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Changes in cerebral hemodynamics and oxygenation during hypothermic cardiopulmonary bypass in neonates and infants
F Van Bel1, P E Zeeuwe, C A Dorrepaal
1Department of Pediatrics Division of Neonatology, University Hospital Leiden, The Netherlands.
Insights
Cardiopulmonary bypass (CPB) in infants undergoing heart surgery affects brain blood volume and oxygenation. Deep hypothermia impacts cerebral blood flow, potentially compromising brain cell energy metabolism, especially during circulatory arrest.
Area of Science:
- Pediatric Cardiology
- Neuroscience
- Biomedical Engineering
Background:
- Infant developmental delays after open-heart surgery are common.
- Inadequate brain perfusion and oxygenation during deep hypothermic cardiopulmonary bypass (CPB) are suspected causes.
Purpose of the Study:
- To investigate the effects of CPB on cerebral perfusion and oxygenation in infants undergoing open-heart surgery.
- To analyze the relationship between CPB parameters and brain physiological changes.
Main Methods:
- Near-infrared spectroscopy (NIRS) was used to measure changes in cerebral blood volume (delta CBV) and cytochrome aa3 oxidation (delta Cytaa3).
- Nasopharyngeal temperature (Tnas) and mean arterial blood pressure (MAP) were continuously monitored in 12 infants (0-11 months).
Main Results:
- CBV changes correlated with Tnas during cooling and rewarming, but not MAP or pump flow.
- During steady-state hypothermic CPB, CBV changes were linked to MAP, indicating impaired cerebral autoregulation.
- A significant decrease in delta Cytaa3 was observed in patients experiencing circulatory arrest, suggesting compromised brain cell energy metabolism.
Conclusions:
- CPB-induced changes in infant cerebral blood volume are primarily related to changes in brain temperature.
- Impaired cerebral autoregulation occurs during deep hypothermic CPB.
- Circulatory arrest during CPB can severely compromise brain cell energy metabolism in infants.
Abstract:
Delay in development after open-heart surgery in infants has frequently been reported. Inadequate brain perfusion and oxygenation during deep hypothermic cardiopulmonary bypass (CPB) may play an important role. We investigated the effect of CPB on cerebral perfusion and oxygenation in 12 neonates and infants (age 0-11 months) undergoing open-heart surgery. Changes in cerebral blood volume (delta CBV; in ml/100 g brain tissue) and oxidation level of the intracerebral mitochondrial enzyme cytochrome aa3 (delta Cytaa3; in mumol/l) were measured with near infrared spectroscopy. Nasopharyngeal temperature (Tnas) for assessment of changes in brain temperature, and mean arterial blood pressure (MAP) were monitored continuously. CBV lowered during cooling and increased during rewarming. These changes were only related with changes in Tnas (p < 0.001; 0.07 ml.100 g-1/ degrees C). No relation was found with changes in MAP or pump flow rate of the heart-lung machine. During steady-state hypothermic CPB, changes in CBV were only related to changes in MAP (p < 0.001). The individual regression lines between delta CBV and MAP became steeper at lower absolute Tnas. Cytaa3 showed an increase shortly after the initiation of CPB in 9 patients, with a sustained decrease to baseline values in 8 patients towards the end of the CPB period. Two patients who had a circulatory arrest during CPB had a sharp decrease in delta cytaa3 after cessation of the heart-lung pump and showed no complete recovery of delta Cytaa3 to baseline at the end of the CPB period. We conclude that changes in CBV during CPB are related to changes in Tnas. During deep hypothermic steady-state CPB, changes in CBV and MAP were related to each other, suggesting lack of cerebral autoregulation. The large decrease in Cytaa3 in 2 patients with circulatory arrest suggests that this procedure compromises energy metabolism of the brain cell.