Method of randomization and patient selection
esophageal atresia, Azygos vein preservation, Azygos vein disconnection
The sample size was determined before beginning the study. We then prepared 64 nontransparent envelopes, with each envelope containing a card. Out of the 64 envelopes, 32 contained cards signed for “esophageal atresia repair with Azygos vein preservation” and the other 32 envelopes contained cards signed for “esophageal atresia repair with Azygos vein disconnection.” All envelopes were closed and mixed. Each patient came one by one, and each patient's parent blindly chose one of the closed envelopes. The surgical committee opened the envelopes to determine the chosen technique. This method is called the permuted block design, and it is used to ensure that both groups in the current study have equal and balanced numbers.