***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: Objectives To determine the degree of interinstitutional transfusion practice variation and reasons why red cells are administered in critically ill patients . Study design Multicentre cohort study combined with a cross-sectional survey of physicians requesting red cell transfusions for patients in the cohort . Study population The cohort included 5298 consecutive patients admitted to six tertiary level intensive care units in addition to administering a survey to 223 physicians requesting red cell transfusions in these units . Measurements Haemoglobin concentrations were collected , along with the number and reasons for  red cell transfusions plus demographic , diagnostic , disease severity ( APACHE II score ) , intensive care unit ( ICU ) mortality and lengths of stay in the ICU . Results Twenty five per cent of the critically ill patients in the cohort study received red cell transfusions . The overall number of transfusions per patient-day in the ICU averaged 0.95 ± 1.39 and ranged from 0.82 ± 1.69 to 1.08 ± 1.27 between institutions ( P < 0.001 ) . Independent predictors of transfusion thresholds ( pre-transfusion haemoglobin concentrations ) included patient age , admission APACHE II score and the institution ( P < 0.0001 ) . A very significant institution effect ( P < 0.0001 ) persisted even after multivariate adjustments for age , APACHE II score and within four diagnostic categories ( cardiovascular disease , respiratory failure , major surgery and trauma ) ( P < 0.0001 ) . The evaluation of transfusion practice using the bedside survey documented that 35 % ( 202 of 576 ) of pre-transfusion haemoglobin concentrations were in the range of 95 - 105 g/l and 80 % of the orders were for two packed cell units . The most frequent reasons for administering red cells were acute bleeding ( 35 % ) and the augmentation of O2 delivery ( 25 % ) . Conclusions There is significant institutional variation in critical care transfusion practice , many intensivists adhering to a 100g/l threshold , and opting to administer multiple units despite published guidelines to the contrary . There is a need for prospect i ve studies to define optimal practice in the critically ill OBJECTIVES We sought to determine the relationship between red blood cell ( RBC ) transfusion and clinical outcomes in patients undergoing primary percutaneous coronary intervention ( PCI ) for acute myocardial infa rct ion ( AMI ) . BACKGROUND The implication s of RBC transfusion in patients undergoing primary PCI for AMI have not been evaluated . METHODS Clinical outcomes of patients from the prospect i ve , r and omized CADILLAC ( Controlled Abciximab and Device Investigation to Lower Late Angioplasty Complications ) trial were analyzed by administration of in-hospital RBC transfusion not related to coronary artery bypass surgery . RESULTS Of 2,060 r and omized patients , 82 ( 3.98 % ) received RBC transfusion during the index hospitalization , including 33 ( 1.60 % ) with moderate/severe bleeding and 49 ( 2.38 % ) without overt major bleeding . Transfusion was independently associated with baseline anemia ( odds ratio [ 95 % confidence interval ] : 4.44 [ 2.60 to 7.58 ] , p < 0.0001 ) , older age ( 1.03 [ 1.01 to 1.06 ] , p = 0.002 ) , triple-vessel disease ( 2.54 [ 1.47 to 4.38 ] , p = 0.0008 ) , and female sex ( 1.04 [ 1.02 to 1.06 ] , p = 0.0008 ) . Patients transfused versus not transfused had significantly higher rates of 1-year mortality ( 23.9 % vs. 3.4 % ) , disabling stroke ( 2.5 % vs. 0.5 % ) , reinfa rct ion ( 7.0 % vs. 2.2 % ) , and composite major adverse cardiac events ( 41.0 % vs. 16.6 % ) ( all p values < 0.01 ) . After multivariable adjustment for potential confounders including transfusion propensity , RBC transfusion was independently associated with mortality at 30 days ( hazards ratio : 4.71 , p = 0.0005 ) and 1 year ( hazards ratio : 3.16 , p = 0.0005 ) . CONCLUSIONS An RBC transfusion after primary PCI in AMI may be harmful , which is consistent with the findings from other studies after PCI in the noninfa rct setting . Alternatively , RBC transfusion may be a marker of markedly increased risk . R and omized studies are warranted to determine the optimal threshold for RBC transfusion in patients with AMI undergoing mechanical reperfusion therapy Background : The long‐term prognostic implication of post‐procedural hematocrit drops in patients undergoing cardiac catheterization outside the clinical trial setting is not well defined . Methods : Data was prospect ively collected from 12,661 patients undergoing diagnostic or interventional cardiac catheterization between July 1998 and July 2006 . Patients were divided into three cohorts based upon the degree of hematocrit change : drop greater than 6 , drop between 3 and 6 , and drop less than 3 . In‐hospital major adverse events , 30‐day mortality , and long‐term all‐cause mortality were recorded . Results : Patients with larger reductions in hematocrit were more likely to be older , female , and have a higher baseline hematocrit , present with acute myocardial infa rct ion , develop cardiogenic shock , require emergent catheterization , develop retroperitoneal bleeds and large hematomas , receive transfusions , have longer index hospitalizations , develop subacute stent thrombosis , and have higher 30‐day and long‐term mortality . An increase in long‐term mortality was observed with progressive hematocrit drop . This finding is largely driven by early ( 30 day ) mortality , as trends were no longer significant after rezeroing mortality . Hematocrit drop was not an independent risk factor for 30‐day mortality . Transfusion and low baseline hematocrit were identified as independent predictors of near and long‐term mortality . Conclusions : Periprocedural bleeding , defined by hematocrit drop , is associated with increased near‐term and long‐term mortality in patients undergoing diagnostic and therapeutic cardiac catheterization procedures . Long‐term mortality is largely driven by up front 30‐day mortality . Hematocrit drop was not an independent predictor for near‐term mortality . Transfusion and low baseline hematocrit were independent predictors for near and long‐term mortality . © 2009 Wiley‐Liss , The relation across anemia , hemorrhagic complications , and mortality associated with  percutaneous coronary intervention ( PCI )  is unclear . We review ed the R and omized Evaluation in PCI Linking Angiomax to Reduced Clinical Events (REPLACE)-2 Trial , which compared bivalirudin plus provisional glycoprotein IIb/IIIa blockade with heparin plus planned glycoprotein IIb/IIIa blockade in patients undergoing urgent or elective PCI . Of the 6,010 patients r and omized in REPLACE-2 , 1,371 ( 23 % ) were anemic .  Major bleeding was more common in anemic than in nonanemic patients ( 4.9 % vs 2.8 % , p = 0.0001 ) . In anemic patients , treatment with bivalirudin ( n = 678 ) result ed in a lower risk of major bleeding versus heparin plus glycoprotein IIb/IIIa blockade ( n = 693 , 3.5 % vs 6.2 % , p = 0.0221 ) . Mortality was higher in anemic patients than in nonanemic patients at 30 days ( 0.9 % vs 0.2 % , p < 0.0001 ) , 6 months ( 2.6 % vs 0.7 % , p < 0.0001 ) , and 1 year ( 4.3 % vs 1.5 % , p < 0.0001 ) . There were no differences between anemic and nonanemic patients with regard to ischemic complications at 30 days . Although anemic patients had higher mortality rates , proportions of cardiovascular and noncardiovascular mortalities were equal in anemic and nonanemic patients . In conclusion , anemic patients undergoing PCI have an increased risk of mortality and major bleeding , but not of ischemic events , and the use of bivalirudin with provisional glycoprotein IIb/IIIa blockade decreases the risk of hemorrhagic complications compared with heparin plus planned glycoprotein IIb/IIIa blockade Background : Bleeding and transfusion after  percutaneous coronary intervention ( PCI )  are known predictors of mortality . Transradial arterial access reduces bleeding and transfusion related to femoral access complications , although its association with mortality is unknown . Objective : To determine the association of arterial access site ( radial or femoral ) with transfusion and mortality in unselected PCIs . Design , setting and patients : By data linkage of three prospect ively collated provincial registries , 38 872 procedures in 32 822 patients in British Columbia were analysed . The association between access site , transfusion and outcomes was assessed by logistic regression , propensity score matching and probit regression . Main outcome measures : 30-Day and 1-year mortality . Results : 1134 ( 3.5 % ) patients had at least one blood transfusion .  Transfused patients had a significantly increased 30-day and 1-year mortality , adjusted odds ratio ( 95 % CI ) 4.01 ( 3.08 to 5.22 ) and 3.58 ( 2.94 to 4.36 ) , respectively . By probit regression the absolute increase in risk of death at 1 year associated with receiving a transfusion was 6.78 % . The number needed to treat was 14.74 ( prevention of 15 transfusions required to “ avoid ” one death ) . Radial access halved the transfusion rate . After adjustment for all variables , radial access was associated with a significant reduction in 30-day and 1-year mortality , odds ratio = 0.71 ( 95 % CI 0.61 to 0.82 ) and 0.83 ( 0.71 to 0.98 ) , respectively ( all p<0.001 ) . Conclusions : In a registry of all comers to PCI , transradial access was associated with a halving of the transfusion rate and a reduction in 30-day and 1-year mortality BACKGROUND Prior trials suggest it is safe to defer transfusion at hemoglobin levels above 7 to 8 g/dL in most patients . Patients with acute coronary syndrome may benefit from higher hemoglobin levels . METHODS We performed a pilot trial in 110 patients with acute coronary syndrome or stable angina undergoing cardiac catheterization and a hemoglobin < 10 g/dL. Patients in the liberal transfusion strategy received one or more units of blood to raise the hemoglobin level ≥10 g/dL. Patients in the restrictive transfusion strategy were permitted to receive blood for symptoms from anemia or for a hemoglobin < 8 g/dL. The predefined primary outcome was the composite of death , myocardial infa rct ion , or unscheduled revascularization 30 days post r and omization . RESULTS Baseline characteristics were similar between groups except age ( liberal , 67.3 ; restrictive , 74.3 ) . The mean number of units transfused was 1.6 in the liberal group and 0.6 in the restrictive group . The primary outcome occurred in 6 patients ( 10.9 % ) in the liberal group and 14 ( 25.5 % ) in the restrictive group ( risk difference = 15.0 % ; 95 % confidence interval of difference 0.7 % to 29.3 % ; P = .054 and adjusted for age P = .076 ) . Death at 30 days was less frequent in liberal group ( n = 1 , 1.8 % ) compared to restrictive group ( n = 7 , 13.0 % ; P = .032 ) . CONCLUSIONS The liberal transfusion strategy was associated with a trend for fewer major cardiac events and deaths than a more restrictive strategy . These results support the feasibility of and the need for a definitive trial IMPORTANCE Studies have shown variation in the use of red blood cell transfusion among patients with acute coronary syndromes . There are no definitive data for the efficacy of transfusion in improving outcomes , and concerning data exist about possible association with harm . Current transfusion practice s in patients undergoing percutaneous coronary intervention ( PCI ) are not well understood . OBJECTIVE To determine the current patterns of blood transfusion among patients undergoing PCI and the association of transfusion with adverse cardiac outcomes across hospitals in the United States . DESIGN , SETTING , AND PARTICIPANTS Retrospective cohort study of all patient visits from the CathPCI Registry from July 2009 to March 2013 that included PCI , excluding those with missing data on bleeding complications or who underwent in-hospital coronary artery bypass graft surgery ( N = 2,258,711 visits ) . MAIN OUTCOMES AND MEASURES Trans 
    Output:
    
Blood transfusion is independently associated with increased risk of mortality and MACE events .