Intravenous fluid loading as prophylaxis for paradoxical air embolism

Paradoxical cerebral air embolism has been described in neurosurgical operations performed on patients in the seated position. This problem is thought to result most often from a probe-patent foramen ovale. It has been postulated that right atrial pressure exceeds left atrial pressure when paradoxical air embolism occurs. A study is described in which intravenous fluid loading is compared with routine fluid management in 20 patients undergoing neurosurgical operations in the seated position. In order to investigate if intravenous fluid loading would decrease the risk of paradoxical air embolism during neurosurgical operations on seated patients, 20 patients were assigned randomly to two groups: 10 patients received normal intravenous fluid replacement (1220 +/- 102 ml), and 10 received augmented fluid replacement (2800 +/- 400 ml). Right atrial and pulmonary capillary pressures were monitored for evidence of an interatrial pressure gradient that would force air emboli from the right atrium into the left atrium via a probe-patent foramen ovale. Four of 10 patients receiving routine fluid administration developed right atrial pressure greater than pulmonary capillary wedge pressure (and hence, indirectly, greater than left atrial pressure), whereas none of the 10 patients with augmented fluid loading developed this condition (p = 0.04). The authors conclude that augmented intravenous fluid loading may be effective in preventing systemic air embolism during neurosurgical operations performed on patients in the seated position.