Best practice & research. Clinical anaesthesiology
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Best Pract Res Clin Anaesthesiol · Mar 2013
ReviewAnaemia: can we define haemoglobin thresholds for impaired oxygen homeostasis and suggest new strategies for treatment?
Observational clinical studies in perioperative medicine have defined a progressive increase in mortality that is proportional to both chronic preoperative anaemia and acute interpretative reductions in haemoglobin concentration (Hb). However, this knowledge has not yet helped to define the critical Hb threshold for organ injury and mortality in specific patient populations or in individual patients. Nor has this knowledge enabled us to develop effective treatment strategies for anaemia, as evident from the lack of a demonstrable improvement in survival in patients randomised to higher Hb levels by various treatment strategies including allogeneic red blood cell transfusion, erythropoiesis-stimulating agents (ESAs) and haemoglobin-based oxygen carriers (HBOCs). ⋯ The mechanisms include: (1) effective sensing of anaemia-induced tissue hypoxia; (2) adaptive cardiovascular responses to maintain adequate tissue oxygen delivery; (3) heterogeneity of organ-specific oxygen delivery to preferentially sustain vital organs which are essential for acute survival (heart and brain); (4) evidence of increased vital organ injury with interruption of cardiovascular responses to anaemia and (5) evidence of activation of adaptive cellular responses to maintain oxygen homeostasis and support survival during acute anaemia. Understanding these mechanisms may allow us to define treatment thresholds and novel treatment strategies for acute anaemia based on biological markers of tissue hypoxia. The overall goal of these approaches is to improve patient outcomes, including event-free perioperative survival.
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Best Pract Res Clin Anaesthesiol · Mar 2013
ReviewThe transfusion dilemma--weighing the known and newly proposed risks of blood transfusions against the uncertain benefits.
Due to its significant role in saving lives, blood transfusion became one of the most commonly used therapies in medicine. In the USA red blood cell transfusions, for instance, are given to an estimated 3-4 million patients per year. ⋯ Although methods of blood collection, preparation and storage have improved significantly, potential complications and controversial efficacy, especially of red blood cell transfusions, are still a major concern. One long-standing primary concern has been bacterial and viral contamination but recently other risks have been identified, mostly related to recipient immunomodulation and storage lesion-related changes.
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Best Pract Res Clin Anaesthesiol · Mar 2013
ReviewDrivers for change: Western Australia Patient Blood Management Program (WA PBMP), World Health Assembly (WHA) and Advisory Committee on Blood Safety and Availability (ACBSA).
Patient blood management is now high on national and international health-system agendas. Serious supply challenges as a result of changing population dynamics, escalating cost of blood, ongoing safety challenges and questions about transfusion efficacy and outcomes are necessitating change in transfusion practice. Numerous initiatives are underway to bring about change, including the institution of comprehensive patient blood management programmes. ⋯ Nationally and internationally, other initiatives are underway to bring about change and implement patient blood management. The World Health Assembly in May 2010 adopted resolution WHA63.12 endorsing patient blood management and its three-pillar application. The United States Advisory Committee on Blood Safety and Availability met in 2011 to consider the implications of this resolution and its implementation.
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One of the main factors that contributes to the need for transfusion in the surgical patient is excessive blood loss. Pillar 2 of patient blood management (PBM) includes all the strategies to reduce bleeding and preserve the patient's own blood, designed with an aim to reducing or avoiding transfusion. Some of these strategies, such as identifying and planning the management of patients at high risk of bleeding, can be implemented as early as at the preoperative assessment visit. ⋯ However, there are also additional anaesthetic techniques that can help reduce blood loss and transfusion requirements, such as the use of pharmacological or haemostatic agents. After surgery, PBM continues in the postoperative recovery unit or on the ward with the monitoring and management of postoperative bleeding. The blood lost via drains can be filtered, washed and reinfused, if needed.
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Perioperative anaemia is a common clinical entity. It is usually due to combination of various mechanisms, including: pre-existing anaemia prior to surgery; anaemia due to impaired erythropoiesis, including alterations of metabolism of iron and erythropoietin (EPO); anaemia due to increased destruction of red blood cells (RBCs); and anaemia due to iatrogenic causes. ⋯ Iatrogenic causes, notably excessive phlebotomies, remain a major cause of perioperative anaemia. With increasing emphasis on restrictive blood transfusion strategies, understanding these mechanisms is important for the clinician.