Air Embolism during Neurosurgical Operations in the Sitting Position Efficacy of Real-Time Two-Dimensional Echocardiography

When a sitting operation is performed, early detection and prevention of air embolism are important. Air flow into the right heart system was monitored by a real-time two-dimensional echocardiograph in combination with a video-recorder. The heart was observed from the apical four chamber view by a ditector placed under the xiphisternum and directed towards the base of heart. The echocardiography showed two types of air flow; one was the single-bubble type in which several bubbles flowed from the right atrium to the right ventricle, and the other was the stormy-bubble type in which a great number of air bubbles flowed en masse. The single-bubble type was observed during surgery involving the skin, muscle, or bone, and the air flow in this type could be interrupted by electrocoagulation, bone wax, etc. The stormy-bubble type was noted during surgery involving the muscle or dura mater. The air flow from the dura mater was most frequently observed. Retroflexion of the dura mater and then electrocoagulation would be required to prevent the air flow from the cut end of the dura mater. If electrocoagulation does not control the air flow from the cut end of the muscle, massive muscle suture by thick threads could prevent the air flow. Air flow into the right heart system in a sitting operation was more frequent than has previously been believed, and a small amount of air flow was noted even during minor surgery. Therefore, application of a sitting operation should be carefully undertaken. Ultrasonic tomographic monitoring of the heart was useful in the early detection of air embolism because of its non-invasive technique and its high sensitivity.