Associationbetween hyperoxia and mortality in severely burned patients

INTRODUCTION

The use of oxygen is a key component of acute burn resuscitation, particularly when there is concern for carbon monoxide toxicity or inhalation injury. Prior studies of critically-ill patients have shown an association between early hyperoxia and increased mortality. There are no studies to date evaluating outcomes related to excessive oxygen administration in burn patients.

METHODS

We conducted a retrospective analysis of 219 severely burned patients to quantify the average amount of oxygen given during initial resuscitation, the level of carbon monoxide exposure, and to determine if early exposure to supratherapeutic oxygen was associated with increased hospital mortality or ventilator-associated pneumonia (VAP). The models were adjusted for inhalation injury and total body surface area (TBSA) burned.

RESULTS

Early hyperoxia in severely burn patients is common and possibly associated with increased overall mortality, although the results were inconclusive and after adjusting for burn-specific scoring systems, we found a negative correlation between hyperoxia and mortality. Confirmed carbon monoxide poisoning was relatively uncommon, but also associated with increased mortality. Patients with elevated carboxyhemoglobin did not receive more oxygen compared to others within the cohort.

CONCLUSIONS

Burn patients are exposed to higher concentrations of pure oxygen compared to other critically-ill patients, presumably for empiric treatment of carbon monoxide poisoning. Our data showed a liberal use of oxygen therapy across all patients. Considering the potentially negative effects of hyperoxia, this study exposes either a gap in clinical research or need for clearer indications.

A comparison of injury scoring systems in predicting burn mortality

The models most widely used to predict burn patient mortality are the revised Baux score, Ryan, Smith, McGwin, Abbreviated Burn Severity Index (ABSI), Belgian Outcome of Burn Injury (BOBI), and the Fatality by Longevity, APACHE II score, Measured Extent of burn, and Sex (FLAMES). Improvements in critical care have reduced mortality resulting from severe burns, which may affect the predictive strength of older models. We conducted a cross-validation study on all burn patients (n = 114) with TBSA greater than 20%, admitted to the Arizona Burn Center between 2014 and 2016. The study compared the accuracy of seven previously validated burn-specific models and one new model derived for our cohort. Data were collected on age, ethnicity, gender, total body surface area burned (TBSA), inhalational injury, associated trauma, and injury severity (ISS, APACHE II). The accuracy of each model was tested using logistic regression, preserving the published regression coefficients. Predictive performance of the models was assessed by Receiving Operator Curve (ROC) curve analyses and Hosmer-Lemeshow (H-L) goodness of fit tests. Age, TBSA and APACHE II score were found to be significant, independent risk factors for patient mortality. The FLAMES model performed best (AUC 0.96) and was comparable to our native model (AUC 0.96). The revised Baux score was both accurate and easy to calculate, making it clinically useful. The older models demonstrated adequate predictive performance compared with the newer models. Even without key burn parameters, the APACHE II score performed well in critically ill patients with moderate to severe burn injuries.