A Study Of Hypothermia In The Treatment Of Acute Lung Injury Induced By Intestinal Ischemia-reperfusion

Objective: To study of hypothermia in the treatment of acute lung injury induced by intestinal ischemia-reperfusion and explore it's possible underneath mechanism.Methods: 108 healthy rabbits were randomly divided into 6 groups (n=18 per group): normothermia intestinal ischemia-reperfusion groups (rectal temperature 37-38℃); mild hypothermia group (rectal temperature 32-35℃); moderate hypothermia group (rectal temperature 28-31.9℃); delayed mild hypothermia group (rectal temperature 32-35℃); delayed moderate hypothermia (rectal temperature 28-31.9℃); normothermia control group (rectal temperature 37-38℃, the sham group).The rabbit models of acute lung injury were produced by clamping super mesenteric artery (SMA) for 1 hour and declamping SMA for 6 hours. Hypothermia was induced by surface cooling. Monitoring heart rate, arterial pressure and breath rate and obtaining arterial blood for blood gas analysis. Before intestinal ischemia-reperfusion and 2, 4, 6 hours after, levels of TNF-α, IL-1β, IL-6, IL-10 in plasma were measured; six hours after intestinal ischemia-reperfusion, levels of PT, SP-A in plasma and TNF-α, IL-1β, IL-6, IL-10, SP-A in BALF were measured. Six hours after intestinal ischemia-reperfusion, eight rabbits selected randomly per group were killed to measure levels of MPO, MDA, SOD, the ATP enzyme, lung water and lactic acid in tissues of lung. Light microscopic examination was performed for morphological measurement of lung. The survival numbers of rabbits in 24 hours were observed.RESULTS: In IR groups, levels of TNF-α, IL-1β, IL-6, IL-10 in plasma and BALF increased, PaO₂ decreased, levels of SP-A increased in plasma and decreased in BALF. Lung water and the level of MPO, MDA and lactic acid increased in IR groups, SOD and the ATP enzyme in tissues of lung decreased. There were evidences of acute lung injury in morphological measurement of lung. The acute lung injury induced by intestinal ischemia-reperfusion were improved by hypothermia. Mild hypothermia was similar with moderate hypothermia in treatment of ALI induced by IIR. Mild hypithermia less impact than moderate hypothermia on hemodynamics, respiratory and blood coagulation. Delayed hypothermia improved partialy the acute lung injury induced by intestinal ischemia-reperfusion.Conclusion: (1) We observed rabbits ALI induced by IIR in this study. (2) Mild hypothermia and moderate hypothermia can improved significantly ALI induced by IIR in rabbits. (3) Mild hypothermia was similar with moderate hypothermia in treatment of ALI induced by IIR. Mild hypithermia less impacted than moderate hypothermia on hemodynamics, respiratory and blood coagulation. Mild hypothermia group's survival duration was longer than moderate hypothermia group. (4) Delayed hypothermia improved partialy the acute lung injury by intestinal ischemia-reperfusion.