title: Mortality and the nature of metabolic acidosis in children with shock.
abstract: OBJECTIVE
  Mortality in children with shock is more closely related to the nature, rather than the magnitude (base deficit/excess), of a metabolic acidosis.
  
  
  OBJECTIVE
  To examine the relationship between base excess (BE), hyperlactataemia, hyperchloraemia, 'unmeasured' strong anions, and mortality.
  
  
  METHODS
  Prospective observational study set in a multi-disciplinary Paediatric Intensive Care Unit (PICU).
  
  
  METHODS
  Forty-six children, median age 6 months (1.5-14.4), median weight 5 kg (3.2-8.8), admitted to PICU with shock.
  
  
  METHODS
  Predicted mortality was calculated from the paediatric index of mortality (PIM) score. The pH, base excess, serum lactate, corrected chloride, and 'unmeasured' strong anions (Strong Ion Gap) were measured or calculated at admission and 24 h.
  
  
  RESULTS
  Observed mortality ( n=16) was 35%, with a standardised mortality ratio (SMR) of 1.03 (95% CI 0.71-1.35). There was no significant difference in admission pH or BE between survivors and nonsurvivors. There was no association between elevation of 'unmeasured' anions and mortality, although there was a trend towards hyperchloraemia in survivors ( P=0.08). Admission lactate was higher in nonsurvivors (median 11.6 vs 3.3 mmol/l; P=0.0003). Area under the mortality receiver operating characteristic curve for lactate was 0.83 (955 CI 0.70-0.95), compared to 0.71 (95% CI 0.53-0.88) for the PIM score. Admission lactate level >5 mmol/l had maximum diagnostic efficiency for mortality, with a likelihood ratio of 2.0.
  
  
  CONCLUSIONS
  There is no association between the magnitude of metabolic acidosis, quantified by the base excess, and mortality in children with shock. Hyperlactataemia, but not elevation of 'unmeasured' anions, is predictive of a poor outcome.
authors.affiliation: School of Child & Adolescent Health, University of Cape Town and Red Cross War Memorial Children's Hospital, Klipfontein Road, 7700, Cape Town, South Africa. hatheril@ich.uct.ac.za
authors.forename: Mark
authors.initials: M
authors.lastname: Hatherill
authors.forename: Zainab
authors.initials: Z
authors.lastname: Waggie
authors.forename: Langley
authors.initials: L
authors.lastname: Purves
authors.forename: Louis
authors.initials: L
authors.lastname: Reynolds
authors.forename: Andrew
authors.initials: A
authors.lastname: Argent
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000097:blood / Q000145:classification / Q000453:epidemiology / Q000209:etiology*; D001784:Blood Gas Analysis; D002648:Child; D002712:Chlorides / Q000097:blood; D017052:Hospital Mortality; D006776:Hospitals, Pediatric; D006785:Hospitals, University; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015994:Incidence; D007223:Infant; D015278:Intensive Care Units, Pediatric / Q000706:statistics & numerical data*; D019344:Lactic Acid / Q000097:blood; D016013:Likelihood Functions; D009017:Morbidity; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D012720:Severity of Illness Index; D012769:Shock / Q000150:complications* / Q000401:mortality*; D013019:South Africa / Q000453:epidemiology; D016019:Survival Analysis
chemical_list: D002712:Chlorides; D019344:Lactic Acid