Introduction
Maintenance of adequate brain perfusion is an essential component of post-resuscitation care. Mean arterial pressure (MAP) and PaCO2 are important determinants of brain perfusion; however, no precise guidelines exist for optimal MAP and PaCO2 targets in comatose post-cardiac arrest (CA) patients.
Methods
Using NIRS, we examined changes in non-invasive cerebral tissue oxygen saturation (SctO2) following moderate hyperventilation (HV) and induced hypertension (IH) in comatose CA patients treated with therapeutic hypothermia (TH). A prospective pilot study including comatose patients successfully resuscitated from out-of-hospital CA treated with TH (33°C for 24 hours, using cold saline and surface cooling device), monitored for continuous SctO2 with the Foresight NIRS system (CAS Medical Systems, Branford, CT, USA). Moderate hyperventilation was induced for approximately 30 minutes by decreasing PaCO2 from ~40 to ~30 mmHg, at stable MAP. After PaCO2 normalization, MAP was increased from ~70 to ~90 mmHg by intravenous infusion of norepinephrine, at stable PaCO2. Effects of MV and IH on SctO2 were analyzed with a paired t test.
Results
Ten patients (mean age, 69.5; mean time to ROSC, 19 minutes) were studied during the stable TH maintenance phase. Results are summarized in Figure 1. MV was associated with a significant reduction of SctO2 from baseline (75% (73 to 76) to 69% (67.5 to 71.5), P < 0.001).
No significant changes in SctO2 were found after IH (74 (72 to 76) vs. 75 (73 to 75.5), P = 0.24).
Conclusion
Moderate HV was associated with significant reduction in cerebral saturation, whilst IH may be detrimental after CA and TH, whilst increasing MAP to supranormal levels with vasopressors does not improve cerebral oxygenation. These data stress the importance of strict control of PaCO2 following CA and TH to avoid secondary cerebral ischemic insults.
Changes in SctO 2 after moderate HV and IH tests ( n = 10 patients).
Acknowledgements
MO is supported by Grants from the Swiss National Science Foundation (FN 320030_138191) and The European Critical Care Research Network (ECCRN).
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Suys, T., Sala, N. & Oddo, M. Effect of moderate hyperventilation and induced hypertension on cerebral tissue oxygen saturation in comatose post-cardiac arrest patients treated with hypothermia. Crit Care 17 (Suppl 2), P311 (2013). https://doi.org/10.1186/cc12249
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DOI: https://doi.org/10.1186/cc12249