Einfluss milder therapeutischer Hypothermie auf die respiratorische und kardiale Funktion nach primär erfolgreicher kardiopulmonaler Reanimation

Abstract

Since decades, survival remains poorly after resuscitation. Mild therapeutic hypothermia (MTH) is the only therapy that has been shown to significantly improve neurologic recovery and survival rates after return of spontaneous circulation. One possible method for induction and maintenance of a body temperature of ≤34°C for 12-24 hours is the infusion of large volume 2-4°C ice-cold intravenous fluid. In context of post-cardiac arrest syndrome (PCAS), impaired myocardial function as well as systemic inflammatory response syndrome (SIRS) with hemodynamic instability in resuscitated patients does however raise concerns about inducing pulmonary edema by rapid infusion of large fluid volumes. In the present study, the effects of ice-cold fluid on respiratory function were investigated. In addition, the influence of mild hypothermia on catecholamine dosage for hemodynamic stabilization and on hemodynamic parameters was evaluated. Therefor the respiratory parameters of 166 patients and the cardiac parameters of 159 patients were statistically analyzed during hypothermia. Respiratory data: The initial ejection fraction (EF) was 34,8%. This corresponds to a moderately impaired left ventricular (LV) function. On arrival at the intensive care unit, the Horowitz index (PaO2/FiO2) as a measure for the oxygenation function of the lung, was 210mmHg with a PEEP level of 7 mbar. This corresponds to a mild to moderate acute respiratory distress syndrome (ARDS). Until reaching the target temperature of ≤34 ◦C (4,5h), 3.279ml ice-cold fluid were infused. The Horowitz index remained at 210 mmHg, with unchanged PEEP level of 7 mbar. There was a slight, but significant negative linear correlation between Horowitz index and infused volume (0-11.000 ml). These results indicate that the infusion of fluid does not impair the oxygenation function of the lung. Due to the slight correlation between Horowitz index and infusion rate however, the respiratory parameter should be frequently monitored during the infusion period. Hemodynamic data: The initial moderately impaired LV function (EF 34,7%) improved during the course to 41,5%. Under MTH, the infusion rate of epinephrine was significantly reduced, the norepinephrine dosage was significantly increased. In the same period, the heart beat decreased significantly. These results confirm earlier studies, that were able to show a positive inotropic effect and a reduction of heart beat through MTH. Probably, due to the vasodilation in context of the PCAS, there is an additional need for vasoconstrictors.