Abstract 15078: Cerebral Co2 Reactivity is Decreased in Children With Post-Bidirectional Glenn Physiology
Introduction: The Bidirectional Glenn (BDG) procedure converts the patient from a systemic-to-pulmonary arterial shunt to a superior cavo-pulmonary connection. This transition may affect the hemodynamic processes involved in cerebral autoregulation, including cerebral CO2 reactivity, defined as the change of cerebral blood flow (CBF) per unit change of arterial pCO2. Inhaled CO2 acts as a vasodilator in the brain and a vasoconstrictor in the pulmonary bed. Thus, BDG physiology could reduce cerebral CO2 reactivity, which has been associated with both worse neurodevelopmental outcomes and increased mortality at all ages.
Methods: Children with pre-BDG physiology were compared to children with BDG physiology. Subjects were identified from a larger prospective study and studied retrospectively. Under general anesthesia, brain and cardiac MRIs were performed. Arterial spin labeling perfusion MRI sequences were performed to quantify a global average of CBF at baseline and again after 30 minutes of sustained hypercapnia. Arterial blood gases were obtained to confirm pCO2 during each condition. CO2 reactivity was quantified as the percentage change of CBF per mmHg pCO2 increase from baseline to hypercapnia. Only subjects with pCO2 changes greater than 10 mmHg were included in the analysis.
Results: For pre-BDG subjects (n=33), average age (0.53 ± 0.41 years), baseline MAP ( 60 ± 11 mmHg), baseline HR ( 114 ± 14 bpm), baseline pCO2 (41 ± 6 mmHg) and hypercapnia pCO2 (71 ± 11 mmHg) are reported; for BDG subjects (n=39) these values were 3.20 ± 0.83 years, 64 ± 8 mmHg, 104 ± 13 bpm, 39 ± 5 mmHg and 70 ± 12 mmHg, respectively. BDG subjects had a significantly lower CO2 reactivity than pre-BDG subjects (p < 0.05), with a mean CO2 reactivity of 1.66 ± 1.55 (IQR 0.51-3.35) %ΔCBF/mmHg in the pre-BDG group and 0.99 ± 1.52 (IQR 0.09-1.32) %ΔCBF/mmHg in the BDG group.
Conclusion: The unique relationship between the cerebral and pulmonary circulations in BDG physiology results in decreased cerebral CO2 reactivity compared to pre-BDG physiology. This may be due to opposed autoregulatory mechanisms of the brain and lungs when arranged in series - pulmonary vasoconstriction directly competes with cerebral vasodilation during hypercapnia, potentially dampening cerebral CO2 reactivity.
- Congenital heart surgery
- Congenital heart disease
- Perfusion imaging
- Pediatric cardiology
- Cerebrovascular circulation
- © 2013 by American Heart Association, Inc.