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Published on: September 22, 2017
Cerebral oxygenation during cardiopulmonary bypass
S P Wardle1, C W Yoxall, A M Weindling
1Department of Child Health, Royal Liverpool Children's Hospital. s.p.wardle@liverpool.ac.uk
Insights
Cerebral fractional oxygen extraction (FOE) decreased with cooling during cardiopulmonary bypass. Continuous flow bypass allowed FOE to recover during rewarming, unlike circulatory arrest, potentially impacting brain injury timing.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Pediatric Cardiology
Background:
- Cerebral fractional oxygen extraction (FOE) monitoring is crucial during pediatric cardiopulmonary bypass (CPB).
- Understanding the impact of hypothermia and circulatory arrest on cerebral oxygenation is vital for patient outcomes.
- Near-infrared spectroscopy (NIRS) offers a non-invasive method for assessing cerebral hemodynamics.
Purpose of the Study:
- To investigate the effects of profound hypothermia with circulatory arrest versus mild/moderate hypothermia on cerebral FOE in children undergoing CPB.
- To evaluate the changes in cerebral FOE during different stages of CPB, including cooling, cold perfusion, and rewarming.
- To assess the potential correlation between preoperative arterial oxygen content and cerebral FOE.
Main Methods:
- Cerebral FOE was monitored non-invasively using NIRS in 30 children undergoing CPB.
- Children were divided into groups based on hypothermia levels (profound vs. mild/moderate) and CPB strategy (circulatory arrest vs. continuous flow).
- Changes in oxidized cytochrome oxidase concentration were also monitored using NIRS.
Main Results:
- Cerebral FOE decreased during cooling and cold bypass in all groups.
- FOE increased during rewarming only in the continuous flow group; it remained low in the circulatory arrest group.
- No significant differences in cytochrome aa3 changes were observed between groups.
- Preoperative arterial oxygen content showed a negative correlation with mean FOE.
Conclusions:
- Cooling during CPB reduces cerebral FOE, as measured by NIRS.
- Continuous flow bypass facilitates cerebral FOE recovery during rewarming, whereas circulatory arrest does not.
- The sustained low FOE during circulatory arrest may have implications for the timing of hypoxic brain injury in pediatric patients.
Abstract:
Cerebral fractional oxygen extraction (FOE) was monitored in 30 children, using near infrared spectroscopy during cardiopulmonary bypass, to investigate the effect of hypothermia and circulatory arrest. One group of children (n = 15) underwent profound hypothermia with total circulatory arrest (n = 8) or continuous flow (n = 7). Another group (n = 15), of whom only one had circulatory arrest, underwent mild (n = 6) or moderate (n = 9) hypothermia. The mean FOE (SD) before bypass was 0.35 (0.12) and this correlated negatively with the preoperative arterial oxygen content (r = -0.58). Between the stage of cooling on bypass and cold bypass there was a reduction in FOE in all groups. Between cold bypass and rewarming there was an increase in FOE only in the groups with continuous flow. In the circulatory arrest group, the FOE remained low during rewarming and was significantly lower than that of the continuous flow group. No patients died and none had neurological abnormalities postoperatively. Apparent changes in oxidised cytochrome oxidase concentration were also monitored using near infrared spectroscopy. There was a fall in cytochrome aa3 on starting cardiopulmonary bypass, but there were no significant differences in the changes in cytochrome aa3 between any stage in any of the patient groups. Using this non-invasive technique, cooling was shown to reduce cerebral FOE. During rewarming on bypass there was an increase in cerebral FOE only in patients who had had continuous flow bypass. In contrast, the cerebral FOE in those with circulatory arrest remained constant after arrest and during the duration of the study. This may have implications for the timing of hypoxic brain injury.
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