Medline ® Abstracts for References 3-9

In 1994, the American Society of Anesthesiologists established the Task Force on Blood Component Therapy to develop evidence-based indications for transfusing red blood cells, platelets, fresh-frozen plasma, and cryoprecipitate in perioperative and peripartum settings. The guidelines were developed according to an explicit methodology. The principal conclusions of the task force are that red blood cell transfusions should not be dictated by a single hemoglobin "trigger" but instead should be based on the patient's risks of developing complications of inadequate oxygenation. Red blood cell transfusion is rarely indicated when the hemoglobin concentration is greater than 10 g/dL and is almost always indicated when it is less than 6 g/dL. The indications for autologous transfusion may be more liberal than for allogeneic (homologous) transfusion. The risks of bleeding in surgical and obstetric patients are determined by the extent and type of surgery, the ability to control bleeding, the actual and anticipated rate of bleeding and the consequences of uncontrolled bleeding. Prophylactic platelet transfusion is ineffective when thrombocytopenia is due to increased platelet destruction. Surgical and obstetric patients with microvascular bleeding usually require platelet transfusion if the platelet count is less than 50 times 10(9)/l and rarely therapy if it is greater than 100 times 10(9)/l. Fresh-frozen plasma is indicated for urgent reversal of warfarin therapy, correction of known coagulation factor deficiencies forwhich specific concentrates are unavailable, and correction of microvascular bleeding when prothrombin and partial thromboplastin times are>1.5 times normal. It is contraindicated for augmentation of plasma volume or albumin concentration. Cryoprecipitate should be considered for patients with von Willebrand's disease unresponsive to desmopressin, bleeding patients with von Willebrand's disease, and bleeding patients with fibrinogen levels below 80-100 mg/dL. The task force recommends careful adherence to proper indications for blood component therapy to reduce the risks of transfusion. (Key words:Practice guide-lines: anemia: blood component therapy; coagulopathy; cryoprecipitate; fresh-frozen plasma; red blood cells; transfusion.)

OBJECTIVE: To develop a clinical practice guideline for red blood cell transfusion in adult trauma and critical care.

DESIGN: Meetings, teleconferences and electronic-based communication to achieve grading of the published evidence, discussion and consensus among the entire committee members.

METHODS: This practice management guideline was developed by a joint taskforce of EAST (Eastern Association for Surgery of Trauma) and the American College of Critical Care Medicine (ACCM) of the Society of Critical Care Medicine (SCCM). We performed a comprehensive literature review of the topic and graded the evidence using scientific assessment methods employed by the Canadian and U.S. Preventive Task Force (Grading of Evidence, Class I, II, III; Grading of Recommendations, Level I, II, III). A list of guideline recommendations was compiled by the members of the guidelines committees for thetwo societies. Following an extensive review process by external reviewers, the final guideline manuscript was reviewed and approved by the EAST Board of Directors, the Board of Regents of the ACCM and the Council of SCCM.

RESULTS: Key recommendations are listed by category, including (A) Indications for RBC transfusion in the general critically ill patient; (B) RBC transfusion in sepsis; (C) RBC transfusion in patients at risk for or with acute lung injury and acute respiratory distress syndrome; (D) RBC transfusion in patients with neurologic injury and diseases; (E) RBC transfusion risks; (F) Alternatives to RBC transfusion; and (G) Strategies to reduce RBC transfusion.

CONCLUSIONS: Evidence-based recommendations regarding the use of RBC transfusion in adult trauma and critical care will provide important information to critical care practitioners.

BACKGROUND: Practice guidelines reflect published literature. Because of the ever changing literature base, it is necessary to update and revise guideline recommendations from time to time. The Society of Thoracic Surgeons recommends review and possible update of previously published guidelines at least every three years. This summary is an update of the blood conservation guideline published in 2007.

METHODS: The search methods used in the current version differ compared to the previously published guideline. Literature searches were conducted using standardized MeSH terms from the National Library of Medicine PUBMED database list of search terms. The following terms comprised the standard baseline search terms for all topics and were connected with the logical 'OR' connector--Extracorporeal circulation (MeSH number E04.292), cardiovascular surgical procedures (MeSH number E04.100), and vascular diseases (MeSH number C14.907).Use of these broad search terms allowed specific topics to be added to the search with the logical 'AND' connector.

RESULTS: In this 2011 guideline update, areas of major revision include: 1) management of dual anti-platelet therapy before operation, 2) use of drugs that augment red blood cell volume or limit blood loss, 3) use of blood derivatives including fresh frozen plasma, Factor XIII, leukoreduced red blood cells, platelet plasmapheresis, recombinant Factor VII, antithrombin III, and Factor IX concentrates, 4) changes in management of blood salvage, 5) use of minimally invasive procedures to limit perioperative bleeding and blood transfusion, 6) recommendations for blood conservation related to extracorporeal membrane oxygenation and cardiopulmonary perfusion, 7) use of topical hemostatic agents, and 8) new insights into the value of team interventions in blood management.

CONCLUSIONS: Much has changed since the previously published 2007 STS blood management guidelines and this document contains new and revised recommendations.

Importance: More than 100 million units of blood are collected worldwide each year, yet the indication for red blood cell (RBC) transfusion and the optimal length of RBC storage prior to transfusion are uncertain.

Objective: To provide recommendations for the target hemoglobin level for RBC transfusion among hospitalized adult patients who are hemodynamically stable and the length of time RBCs should be stored prior to transfusion.

Evidence Review: Reference librarians conducted a literature search for randomized clinical trials (RCTs) evaluating hemoglobin thresholds for RBC transfusion (1950-May 2016) and RBC storage duration (1948-May 2016) without language restrictions. The results were summarized using the Grading of Recommendations Assessment, Development and Evaluation method. For RBC transfusion thresholds, 31 RCTs included 12 587 participants and compared restrictive thresholds (transfusion not indicated until the hemoglobin level is 7-8 g/dL) with liberal thresholds (transfusion not indicated until the hemoglobin level is 9-10 g/dL). The summary estimates across trials demonstrated that restrictive RBC transfusion thresholds were not associated with higher rates of adverse clinical outcomes, including 30-day mortality, myocardial infarction, cerebrovascular accident, rebleeding, pneumonia, or thromboembolism. For RBC storage duration, 13 RCTs included 5515 participants randomly allocated to receive fresher blood or standard-issue blood. These RCTs demonstrated that fresher blood did not improve clinical outcomes.

Findings: It is good practice to consider the hemoglobin level, the overall clinical context, patient preferences, and alternative therapies when making transfusion decisions regarding an individual patient. Recommendation 1: a restrictive RBC transfusion threshold in which the transfusion is not indicated until the hemoglobin level is 7 g/dL is recommended for hospitalized adult patients who are hemodynamically stable, including critically ill patients, rather than when the hemoglobin level is 10 g/dL (strong recommendation, moderate quality evidence). A restrictive RBC transfusion threshold of 8 g/dL is recommended for patients undergoing orthopedic surgery, cardiac surgery, and those with preexisting cardiovascular disease (strong recommendation, moderate quality evidence). The restrictive transfusion threshold of 7 g/dL is likely comparable with 8 g/dL, but RCT evidence is not available for all patient categories. These recommendations do not apply to patients with acute coronary syndrome, severe thrombocytopenia (patients treated for hematological or oncological reasons who are at risk of bleeding), and chronic transfusion-dependent anemia (not recommended due to insufficient evidence). Recommendation 2: patients, including neonates, should receive RBC units selected at any point within their licensed dating period (standard issue) rather than limiting patients to transfusion of only fresh (storage length:<10 days) RBC units (strong recommendation, moderate quality evidence).

Conclusions and Relevance: Research in RBC transfusion medicine has significantly advanced the science in recent years and provides high-quality evidence to inform guidelines. A restrictive transfusion threshold is safe in most clinical settings and the current blood banking practices of using standard-issue blood should be continued.