Air embolism due to the Mayfield skull clamp

During posterior craniotomy of a 77 years old man in the sitting position air embolism was monitored and reoccurred not withstanding proper measures. Only at the end of the operation the source was discovered: when the head was removed from the Mayfield skull clamp the embolism reoccurred once more. All this not withstanding the meticulous treatment of the three points of the head holder with antibacterial ointment, in the beginning.