197 - Increased cerebral tissue fractional oxygen extraction with episodes of peripheral arterial desaturation and bradycardia

Poster Number: 197
Publication Number: 197.219

Mohamed A. Mohamed, Cleveland Clinic Children's, Cleveland, OH, United States; Noor Asi, Metrohealth Medical Center, Cleveland, OH, United States; Michael Frasketi, George Washington University School of Public Health, Washington, DC, United States; Safwat Aly, The Hospital for Sick Children, University of Toronto, Old Toronto, ON, Canada; Heather J. Hoffman, The George Washington University, Washington, DC, United States; Hany Aly, Cleveland Clinic Children's Hospital, Cleveland, OH, United States

Background: The capacity for brain tissue to extract oxygen is expected to increase during hypoxia although the relationship between cerebral tissue fractional oxygen extraction (cFTOE) and peripheral arterial oxygen saturation (SaO2) and heart rate (HR) has not been established in premature infants

Objective: To examine the relationship of episodes of increased cFTOE and SaO2 desaturation and bradycardic events in preterm infants

Design/Methods: Infants < 34 weeks gestational age (GA) were monitored with near-infrared spectroscopy (NIRS)  to measure their SctO2 for 1-3 sessions (up to 12 hours each) during the first 28 days of life. The upper limit of normal cFTOE was calculated using a tolerance interval method with 95% confidence interval (CI) for all data points in the sample and was found to be 35.2%. This value was established as the increased cFTOE event threshold. Increased cFTOE events were defined according to the following criteria: 1) a sustained increase of cFTOE above the event threshold for at least 30 seconds, 2) is preceded by a stability period below the event threshold for at least 30 seconds, and 3) followed by a stability period below the event threshold for at least 60 seconds.  Peripheral desaturation and bradycardic events were considered with similar approach based on established lower limits of normal of 85% and 120bpm respectively. Odds ratios (OR) of having increased cFTOE in association with peripheral desaturation or bradycardic events were calculated using logistic regression

Results: Study included 70 preterm infants. Forty two of them were female newborns and 42 where of African American race. Mean BW was 1040 g (±293) and mean GA was 27 4/7 weeks. There were 150 episodes of increased cFTOE, 374 episodes of peripheral desaturations and 79 episodes of bradycardia during the study period. There was no correlation between increased cFTOE events and bradycardic events where both concurrently occurred only in 7 occurrences (4.6% of increased cFTOE and 8.8% of bradycardic events). Mean heart rate increased by 7.5 beats per minute during increased cFTOE episodes (p < 0.001). Similarly, there was no association between episodes of increased cFTOE and peripheral desaturation where both concurrently occurred in 14 occurrences (9.3% out of cerebral desaturations and 3.4% of peripheral desaturations)Conclusion(s): There is no correlation between episodes of increased cFTOE with bradycardic or peripheral desaturation events. Heart rate increased during increased cFTOE episodes. The current definition of oxygen desaturation needs be revisited using available brain monitoring technologies.
Fig 1. An example for an episode of increased eFTOE that were associated with peripheral arterial desaturation.