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Biomedical subjects

Charles Marc Samama

Publications and source records attributed to Charles Marc Samama.

16 recordsLinked to original sources
PubMed2006

Massive transfusion and coagulopathy: pathophysiology and implications for clinical management.

PURPOSE: To review the pathophysiology of coagulopathy in massively transfused, adult and previously hemostatically competent patients in both elective surgical and trauma settings, and to recommend the most appropriate treatment strategies. METHODS: Medline was searched for articles on "massive transfusion," "transfusion," "trauma," "surgery," "coagulopathy" and "hemostatic defects." A group of experts reviewed the findings. PRINCIPAL FINDINGS: Coagulopathy will result from hemodilution, hypothermia, the use of fractionated blood products and disseminated intravascular coagulation. The clinical significance of the effects of hydroxyethyl starch solutions on hemostasis remains unclear. Maintaining a normal body temperature is a first-line, effective strategy to improve hemostasis during massive transfusion. Red cells play an important role in coagulation and hematocrits higher than 30% may be required to sustain hemostasis. In elective surgery patients, a decrease in fibrinogen concentration is observed initially while thrombocytopenia is a late occurrence. In trauma patients, tissue trauma, shock, tissue anoxia and hypothermia contribute to the development of disseminated intravascular coagulation and microvascular bleeding. The use of platelets and/or fresh frozen plasma should depend on clinical judgment as well as the results of coagulation testing and should be used mainly to treat a clinical coagulopathy. CONCLUSIONS: Coagulopathy associated with massive transfusion remains an important clinical problem. It is an intricate, multifactorial and multicellular event. Treatment strategies include the maintenance of adequate tissue perfusion, the correction of hypothermia and anemia, and the use of hemostatic blood products to correct microvascular bleeding.

Journal Article↗
PubMed2006

Prevention of postoperative venous thromboembolism. Risk assessment and methods of prophylaxis.

PURPOSE: To describe risk assessment models that have been developed to stratify patients into different risk levels of postoperative venous thromboembolism (VTE) and then to review the different methods of prophylaxis and to outline the evidence supporting their effectiveness and safety. SOURCE: Our review of the literature is focused on consensus documents, recent large randomized trials and meta-analyses. PRINCIPAL FINDINGS: The risk of VTE is determined by the type of surgery and underlying patient factors. Risk assessment models are useful in stratifying patients into different VTE risk levels. However, multiple risk factors are often present in the same patient and in practice the evaluation of their relative contribution to the overall risk remains difficult. A variety of prophylactic strategies including physical and pharmacological methods have been shown to be effective in different patient groups. Patients with a moderate or high risk of VTE should receive prophylaxis consisting of an antithrombotic agent, unless contraindicated, used alone or in combination with a mechanical method. Recommendations concerning which prophylaxis to use and how intensive it should be are based mainly on data from trials using surrogate endpoints, and do not translate easily into practical decisions aiming to reduce the incidence of symptomatic events. CONCLUSION: Although risk assessment models and recommendations provided by consensus documents are of practical assistance, a decision concerning any patient is best made by combining recommendations of the literature with clinical judgment, including individual patient risk factors for thrombosis and bleeding.

Animals↗
PubMed2006

Management of venous thromboembolism.

PURPOSE: To describe the drugs used to treat venous thromboembolism (VTE) and to review particular aspects of the management (elastic stockings, thrombolysis, thrombectomy, vena cava filter). SOURCE: Our review of the literature is focused on consensus documents and recent large randomized trials. PRINCIPAL FINDINGS: Subcutaneous low molecular weight heparins (LMWH) have been shown to be both safe and effective for the initial treatment of VTE and have largely replaced unfractionated heparin, unless there is a contraindication to LMWH such as severe renal insufficiency. Low molecular weight heparins or unfractionated heparin are usually administered for five to seven days. Treatment is gradually switched from heparin to oral vitamin K antagonists (VKA) which are usually started the same day as heparin. The duration of oral anticoagulation must be tailored to the individual patient according to the presence of reversible or continuing risk factors. In patients with active cancer, long-term treatment of VTE with LMWH has been shown to be more effective than oral anticoagulation and is recommended for the first three to six months of long-term anticoagulant therapy as an alternative approach to VKA. Elastic stockings are recommended because they have been shown to prevent postthrombotic syndrome. Thrombolysis is, usually, not justified for the treatment of deep venous thrombosis, but is used in cases of massive pulmonary embolism with arterial hypotension and/or shock. Vena cava filter placement is mainly indicated in patients with a proximal deep venous thrombosis and an absolute contraindication to anticoagulation. CONCLUSIONS: The initial management of patients with acute VTE has largely been simplified due to the use of LMWH. Early conversion to VKA is recommended for the great majority of patients. New agents, such as anti-Xa or oral thrombin inhibitors, are promising alternatives to heparins or VKA.

Animals↗
PubMed2006

Do antifibrinolytics reduce allogeneic blood transfusion in orthopedic surgery?

Studies have shown that antifibrinolytic (aprotinin, tranexamic acid, epsilon-aminocaproic acid) reduce blood loss in orthopedic surgery. However, most lacked sufficient power to evaluate the efficacy and safety on clinical outcomes. This meta-analysis aims to evaluate whether intravenous antifibrinolytics, when compared with placebo, reduce perioperative allogeneic erythrocyte transfusion requirement in adults undergoing orthopedic surgery and whether it might increase the risk of venous thromboembolism. From MEDLINE, EMBASE, and the Cochrane Controlled Trials Register, the authors identified 43 randomized controlled trials in total hip and knee arthroplasty, spine fusion, musculoskeletal sepsis, or tumor surgery performed to July 2005 (for aprotinin, 23 trials with 1,268 participants; tranexamic acid, 20 with 1,084; epsilon-aminocaproic acid, 4 with 171). Aprotinin and tranexamic acid reduced significantly the proportion of patients requiring allogeneic erythrocyte transfusion according to a transfusion protocol. The odds ratio was 0.43 (95% confidence interval, 0.28-0.64) for aprotinin and 0.17 (0.11-0.24) for tranexamic acid. Results suggest a dose-effect relation with tranexamic acid. Epsilon-aminocaproic acid was not efficacious. Unfortunately, data were too limited for any conclusions regarding safety. Although the results suggest that aprotinin and tranexamic acid significantly reduce allogeneic erythrocyte transfusion, further evaluation of safety is required before recommending the use of antifibrinolytics in orthopedic surgery.

Adult↗
PubMed2005

Methodological issues in trials assessing primary prophylaxis of venous thrombo-embolism.

AIMS: Many trials have been conducted to assess the efficacy of various strategies in the prevention of venous thrombo-embolism (VTE). Some of these trials have been subject to methodological criticisms. We aimed to assess the methodological issues raised by VTE trials. METHODS AND RESULTS: We searched MEDLINE and the Cochrane Central Register of Controlled Trials for articles assessing primary thromboprophylaxis published between 1994 and 2003 in 60 general medical and specialty journals. A total of 77 articles were analysed by two independent reviewers using a list of items. No primary endpoint was defined in 20% of trials. Although the primary endpoint was collected before day 15 in 75% of trials, there were >/=20% missing data in 56% of articles and >/=30% in 24.2% of articles. The rate of missing data was 23.7+/-9.7% in studies using venography-detected deep-vein thrombosis as an endpoint compared with 5.6+/-6.0% in studies using other endpoints. Among the 47 superiority trials, 27 (57.4%) reported an intention-to-treat (ITT) analysis, but only 10 (21.3%) reported an analysis that complied with this principle. These results were consistent when limiting the analysis to articles published in high-impact journal (impact factor more than 5). CONCLUSION: Recent randomized controlled trials assessing prophylactic regimens in VTE have important methodological limitations in terms of primary endpoints, missing data, and compliance with the ITT principle. These methodological shortcomings should be addressed when planning future trials.

Humans↗
PubMed2005

Perioperative platelet transfusion: recommendations of the Agence Française de Sécurité Sanitaire des Produits de Santé (AFSSaPS) 2003.

PURPOSE: To present the recommendations of the Agence Française de Sécurité Sanitaire des Produits de Santé (AFSSaPS; French Safety Agency for Health Products). METHODS: A panel of experts reviewed and graded the literature on platelet transfusions; recommendations were formulated. MAIN FINDINGS: Threshold platelet counts (PC) for transfusions in the perioperative context have not been clearly defined and should be determined by the existence of hemorrhagic risk factors. In the case of commonly practiced invasive procedures, the recommendation is to transfuse in order to achieve PC > 50,000xmicroL(-1). In the absence of platelet dysfunction, regardless of the type of surgery, the standard hemorrhagic risk threshold for surgery is 50,000xmicroL(-1). It has not been proven that the risk threshold is different according to the type of surgery. For neurosurgery and ophthalmologic surgery involving the posterior segment of the eye, a PC of 100,000xmicroL(-1) is required. For axial regional anesthesia, a PC of 50,000xmicroL(-1) is sufficient for spinal anesthesia; a PC of 80,000xmicroL(-1) has been proposed for epidurals. During massive transfusion, prophylactic platelet infusion cannot be recommended beyond a loss of two blood volumes in less than 24 hr (Professional Consensus). As for the therapeutic transfusion of plasma and/or platelets, as much as possible, platelet deficit should be documented with test results (PC and fibrinogen) before transfusing. In the event of bleeding, platelet transfusion may precede plasma infusion. However, although this recommendation has been the subject of several professional consensus agreements, it is not based on any randomized studies. CONCLUSION: Threshold PC for perioperative transfusions have not been clearly defined and most recommendations are the result of a professional consensus.

Blood Coagulation Disorders↗
PubMed2005

Two injections of erythropoietin correct moderate anemia in most patients awaiting orthopedic surgery.

BACKGROUND: The primary objective of this study was to assess the number of erythropoietin (EPO) injections required to reach a hematocrit (Ht) of 40% in moderately anemic patients. The secondary objective was to compare this strategy with autologous blood donation (ABD) in elective orthopedic surgery in terms of red blood cell (RBC) production. STUDY DESIGN AND METHODS: 93 patients with a baseline Ht between 30 and 39% were randomized into two groups the day of the preoperative assessment. In the EPO group, patients received 40,000 UI/week sc until they reached a maximal Ht of 40%. In the ABD group, a RBC pack was collected every week as long as the Ht was above 33%. RESULTS: Two EPO injections were necessary to reach a 40% Ht in 63% of the patients. It was possible to collect two RBC packs in 45% of the patients in the ABD group. Volume of RBC production was significantly higher in the EPO group: 268 +/- 142 mL vs 141 +/- 129 (P = 0.0001). In the EPO group, Ht was significantly higher on days one and three after surgery and at discharge. The energy score was better in the EPO group. In the ABD group, 12.6% patients vs 6.5% in the EPO group received allogeneic transfusion (ns). CONCLUSION: Only two EPO injections were sufficient to reach a Ht of 40% in the majority of patients. Therefore, to improve cost/effectiveness, the number of EPO injections should be related to baseline Ht instead of the four injections recommended in the product monograph.

Aged↗
PubMed2004

Aprotinin and major orthopedic surgery.

Aprotinin is a potent pharmacological agent that reduces bleeding and limits blood transfusion requirements in current surgical practice. Many studies have been conducted in orthopedic surgery. In several trials performed in total hip replacement (THR) and total knee replacement (TKN) patients, aprotinin only moderately decreased blood-loss-replacement requirements. Conversely, when aprotinin was used in patients at high risk for bleeding (cancer, sepsis, redone surgery), it developed a potent hemostatic activity and decreased blood transfusion significantly. No increase in deep vein thrombosis and pulmonary embolism was observed. The only major side effect could be the potential occurrence of an anaphylactoid reaction. Prophylactic administration of aprotinin should be considered in extensive spine surgery and in high-risk major orthopedic operations. The decision to use aprotinin should be guided by a risk/benefit analysis.

Aprotinin↗
PubMed2004

A direct antifibrinolytic agent in major orthopedic surgery.

Aprotinin is a potent pharmacological agent that reduces bleeding. In current surgical practices, the rate of blood transfusions has decreased with the use of aprotinin. Recently, studies using aprotinin have been conducted in orthopedic surgery. Several trials have been performed in patients undergoing total hip replacement and total knee replacement. Aprotinin moderately decreased blood loss in these patients. When aprotinin was used in patients with a high-risk of bleeding (ie, patients with cancer, sepsis, or undergoing reoperation), potent hemostatic activity occurred and the rate of blood transfusions significantly decreased. No increase in deep vein thrombosis and pulmonary embolism was observed. One adverse effect was the potential occurrence of an anaphylactoid reaction. Prophylactic administration of aprotinin should be considered in extensive spine surgery and in high-risk orthopedic operations. The decision to use aprotinin can be guided by a risk/benefit analysis.

Antifibrinolytic Agents↗
PubMed2002

Extended venous thromboembolism prophylaxis after total hip replacement: a comparison of low-molecular-weight heparin with oral anticoagulant.

BACKGROUND: Oral anticoagulants and low-molecular-weight heparin are both recommended for venous thromboembolism prophylaxis after total hip replacement. To date, these regimens have not been compared by means of clinical end points in the extended prophylaxis setting. METHODS: We randomly assigned 1279 patients 3 days after total hip replacement surgery to fixed-dose subcutaneous low-molecular-weight heparin (reviparin sodium, 4200 anti-Xa IU) or adjusted-dose oral anticoagulant (international normalized ratio, 2-3; acenocoumarol) for a 6-week period. The primary end point was the failure rate, defined as the combined clinical events of a confirmed symptomatic thromboembolic event, a major hemorrhage, or death. All patients were followed up throughout the study interval. The primary objective was to compare the observed cumulative failure rate in the low-molecular-weight heparin vs oral anticoagulant group. RESULTS: In the intent-to-treat population, objectively documented symptomatic thromboembolic events occurred in 15 (2.3%) of 643 patients vs 21 (3.3%) of 636 patients receiving low-molecular-weight heparin or oral anticoagulants, respectively (P =.30; 95% confidence interval for the difference, -0.8% to 2.8%). Major bleeding occurred in 9 (1.4%) of 643 patients vs 35 (5.5%) of 636 patients receiving low-molecular-weight heparin or oral anticoagulants, respectively (P =.001). The failure rate was 24 (3.7%) of 643 patients compared with 53 (8.3%) of 636 patients who received low-molecular-weight heparin or oral anticoagulants (P =.001). CONCLUSIONS: A significantly higher benefit-risk ratio was observed for patients undergoing elective hip replacement who received extended out-of-hospital prophylaxis with low-molecular-weight heparin vs acenocoumarol. Low-molecular-weight heparin prophylaxis was at least as effective as oral anticoagulants, but with a marked improvement in safety.

Acenocoumarol↗
PubMed2002

Aprotinin versus placebo in major orthopedic surgery: a randomized, double-blinded, dose-ranging study.

UNLABELLED: We conducted a prospective, multicenter, double-blinded, dose-ranging study to compare the risk/benefit ratio of large- and small-dose aprotinin with placebo after major orthopedic surgery. Fifty-eight patients were randomized into three groups: Large-Dose Aprotinin (4 M kallikrein inactivator unit [KIU] bolus before surgery followed by a continuous infusion of 1 M KIU/h until the end of surgery), Small-Dose Aprotinin (2 M KIU bolus plus 0.5 M KIU/h), and Placebo. Bleeding was measured and calculated. Bilateral ascending venography was systematically performed on the third postoperative day. Measured and calculated blood loss decreased in the Large-Dose Aprotinin group (calculated bleeding, whole blood, hematocrit 30%, median [range], 2,023 mL [633-4,113] as compared with placebo, 3,577 mL [1,670-21,758 mL]). The total number of homologous and autologous units was also significantly decreased in the Large-Dose Aprotinin group (2 U [0-5 U] as compared with placebo, 4 U [0-42 U]). No increase in deep vein thrombosis or pulmonary embolism was observed in the aprotinin groups. Large-dose aprotinin was safe and effective in dramatically reducing the measured and calculated bleeding and the amount of transfused red blood cell units after major orthopedic surgery. IMPLICATIONS: Large doses of aprotinin decrease blood loss and transfusion amount in major orthopedic surgery.

Adult↗
PubMedDate not supplied

Antiplatelet agents in the perioperative period: expert recommendations of the French Society of Anesthesiology and Intensive Care (SFAR) 2001--summary statement.

PURPOSE: Antiplatelet agents are administered to an increasing number of patients. Preoperative treatment with these agents represents a major problem for the anesthesiologist. The results of a French expert meeting on their perioperative management are reported. METHODS: Responses to questions formulated by the Organizing Committee were drafted by a group of experts and reviewed by a multidisciplinary. Reading Committee. Recommendations were classified (grade) according to the evidence level of the studies supporting them. PRINCIPAL FINDINGS: First, antiplatelet agents have a variable effect on hemostasis as far as bleeding risk is concerned. Aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) increase intra- and postoperative bleeding moderately, but not transfusion requirements. Very few data are available on clopidogrel and ticlopidin. Anti-glycoprotein (GP) IIb/IIIa agents may increase bleeding when surgery is required in proximity with their administration. Second, the common practice of withdrawing antiplatelet agents is now challenged because an increased incidence of myocardial infarction has been reported in patients in whom treatment was interrupted. Third, aspirin should not be withdrawn for most vascular procedures and in several additional settings. When a definite increase in intraoperative bleeding is feared, or when surgical hemostasis is difficult, aspirin, clopidogrel or ticlopidine can be replaced by short-acting NSAIDS, given for a ten-day period and interrupted the day before surgery. Platelet transfusion should only be given when overt bleeding is observed. Postoperatively, antiplatelet treatment should be resumed immediately after surgery (first six hours). CONCLUSION: Anesthesiologists should be aware of the indications, potential complications and means of substitution of these agents.

Anesthesia↗