Regional generation of free oxygen radicals during cardiopulmonary bypass in children
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E J Pesonen1, R Korpela, K Peltola
1Children's Hospital, University of Helsinki, Finland.
Insights
Cardiopulmonary bypass generates free radicals and activates granulocytes primarily in the lower body circulation, not the heart or lungs. This study highlights regional differences in bypass-induced oxidative stress and inflammation.
Area of Science:
- Cardiovascular Surgery
- Physiology
- Biochemistry
Background:
- Cardiopulmonary bypass (CPB) can induce systemic oxidative stress and inflammation.
- Previous studies focused on heart and lung effects, neglecting other circulatory regions.
- CPB's non-physiological conditions may impact splanchnic circulation and gut permeability.
Purpose of the Study:
- To investigate regional free radical production and granulocyte activation during CPB.
- To assess hypoxanthine metabolism in different circulatory compartments during CPB.
- To differentiate CPB-induced changes in the superior vena cava (SVC) and inferior vena cava (IVC) circulations.
Main Methods:
- Studied 16 pediatric patients undergoing CPB.
- Measured malondialdehyde, lactoferrin, myeloperoxidase, hypoxanthine, and urate levels.
- Compared levels in IVC, SVC, and arterial line samples at different time points and temperatures.
Main Results:
- Significant increases in malondialdehyde, lactoferrin, and myeloperoxidase were observed in the IVC circulation.
- Hypoxanthine elimination and urate production were higher in the IVC circulation.
- These gradients diminished with decreasing body temperature; SVC showed minimal changes except transient malondialdehyde.
- Granulocyte activation in the oxygenator occurred only after aortic declamping.
Conclusions:
- CPB induces significant free radical generation and granulocyte activation in the IVC-drained region.
- Hypoxanthine elimination and urate production are also localized to the IVC circulation during CPB.
- Oxygenator-related granulocyte activation is a post-declamping event.
Abstract:
Studies on free radical generation during cardiopulmonary bypass have focused mainly on the heart and the lungs. However, low pumping pressure, nonpulsatile perfusion, and hypothermia affect the entire circulation, resulting in decreased splanchnic blood flow, increased intestinal permeability, and endotoxemia. To evaluate regional phenomena, we studied 16 children undergoing cardiopulmonary bypass. Free radical production, granulocyte activation, and hypoxanthine metabolism were assessed separately in the circulations drained by the inferior and superior venae cavae, as well as in the oxygenator. Three minutes after the onset of cardiopulmonary bypass, significant gradients between the inferior vena cava and the arterial line of the oxygenator existed in malondialdehyde (+0.60 +/- 0.12 mumol/L, lactoferrin (+18.21 +/- 7.65 micrograms/L), myeloperoxidase (+53.75 +/- 16.50 micrograms/L), hypoxanthine (-0.62 +/- 0.15 mumol/L), and urate (+8.87 +/- 4.03 mumol/L). These gradients decreased in parallel with decreasing body temperature. Except for a transient gradient in malondialdehyde at 3 minutes after the onset of cardiopulmonary bypass (+0.23 +/- 0.08 mumol/L), no changes were detected between the superior vena cava and the arterial line. In the oxygenator, granulocyte activation was observed only after aortic declamping. We conclude that during cardiopulmonary bypass, significant free radical generation, granulocyte activation, hypoxanthine elimination, and urate production take place in the region drained by the inferior vena cava. In the oxygenator, granulocyte activation occurs only after aortic declamping.