Delirium

Make the Diagnosis: Delirium

Prior Probability

Delirium describes a state where patients have a reduced ability to focus or to sustain or shift attention with an associated change in cognition. Patient may also develop perceptual disturbances. These events occur over a short period of time, and they fluctuate during the course of a day. The diagnosis is primarily clinical and based on careful observation of key features. Consensus from an expert panel identified several clinical features of delirium: acute onset and fluctuating course, inattention, disorganized thinking, altered level of consciousness, disorientation, memory impairment, perceptual disturbances, increased or decreased psychomotor activity, and disturbance of the sleep-wake cycle.¹ The key diagnostic feature that helps to distinguish delirium from dementia is that delirium has an acute and rapid onset, whereas dementia is much more gradual in progression. Alternations in attention and changes in level of consciousness also favor a diagnosis of delirium. A hypoactive form of delirium is characterized by lethargy and reduced psychomotor functioning, while a hyperactive form is more easily recognized because patients are agitated or hypervigilant, or they have hallucinations.² Patients may fluctuate between the 2 forms.

Delirium has a relatively high prevalence among some populations of hospitalized patients, with many of the cases representing iatrogenic incident cases. The prevalence varies broadly depending on the setting and patient situation; among patients admitted to a geriatric unit, the prevalence is 9%-43%,^3-5 while those in a postcardiac surgical unit have a prevalence of 12%-27%.^{6, 7}

Population for Whom Delirium Should Be Considered

Because of the high prevalence, hospitalized adult patients should be assessed at least daily for delirium. This is most important for those patients who are most ill and admitted to intensive care or postoperative care units or, older patients. The fluctuating nature of delirium means that the patient's visiting family or nurses may detect the condition first. This is especially true when the physician does not spend an adequate amount of time with the patient to detect subtle clues.

Assessing the Likelihood of Delirium

The Global Attentiveness Rating (GAR) requires a 2-minute conversation with the patient, following which the physician rates the patient's ability to engage in a normal conversation. Among the many screening tools for assessing delirium that require <5-minute interaction with the patient, the Confusion Assessment Method (CAM) has the best test characteristics and can be performed by nurses or physicians (see Box 80-1 and Table 80-1). The often used Mini-Mental Status Examination (MMSE) should not be used to screen for delirium as it had the least useful LR of all studied instruments (MMSE<24; LR+, 1.6; 95% 1.2-2.0).