title: Lactate level, aetiology and mortality of adult patients in an emergency department: a cohort study.
abstract: BACKGROUND
  Increased lactate is associated with high mortality among patients with suspected infection or trauma in the emergency department (ED), but the association with patients with other aetiologies is less well described. The aim of this study was to describe the relation between lactate, aetiology and 7-day mortality in adult ED patients.
  
  
  METHODS
  A retrospective cohort study of all adult patients who had a lactate measured within 4 h after arrival to the ED at Odense University Hospital between June 2012 and May 2013. The categorisation of suspected aetiology was based on discharge diagnoses.
  
  
  RESULTS
  5360 patients were included; 51.7% were men, and the median age was 67 years (IQR 50-79). 77.2% had low lactate (0-1.9 mmol/L), 16.2% intermediate lactate (2-3.9 mmol/L), and 6.6% high lactate (≥4 mmol/L). 7-day mortality was 2.9% (95% CI 2.4% to 3.5%) for patients with low lactate, 7.8% (95% CI 6.1% to 9.8%) for patients with intermediate lactate, and 23.9% (95% CI 19.6% to 28.8%) for patients with high lactate. The association between lactate level and mortality varied across different diagnostic groups. Based on Area Under the Curve in receiver operating characteristic analysis, lactate level showed to be useful in patients with infection (0.78, 95% CI 0.73 to 0.84), trauma (0.78, 95% CI 0.65 to 0.92), cardiac diseases (0.83, 95% CI 0.75 to 0.91) and gastrointestinal diseases (0.83, 95% CI 0.68 to 0.98). Lactate level was not useful in neurological (0.58, 95% CI 0.50 to 0.67) and respiratory disease (0.64, 95% CI 0.55 to 0.74), and of uncertain value in the remaining diagnostic groups.
  
  
  CONCLUSIONS
  Among adult ED patients, the prognostic value of lactate varies between diagnostic groups.
authors.affiliation: Department of Emergency Medicine, Odense University Hospital, Odense C, Denmark.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Pedersen
authors.affiliation: Department of Emergency Medicine, Odense University Hospital, Odense C, Denmark.
authors.forename: Vibeke Schnack
authors.initials: VS
authors.lastname: Brandt
authors.affiliation: Department of Emergency Medicine, Odense University Hospital, Odense C, Denmark.
authors.forename: Jon Gitz
authors.initials: JG
authors.lastname: Holler
authors.affiliation: Department of Emergency Medicine, Odense University Hospital, Odense C, Denmark.
authors.forename: Annmarie Touborg
authors.initials: AT
authors.lastname: Lassen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003953:Diagnosis-Related Groups; D004636:Emergency Service, Hospital; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D012372:ROC Curve; D012189:Retrospective Studies; D012307:Risk Factors; D016019:Survival Analysis; D055815:Young Adult
chemical_list: D019344:Lactic Acid
keywords: acute medicine-other; death/mortality; diagnosis; emergency department