A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group. Influence of hematocrit on cardiopulmonary function after acute hemorrhage. Effect of early blood transfusion on gastrointestinal haemorrhage. Liberal or restrictive transfusion in high-risk patients after hip surgery. A pilot randomized trial comparing symptomatic vs. hemoglobin-level-driven red blood cell transfusions following hip fracture. Transfusion strategies for patients in pediatric intensive care units. Transfusion requirements after cardiac surgery: the TRACS randomized controlled trial. The effects of liberal versus restrictive transfusion thresholds on ambulation after hip fracture surgery. Predonated autologous blood transfusions after total knee arthroplasty: immediate versus delayed administration. A randomized comparison of transfusion triggers in elective orthopaedic surgery using leucocyte-depleted red blood cells. The illness of trauma. Lowering the hemoglobin threshold for transfusion in coronary artery bypass procedures: effect on patient outcome. Transfusion requirements in critical care. A pilot study. Canadian Critical Care Trials Group. A multicenter pilot-randomized controlled trial of the feasibility of an augmented red blood cell transfusion strategy for patients treated with induction chemotherapy for acute leukemia or stem cell transplantation. Silent myocardial ischaemia and haemoglobin concentration: a randomized controlled trial of transfusion strategy in lower limb arthroplasty. A prospective, randomized trial limiting perioperative red blood cell transfusions in vascular patients. Comparison of two transfusion strategies after elective operations for myocardial revascularization. The effect of red blood cell transfusion on cerebral oxygenation and metabolism after severe traumatic brain injury.
To determine whether a restrictive strategy of red-cell transfusion and a liberal strategy produced equivalent results in critically ill patients, we compared the rates of death from all causes at 30 days and the severity of organ dysfunction.
                We enrolled 838 critically ill patients with euvolemia after initial treatment who had hemoglobin concentrations of less than 9.0 g per deciliter within 72 hours after admission to the intensive care unit and randomly assigned 418 patients to a restrictive strategy of transfusion, in which red cells were transfused if the hemoglobin concentration dropped below 7.0 g per deciliter and hemoglobin concentrations were maintained at 7.0 to 9.0 g per deciliter, and 420 patients to a liberal strategy, in which transfusions were given when the hemoglobin concentration fell below 10.0 g per deciliter and hemoglobin concentrations were maintained at 10.0 to 12.0 g per deciliter.
                Overall, 30-day mortality was similar in the two groups (18.7 percent vs. 23.3 percent, P= 0.11). However, the rates were significantly lower with the restrictive transfusion strategy among patients who were less acutely ill -- those with an Acute Physiology and Chronic Health Evaluation II score of < or =20 (8.7 percent in the restrictive-strategy group and 16.1 percent in the liberal-strategy group; P=0.03) -- and among patients who were less than 55 years of age (5.7 percent and 13.0 percent, respectively; P=0.02), but not among patients with clinically significant cardiac disease (20.5 percent and 22.9 percent, respectively; P=0.69). The mortality rate during hospitalization was significantly lower in the restrictive-strategy group (22.3 percent vs. 28.1 percent, P=0.05).
                A restrictive strategy of red-cell transfusion is at least as effective as and possibly superior to a liberal transfusion strategy in critically ill patients, with the possible exception of patients with acute myocardial infarction and unstable angina. The 'optimal' hematocrit to which patients should be resuscitated after shock and trauma is controversial. To test the hypothesis that sufficient oxygen delivery can be provided at a lower hematocrit without impairing oxygen consumption or hemodynamic function, 25 patients were prospectively studied immediately following injury and/or acute hemorrhage. Patients were randomized to have their hematocrits (HCT) maintained near 30% (29.7 +/- 0.4% (M +/- SEM); n = 12) or 40% (38.4 +/- 0.6%, n = 13). Cardiopulmonary parameters were measured twice a day for 3 days. Statistical analysis used a repeated measures analysis of variance with patient age, and ventilator parameters (FIO2, PEEP, and ventilator mode) as covariates. Arterial and venous O2 saturations were not significantly different at different hematocrits, although arterial and venous O2 contents were lower at 30% HCT (a = 14.1 +/- 0.2 m10(2)/dl, v = 10.1 +/- 0.3 m10(2)/dl; vs. a = 17.4 +/- 0.4 m10(2)/dl, v = 13.6 +/- 0.6 m10(2)/dl; p less than 0.05). This resulted in a lower oxygen delivery at the lower HCT. Between the two groups, there also was no significant difference in cardiac index (overall mean, 3.64 +/- 0.16 ml/min/m2), heart rate (99 +/- 4 bpm), systemic vascular resistance (1,058 +/- 55 dyne-sec/cm5), or left ventricular stroke work index (4.3 +/- 0.3 X 10(6) dyne-cm/m2). Intrapulmonary shunt was higher with higher hematocrit (22.6 +/- 2.4% at 40% HCT vs. 14.6 +/- 1.6% at 30% HCT; p less than 0.05) with no difference in end-expiratory pressure.(ABSTRACT TRUNCATED AT 250 WORDS) The effect of citrated stored blood on coagulation was studied initially in a pilot study where 25 patients with acute severe gastrointestinal haemorrhage had their whole blood coagulation measured using the Biobridge Impedance Clotting Time (ICT). This demonstrated that there is a hypercoagulable response to haemorrhage which was partially reversed by blood transfusion. Similar changes were noted in Kaolin Cephalin Clotting Times (KCCT). A further 50 patients were then randomized to receive, during the 24 h after admission, either at least 2 units of blood or no blood transfusion unless the haemoglobin fell below 8 g/dl or they were shocked. In the transfused group nine patients re-bled compared with only one in the non-transfused group (P less than 0.01, chi 2 with Yates' correction). Early blood transfusion appears to reverse the hypercoagulable response to haemorrhage thereby encouraging re-bleeding and hence the need for an operation. The hemoglobin threshold at which postoperative red-cell transfusion is warranted is controversial. We conducted a randomized trial to determine whether a higher threshold for blood transfusion would improve recovery in patients who had undergone surgery for hip fracture.
                We enrolled 2016 patients who were 50 years of age or older, who had either a history of or risk factors for cardiovascular disease, and whose hemoglobin level was below 10 g per deciliter after hip-fracture surgery. We randomly assigned patients to a liberal transfusion strategy (a hemoglobin threshold of 10 g per deciliter) or a restrictive transfusion strategy (symptoms of anemia or at physician discretion for a hemoglobin level of <8 g per deciliter). The primary outcome was death or an inability to walk across a room without human assistance on 60-day follow-up.
                A median of 2 units of red cells were transfused in the liberal-strategy group and none in the restrictive-strategy group. The rates of the primary outcome were 35.2% in the liberal-strategy group and 34.7% in the restrictive-strategy group (odds ratio in the liberal-strategy group, 1.01; 95% confidence interval [CI], 0.84 to 1.22), for an absolute risk difference of 0.5 percentage points (95% CI, -3.7 to 4.7). The rates of in-hospital acute coronary syndrome or death were 4.3% and 5.2%, respectively (absolute risk difference, -0.9%; 99% CI, -3.3 to 1.6), and rates of death on 60-day follow-up were 7.6% and 6.6%, respectively (absolute risk difference, 1.0%; 99% CI, -1.9 to 4.0). The rates of other complications were similar in the two groups.
                A liberal transfusion strategy, as compared with a restrictive strategy, did not reduce rates of death or inability to walk independently on 60-day follow-up or reduce in-hospital morbidity in elderly patients at high cardiovascular risk. (Funded by the National Heart, Lung, and Blood Institute; FOCUS ClinicalTrials.gov number, NCT00071032.). The indications for transfusion have never been evaluated in an adequately sized clinical trial. A pilot study was conducted to plan larger clinical trials.
                Hip fracture patients undergoing surgical repair who had postoperative hemoglobin levels less than 10 g per dL were randomly assigned to receive 1) symptomatic transfusion: that is, transfusion for symptoms of anemia or for a hemoglobin level that dropped below 8 g per dL or 2) threshold transfusion: that is, patients receive 1 unit of packed RBCs at the time of random assignment and as much blood as necessary to keep the hemoglobin level above 10 g per dL. Outcomes were 60-day mortality, morbidity, functional status, and place of residence.
                Among 84 eligible patients enrolled, mean (+/- SD) prerandomization hemoglobin was 9.1 (+/- 0.6) g/ dL. The median number of units transfused in the threshold transfusion group was 2 (interquartile range, = 1-2), and that in the symptomatic transfusion group was 0 (6; interquartile range, = 0-2) (p < 0.001). Mean hemoglobin levels were approximately 1 g per dL higher in the threshold group than in the symptomatic group: for example, on Day 2, 10.3 (+/- 0.9) g per dL versus 9.3 (+/- 1.2) g per dL, respectively (p < 0.001). At 60 days, death or inability to walk across the room without assistance occurred in 16 (39.0%) of the symptomatic transfusion group and 19 (45.2%) of the threshold transfusion group. Death occurred by 60 days in 5 (11.9%) of the symptomatic transfusion group and 2 (4.8%) in the threshold transfusion group (relative risk = 2.5; 95% CI, 0.5-12.2). Other outcomes were similar for the two groups.
                Symptomatic transfusion may be an effective blood-sparing protocol associated with the transfusion of appreciably fewer units of RBCs and lower mean hemoglobin levels than are associated with the threshold transfusion policy. However, it is unknown whether these two clinical strategies have comparable mortality, morbidity, or functional status. A definitive trial is needed. The optimal hemoglobin threshold for erythrocyte transfusions in critically ill children is unknown. We hypothesized that a restrictive transfusion strategy of using packed red cells that were leukocyte-reduced before storage would be as safe as a liberal transfusion strategy, as judged by the outcome of multiple-organ dysfunction.
                In this noninferiority trial, we enrolled 637 stable, critically ill children who had hemoglobin concentrations below 9.5 g per deciliter within 7 days after admission to an intensive care unit. We randomly assigned 320 patients to a hemoglobin threshold of 7 g per deciliter for red-cell transfusion (restrictive-strategy group) and 317 patients to a threshold of 9.5 g per deciliter (liberal-strategy group).
                Hemoglobin concentrations were maintained at a mean (+/-SD) level that was 2.1+/-0.2 g per deciliter lower in the restrictive-strategy group than in the liberal-strategy group (lowest average levels, 8.7+/-0.4 and 10.8+/-0.5 g per deciliter, respectively; P<0.001). Patients in the restrictive-strategy group received 44% fewer transfusions; 174 patients (54%) in that group did not receive any transfusions, as compared with 7 patients (2%) in the liberal-strategy group (P<0.001). New or progressive multiple-organ dysfunction syndrome (the primary outcome) developed in 38 patients in the restrictive-strategy group, as compared with 39 in the liberal-strategy group (12% in both groups) (absolute risk reduction with the restrictive strategy, 0.4%; 95% confidence interval, -4.6 to 5.4). There were 14 deaths in each group within 28 days after randomization. No significant differences were found in other outcomes, including adverse events.
                In stable, critically ill children a hemoglobin threshold of 7 g per deciliter for red-cell transfusion can decrease transfusion requirements without increasing adverse outcomes. (Controlled-trials.com number, ISRCTN37246456 [controlled-trials.com].).
                Copyright 2007 Massachusetts Medical Society. Perioperative red blood cell transfusion is commonly used to address anemia, an independent risk factor for morbidity and mortality after cardiac operations; however, evidence regarding optimal blood transfusion practice in patients undergoing cardiac surgery is lacking.
                To define whether a restrictive perioperative red blood cell transfusion strategy is as safe as a liberal strategy in patients undergoing elective cardiac surgery.
                The Transfusion Requirements After Cardiac Surgery (TRACS) study, a prospective, randomized, controlled clinical noninferiority trial conducted between February 2009 and February 2010 in an intensive care unit at a university hospital cardiac surgery referral center in Brazil. Consecutive adult patients (n = 502) who underwent cardiac surgery with cardiopulmonary bypass were eligible; analysis was by intention-to-treat.
                Patients were randomly assigned to a liberal strategy of blood transfusion (to maintain a hematocrit ≥30%) or to a restrictive strategy (hematocrit ≥24%).
                Composite end point of 30-day all-cause mortality and severe morbidity (cardiogenic shock, acute respiratory distress syndrome, or acute renal injury requiring dialysis or hemofiltration) occurring during the hospital stay. The noninferiority margin was predefined at -8% (ie, 8% minimal clinically important increase in occurrence of the composite end point).
                Hemoglobin concentrations were maintained at a mean of 10.5 g/dL (95% confidence interval [CI], 10.4-10.6) in the liberal-strategy group and 9.1 g/dL (95% CI, 9.0-9.2) in the restrictive-strategy group (P < .001). A total of 198 of 253 patients (78%) in the liberal-strategy group and 118 of 249 (47%) in the restrictive-strategy group received a blood transfusion (P < .001). Occurrence of the primary end point was similar between groups (10% liberal vs 11% restrictive; between-group difference, 1% [95% CI, -6% to 4%]; P = .85). Independent of transfusion strategy, the number of transfused red blood cell units was an independent risk factor for clinical complications or death at 30 days (hazard ratio for each additional unit transfused, 1.2 [95% CI, 1.1-1.4]; P = .002).
                Among patients undergoing cardiac surgery, the use of a restrictive perioperative transfusion strategy compared with a more liberal strategy resulted in noninferior rates of the combined outcome of 30-day all-cause mortality and severe morbidity.
                clinicaltrials.gov Identifier: NCT01021631. Perioperative anemia leads to increased morbidity and mortality and potentially inhibits rehabilitation after hip fracture surgery. As such, the optimum transfusion threshold after hip fracture surgery is unknown.
                A total of 120 elderly, cognitively intact hip fracture patients admitted from their own home were randomly assigned to receive transfusion at a hemoglobin threshold of 10.0 g per dL (liberal) versus 8.0 g per dL (restrictive) in the entire perioperative period. Patients were treated according to a well-defined multimodal rehabilitation program. Primary outcome was postoperative functional mobility measured with the cumulated ambulation score (CAS).
                Patients in the liberal group received transfusions more frequently than those in the restrictive group (44 patients vs. 22 patients; p < 0.01) and received more transfusions during hospitalization (median, 2 units [interquartile range, 1-2] vs. 1 [1-2]; p < 0.0001). There were no significant differences in postoperative rehabilitation scores (CAS: median, 9 [9-15] vs. 9 [9-13.5]; p = 0.46) or in length of stay (median, 18 days vs. 16 days, respectively; p = 0.46). There were fewer patients in the liberal transfusion group with cardiovascular complications (2% vs. 10%; p = 0.05) and a lower mortality (0% vs. 8%; p = 0.02).
                Although a liberal transfusion trigger did not result in increased ambulation scores, restrictive transfusion thresholds should be treated with caution in elderly high-risk hip fracture patients, until their safety has been proved in larger randomized studies. Efforts to avoid complications associated with transfusion of allogeneic blood have increased the use of preoperatively donated autologous blood (PAB). A major controversy has arisen: Should the same criteria be used for transfusion of autologous as allogeneic red cells? This study prospectively and randomly compared giving PAB immediately after total knee arthroplasty (TKA), beginning in the recovery room or delaying a transfusion until the patient's hemoglobin had fallen to less than a 9.0 g/dL transfusion trigger point. The results show that patients who received immediate transfusion had fewer nonsurgical complications (P < .002). Because TKAs are associated with an average blood loss of 1,400 mL, we recommend that PAB be used in the immediate postoperative period, especially in the elderly, in whom the risk for cardiac or nonsurgical complications is inherently increased. In elective orthopaedic hip- and knee replacement surgery patients, we studied the effect of implementation of a uniform transfusion policy on RBC usage.
                A randomized, controlled study. A new uniform, restrictive transfusion policy was compared with standard care, which varied among the three participating hospitals. Only prestorage leucocyte-depleted RBC(s) were used. Primary end-point was RBC usage, related to length of hospital stay. Secondary end-points were Hb levels, mobilization delay and postoperative complications.
                Six hundred and three patients were evaluated. Adherence to the protocol was over 95%. Overall mean RBC usage was 0.78 U/patient in the new policy group and 0.86 U/patient in the standard care policy group (mean difference 0.08;95% CI [-0.3; 0.2]; P = 0.53). In two hospitals, the new transfusion policy resulted in a RBC reduction of 30% (0.58U RBC/patient) (P = 0.17) and 41% (0.29 U RBC/patient) (P = 0.05) respectively. In the third hospital, however, RBC usage increased by 39% (0.31 U RBC/patient) (P = 0.02) with the new policy, due to a more restrictive standard care policy in that hospital. Length of hospital stay was not influenced by either policy.
                Implementation of a uniform transfusion protocol for elective lower joint arthroplasty patients is feasible, but does not always lead to a RBC reduction. Length of hospital stay was not affected. nan There is controversy regarding the application of transfusion triggers in cardiac surgery. The goal of this study was to determine if lowering the hemoglobin threshold for red cell (RBC) transfusion to 8 g per dL after coronary artery bypass graft surgery would reduce blood use without adversely affecting patient outcome.
                Consecutive patients (n = 428) undergoing elective primary coronary artery bypass graft surgery were randomly assigned to two groups: study patients (n = 212) received RBC transfusions in the postoperative period if the Hb level was < 8 g per dL or if predetermined clinical conditions required RBC support, and control patients (n = 216) were treated according to individual physician's orders (hemoglobin levels < 9 g/dL as the institutional guideline). Multiple demographic, procedure-related, transfusion, laboratory, and outcome data were analyzed. Questionnaires were administered for patient self-assessment of fatigue and anemia.
                Preoperative and operative clinical characteristics, as well as the intraoperative transfusion rate, were similar for both groups. There was a significant difference between the postoperative RBC transfusion rates in study (0.9 +/- 1.5 RBC units) and control (1.4 +/- 1.8 RBC units) groups (p = 0.005). There was no difference in clinical outcome, including morbidity and mortality rates, in the two groups; group scores for self-assessment of fatigue and anemia were also similar.
                A lower Hb threshold of 8 g per dL does not adversely affect patient outcome. Moreover, RBC resources can be saved without increased risk to the patient. To evaluate the effects of a restrictive and a liberal red blood cell (RBC) transfusion strategy on mortality and morbidity in critically ill patients.
                Multicenter, prospective, randomized clinical trial.
                Sixty-nine normovolemic critically ill patients admitted to one of five tertiary level intensive care units with hemoglobin values less than 90 g/L within 72 hours of admission.
                Patients were randomly allocated to one of two RBC transfusion strategies. Hemoglobin values were maintained between 100 and 120 g/L in the liberal transfusion group and between 70 and 90 g/L in the restrictive group.
                Primary diagnosis and mean +/- SD age (58.6 +/- 15 vs 59.0 +/- 21 years and Acute Physiology and Chronic Health Evaluation II score (20 +/- 6.2 vs 21 +/- 7.2) were similar in the restrictive and liberal groups, respectively. Daily hemoglobin values averaged 90 g/L in the restrictive group vs 109 g/L in the liberal group (P < .001). The restrictive group received 2.5 U per patient compared with 4.8 U per patient in the liberal group. This represents a 48% relative decrease (P < .001) in RBC units transfused per patient. The 30-day mortality rate was 24% in the restrictive group compared with 25% in the liberal group; the 95% confidence interval around the absolute difference was -19% to 21%. Similar observations were noted for intensive care unit mortality (P = .76) and 120-day mortality (P > .99). In addition, survival analysis comparing time until death in both groups did not reveal any significant difference (P = .93) between groups. Organ dysfunction scores were also similar (P = .44).
                In this small randomized trial, neither mortality nor the development of organ dysfunction was affected by the transfusion strategy, which suggests that a more restrictive approach to the transfusion of RBCs may be safe in critically ill patients. However, the study lacked power to detect small but clinically significant differences. Therefore, further investigations of RBC transfusion strategies are warranted. Anemia may be an important factor contributing to an increased risk of bleeding, particularly in patients with thrombocytopenia.
                A multicenter, single-blinded pilot randomized controlled trial (RCT) was performed to evaluate the feasibility of conducting a larger RCT to determine the effect of the hemoglobin (Hb) concentration on bleeding risk. Patients with acute leukemia receiving induction chemotherapy or those undergoing stem cell transplantation were assigned to one of two treatment groups: standard transfusion strategy (transfusion of 2 units of red blood cells [RBCs] when their Hb level was less than 80 g/L) or an augmented transfusion strategy (transfusion of 2 units of RBCs when their Hb level was less than 120 g/L).
                Sixty patients were enrolled: 29 in the control group and 31 in the experimental group. The proportions of patients experiencing clinically significant bleeding and the time to first bleed were not significantly different between the control and experimental groups. The experimental group received more RBC transfusions (transfusions/patient-day) than the control group (0.233 vs. 0.151; relative risk, 1.56; 95% confidence interval, 1.16-2.10; p = 0.003). The proportion of patient-days with platelet (PLT) transfusions was not different between the experimental and control groups. The mean number of donor exposures (PLT and RBC transfusions) was not different between experimental and control groups. Bleeding symptoms were systematically documented.
                This pilot study thus indicated that it would be feasible to enroll the required number of patients to enable the performance of a large RCT to investigate the effect of Hb on bleeding risk in thrombocytopenic patients. Red cell transfusion is commonly used in orthopaedic surgery. Evidence suggests that a restrictive transfusion strategy may be safe for most patients. However, concern has been raised over the risks of anaemia in those with ischaemic cardiac disease. Perioperative silent myocardial ischaemia (SMI) has a relatively high incidence in the elderly population undergoing elective surgery. This study used Holter monitoring to compare the effect of a restrictive and a liberal red cell transfusion strategy on the incidence of SMI in patients without signs or symptoms of ischaemic heart disease who were undergoing lower limb arthroplasty.
                We performed a multicentre, controlled trial in which 260 patients undergoing elective hip and knee replacement surgery were enrolled and randomized to transfusion triggers that were either restrictive (8 g/dl) or liberal (10 g/dl). Participants were monitored with continuous ambulatory electrocardiogram (ECG) (Holter monitoring), preoperatively for 12 h and postoperatively for 72 h. The tapes were analysed for new ischaemia by technicians blinded to treatment. The total ischaemia time in minutes was divided by the recording time in hours and an ischaemic load in min/h was calculated. Haemoglobin levels were measured preoperatively, postoperatively in the recovery room, and on days one, three and five after surgery.
                The mean postoperative haemoglobin concentration was 9.87 g/dl in the restrictive group and 11.09 g/dl in the liberal group. In the restrictive group, 34% were transfused a total of 89 red cell units, and in the liberal group 43% were given a total of 119 red cell units. A postoperative episode of silent ischaemia was experienced by 21/109 (19%) patients in the restrictive group and by 26/109 (24%) patients in the liberal group [mean difference -4.6%; 95% confidence interval (CI): -15.5% to 6%, P = 0.41). There was no significant difference (P = 0.53) between the overall ischaemic load in the restrictive group (median 0 min/h, range 0-4.18) and the liberal group (median 0 min/h, range 0-19.48). In those patients who did experience postoperative SMI, the mean ischaemic load was 0.48 min/h in the restrictive group and 1.51 min/h in the liberal group (ratio 0.32, 95% CI: 0.14-0.76, P = 0.011). The median postoperative length of hospital stay in the restrictive group was 7.3 days [range 5-11; interquartile range (IQR) 6-8] compared with 7.5 days (range 5-13; IQR 7-8) in the liberal group. The numbers were not large enough to conclude equivalence.
                In patients without preoperative evidence of myocardial ischaemia undergoing elective hip and knee replacement surgery, a restrictive transfusion strategy seems unlikely to be associated with an increased incidence of SMI. A proportion of these patients experience moderate SMI, regardless of the transfusion trigger. Use of a restrictive transfusion strategy did not increase length of hospital stay, and use of this strategy would lead to a significant reduction in red cell transfusion in orthopaedic surgery. Our data did not indicate any potential for harm in employing such a strategy in patients with no prior evidence of cardiac ischaemia who were undergoing elective orthopaedic surgery. Patients undergoing major arterial reconstruction have traditionally been transfused with red blood cells to keep hemoglobin concentrations above 10 g/dL in order to prevent anemia-induced myocardial ischemia. There are no data to support this practice. The hypothesis that vascular patients will tolerate a hemoglobin concentration of 9 g/dL was examined.
                Ninety-nine patients undergoing elective aortic and infrainguinal arterial reconstructions were prospectively randomized preoperatively to receive transfusions to maintain a hemoglobin level of either 10 g/dL or 9 g/dL.
                Despite significantly different postoperative hemoglobin levels of 11.0 +/- 1.2 versus 9.8 +/- 1.3 g/dL (P <0.0001), there were no differences in mortality or cardiac morbidity rates or length of hospital stay. There were no differences in hemodynamic parameters. Oxygen delivery was lower in the group with lower hemoglobin levels, but there was no difference in O2 consumption between the groups.
                A lower hemoglobin concentration was tolerated without adverse clinical outcome. Patients did not compensate for anemia by increased myocardial work, but by increasing O2 extraction in the peripheral tissues. We performed a prospective, randomized trial of two different strategies for postoperative packed red blood cell replacement in 39 autologous blood donors undergoing elective myocardial revascularization. The "liberal" group received blood to achieve a hematocrit value of 32%, and the "conservative" group received transfusions for a hematocrit value less than 25%. Although the groups had significantly different mean hematocrit values from the fourth postoperative hour (28.7% versus 31.2%) through the fifth postoperative day (28.4% versus 31.3%), there were no significant differences in fluid requirement, hemodynamic parameters, or hospital complications. Significantly fewer units of packed cells were required in the conservatively transfused group (20 units/20 patients) compared with the liberally transfused group (37 units/18 patients) (p = 0.012). Exercise tests were performed on the fifth and sixth postoperative days, with a transfusion being given to the conservative group between tests. Although a significant improvement in exercise endurance occurred in the conservative group receiving a transfusion (p = 0.008), no significant difference in duration or degree of exercise was demonstrated between the two groups on either day. In comparing these two groups of profoundly anemic patients, we identified no adverse consequence associated with the greater degree of hemodilution and could identify no correlation between hematocrit value and exercise capacity. We conclude that although the limits of hemodilution are still poorly defined, postoperative blood transfusion in revascularized patients should be guided by clinical indications and not by specific hematocrit values. There is evidence to suggest that anemia after severe traumatic brain injury (sTBI) is detrimental. However, there is a paucity of evidence supporting the use of transfusion of packed red blood cells in patients with sTBI. To understand the acute effect of packed red blood cell transfusion on cerebral oxygenation and metabolism in patients with sTBI.
                Prospective clinical study.
                Addenbrooke's Neurosciences Critical Care Unit, a 21-bed tertiary academic unit.
                Thirty patients with sTBI.
                Patients were randomized by computer random number generator to one of three transfusion thresholds: 8, 9, or 10 g/dL. When the patients' hemoglobin concentration fell below their assigned threshold, two units of packed red blood cells were transfused over 2 hours. A 1-hour period of stabilization was observed before final data collection.
                The primary outcome was change in brain tissue oxygen (Pbto2). Secondary outcomes included dependence of baseline hemoglobin concentration and baseline Pbto2 on the relationship of transfusion and Pbto2, and the effect of transfusion on lactate pyruvate ratio (LPR) and brain pH as markers of cerebral metabolic state. Fifty-seven percent of patients experienced an increase in Pbto2 during the course of the study, whereas in 43% of patients, Pbto2 either did not change or decreased. Multivariable generalized estimating equation analysis revealed change in hemoglobin concentration to significantly and positively associated with change in Pbto2 [0.10 kPa/(g/dL) 95% confidence interval 0.03-0.17, p = 0.003]. Improvement in Pbto2 was not associated with baseline hemoglobin concentration or low Pbto2 (<1 kPa). Fifty-six percent of patients experienced an increase in LPR. No significant relationship between change in LPR or transfusion on pHbt and change in hemoglobin could be demonstrated.
                Transfusion of packed red blood cells acutely results in improved brain tissue oxygen without appreciable effect on cerebral metabolism.
                ISRCTN89085577.
The existing evidence supports the use of restrictive transfusion triggers in most patients, including those with pre-existing cardiovascular disease. As there are no trials, the effects of restrictive transfusion triggers in high-risk groups, such as acute coronary syndrome, need to be tested in further large clinical trials. In countries with inadequate screening of donor blood, the data may constitute a stronger basis for avoiding transfusion with allogeneic red cells.