Patients go through three main critical periods after craniotomy. These three critical periods are the rebleeding period, the cerebral edema period, and the pulmonary infection period. The rebleeding period occurs mainly within 24 hours after the craniotomy and is usually completed on the morning of the second day of surgery with a cranial CT review to identify any intracranial rebleeding. If there is no rebleeding, the level is passed. The peak of cerebral edema occurs one week after surgery. If the peak period of cerebral edema is successfully passed, the patient will then experience a period of pulmonary infection. If the lung infection is particularly severe and the patient is confused, a tracheotomy may be required if necessary.