Influence of core body temperature on Tryptophan metabolism, kynurenines, and estimated IDO activity in critically ill patients receiving target temperature management following cardiac arrest

• Published in: Resuscitation Vol. 107; pp. 107 - 114
• Main Authors: Schefold, Joerg C, Fritschi, Nora, Fusch, Gerhard, Bahonjic, Aldin, Doehner, Wolfram, von Haehling, Stephan, Pschowski, Rene, Storm, Christian, Schroeder, Tim
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01-10-2016
• Subjects: Aged; Body Temperature; Cell-mediated immune system; Coma - diagnosis; Coma - etiology; Coma - metabolism; Critical Illness - mortality; Critical Illness - therapy; Emergency; Female; Germany; Heart Arrest - complications; Heart Arrest - therapy; Humans; Hypothermia, Induced - adverse effects; Hypothermia, Induced - methods; Indoleamine 2,3 dioxygenase; Indoleamine-Pyrrole 2,3,-Dioxygenase - metabolism; Inflammation; Intensive care unit patients; Kynurenine - metabolism; Male; Middle Aged; Neurologic Examination - methods; Outcome Assessment (Health Care); Prognosis; Recovery of Function; Sepsis; Statistics as Topic; Systemic Inflammatory Response Syndrome - etiology; Systemic Inflammatory Response Syndrome - metabolism; Target temperature management; Tryptophan - metabolism; Cell-mediated immune system; Sepsis; Target temperature management; Inflammation; Intensive care unit patients; Indoleamine 2,3 dioxygenase
• ISSN: 0300-9572; 1873-1570
• DOI: 10.1016/j.resuscitation.2016.07.239

Abstract Background/Aims Temperature control improves neurological prognosis in comatose cardiac arrest (CA) survivors. Previous reports demonstrate that most affected patients show signs of significant systemic inflammation. In an effort to better characterize potential temperature-related effects on key inflammatory pathways, we investigate the course of Tryptophan (Trp) levels, Tryptophan catabolites (including kynurenines) and indoleamine-2,3-dioxygenase (IDO)-activity in post CA patients. Material/Methods In an observational blinded endpoint analysis, a total of n = 270 serial samples from 20 post CA patients (63.1 ± 16.6 yrs., 45% shockable rhythm, mean time to return of spontaneous circulation (ROSC) 26.6 ± 16.0 minutes) treated with target temperature management (TTM) were analysed. Core body temperatures, course of Trp, Trp catabolites (incl. kynurenines), and estimated IDO-activity were followed up for a maximum of 7 days after ROSC. Patients were followed up until hospital discharge or death and functional outcome was recorded. Results Over the 7-day observational interval, marked changes in Trp serum levels and IDO-activity were noted. In general, Trp serum levels but not IDO-activity seemed to parallel with the course of core body temperature. In explorative analyses, a correlation of Trp (rho = 0.271 (95%-CI: 0.16-0.38, p < 0.0001) and IDO-activity (rho= -0.155, 95%-CI: -0.27--0.037, p = 0.01) with core body temperature was observed. Linear mixed effect models revealed a positive significant association of core body temperature with Trp serum levels (Likelihood ratio test χ2 = 6.35, p = 0.012). In patients with good (vs. unfavourable) outcome, a tendency towards higher Trp serum levels, lower IDO-activity, and lower Kynurenic acid levels was noted. Conclusions We observed significant changes in Trp catabolism and IDO-activity that appeared temperature associated in post CA patients. Under hypothermia, decreased serum levels of Trp and increased IDO-activity were noted. We speculate from our data that IDO-induction during hypothermia contributes to the previously described increased susceptibility to infection or sepsis under reduced temperatures.