Cardiac catheters for diagnosis and treatment of venous air embolism. A prospective study in man

One hundred consecutive patients undergoing neurosurgical procedures in the seated position were monitored for venous air embolism with a Swan-Ganz pulmonary artery (PA) catheter, precordial Doppler ultrasound device, and continous end-trial CO₂ (FET(CO₂)) analysis. Simultaneous determinations of right atrial and pulmonary capillary wedge pressure were also performed during each operation. Although 80 episodes of air embolism were detected by changes in Doppler sounds only 36 were associated with increased PA pressure, and only 30 developed a decrease in FET(CO₂). Changes in PA pressure and FET(CO₂), agreed closely (r=0.86), and only marked changes were associated with systemic arterial hypotension. Air was recovered from the right atrium and PA only in small amounts (2 to 20 ml) during air embolism, although it was possible to aspirate large quantities of blood. Twenty-nine patients were found to have right atrial pressures that were higher than pulmonary capillary wedge pressure. Paradoxical air embolism from a probe-patent formation ovale was possible in these patients, and one developed signs and symptoms of systemic air embolism postoperatively. We conclude that noninvasive monitoring with the combination of a precordial Doppler device and end-trial CO₂ analysis is satisfactory for rapid detection of clinically significant venous air embolism. The unique advantage of Swan-Ganz monitoring, however, is that it permits identification of patients who may sustain paradoxical air embolism, and that it differentiates the hemodynamics effects of brain-stem manipulation from those caused by air embolism.