tcPO2 in pediatric cardiology: application during balloon septostomy, tolazoline administration, and in children with right-to-left shunt.

In pediatric cardiology tcPO2 is useful in monitoring cyanotic children given high-risk therapy such as balloon septostomy or drugs with controversial effects such as tolazoline in persistent fetal circulation. tcPO2 during administration of 100% oxygen enables a rapid, noninvasive differentiation between cyanosis due to intracardiac right-to-left shunt and that due to low cardiac output or pulmonary ventilation or diffusion difficulty. The size of the right-to-left shunt can be roughly estimated from the highest value of tcPO2, this estimation being influenced by anemia, hypothermia, and acidosis, among other factors. A trend of the tcPO2 rise is evident 90 seconds after the beginning of oxygen breathing. If tcPO2 does not rise at least 40 mm Hg over the initial value, a significant right-to-left shunt must be suspected. Interpretation of tcPO2 rise is difficult in dynamic right-to-left shunt, changing with oxygen breathing.