Delirium is a sudden, severe change in mental state, marked by confusion and a reduced ability to focus and maintain attention. It develops rapidly, and its severity can fluctuate throughout the day. This condition is a common complication after surgery, particularly in older adults, with prevalence rates ranging from 5% to 50% depending on the surgical context. Delirium is often a temporary state that usually resolves within one to three days, though it can sometimes persist longer.
Patient Vulnerabilities
Advanced age is a risk factor for developing postoperative delirium, with individuals over 65 years having a prevalence above 30%, and those over 80 years showing rates between 33.5% and 50%. The aging brain has reduced cognitive reserve, making it more susceptible to stressors like surgery and anesthesia. This decreased resilience means that even minor disruptions can trigger confusion.
Pre-existing cognitive impairment, such as dementia or mild cognitive impairment, increases the risk of delirium. Patients with undiagnosed cognitive issues are also more vulnerable, as their baseline mental function may already be compromised. These impairments reduce the brain’s ability to cope with the physiological stress of surgery.
Chronic health conditions increase susceptibility to delirium. Conditions like heart disease, lung disease, kidney disease, diabetes, and neurological disorders (e.g., previous stroke) often lead to systemic inflammation and reduced organ function, which can impact brain health.
Taking multiple medications elevates the risk. Certain drug classes, including sedatives, anticholinergics, and benzodiazepines, are implicated in inducing or worsening delirium. The interaction of these medications can have a cumulative effect on cognitive function. Substance use, especially alcohol or drug dependence and withdrawal, can also trigger delirium.
Overall physical weakness (frailty) and poor nutritional status contribute to delirium risk. Frail patients often have diminished physiological reserves, making them less resilient to the stress of surgery. Malnutrition can lead to electrolyte imbalances and a weakened immune system, increasing the risk of delirium.
Surgical and Anesthetic Influences
The type of surgical procedure influences the risk of postoperative delirium. Orthopedic surgeries, particularly hip fracture repair, cardiac surgeries, and vascular surgeries, are associated with higher rates due to their invasiveness, longer duration, and the physiological stress they impose on the body. Emergency surgeries also carry a higher risk compared to elective procedures.
The choice and duration of anesthesia are contributors to delirium risk. General anesthesia, especially when administered for longer periods, has been linked to an increased likelihood of delirium. Some anesthetic agents can temporarily alter neurotransmitter balance in the brain.
Complications that arise during surgery can exacerbate the risk. Blood loss, which can lead to reduced oxygen delivery to the brain, is an intraoperative factor. Fluctuations in blood pressure (hypotension or hypertension) and hypothermia (low body temperature) during the procedure can also negatively impact cerebral autoregulation, contributing to postoperative confusion.
Effective pain management after surgery is important, as both inadequate pain control and the use of certain pain medications can influence delirium. Uncontrolled pain itself can be a stressor that contributes to confusion. Conversely, specific pain relievers, such as opioids, are known to have central nervous system effects that can induce or worsen delirium. Balancing pain relief with minimizing delirium risk requires careful consideration of medication type and dosage.
Postoperative Body and Environment Changes
The body’s natural inflammatory response to surgical trauma can trigger delirium. Surgical procedures initiate a systemic inflammatory cascade, and if an infection develops postoperatively, this inflammation can become more pronounced. Inflammatory mediators can cross the blood-brain barrier, affecting brain function and neurotransmitter systems.
Physiological imbalances are common after surgery and contribute to confusion. Electrolyte disturbances, such as abnormal levels of sodium or potassium, can disrupt normal brain cell function. Dehydration, low oxygen levels (hypoxia), and fluctuations in blood sugar can also impair cognitive processes. These imbalances collectively stress the brain, making it more vulnerable to delirium.
Sleep deprivation and disrupted sleep-wake cycles are factors in the hospital setting. The unfamiliar environment, pain, frequent vital sign checks, and administration of medications can interrupt natural sleep patterns. This lack of restorative sleep can impair cognitive function and contribute to delirium.
Sensory changes in the hospital environment can disorient patients. Sensory deprivation, caused by a lack of familiar cues like personal belongings or natural light, can lead to confusion. Conversely, sensory overload, particularly in intensive care units, can overwhelm patients and worsen disorientation.
Common postoperative issues like urinary retention and constipation can cause discomfort and contribute to a patient’s distress, which may manifest as confusion. These physical discomforts add to the physiological burden on the patient, contributing to delirium.
Certain medications administered postoperatively can induce or worsen delirium. Opioids, commonly used for pain control, can have sedating and disorienting effects. Benzodiazepines, often used for anxiety or sleep, and anticholinergic medications can also impair cognitive function and increase confusion.