Assessment of Erythrocyte Cholinesterase Activity in Victims of Smoke Inhalation

Abstract

Background: The nature of the toxic gases that cause death from smoke inhalation is incompletely understood, and the mechanisms leading to incapacitation remain to be determined. Thermal degradation products of various compounds, including phosphorous-based fire retardants, are suspected capable of impairing human cholinesterase activity. The aim of this study was to measure the erythrocyte cholinesterase activity in victims of smoke inhalation. Methods: We prospectively measured the erythrocyte cholinesterase activity in blood samples obtained at the scene of residential fires from 49 fire victims. We compared the results with those in an unmatched group of 45 persons with acute drug poisoning. Results: The median (25th–75th percentiles) erythrocyte cholinesterase activity in the 49 fire victims, 1968 IU/L (1660–2276), was significantly lower than in the 45 control subjects 2460 IU/mL (1968–2890), (p = 0.0004). There was no significant difference of the red blood cell counts or plasma protein levels between the 2 groups, while the hematocrit was significantly greater in the fire victims than in the drug-poisoned patients. There was a significant correlation between blood cyanide and carbon monoxide concentrations in the fire victims (r = 0.494, p = 0.002). There was no correlation between erythrocyte cholinesterase activity and either blood cyanide (r = 0.11, p = 0.44) or blood carbon monoxide concentrations (r = 0.04, p = 0.78). Conclusions: We found a significantly lower level of erythrocyte cholinesterase activity in victims of residential fires, when compared with a convenience sample of hospitalized poisoned patients. Despite the limitations of the study, investigations of the toxic gases potentially responsible for impairment of cholinesterase activity and the clinical significance of this lower enzymatic activity merit further investigation.