Delirium in the postanesthesia care unit

Published on 07/02/2015 by admin

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Last modified 07/02/2015

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CHAPTER 114

Delirium in the postanesthesia care unit

Carla L. Dormer, MD

Postoperative delirium is an acute onset of altered or fluctuating mental status combined with significant inattention that can present in multiple ways. Although often thought to include one or more of the following manifestations—hyperarousal, agitation, hyperactivity, and even frank psychosis—postoperative delirium more often exhibits as hypoactivity, which may include flat affect, withdrawal, and lethargy.

Postoperative delirium occurs more frequently at the extremes of age, as well as following certain operations. In children, delirium is relatively common (with a reported incidence of approximately 30%), manifesting as emergence excitement or agitation (e.g., inconsolable crying or disorientation) occurring within the first 10 min of arrival in the postanesthesia care unit (PACU) and resolving within an hour. If children are still asleep when brought to the PACU, they can nonetheless experience agitation, but it will occur later in their PACU stay.

Predisposing and perioperative risk factors

Risk factors for postoperative delirium are summarized in Box 114-1. Patients with no risk factors have a 9% chance of developing postoperative delirium. For those with one or two risk factors, the chance increases to 23%, and for those with three or four risk factors, it’s up to 83%. Multiple hypotheses have been proposed as to why certain individuals are at risk for developing delirium. In elderly patients, contributing factors include smaller brain mass (atrophy) and a decreased number of neurons, as well as decreased neurotransmitter (acetylcholine, serotonin, and dopamine) production and receptor density. Accordingly, the elderly appear to have limited “cognitive reserve.” Therefore, even minor disturbances can lead to postoperative delirium. Specifically, severe illness, cognitive impairment with and without dementia, dehydration, and substance abuse have been shown to be predisposing risk factors. Preexisting diminished executive function and depression are independent predictors of postoperative delirium.

Box 114-1 Predisposing and Perioperative Factors Associated with Increased Risk for Delirium in Postanesthesia Care Unit

Predisposing Factors	Perioperative Factors
Abnormal glycemic control Age >65 y ASA score ≥3 BUN/Cr >18 Cognitive dysfunction or dementia ^† Depression Excessive alcohol use Illicit drug use or use of ≥3 prescription drugs Immobility Intracranial injury Male sex Neurologic disease ^‡ Sensory impairment, particularly visual Sepsis Use of β-adrenergic receptor blocking agents Metabolic derangements