[Estimation of size of the uncuffed endotracheal tube for pediatric cardiac anesthesia--Cole's formula cannot estimate the appropriate tube size].

We evaluated the validity of Cole's formula (tube size = 0.25 x age + 4) for the estimation of uncuffed endotracheal tube size, and devised new formula with a statistical method on the basis of the ages of 217 pediatric patients with congenital heart disease. The sizes of the tubes actually used for these patients were 0.5 mm or larger than those estimated by Cole's formula in 29% of patients with congenital heart disease. Only one patient with cyanotic heart disease required a tube that was more than 0.5 mm smaller than that estimated by Cole's formula. The regression formula representing the relationship between the tube size and age was "tube size = 0.316 x age + 4.135". In conclusion, tube size estimated by Cole's formula tends to be smaller than practically appropriate tube size for pediatric cardiac anesthesia, and therefore we suggest new formula to estimate the tube size.