Stability of the intra-operative arterial to end-tidal carbon dioxide partial pressure difference in children with congenital heart disease

Abstract

The purpose of this study was to evaluate the stability of the arterial PCO2 (PaCO2) to end-tidal PCO2 (P etCO2) partial pressure difference (Pa-etCO2) during surgery using PetCO2 monitoring, in children with congenital heart disease (CHD). Forty children with CHD were studied: ten children with no interchamber communication and normal pulmonary blood flow (PBF) (normal group); ten acyanotic children with increased PBF (acyanotic-shunting group); ten cyanotic children with mixing type lesions and normal or increased PBF (mixing group), and ten cyanotic children with right-to-left intracardiac shunts demonstrating decreased and variable PBF (cyanotic-shunting group). Simultaneous PaCO2 recordings and PetCO2 measurements were obtained for each patient during five intraoperative events: (1) control time, arterial line placement under anaesthesia; (2) time 1, patient preparation; (3) time 2, immediately after sternotomy; (4) time 3, after heparin administration; and (5) time 4, immediately after aortic cannulation. Initially, cyanotic children demonstrated a greater Pa-etCO2 compared with acyanotic children (P<0.05). There was no difference in the Pa-etCO2 over time in the control, acyanotic-shunting, or mixing groups. The Pa-etCO2 in the children with cyanotic-shunting lesions at times 2 and 3 was greater (P<0.05) than at their control times. We conclude that the Pa-etCO2 of children with acyanotic-shunting and mixing congenital heart lesions is stable intraoperatively, although patients with mixing congenital heart lesions may demonstrate large individual variations. In children with cyanotic-shunting congenital heart lesions, the Pa-etCO2 is not stable. The PetCO2 cannot be used during surgery to estimate reliably the PaCO2 in children with cyanotic CHD. © 1991 Canadian Anesthesiologists.