Incidence of Venous Air Embolism during Cesarean Section Is Unchanged by the Use of a 5 to 10?? Head-Up Tilt

Abstract

One hundred healthy parturients were divided at random into two demographically similar groups and were positioned for cesarean section either horizontally or flexed 5 to 10° head up, with a 15° lateral tilt. A Doppler ultrasound transducer was positioned over the fourth intercostal space parasternally. Initially, two patients received spinal, three general, and 95 epidural anesthesia. Two patients subsequently needed general for failed epidural anesthesia. Changes in Doppler heart tones (>15 sec duration) indicative of venous air embolism (VAE) were identified 15 times in 11 patients—seven in supine and four in head-up patients (no statistically significant diference). Six awake patients (three horizontal, three head-up) developed chest tightness or pain during surgery, but only one episode correlated with VAE. No patient developed breathlessness. Moderate hypotension (>lo% decrease in systolic arterial pressure [SAP]) occurred in seven of 11 (63.6%) patients with, and in 26 (29.2′%) of 89 patients without, VAE (P < 0.001). More severe hypotension (SAP <90 mm Hg) due to bleeding occurred once. We conclude that a modest (5–10°) head-up position does not influence the occurrence of VAE in patients having cesarean section. An 21% incidence of clinically insignificant VAE, although low, is still worrisome, as even small air bubbles in the circulation are potentially harmful, especially if the foramen ovule is patent. VAE during cesarean section should be anticipated and the anesthetic management planned accordingly.