Failure to awaken after general anaesthesia secondary to paradoxical venous embolus

A patient is presented who failed to regain consciousness after an apparently uneventful nine-hour revision of a total hip replacement. There were no clinically important haemodynamic changes during the operation, and oxygen saturation, capnography and acid base balance were normal throughout. Postop CT of the head showed a large left MCA infarct with midline shift. At autopsy, the patient was found to have a previously unsuspected patent foramen ovale, and a venous embolus in the left internal carotid artery, which probably had originated from the periprostatic venous plexus with a large infarct in the distribution of the left anterior and middle cerebral arteries. The authors conclude that massive paradoxical venous emboli can occur during surgery with minimal haemodynamic changes.