The delirium subtypes: A review of prevalence, phenomenology, pathophysiology, and treatment response

Abstract

Delirium is a highly prevalent disease in the elderly and postoperative, cancer, and AIDS patients. However it is often misdiagnosed and mistreated. This may be partly due to the inconsistencies of the diagnosis itself. Delirium is best defined currently by an association of cognitive impairment and arousal disturbance. Three subtypes (hyperactive, hypoactive, mixed) receive a definition in the literature, but those definitions may vary from author to author according to the importance they give either to the motoric presentation of the delirium or to the arousal disturbance. Our aim is to point out the inconsistencies we found in the literature, but also to identify different paths that have been explored to solve them, that is, the suggestion to emphasize the arousal disturbances in defining the subtypes instead of the motoric presentations, which seem to be more fluctuating, and because of the fluctuating course of the disease to extend the observation over a period of time, which may improve the accuracy of the diagnosis. This is not without importance from a clinical standpoint. Subtypes of delirium may be explained by different pathophysiologic mechanisms, which remain partly unexplained, and may respond to specific treatments. There is a trend to isolate core symptoms (disorientation, cognitive deficits, sleep-wake cycle disturbance, disorganized thinking, and language abnormalities) so as to distinguish them from secondary symptoms that may be correlated with the different etiologies. Our contribution is also to challenge, with new data, the accepted belief that psychotic features are quite rare in the hypoactive type of delirium. We demonstrate that delusions and perceptual disturbances, although less frequent, are present in more than half of the patients with hypoactive delirium. The psychotic features are clearly correlated with a highly prevalent rate of patients', spouses', and caregivers' distress. The mixed subtype of delirium seems to have the worst prognosis, the hyperactive showing the best prognosis. The treatment of the agitated delirious patient is also more consensual. Haloperidol remains the gold standard in the treatment of delirium regardless of the clinical presentation, but the literature provides several alternatives that may prove more specific and have less adverse effects (atypical antipsychotics, psychostimulants, anesthetics).

EEG changes and serum anticholinergic activity measured in patients with delirium in the intensive care unit

“…One possible candidate for this could be the serum anticholinergic activity (SAA). If it is assumed (i) that multiple causes of delirium pathogenetically result in a final common pathway, resulting in an imbalance between dopaminergic and cholinergic neurotransmitter systems [15][16][17]24], and (ii) that peripheral SAA levels adequately reflect the central acetylcholinergic changes, then the detection of high SAA levels should be associated with delirious symptoms and EEG parameters in ICU patients.…”

“…The relative importance of elevated SAA levels in delirium, compared to other contributing factors, is a matter of controversy in acute elderly medical patients [13,14]. The pathophysiology of delirium appears to be complex [15] and has not been completely elucidated; however, one hypothesis is that impairment of central cholinergic transmission may contribute to delirium [16,17].…”

Safety and Efficacy of Flumazenil for Reversal of Iatrogenic Benzodiazepine-Associated Delirium Toxicity During Treatment of Alcohol Withdrawal, a Retrospective Review at One Center

“…Documentation from the physician care team was also used to confirm diagnoses of delirium and assign phenomenological subtypes (i.e., hypoactive, hyperactive, or mixed) [21][22][23] based on the Riker scale [24,25] or patient description if the Riker scale was not found. Delirium was diagnosed by the DSM-IV-TR criteria.…”

Postoperative delirium: A preventable complication in the elderly surgical patient

“…In adults and in the elderly, three forms of POD are described, from "hypoactive" (reduced level of attention, apparent sedation, lethargy,) to "hyperactive" (agitation, inappropriate behaviour, restlessness and hallucination, sometimes hyper-motoric behaviour until aggressiveness) and "mixed" forms [2]. About 10-30% of all PODs are hyperactive, whereas 50% are mixed forms and 20-40% purely hypoactive [3]. Age more than 80 years seems to be a predisposing factor for the hypoactive form [3].…”

“…About 10-30% of all PODs are hyperactive, whereas 50% are mixed forms and 20-40% purely hypoactive [3]. Age more than 80 years seems to be a predisposing factor for the hypoactive form [3]. Hypoactive forms are more difficult to diagnose since hypoactive patients do less often interfere with medical treatment and care.…”