Extracorporeal Life Support: What Should We Be Targeting?*
The topic is clinically relevant, as, once ECLS is initiated, the intensive care team has considerable latitude in controlling previously uncontrollable oxygenation. Adjustment of pump blood flow allows titration of oxygen delivery to vary systemic oxygenation along the important ranges of the oxygen-hemoglobin saturation curve. With this latitude comes the question of “what is the most appropriate PaO2 target?.” This is not clearly established, and definition of appropriate goals of therapy on ECLS would clearly enhance current practice.
From a more general ICU perspective, we know that this answer is not simple; higher oxygen targets are not necessarily better. In the original acute respiratory distress syndrome Network ARMA tidal volume study, the 12 mL/kg group had earlier reversal of hypoxemia, yet also had higher overall mortality (10). In contrast, mortality and long-term cognitive outcomes may be adversely affected by hypoxemia in the ICU (11, 12). A 2014 Cochrane systematic review identified no randomized trials meeting criteria for evaluating hypoxemia versus normoxemia in critically ill patients (13). Internationally, several randomized trials to evaluate oxygenation targets in the ICU are in progress or in the planning stages (ICU-ROX [Australian and New Zealand Intensive Care Society, Australian New Zealand Clinical Trials Registry Number 12615000957594], O2-ICU [NCT02321072], HOT-ICU [NCT03174002], LOCO2 [NCT02713451]).