Marino The ICU Book 4e, IE

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Disorders of Consciousness

common presentation of delirium is lethargy and somnolence. Failure to recognize the hypoactive form of delirium may explain why the diagno- sis of delirium is missed in as many as 75% of patients (12). Delirium vs. Dementia Delirium and dementia are distinct mental disorders that are often con- fused because they have overlapping clinical features (i.e., attention deficits and disordered thinking). Furthermore, as many as two-thirds of hospitalized patients with dementia can have a superimposed delirium (8,13), which further blurs the distinction between these two conditions. The principal features of delirium that distinguish it from dementia are the acute onset and fluctuating course. Predisposing Conditions Several conditions promote delirium in hospitalized patients, including (a) advanced age, (b) sleep deprivation, (c) unrelieved pain, (d) pro- longed bed rest, (e) major surgery, (f) encephalopathy, (g) systemic inflammation, and (h) deliriogenic drugs (6,8,11). Deliriogenic Drugs Several types of drugs can promote delirium, including (a) anticholiner- gic drugs, (b) dopaminergic drugs, (c) seritonergic drugs, and (d) drugs that promote gamma-amino-butyric-acid (GABA)-mediated neurotrans- mission, such as benzodiazepines and propofol (6). Diagnosis Validated screening tools are recommended for the detection of delirium because (as mentioned earlier) the diagnosis of delirium is frequently missed (12). The Confusion Assessment Method for the ICU (CAM-ICU) is the most reliable tool for the detection of delirium (6,9), and it is available (along with an instructional video) at www.icudelirium.org. Management Preventive Measures Recommended measures for reducing the risk of delirium in the ICU include (a) adequate treatment of pain, (b) maintaining regular sleep- wake cycles, (c) promoting out-of-bed time, (d) encouraging family visi- tation, and (e) limiting the use of deliriogenic drugs like midazolam and lorazepam, if possible (6,8). DEXMEDETOMIDINE: Sedation with dexmedetomidine, an alpha-2-adren- ergic receptor antagonist, is associated with fewer episodes of delirium than lorazepam or midazolam (14,15). This drug provides an alternative to benzodiazepines for sedation in ICU patients who are at risk for delir- ium (which includes most ICU patients). For more information on dex- medetomidine, see Chapter 51.