"He was teaching them about his condition, and about the history of the heart-lung machine in Jefferson's John H. Gibbon Building, where he had worked," said his daughter Linda Swain.
Born in Hazleton, Pa., during the Depression, Dr. Prehatny came from humble beginnings. His parents emigrated from what became Czechoslovakia to America in the early 1900s.
He worked three jobs to put himself through Pennsylvania State University, earning a bachelor of science degree in 1953. He graduated in 1957 from Thomas Jefferson University School of Medicine.
He did an internship in surgery at Methodist and a residency at Jefferson Medical College, and was chief resident at Philadelphia General Hospital. The latter closed in 1977.
Dr. Prehatny was known for his sleight of hand and magic, an expertise that helped him handle delicate instruments in the operating theater.
He also was known for his calm demeanor under pressure. He counseled his trainees: "If patients are bleeding, have broken bones, head trauma, what's the first thing you control? The answer is, yourself."
His patients came from all walks of life. "It was not uncommon for him to perform surgery on a famous athlete, a politician, a Gypsy [free], and an illustrious mob boss, all in one day," his daughter said.
Stuart L. Gordon, orthopedic surgeon at Cooper University Hospital and a former student of Dr. Prehatny's, said he had "a powerful mastery of what doctors need to have and be - ability, wit, compassion, the highest moral character, and, most important, humility."
Dr. Prehatny received many honors, including an award from Drexel College of Medicine for excellence in teaching presented in September 2013.
Dr. Prehatny met his wife, the former Helene Smith, at Penn State. The couple married and moved to Wynnewood, where they raised a family.
Surviving, besides his wife of 58 years, are a son, John R. Jr.; daughters Charlene Ryan, Linda Swain, Lorraine Belprez, and Barbara Rake; 21 grandchildren; three great-grandchildren; and two sisters.
A viewing at 9 a.m. Wednesday, Feb. 5, at Holy Ghost Byzantine Catholic Church, 2310 S. 24th St., Philadelphia 19145, will be followed by a Divine Funeral Liturgy at 11 a.m. Family members will speak at 10:40 a.m. Interment is at noon Thursday, Feb. 6, at Sacred Heart Cemetery, Weston, Pa.
Donations may be made to the church at the address above.