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EXACT Trial – Oxygen Saturation Targets after Cardiac Arrest

January 3, 2023

Written by Laura Murphy

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Targeting a lower oxygen saturation (90-94%), compared to standard care (98-100%), in patients who were resuscitated after out-of-hospital cardiac arrest (OHCA) until admission to the intensive care unit did not significantly improve survival to hospital discharge.

Why does this matter?
The ideal oxygenation range for ICU patients appears to be 94-98%. Hypoxia is bad. Hyperoxia is less clear. What about the immediate post-resuscitation period? Does a lower oxygenation target matter for OHCA patients?

It’s hard to be EXACT…
This was a multicenter, parallel-group, randomized controlled trial which included unconscious adults with return of spontaneous circulation after OHCA, advanced airway placement, and a peripheral oxygen saturation (SpO2) of at least 95% while receiving 100% oxygen. Patients were randomized to receive oxygen therapy to target oxygen saturation of either 90-94% (intervention) or 98-100% (standard care). Primary outcome was survival to hospital discharge, with multiple secondary outcomes including hypoxic events (SpO2<90%), re-arrest, and Cerebral Performance Category (CPC) score at 12 months, and several others.

The trial was stopped early due to the COVID-19 pandemic; a total of 428 patients were randomized. Baseline characteristics were similar in the intervention (90-94%) and standard group (98-100%). In the intervention group, 38.3% survived to hospital discharge compared with 47.9% in the standard care group: -9.6% difference (95%CI -18.9% to -0.2%). Since the study was underpowered, results are not clear but appear to favor standard care group. There was no significant difference in prespecified adverse events. There was a higher rate of hypoxic events prior to ICU admission in the intervention group (31.3%) compared to the standard group (16.1%). In subgroup analyses, results generally favored the standard care group, though were not statistically significant.

While further studies may be needed to definitively answer this question, the results from this trial suggest that the risk of hypoxia with conservative oxygenation strategies may outweigh the benefit of avoiding hyperoxia in the prehospital setting. Of note, in this study population, there was a high survival rate to hospital discharge (exceeding 40%) as well as a high percentage of patients with shockable rhythms (>60% in both groups), which limits generalizability of these results.

Source
Effect of Lower vs Higher Oxygen Saturation Targets on Survival to Hospital Discharge Among Patients Resuscitated After Out-of-Hospital Cardiac Arrest: The EXACT Randomized Clinical Trial. JAMA. 2022 Nov 8;328(18):1818-1826. doi: 10.1001/jama.2022.17701.

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