A dictionary defines delirium as a temporary state of mental confusion resulting from high fever, intoxication, shock or other causes, and characterized by anxiety, disorientation, memory impairment, hallucinations, trembling and incoherent speech.
Delirium after surgery under general anaesthetic is common in the elderly. Approximately half of all operations performed in North America are in patients greater than 65 years of age. This number is expected to increase as the population of elderly increases. Older adults represent a unique challenge to the surgeon, often presenting with multiple medical illnesses and higher risk for post-surgical complications, says an article in the Journal of the American College of Surgeons (JACS).
The incidence of delirium in various studies varies from nine per cent to 87 per cent. The development of delirium is associated with increased death rate, increased length of stay in the hospital and an increased rate of discharge to long term care facilities. Delirium is also associated with increased risk of major medical complications including heart attack, build up of fluid in the lungs, pneumonia, and respiratory failure.
Studies have also found that post-surgical delirium predicts future cognitive (mental processes of perception, memory, judgment and reasoning) decline and an increased risk of dementia. Delirium is not always easy to recognize and may be confused with other conditions common among the elderly such as dementia or depression.
Delirium is a complex phenomenon, often involving multiple factors to trigger the problem and likely affecting multiple spheres of the central nervous system. Some of the common factors responsible for post-surgical dementia are lack of oxygen, low blood sugar level, electrolyte imbalances, body fluid depletion, infection and drug interactions.
A surgeon has to remember that pain is a common post-surgical complaint and delirious patients may not be able to effectively communicate with providers about pain. Both under treatment of pain and overuse of narcotics can make delirium worse and makes postoperative pain management a challenge.
Which elderly patient is at high risk of developing post-surgical delirium?
One study identified seven predictors that could be used preoperatively to assess an individual patient’s risk of delirium. These factors include age greater than 70 years, self-reported alcohol abuse, poor cognitive status, poor functional status, abnormalities of serum sodium, potassium or glucose, non-cardiac thoracic surgery or abdominal aneurysm surgery, says the JACS article.
The strongest predictors of postoperative delirium are the presence of preexisting cognitive dysfunction, advanced age and multiple medical comorbidities. To reduce the incidence of postoperative delirium, hospitals should identify patients at risk, have good geriatrics pre-operative consultation services and assign patients to multidisciplinary teams of providers with experience caring for elderly patients.
JACS article says that despite the best preventive efforts, a certain percentage of patients will become delirious in the postoperative period. It is important to identify and treat underlying causes, along with emphasizing non-pharmacologic interventions to decrease severity and duration of delirium.
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