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Oxygen consumption following pediatric cardiac surgery
K Puhakka1, J Räsänen, M Leijala
1Department of Anesthesiology, University Children's Hospital, Helsinki, Finland.
Insights
Pediatric patients recovering from heart surgery showed increased oxygen consumption (VO2) during rewarming, but a hypermetabolic state was not universal. Factors like anesthesia and low cardiac output influenced metabolic responses post-operation.
Area of Science:
- Pediatric Cardiac Surgery
- Metabolic Physiology
- Critical Care Medicine
Background:
- Congenital heart defects require complex surgical interventions in pediatric patients.
- Understanding metabolic recovery is crucial for optimizing post-operative care in this vulnerable population.
- Previous studies have not fully elucidated the metabolic response patterns in infants versus older children after cardiac surgery.
Purpose of the Study:
- To investigate and compare metabolic responses, specifically oxygen consumption (VO2) and carbon dioxide production (VCO2), during recovery from cardiac operations in two pediatric age groups.
- To correlate metabolic data with temperature and hemodynamic variables.
- To identify factors influencing metabolic recovery, such as anesthesia and cardiac output.
Main Methods:
- Study included 30 mechanically ventilated pediatric patients undergoing cardiac surgery, divided into infants (≤1 year) and older children (>1 year).
- Metabolic measurements (VO2, VCO2, respiratory quotient) were taken at multiple postoperative time points using a pediatric metabolic monitor.
- Rectal/skin temperatures and hemodynamic variables were recorded concurrently; central venous oxyhemoglobin saturation (ScvO2) was monitored.
Main Results:
- Oxygen consumption (VO2) increased during rewarming (2-4 hours postoperatively) by 12% in infants and 24% in older children, correlating with a rise in rectal temperature.
- No significant further increase in VO2 was observed until the first postoperative morning.
- A hypermetabolic response was inconsistent despite thermal changes; high-dose fentanyl anesthesia and low cardiac output were implicated. Low ScvO2 (<60%) indicated increased oxygen extraction during rewarming.
Conclusions:
- Metabolic recovery after pediatric cardiac surgery is variable, with increased oxygen demand during rewarming, but not universally hypermetabolic.
- High-dose opioid anesthesia and compromised cardiac output can attenuate metabolic responses and affect oxygen delivery.
- Careful monitoring of metabolic status and hemodynamic parameters is essential for managing pediatric patients after complex cardiac operations.
Abstract:
Metabolic responses during recovery from cardiac operations for various congenital heart defects were studied in 30 mechanically ventilated pediatric patients in two groups: infants 1 year or less (group I) and children more than 1 year old (group II). Oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured using a pediatric metabolic monitor intermittently after induction of anesthesia, after skin closure, 2 to 4 hours postoperatively, and on the first postoperative morning in the pediatric intensive care unit. Energy expenditure and respiratory quotient were determined from respiratory gas measurements. Rectal and skin temperatures and hemodynamic variables were recorded at the same time. VO2 increased during rewarming 2 to 4 hours after the operation by 12 +/- 15% in group I and by 24 +/- 19% in group II, while rectal temperature increased by 2.0 +/- 1.2 degrees C and 1.8 +/- 1.4 degrees C, respectively. No further increase in VO2 occurred until the first postoperative morning. A hypermetabolic response was not seen in all cases despite marked thermal changes. High-dose fentanyl anesthesia partly explains the low responses. On the other hand, low cardiac output may also compromise oxygen supply. Sixty-three percent of infants were treated for cardiac failure before surgery and 75% needed inotropic support immediately after the operation. Low central venous oxyhemoglobin saturation values (ScvO2 < 60%) were observed during rewarming, indicating an increase in oxygen extraction secondary to an increased oxygen demand in the brain during recovery from anesthesia, and a low cardiac output or delayed restoration of cerebral blood flow after CPB and deep hypothermia.