Electrocardiographic ST-segment changes during acute, severe isovolemic hemodilution in humans

Alternative blood transfusion triggers: a narrative review

BACKGROUND

Anemia, characterized by low hemoglobin levels, is a global public health concern. Anemia is an independent factor worsening outcomes in various patient groups. Blood transfusion has been the traditional treatment for anemia; its triggers, primarily based on hemoglobin levels; however, hemoglobin level is not always an ideal trigger for blood transfusion. Additionally, blood transfusion worsens clinical outcomes in certain patient groups. This narrative review explores alternative triggers for red blood cell transfusion and their physiological basis.

MAIN TEXT

The review delves into the physiology of oxygen transport and highlights the limitations of using hemoglobin levels alone as transfusion trigger. The main aim of blood transfusion is to optimize oxygen delivery, necessitating an individualized approach based on clinical signs of anemia and the balance between oxygen delivery and consumption, reflected by the oxygen extraction rate. The narrative review covers different alternative triggers. It presents insights into their diagnostic value and clinical applications, emphasizing the need for personalized transfusion strategies.

CONCLUSION

Anemia and blood transfusion are significant factors affecting patient outcomes. While restrictive transfusion strategies are widely recommended, they may not account for the nuances of specific patient populations. The search for alternative transfusion triggers is essential to tailor transfusion therapy effectively, especially in patients with comorbidities or unique clinical profiles. Investigating alternative triggers not only enhances patient care by identifying more precise indicators but also minimizes transfusion-related risks, optimizes blood product utilization, and ensures availability when needed. Personalized transfusion strategies based on alternative triggers hold the potential to improve outcomes in various clinical scenarios, addressing anemia's complex challenges in healthcare. Further research and evidence are needed to refine these alternative triggers and guide their implementation in clinical practice.

Perioperative Fluid Management

The medical complexity of the geriatric patients has been steadily rising. Still, as outcomes of surgical procedures in the elderly are improving, centers are pushing boundaries. There is also a growing appreciation of the importance of perioperative fluid management on postoperative outcomes, especially in the elderly. Optimal fluid management in this cohort is challenging due to the combination of age-related physiological changes in organ function, increased comorbid burden, and larger fluid shifts during more complex surgical procedures. The current state-of-the-art approach to fluid management in the perioperative period is outlined.

Patient Blood Management, Anemia, and Transfusion Optimization Across Surgical Specialties

Patient blood management (PBM) is a systematic, evidence-based approach to improve patient outcomes by managing and preserving a patient's own blood and minimizing allogenic transfusion need and risk. According to the PBM approach, the goals of perioperative anemia management include early diagnosis, targeted treatment, blood conservation, restrictive transfusion except in cases of acute and massive hemorrhage, and ongoing quality assurance and research efforts to advance overall blood health.

Perioperative Anemia and Transfusions and Late Mortality in Coronary Artery Bypass Patients

BACKGROUND

Perioperative anemia and transfusions are associated with adverse operative outcomes after coronary artery bypass graft surgery (CABG). Their individual association with long-term outcomes is unclear.

METHODS

Patients aged 65 years and older who had undergone CABG and were in The Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database (n = 504,596) from 2011 to 2018 were linked to Centers for Medicare and Medicaid Service data to assess long-term survival. The association of intraoperative anemia defined by intraoperative nadir hematocrit (nHct) and red blood cell (RBC) transfusions, and their interactions, on long-term mortality were assessed with Kaplan-Meier estimates and multivariable Cox regression. Restricted cubic splines were used to explore the association between nHct as a continuous variable and long-term mortality.

RESULTS

258,398 on-pump CABG STS Adult Cardiac Surgery Database patients surviving the perioperative period were linked to Centers for Medicare and Medicaid Service claims files. Per World Health Organization criteria, 41% had preoperative anemia. Mean intraoperative nHct was 24%; RBC transfusion rate was 43.7%. Univariable analysis associated both RBC transfusion and lower nHct with worse survival. Lower nHct was only marginally associated with risk-adjusted mortality: adjusted hazard ratio (AHR) 1.04 (95% CI, 1.01-1.06) and 1.07 (95% CI, 1.00-1.14) at nHct 20% and at nHct 14%, respectively. RBC transfusion was associated with significantly higher adjusted mortality irrespective of timing of transfusion: AHR intraoperative 1.21 (95% CI, 1.18-1.27); AHR postoperative 1.26 (95% CI, 1.22-1.30); AHR both 1.46 (95% CI, 1.40-1.52) and across all levels of nHct. RBC transfusion was not associated with improved survival at any level of nHct.

CONCLUSIONS

Among Medicare CABG patients, RBC transfusions were associated with increased risk-adjusted late mortality across all levels of nHct whereas intraoperative anemia was only marginally so. Tolerance of lower intraoperative nHct than currently accepted may be preferable to transfusions.

TRansfusion strategies in Acute brain INjured patients (TRAIN): a prospective multicenter randomized interventional trial protocol

BACKGROUND

Although blood transfusions can be lifesaving in severe hemorrhage, they can also have potential complications. As anemia has also been associated with poor outcomes in critically ill patients, determining an optimal transfusion trigger is a real challenge for clinicians. This is even more important in patients with acute brain injury who were not specifically evaluated in previous large randomized clinical trials. Neurological patients may be particularly sensitive to anemic brain hypoxia because of the exhausted cerebrovascular reserve, which adjusts cerebral blood flow to tissue oxygen demand.

METHODS

We described herein the methodology of a prospective, multicenter, randomized, pragmatic trial comparing two different strategies for red blood cell transfusion in patients with acute brain injury: a "liberal" strategy in which the aim is to maintain hemoglobin (Hb) concentrations greater than 9 g/dL and a "restrictive" approach in which the aim is to maintain Hb concentrations greater than 7 g/dL. The target population is patients suffering from traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), or intracerebral hemorrhage (ICH). The primary outcome is the unfavorable neurological outcome, evaluated using the extended Glasgow Outcome Scale (eGOS) of 1-5 at 180 days after the initial injury. Secondary outcomes include, among others, 28-day survival, intensive care unit (ICU) and hospital lengths of stay, the occurrence of extra-cerebral organ dysfunction/failure, and the development of any infection or thromboembolic events. The estimated sample size is 794 patients to demonstrate a reduction in the primary outcome from 50 to 39% between groups (397 patients in each arm). The study was initiated in 2016 in several ICUs and will be completed in December 2022.

DISCUSSION

This trial will assess the impact of a liberal versus conservative strategy of blood transfusion in a large cohort of critically ill patients with a primary acute brain injury. The results of this trial will help to improve blood product and transfusion use in this specific patient population and will provide additional data in some subgroups of patients at high risk of brain ischemia, such as those with intracranial hypertension or cerebral vasospasm.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02968654.

Calculating and selecting fluid therapy and blood product replacements for horses with acute hemorrhage

BACKGROUND

Blood products, crystalloids, and colloid fluids are used in the medical treatment of severe hemorrhage in horses with a goal of providing sufficient blood flow and oxygen delivery to vital organs. The fluid treatments for hemorrhage will vary depending upon severity and duration and whether hemorrhage is controlled or uncontrolled.

DESCRIPTION

With acute and severe controlled hemorrhage, treatment is focused on rapidly increasing perfusion pressure and blood flow to vital organs. This can most easily be accomplished in field cases by the administration of hypertonic saline. If isotonic crystalloids are used for resuscitation, the volume administered should be at least as great as the estimated blood loss. Following crystalloid resuscitation, clinical signs, HCT, and laboratory evidence of tissue hypoxia may help determine the need for a whole blood transfusion. In uncontrolled hemorrhage, crystalloid resuscitation is often more conservative and is referred to as "permissive hypotension." The goal of "permissive hypotension" would be to provide enough perfusion pressure to vital organs such that function is maintained while keeping blood pressure below the normal range in the hope that clot formation will not be disrupted. Whole blood and fresh frozen plasma in addition to aminocaproic acid are indicated in most horses with severe uncontrolled hemorrhage.

SUMMARY

Blood transfusion is a life-saving treatment for severe hemorrhage in horses. No precise HCT serves as a transfusion trigger; however, an HCT < 15%, lack of appropriate clinical response, or significant improvement in plasma lactate following crystalloid resuscitation and loss of 25% or more of blood volume is suggestive of the need for whole blood transfusion. Mathematical formulas may be used to estimate the amount of blood required for transfusion following severe but controlled hemorrhage, but these are not very accurate and, in practice, transfusion volume should be approximately 40% of estimated blood loss.

KEY POINTS

Modest hemorrhage, <15% of blood volume (<12 mL/kg), can be fully compensated by physiological mechanisms and generally does not require fluid or blood product therapy. More severe hemorrhage, >25% of blood volume (> 20 mL/kg), often requires crystalloid or blood product replacement, while acute loss of greater than 30% (>24 mL/kg) of blood volume may result in hemorrhagic shock requiring resuscitation treatments Uncontrolled hemorrhage is a common occurrence in equine practice, and is most commonly associated with abdominal bleeding (eg, uterine artery rupture in mares). If the hemorrhage can be controlled such as by ligation of a bleeding vessel, then initial efforts to resuscitate the horse should focus on increasing perfusion pressure and blood flow to organs as quickly as possible with crystalloids or colloids while assessing need for whole blood transfusion. While fluid therapy is being administered every effort to physically control hemorrhage should be made using ligatures, application of compression, surgical methods, and local hemostatic agents like collagen-, gelatin-, and cellulose-based products, fibrin, yunnan baiyao (YB), and synthetic glues Although some synthetic colloids have been shown to be associated with acute kidney injury in people receiving resuscitation therapy,²⁰ this undesirable effect in horses has not been reported.

Epidemiology of Bleeding in Critically Ill Children

Objective: Bleeding can be a severe complication of critical illness, but its true epidemiologic impact on children has seldom been studied. Our objective is to describe the epidemiology of bleeding in critically ill children, using a validated clinical tool, as well as the hemostatic interventions and clinical outcomes associated with bleeding. Design: Prospective observational cohort study. Setting: Tertiary pediatric critical care unit Patients: All consecutive patients (1 month to 18 years of age) admitted to a tertiary pediatric critical care unit Measurements and Main Results: Bleeding events were categorized as minimal, moderate, severe, or fatal, according to the Bleeding Assessment Scale in Critically Ill Children. We collected demographics and severity at admission, as evaluated by the Pediatric Index of Mortality. We used regression models to compare the severity of bleeding with outcomes adjusting for age, surgery, and severity. Over 12 months, 902 critically ill patients were enrolled. The median age was 64 months (IQR 17; 159), the median admission predicted risk of mortality was 0.5% (IQR 0.2; 1.4), and 24% were post-surgical. Eighteen percent of patients experienced at least one bleeding event. The highest severity of bleeding was minimal for 7.9% of patients, moderate for 5.8%, severe for 3.8%, and fatal for 0.1%. Adjusting for age, severity at admission, medical diagnosis, type of surgery, and duration of surgery, bleeding severity was independently associated with fewer ventilator-free days (p < 0.001) and fewer PICU-free days (p < 0.001). Adjusting for the same variables, bleeding severity was independently associated with an increased risk of mortality (adjusted odds ratio for each bleeding category 2.4, 95% CI 1.5; 3.7, p < 0.001). Conclusion: Our data indicate bleeding occurs in nearly one-fifth of all critically ill children, and that higher severity of bleeding was independently associated with worse clinical outcome. Further multicenter studies are required to better understand the impact of bleeding in critically ill children.

Changes in central venous oxygen saturation, lactates, and ST segment changes in a V lead ECG with changes in hemoglobin in neurosurgical patients undergoing craniotomy and tumor excision: A prospective observational study

Background and Aims:

The aim of the study was to observe the trends in central venous oxygen saturation (ScvO₂), lactate, and ST segment changes with change in hemoglobin in patients undergoing acute blood loss during surgery and to assess their role as blood transfusion trigger.

Material and Methods:

Seventy-seven consecutive patients undergoing craniotomy at a tertiary care institution were recruited for this study after obtaining written, informed consent. After establishing standard monitoring, anesthesia was induced with standard anesthetic protocol. Hemodynamic parameters such as heart rate, blood pressure (mean, systolic, diastolic), pulse pressure variation (PPV), and physiological parameters such as lactate, ScvO₂, ST segment changes were checked at baseline, before and after blood transfusion and at the end of the procedure.

Statistical Analysis:

Comparison of the mean and standard deviation for the hemodynamic parameters was performed between the transfused and nontransfused patient groups. Pearson correlation test was done to assess the correlation between the covariates. Receiver operating characteristic (ROC) curve was constructed for the ScvO₂ variable, which was used as a transfusion trigger and the cutoff value at 100% sensitivity and 75% specificity was constructed. Linear regression analysis was done between the change in hemoglobin and the change in ScvO₂ and change in hemoglobin and change in the ST segment.

Results:

There was a statistically significant positive correlation between the change in ScvO₂ and change in hemoglobin during acute blood loss with a regression coefficient of 0.8 and also between change in ST segment and hemoglobin with a regression coefficient of –0.132. No significant change was observed with lactate. The ROC showed a ScvO₂ cutoff of 64.5% with a 100% sensitivity and 75% specificity with area under curve of 0.896 for blood transfusion requirement.

Conclusions:

We conclude that ScvO₂ and ST change may be considered as physiological transfusion triggers in patients requiring blood transfusion in the intraoperative period.

Recommendations on RBC Transfusion in General Critically Ill Children Based on Hemoglobin and/or Physiologic Thresholds From the Pediatric Critical Care Transfusion and Anemia Expertise Initiative

OBJECTIVES

To present the consensus recommendations and supporting literature for RBC transfusions in general critically ill children from the Pediatric Critical Care Transfusion and Anemia Expertise Initiative.

DESIGN

Consensus conference series of international, multidisciplinary experts in RBC transfusion management of critically ill children.

METHODS

The panel of 38 experts developed evidence-based and, when evidence was lacking, expert-based recommendations and research priorities regarding RBC transfusions in critically ill children. The subgroup on RBC transfusion in general critically ill children included six experts. Electronic searches were conducted using PubMed, EMBASE, and Cochrane Library databases from 1980 to May 30, 2017, using a combination of keywords to define concepts of RBC transfusion and critically ill children. Recommendation consensus was obtained using the Research and Development/UCLA Appropriateness Method. The results were summarized using the Grading of Recommendations Assessment, Development, and Evaluation method.

RESULTS

Three adjudicators reviewed 4,399 abstracts; 71 papers were read, and 17 were retained. Three papers were added manually. The general Transfusion and Anemia Expertise Initiative subgroup developed, and all Transfusion and Anemia Expertise Initiative members voted on two good practice statements, six recommendations, and 11 research questions; in all instances, agreement was reached (> 80%). The good practice statements suggest a framework for RBC transfusion in PICU patients. The good practice statements and recommendations focus on hemoglobin as a threshold and/or target. The research questions focus on hemoglobin and physiologic thresholds for RBC transfusion, alternatives, and risk/benefit ratio of transfusion.

CONCLUSIONS

Transfusion and Anemia Expertise Initiative developed pediatric-specific good practice statements and recommendations regarding RBC transfusion management in the general PICU population, as well as recommendations to guide future research priorities. Clinical recommendations emphasized relevant hemoglobin thresholds, and research recommendations emphasized a need for further understanding of physiologic thresholds, alternatives to RBC transfusion, and hemoglobin thresholds in populations with limited pediatric literature.

Transfusion Decision Making in Pediatric Critical Illness

Transfusion decision making (TDM) in the critically ill requires consideration of: (1) anemia tolerance, which is linked to active pathology and to physiologic reserve, (2) differences in donor RBC physiology from that of native RBCs, and (3) relative risk from anemia-attributable oxygen delivery failure vs hazards of transfusion, itself. Current approaches to TDM (e.g. hemoglobin thresholds) do not: (1) differentiate between patients with similar anemia, but dissimilar pathology/physiology, and (2) guide transfusion timing and amount to efficacy-based goals (other than resolution of hemoglobin thresholds). Here, we explore approaches to TDM that address the above gaps.

Pediatric Patient Blood Management Programs: Not Just Transfusing Little Adults

Red blood cell transfusions are a common life-saving intervention for neonates and children with anemia, but transfusion decisions, indications, and doses in neonates and children are different from those of adults. Patient blood management (PBM) programs are designed to assist clinicians with appropriately transfusing patients. Although PBM programs are well recognized and appreciated in the adult setting, they are quite far from standard of care in the pediatric patient population. Adult PBM standards cannot be uniformly applied to children, and there currently is significant variation in transfusion practices. Because transfusing unnecessarily can expose children to increased risk without benefit, it is important to design PBM programs to standardize transfusion decisions. This article assesses the key elements necessary for a successful pediatric PBM program, systematically explores various possible pediatric specific blood conservation strategies and the current available literature supporting them, and outlines the gaps in the evidence suggesting need for further/improved research. Pediatric PBM programs are critically important initiatives that not only involve a cooperative effort between pediatric surgery, anesthesia, perfusion, critical care, and transfusion medicine services but also need operational support from administration, clinical leadership, finance, and the hospital information technology personnel. These programs also expand the scope for high-quality collaborative research. A key component of pediatric PBM programs is monitoring pediatric blood utilization and assessing adherence to transfusion guidelines. Data suggest that restrictive transfusion strategies should be used for neonates and children similar to adults, but further research is needed to assess the best oxygenation requirements, hemoglobin threshold, and transfusion strategy for patients with active bleeding, hemodynamic instability, unstable cardiac disease, and cyanotic cardiac disease. Perioperative blood management strategies include minimizing blood draws, restricting transfusions, intraoperative cell salvage, acute normovolemic hemodilution, antifibrinolytic agents, and using point-of-care tests to guide transfusion decisions. However, further research is needed for the use of intravenous iron, erythropoiesis-stimulating agents, and possible use of whole blood and pathogen inactivation. There are numerous areas where newly formed collaborations could be used to investigate pediatric transfusion, and these studies would provide critical data to support vital pediatric PBM programs to optimize neonatal and pediatric care.

The Effect of Patient-Specific Cerebral Oxygenation Monitoring on Postoperative Cognitive Function: A Multicenter Randomized Controlled Trial

BACKGROUND

Indices of global tissue oxygen delivery and utilization such as mixed venous oxygen saturation, serum lactate concentration, and arterial hematocrit are commonly used to determine the adequacy of tissue oxygenation during cardiopulmonary bypass (CPB). However, these global measures may not accurately reflect regional tissue oxygenation and ischemic organ injury remains a common and serious complication of CPB. Near-infrared spectroscopy (NIRS) is a noninvasive technology that measures regional tissue oxygenation. NIRS may be used alongside global measures to optimize regional perfusion and reduce organ injury. It may also be used as an indicator of the need for red blood cell transfusion in the presence of anemia and tissue hypoxia. However, the clinical benefits of using NIRS remain unclear and there is a lack of high-quality evidence demonstrating its efficacy and cost effectiveness.

OBJECTIVE

The aim of the patient-specific cerebral oxygenation monitoring as part of an algorithm to reduce transfusion during heart valve surgery (PASPORT) trial is to determine whether the addition of NIRS to CPB management algorithms can prevent cognitive decline, postoperative organ injury, unnecessary transfusion, and reduce health care costs.

METHODS

Adults aged 16 years or older undergoing valve or combined coronary artery bypass graft and valve surgery at one of three UK cardiac centers (Bristol, Hull, or Leicester) are randomly allocated in a 1:1 ratio to either a standard algorithm for optimizing tissue oxygenation during CPB that includes a fixed transfusion threshold, or a patient-specific algorithm that incorporates cerebral NIRS monitoring and a restrictive red blood cell transfusion threshold. Allocation concealment, Internet-based randomization stratified by operation type and recruiting center, and blinding of patients, ICU and ward care staff, and outcome assessors reduce the risk of bias. The primary outcomes are cognitive function 3 months after surgery and infectious complications during the first 3 months after surgery. Secondary outcomes include measures of inflammation, organ injury, and volumes of blood transfused. The cost effectiveness of the NIRS-based algorithm is described in terms of a cost-effectiveness acceptability curve. The trial tests the superiority of the patient-specific algorithm versus standard care. A sample size of 200 patients was chosen to detect a small to moderate target difference with 80% power and 5% significance (two tailed).

RESULTS

Over 4 years, 208 patients have been successfully randomized and have been followed up for a 3-month period. Results are to be reported in 2015.

CONCLUSIONS

This study provides high-quality evidence, both valid and widely applicable, to determine whether the use of NIRS monitoring as part of a patient-specific management algorithm improves clinical outcomes and is cost effective.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Number (ISRCTN): 23557269; http://www.isrctn.com/ISRCTN23557269 (Archived by Webcite at http://www.webcitation.org/6buyrbj64).

Recovery from Extreme Hemodilution (Hemoglobin Level of 0.6 g/dL) in Cadaveric Liver Transplantation

Decompensated hepatic failure occurred in a patient with a rare blood type. The patient had extreme hemodilution due to massive bleeding during liver transplantation. A shortage of matched and universal donor blood prompted us to transfuse albumin and fresh frozen plasma for intravascular volume resuscitation. The lowest hemoglobin was 0.6 g/dL, accompanied by ST depression and a serum lactate of 100 mg/dL. The accuracy of the measured value of 0.6 g/dL was confirmed. However, the patient recovered from this critical situation after transfusion, and he was eventually discharged from the hospital without significant sequelae. Maintaining normovolemia, administering pure oxygen, ensuring appropriate anesthetic depth, and maintaining minimal inotropic support were essential for this patient's survival during massive bleeding.

Intravenous iron administration and hypophosphatemia in clinical practice

Introduction. Parenteral iron formulations are frequently used to correct iron deficiency anemia (IDA) and iron deficiency (ID). Intravenous formulation efficacy on ferritin and hemoglobin level improvement is greater than that of oral formulations while they are associated with lower gastrointestinal side effects. Ferric carboxymaltose- (FCM-) related hypophosphatemia is frequent and appears without clinical significance. The aim of this study was to assess the prevalence, duration, and potential consequences of hypophosphatemia after iron injection. Patients and Methods. The medical records of all patients who underwent parenteral iron injection between 2012 and 2014 were retrospectively reviewed. Pre- and postinjection hemoglobin, ferritin, plasma phosphate, creatinine, and vitamin D levels were assessed. Patients who developed moderate (range: 0.32–0.80 mmol/L) or severe (<0.32 mmol/L) hypophosphatemia were questioned for symptoms. Results. During the study period, 234 patients received iron preparations but 104 were excluded because of missing data. Among the 130 patients included, 52 received iron sucrose (FS) and 78 FCM formulations. Among FS-treated patients, 22% developed hypophosphatemia versus 51% of FCM-treated patients, including 13% who developed profound hypophosphatemia. Hypophosphatemia severity correlated with the dose of FCM (p = 0.04) but not with the initial ferritin, hemoglobin, or vitamin D level. Mean hypophosphatemia duration was 6 months. No immediate clinical consequence was found except for persistent fatigue despite anemia correction in some patients. Conclusions. Hypophosphatemia is frequent after parenteral FCM injection and may have clinical consequences, including persistent fatigue. Further studies of chronic hypophosphatemia long-term consequences, especially bone assessments, are needed.

Transfusion of Blood and Blood Products

In transfusion medicine, several blood products can be prepared and used as replacement therapy; however, four of these products are more commonly used in general practice: RBCs, fresh frozen plasma (FFP), platelets and cryoprecipitate. RBC transfusions are mainly administered to improve tissue oxygenation in cases of anaemia or acute blood loss due to trauma or surgery. FFP, platelets and cryoprecipitate are used for the prevention and treatment of bleeding.

Transfusion strategy: impact of haemodynamics and the challenge of haemodilution

Blood transfusion is associated with increased morbidity and mortality and numerous reports have emphasised the need for reduction. Following this there is increased attention to the concept of patient blood management. However, bleeding is relatively common following cardiac surgery and is further enhanced by the continued antiplatelet therapy policy. Another important issue is that cardiopulmonary bypass leads to haemodilution and a potential blood loss. The basic role of blood is oxygen transport to the organs. The determining factors of oxygen delivery are cardiac output, haemoglobin, and saturation. If oxygen delivery/consumption is out of balance, the compensation mechanisms are simple, as a decrease in one factor results in an increase in one or two other factors. Patients with coexisting cardiac diseases may be of particular risk, but studies indicate that patients with coexisting cardiac diseases tolerate moderate anaemia and may even benefit from a restrictive transfusion regimen. Further it has been shown that patients with reduced left ventricular function are able to compensate with increased cardiac output in response to bleeding and haemodilution if normovolaemia is maintained. In conclusion the evidence supports that each institution establishes its own patient blood management strategy to both conserve blood products and maximise outcome.

Evidence review: periprocedural use of blood products

Blood product transfusion has not been subject to rigorous clinical study, and great practice variations exist. Of particular concern to hospitalists is the use of red blood cells, plasma, and platelets prior to invasive procedures to correct anemia or perceived bleeding risk. We summarize the known risks associated with periprocedural anemia, prolonged international normalized ratio (INR), and thrombocytopenia, as well as the effects of blood product administration on clinical outcomes. Clinical trial evidence argues for a restrictive red blood cell transfusion threshold (a hemoglobin level of 7-8 g/dL or symptomatic anemia) for most perioperative patients. There are no high-quality data to guide plasma and platelet transfusions around the time of procedures. Available data do not support the use of prothrombin time/INR to guide prophylactic administration of plasma, and there are scarce data to guide platelet use around the time of an invasive procedure. Therefore, we rely on current consensus expert opinion, which recommends administration of plasma in moderate- to high-risk procedures when INR is >1.5. We recommend platelet transfusion in low-risk procedures when platelet count is <20,000/μL, for average-risk procedures when platelet count is <50,000/μL, and for procedures involving the central nervous system when the platelet count is <100,000/μL.

Accuracy of formulas used to predict post-transfusion packed cell volume rise in anemic dogs

OBJECTIVE

To assess the accuracy of published formulas used to guide packed red blood cell (pRBC) transfusions in anemic dogs and to compare the predicted rise in packed cell volume (PCV) to the actual post-transfusion rise in PCV.

DESIGN

Prospective observational study from April 2009 through July 2009.

SETTING

A small animal emergency and specialty hospital.

ANIMALS

Thirty-one anemic client-owned dogs that received pRBC transfusions for treatment of anemia.

INTERVENTIONS

None

MEASUREMENTS

Four formulas were evaluated to determine their predictive ability with respect to rise in PCV following transfusion with pRBC. Post-transfusion rise in PCV were compared to calculated rise in PCV using 4 different formulas. Bias and limits of agreement were investigated using Bland-Altman analyses.

RESULTS

Accuracy of existing formulas to predict rise in PCV following transfusion varied significantly. Formula 1 (volume to be transfused [VT] [mL] = 1 mL × % PCV rise × kg body weight [BW]) overestimated the expected rise in PCV (mean difference, 6.30), while formula 2 (VT [mL] = 2 mL ×% PCV rise × kg BW) underestimated the rise in PCV (mean difference, -3.01). Formula 3 (VT [mL] = 90 mL × kg BW × [(desired PCV - Patient PCV)/PCV of donor blood]) and formula 4 (VT [mL] = 1.5 mL ×% PCV rise × kg BW) performed well (mean difference 0.23 and 0.09, respectively) in predicting rise in PCV following pRBC transfusion.

CONCLUSIONS

Agreement between 2 formulas, "VT (mL) = kg BW × blood volume (90 mL) × [(desired PCV - recipient PCV)/Donor PCV]" and "VT (mL) = 1.5 ×desired rise in PCV × kg BW," was found when they were compared to the actual rise in PCV following pRBC transfusion in anemic dogs. Further research is warranted to determine whether these formulas perform similarly well for other species.

High oxygen partial pressure decreases anemia-induced heart rate increase equivalent to transfusion

BACKGROUND

Anemia is associated with morbidity and mortality and frequently leads to transfusion of erythrocytes. The authors sought to directly compare the effect of high inspired oxygen fraction versus transfusion of erythrocytes on the anemia-induced increased heart rate (HR) in humans undergoing experimental acute isovolemic anemia.

METHODS

The authors combined HR data from healthy subjects undergoing experimental isovolemic anemia in seven studies performed by the group. HR changes associated with breathing 100% oxygen by nonrebreathing facemask versus transfusion of erythrocytes at their nadir hemoglobin concentration of 5 g/dl were examined. Data were analyzed using a mixed-effects model.

RESULTS

HR had an inverse linear relationship to hemoglobin concentration with a mean increase of 3.9 beats per min per gram of hemoglobin (beats/min/g hemoglobin) decrease (95% CI, 3.7-4.1 beats/min/g hemoglobin), P < 0.0001. Return of autologous erythrocytes significantly decreased HR by 5.3 beats/min/g hemoglobin (95% CI, 3.8-6.8 beats/min/g hemoglobin) increase, P < 0.0001. HR at nadir hemoglobin of 5.6 g/dl (95% CI, 5.5-5.7 g/dl) when breathing air (91.4 beats/min; 95% CI, 87.6-95.2 beats/min) was reduced by breathing 100% oxygen (83.0 beats/min; 95% CI, 79.0-87.0 beats/min), P < 0.0001. The HR at hemoglobin 5.6 g/dl when breathing oxygen was equivalent to the HR at hemoglobin 8.9 g/dl when breathing air.

CONCLUSIONS

High arterial oxygen partial pressure reverses the heart rate response to anemia, probably because of its usability rather than its effect on total oxygen content. The benefit of high arterial oxygen partial pressure has significant potential clinical implications for the acute treatment of anemia and results of transfusion trials.

Red blood cell transfusion in the critically ill patient

Red blood cell (RBC) transfusion is a common intervention in intensive care unit (ICU) patients. Anemia is frequent in this population and is associated with poor outcomes, especially in patients with ischemic heart disease. Although blood transfusions are generally given to improve tissue oxygenation, they do not systematically increase oxygen consumption and effects on oxygen delivery are not always very impressive. Blood transfusion may be lifesaving in some circumstances, but many studies have reported increased morbidity and mortality in transfused patients. This review focuses on some important aspects of RBC transfusion in the ICU, including physiologic considerations, a brief description of serious infectious and noninfectious hazards of transfusion, and the effects of RBC storage lesions. Emphasis is placed on the importance of personalizing blood transfusion according to physiological endpoints rather than arbitrary thresholds.

Low hemoglobin levels during normovolemia are associated with electrocardiographic changes in pigs

We studied whether low hemoglobin concentrations during normovolemia change the myocardial electrical current (electrocardiogram) in a pig model. Normovolemic anemia was achieved by stepwise replacing blood with colloids (hydroxyethyl starch 6%). We measured the length of the PQ-, QT-, QTc, and the ST interval as well as the amplitude of the Q wave and T wave at hemoglobin concentrations of 9.5, 8.0, 5.5, 3.8, and 3.3 g·dL. Normovolemic anemia is accompanied by a gradual prolongation of the QT and QTc interval and a reduction in the amplitude of the T wave. The QRS complex is partly diminished in amplitude. Results were verified performing a time-frequency analysis on single heartbeats. During severe anemia and normovolemia, electrocardiographic changes can be detected. Further investigations are warranted to elucidate whether these changes indicate myocardial hypoxia.

Myocardial ischaemia in sickle cell anaemia: evaluation using a new scoring system

BACKGROUND

Sickle cell anaemia (SCA) is associated with recurrent multi-organ ischaemia and infarction. Myocardial ischaemia (MI) and infarction are increasingly recognised as features of SCA. The prevalence and severity of MI in children with SCA is not known.

AIM

To evaluate the usefulness of a new scoring system based on the standard surface electrocardiogram (ECG) in determining the prevalence and severity of MI in children with SCA.

METHOD

MI prevalence and scores derived from standard surface ECGs of 35 children with SCA aged 3-18 years who presented consecutively during 38 episodes of vaso-occlusive crisis (VOC) were compared with those of 40 age- and sex-matched SCA patients in the steady state and 40 anaemic non-SCA patients. In SCA subjects with VOC, ECG was repeated approximately 1 week and 4-8 weeks post crisis and the respective MI scores were compared with their intra-crisis ECG and those of the two other groups.

RESULTS

Mean (SD) MI scores were significantly higher during vaso-occlusive crises [1·82 (0·20)] compared with the steady state [1·15 (0·15)] and non-SCA anaemic controls [1·13 (0·21)], p = 0·017. SCA patients in crisis were 5·5 (1·20-13·99) times more likely to have MI compared with non-SCA anaemic controls (p = 0·025). They were also 3·66 (1·05-12·74, p = 0·042) and 7·58 (1·31-43·92, p = 0·024) times more likely to have mild and significant MI, respectively. MI scores derived from the post-crisis ECGs were similar to those of steady-state SCA patients.

CONCLUSION

ECG changes consistent with MI are common in children with SCA, especially during vaso-occlusive crises. Our proposed MI scoring system could be a useful screening tool for early detection of significant MI during crises, facilitating early institution of intervention. Further studies are needed to determine the specificity of the observed changes and to validate the proposed screening tool.

Red blood cell transfusion in critically ill children: a narrative review

OBJECTIVE

To review the pathophysiology of anemia, as well as transfusion-related complications and indications for red blood cell (RBC) transfusion, in critically ill children. Although allogeneic blood has become increasingly safer from infectious agents, mounting evidence indicates that RBC transfusions are associated with complications and unfavorable outcomes. As a result, there has been growing interest and efforts to limit RBC transfusion, and indications are being revisited and revamped. Although a so-called restrictive RBC transfusion strategy has been shown to improve morbidity and mortality in critically ill adults, there have been relatively few studies on RBC transfusion performed in critically ill children.

DATA SOURCES

Published literature on transfusion medicine and outcomes of RBC transfusion. STUDY SELECTION, DATA EXTRACTION, AND SYNTHESIS: After a brief overview of physiology of oxygen transportation, anemia compensation, and current transfusion guidelines based on available literature, risks and outcomes of transfusion in general and in critically ill children are summarized in conjunction with studies investigating the safety of restrictive transfusion strategies in this patient population.

CONCLUSIONS

The available evidence does not support the extensive use of RBC transfusions in general or critically ill patients. Transfusions are still associated with risks, and although their benefits are established in limited situations, the associated negative outcomes in many more patients must be closely addressed. Given the frequency of anemia and its proven negative outcomes, transfusion decisions in the critically ill children should be based on individual patient's characteristics rather than generalized triggers, with consideration of potential risks and benefits, and available blood conservation strategies that can reduce transfusion needs.

Anemia in the setting of traumatic brain injury: the arguments for and against liberal transfusion

Anemia is recognized as a possible cause of secondary injury following traumatic brain injury (TBI). Cogent arguments can be made for both liberal and restrictive blood transfusion practices in this setting. In this narrative review, we summarize available knowledge regarding the risks of anemia and transfusion in patients with TBI. Laboratory studies using animal models and healthy human subjects suggest that anemia below a hemoglobin (Hb) concentration of 7 g/dL results in impaired brain function and below 10 g/dL may be detrimental to recovery from TBI. Clinical studies that have evaluated the association of anemia with clinical outcomes have not consistently demonstrated harm, but they generally have important methodological weaknesses. Alternatively, studies that have analyzed transfusion as a predictor of worse outcome have consistently identified such an association, but these studies may involve residual confounding. What little information exists from randomized trials that have included patients with TBI and evaluated liberal versus restrictive transfusion strategies is inconclusive. Since anemia in the setting of TBI is relatively common and there is considerable variation in transfusion preferences, greater study of this topic - preferably with one or more rigorous, adequately powered, non-inferiority randomized trials - is desirable.

Strategy of transfusion in cardiac surgery: limits of hematocrit and how much is too low?

The use of blood and blood products in cardiac surgery is higher than necessary and a reduction is imperative due to complications and costs. Hemodilution is unavoidable in cardiopulmonary bypass and is the most likely pitfall when evaluating transfusion needs. Even patients with coexisting cardiovascular diseases tolerate perioperative hemodilution better than most anticipate. Hemodynamic monitoring is important to evaluate the association between hemoglobin level and organ function. Use of both mechanical and medical blood conservation strategies is required to reduce blood transfusion, and most of the methods have a positive cost-effectiveness and cost-benefit. By using the right strategy and policy, transfusion of blood and blood products can be reduced to less than 5% of cardiac patients.

Venous oxygen saturation as a physiologic transfusion trigger

This article is one of ten reviews selected from the Yearbook of Intensive Care and Emergency Medicine 2010 (Springer Verlag) and co-published as a series in Critical Care . Other articles in the series can be found online at http://ccforum.com/series/yearbook . Further information about the Yearbook of Intensive Care and Emergency Medicine is available from http://www.springer.com/series/2855 .

Anemia and RBC Transfusion

Anemia is common in critically ill patients. More than 90% of patients have subnormal hemoglobin by the third day of ICU admission. Despite the fact that blood transfusions have not been shown to improve the outcome of ICU patients (see below) and that the current guidelines recommend blood transfusion only when the hemoglobin falls below 7.0 g/dl, almost half of all patients admitted to an ICU receive a blood transfusion.^1,2 The etiology of anemia of critical illness is multi-factorial and complex. Repeated phlebotomy, gastrointestinal blood loss, and other surgical procedures contribute significantly to the development of anemia. Red cell production in critically ill patients is often abnormal and is involved in the development and maintenance of anemia. The pathophysiology of this anemia includes decreased production of erythropoietin (EPO), impaired bone marrow response to erythropoietin, and reduced red cell survival.

Anemia in the preoperative patient

Anemia is commonly encountered in the preoperative patient. Determination of the cause of the anemia can affect perioperative surgical and medical management and outcome. Red blood cell transfusions are often administered during the perioperative time period in patients with preoperative anemia, although evidence to support the optimal transfusion threshold is limited. The authors review the evaluation of anemia and evidence regarding perioperative blood transfusions. Recommendations on the treatment of anemia, including perioperative blood transfusions, are outlined.

Anemia in the preoperative patient

Anemia is commonly encountered in the preoperative patient. Determination of the cause of the anemia can affect perioperative surgical and medical management and outcome. Red blood cell transfusions are often administered during the perioperative time period in patients with preoperative anemia, although evidence to support the optimal transfusion threshold is limited. The authors review the evaluation of anemia and evidence regarding perioperative blood transfusions. Recommendations on the treatment of anemia, including perioperative blood transfusions, are outlined.

[Contribution of central venous oxygen saturation in postoperative blood transfusion decision]

OBJECTIVE

The aim of this study was to assess the value of central venous oxygen saturation (ScvO(2)) for the decision of blood transfusion in comparison with the criteria of the French guidelines for blood transfusion (2003).

STUDY DESIGN

Prospective, observational.

PATIENTS AND METHODS

Sixty patients, haemodynamically stable, for whom a blood transfusion (BT) was discussed in the postoperative course of general surgery, were included. ScvO(2) (%) and haemoglobin (g/dl) were measured before and after BT. Patients were retrospectively divided into two groups according to ScvO(2) measured before BT (< or >or=70%). Results are expressed as median.

RESULTS

The ScvO(2) before transfusion was greater or equal to 70% in 25 (47.2%) patients. Following BT, the ScvO(2) increased significantly (from 57.8 to 68.5%) in the group with initial ScvO(2) less than 70% whereas it was unchanged in patients with initial ScvO(2) greater or equal 70% (from 76.8 to 76.5%). Twenty patients (37.7%) did not meet the French guidelines for BT criteria. Eighteen patients out of 33 that met the criteria had ScvO(2) greater or equal 70% before BT while 13 patients with ScvO(2) less than 70% were not detected by these same criteria.

CONCLUSION

ScvO(2) could be a relevant biological parameter to complete the current guidelines for BT in stable patient with a central venous catheter during the postoperative period.

Efficacy of red blood cell transfusion in the critically ill: a systematic review of the literature

BACKGROUND

Red blood cell (RBC) transfusions are common in intensive care unit, trauma, and surgical patients. However, the hematocrit that should be maintained in any particular patient because the risks of further transfusion of RBC outweigh the benefits remains unclear.

OBJECTIVE

A systematic review of the literature to determine the association between red blood cell transfusion, and morbidity and mortality in high-risk hospitalized patients.

DATA SOURCES

MEDLINE, Embase, Cochrane Register of Controlled Trials, and citation review of relevant primary and review articles.

STUDY SELECTION

Cohort studies that assessed the independent effect of RBC transfusion on patient outcomes. From 571 articles screened, 45 met inclusion criteria and were included for data extraction.

DATA EXTRACTION

Forty-five studies including 272,596 were identified (the outcomes from one study were reported in four separate publications). The outcome measures were mortality, infections, multiorgan dysfunction syndrome, and acute respiratory distress syndrome. The overall risks vs. benefits of RBC transfusion on patient outcome in each study was classified as (i) risks outweigh benefits, (ii) neutral risk, and (iii) benefits outweigh risks. The odds ratio and 95% confidence interval for each outcome measure was recorded if available. The pooled odds ratios were determined using meta-analytic techniques.

DATA SYNTHESIS

Forty-five observational studies with a median of 687 patients/study (range, 63-78,974) were analyzed. In 42 of the 45 studies the risks of RBC transfusion outweighed the benefits; the risk was neutral in two studies with the benefits outweighing the risks in a subgroup of a single study (elderly patients with an acute myocardial infarction and a hematocrit <30%). Seventeen of 18 studies, demonstrated that RBC transfusions were an independent predictor of death; the pooled odds ratio (12 studies) was 1.7 (95% confidence interval, 1.4-1.9). Twenty-two studies examined the association between RBC transfusion and nosocomial infection; in all these studies blood transfusion was an independent risk factor for infection. The pooled odds ratio (nine studies) for developing an infectious complication was 1.8 (95% confidence interval, 1.5-2.2). RBC transfusions similarly increased the risk of developing multi-organ dysfunction syndrome (three studies) and acute respiratory distress syndrome (six studies). The pooled odds ratio for developing acute respiratory distress syndrome was 2.5 (95% confidence interval, 1.6-3.3).

CONCLUSIONS

Despite the inherent limitations in the analysis of cohort studies, our analysis suggests that in adult, intensive care unit, trauma, and surgical patients, RBC transfusions are associated with increased morbidity and mortality and therefore, current transfusion practices may require reevaluation. The risks and benefits of RBC transfusion should be assessed in every patient before transfusion.

Anemia of Inflammation in Critically Ill Patients

Anemia is seen frequently in critically ill patients and has several etiologies. This article reviews the causes with an emphasis on the effects of inflammation, examines the risks and benefits of current therapies, and discusses novel treatment options.

Increased mortality, postoperative morbidity, and cost after red blood cell transfusion in patients having cardiac surgery

BACKGROUND

Red blood cell transfusion can both benefit and harm. To inform decisions about transfusion, we aimed to quantify associations of transfusion with clinical outcomes and cost in patients having cardiac surgery.

METHODS AND RESULTS

Clinical, hematology, and blood transfusion databases were linked with the UK population register. Additional hematocrit information was obtained from intensive care unit charts. Composite infection (respiratory or wound infection or septicemia) and ischemic outcomes (myocardial infarction, stroke, renal impairment, or failure) were prespecified as coprimary end points. Secondary outcomes were resource use, cost, and survival. Associations were estimated by regression modeling with adjustment for potential confounding. All adult patients having cardiac surgery between April 1, 1996, and December 31, 2003, with key exposure and outcome data were included (98%). Adjusted odds ratios for composite infection (737 of 8516) and ischemic outcomes (832 of 8518) for transfused versus nontransfused patients were 3.38 (95% confidence interval [CI], 2.60 to 4.40) and 3.35 (95% CI, 2.68 to 4.35), respectively. Transfusion was associated with increased relative cost of admission (any transfusion, 1.42 times [95% CI, 1.37 to 1.46], varying from 1.11 for 1 U to 3.35 for >9 U). At any time after their operations, transfused patients were less likely to have been discharged from hospital (hazard ratio [HR], 0.63; 95% CI, 0.60 to 0.67) and were more likely to have died (0 to 30 days: HR, 6.69; 95% CI, 3.66 to 15.1; 31 days to 1 year: HR, 2.59; 95% CI, 1.68 to 4.17; >1 year: HR, 1.32; 95% CI, 1.08 to 1.64).

CONCLUSIONS

Red blood cell transfusion in patients having cardiac surgery is strongly associated with both infection and ischemic postoperative morbidity, hospital stay, increased early and late mortality, and hospital costs.

Physiologic transfusion triggers

In clinical practice, the decision to transfuse is linked to the hope of increasing oxygen transport (TO2) to tissues. Physiologic transfusion triggers should progressively replace arbitrary hemoglobin-based transfusion triggers. These 'physiologic' transfusion triggers can be based on signs and symptoms of impaired global oxygenation (lactate, venous O2 saturation [SvO2]) or, even better, of regional tissue oxygenation (electrocardiographic ST-segment, electroencephalographic P300 latency). The SvO2 or its surrogate, the central venous 02 saturation (ScvO2), is a clinical tool which integrates the relationship between whole-body O2 uptake and TO2, and as such can be proposed as a simple physiologic transfusion trigger.

[Tolerance to perioperative anemia. Mechanisms, influencing factors and limits]

Die zu erwartende Kostensteigerung im Transfusionswesen (steigender Fremdblutbedarf bei gleichzeitig rückläufiger Spendebereitschaft, Behandlungspflicht transfusionsassoziierter Folgeerkrankungen) erhöht den sozioökonomischen Stellenwert der Entwicklung institutionsspezifischer Transfusionsprogramme. Ein wesentlicher Bestandteil hierbei ist – neben einer schonenden Operationstechnik und der konsequenten perioperativen Anwendung fremdblutsparender Maßnahmen – die Ausschöpfung der natürlicherweise vorhandenen „Anämietoleranz“ des menschlichen Organismus (Toleranz größerer Blutverluste durch Verlust von „verdünntem“ Blut, Hinauszögern des Transfusionsbeginns bis nach chirurgischer Blutstillung, Gewinnung von autologem Blut). In der vorliegenden Übersicht werden die Mechanismen, Einflussgrößen und Grenzen dieser natürlichen Anämietoleranz für den Gesamtorganismus und für einzelne Organsysteme zusammengefasst und die sich daraus ergebende Indikation zur Erythrozytentransfusion abgeleitet. Unter kontrollierten Bedingungen (Narkose, strikte Aufrechterhaltung von Normovolämie, komplette Muskelrelaxierung, Hyperoxämie, Hypothermie) werden von kardiopulmonal gesunden Individuen kurzzeitig auch extreme Grade der Verdünnungsanämie [Hämoglobin- (Hb-)Wert <3 g/dl (<1,86 mmol/l)] ohne Transfusion toleriert. In der klinischen Routine bleibt diese Situation – nicht zuletzt in Ermangelung eines adäquaten Monitorings – jedoch auf spezielle Sonderfälle beschränkt (z. B. unerwartete große Blutverluste bei Zeugen Jehovahs, unerwarteter Engpass bei der Bereitstellung von Fremdblut). Die derzeit geltenden Empfehlungen verschiedener Expertenkommissionen decken sich dahingehend, dass perioperativ (1) bis zu einer Hb-Konzentration von 10 g/dl (6,21 mmol/l) auch bei alten Patienten und Patienten mit kardiopulmonalen Begleiterkrankungen eine Transfusion von Erythrozyten in der Regel nicht notwendig ist und (2) eine Transfusion bei jungen, gesunden Patienten ohne kardiopulmonale Vorerkrankungen (einschließlich Schwangeren und Kindern) erst ab einer Hb-Konzentration von <6 g/dl (<3,72 mmol/l) notwendig wird. Auch beatmete Intensivpatienten mit Polytrauma und Sepsis scheinen nicht von einer Transfusion auf Hb-Konzentration >9 g/dl (>5,59 mmol/l) zu profitieren. Bei massiven Blutverlusten und diffuser Blutungsneigung scheint ein Hb von 10 g/dl (6,21 mmol/l) zur Stabilisierung der Blutgerinnung beizutragen.

Blood tranfusion in critically ill patients: state of the art

Anemia is one of the most common abnormal findings in critically ill patients, and many of these patients will receive a blood transfusion during their intensive care unit stay. However, the determinants of exactly which patients do receive transfusions remains to be defined and have been the subject of considerable debate in recent years. Concerns and doubts have emerged regarding the benefits and safety of blood transfusion, in part due to the lack of evidence of better outcomes resulting from randomized studies and in part related to the observations that transfusion may increase the risk of infection. As a result of these concerns and of several studies suggesting better or similar outcomes with a lower transfusion trigger, there has been a general tendency to decrease the transfusion threshold from the classic 10 g/dL to lower values. In this review, we focus on some of the key studies providing insight into current transfusion practices and fueling the current debate on the ideal transfusion trigger.

[Tolerance to perioperative anemia. Mechanisms, influencing factors and limits]

Die zu erwartende Kostensteigerung im Transfusionswesen erhöht den sozioökonomischen Stellenwert der Entwicklung institutionsspezifischer Transfusionsprogramme. Ein wesentlicher Bestandteil hierbei ist – neben einer schonenden Operationstechnik und der konsequenten perioperativen Anwendung fremdblutsparender Maßnahmen – die Ausschöpfung der natürlichen „Anämietoleranz“ des menschlichen Organismus. Im vorliegenden Beitrag werden die Mechanismen, Einflussgrößen und Grenzen dieser Anämietoleranz für den Gesamtorganismus und für einzelne Organsysteme zusammengefasst und die sich daraus ergebende Indikation zur Erythrozytentransfusion abgeleitet. Die derzeit geltenden Empfehlungen decken sich dahingehend, dass bis zu einer Hämoglobinkonzentration von 10 g/dl (6,21 mmol/l) auch bei alten Patienten oder kardiopulmonalen Begleiterkrankungen eine perioperative Transfusion in der Regel nicht notwendig ist und bei jungen, gesunden Patienten ohne kardiopulmonale Vorerkrankungen (einschließlich Schwangeren und Kindern) erst ab <6 g/dl (<3,72 mmol/l) notwendig wird. Auch beatmete Intensivpatienten mit Polytrauma und Sepsis scheinen nicht von einer Transfusion auf eine Hämoglobinkonzentration >9 g/dl (>5,59 mmol/l) zu profitieren. Bei massiven Blutverlusten und diffuser Blutungsneigung scheint ein Wert von 10 g/dl (6,21 mmol/l) zur Stabilisierung der Blutgerinnung beizutragen.