***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Preoperative transfusions are frequently given to prevent perioperative morbidity in patients with sickle cell anemia . There is no consensus , however , on the best regimen of transfusions for this purpose . METHODS We conducted a multicenter study to compare the rates of perioperative complications among patients r and omly assigned to receive either an aggressive transfusion regimen design ed to decrease the hemoglobin S level to less than 30 percent ( group 1 ) or a conservative regimen design ed to increase the hemoglobin level to 10 g per deciliter ( group 2 ) . RESULTS Patients undergoing a total of 604 operations were r and omly assigned to group 1 or group 2 . The severity of the disease , compliance with the protocol , and the types of operations were similar in the two groups . The preoperative hemoglobin level was 11 g per deciliter in group 1 and 10.6 g per deciliter in group 2 . The preoperative value for hemoglobin S was 31 percent in group 1 and 59 percent in group 2 . The most frequent operations were cholecystectomies ( 232 ) , head and neck surgery ( 156 ) , and orthopedic surgery ( 72 ) . With the exception of transfusion-related complications , which occurred in 14 percent of the operations in group 1 and in 7 percent of those in group 2 , the frequency of serious complications was similar in the two groups ( 31 percent in group 1 and 35 percent in group 2 ) . The acute chest syndrome developed in 10 percent of both groups and result ed in two deaths in group 1 . A history of pulmonary disease and a higher risk associated with surgery were significant predictors of the acute chest syndrome . CONCLUSIONS A conservative transfusion regimen was as effective as an aggressive regimen in preventing perioperative complications in patients with sickle cell anemia , and the conservative approach result ed in only half as many transfusion-associated complications BACKGROUND 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 . PATIENTS AND METHODS A total of 120 elderly , cognitively intact hip fracture patients admitted from their own home were r and omly 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 ) . RESULTS 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 ) . CONCLUSION 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 r and omized studies BACKGROUND AND OBJECTIVES 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 . MATERIAL S AND METHODS We performed a multicentre , controlled trial in which 260 patients undergoing elective hip and knee replacement surgery were enrolled and r and omized 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 . RESULTS 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 . CONCLUSIONS 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 Objective : To determine the impact of a restrictive vs. a liberal transfusion strategy on  new or progressive multiple organ dysfunction syndrome in children post cardiac surgery . The optimal transfusion threshold after cardiac surgery in children is unknown . Design : R and omized , controlled trial . Setting : Tertiary pediatric intensive care units . Patients : Participants are a subgroup of pediatric patients post cardiac surgery from the TRIPICU ( Transfusion Requirements in Pediatric Intensive Care Units ) study . Exclusion criteria specific to the cardiac surgery subgroup included : age < 28 days and patients remaining cyanotic . Intervention : Critically ill children with a hemoglobin ≤95 g/L within 7 days of pediatric intensive care unit admission were r and omized to receive prestorage leukocyte-reduced red-cell transfusion if their hemoglobin dropped either < 70 g/L ( restrictive ) or 95 g/L ( liberal ) . Measurements and Main Results : Postoperative cardiac patients ( n = 125 ) from seven centers were enrolled . The restrictive ( n = 63 ) and liberal ( n = 62 ) groups were similar at baseline in age ( mean ± st and ard deviation = 31.4 ± 38.1 mos vs. 26.4 ± 39.1 mos ) , surgical procedure , severity of illness ( Pediatric Risk of Mortality score = 3.4 ± 3.2 vs. 3.2 ± 3.2 ) , multiple organ dysfunction syndrome ( 46 % vs. 44 % ) , mechanical ventilation ( 62 % vs. 60 % ) , and hemoglobin ( 83 vs. 80 g/L ) . Mean hemoglobin remained 21 g/L lower in the restrictive group after r and omization . No significant difference was found in new or progressive multiple organ dysfunction syndrome ( primary outcome ) in the restrictive group vs. liberal group ( 12.7 % vs. 6.5 % ; p = .36 ) , pediatric intensive care unit length of stay ( 7.0 ± 5.0 days vs. 7.4 ± 6.4 days ) or 28-day mortality ( 3.2 % vs. 3.2 % ) . Conclusion : In this subgroup analysis of cardiac surgery patients , a restrictive red-cell transfusion strategy , as compared with a liberal one , was not associated with any significant difference in new or progressive multiple organ dysfunction syndrome , but this evidence is not definitive OBJECTIVE In elective orthopaedic hip- and knee replacement surgery patients , we studied the effect of implementation of a uniform transfusion policy on RBC usage . STUDY DESIGN AND METHODS A r and omized , controlled study . A new uniform , restrictive transfusion policy was compared with st and ard 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 . RESULTS 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 st and ard care policy group ( mean difference 0.08;95 % CI [ -0.3 ; 0.2 ] ; P = 0.53 ) . In two hospitals , the new transfusion policy result ed 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 st and ard care policy in that hospital . Length of hospital stay was not influenced by either policy . CONCLUSIONS 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 Objective : To examine the impact of a restrictive vs. liberal transfusion strategy on arterial lactate and oxygen content differences in children with single-ventricle physiology post cavopulmonary connection . Children with single-ventricle physiology are routinely transfused postoperatively to increase systemic oxygen delivery , and transfusion thresholds in this population have not been studied . Design : Prospect i ve , r and omized , controlled , clinical trial . Setting : Pediatric cardiac intensive care unit in a teaching hospital . Patients : Infants and children ( n = 60 ) with variations of single-ventricle physiology presenting for cavopulmonary connection . Interventions : Subjects were r and omized to a restrictive ( hemoglobin of < 9.0 g/dL ) , or liberal ( hemoglobin of ≥13.0 g/dL ) transfusion strategy for 48 hrs post operation . Primary outcome measures were mean and peak arterial lactate . Secondary end points were arteriovenous ( C(a-v)o2 ) and arteriocerebral oxygen content ( C(a-c)o2 ) differences and clinical outcomes . Measurements and Main Results : A total of 30 children were in each group . There were no significant preoperative differences . Mean hemoglobin in the restrictive and liberal groups were 11 ± 1.3 g/dL and 13.9 ± 0.5 g/dL , respectively ( p < .01 ) . No differences in mean ( 1.4 ± 0.5 mmol/L [ Restrictive ] vs. 1.4 ± 0.4 mmol/L [ Liberal ] ) or peak ( 3.1 ± 1.5 mmol/L [ Restrictive ] vs. 3.2 ± 1.3 mmol/L [ Liberal ] ) lactate between groups were found . Mean number of red blood cell transfusions were 0.43 ± 0.6 and 2.1 ± 1.2 ( p < .01 ) , and donor exposure was 1.2 ± 0.7 
    Output:
    
Compared with liberal strategies , restrictive transfusion strategies were associated with a reduction in the number of red blood cell units transfused and number of patients being transfused , but mortality , overall morbidity , and myocardial infa rct ion seemed to be unaltered .
Restrictive transfusion strategies are safe in most clinical setting s. Liberal transfusion strategies have not been shown to convey any benefit to patients .