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Oxygen consumption, energy expenditure, and substrate utilization after cardiac surgery in children
B M Gebara1, M Gelmini, A Sarnaik
1Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit, MI.
Insights
Pediatric cardiac surgery impacts children's substrate utilization, increasing fat oxidation. Resting energy expenditure remains stable, but caloric intake is insufficient post-surgery.
Area of Science:
- Pediatric critical care medicine
- Cardiovascular surgery outcomes
- Metabolic response to critical illness
Background:
- Understanding metabolic changes after pediatric cardiac surgery is crucial for optimizing patient care.
- Indirect calorimetry is a key tool for assessing energy expenditure and substrate utilization in critically ill children.
Purpose of the Study:
- To quantify oxygen consumption (VO2), resting energy expenditure, and substrate utilization in children post-cardiac surgery.
- To compare indirect calorimetry-derived cardiac index with thermodilution measurements.
Main Methods:
- Prospective, observational study involving 26 children within 3 days of open-heart surgery.
- Indirect calorimetry used to measure VO2, resting energy expenditure, and respiratory quotient.
- Cardiac index calculated via Fick equation and compared with thermodilution.
Main Results:
- Accurate VO2 measurements confirmed by excellent correlation between Fick equation and thermodilution cardiac index.
- Resting energy expenditure was consistent with predicted basal metabolic rate.
- Substrate utilization showed a shift towards fat oxidation, with a respiratory quotient of 0.74 +/- 0.05, indicating potential impaired carbohydrate utilization.
Conclusions:
- Pediatric cardiovascular surgery does not significantly alter resting energy expenditure.
- Significant influence on substrate utilization, with a shift towards fat oxidation observed.
- Perioperative stress and catecholamines likely contribute to the observed metabolic shift.
Objective:
To determine the oxygen consumption (VO2), resting energy expenditure, and substrate utilization after cardiac surgery in children.
Design:
Prospective, observational, cross-sectional study with factorial design.
Setting:
Pediatric ICU at a university hospital.
Patients:
Twenty-six consecutive children during the first 3 days after open-heart surgery.
Interventions:
Patients were mechanically ventilated and received routine therapeutic interventions.
Measurements And Main Results:
VO2, resting energy expenditure, and substrate utilization were determined by indirect calorimetry. Cardiac index was calculated using the Fick equation from the measured VO2 and the arterial-mixed venous oxygen content difference, and this cardiac index value was compared with a simultaneous cardiac index value that was measured by thermodilution whenever possible. There were excellent correlation and agreement between cardiac index measurements by Fick equation and thermodilution, indicating accurate VO2 measurements. VO2 was consistent with predicted values in healthy resting children. Resting energy expenditure was consistent with the predicted basal metabolic rate. The mean caloric intake was 19% of the mean energy expenditure. The respiratory quotient was 0.74 +/- 0.05. The substrate utilization showed a shift toward fat oxidation and either gluconeogenesis or impaired carbohydrate utilization.
Conclusions:
Cardiovascular surgery in children does not significantly alter resting energy expenditure but influences the substrate utilization. Perioperative hormonal stress responses and therapeutically administered catecholamines may explain the shift toward fat oxidation.