Another important contribution by Macewen to modern surgery was the technique of endotracheal anaesthesia with the help of orotracheal intubation, which he described in 1880, and still in use today.

The hospital had been established for the treatment of facial injuries sustained in World War I. Working with plastic surgeon Harold Gillies, he was responsible for the development of numerous items of anaesthetic equipment but most particularly the single-tube technique of endotracheal anaesthesia.

Whenever possible, patients with HPS may benefit from general endotracheal anesthesia.

He had started the temporal lobectomy as soon as Ranade had inducted Lisa under general endotracheal anesthesia.

Beginning in the 1940s under the surgical leadership of C. Everett Koop, newer techniques for endotracheal anesthesia of infants allowed surgical repair of previously untreatable birth defects.

That, coupled with many new discoveries at Mount Sinai (including significant advances in blood transfusions and the first endotracheal anesthesia apparatus), meant that Mount Sinai's pool of doctors and experts was in increasing demand.