Our aim was to find out the rate and timing of venous air embolism (VAE), other complications associated with sitting position and changes on arterial blood gas during and after VAE. We analyzed retrospectively files of 124 patients who underwent posterior fossa surgery in department of Neurosurgery of our institute between January 2004 and April 2014. The incidence of emboli was 76,3% in the first 3 hours of the surgery while it was 38.2% in the first 2 hours in total. VAE was seen in a total of 21 patients (16.9%) and it was detected by a sudden drop of minimum 2mmHg of end-tidal CO2 (EtCO2)(25.38 ± 3.28 mmHg) in all cases (100%). The pH, PaO2 and PaCO2 values of the patients with and without emboli were evaluated pre and post-operatively and no significant difference was found (p>0.05). Precordial doppler ultrasonography is the most sensitive non-invasive monitoring device for accurate detection of even small VAE which are not clinically relevant. The most sensitive technique for detection of VAE is transoesophageal echocardiography but it is expensive, invasive and can cause some serious complications. In our study, emboli were most frequently seen in the 3rd hour of the surgery which coincide with tumor resection, thus proposing anaesthesiologists to be more cautious about VAE and EtCO2 during the tumor resection period.
Key words: Sitting position, venous air embolism, cranial surgery, arterial blood gas analysis
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