Adenosine-triphosphate in trauma-related and elective hypothermia

Background: In trauma patients, hypothermia is a frequent event. According to the literature, the majority of trauma patients are presenting a core te mperature of less than 34 degrees C at admission. In contrast to the benefi t of hypothermia in elective surgery, clinical experience with hypothermia in trauma patients has identified hypothermia to be one major cause of seve re posttraumatic complications. It was hypothesized that this diverse effec t of hypothermia is related to depletion of high-energy phosphates like ade nosine triphosphate (ATP) in trauma patients. To verify this hypothesis, th e relation of ATP plasma levels and hypothermia was examined in a clinical study. Methods: Three different groups of patients were under study. The first gro up (group A, normothermic control group) included patients (n = 15) undergo ing elective surgery of the lower limb with a mean operation time of 113 mi nutes. The second study group (group B, hypothermic control) was composed o f patients (n = 15) who were subjected to elective coronary artery bypass o peration under hypothermia (31 degrees C for 48 minutes, mean total operati on time being 205 minutes). The third study group (group C) included trauma patients (n = 23, mean Injury Severity Score [ISS] of 24.7), At the time o f admission, 10 patients presented a core temperature more than or equal to 34 degrees C (group C1, mean ISS, 25.2; mean T-A, 34.5 degrees C), 13 pati ents presented a T-A less than 34 degrees C (group C2, mean ISS, 26.0; mean T-A, 32.9 degrees C). In both groups of surgical patients, the ATP plasma level was measured preoperatively, at 2, 4, and 23 hours postoperatively. F or trauma patients, this measurement was performed at admission and 23 hour s later. Within the same schedule, body core temperature was recorded and t he clinical course was documented as well, Results: Elective limb surgery in normothermic patients resulted only in a transient decrease in ATP plasma levels (preoperative, 87.8 mu mol/dL; 4 ho urs postoperative, 52.0 mu mol/dL). At 24 hours, the ATP plasma level (62.6 +/- 10.0 mu mol/dL) has increased toward baseline level. Elective hypother mia in patients subjected to coronary bypass also resulted only in a transi ent decrease in ATP plasma levels. During the operation period, including h ypothermia, the ATP plasma level was comparable (50.4 mu mol/dL) to group A and also returned back toward normal values at 24 hours (58.2 mu mol/dL). All trauma patients revealed a significant low ATP plasma level at admissio n compared with both control groups. Looking at subdivided groups the most significant drop in ATP plasma level (28.5 mu mol/dL) was noted in patients presenting an initial core temperature less than 34 degrees C and ISS more than 30, Even 24 hours later, the ATP level of this subgroup was significa ntly diminished, despite a rise up to 44.4 mu mol/dL. In contrast, only a m oderate drop in ATP plasma concentration (59.2 mu mol/dL) was noted in the group of T-A more than or equal to 34 degrees C and ISS less than 20, This group revealed almost normal values (68.3 mu mol/dL) 23 hours after trauma. In addition to hypothermia, the metabolic state, reflected by the plasma l actate levels, significantly influenced the ATP plasma levels, as high lact ate levels mere paralleled by low ATP levels, Also, the overall outcome was related to injury severity and hypothermia. Conclusion: Hypothermia in elective surgery, established by active cooling, preserves the ATP storage and maintains an aerobic metabolism, which both contribute to the beneficial effect of hypothermia in ischemia/reperfusion in cardiovascular surgery, However, in trauma patients hypothermia is cause d by insufficient heat production due to utilization of ATP under anaerobic metabolic conditions. Low ATP plasma levels combined with hypothermia seem to be a predisposition for post-traumatic complications like organ failure .