Hypothermic to ischemic ratio and mortality in post-cardiac arrest patients

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  • Markus B Skrifvars, j Department of Anesthesiology, Intensive Care and Pain Medicine , University of Helsinki, Helsinki University Hospital , Helsinki , Finland.
  • ,
  • Eldar Soreide, Department of Occupational Medicine, Haukeland University Hospital, Bergen, Norway; Institute of Clinical Medicine, University of Bergen, Bergen, Norway.
  • ,
  • Kelly N Sawyer, Department of Emergency Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
  • ,
  • Fabio S Taccone, Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
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  • Valdo Toome, Department of Intensive Cardiac Care, North Estonia Medical Centre, Tallinn, Estonia.
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  • Christian Storm, Department of Internal Medicine, Nephrology and Intensive Care, Charité-Universitätsmedizin Berlin, Berlin, Germany.
  • ,
  • Anni Jeppesen
  • Anders Grejs
  • Christophe H V Duez
  • Marjaana Tiainen, Department of Neurology, Helsinki University Hospital and Department of Clinical Neurosciences (Neurology), University of Helsinki, Helsinki, Finland.
  • ,
  • Bodil S Rasmussen, Department of Anesthesiology and Intensive Care Medicine, Aalborg University Hospital, and Clinical Institute, Aalborg University, Aalborg, Denmark.
  • ,
  • Timo Laitio, Division of Perioperative Services, Intensive Care Medicine and Pain Management, Turku University Hospital, Turku, Finland
  • ,
  • Christian Hassager, Department of Cardiology, Rigshospitalet and Dept of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
  • ,
  • Hans Kirkegaard

BACKGROUND: We studied the associations between ischemia and hypothermia duration, that is, the hypothermic to ischemic ratio (H/I ratio), with mortality in patients included in a trial on two durations of targeted temperature management (TTM) at 33°C.

METHODS: The TTH48 (NCT01689077) trial compared 24 and 48 hours of TTM in patients after cardiac arrest. We calculated the hypothermia time from return of spontaneous circulation (ROSC) until the patient reached 37°C after TTM and the ischemic time from CA to ROSC. We compared continuous variables with the Mann-Whitney U test. Using COX regression, we studied the independent association of the logarithmically transformed H/I ratio and time to death as well as interaction between time to ROSC, hypothermia duration, and intervention group. We visualized the predictive ability of variables with receiver operating characteristic curve analysis.

RESULTS: Of the 338 patients, 237 (70%) survived for 6 months. The H/I ratio was 155 (IQR 111-238) in survivors and 114 (IQR 80-169) in non-survivors (P < .001). In a Cox regression model including factors associated with outcome in univariate analysis, the logarithmically transformed H/I ratio was a significant predictor of outcome (hazard ratio 0.52 (0.37-0.72, P = .001)). After removing an outlier, we found no interaction between time to ROSC and intervention group (P = .55) or hypothermia duration in quartiles (P = .07) with mortality. There was no significant difference in the area under the curve (AUC) between time to ROSC and H/I ratio (ΔAUC 0.03 95% CI -0.006-0.07, P = .10).

CONCLUSIONS: We did not find any consistent evidence of a modification of the effect of TTM based on ischemia duration.

Original languageEnglish
JournalActa Anaesthesiologica Scandinavica
Pages (from-to)546-555
Number of pages10
Publication statusPublished - Apr 2020

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