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Background: After cardiopulmonary resuscitation, especially as a consequence of primary cardiac events an induced hypothermia improves cardiac outcome. The impact of therapeutic cold application to myocardial function and morphology of polytrauma patients after cardiac contusion and relevant hemorrhagic shock has not been investigated yet. The aim of the present work was to figure out if therapeutic hypothermia within a porcine long-term model for multiple trauma leads to a cardioprotective effect with deducible clinical relevance.
Materials und methods: The experimental group included 60 male pigs randomized into three cohorts. Two intervention cohorts with multiple trauma of varying severity (Cohort L, Low Blood Loss: n = 30, Cohort H, High Blood Loss: n = 20) and one control cohort with a sham treatment (Cohort C, Control: n = 10) were differentiated. Trauma consisted of blunt injury to the chest wall, liver laceration, pressure- and volume-controlled hemorrhage as well as a tibia fracture. All cohorts were separated into two groups. Mild therapeutic hypothermia down to 33 °C was applied to pigs of therapy groups after trauma for twelve hours with following rewarming. Laboratory animals of non-therapy groups stayed normothermic. Primary endpoint was histological evaluation graded by an ischemic score (range 0 - 3). Assessment of cardiac troponin levels and hemodynamic parameters were defined as secondary endpoints.
Results: Significant temperature-dependent relation did not occur neither for ischemic score (Cohort L: p = 0,436, Cohort H: p = 0,863) nor for troponin levels (Cohort L, H: TnI ratio 2 - 4 > 0,05). Significant results only refered to a positive correlation between higher histological scores as well as higher laboratory troponin levels with intensified trauma. A long-term temperature-dependent benefit of therapy groups was also not seen considering hemodynamic parameters process.
Conclusion: Therapeutic hypothermia within a polytrauma setting did not substantially influence cardiac outcome. However, consecutive vasoconstriction and bradycardia of cold application did not have measurable negative or positive effects on myocardium. Trauma severity seemed to affect the extent of myocardial injury. High mortality rates in case of multiple trauma with cardiac involvement demonstrate clinical relevance of the present work.