Dr. David O'Neal said it was just another casualty at the time, but one wrong move might have ended his life and that of his patient.
The retired Chattanooga physician was the chief of orthopedic surgery aboard the USS Repose, moored at Da Nang, South Vietnam, when the incident occurred in 1969.
The 14-year-old South Vietnamese boy who was brought aboard had a live gas canister buried in his thigh, between two parts of a shattered femur, after absorbing what was thought to be a warning shot by a Marine guard.
"The case [of the canister] had developed a leak," Mr. O'Neal, 77, said, "and I smelled it. I knew what it was, so I mobilized the [operating room] crew."
He said if the gas canister had exploded, it would have done as much damage as a fragmentation weapon. He said the ship's captain was so concerned about an explosion that he rigged up a metal shield in front of the anesthesiologist.
Mr. O'Neal had no shield in front of him but said he didn't blink at the potential for injury.
"At the time," he said, "you get this attitude, if you will, that you're taking care of what comes along. You say, here's the problem, let's fix it. We had had so many casualties, this was just the next in line."
Thomas A. Schwartz, a professor of history at Vanderbilt University and an expert on the Vietnam War, said doctors were able to save the lives of more people in the conflict than in previous wars because evacuation by helicopter of casualties to treatment was much more rapid.
"A lot of men were saved," he said. Doctors could take "a sense of satisfaction from that."
The surgery on the boy, Mr. O'Neal said, involved clamping off the bone portions above and below the explosive. Next, the demolition expert pulled out the canister, secured it in a metal box and left.
"I didn't touch the thing," he said. "That's the last I saw of it."
Mr. O'Neal set the broken leg, but he never saw the boy again after the young man was transferred from the ship to a hospital on shore.
Operating on Vietnamese citizens was not uncommon aboard the ship, where, Mr. O'Neal said, some days there was little to do and other days he was covered up.
Mr. O'Neal said in addition to U.S. soldiers, he operated on Vietnamese civilians, Vietnamese nationals and even enemy Viet Cong.
"We didn't pay any attention," he said. "We didn't know who was who."
Schwartz said there was a powerful sentiment among medical personnel during the war that people - regardless of nationality - would be treated as wounded. He said there are even stories of Viet Cong soldiers who defected because of how well they were treated.
"The medical care given was first-rate," he said. "That was one of the hallmarks of the attempt to win hearts and minds."
Mr. O'Neal said the 30 doctors aboard the USS Repose represented a wide variety of specialties and, in addition to military personnel, also treated civilian children with routine conditions such as post-polio syndrome or club feet, children whose fathers had political clout in their villages and elderly who needed special care.
"A lot [of people] don't know we did that," O'Neal said.
"There are a lot of Vietnamese alive who wouldn't have been alive [without the doctors]," Schwartz said.
The USS Repose, before returning to its home port of Alameda, Calif., on April 30, 1970, according to www.ussrepose.org, admitted more than 24,000 patients, including more than 9,000 battle casualties, performed nearly 8,000 surgical operations, and saw more than 16,000 consecutive safe helicopter landings.