***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE : To determine the utility of pulse pressure variation ( ΔRESPPP ) in predicting fluid responsiveness in patients ventilated with low tidal volumes ( VT ) and to investigate whether a lower ΔRESPPP cut-off value should be used when patients are ventilated with low tidal volumes . METHOD : This cross-sectional observational study included 37 critically ill patients with acute circulatory failure who required fluid challenge . The patients were se date d and mechanically ventilated with a VT of 6 - 7 ml/kg ideal body weight , which was monitored with a pulmonary artery catheter and an arterial line . The  mechanical ventilation and hemodynamic parameters ,  including ΔRESPPP  , were measured before and after fluid challenge with 1,000 ml crystalloids or 500 ml colloids . Fluid responsiveness was defined as an increase in the cardiac index of at least 15 % . Clinical Trial.gov : NCT01569308 . RESULTS : A total of 17 patients were classified as responders . Analysis of the area under the ROC curve ( AUC ) showed that the optimal cut-off point for ΔRESPPP to predict fluid responsiveness was 10 % ( AUC = 0.74 ) . Adjustment of the ΔRESPPP to account for driving pressure did not improve the accuracy ( AUC = 0.76 ) . A ΔRESPPP≥10 % was a better predictor of fluid responsiveness than central venous pressure ( AUC = 0.57 ) or pulmonary wedge pressure ( AUC = 051 ) . Of the 37 patients , 25 were in septic shock . The AUC for ΔRESPPP≥10 % to predict responsiveness in patients with septic shock was 0.84 ( sensitivity , 78 % ; specificity , 93 % ) . CONCLUSION : The parameter ΔRESPPP has limited value in predicting fluid responsiveness in patients who are ventilated with low tidal volumes , but a ΔRESPPP>10 % is a significant improvement over static parameters . A ΔRESPPP≥10 % may be particularly useful for identifying responders in patients with septic shock OBJECTIVES Arterial pulse pressure variation ( PPV ) and digital plethysmographic variability index ( PVI ) have been proposed to predict fluid responsiveness during anesthesia and in critically ill patients . The present study aim ed to compare the clinical utility of PPV and PVI in predicting fluid responsiveness after elective cardiac surgery . DESIGN A prospect i ve observational study . SETTING A university hospital . PARTICIPANTS Eighty-seven adult patients . INTERVENTIONS Admission to the intensive care unit after cardiac surgery . Investigation before and after fluid challenge . MEASUREMENTS AND MAIN RESULTS The discrimination of both PPV and PVI in predicting fluid responsiveness was compared by using areas under the receiver operating characteristics curves ( ROCAUC ) . Sensibility analyses were conducted after exclusion of patients with a low perfusion index , patients receiving norepinephrine , and patients with right ventricular dysfunction . Fifty-seven ( 71 % ) patients were responders and twenty-three ( 29 % ) were nonresponders . ROCAUC were 0.73 [ 95 % CI : 0.63 - 0.83 ] versus 0.60 [ 95 % CI : 0.48 - 0.71 ] for PPV and PVI in the whole cohort of patients , respectively ( p = 0.020 ) . The inconclusive class of responses included 47 ( 59 % ) and 62 ( 77 % ) patients , respectively ( p = 0.010 ) ; whereas the discrimination of PVI remained low whatever the subgroup of patients , the discrimination of PPV markedly increased in patients without perfusion index ≤ 1.3 ( ROCAUC = 0.83 [ 95 % CI : 0.68 - 0.93 ] ) and in patients without right ventricular dysfunction ( ROCAUC = 0.85 [ 95 % CI : 0.67 - 0.95 ] ) . CONCLUSIONS PVI is not discriminant and probably inaccurate to predict fluid responsiveness after elective cardiac surgery . PPV could be of potential interest after exclusion of patients with a low perfusion index and right ventricular dysfunction Objectives : During circulatory failure , the ultimate goal of treatments that increase cardiac output is to reduce tissue hypoxia . This can only occur if oxygen consumption depends on oxygen delivery . We compared the ability of central venous oxygen saturation and markers of anaerobic metabolism to predict whether a fluid-induced increase in oxygen delivery results in an increase in oxygen consumption . Design : Prospect i ve study . Setting : ICU . Patients : Fifty-one patients with an acute circulatory failure ( 78 % of septic origin ) . Measurements : Before and after a volume expansion ( 500mL of saline ) , we measured cardiac index , o2- and Co2-derived variables and lactate . Main Results : Volume expansion increased cardiac index ≥15 % in 49 % of patients ( “ volume-responders ” ) . Oxygen delivery significantly increased in these 25 patients ( + 32 % ± 16 % , p < 0.0001 ) . An increase in oxygen consumption ≥15 % concomitantly occurred in 56 % of these 25 volume-responders ( + 38 % ± 28 % ) . Compared with the volume-responders in whom oxygen consumption did not increase , the volume-responders in whom oxygen consumption increased ≥15 % were characterized by a higher lactate ( 2.3 ± 1.1 mmol/L vs. 5.5 ± 4.0 mmol/L , respectively ) and a higher ratio of the veno-arterial carbon dioxide tension difference ( P(v − a)Co2 ) over the arteriovenous oxygen content difference ( C(a − v)o2 ) . A fluid-induced increase in oxygen consumption greater than or equal to 15 % was not predicted by baseline central venous oxygen saturation but by high baseline lactate and ( P(v − a)Co2/C(a − v)o2 ratio ( areas under the receiving operating characteristics curves : 0.68 ± 0.11 , 0.94 ± 0.05 , and 0.91 ± 0.06 ) . In volume-nonresponders , volume expansion did not significantly change cardiac index , but the oxygen delivery decreased due to a hemodilution-induced decrease in hematocrit . Conclusions : In volume-responders , unlike markers of anaerobic metabolism , central venous oxygen saturation did not allow the prediction of whether a fluid-induced increase in oxygen delivery would result in an increase in oxygen consumption . This suggests that along with indicators of volume-responsiveness , the indicators of anaerobic metabolism should be considered instead of central venous oxygen saturation for starting hemodynamic resuscitation Objective : To investigate whether stroke volume variations obtained with the pressure recording analytic method can predict fluid responsiveness in mechanically ventilated patients with circulatory failure . Design : Prospect i ve study . Setting : Surgical intensive care unit of a university hospital . Patients : Thirty-five mechanically ventilated patients with circulatory failure for whom the decision to give fluid was taken by the physician were included . Exclusion criteria were : Arrhythmia , tidal volume < 8 mL/kg , left ventricular ejection fraction<50 % , right ventricular dysfunction , and heart rate/respiratory rate ratio < 3.6 . Interventions : Fluid challenge with 500 mL of saline over 15 mins . Measurements and Main Results : Stroke volume variations and cardiac output obtained with a pressure recording analytic method , pulse pressure variations , and cardiac output estimated by echocardiography were recorded before and after volume expansion . Patients were defined as responders if stroke volume obtained using echocardiography increased by ≥15 % after volume expansion . Nineteen patients responded to the fluid challenge . Median [ interquartile range , 25 % to 75 % ] stroke volume variation values at baseline were not different in responders and nonresponders ( 10 % [ 8–16 ] vs. 14 % [ 12–16 ] ) , whereas pulse pressure variations were significantly higher in responders ( 17 % [ 13–19 ] vs. 7 % [ 5–10 ] ; p < .0001 ) . A 12.6 % stroke volume variations threshold discriminated between responders and nonresponders with a sensitivity of 63 % ( 95 % confidence interval 38 % to 84 % ) and a specificity of 69 % ( 95 % confidence interval 41 % to 89 % ) . A 10 % pulse pressure variation threshold discriminated between responders and nonresponders with a sensitivity of 89 % ( 95 % confidence interval 67 % to 99 % ) and a specificity of 88 % ( 95 % confidence interval 62 % to 98 % ) . The area under the receiver operating characteristic curves was different between pulse pressure variations ( 0.95 ; 95 % confidence interval 0.82–0.99 ) and stroke volume variations ( 0.60 ; 95 % confidence interval 0.43–0.76 ) ; p < .0001 ) . Volume expansion-induced changes in cardiac output measured using echocardiography or pressure recording analytic method were not correlated ( r2 = 0.14 ; p > .05 ) and the concordance rate of the direction of change in cardiac output was 60 % . Conclusion : Stroke volume variations obtained with a pressure recording analytic method can not predict fluid responsiveness in intensive care unit patients under mechanical ventilation . Cardiac output measured by this device is not able to track changes in cardiac output induced by volume expansion . ( Crit Care Med 2012 ; 40:–1191 BACKGROUND The safety and efficacy of hydroxyethyl starch ( HES ) for fluid resuscitation have not been fully evaluated , and adverse effects of HES on survival and renal function have been reported . METHODS We r and omly assigned 7000 patients who had been admitted to an intensive care unit ( ICU ) in a 1:1 ratio to receive either 6 % HES with a molecular weight of 130 kD and a molar substitution ratio of 0.4 ( 130/0.4 , Voluven ) in 0.9 % sodium chloride or 0.9 % sodium chloride ( saline ) for all fluid resuscitation until ICU discharge , death , or 90 days after r and omization . The primary outcome was death within 90 days . Secondary outcomes included acute kidney injury and failure and treatment with renal-replacement therapy . RESULTS A total of 597 of 3315 patients ( 18.0 % ) in the HES group and 566 of 3336 ( 17.0 % ) in the saline group died ( relative risk in the HES group , 1.06 ; 95 % confidence interval [ CI ] , 0.96 to 1.18 ; P=0.26 ) . There was no significant difference in mortality in six predefined subgroups . Renal-replacement therapy was used in 235 of 3352 patients ( 7.0 % ) in the HES group and 196 of 3375 ( 5.8 % ) in the saline group ( relative risk , 1.21 ; 95 % CI , 1.00 to 1.45 ; P=0.04 ) . In the HES and saline groups , renal injury occurred in 34.6 % and 38.0 % of patients , respectively ( P=0.005 ) , and renal failure occurred in 10.4 % and 9.2 % of patients , respectively ( P=0.12 ) . HES was associated with significantly more adverse events ( 5.3 % vs. 2.8 % , P<0.001 ) . CONCLUSIONS In patients in the ICU , there was no significant difference in 90-day mortality between patients resuscitated with 6 % HES ( 130/0.4 ) or saline . However , more patients who received resuscitation with HES were treated with renal-replacement therapy . ( Funded by the National Health and Medical Research Council of Australia and others ; CHEST Clinical Trials.gov number , NCT00935168 . ) PURPOSE Volume expansion is a common therapeutic intervention in septic shock , although patient response to the intervention is difficult to predict . Central venous pressure ( CVP ) and shock index have been used independently to guide volume expansion , although their use is question able . We hypothesize that a combination of these measurements will be useful . METHODS In a prospect i ve , observational study , patients with early septic shock received 10-mL/kg volume expansion at their treating physician 's discretion after brief initial resuscitation in the emergency department . Central venous pressure and shock index were measured before volume expansion interventions .  Cardiac index  was measured immediately before and after the volume expansion using transthoracic echocardiography .  Hemodynamic response was defined as an increase in a cardiac index of 15 % or greater . RESULTS Thirty-four volume expansions were observed in 25 patients . A CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1 ) mm Hg(-1 ) or less individually had a good negative predictive value ( 83 % and 88 % , respectively ) . Of 34 volume expansions , the combination of both a high CVP and a low shock index was extremely unlikely to elicit hemodynamic response ( negative predictive value , 93 % ; P = .02 ) . CONCLUSIONS Volume expansion in patients with early septic shock with a CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1 ) mm Hg(-1 ) or less is unlikely to lead to an increase in cardiac index In this prospect i ve study , cardiac output was 
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Conclusions The PR decreases with a long infusion time .