***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: Background : Lactate has been shown to be a prognostic biomarker in trauma . Although lactate clearance has already been proposed as an intermediate endpoint in r and omized trials , its precise role in trauma patients remains to be determined . Methods :  Blood lactate levels and lactate clearance ( LC ) were calculated at admission and 2 and 4 h later in trauma patients . The association of initial blood lactate level and lactate clearance with mortality was tested using receiver-operating characteristics curve , logistic regression using triage scores , Trauma Related Injury Severity Score as a reference st and ard , and reclassification method . Results : The authors evaluated 586 trauma patients ( mean age 38 ± 16 yr , 84 % blunt and 16 % penetrating , mortality 13 % ) . Blood lactate levels at admission were elevated in 327 ( 56 % ) patients . The lactate clearance should be calculated within the first 2 h after admission as LC0–2 h was correlated with LC0–4 h ( R2 = 0.55 , P < 0.001 ) but not with LC2–4 h ( R2 = 0.04 , not significant ) . The lactate clearance provides additional predictive information to initial blood lactate levels and triage scores and the reference score . This additional information may be summarized using a categorical approach ( i.e. , less than or equal to −20 % /h ) in contrast to initial blood lactate . The results were comparable in patients with high ( 5 mM/l or more ) initial blood lactate . Conclusions : Early ( 0–2 h ) lactate clearance is an important and independent prognostic variable that should probably be incorporated in future decision schemes for the resuscitation of trauma patients Objective . To evaluate 2-hour lactate clearance as a prognostic marker in acute cardiorespiratory insufficiency . Design . Prospect i ve observational study . Setting . Emergency Department ( ED ) and 16-bed medical High Dependency Unit ( HDU ) . Methods and Main Results . 95 consecutive admissions from the ED for acute cardiorespiratory insufficiency were prospect ively enrolled .  Arterial lactate concentration  was assessed at ED arrival and 1 , 2 , 6 , and 24 hours later . The predictive value of 2-hour lactate clearance was evaluated for negative outcomes defined as hospital mortality or need for endotracheal intubation versus positive outcomes defined as discharge or transfer to a general medical ward . Logistic regression and ROC curves found 2-hour lactate clearance > 15 % was a strong predictor of negative outcome ( P < .0001 ) with a sensitivity of 86 % ( 95%CI = 67%–95 % ) and a specificity of 91 % ( 95%CI = 82%–96 % ) , Positive predictive value was 80 % ( 95%CI = 61%–92 % ) , and negative predictive value was 92 % ( 95%CI = 84%–98 % ) . Conclusions . Systematic monitoring of lactate clearance at 2 hours can be used in to identify patients at high risk of negative outcome and perhaps to tailor more aggressive therapy . Equally important is that a 2-hour lactate clearance > 15 % is highly predictive of positive outcome and may reassure clinicians that the therapeutic approach is appropriate Abstract Background Blood lactate levels and central venous oxygen saturation ( ScvO2 ) are known to be useful indicators of global tissue hypoxia . However , it is unclear whether ScvO2 correlates with lactate levels when measured simultaneously and whether changes in ScvO2 or lactate levels in serial measurements have prognostic value . We investigated the correlation between ScvO2 and lactate levels measured simultaneously and their association with clinical outcomes . Methods We performed a prospect i ve observational study of patients with severe systemic inflammatory response syndrome ( SIRS ) and severe sepsis who were admitted to the medical intensive care unit .  ScvO2 and lactate levels  were measured simultaneously at the time of study enrollment , every 6 h for 24 h , and then every 24 h until the goal was reached . Results Twenty-five patients were enrolled in the study ; 13 have died and 12 have survived . There was no correlation between lactate levels and ScvO2 . Neither lactate levels nor ScvO2 at the time of admission differed between nonsurvivors and survivors . Normalization of lactate levels within 48 h was significantly associated with survival . Conclusions In patients with severe SIRS and severe sepsis , simultaneously measured ScvO2 and lactate levels showed no correlation , and normalization of lactate levels within 48 h was a predictive factor for survival OBJECTIVE To compare the efficacy of fluid resuscitation as guided by lactate clearance rate ( LCR ) and central venous oxygen saturation ( ScvO2 ) in patients with sepsis . METHODS A prospect i ve r and omized control study was conducted . Fifty patients diagnosed with severe sepsis or septic shock from January 2011 to February 2012 in department of critical care medicine of Fourth Hospital of Hebei Medical University were enrolled in the study . The patients were r and omly divided into two groups according to the sequence ( each n=25 ) : ScvO2 group and LCR group . After ICU admission , the patients were treated symptomatically timely , and fluid resuscitation was started as early as possible according to Surviving Sepsis Campaign guidance for management of severe sepsis and septic shock 2008 . Central venous pressure (CVP)≥8 mm Hg ( 1 mm Hg=0.133 kPa ) , mean arterial pressure (MAP)≥65 mm Hg and ScvO2≥0.70 served as goal values to accomplish the fluid resuscitation therapy in ScvO2 group , while CVP≥8 mm Hg , MAP≥65 mm Hg , LCR≥10 % served as goal value to accomplish the fluid resuscitation therapy in LCR group . The general condition and clinical characteristics on arrival in ICU , changes in CVP , MAP , ScvO2 , lactate level and /or LCR before ( 0 hour ) and 3 , 6 , 72 hours after the start of fluid resuscitation and the other related conditions during the therapy were recorded . RESULTS There was no significant difference in general data or clinical characteristics before the start of therapy , occurrence of organ dysfunction , or treatment measures during different time periods after start of fluid resuscitation . Compared with the condition immediately before fluid resuscitation , at 3 hours after start of fluid resuscitation , CVP were improved in LCR and ScvO2 groups ( 8.58±1.17 mm Hg vs. 6.33±1.21 mm Hg , 9.08±2.43 mm Hg vs. 5.33±0.98 mm Hg , both P<0.05 ) ; at 6 hours after start of fluid resuscitation , heart rate ( HR ) and respiratory rate ( RR ) were lowered in LCR and ScvO2 groups ( HR : 96±18 bpm vs. 127±13 bpm , 98±13 bpm vs. 116±19 bpm , RR : 23±3 times/min vs. 33±9 times/min , 24±5 times/min vs. 35±6 times/min , all P<0.05 ) , oxygenation index ( PaO2/FiO2 ) was increased in LCR and ScvO2 groups ( 179±41 mm Hg vs. 86±21 mm Hg , 202±33 mm Hg vs. 95±17 mm Hg , both P<0.05 ) , and there was no significant difference in MAP in both groups . There was no significant difference in all indexes between two groups . In LCR group , 3 hours after start of fluid resuscitation , lactate level was significantly decreased ( 2.81±0.18 mmol/L vs. 3.43±1.31 mmol/L , P<0.05 ) . Compared with the value 3 hours after start of fluid resuscitation , LCR was significantly improved at 6 hours and 72 hours after start of fluid resuscitation in LCR group [ (42.69±8.75)% , (48.87±9.69)% vs. (20.32±4.58)% , both P<0.05 ] . Compared with that immediately before fluid resuscitation , ScvO2 was significant improved in ScvO2 group at 3 hours after start of fluid resuscitation ( 0.65±0.04 vs. 0.53±0.06 , P<0.05 ) . There was no significant difference in success rate of fluid resuscitation comparing that of 6 hours and that of 72 hours [ 6 hours : 72 % ( 18/25 ) vs. 64 % ( 16/25 ) , χ(2)=0.368 , P=0.762 ; 72 hours : 88 % ( 22/25 ) vs. 88 % ( 22/25 ) , χ(2)=0.000 , P=1.000 ] , length of ICU stay ( 8±3 days vs. 10±4 days , t=0.533 , P=0.874 ) , length of hospital stay ( 29±11 days vs. 35±16 days , t=0.692 , P=0.531 ) , improvement rate [ 84 % ( 21/25 ) vs. 76%(19/25 ) , χ(2)=0.500 , P=0.480 ] or 28-day mortality [ 20 % ( 5/25 ) vs. 28 % ( 7/25 ) , χ(2)=0.439 , P=0.742 ] between LCR and ScvO2 groups . CONCLUSIONS Both LCR and ScvO2 can be taken as the index in confirming the endpoint of fluid resuscitation for patients with severe sepsis and septic shock . Fluid resuscitation therapy under the guidance of LCR is accurate and reliable in patients with severe sepsis and septic shock Introduction Dynamic changes in lactate concentrations in the critically ill may predict patient outcome more accurately than static indices . We aim ed to compare the predictive value of dynamic indices of lactatemia in the first 24 hours of intensive care unit ( ICU ) admission with the value of more commonly used static indices . Methods This was a retrospective observational study of a prospect ively obtained intensive care data base of 5,041 consecutive critically ill patients from four Australian university hospitals . We assessed the relationship between  dynamic lactate values  collected in the first 24 hours of ICU admission and both ICU and hospital mortality . Results We obtained 36,673  lactate  measurements in 5,041 patients in the first 24 hours of ICU admission . Both the time weighted average lactate ( LACTW24 ) and the change in lactate ( LACΔ24 ) over the first 24 hours were independently predictive of hospital mortality with both relationships appearing to be linear in nature . For every one unit increase in LACTW24 and LACΔ24 the risk of hospital death increased by 37 % ( OR 1.37 , 1.29 to 1.45 ; P < 0.0001 ) and by 15 % ( OR 1.15 , 1.10 to 1.20 ; P < 0.0001 ) respectively . Such dynamic indices , when combined with Acute Physiology and Chronic Health Evaluation II ( APACHE II ) scores , improved overall outcome prediction ( P < 0.0001 ) achieving almost 90 % accuracy . When all lactate measures in the first 24 hours were considered , the combination of LACTW24 and LACΔ24 significantly outperformed ( P < 0.0001 ) static indices of lactate concentration , such as admission lactate , maximum lactate and minimum lactate . Conclusions In the first 24 hours following ICU admission , dynamic indices of hyperlactatemia have significant independent predictive value , improve the performance of illness severity score-based outcome predictions and are superior to simple static indices of lactate concentration Background The decision of when to stop  septic shock resuscitation  is a critical but yet a relatively unexplored aspect of care . This is especially relevant since the risks of over-resuscitation with fluid overload or inotropes have been highlighted in recent years . A recent guideline has proposed normalization of central venous oxygen saturation and /or lactate as therapeutic end-points , assuming that these variables are equivalent or interchangeable . However , since the physiological determinants of both are totally different , it is legitimate to challenge the rationale of this proposal . We design ed this study to gain more insights into the most appropriate resuscitation goal from a dynamic point of view . Our objective was to compare the normalization rates of these and other potential perfusion-related targets in a cohort of septic shock survivors . Methods We design ed a prospect i ve , observational clinical study . One hundred and four septic shock patients with hyperlactatemia were included and followed until hospital discharge . The 84 hospital-survivors were kept for final analysis . A multimodal perfusion assessment was performed at baseline , 2 , 6 , and 24 h of ICU treatment . Results Some variables such as central venous oxygen saturation , central venous-arterial pCO2 gradient , and capillary refill time were already normal in more than 70 % of survivors at 6 h. Lactate presented a much slower normalization rate decreasing significantly at 6 h compared to that of baseline ( 4.0 [ 3.0 to 4.9 ] vs. 2.7 [ 2.2 to 3.9 ] mmol/L ; p < 0.01 ) but with only 52 % of 
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A decrease in lactate levels over time was consistently associated with lower mortality rates in all subgroups of patients .
Lactate kinetics did not appear very different in patients with sepsis and other types of patients .
A few studies suggested that therapy could be guided by these measurements .
Conclusions The observation of a better outcome associated with decreasing blood lactate concentrations was consistent throughout the clinical studies , and was not limited to septic patients .
In all groups , the changes are relatively slow , so that lactate measurements every 1–2 hrs are probably sufficient in most acute conditions .
The value of lactate kinetics appears to be valid regardless of the initial value