Dr. Nazih Zuhdi worked for four years under Drs. Clarence Dennis, Karl Karlson, and Charles Fries, who built an early pump-oxygenator. Zuhdi and Fries worked on several designs and re-designs of Dennis' earlier model from 1952–1956 at the Brooklyn Center. Zuhdi then went to work with Dr. C. Walton Lillehei at the University of Minnesota. Lillehei had designed his own version of a cross-circulation machine, which came to become known as the DeWall-Lillehei heart-lung machine. Zuhdi worked on perfusion and blood flow trying to solve the problem of air bubbles while bypassing the heart so the heart could be stopped for the operation. Zuhdi moved to Oklahoma City, OK, in 1957, and began working at the Oklahoma University College. Zuhdi, the heart surgeon, teamed up with Dr. Allen Greer, a lung surgeon and Dr. John Carey, forming a three man open heart surgery team. With the advent of Dr. Zuhdi's heart-lung machine which was modified in size, being much smaller than the DeWall-Lillehei heart-lung machine, and with other modifications, reduced the need for blood down to a minimal amount, and the cost of the equipment down to $500.00 and also reduced the prep time from two hours to 20 minutes. Dr. Zuhdi performed the first Total Intentional Hemodilution open heart surgery on Terry Gene Nix, age 7, on February 25, 1960, at Mercy Hospital, Oklahoma City, OK. The operation was a success; however, Nix died three years later in 1963. In March, 1961, Zuhdi, Carey, and Greer, performed open heart surgery on a child, age 3½, using the Total Intentional Hemodilution machine, with success. That patient is still alive.

In 1985 Dr. Zuhdi performed Oklahoma's first successful heart transplant on Nancy Rogers at Baptist Hospital. The transplant was successful, but Rogers, a cancer sufferer, died from an infection 54 days after surgery.