Feature 1 of CAM, “Acute onset and fluctuating course,” requires that you compare the patient’s current mental status to his or her pre-hospital baseline mental status; the baseline status should be obtained from a family member, caretaker, or clinician who has observed the patient over time.10 This is intended to determine if the patient has experienced an acute change in mental status (eg, attention, orientation, cognition), usually over the course of hours to days.10 Feature 2, “Inattention,” is used to determine if the patient has a reduced ability to maintain attention to external stimuli and to appropriately shift attention to new external stimuli, and if the patient is unaware or out of touch with the environment.10 Feature 3, “Disorganized thinking,” is used to assess the patient’s organization of thought as expressed by speech or writing. Disorganized thinking typically manifests as rambling and irrelevant or incoherent speech.10 Feature 4, “Altered level of consciousness,” is used to rate the patient’s alertness level.10
A positive screen for delirium requires the presence of Feature 1 (acute onset and/or fluctuation) and Feature 2, plus either Feature 3 or Feature 4.
Is delirium—or something else—at work?
If an older adult is exhibiting cognitive and/or behavioral disturbances after undergoing surgery, it’s important to discern if these manifestations are the result of delirium, a preexisting psychiatric disorder, or some other cause if the patient has a clear sensorium (ALGORITHM).6,13,14
Delirium. If a patient’s CAM screen suggests delirium, conduct a thorough assessment for the signs and symptoms of delirium to determine if the patient meets DSM-5 criteria for the diagnosis.1 In order to avoid missing hypoactive, subtle, or atypical cases of delirium, conduct a thorough medical record and medications review, and gather assessments from the nursing staff and other team members regarding the patient’s behavior.
Preexisting psychiatric disorder. It’s important to differentiate psychiatric symptoms from those of a superimposed delirium.13 Because patients with preoperative depressive symptoms may be at increased risk for postop delirium, pre-surgical psychiatric evaluations are important for identifying even subtle psychopathological symptoms.15 (The psychiatric interview is the gold standard for diagnosis.16) For patients who have an established psychiatric diagnosis, consider consulting with the psychiatrist who is managing the patient’s psychiatric care.13
Other causes. If a patient who is exhibiting postop cognitive and/or behavioral disturbances has a reasonably accurate memory and a correct orientation for time, place, and person, interviews with the patient and caregivers (along with the psychiatric interview) will likely reveal potential causes for the behavioral problems.13
Is the patient suffering from dehydration? Drug withdrawal?
Assessment for an underlying organic cause must be performed because specific treatment for the underlying diagnosis may improve delirium.17 Common causes include hypoxia, infection, dehydration, acute metabolic disturbance, endocrinopathies, cardiac or vascular disorders, and drug withdrawal.13 An appropriate diagnostic work-up might consist of serum urea, glucose, electrolytes, liver function tests, arterial blood gas analyses, urinalysis, nutritional evaluation, electrocardiogram, and a complete blood count.
Ask patients about their use of alcohol and benzodiazepines, and consider alcohol or drug withdrawal as potential etiologies.18 Patients with delirium should also be assessed for iatrogenic hospital-related factors that could be causing or contributing to the condition, such as immobilization or malnutrition.13
Medications are a common culprit: Approximately 40% of cases of delirium are related to medication use.18 Commonly used postop medications such as analgesics, sedatives, proton pump inhibitors, and others can cause delirium.19 Carefully review the patient’s medication list.13 Medication-induced delirium is influenced by the number of medications taken (generally >3),20 the use of psychoactive medications,21 and the specific agent's anticholinergic potential.22 The 2012 updated Beers Criteria (American Geriatrics Society) is a useful resource for determining if “inappropriate polypharmacy” is the cause of postop delirium.23
Inadequate pain control. In a multisite trial,24 patients who received <10 mg/d of parenteral morphine sulfate equivalents were more likely to develop delirium than patients who received more analgesia. In cognitively intact patients, severe pain significantly increased the risk of delirium. With the exception of meperidine, opioids do not precipitate delirium in patients with acute pain.24 Not treating pain or administering very low—or excessively high—doses of opioids is associated with an increased risk of delirium for both cognitively intact and impaired patients.24
Constipation can contribute to the development of delirium.25 After surgery, patients tend to be less mobile and may be receiving medications that can cause constipation, such as opioids, iron, calcium, and channel blockers. Preventing and treating constipation in postop patients can reduce delirium risk.25