John Webster Kirklin (April 5, 1917 – April 21, 2004) was an American cardiothoracic surgeon, general surgeon, prolific author and medical educator who is best remembered for refining John Gibbon's heart–lung bypass machine via a pump-oxygenator to make feasible under direct vision, routine open-heart surgery and repairs of some congenital heart defects.

After completing his undergraduate education at the University of Minnesota, Kirklin gained admission to Harvard Medical School from where he graduated in 1942.

He was a neurosurgeon during the Second World War, but later, after being appointed to the Mayo Clinic in 1950, specialised in the surgical treatment of congenital heart disease.

From 1964 he led the surgical departments at the Mayo Clinic and from 1966 until retirement, held the same position at the University of Alabama School of Medicine (UAB).

[4] In 1944, Kirklin began service with the United States Army with the rank of captain[8] and undertook neurosurgical training at O'Reilly General Hospital in Missouri.

[9] In 1952, F. John Lewis, at the University of Minnesota, used deep hypothermic circulatory arrest to visualize and directly close an atrial septal defect (ASD) in a five-year-old girl.

[10] In the same year, Kirklin formed a team of specialists including a cardiologist, a physiologist and an engineer to advance a cardiac surgical programme for the clinical application of a mechanical pump-oxygenator.

[11][12][13] In 1954, Kirklin's rival, C. Walton Lillehei used the technique of cross circulation to operate on an 11-month-old baby who died on the 11th day after surgery.

Usually using the parent for cross circulation, he performed 45 operations of ventricular septal defects (VSDs), ASDs and tetralogy of Fallot.

During the 1950s and 1960s, the trend for ambitious trainee cardiac surgeons was to fly to Minneapolis to observe Lillehei and subsequently travel to the Mayo Clinic to then watch Kirklin.

[11][16] In 1961, Italian surgical trainee Giancarlo Rastelli received a North Atlantic Treaty Organization (NATO) scholarship and entered into a fellowship under Kirklin's guidance.

[17] After years as the chair of the Department of Surgery at the Mayo Clinic, Kirklin accepted the same position at the University of Alabama School of Medicine in 1966,[7] succeeding Champ Lyons.

[7][11][18] In addition, Kirklin developed the use of technology for continuous monitoring of vital functions in the intensive care unit.