Arterial versus end-tidal carbon dioxide levels in children with congenital heart disease: a prospective cohort study in patients undergoing pulmonary catheterization.

UNLABELLED: Capnography has been the standard in the operating room for a long time now. When variable amounts of intrapulmonary shunt and intracardiac shunt are taken into account, arterial carbon dioxide (CO2) and end-tidal CO2 typically match rather well. The gap between arterial and end-tidal CO2 widens in patients with cardiopulmonary disorders. The current study sought to determine how arterial and end-tidal CO2 correlated with each other and with hemoglobin saturation both before and after pulmonary catheterization in a pediatric population with congenital heart disease.

METHODS: Fifty-seven children with congenital heart disease who underwent cardiopulmonary catheterization between March 2018 and April 2019 were included in a prospective cohort study at Children's Medical Center. Arterial and end-tidal CO2, and hemodynamic variables were assessed prior to the catheterization procedure. Then the patients underwent catheterization, and before being extubated, these variables were again assessed and compared to the baseline levels.

RESULTS: End-tidal CO2 increased significantly in cyanotic patients following the catheterization procedure, and the difference between arterial and end-tidal CO2 decreased significantly. End-tidal CO2, arterial CO2, and their difference did not significantly change in non-cyanotic patients following the catheterization procedure. End-tidal and arterial CO2 were not significantly correlated in cyanotic patients (r=0.411, P=0.128), but they were correlated after the catheterization procedure (r=0.617, P=0.014).

CONCLUSIONS: End-tidal CO2 can estimate arterial CO2 in non-cyanotic patients reasonably. End-tidal CO2 cannot be used to estimate arterial CO2 in cyanotic patients since there is no association. After cardiac defect correction, end-tidal CO2 can be a reliable predictor of arterial CO2.