Admission Carboxyhemoglobin: Is It a Marker for Burn Patient Outcomes?

Background: Carbon monoxide is a gas produced by the combustion of hydrocarbon products that binds to heme molecules, 240 times more than oxygen, producing carboxyhemoglobin (COHb). As a result of its high affinity, there is shift of the oxyhemoglobin dissociation curve, compromising oxygen transport and delivery to tissues. Our study aim was to evaluate COHb elevation on admission as a predictor of worse outcomes in burn patients.

Methods: This is a 10-year retrospective review of the American Burn Association Burn Registry from 2002 to 2011. We stratified the patients into 2 groups: adult patients with normal COHb on admission (group 1) versus elevated COHb (group 2). Elevated COHb levels were defined as greater than 10% on the first arterial blood gas. Outcome measures included in-hospital mortality rate, hospital length of stay (LOS), intensive care unit LOS (ICU-LOS), and ventilator days. χ and t test analyses were used with significance defined as a P value of less than 0.05.

Results: A total of 6365 burn patients meet our inclusion criteria. There were 5775 patients in group 1 and 590 patients in group 2. Group 1 had an average age of 39.29 years compared with 42.62 years in group 2. The total body surface area was higher in group 1 compared with group 2 (6.24 vs 4.65) and with a statistically significant increase in partial thickness burns at 4.97 in group 1 compared with 3.27 in group 2. There was no statistically significant difference between the 2 groups in terms of full thickness total body surface area. The hospital LOS was significantly higher in group 2 compared with group 1 (15.34 vs 9.66). There was a significantly higher ICU-LOS at 12.89 days in group 2 compared with 4.01 in the group 1 (P = 0.0001, t test). There were higher ventilator days in group 2 at 9.23 than those in group 1 at 2.05 (P < 0.0001, t test). The in-hospital mortality was also significantly higher in group 2 at 15.59% than in group 1 at 1.33% (P = 0.0001, χ).

Conclusions: Elevated COHb on admission was associated with an increased hospital and ICU-LOS, average ventilator days, and in-hospital mortality. The presence of elevated COHb of greater than 10% on an initial arterial blood gas suggests worse outcomes and increased need of resource utilization during the index hospital admission.