Aspiration of Activated Charcoal Elicits an Increase in Lung Microvascular Permeability

Abstract

Background: Gastric decontamination with orally administered activated charcoal is the recommended treatment for many poisonings, However, ingestion of central nervous system depressants resulting in loss of protective airway reflexes may result in pulmonary aspiration of activated charcoal. Although activated charcoal has been reported to be an inert substance, evidence suggests that pulmonary aspiration of charcoal is associated with lung edema formation and pulmonary compromise. This study tested the hypothesis that intratracheal instillation of activated charcoal disrupts the integrity of the lung microvascular barrier. Methods: The capillary filtration coefficient (Kf, c), a sensitive measure of lung microvascular permeability, was determined isogravimetrically prior to and after intratracheal instillation of activated charcoal 0.04g/kg (12% weight/vol solution, pH 7.4) or an equal volume of sterile water in isolated, perfused rat lungs. Arterial blood gas analysis was determined prior to and after tracheal instillation of activated charcoal or sterile water in a separate group of animals. Results: Intratracheal instillation of activated charcoal resulted in a significant increase in pulmonary microvascular permeability compared to lungs treated with sterile water or control lungs (ΔKf_f,c = +0.21±0.076; −0.014±0.04; and −0.041±0.02 mL/min/cm H₂O/100 g lung tissue, respectively, p<0.05 ANOVA). There was no significant difference in baseline blood gases in the 3 experimental groups. There was a significant decrease in arterial Po₂, bicarbonate, and pH in animals administered activated charcoal compared to time-matched controls and animals administered sterile water. Conclusions: Intratracheal instillation of activated charcoal is associated with a significant increase in lung microvascular permeability and arterial blood gas derangements. The effects of activated charcoal on pulmonary microvascular barrier integrity may contribute to the lung edema formation and pulmonary compromise observed following clinical aspiration of activated charcoal.