Delirium in ICU
Does this patient have delirium? Diagnosis, epidemiology, risk factors.
The most widely used instruments to detect ICU delirium are the Confusion Assessment Method for the ICU (CAM-ICU) [12] and the Intensive Care Delirium Screening Checklist (ICDSC) [13]. Studies demonstrate that both tools can be implemented at the bedside by ICU staff after adequate training. ICU delirium can present as a hypoactive (quiet) type, which is not often recognized in the ICU setting unless actively sought [1]. Bedside clinical evaluation without a specified instrument for detecting ICU delirium often fails to provide an accurate diagnosis. Perhaps this occurs as a consequence of looking strictly for hyperactive signs and symptoms such as agitation and hallucinations as prompts for the presence of delirium or due to confounding effects of sedation or concurrent neurologic conditions. Although these signs and symptoms are associated with delirium, they are not specific or essential criteria for its diagnosis [14]. In fact, a significant fraction of ICU delirium cases present in a hypoactive form; sometimes hallucinations are present, but they are not needed for diagnosis. Although a number of tools are available to diagnose delirium in ICU patients, as noted above, the CAM-ICU and the ICDSC are the most valid and reliable instruments. Both can be implemented reliably in the ICU setting by the healthcare team without the need for specialists (e.g., psychiatrists, neurologists, or geriatricians). Given the importance of delirium as a predictor of worse outcomes in ICU patients and a cause of distress for patients/relatives, routine ICU delirium screening is strongly recommended [3]. Once a diagnosis of ICU delirium is established, one must consider the implications of such a diagnosis. A checklist that can aid clinicians at the bedside is provided (Fig. 1). Certainly, as in any organ failure, not all ICU delirium is the same [2, 15]. Recently, studies have demonstrated that a short duration of delirium or its reversal upon the interruption of sedation is associated with relatively good outcomes [2]. Using scores to accurately measure level of sedation can help to reduce the frequency of oversedation and its accompanying propensity toward delirium [3]. It is important to state that sedation is a major problem when a patient with suspected delirium is evaluated. On the one hand sedatives can preclude the use of validated scales; on the other hand, sedatives are both risk factors for delirium and confounders of its diagnosis as deep sedation, especially with benzodiazepines, is a well-recognized inducer of coma. Though diagnosing delirium is important, efforts should be made to prevent it, shorten its duration, and/or identify early those patients who have the potential for a higher burden of acute brain dysfunction [3].
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