“The third and most controversial technique was called "cross circulation." In this procedure, Lillehei tapped the circulation from the large vessels of a healthy partner whose normal heart was strong enough to be put "on loan" to support the circulation needs of a sick patient while the patient's heart was opened and repaired. From the observation dome of the human operating room, we witnessed a tragedy during an attempt at cross circulation. The healthy member of the connected pair was accidentally given a large amount of intravenous air from a bottle that had been internally pressurized to increase the rate of fluid infusion. No one had noticed when the bottle became empty of its solution. Moments later, the previously healthy cross-circulation partner who had been pumped full of air had a heart stoppage. Although heart massage was successful, I learned later that the healthy patient had suffered permanent brain injury and ultimately died.”