Massive air embolism during cardiopulmonary bypass. Causes, prevention, and management.

Massive air embolism during cardiopulmonary bypass is a frightening complication requiring immediate response and carrying strong medicolegal implications. From July, 1971, to July, 1979, there were eight instances of massive air embolism during 3,620 cardiopulmonary bypass operations. Five such accidents from other institutions are included in this report. Causes were (1) inattention to reservoir level, (2) reversal of pump head tubing or direction of pump head rotation, (3) unexpected resumption of heartbeat, (4) inadequate steps to remove air after cardiotomy, (5) high-flow suction deep in a pulmonary artery, (6) defective oxygenator, (7) use of a pressurized cardiotomy reservoir, and (8) inadvertent detachment of oxygenator during bypass. Prevention includes a systematic check of pump suckers and perfusion lines before bypass, a sensing device on the oxygenator reservoir, secure fixation of the oxygenator and avoidance of traffic around pump equipment, immediate cessation of pump and inspection for abnormal noise, use of standard maneuvers to remove air from the heart, and carotid compression with resumption of heartbeat. Immediate management of massive air embolism consists of placing the patient in a deep Trendelenburg position and making a large stab wound in the ascending aorta for retrograde drainage from the cerebrovascular bed. Temporary retrograde perfusion through the superior vena cava (SVC) may also be used. Subsequent steps are hypothermia with the resumption of cardiopulmonary bypass, elevation of blood pressure, steroids, ventilation with 100% oxygen, and deep barbiturate anesthesia. Among the 13 patients, there were four instantaneous deaths. Cerebral injury which resolved within a 2 month period occurred in three patients. The remainder had no neurologic sequelae. Nonfatal cerebral air injury may be associated with prolonged convalescence yet complete recovery, as compared to embolism from debris or clot, which offers a poorer prognosis.