To confirm the incidence of venous air embolism (VAE), we simultaneously monitored expired nitrogen concentration (FEN2) and precordial Doppler in 30 patients undergoing cesarean delivery during general anesthesia. Patients were randomized into two groups and the effect of a 10 degrees reverse Trendelenburg tilt versus the horizontal position was evaluated. Forty-two episodes of VAE, defined by an increase in FEN2 of 0.1%, were detected in 97% (29/30) of patients. Doppler ultrasound failed to detect 9 of the episodes and 23 (41%) changes in Doppler tones were not associated with an increase in FEN2. These spurious Doppler signals were synchronous with compression of retroperitoneal structures, suggesting turbulent venous return to be the cause. The reverse Trendelenburg position did not reduce the incidence of VAE. Compared with the preinduction baseline, mean arterial blood pressure decreased by 31.5 +/- 10.1 mm Hg in this position and 22.6 +/- 13.4 mm Hg in the supine position after hysterotomy. We conclude that VAE in cesarean delivery during general anesthesia occurs very frequently, and that changes in Doppler tones may not be reliable indicators of this complication. Measures to reduce the size and effect of air emboli therefore should be applied routinely in all patients.
Laryngeal mask assisted blind orotracheal intubation is a technique that is best mastered under controlled circumstances. The influence of the type of tracheal tube, and positioning of the head, on the success rate of this procedure was evaluated in 90 gynaecological patients presenting for elective procedures under general anaesthesia. After induction, a laryngeal mask was introduced and its position was confirmed. Up to three attempts at blind orotracheal intubation using one of three tracheal tubes (Argyle, Portex or Kendall Curity) passed through the laryngeal mask were permitted in each patient. The success rates after a single attempt at blind oral intubation were 3.3%, 70.0% and 30.0% respectively ( p < 0.001 and p < 0.05
when Portex was compared to Argyle and Kendall Curity types). After a maximum of three attempts, success rates were 30.0% (Argyle), 93.3% ( Portex) and 76.7% (Kendall Curity). The first attempt at tracheal intubation was performed in the 'snifing the morning air position' and this was successful in 52% of successful intubations; the second attempt using extension at the atlanto-occipital joint was successful in a further 35% of successful intubations; the third attempt used varying degrees of neck JIexion and extension at the atlanto-occipital joint and this permitted successful placement of the tracheal tube in the remaining 13% of patients in whom tracheal intubation was possible.
The quality of analgesia in all subjects in the study was excellent. Side effects were more common in the i.t. sufentanil-bupivacaine combination group.
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