Pulmonary air embolism induced during experimental decerebration

¹ Division of Neurology, University of Washington School of Medicine, Seattle, Washington

During experiments employing Sherringtonian decerebration, it was observed that cats which failed to demonstrate the expected postural responses often showed hyperpnea, widened arterial-alveolar CO₂ gradients, and anoxemia. Autopsy revealed air in jugular veins and right heart, as well as heavy lungs. Analysis of surgical procedures revealed that pulmonary air embolism was favored by the following conditions: elevating the head above the thorax during craniotomy, widely removing temporal bone to expose diploic spaces along the tentorial margin, and light anesthesia. Conversely, air embolism was avoided if the head was kept at or below hindquarter level during surgery, bone edges were delicately removed and wax-sealed, care was taken to avoid tearing venous sinuses, and anesthesia was sufficiently deep to prevent gasping. When this latter technique was used, postoperative pulmonary ventilation and blood gases resembled control values. Pulmonary air embolism may explain some of the wide respiratory variations and physiological conditions reported to follow experimental decerebration and other procedures employing extensive craniectomy.