ICU Topics > Delirium

Delirium

What is Delirium?

Delirium is defined by three core features: (A) a disturbance in attention and awareness, (B) developing over a short period of time (hours to days), representing a change from baseline that fluctuates in severity throughout the day, and (C) additional changes in cognition. These disturbances cannot be explained by a pre-existing or established neurocognitive disorder, and there must be evidence that they result directly from a medical condition, substance intoxication or withdrawal, medication exposure, toxin exposure, or multiple contributing etiologies (Slooter et al., 2020).

Delirium is one of the most common and consequential complications in the ICU. Incidence ranges from 45–87% in mechanically ventilated patients and 20–56% in non-ventilated elderly patients (Álvarez et al., 2017; Balas et al., 2012). A cohort study of 542 patients found that duration of delirium directly impacts survival — mortality increases by 11% for every 48 hours that delirium persists (González et al., 2009).

Types of delirium

Hyperactive
Hyperactive delirium is the easiest type to recognize. These patients are restless, agitated, and anxious, with potential for rapid mood swings and hallucinations. They may resist care or attempt to remove lines and devices. Behavioral presentations make this type highly visible to the team.

Hypoactive
Patients with hypoactive delirium appear inactive, sluggish, drowsy, or in a daze. They may not interact with family or respond to the environment in obvious ways. This type is also called "quiet delirium" and is frequently misidentified as sedation or depression — or missed entirely. These are often the patients you'll be told aren't ready for therapy yet. They frequently are. Hypoactive delirium is an indication to engage, not a reason to wait.

Mixed
Mixed delirium involves features of both hyperactive and hypoactive presentations. Patients may shift between restlessness and withdrawal within the same session or across the day. This fluctuation is itself a diagnostic feature and a reason to reassess frequently.

Acute encephalopathy
Acute encephalopathy refers to a rapidly developing pathobiological process in the brain — typically evolving over hours to days, and by definition within less than four weeks (Slooter et al., 2020). It is the underlying brain process that can manifest as delirium, a reduced level of consciousness, or coma. Understanding the distinction matters clinically: acute encephalopathy is the cause; delirium is one possible presentation.

Risk Factors

(Palacios-Ceña et al., 2016; Ramírez Echeverría et al., 2022)

Delirium in the ICU is rarely caused by a single factor. Risk tends to accumulate — the more factors present, the higher the likelihood of delirium developing or worsening.

Patient factors

  • Pre-existing cognitive impairment

  • Advanced age

  • Multisystem illness

Treatment and environment

  • Mechanical ventilation

  • Sedative medications — notably, many critically ill patients require sedation while in the ICU, and sedative use is one of the most consistently identified contributors to delirium

  • Untreated or undertreated pain

  • Sleep deprivation

  • Prolonged immobilization

Role of OT

(Álvarez et al., 2017; Deemer et al., 2020)

Research suggests that a majority of delirium cases are preventable through environmental modifications, appropriate day/night rhythm, and participation in early mobility and rehabilitation (Álvarez et al., 2017). ICU patients who participated in an OT-specific delirium treatment protocol demonstrated improvements in cognition, functional performance, and delirium severity — underscoring the value of a structured OT approach (Álvarez et al., 2017).

OT's primary contributions include improving cognition, supporting memory and sleep hygiene, and maintaining functional performance during the ICU stay. Critically, OT's impact extends beyond the therapy session itself. Think about the other 23 hours of the day when you're not at the bedside — carryover of strategies into the rest of the patient's day, reinforced by nursing staff and family, is what makes delirium intervention effective.

Evidence supports non-pharmacologic cognitive intervention as a first-line approach to delirium management. Three frameworks guide this work:

  • Cognitive training aims to maintain or restore specific cognitive functions through repeated, structured tasks targeting discrete cognitive domains. Examples include ADL-based tasks, spaced retrieval practice, digit span, and memory activities. Tasks should be adapted to the patient's current level and modified as function changes.

  • Cognitive stimulation uses meaningful activities and discussion to improve both cognition and social engagement. Reality orientation, reminiscence therapy, memory training, and recreational activities all fall within this category. The emphasis is on engagement and interaction, not just task performance.

  • Cognitive rehabilitation takes a more individualized approach, focusing on improving function in everyday tasks by building new strategies to compensate for cognitive deficits. Examples include introducing memory aids such as calendars, diaries, or structured routines that the patient can carry beyond the ICU.

Evaluation & Treatment

Evaluation

Screening for delirium should be a routine part of every ICU therapy evaluation. The goal is prevention, not just treatment — identifying delirium early (or identifying patients at risk) gives you the best opportunity to intervene meaningfully.

Assessments to consider:

  • CAM-ICU — the most widely used and validated delirium screening tool for ICU patients. See the CAM-ICU page for administration guidance.

  • AM-PAC "6-Clicks" Applied Cognitive Inpatient Short Form — a functional cognitive screen that can help identify delirium's impact on daily activities and participation.

Treatment

There is no single protocol for delirium management, but the overarching goal is to help the patient engage in normal, meaningful, and orienting activity. Interventions should be tailored to the patient's level of arousal and cognitive status.

Orientation and cognitive support

  • Reorient the patient to person, place, and time — aim for at least three repetitions per session and encourage nursing staff to reinforce orientation between visits

  • Speak clearly and slowly; repeat cues as needed

  • Avoid overstimulation — one input at a time, with adequate rest breaks

  • Engage the patient in conversation about familiar topics: family, friends, hobbies, routine

Sensory and environmental modifications

  • Ensure the patient has access to their glasses and/or hearing aids

  • Decorate the room with familiar items from home

  • Play the patient's preferred music

  • Optimize the environment: promote natural light exposure, reduce nighttime noise and interruptions where possible, provide a clock and calendar

Family involvement

  • Involve family and friends in sessions when possible

  • Encourage phone calls, video calls, or recorded messages from familiar voices

Sensory stimulation for lower-level patients

  • For patients with significantly reduced arousal, structured sensory stimulation (auditory, tactile, olfactory, visual) may be appropriate — see OT Treatment Ideas: Disorders of Consciousness for more detail

Communication

  • Establish a reliable communication method early. High-tech options include eye gaze devices and tablets; low-tech options include yes/no responses and communication boards. Consider the SPEACS-2 program for structured AAC implementation.

Possible Barriers

  • Receiving appropriate referrals. OT must be consulted in order to intervene. If the team isn't proactively ordering OT — or doesn't recognize delirium as an indication for referral — patients miss the window for early intervention.

  • Medical complexity. The patient's acuity may limit participation. Highly unstable patients may not be able to engage in the cognitive or sensory-based interventions most effective for delirium management.

  • Timing. Delirium interventions are most effective early. Delays in referral or treatment — whether from staffing, team awareness, or patient acuity — reduce the likelihood of meaningful impact

  • Family understanding. Families may be distressed, overwhelmed, or confused about what delirium is and why an OT is at the bedside. Without basic education, family members may resist or inadvertently undermine interventions

  • Provider support. Team members who don't understand OT's role in delirium management are less likely to support, facilitate, or reinforce OT interventions between sessions. Nurse and physician buy-in matters

  • The environment. The ICU environment — noise, constant lighting, lack of windows or clocks, frequent interruptions — actively contributes to delirium. Modifying it requires cooperation from the whole team and isn't always feasible.

Return to ICU Topics

References

Álvarez, E. A., Garrido, M. A., Tobar, E. A., Prieto, S. A., Vergara, S. O., Briceño, C. D., & González, F. J. (2017). Occupational therapy for delirium management in elderly patients without mechanical ventilation in an intensive care unit: A pilot randomized clinical trial. Journal of Critical Care, 37, 85–90. https://doi.org/10.1016/j.jcrc.2016.09.002

Balas, M. C., Vasilevskis, E. E., Burke, W. J., Boehm, L., Pun, B. T., Olsen, K. M., Peitz, G. J., & Ely, E. W. (2012). Critical care nurses’ role in implementing the “ABCDE Bundle” into practice. Critical Care Nurse, 32(2), 35–48. https://doi.org/10.4037/ccn2012229

Deemer, K., Zjadewicz, K., Fiest, K., Oviatt, S., Parsons, M., Myhre, B., & Posadas-Calleja, J. (2020). Effect of early cognitive interventions on delirium in critically ill patients: A systematic review. Canadian Journal of Anesthesia/Journal Canadien d’anesthésie, 67(8), 1016–1034. https://doi.org/10.1007/s12630-020-01670-z

González, M., Martínez, G., Calderón, J., Villarroel, L., Yuri, F., Rojas, C., Jeria, Á., Valdivia, G., Marín, P. P., & Carrasco, M. (2009). Impact of delirium on short-term mortality in elderly inpatients: A prospective cohort study. Psychosomatics, 50(3), 234–238. https://doi.org/10.1176/appi.psy.50.3.234

Ista, E., Trogrlic, Z., Bakker, J., Osse, R. J., van Achterberg, T., & van der Jagt, M. (2014). Improvement of care for ICU patients with delirium by early screening and treatment: Study protocol of iDECePTIvE study. Implementation Science, 9(1), 143. https://doi.org/10.1186/s13012-014-0143-7

Palacios-Ceña, D., Cachón-Pérez, J. M., Martínez-Piedrola, R., Gueita-Rodriguez, J., Perez-de-Heredia, M., & Fernández-de-las-Peñas, C. (2016). How do doctors and nurses manage delirium in intensive care units? A qualitative study using focus groups. BMJ Open, 6(1), e009678. https://doi.org/10.1136/bmjopen-2015-009678

Peterson, J. F., Pun, B. T., Dittus, R. S., Thomason, J. W. W., Jackson, J. C., Shintani, A. K., & Ely, E. W. (2006). Delirium and its motoric subtypes: A study of 614 critically ill patients. Journal of the American Geriatrics Society, 54(3), 479–484. https://doi.org/10.1111/j.1532-5415.2005.00621.x

Ramírez Echeverría, M. de L., Schoo, C., & Paul, M. (2022). Delirium. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK470399/

Slooter, A. J. C., Otte, W. M., Devlin, J. W., Arora, R. C., Bleck, T. P., Claassen, J., Duprey, M. S., Ely, E. W., Kaplan, P. W., Latronico, N., Morandi, A., Neufeld, K. J., Sharshar, T., MacLullich, A. M. J., & Stevens, R. D. (2020). Updated nomenclature of delirium and acute encephalopathy: Statement of ten Societies. Intensive Care Medicine, 46(5), 1020–1022. https://doi.org/10.1007/s00134-019-05907-4