Objective: To study the effect of hypothermia on pro-inflammatory mediators in serum, the enzymology and pathology of lung tissue.
Methods: Ventricular fibrillation for 4 minutes was induced in 10 domestic pigs. Standard cardiopulmonary resuscitation was given to them. They were then divided into two groups according to the random table after restoration of spontaneous circulation (ROSC): low temperature group (n=5): pigs were given an infusion 30 ml/kg of 4 centigrade normal saline (NS) at an infusion rate of 1.33 ml * kg(-1) * min(-1), started after ROSC for 22 minutes, then 10 ml * kg(-1) * h(-1) for 4 hours; ambient temperature group (n=5) received the same infusion of NS in room temperature. Hemodynamic parameters were observed, blood samples were collected to measure tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in serum before ventricular fibrillation and 10 minutes, 2 hours, 4 hours after ROSC. Na(+)-K(+)-ATPase of lung tissue was determined 24 hours after ROSC, and the pathology and ultrastructure of the lung were studied.
Results: There was no significant difference in the hemodynamic parameters, except the temperature, between low temperature and ambient temperature groups. TNF-alpha contents at 10 minutes, 2 hours, 4 hours after ROSC in low temperature group were (15.55+/-1.65), (17.06+/-0.86), (12.52+/-1.82) ng/L, and the IL-6 contents were (173.80+/-15.01), (184.09+/-13.44), (73.17+/-6.95) ng/L, while the TNF-alpha contents at 10 minutes, 2 hours, 4 hours after ROSC in ambient temperature group were (20.09+/-1.32), (26.18+/-1.16), (29.18+/-1.20) ng/L, and the IL-6 contents were (176.92+/-16.68), (239.17+/-13.18), (405.48+/-55.49) ng/L. The pro-inflammatory mediators in low temperature group were reduced significantly (P<0.05 or P<0.01). Low temperature could significantly reduce the activity of Na(+)-K(+)-ATPase [(3.78+/-1.14) U/L vs. (6.22+/-1.23) U/L, P<0.01]. The pathology of lung was milder in low temperature group compared with that of ambient temperature group.
Conclusion: Hypothermia therapy with infusion of 4 centigrade NS can reduce the release of pro-inflammatory mediators, inhibit the ATPase activity of alveolar membrane, and shows a protective effect on lung tissue against low perfusion.