Postoperative neurologic complications are very uncommon but can be devastating in some circumstances. Neurologic complications after anesthesia can range from delirium, postoperative cognitive decline, to delayed emergence due to other factors such as residual anesthesia or rarely postoperative stroke. Most neurologic complications postoperatively occur in the elderly population and may also vary based on length of surgery, extent of surgery, and perioperative complications. There are many different risk factors for each type of complication and this will be discussed more thoroughly below.
The most likely postoperative complication in a geriatric patient is postoperative delirium. It can occur at any age and has an incidence of about 5%–52% in patients undergoing noncardiac surgery. However, it is more likely to affect the geriatric population. Also, the incidence of postoperative delirium is dependent on the type of surgery. For example, hip fracture surgery has a higher rate of delirium, likely due to the fact that most of those procedures are emergent or urgent and the patients usually have some comorbidity. Postoperative delirium usually happens in the first few days after surgery and may even start when the patient is recovering in the PACU. It consists of acute confusion with waxing and waning consciousness and affects patients’ memory, orientation, and perception. Postoperative delirium varies throughout the day and can have some symptoms of psychosis and interruption of sleep-wake cycle as well.
There are two different manifestations of postoperative delirium: hyperactive and hypoactive. Hypoactive is what occurs most often and is also associated with a worse prognosis. These patients can be mistaken to have other psychiatric conditions such as depression or dementia. Hyperactive is diagnosed more easily because these patients can cause interference in their medical care. On the other hand, hypoactive delirium may go unnoticed because the patient will participate in their care but then fall asleep when the physician is not present.
There are many risk factors that predispose patients to having postoperative delirium. These factors include their age, baseline cognitive dysfunction, limited functional capacity, abnormal laboratory values, alcohol abuse, or major type of surgery that is either thoracic or open aortic.
The main abnormal laboratory values that serve as risk factors for delirium are glucose, sodium, potassium, and albumin. Low albumin is of utmost importance because it can be associated with malnutrition and increased mortality perioperatively.
Due to increased morbidity in those that develop delirium, it is important to screen for delirium daily, especially in those at high risk. One such standardized tool to screen for delirium is known as the Confusion Assessment Method (CAM). CAM assesses the patient in four different areas: acute onset or fluctuating in nature, inattention, disorganized thinking, and altered level of consciousness (see Figure 121-1). This same diagnostic tool was altered to create CAM ICU to assess nonverbal ICU patients.