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Biomedical subjects

C M Samama

Publications and source records attributed to C M Samama.

18 recordsLinked to original sources
PubMed1995

Function of von Willebrand factor after crossed bone marrow transplantation between normal and von Willebrand disease pigs: effect on arterial thrombosis in chimeras.

von Willebrand factor (vWF) is essential for the induction of occlusive thrombosis in stenosed and injured pig arteries and for normal hemostasis. To separate the relative contribution of plasma and platelet vWF to arterial thrombosis, we produced chimeric normal and von Willebrand disease pigs by crossed bone marrow transplantation; von Willebrand disease (vWD) pigs were engrafted with normal pig bone marrow and normal pigs were engrafted with vWD bone marrow. Thrombosis developed in the chimeric normal pigs that showed normal levels of plasma vWF and an absence of platelet vWF; but no thrombosis occurred in the chimeric vWD pigs that demonstrated normal platelet vWF and an absence of plasma vWF. The ear bleeding times of the chimeric pigs were partially corrected by endogenous plasma vWF but not by platelet vWF. Our animal model demonstrated that vWF in the plasma compartment is essential for the development of arterial thrombosis and that it also contributes to the maintenance of bleeding time and hemostasis.

Animals↗
PubMed1995

Inhibition of platelet aggregation by inhaled nitric oxide in patients with acute respiratory distress syndrome.

BACKGROUND: Nitric oxide inhibits platelet adhesion and aggregation in vitro. The aim of this prospective study was to assess the platelet antiaggregating activity of nitric oxide administered to patients with acute respiratory distress syndrome (ARDS) at increasing concentrations. METHODS: In six critically ill patients (mean age 37 +/- 16 yr) with ARDS (lung injury severity score > or = 2.2), the lungs were mechanically ventilated with inhaled nitric oxide (1, 3, 10, 30, and 100 ppm) randomly administered. Patients with cardiac dysrhythmias, septic shock, an underlying hemostasis disorder (constitutive or acquired), a platelet count less than 100 Giga/l, or a decreased platelet aggregation and those treated with antiplatelet or anticoagulant agents were excluded. Platelet aggregation was measured without nitric oxide and at each nitric oxide concentration in platelet-rich plasma issued from radial artery. Ivy bleeding time using a horizontal incision was simultaneously performed. RESULTS: After nitric oxide, a non-dose-dependent but statistically significant decrease in ex vivo platelet aggregation induced by three aggregating agents was observed: adenosine diphosphate = -56 +/- 18%, collagen = -37 +/- 18%, and ristocetin = -45 +/- 18% (P < 0.05). In each individual, Ivy bleeding time remained within normal values measured in healthy volunteers, and variations after nitric oxide did not correlate with changes in platelet aggregation. Simultaneously, arterial oxygenation improved significantly and pulmonary artery pressure decreased significantly. CONCLUSIONS: In patients with ARDS and without preexisting coagulation disorders, the beneficial effects of inhaled nitric oxide on arterial oxygenation and pulmonary circulation are associated with a significant inhibition of platelet aggregation. This antithrombotic effect is not associated with a significant prolongation of the bleeding time.

Acute Disease↗
PubMed1994

Dipyridamole-thallium scintigraphy and gated radionuclide angiography to assess cardiac risk before abdominal aortic surgery.

BACKGROUND: Because many patients with atherosclerotic disease of the abdominal aorta also have coronary artery disease, assessment of cardiac risk before abdominal aortic surgery has received much attention. Our prospective study was designed to identify predictors of cardiac risk in consecutive patients evaluated preoperatively with dipyridamole-thallium single-photon-emission computed tomography (SPECT) to assess myocardial perfusion and radionuclide angiography to measure left ventricular ejection fraction. METHODS: Clinical and scintigraphic data were collected prospectively during hospitalization in 457 consecutive patients undergoing elective abdominal aortic surgery. Adverse cardiac outcomes were predicted with multivariate analyses. RESULTS: Eighty-six patients (19 percent) had one or more of the following postoperative complications: prolonged myocardial ischemia (61 patients), myocardial infarction (22), congestive heart failure (20), and severe ventricular tachyarrhythmia (2). Twenty patients died postoperatively (4.4 percent), half of them from cardiac causes. Information about myocardial perfusion obtained from dipyridamole-thallium SPECT did not accurately predict adverse cardiac outcomes. The best correlates of cardiac complications were definite clinical evidence of coronary artery disease (odds ratio, 2.6; 95 percent confidence interval, 1.6 to 4.3) and age greater than 65 years (odds ratio, 2.3; 95 percent confidence interval, 1.4 to 3.6). Measurement of the ejection fraction was useful only in the prediction of left ventricular failure. Age greater than 65 years was the only predictor of death (odds ratio, 26.4; 95 percent confidence interval, 3.5 to 200.0). CONCLUSIONS: The presence of definite clinical evidence of coronary artery disease and older age were the most important preoperative predictors of an adverse cardiac outcome after abdominal aortic surgery. These results suggest that the routine use of dipyridamole-thallium SPECT and radionuclide angiography for screening before abdominal aortic surgery may not be justified.

Aged↗
PubMed1994

Aprotinin to decrease bleeding and intraoperative blood transfusion requirements during descending thoracic and thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass.

The purpose of this retrospective study was to assess the efficacy of aprotinin, an antifibrinolytic agent, in reducing bleeding and blood transfusion requirements in patients undergoing descending thoracic or thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass (CPB). Sixty-nine consecutive patients underwent thoracic or thoracoabdominal aneurysmectomy using CPB in a 2-year period. None of the 29 patients operated on in 1990 (group 1) received aprotinin, whereas all 40 patients operated on in 1991 (group 2) were placed on a high-dose regimen of aprotinin. There were no significant differences between the two groups. Administration of aprotinin was associated with a decrease in CPB time (p = 0.02), surgical duration (p = 0.05) and intraoperative blood loss (p = 0.008) as well as a reduction in intraoperative packed red cells (p = 0.01), Cell-Saver units (p = 0.05), fresh-frozen plasma units (p = 0.002), and platelet concentrate (p = 0.01) requirements. These data suggest that aprotinin is effective in reducing bleeding and blood transfusion requirements during descending thoracic or thoracoabdominal aortic aneurysmectomy using CPB.

Adult↗
PubMed1994

Intraoperative measurement of activated partial thromboplastin time and prothrombin time with a new compact monitor.

A prospective study was conducted to evaluate a new compact portable coagulation monitor (Ciba-Corning Biotrack 512 Monitor), which enables the clinician to perform instantaneous activated partial thromboplastin time (APTT) and prothrombin time (PT). 126 patients scheduled for heparinized and nonheparinized vascular surgery, and gynaecological surgery, were included. A drop of capillary or venous whole blood was applied in disposable cartridges to successively perform APTT and PT, and the results of the tests were compared with conventional laboratory methods, performed in two different laboratories (Lab. A and B). Comparisons between Lab. A. and Lab. B. enables determination of the bias, precision, and percent of outliers (patients whose values differed more than 20%) in conventional methods. The reference value was defined as the mean of Lab. A. and Lab. B. values. For PT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias, the precision and the proportion of outliers. For APTT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias and the precision. The percent of outliers, however, was significantly greater with the venous sample of the compact monitor than with the reference (48 versus 22%), and even if it did not reach the statistical significance (P = 0.07) it was also higher with the capillary sample performed with the Ciba Monitor than with the reference (33%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Aprotinin could promote arterial thrombosis in pigs: a prospective randomized, blind study.

Haemostatic properties of aprotinin could be associated with an increased risk of thrombosis. A randomized, blinded study was conducted to consider the potential thrombogenicity of aprotinin, using the Folts' model on femoral arteries in 12 pigs. The flow variations were measured by a pulsed Doppler in anaesthetised animals. Ear immersion bleeding time was performed. During the first part of the study, a stenosis was performed successively on both femoral arteries, each for a period of 30 min, without prior injury, to assess the integrity of the vessel, and to check that the arteries did not develop cyclic flow reductions (CFR), permanent cessation of flow (PCF) or partial thrombosis, when a stenosis is applied. Then the clamp was released and a bolus of placebo (saline), or aprotinin (4 millions KIU, followed by a continuous infusion of 1 million KIU.h-1), was administered. At the end of the bolus, the second part of the study began. Stenosis was applied to the arteries. If CRF, PCF, or partial thrombosis were observed without prior injury then the infused drug (aprotinin or saline) was considered a prothrombotic drug, and the opposite artery was studied. For each animal, right and left femoral artery segments were fixed and studied (morphologic study). Eighteen arteries were studied. In the aprotinin group, 6 arteries out of 8 developed an unexpected thrombosis, as compared with only 2 out of 10 arteries in the control group (p = 0.02). The morphologic study confirmed the occurrence of thrombosis in 4 out of 7 arteries in the aprotinin group, as compared with only 1 out of 9 in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Comparative arterial antithrombotic activity of clopidogrel and acetyl salicylic acid in the pig.

We investigated the comparative antithrombotic properties of clopidogrel, an analogue of ticlopidine, and aspirin, using the Folts' model on femoral arteries in 22 pigs. On each animal, clopidogrel or aspirin were used to treat the thrombotic process on the left femoral artery and to prevent this process on the right femoral artery. Sequentially: an injury and stenosis were carried out on the left femoral artery; the thrombotic process was monitored with a Doppler during a 30-min observation period for cyclic flow reductions or permanent cessation of flow; after the first cyclic flow reduction occurred, clopidogrel (5 mg kg-1) or aspirin (2.5, 5, 100 mg kg-1) were injected intravenously; if cyclic flow reductions were abolished, epinephrine (0.4 micrograms kg-1 min-1) was injected to try to restore cyclic flow reductions and/or permanent cessation of flow; then injury and stenosis were applied on the right femoral artery. Before and after injection of clopidogrel or aspirin, ear immersion bleeding times and ex-vivo platelet aggregation were performed. Clopidogrel (n = 7) abolished cyclic flow reductions were efficiently prevented, even for two injuries. Basal bleeding time (5 min 28) was lengthened (> 15 min, 30 min after clopidogrel and remained prolonged even after 24 h). ADP-induced platelet aggregation was inhibited (more than 78%). Comparatively, aspirin had a moderate and no dose-dependent effect. Aspirin 2.5 mg kg-1 (n = 6) abolished cyclic flow reductions in 2 animals, CFR reoccurred spontaneously in one animal and epinephrine restored it in a second animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Peri- and postoperative use of low molecular weight heparin in peripheral vascular surgery].

A pilot study has been conducted in ten consecutive patients undergoing femoro-popliteal reconstruction or distal vascular surgery under epidural anaesthesia. Immediately before arterial cross-clamping, enoxaparin (E) (75 anti-Xa IU.kg-1) was injected intravenously (i.v.). During surgery, washing of the saphenous or polytetrafluoroethylene (PTFE) graft has been performed using enoxaparin. Enoxaparin (75 anti-Xa IU.kg-1) was administered subcutaneously (S.C.) 8 hours after the i.v. injection, and then every 12 hours during 10 days. The patency of the vascular reconstruction and the side-effects of E administration were evaluated clinically before and during surgery, then by a daily clinical examination. Echo-Doppler and/or arteriography were also performed preoperatively and on the 10th postoperative day. Haematocrit, platelet count, activated partial thromboplastin time, prothrombin time, thrombin time, fibrinogen and anti-Xa activity were assessed. None of the patients developed venous or arterial thrombosis and all the by-pass grafts remained patient. Only one minor surgical bleeding occurred on the first post operative day, despite anti-Xa levels in the expected range. One patient developed minor haematomas at the injection site. No bleeding was observed. Further randomized studies comparing LMWH and UH are required in order to substantiate these preliminary clinical and biological findings.

Aged↗
PubMed1990

[Mechanisms and prediction of hemorrhagic complications during surgery of thoraco-abdominal aortic aneurysms].

This study, including 33 consecutive patients was designed to assess the haemostatic alterations occurring during repair of thoracoabdominal aneurysms. The surgical procedure consisted in Dacron graft replacement of the diseased aorta, using neither cardiopulmonary bypass, nor any shunting technique, nor any heparin. Blood samples were drawn before anaesthesia, before and 30 min after unclamping, and on the first postoperative day. The measured parameters were: haematocrit, platelet count, bleeding, activated cephalin, thrombin and prothrombin times, and concentrations of fibrinogen, factors V, VII, X and II, anti-thrombin III, proteins C and S, fibrin degradation products, D-dimers, alpha 2-antiplasmin, plasminogen, tissue plasminogen activator, plasminogen activator inhibitor, and serum protein. Eight patients developed severe multiple haemorrhages; 3 of them died during the procedure because of uncontrollable bleeding. Although the measured parameters were similar in the "bleeding" and control (n = 25) groups before surgery, there was, before unclamping in the first group, an important increase in activated cephalin and thrombin times, with a fall in concentrations of factor II and V, protein C, fibrinogen, and alpha 2-antiplasmin, and in platelet numbers. After unclamping, these changes worsened further, with an increase in prothrombin time and in fibrinogen levels (0,8 g.l-1), without any increase in fibrin degradation products. Abnormal bleeding started about 30 min after this in all the patients of the "bleeding" group. These changes, involving the fibrinolytic system as well as a fall in concentration of all the coagulation factors, can probably be partly explained by the clamping and unclamping of mesenteric vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Aneurysm↗