Comparison of Surgical Approaches in Neurosurgical Patients Experiencing Venous Air Embolism in the Sitting Position

The Editor,

Sir,

Neurosurgery in the sitting position offers advantages for certain posterior fossa operations. However, these approaches are associated with potential complications, particularly venous air embolism (VAE), cerebral and myocardial ischaemia secondary to hypotension, and complications of the positioning itself (1). There is no study comparing the paramedian and median approaches for the risk of VAE. We aimed to find out the incidence of VAE according to the type of the surgical approach as paramedian and median incision.

Records of 73 patients who underwent neurosurgical procedures in the sitting position were reviewed in order to classify the morbidity and mortality related to surgical procedure as well as the clinical appearance of VAE. Patients were assigned into two groups according to the type of the surgical approach as paramedian (Group I, n = 37) and median incision (Group II, n = 36). Before the induction of anaesthesia, routine monitoring was started. End-tidal carbon dioxide (ETC0₂) tension was monitored to diagnose VAE. A sudden and sustained decrease in ETC0₂ of more than 5 mmHg in the absence of sudden hypovolaemia was presumed to be the result of VAE. The incidence of VAE was found to be 37.8% (14 patients) in Group I (paramedian) and 13.9 % (five patients) in Group II [median] (p < 0.05).

Venous air embolism in neurosurgical procedures done in the sitting position is not rare. It depends on the type of surgery and the mode of ventilation. Also, the degree of tilt, intrathoracic and intracardiac pressures (right auricle) and the gas mixtures administered (nitrous oxide increases their size owing to its poor blood solubility) are other components that affect the risk of VAE (2). Venous air embolism, which is one of the perioperative complications in neurosurgery, is not only related to the sitting position but also may be related to the surgical approach. Paramedian surgical approach in the sitting position has a higher risk of VAE episodes which significantly increased the perioperative morbidity. The use of the sitting position should be limited in the neurosurgeon's choice because of the disadvantage of VAE.