Runaway pump head: new cause of gas embolism during cardiopulmonary bypass.

Massive gas embolism was narrowly avoided during a recent case of cardiopulmonary bypass for aortic valve replacement. Cause of the mishap was an arterial pump head that had rapidly accelerated spontaneously, emptying the oxygenator of blood within seconds. No gas entered the patient's vascular system, but a period of circulatory arrest was required in order to purge the extracorporeal circuit of gas and to re-establish blood flow. Only an instantaneous response by the perfusionist prevented massive gas embolism.