title: Arterial lactate levels in an emergency department are associated with mortality: a prospective observational cohort study.
abstract: OBJECTIVE
  Lactate measurements are routinely carried out in emergency departments and are associated with increased mortality in septic patients. However, no definitive research has been carried out into whether lactate measurements can be used as a prognostic marker in a clinically unwell population in the emergency department.
  
  
  METHODS
  We carried out a prospective observational cohort study in consecutive patients whose arterial lactate concentration was measured in the emergency department of a tertiary referral hospital assessing 110,000 patients per year between 11th May and 11th August 2011. The main outcome measure was 30-day mortality.
  
  
  RESULTS
  There were 120 deaths (16.1%) at 30 days postattendance in our cohort of 747 patients. Multivariate logistic regression revealed lower lactate levels were associated with 30-day survival: ORs for 30-day death compared with lactate ≥4 were 0.125 (95% CI 0.068 to 0.229) for lactate <2 and 0.273 (95% CI 0.140 to 0.533) for lactate 2-<4. Kaplan-Meier analysis showed a survival difference when dividing lactate concentrations into strata (p<0.0001). This survival difference was maintained when septic diagnoses were taken into account.
  
  
  CONCLUSIONS
  A single arterial lactate measurement on presentation to the emergency department predicts 30-day mortality independent of other measures of illness severity.
authors.affiliation: Emergency Medicine Research Group Edinburgh (EMeRGE), Department of Emergency Medicine, Royal Infirmary of Edinburgh (NHS Lothian), Little France Crescent, Edinburgh, UK.
authors.forename: Deepankar
authors.identifier: http://orcid.org/0000-0001-9971-9434
authors.initials: D
authors.lastname: Datta
authors.affiliation: Emergency Medicine Research Group Edinburgh (EMeRGE), Department of Emergency Medicine, Royal Infirmary of Edinburgh (NHS Lothian), Little France Crescent, Edinburgh, UK Critical Care Department, St John's Hospital (NHS Lothian), Livingston, UK.
authors.forename: Craig
authors.initials: C
authors.lastname: Walker
authors.affiliation: Emergency Medicine Research Group Edinburgh (EMeRGE), Department of Emergency Medicine, Royal Infirmary of Edinburgh (NHS Lothian), Little France Crescent, Edinburgh, UK.
authors.forename: Alasdair James
authors.initials: AJ
authors.lastname: Gray
authors.affiliation: Wellcome Trust Clinical Research Facility, Western General Hospital, University of Edinburgh, Edinburgh, UK.
authors.forename: Catriona
authors.initials: C
authors.lastname: Graham
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D004636:Emergency Service, Hospital; D005260:Female; D006323:Heart Arrest / Q000097:blood* / Q000401:mortality; D006801:Humans; D053208:Kaplan-Meier Estimate; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D012772:Shock, Septic / Q000097:blood* / Q000401:mortality
chemical_list: D019344:Lactic Acid
keywords: assessment; clinical care; death/mortality; emergency department management; research, epidemiology