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Monitoring Gas Exchange During Hypothermia for Hypoxic-Ischemic Encephalopathy

Afzal, Bushra, MD1; Chandrasekharan, Praveen, MD2; Tancredi, Daniel J., PhD3,4; Russell, James, PhD5; Steinhorn, Robin H., MD6; Lakshminrusimha, Satyan, MD3

Pediatric Critical Care Medicine: February 2019 - Volume 20 - Issue 2 - p 166–171
doi: 10.1097/PCC.0000000000001799
Neonatal Intensive Care

Objectives: Therapeutic hypothermia is standard of care in management of moderate/severe hypoxic-ischemic encephalopathy. Persistent pulmonary hypertension of the newborn is associated with hypoxic-ischemic encephalopathy and is exacerbated by hypoxemia and hypercarbia. Gas exchange is assessed by arterial blood gas analysis (with/without correction for body temperature), pulse oximetry, and end-tidal CO2.

Design: A retrospective chart review.

Settings: Regional perinatal center in Western New York.

Patients: Fifty-eight ventilated neonates with indwelling arterial catheter on therapeutic hypothermia.

Intervention: None.

Measurement and Main Results: We compared pulse oximetry, PaO2, end-tidal CO2, and PaCO2 during hypothermia and normothermia in neonates with hypoxic-ischemic encephalopathy using 1,240 arterial blood gases with simultaneously documented pulse oximetry. During hypothermia, pulse oximetry 92–98% was associated with significantly lower temperature-corrected PaO2 (51 mmHg; interquartile range, 43–51) compared with normothermia (71 mmHg; interquartile range, 61–85). Throughout the range of pulse oximetry values, geometric mean PaO2 was about 23% (95% CI, 19–27%) lower during hypothermia compared with normothermia. In contrast, end-tidal CO2 accurately assessed temperature-corrected PaCO2 during normothermia and hypothermia.

Conclusions: Hypothermia shifts oxygen-hemoglobin dissociation curve to the left resulting in lower PaO2 for pulse oximetry. Monitoring oxygenation with arterial blood gas uncorrected for body temperature and pulse oximetry may underestimate hypoxemia in hypoxic-ischemic encephalopathy infants during whole-body hypothermia, while end-tidal CO2 reliably correlates with temperature-corrected PaCO2.

1Newborn Medicine, Department of Pediatrics, Tufts University School of Medicine, Boston, MA.

2Division of Neonatology, Department of Pediatrics, Oishei Children’s Hospital of Buffalo, University at Buffalo, Buffalo, NY.

3Department of Pediatrics, University of California at Davis, Sacramento, CA.

4Center for Healthcare Policy and Research, University of California at Davis, Sacramento, CA.

5Department of Physiology and Biophysics, University at Buffalo, Buffalo, NY.

6Children’s National Health System, Washington, DC.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (http://journals.lww.com/pccmjournal).

Dr. Lakshminrusimha have received funding from a National Institutes of Health grant R01HD072929. The remaining authors have disclosed that they do not have any potential conflicts of interest.

This work was performed at Women and Children’s Hospital of Buffalo, Buffalo, NY.

For information regarding this article, E-mail: bafzal@tuftsmedicalcenter.org

©2019The Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies