***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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    ***EXAMPLES*** 
    Input: Objective To evaluate the immediate effects of red blood cell transfusion on central venous oxygen saturation and lactate levels in septic shock patients with different transfusion triggers . Methods We included patients with a diagnosis of septic shock within the last 48 hours and hemoglobin levels below 9.0g/dL Patients were r and omized for immediate transfusion with hemoglobin concentrations maintained above 9.0g/dL ( Group Hb9 ) or to withhold transfusion unless hemoglobin felt bellow 7.0g/dL ( Group Hb7 ) . Hemoglobin , lactate , central venous oxygen saturation levels were determined before and one hour after each transfusion . Results We included 46 patients and 74 transfusions . Patients in Group Hb7 had a significant reduction in median lactate from 2.44 ( 2.00 - 3.22 ) mMol/L to 2.21 ( 1.80 - 2.79 ) mMol/L , p = 0.005 , which was not observed in Group Hb9 [ 1.90 ( 1.80 - 2.65 ) mMol/L to 2.00 ( 1.70 - 2.41 ) mMol/L , p = 0.23 ] . Central venous oxygen saturation levels increased in Group Hb7 [ 68.0 ( 64.0 - 72.0)% to 72.0 ( 69.0 - 75.0)% , p < 0.0001 ] but not in Group Hb9 [ 72.0 ( 69.0 - 74.0)% to 72.0 ( 71.0 - 73.0)% , p = 0.98 ] . Patients with elevated lactate or central venous oxygen saturation < 70 % at baseline had a significant increase in these variables , regardless of baseline hemoglobin levels . Patients with normal values did not show a decrease in either group . Conclusion Red blood cell transfusion increased central venous oxygen saturation and decreased lactate levels in patients with hypoperfusion regardless of their baseline hemoglobin levels . Transfusion did not appear to impair these variables in patients without hypoperfusion . Clinical Trials.gov Introduction The aim of this study was to evaluate the effects of red blood cell ( RBC ) transfusions on muscle tissue oxygenation , oxygen metabolism and microvascular reactivity in critically ill patients using near-infrared spectroscopy ( NIRS ) technology . Methods This prospect i ve , observational study included 44 consecutive patients hospitalized in the 31-bed , medical-surgical intensive care unit of a university hospital with anemia requiring red blood cell transfusion .  Thenar tissue oxygen saturation ( StO2 ) and muscle tissue hemoglobin index ( THI ) were measured using a tissue spectrometer ( InSpectra ™ Model 325 ; Hutchinson Technology Inc. , Hutchinson , MN , USA ) . A vaso-occlusive test was performed before and 1 hour after RBC transfusion by rapid inflation of a pneumatic cuff around the upper arm . The following variables were recorded : THI , the StO2 desaturation slope during the occlusion ( % /minute ) and the StO2 upslope of the reperfusion phase following the ischemic period ( % /second ) . Muscle oxygen consumption ( NIR VO2 ; arbitrary units ) was calculated as the product of the inverse StO2 desaturation slope and the mean THI over the first minute of arterial occlusion . Results Blood transfusion result ed in increases in hemoglobin ( from 7.1 ( 6.7 to 7.7 ) to 8.4 ( 7.1 to 9 ) g/dl ; P < 0.01 ) and in oxygen delivery ( from 306 ( 259 to 337 ) to 356 ( 332 to 422 ) ml/minute/m2 ; P < 0.001 ) . However , systemic VO2 was unchanged . RBC transfusion did not globally affect NIRS-derived variables , but there was considerable interindividual variation . Changes in the StO2 upslope of the reperfusion phase after transfusion were negatively correlated with baseline StO2 upslope of the reperfusion phase ( r2 = 0.42 ; P < 0.0001 ) . Changes in NIR VO2 after transfusion were also negatively correlated with baseline NIR VO2 ( r2 = 0.48 ; P = 0.0015 ) . There were no correlations between RBC storage time and changes in StO2 slope or NIR VO2 . Conclusions Muscle tissue oxygenation , oxygen consumption and microvascular reactivity are globally unaltered by RBC transfusion in critically ill patients . However , muscle oxygen consumption and microvascular reactivity can improve following transfusion in patients with alterations of these variables at baseline Background Red blood cell ( RBC ) transfusion is commonly used to increase oxygen transport in patients with sepsis . However it does not consistently increase oxygen uptake at either the whole-body level , as calculated by the Fick method , or within individual organs , as assessed by gastric intra-mucosal pH. Aim This study evaluates the hemodynamic and oxygen utilization effects of hemoglobin infusion on critically ill septic patients . Methods Fifteen septic patients undergoing mechanical ventilation whose hemoglobin was < 10 g% were eligible . Ten patients ( APACHE II : 25.5 ± 7.6 ) received an infusion of 1 unit of packed RBC over 1 h while se date d and paralyzed . The remaining five control patients ( APACHE II : 24.3 ± 6.0 ) received a 5 % albumin solution ( 500 ml ) over 1 h. Hemodynamic data , gastric tonometry and calorimetry were obtained prior to and immediately after RBC transfusion or 5 % albumin infusion . Results Transfusion of RBC was associated with an improvement in left ventricular systolic work index ( 38.6 ± 12.6 to 41.1 ± 13.0 g/min/m2 ; P = 0.04 ) . In the control group there was no significant change in the left ventricular systolic work index ( 37.2 ± 14.3 to 42.2 ± 18.9 g/min/m2 ) . An increase in pulmonary vascular resistance index ( 203 ± 58 to 238 ± 49 dyne/cm5/m2 ; P = 0.04 ) was also observed , while no change was produced by colloid infusion ( 237 ± 87.8 to 226.4 ± 57.8 dyne/cm5/m2 ) . Oxygen utilization did not increase either by Fick equation or by indirect calorimetry in either group . Gastric intramucosal pH increased only in the control group but did not reach statistical significance . Conclusion Hemoglobin increase does not improve either global or regional oxygen utilization in anemic septic patients . Furthermore , RBC transfusion may hamper right ventricular ejection by increasing the pulmonary vascular resistance index Background Although the optimum hemoglobin ( H ) concentration for patients with septic shock ( SS ) has not been specifically investigated , current guidelines suggest that H of 7 - 9 g/dL , compared with 10 - 12 g/dL , was not associated with increased mortality in critically ill adults . This contrasts with early goal -directed resuscitation protocol s that use a target hematocrit of 30 % in patients with low central venous oxygen saturation ( ScvO2 ) during the first 6 hours of resuscitation of SS . Methods Data elements were prospect ively collected on all patients with SS patients ( lactic acid ( LA ) > 4 mmol/L , or hypotension ) . Out of a total of 396 SS patients , 46 patients received red blood cell ( RBC ) transfusion for ScvO2 < 70 % ( RBC group ) . We then matched 71 SS patients  that did not receive RBC transfusion ( NRBC group ) on the following goals ( G ) : LA obtained within 6 hours ( G1 ) , antibiotics given within 3 hours ( G2 ) , 20 mL/kg fluid bolus followed by vasopressors ( VP ) if needed to keep mean arterial pressure > 65 mm Hg ( G3 ) , central venous pressure > 8 mm Hg within 6 hours ( G4 ) and ScvO2 > 70 % within 6 hours ( G5 ) . Results In the RBC group , after one unit of RBC transfusion , ScvO2 improved from average of 63 % ( ± 12 % ) to 68 % ( ± 10 % ) ( P = 0.02 ) . Sixteen patients required another unit of RBC , and this result ed in increase of ScvO2 to 78 % ( ± 11 % ) ( P < 0.01 ) . The RBC and NRBC groups were matched on sequential organ failure assessment ( SOFA ) scores and all five goals . There was no difference in mortality between the two groups : 41 % vs. 39.4 % ( OR : 0.8 , 95 % CI : 0.4 - 1.7 , P = 0.6 ) . Conclusions In our study , transfusion of RBC was not associated with decreased mortality in SS patients BACKGROUND AND OBJECTIVES Haemoglobin threshold for transfusion has been significantly decreased , but haemoglobin plasma concentration may not be sufficient to assess the need of red-blood-cell ( RBC ) transfusion .  Central venous oxygen saturation ( ScvO2 ) is a clue of metabolic matching between O2 transport and consumption , which could help to assess when transfusion is appropriate once anaemia has been diagnosed in ICU patients . MATERIAL S AND METHODS Adult patients admitted consecutively to a cardiothoracic and vascular ICU were included in a prospect i ve , observational and single-centre study over a 6-month period ( September 2014 to February 2015 ) , provided they were transfused with RBC .  Patients with active bleeding or in unstable condition were excluded . Haemoglobin and ScvO2 were collected through a central venous catheter before and after transfusion . In order to identify a ScvO2 threshold , analysis of ScvO2 changes after transfusion was performed . RESULTS Fifty-three patients received 100 RBC transfusions .  Haemoglobin at the time of transfusion was 7·2 g/dl [ 6·8 - 7·7 ] , while ScvO2 was 66·9 % [ 60 - 73 ] . A 5 % increase in ScvO2 after transfusion has the best specificity and positive predictive values , with a ScvO2 threshold of 65 % . After transfusion ( RBC units , 2 [ 1 - 2 ] ) , ScvO2 increased only in patients with ScvO2 ≤65 % , from 58 % [ 53 - 62 ] to 69 % [ 64 - 73 ] ( P < 0·001 ) . CONCLUSION In anaemic patients  , RBC transfusion induced a significant increase in ScvO2 , provided it was low before transfusion . A 65 % cut-off value of ScvO2 before transfusion showed good specificity and good positive predictive value for a 5 % increase after transfusion BACKGROUND Red blood cell transfusion is commonly used to augment systemic oxygen delivery to supranormal levels in patients with sepsis . However , clinical studies have not consistently demonstrated that this therapeutic maneuver is accompanied by an increase in oxygen utilization at either the whole-body level or within individual organs . STUDY OBJECTIVES To determine the effect of red blood cell transfusion on gastrointestinal and whole-body oxygen uptake . DESIGN Prospect i ve , controlled , interventional study . SETTING Multidisciplinary intensive care unit of a tertiary care teaching hospital . PATIENTS Twenty-three critically ill patients with sepsis undergoing mechanical ventilation .  MEASUREMENTS AND MAIN RESULTS Systemic oxygen uptake was measured by indirect calorimetry and calculated by the Fick method . Gastric intramucosal pH as measured by tonometry was used to assess changes in splanchnic oxygen availability . Measurements were made prior to transfusion of 3 U of packed red blood cells . These were then repeated immediately following transfusion , as well as 3 and 6 hours later . There was no increase in systemic oxygen uptake measured by indirect calorimetry in any of the patients studied for up to 6 hours posttransfusion ( including those patients with an elevated arterial lactate concentration ) . However , the calculated systemic oxygen uptake increased in parallel with the oxygen delivery in all the patients . More importantly , we found an inverse association between the change in gastric intramucosal pH and the age of the transfused blood ( r = -.71 ; P < .001 ) . In those patients receiving blood that had been stored for more than 15 days , the gastric intramucosal pH consistently decreased following the red blood cell transfusion . CONCLUSION We failed to demonstrate a beneficial effect of red blood cell transfusion on measured systemic oxygen uptake in patients with sepsis . Patients receiving old transfused red blood cells developed evidence of splanchnic ischemia . We postulate that the poorly deformable transfused red blood cells cause micro-circulatory occlusion in some organs , which may lead to tissue ischemia in some organs The role of isolated blood transfusion as a means toward improving oxygen transport was evaluated in 19 critically ill patients having sepsis syndrome as defined by st and ard criteria . 
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Conclusions : Transfusion was not associated with a decrease in mean cardiac output or mean heart rate .
The increase in mean oxygen delivery following transfusion was associated with an increase in mean oxygen consumption after transfusion , especially in patients with sepsis