title: Higher Dead Space Is Associated With Increased Mortality in Critically Ill Children.
abstract: OBJECTIVE
  Elevated dead space has been consistently associated with increased mortality in adults with respiratory failure. In children, the evidence for this association is more limited. We sought to investigate the association between dead space and mortality in mechanically ventilated children.
  
  
  METHODS
  Single-center retrospective review.
  
  
  METHODS
  Tertiary care pediatric critical care unit.
  
  
  METHODS
  Seven hundred twelve mechanically ventilated children with an arterial catheter.
  
  
  METHODS
  None.
  
  
  RESULTS
  The end-tidal alveolar dead space fraction ((PaCO2-PETCO2)/PaCO2), a dead space marker, was calculated with each arterial blood gas. The initial end-tidal alveolar dead space fraction (first arterial blood gas after intubation) (per 0.1 unit increase: odds ratio, 1.59; 95% CI, 1.40-1.81) and day 1 mean end-tidal alveolar dead space fraction (odds ratio, 1.95; 95% CI, 1.66-2.30) were associated with mortality. The relationship between both initial and day 1 mean end-tidal alveolar dead space fraction and mortality held in multivariate modeling after controlling for any of the following individually: PaO2/FIO2, oxygenation index, 24-hour maximal inotrope score, and Pediatric Risk of Mortality III (all p<0.01), although end-tidal alveolar dead space fraction was no longer significant after controlling for the combination of oxygenation index, 24-hour maximal inotrope score, and Pediatric Risk of Mortality III. In 217 children with acute hypoxemic respiratory failure, initial end-tidal alveolar dead space fraction (per 0.1 unit increase odds ratio, 1.38; 95% CI, 1.14-1.67) and day 1 mean end-tidal alveolar dead space fraction (per 0.1 unit increase odds ratio, 1.60; 95% CI, 1.27-2.0) were associated with mortality. Day 1 mean end-tidal alveolar dead space fraction remained associated with mortality after controlling individually for any of the following in multivariate models: PaO2/FIO2, oxygenation index, and 24-hour maximal inotrope score (p≤0.02), although end-tidal alveolar dead space fraction was no longer significant after controlling for the combination of oxygenation index, 24-hour maximal inotrope score, and Pediatric Risk of Mortality III.
  
  
  CONCLUSIONS
  Increased dead space is associated with higher mortality in critically ill children, although it is no longer independently associated with mortality after controlling for severity of oxygenation defect, inotrope use, and severity of illness. However, because end-tidal alveolar dead space fraction is easy to calculate at the bedside, it may be useful for risk stratification and severity-of-illness scores.
authors.affiliation: 1Department of Anesthesiology and Critical Care Medicine, Children's Hospital Los Angeles, Los Angeles, CA. 2Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, CA.
authors.forename: Anoopindar K
authors.initials: AK
authors.lastname: Bhalla
authors.forename: Sanjay
authors.initials: S
authors.lastname: Belani
authors.forename: Dennis
authors.initials: D
authors.lastname: Leung
authors.forename: Christopher J L
authors.initials: CJ
authors.lastname: Newth
authors.forename: Robinder G
authors.initials: RG
authors.lastname: Khemani
mesh_terms: D019540:Area Under Curve; D001784:Blood Gas Analysis; D002140:California; D002245:Carbon Dioxide / Q000097:blood; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016001:Confidence Intervals; D016638:Critical Illness / Q000401:mortality*; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D017052:Hospital Mortality; D006801:Humans; D015994:Incidence; D007223:Infant; D015278:Intensive Care Units, Pediatric; D016015:Logistic Models; D008297:Male; D008991:Monitoring, Physiologic; D016017:Odds Ratio; D012372:ROC Curve; D012121:Respiration, Artificial / Q000379:methods*; D012126:Respiratory Dead Space / Q000502:physiology*; D012131:Respiratory Insufficiency / Q000175:diagnosis / Q000401:mortality* / Q000628:therapy*; D012189:Retrospective Studies; D015996:Survival Rate; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide