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Correspondence
Letter by Bellomo et al Regarding Article,
“Relationship Between Supranormal Oxygen
Tension and Outcome After Resuscitation From
Cardiac Arrest”
To the Editor:
We read the paper by Kilgannon and colleagues 1 with interest. In
a recent study involving 12 108 intensive care unit survivors of
cardiac arrest in Australia and New Zealand, 2 we found that the
relationship between hyperoxia and mortality was significantly
altered by the introduction of FIO 2 into the predictive multivariable
model such that PaO 2 was no longer associated with hospital
mortality. Such findings and clinical experience suggest that a high
PaO 2 may thus simply reflect a high FIO 2 . A high FIO 2 would, in turn,
reflect a clinical attempt to compensate for greater physiological
instability. If this were the case, the relationship between higher PaO 2
and greater mortality would simply represent the fact that PaO 2 is a
marker of illness severity instead of a mediator of injury. Accordingly,
we think that the authors should report their analysis after
correction for FIO 2 . Similarly, we found that the APACHE III (Acute
Physiology and Chronic Health Evaluation III) score also significantly
decreased the associated between PaO 2 and mortality. Given
such findings in a large cohort, we similarly suggest that adjustment
for APACHE III score is crucial to any analysis of the relationship
between PaO 2 and mortality. We have checked with colleagues in the
United States, and they have confirmed that such information is
recorded and stored as part of the Project IMPACT database; thus, it
should be available to the investigators. Finally, it would be
important to report how representative of early intervention and
mean oxygenation the PaO 2 values used in the study might have
been. Accordingly, we think the authors should also report how
many blood gas samples were obtained on average in the first 24
hours, as well as the mean time between admission to the intensive
care unit and the peak PaO 2 in their cohort. Such information seems
vital to ensuring that the reported association is scientifically robust.
None.
Disclosures
Rinaldo Bellomo, MD
Michael Bailey, PhD
Alistair Nichol, PhD
Australian and New Zealand Intensive Care Research Centre
School of Public Health and Preventive Medicine
Monash University
Melbourne, Australia
References
1. Kilgannon JH, Jones AE, Parrillo JE, Dellinger P, Milcarek B, Hunter K,
Shapiro NI, Trzeciak S; Emergency Medicine Shock Research Network
(EMShockNet) Investigators. Relationship between supranormal oxygen
tension and outcome after resuscitation from cardiac arrest. Circulation.
2011;123:2717–2722.
2. Bellomo R, Bailey M, Eastwood GM, Nichol A, Pilcher D, Hart GK,
Reade MC, Egi M, Cooper DJ; Study of Oxygen in Critical Care (SOCC)
Group. Arterial hyperoxia and in-hospital mortality after resuscitation
from cardiac arrest. Crit Care. 2011;15:R90.
(Circulation. 2012;125:e288.)
© 2012 American Heart Association, Inc.
Circulation is available at http://circ.ahajournals.org
DOI: 10.1161/CIRCULATIONAHA.111.053611
Downloaded from http://circ.ahajournals.org/ e288 at Ian Potter Library on April 16, 2013