measured by bleeding times was significantly prolonged. Eicosapentaenoic acid, not found in the serum of control animals, was present in relatively high concentrations in both the serum and a platelet-rich fraction of the marine oil-fed group. Eicosapentaenoic acid, unlike arachidonic acid, does not induce platelet aggregation and this phenomonon may account for the altered platelet function demonstrated in our animals and hence the improved graft patency. These data lend further support to the role of platelets in determining the patency of vascular grafts.

Animals↗
PubMed1984

Platelet aggregation in poiseuille flow: I. A double infusion technique.

This paper describes the design of a double infusion microtube and its use to directly observe the aggregation of platelets undergoing Poiseuille flow immediately after the introduction of 1 microM ADP. Citrated human platelet-rich plasma flowed between two reservoirs through a 100-microns-diameter flow tube at the entrance of which ADP was simultaneously infused through the tip of a concentrically located micropipet . With the aid of microcinematography, the time course of platelet aggregation was followed by measuring the number distribution of single cells and aggregates across the median plane of the tube at various distances downstream of the micropipet . Preliminary studies covering a range of mean tube shear rates from 2 to 30 sec-1 showed that, for a given donor, the fraction of platelets in aggregates, both in control runs (infusion of Tyrodes ) and in experimental runs (infusion of ADP) was reproducible to within +/- 1%. Except at the lowest shear rate, the extent of aggregation increased with increasing distance down the tube.

Adenosine Diphosphate↗
PubMed1984

Platelet aggregation in poiseuille flow: II. Effect of shear rate.

Using a double infusion technique described in the previous paper, the effect of shear rate, G, on platelet aggregation was studied in citrated platelet-rich plasma in Poiseuille flow over a range of mean linear flow rates, u3 from 50 to 1500 microns-1 corresponding to G from 2 to 54 sec-1. At 1 micron ADP, aggregates were formed at all u3 and, except at the lowest flow rate, both the degree of aggregation (net fraction of cells in aggregates, A') and size of the aggregates increased with distance down the tube. The degree of aggregation was both time and shear rate-dependent. Over the first 10 sec, A' appeared to be independent of the mean transit time indicating that the collision capture efficiency decreased with increasing G. Thereafter, A' increased with increasing shear rate leading to the formation of an appreciable number of aggregates greater than 10 cells at G greater than 24 sec-1. Small aggregates initially formed near the tube wall and, as they grew in size, migrated toward the axis as their rotation was physically impeded by the wall. In addition, the values of A' in cPRP from five female donors were significantly greater than those from five male donors.

Adult↗