Hypothermia and trauma

Sammanfattning: Background Accidental hypothermia (HT) has been found to increase morbidity and mortality in trauma patients. In contrast, HT has been induced in certain surgical procedures for several decades because of its cerebroprotective properties. HT has even been used therapeutically in patients with traumatic brain injury. In recent years, a number of experimental studies have suggested beneficial effects of induced HT in hemorrhagic shock (HS), but just how induced HT affects the organism subjected to both HS and trauma has been unknown, hitherto. Methods In papers I & II, animals were exposed to 5 0% exsanguination during 25 minutes. In paper III, a standardized gunshot wound was inflicted on the right hind-leg. In paper IV, animals were subjected to the combination of these insults. In paper V, the hemorrhage amounted to 40% of the blood volume and was achieved in 3-5 minutes. Core temperature, electrolytes, arterial blood gases, blood cell counts, Hb, and central hemodynamics were monitored in an the studies. Catecholamines were analyzed in papers I-IV. IL-6 was studied in papers III-IV. Thromboelastography was used to evaluate coagulation abnormalities in paper V. In this paper, animals were rewarmed after cooling. Results Paper I. Catecholamine levels in plasma increased in response to the hemorrhage, but gradually decreased with cooling. Serum potassium levels increased in the controls, but decreased transiently in HT animals. Paper : HR increased markedly after the hemorrhage, while CO and MAP were reduced. With HT, HR decreased and CO and MAP wore further depressed Leukocyte counts decreased in HT animals. Paper : HR, MAP, neutrophil granulocyte counts and plasma adrenaline levels were lower in the HT group. Cardiac index decreased slightly in both groups. Serum potassium increased with normothermia, but was not affected in HT pigs. Paper IV: HR, V02, ER, scrum potassium, and creatinine levels were lower with cooling. Paper V: V02 was reduced in HT animals. Serum levels of potassium were transiently stabilized with HT. The formation of blood clots was delayed, but once formed, the clot strength was unaffected by HT. Effects of HT were reversed with rewarming. Conclusions In HS and/or soft-tissue trauma, HT reduced plasma catecholamine levels and transiently stabilized serum levels of potassium. Central hemodynamics after the combination of the insults was affected by HT to a remarkably small extent, while V02 and ER decreased. In the presence of rewarming hemodynamics, V02 and ER regained baseline levels.