Other patients would require a slightly higher or lower concentration to achieve the same effect, but the variations were not large.
That led to their introduction in 1965 of a concept, called the minimum alveolar concentration, or MAC, that quickly became the standard measure of potency for anesthetic gases.
Because powerful anesthetics work at lower concentrations and weaker ones require higher doses, a lower MAC value would indicate a stronger drug. Anesthesiologists use MAC values when planning doses needed for surgery.
The values are highly consistent from one patient to another and even among animals. For any given drug, about the same concentration can anesthetize a 200-pound man, a smaller woman, a dog or a rat. The amount needed to reach that concentration differs depending on the patient’s size, but the effective concentration itself does not change.
Dr. Shafer said the technique devised by Dr. Eger and his colleagues made the administering of anesthesia far safer and has saved millions of lives.
In later work, Dr. Eger identified new drugs that could be used as anesthesia, such as isoflurane, sevoflurane and desflurane, which are still the most widely used general anesthetics.
“Ted Eger revolutionized modern anesthetic practice, and led the way to the development of the anesthetic gases used tens of millions of times a year,” Dr. Michael A. Gropper, the chairman of the department of anesthesia and perioperative care at the University of California, San Francisco, wrote in an email.
Edmond I. Eger II was born on Sept. 3, 1930, in Chicago. (His parents gave him a middle initial but not a middle name.) His father was an advertising executive, and his mother, the former Miriam Newmann, was a homemaker.
As a boy, Dr. Eger skipped at least one grade, became a whiz at checkers and led the Hyde Park High School checker team to two city championships. He graduated at 15, but, as a bored and indifferent student, wound up in the bottom 20 percent of the class.
He was soon hired to sell women’s shoes, but after only one day on the job he decided he had had enough and resolved to apply for college. He was accepted at Roosevelt College in Chicago, where “he went from not working at all to working his butt off,” Dr. Shafer said.
After a year, he…