Effects of carbon monoxide inhalation on lung injury induced by brain death in rats

Abstract

Objective To investigate the effects of carbon monoxide (CO) inhalation on lung injury induced by brain death (BD) in rats. Methods Adult male Wistar rats weighing 250-300 g were used in this study. The animals were anesthetized with intraperitoneal pentobarbital sodium 60 mg/kg, tracheostomized and mechanically ventilated (VT 10 ml/kg, RR 50 bpm, PEEP 2 cm H2O). A balloon-tip catheter was placed in the cranium. Twenty-four rats in which Fogarty catheter was successfully placed in the cranium without complication were randomly divided into 3 groups ( n = 8 each) : group I sham operation (group S) ; group II BD and group Ⅲ BDCO. BD was induced by increase in intracranial pressure produced by inflating the balloon at the tip of the catheter. In group S the balloon of the catheter was not inflated. The animals inhaled 40% O2 for 150 min. In group BD, BD was induced and confirmed at 30 min after inflation of the balloon. Then 40% O2 was inhaled for 120 min. In group BDCO, 40% O2 and 0.025% CO were inhaled for 120 min after BD was confirmed at 30 min after balloon inflation. At the end of the experiment the animals were killed. Arterial blood samples were obtained for blood gas analysis before anesthesia (basline), immediately after confirmation of BD, and at 30, 60, 90 and 120 min of CO inhalation. Blood was collected for determination of plasma TNF-α, IL-6 and IL-10 concentrations at 120 min of CO inhalation. The lungs were obtained for determination of W/D lung weight ratio, and MPO activity in the lung tissue and microscopic examination. Lung injury scores were calculated. Results PaO2/FiO2 was stable during the 150 min in group S. Brain death significantly decreased PaO2/FiO2 at 30 min after balloon inflation. PaO2/FiO2 was gradually decreasing during the 120 min in group BD. CO inhalation prevented PaO2/FiO2 from decreasing further. W/D lung weight ratio and MPO activity were significantly higher in group BD than in group S and BDCO. The lung injury score (1 = normal, 4= severely injured) and plasma TNF-αα IL-6 and IL-10 concentrations were significantly higher in group BD than in group S. CO inhalation ameliorated the BD-induced lung injury and attenuated the increase in plasma TNF-a and IL-6 concentration. Plasma IL-10 concentration was significantly higher in group BDCO than in group BD. Conclusion CO inhalation can ameliorate acute lung injury induced by BD through decreasing the local and systemic inflammatory response. Key words: Carbon monoxide; Brain death; Lung