title: The effect of smoking status on burn inhalation injury mortality.
abstract: BACKGROUND
  Three factors that effect burn mortality are age, total body surface of burn (TBSA), and inhalation injury. Of the three, inhalation injury is the strongest predictor of mortality thus its inclusion in the revised Baux score (age+TBSA+17* (inhalation injury, 1=yes, 0=no)). However, the weighted contribution of specific comorbidities such as smoker status on mortality has traditionally not been accounted for nor studied in this subset of burn patients. We therefore sought to examine the impact of current tobacco and/or marijuana smoking in patients with inhalation injury.
  
  
  METHODS
  A retrospective analysis of patients admitted to a regional burn center from 2002 to 2012. Independent variables analyzed included basic demographics, burn mechanism, presence of inhalation injury, TBSA, pre-existing comorbidities, and smoker status. Bivariate analysis was performed and logistic regression modeling using significant variables was utilized to estimate odds of mortality.
  
  
  RESULTS
  There were a total of 7640 patients over the study period. 7% (n=580) of the burn cohort with inhalation injury were included in this study. In-hospital burn mortality for inhalation injury patients was 23%. Current smokers (20%) included cigarette smokers and marijuana users, 19% and 3%, respectively. Preexisting respiratory disease (17%) was present in 36% of smokers compared to 13% of non-smokers (p<0.001). Smokers had significantly lower mortality rate (9%) compared to non-smokers (26%, p<0.01). The logistic regression model for mortality outcomes identified statistically four significant variables: age, TBSA, ethnicity, and smoker status (OR=0.41, 95% CI=0.18-0.93). Presence of comorbidities, including preexisting respiratory disease, was not significant.
  
  
  CONCLUSIONS
  In the sub group of burn patients with inhalation injury, the odds of mortality significantly decreased in pre-existing smokers after adjusting for significant covariates. We postulate that an immune tolerance mechanism that modulates and diminishes the pro-inflammatory response confers a survival advantage in smokers after exposure to acute smoke inhalation injury. Future prospective studies in human and/or animal models are needed to confirm these findings.
authors.affiliation: Department of Surgery, University of North Carolina at Chapel Hill, North Carolina Jaycee Burn Center, United States.
authors.forename: Laquanda
authors.initials: L
authors.lastname: Knowlin
authors.affiliation: Department of Surgery, University of North Carolina at Chapel Hill, North Carolina Jaycee Burn Center, United States.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Stanford
authors.affiliation: Department of Surgery, University of North Carolina at Chapel Hill, North Carolina Jaycee Burn Center, United States.
authors.forename: Bruce
authors.initials: B
authors.lastname: Cairns
authors.affiliation: Department of Surgery, University of North Carolina at Chapel Hill, North Carolina Jaycee Burn Center, United States. Electronic address: anthchar@med.unc.edu.
authors.forename: Anthony
authors.initials: A
authors.lastname: Charles
mesh_terms: D000328:Adult; D000367:Age Factors; D001830:Body Surface Area; D005260:Female; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology; D007902:Length of Stay; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D065840:Protective Factors; D012189:Retrospective Studies; D015208:Smoke Inhalation Injury / Q000276:immunology / Q000401:mortality*; D012907:Smoking / Q000453:epidemiology* / Q000276:immunology; D015599:Trauma Severity Indices; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Burn inhalation injury; Burn mortality; Immune tolerance; Smoking