Effects Of Warm Water Bath Rewarming On Lung Injury And Serum Enzymology In Hypothermic SD Rats Induced By Long-term Seawater Immersion

When a shipwreck or naval warfare occurs,people who fall into the water are immersed in seawater,and the probability of seawater immersion hypothermia is higher.In the Falklands naval battle,the Argentine cruiser General General Belgrano sank quickly after being attacked by a British submarine torpedo,and 320 of the crew members fell into the water and disappeared.Most of them died after seawater immersion due to hypothermia.The current understanding of the mechanism and treatment of hypothermia induced by seawater immersion is not adequate.Even if timely treatment measures are adopted,the success rate of treatment for hypothermia casualties is still lower than 55%.Because it is difficult to search for and rescue the wounded at sea,especially during wartime,the treatment of the drowning person usually needs to wait for a long time.Immersion in seawater above 20?,the survival time of people is significantly longer.Previous hypothermia animal models usually were induced in a short time and did not reflect the chronic pathophysiological changes of hypothermia caused by long-term seawater immersion.Timely and appropriate rewarming is a key measure for the early treatment of hypothermia induced by seawater immersion.Previous studies at home and abroad mostly focus on active rewarming measures in vivo for patients with acute severe hypothermia,such as CRRT or ECMO.It is still controversial whether surface rewarming should be used in rescue practice because of its possible ‘rewarming shock' or ‘after-drop effect'.In the treatment of chronic hypothermia caused by long-term seawater immersion in the naval war time,if the casualty's consciousness is acceptable,and if there is no advanced re-warming equipment and professional medical personnel,it is difficult to grasp the advantages and disadvantages of warm water bath rewarming and other surface rewarming method in emergency treatment of hypothermia induced by long term seawater immersion.The impact of warm water bath rewarming on the body compared with passive rewarming remains unclear.In addition,seawater immersion hypothermia has the highest incidence of complications associated with lung injury,and its mortality rate is as high as 66.7%.Improper or untimely treatment may affect the final success rescue rate of of hypothermia.Changes in serum enzyme markers such as liver function,renal function,and myocardium enzymes can reflect the pathophysiological status of important organs,and those changes in hypothermia are very large.Observing the effects of rewarming method on lung pathological injury and important serum enzymology can evaluate the effectiveness of the rewarming method to some extent.In order to understand the pathophysiological changes of hypothermia caused by long-term seawater immersion and to lay the foundation for follow-up studies,we established a SD rats model of hypothermia induced by long-term seawater immersion.The pathological changes of important organs were observed in cross-sectionally.It was found that the lungs in this model were important target organs of hypothermia injury,and hypothermic pleural effusions and serum enzymology changes were obvious.On this basis,in order to evaluate the validity of warm water bath rewarming for long-term seawater immersion hypothermia in emergency,the rats were rewarmed by warm water bath and passively,and the degree of lung injury and serum enzymology changes of hypothermia rats before and after rewarming were compared.Part I Establishment of SD rats model of hypothermia induced by long-term seawater immersionObjective: To establish SD rats model of hyperthermia induced by long-term seawater immersion.Methods: Twenty adult male Sprague-Dawley rats were randomly divided into normal control group and hypothermia experimental group,with 10 rats in each group.The normal control group was not treated.The experimental group was immersed in artificial seawater at 20 ? for 24 h using a self-made rat water bath fixture.The changes of vital signs in rats were observed.After the experiment,the body temperature,common hematological indexes and the pathological changes of vital organs were detected.Results: Heart rate,respiration,consciousness,etc.of the hypothermia experimental group decreased significantly compared with the normal control group in the cold seawater immersion process,and the core temperature was close to 20 ? after the immersion.The hematological indicators were obviously abnormal in hypothermic rats,and pathology suggested that all vital organs had different degrees of damage,of which the lung pathological damage is more serious.There are alveolar structural damage,alveolar and interstitial hemorrhage,inflammatory cell infiltration and other changes in the hypothermia's lungs.Conclusion: The SD rat model of long-term seawater immersion hypothermia was successfully established and could be used for subsequent studies.The lung is an important target organ of hypothermia injury.Part II Effects of warm water bath rewarming on lung injury and serum enzymology in hypothermic SD rats induced by long-term seawater immersionObjective: To observe the pathological changes of the lung and serum enzymological changes before and after rewarming in hypothermic SD rats induced by long-term seawater immersion through warm water bath rewarming compared to passive rewarming,and to initially evaluate the validity of warm water bath rewarming in long-term seawater immersion hypothermia's treatment.Methods: One hundred male Sprague-Dawley rats were randomly divided into normal control group(without any treatment),hypothermia experimental group(seawaterimmersion at 20 ? for 24h),passive rewarming group 1,2,3,4(seawater immersion at20 ? for 24 h + Passive rewarming,respectively executed after rewarming 0h,3h,6h and12h),active rewarming group 1,2,3,4(seawater immersion at 20 ? for 24 h + warm water bath rewarming,respectively executed after rewarming 0h,3h,6h and 12h),10 in each group.Mainly to detect changes in lung pathology and serum liver function,renal function,myocardial enzyme and other indicators.Results: Warm water bath rewarming and passive rewarming all restored the lung injury and hematological abnormalities in rats with long-term seawater immersion hypothermia.Compared with the passive rewarming group,the recovery of lung pathological injury was better at 6h and 12 h after rewarming in the warm water bath rewarming group,P < 0.05;the actual bicarbonate recovery was better at 6h after rewarming,P<0.05;the liver function index increased littler at 0h after rewarming,and recovered better at 3h and 6h after rewarming,P<0.05;the renal function index increased littler at 0h after rewarming,and recovered better at 3h,6h and 12 h after rewarming,P<0.05;the myocardial enzyme index increased littler at 0h after rewarming,and recovered better at 3h and 6h after rewarming,P<0.05.Conclusion: Compared with passive rewarming,warm water bath rewarming is more effective in repairing lung injury and hematological abnormalities in rats with long-term seawater immersion hypothermia.Warm water bath rewarming is more effective than passive rewarming in the emergency treatment of the hypothermia caused by long-term seawater immersion in naval battles.