[Air embolism in neurosurgery. General data (author's transl)].

Air embolism in neurosurgery, in the sitting position, are not rare. They depend on the type of surgery (more frequent in operations on the posterior fossa), on the mode of ventilation, and most of all on the criteria for detection (clinical, electrocardiographic, ultrasonic, capnographic of haemodynamia). They depend as well upon the degree of tilt, of intrathoracic and intracardiac pressures (right auricle) and of the gas mixture administered (nitrous oxide increases their size owing to its poor blood solubility). The way of entry is venous, but it is certain that they can pass into the systemic circulation (their passage through the lungs is debated). According to their size, the speed of injection and the subject's previous condition they may affect: --the lungs: precapillary pulmonary artery hypertension, and even pulmonary oedema, --the heart, mainly through the fall of venous return, --the brain anoxia, followed by cerebral oedema, leading to early neurologic disturbances and possibly severe sequellae. Those symptoms are due to the gas embolism itself, but also to microthrombi of fibrin and disturbances of vascular membrane permeability.