Rethinking Delirium in Critical Care

Delirium is a common but under-recognised ICU complication with short and long term cognitive, psychological, and functional consequences. It urges for a cultural change in critical care using routine screening, multidisciplinary prevention, and patient and family centred interventions to prioritise mental recovery alongside physical survival.

Mr D, a 70-year-old engineer, was admitted to the ICU with chest sepsis and acute kidney injury (AKI). Twenty-four hours later, he was intubated, sedated and ventilated. He battled through multiple organ failure, vasopressors and mechanical ventilation. When sedation was lightened, he became agitated. The ICU team re-sedated him. When extubated, he recalled fragments of terrifying hallucinations. “I thought I was dying, and no one was helping me,” he said. Weeks after discharge, he struggled to manage even simple tasks and was haunted by bad memories from his ICU stay.

Delirium: A Misunderstood Syndrome in the ICU

Delirium in the ICU is an acute, fluctuating disturbance in consciousness and cognition with three motor subtypes: hyperactive, hypoactive, and mixed. It’s extremely common, especially in ventilated patients, but frequently under-recognised. Delirium, often dismissed as a temporary inconvenience or simply ICU confusion, is a complex acute brain dysfunction with long-term consequences. Despite its prevalence, it remains underdiagnosed, undertreated, and misunderstood-even in the most advanced ICUs.

The Paradox of High Prevalence But Low Recognition

Delirium is one of the most common complications of critical illness, affecting an estimated 30–50% of non-ventilated ICU patients and up to 80% of those on ventilators. Delirium is associated with increased morbidity, mortality, and long-term cognitive decline (Girard et al. 2008).

Studies have shown that ICU teams miss up to two-thirds of delirium cases without the use of standardised screening tools. This paradox, where a syndrome so prevalent remains so underdiagnosed, reveals a systemic blind spot in critical care. The rate of missed diagnosis of delirium remains as high as 55-60%, and no effective drug has been available to prevent and treat ICU delirium (Ma et al. 2025). Reporting of delirium is poor in the U.K., indicating that awareness and reporting procedures need to be improved (NICE Guidelines 2023).

Unlike other ICU syndromes like acute respiratory distress syndrome (ARDS) and sepsis, delirium remains under-recognised and lacks clear protocols or urgent management strategies. Part of the problem is that delirium doesn’t always look like the well-known version of confusion. Hypoactive delirium, particularly, is frequently mistaken for fatigue or depression. Its fluctuating nature means that it might not be captured during ward rounds or at shift changes, especially when systematic screening is not routine.

Delirium independently increases the risk of death, longer ventilation, extended ICU and hospital stays, and long-term cognitive issues. Despite this, it is often diagnosed late, missing the chance for effective intervention.

How Delirium Disrupts Mind and Care Flow

Delirium deeply affects both patients and ICU care. It distorts the patient’s mind with fear, confusion, and hallucinations, often leaving lasting emotional and cognitive scars. It also disrupts care delivery, hinders team communication, and raises the risk of harm.

Delirious patients may bring out the use of physical and or chemical restraints, both of which can further worsen delirium. Communication becomes nearly impossible as patients cannot participate in decisions, express needs, or reliably report symptoms. This leads to reactive management strategies instead of thoughtful, patient-centred approaches.

From a systems perspective, delirium complicates weaning from the ventilator, delays mobilisation, and prolongs ICU stays. ICU team must continuously adapt their plans to the patient’s unpredictable behaviour, often at the cost of other tasks or patients. Conclusively, delirium interferes with recovery, impairs decision-making, and fractures the therapeutic alliance.

A Perfect Storm for Delirium

ICU is paradoxically an environment provoking delirium. Alarms, lighting, sleep disruption, immobility, and unfamiliar faces create a sensory landscape that is disorienting at best and terrifying at worst. For patients who are critically ill, sedated, or mechanically ventilated, this environment becomes the setting for cognitive and psychological deterioration.

Sleep deprivation is a key factor. ICU patients are routinely exposed to noise levels far exceeding World Health Organisation (WHO) recommendations (Delaney et al. 2017; Simons et al. 2018), with frequent disruptions for vital signs, medication administration, and procedures. Without normal, uninterrupted rest, the brain loses one of its basic tools for maintaining orientation. Despite evidence that early mobilisation reduces delirium risk, many patients remain bedbound for days. That deepens the disconnection between body and mind.

Patients may lie in rooms where they cannot see a clock or window while being overwhelmed with unfamiliar voices and beeping monitors. Language barriers, hearing loss, or the presence of an endotracheal tube can make communication nearly impossible. The result is an environment where nothing makes sense, but everything feels urgent.

The ICU's critical environment often prioritises physiologic stability over psychological safety, maintaining a culture in which delirium is accepted as inescapable, rather than avoidable.

Environmental factors in the ICU create a perfect storm for delirium. Minimising sedation, normalising day-night cycles, reducing noise, and promoting early mobility are essential prevention strategies (Reade et al. 2014). As emphasised by evidence-based care bundles, e.g., A2I (ABCDEFGHI bundle) and Pain, Agitation, Delirium (PAD) guidelines, routine monitoring and systematic non-pharmacologic interventions protect cognitive health and improve patient-centred outcomes.

The ICU becomes more than a place of treatment; it becomes a neurocognitive stress test. And in its current form, many patients fail. Not for lack of medical care, but because the brain was not protected as importantly as the heart or lungs. If cognitive outcomes mattered as much as ventilator settings, the culture of critical care would look very different.

Emotional, Psychological, and Factual Impact

For ICU patients, delirium is not just confusion. It’s terrifying, isolating, and painfully traumatic. Survivors often describe it as a vivid and disturbing agony. Some patients believe they are being held hostage, tortured, or abandoned. Others remember hearing voices, seeing insects crawling on walls, or feeling a profound sense of despair. These are not just delusions; they become memories. Patients frequently report flashbacks, nightmares, and post-traumatic stress disorder (PTSD) after discharge.

When Time Becomes Disordered: The Patient Experience of Delirium

"I thought I was in hell."

In a study, Svenningsen et al. (2016) interviewed ICU survivors and found that patients frequently experienced terrifying hallucinations. One patient recalled: “I saw the devil and believed I had died. I didn’t know what was real anymore."

The classic sensation of locked-in deliriumis described in a 2021 meta-synthesis of ICU survivor interviews: “I lay there without moving a muscle, totally stiff, people all around me, but no one answering me! I would be calling out to people, but no one would even look up.”

"I Can Remember Sort of Vivid People…but to Me They Were Plasticine.” Darbyshire et al. (2016) in DelusionsDelusions on the Intensive Care Unit: What Do Patients Think Is Going On? described the devastating experiences of delirious patients in the ICU. “Each time I went under, the nightmares flooded back. So, when they were telling me to sleep, I couldn't sleep because a blackness just came back over me, so I stayed awake."

The emotional fallout is profound. Many patients express guilt, shame, or fear when reflecting on their behaviour during delirium. Some question whether they are losing their mind or developing dementia. Importantly, when no one explains what delirium is, these perceptions go unverified, leaving psychological wounds unhealed.

Salluh et al. (2015) found that delirium has long-term consequences, with studies indicating an association between delirium and a higher likelihood of death, functional disability, admission to residential care, cognitive impairment, and dementia after discharge.

Approximately three-quarters of critically ill patients who were interviewed two weeks after surviving their initial illness reported delusions, and those with limited factual recall of their hospitalisations had significantly increased anxiety and symptoms of PTSD (Mart et al. 2020).

Listening to patients' stories reveals a truth often noted in daily ICU practice: delirium is not just a clinical diagnosis. It is an experience that can shape a patient’s entire memory of critical illness, colouring their recovery with fear, confusion, and uncertainty.

Failure to See Delirium

We fail to see delirium not because it is unseen, but because we are not always trained to look for it. Despite its frequency and consequences, delirium remains one of the most under-recognised syndromes in the ICU. This failure is not due to lack of concern, but due to a combination of diagnostic challenges, system limitations, and cultural blind spots.

Delirium is fluctuant, often appears subtle, and can present in forms that defy our expectations. Hyperactive delirium is more likely to be noticed due to agitation or aggression. But hypoactive delirium often masquerades as fatigue, depression, or quiet compliance. Many patients appear calm but are, in fact, profoundly disoriented. In busy ICUs, this presentation is easily missed.

Clinicians often rely on intuition rather than structured assessments. Without tools like the Confusion Assessment Method for ICU (CAM-ICU) or the Intensive Care Delirium Screening Checklist (ICDSC) used routinely, delirium is underdiagnosed. A 2005 study by Ely et al. found that ICU staff missed two out of every three delirium cases when relying on clinical impression alone.

Early detection with CAM-ICU or ICDSC leads to prompt assessment and intervention. Without validated assessment, up to 75% of delirium will be missed. It is noted that delirium assessment tools such as CAM-ICU have not been validated in autistic populations and, as such, may present challenges to delirium assessment (ICS guidelines 2025).

Notably, delirium can and often does coexist with underlying neurological disease, such as dementia, traumatic brain injury (TBI), and stroke, and so is not precluded from developing in these patients (Mart et al. 2020). This leads to inappropriate treatment with antipsychotics when not needed, or additional sedation that deepens the problem.

Delirium is still conceived by many as an unavoidable part of critical illness. Unlike sepsis or stroke, it lacks a sense of urgency. This concept undermines efforts to prevent or treat it, perpetuating the cycle of inattention.

The consequence of missing delirium in patients can cause distress to both patients and families. Once a diagnosis of delirium has been made, it can facilitate discussions and support for patients and families about the experience and any long-term consequences it may have (ICS guidelines 2025).

Systemic Gaps in Monitoring, Staffing, and Training

Delirium is not only under recognised at the bedside, but also systemically unsupported at the institutional level. Few ICUs are structurally equipped to detect, manage, or prevent delirium consistently. This failure reflects gaps in staffing, education, and clinical infrastructure that hinder even the most well-intentioned care.

Monitoring is a fundamental weakness. Most ICUs do not routinely monitor brain function unless a neurologic event is suspected. Delirium screening tools exist, but their use is greatly variable, often dependent on individual practice rather than being part of the standard workflow.

The CAM-ICU is the most widely studied and validated diagnostic instrument. However, the accuracy of this tool may be less than ideal without adequate training of the providers applying it (Cavallazzi et al. 2012).

Staffing constraints additionally exacerbate the problem. ICU nurses and physicians are overcommitted, managing complex patients in time-pressured environments. Without adequate nurse-to-patient ratios, even the basics, like minimising sedatives, can be dropped. Delirium prevention often feels like a “nice-to-have” rather than a core task, particularly when life-saving interventions attract the greatest ICU team’s attention.

Training gaps remain, as many clinicians receive little formal education on delirium. It's often seen as inevitable, not preventable, and its cognitive impact is overlooked. Ongoing ICU education rarely prioritises it unless driven by local interest or adverse events.

There is some evidence from multicomponent prevention studies to suggest that an education programme for healthcare professionals who care for people at risk of delirium reduces the incidence of delirium (NICE Guideline 2023).

The outcome is a system where delirium is everyone's responsibility, but no one’s mandate. Until we embed delirium prevention and detection into the culture, infrastructure, and standards of ICU care, we will continue to fail patients in ways that are both preventable and profound.

Can We Prevent the Fog?

Despite the huge challenges, progress is already underway in ICUs that have adopted structured, evidence-based approaches. Consistent application of evidence-based nonpharmacological interventions is needed in adult ICUs to address the gap in delirium care (Johnson et al. 2024). In another study, nonpharmacological interventions have been suggested as more effective than the use of drugs (Chen et al. 2022).

A multicomponent approach to delirium prevention and management may benefit ICU patients and clinicians significantly. The evidence supporting the use of multicomponent nonpharmacological interventions for delirium prevention and management is more substantial than a single component (Burton et al. 2021).

One of the most effective is the ICU Liberation initiative, bonded by the A2I bundle, which has re-evaluated how we think about patient-centred, brain-conscious critical care (Figure 1).

Each component targets a known risk factor for delirium-oversedation, immobility, isolation, unmanaged pain, and fragmented care. Together, they form a practical strategy that embeds brain-protective practices into daily ICU practice.

The ICU Liberation Collaborative, a multi-centre QI initiative involving over 15,000 patients, showed significant reductions in delirium duration, ventilator days, ICU length of stay, and mortality. Vitally, implementation success depended not only on protocols, but on team culture, leadership support, and sustained education. A2I bundle performance showed significant and clinically meaningful improvements in outcomes, including survival, mechanical ventilation use, coma, delirium, restraint-free care, ICU readmissions, and post-ICU discharge disposition (Pun et al. 2019).

With commitment, coordination, and consistency, we can create an ICU culture that prioritises the brain as much as the lungs or heart. The A2I bundle is not just a checklist, but a philosophy that acknowledges the centrality of cognition in recovery as well.

Examples from Practice

A retrospective study at a U.K. tertiary hospital ICU examined 218 delirium patients over three separate 24-hour periods, tracking bed occupancy and collecting data on demographics, diagnoses, comorbidities, length of stay, substance misuse, psychiatric history, neurodiversity, and CAM-ICU scores. The findings highlight the complex psychiatric needs of ICU patients and the significant mind-body connection (Table 1).

Delirium affects existing mental illness and can cause new psychiatric issues, especially in long-stay patients (Figures 2 and 3). More research is needed to better understand and manage delirium.

Interdisciplinary Collaboration in Delirium Care

The future design of delirium-free ICUs should emphasise a multidisciplinary approach, involving physicians, nurses, physiotherapists, clinical pharmacists, psychologists, speech and language therapists, dieticians, occupational therapists, spiritual care providers, and social workers to address the comprehensive needs of each patient. This ensures multidimensional diagnostics and therapeutics for thorough assessment, treatment, and follow-up.

Psychologists play a critical role within the ICU team by providing daily consultations to mitigate distress, manage mood and sleep disorders, and address the psychological impact of sedation and delirium, thereby improving patient and family outcomes. Early interventions are essential to facilitate recovery, communication, and long-term care planning.

Additionally, dieticians are integral in managing the gut-brain axis through evidence-based nutritional strategies, as disruptions to the gut microbiome exacerbated by anaesthetics and sedatives contribute to delirium pathogenesis. Dieticians support both nutritional needs and delirium prevention by modulating neuroinflammatory pathways.

Healthcare providers should undergo structured education and training to enhance their ability to recognise, diagnose, and manage delirium. A recent international survey among delirium experts within European countries reported that low delirium awareness, inadequate knowledge or incompetence, lack of education, and lack of time for assessment were identified as the four main barriers to improving delirium detection (Morandi et al. 2019).

Empowering the use of guidelines or protocols has been shown to be efficient in improving the care of delirium, with a direct effect on delirium outcomes. Collaboration among health care professionals such as, but not limited to, European Delirium Association (EDA), European Geriatric Medicine Society (EuGMS), European Academy of Nursing Science (EANS), Council of Occupational Therapists for European Countries (COTEC), World Confederation for Physical Therapy (WCPT) and the International Association of Physical Therapists working with Older People (IPTOP) is hugely important for the future management of delirium.

Over the past 10 to 15 years, using reminders and implementing guidelines or protocol strategies effectively improved delirium care, with measurable impacts on patient outcomes. Ongoing collaboration between the above-mentioned organisations plays a significant role in advancing the management of delirium. E-learning has been described as a novel approach to facilitate the possibility of providing education for large groups of people (Morandi et al. 2019).

Nurses are the first to notice cognitive changes, yet their visions are sometimes undervalued in clinical decision-making. Pharmacists help reduce delirium-inducing medications and optimise sedation strategies. Physiotherapists promote early mobility, which is one of the most effective approaches for reducing delirium. Facilitating spontaneous breathing trials (SBTs) and reducing sedation show a great benefit. Physicians must coordinate all these efforts and integrate delirium assessment into daily ward rounds.

Family members, too, are key partners. Their presence provides familiarity and emotional support that can be profoundly protective against disorientation. Involving them in reorientation, communication, and even decision-making braces the human connection that delirium so often ruins.

Incorporating family education into delirium care significantly enhances the holistic management of the condition. Educating families improves their understanding of delirium, fosters effective communication, and supports patient-centred care throughout the clinical course.

A video-based ICU delirium education intervention was effective in educating family members of ICU patients on the detection of delirium symptoms, its prevention and management using nonpharmacologic strategies. That may act as a primer for family members to partner with the ICU care team in delirium-related patient issues or empower families to participate in delirium-focused discussions (Krewulak et al. 2020).

Creating a culture where delirium is everyone’s responsibility requires strategic team development, shared responsibility, and mutual respect. In this way, delirium becomes not just a clinical aim, but a unifying challenge that anneals ICU teams and restores a more humane vision of critical care.

Post-ICU Cognitive Dysfunction and Delirium’s Legacy

This is just the beginning. For most ICU survivors, the story doesn’t end at discharge. Delirium, once dismissed as temporary confusion, is the portal to long-term cognitive impairment. Its legacy can be extreme and persistent. In one study of mechanically ventilated ICU patients, Girard et al. (2010) concluded that duration of delirium was independently associated with long-term cognitive impairment in ICU survivors. Furthermore, the number of days of ICU delirium was associated with higher 1-year mortality after adjustment for relevant covariates in an older ICU population (Pisani et al. 2009).

Up to two-thirds of patients who had ICU delirium develop measurable cognitive impairments that affect memory, attention, processing speed, and executive function. These deficits can mimic mild Alzheimer’s disease or traumatic brain injury (TBI), even in younger patients. For some, it means losing the ability to return to work, manage finances, or live independently. For others, it’s a lasting sense of being mentally not the same.

Delirium is linked to PTSD, anxiety, and depression. Survivors describe having nightmares, fear of hospitals, and feelings of shame about their uncontrolled behaviour. Families carry the emotional burden, often reporting distress after witnessing their loved ones hallucinate.

Delirium’s true cost extends far beyond the ICU, shaping the trajectory of recovery for months or years. It turns a short episode of organ failure into a chronic cognitive illness, affecting quality of life in ways we are far from quantifying. Patients who had prolonged delirium showed poorer global cognition after discharge and greater risks of dementia and long-term cognitive impairment, regardless of the severity and duration of their delirium, as per a review based on the 2018 PADIS guidelines.

Recognising delirium as a predictor, not just a symptom, demands a change in how we define ICU success. Survival is no longer the only benchmark. Preserving the integrity of the mind, the memory, and the self is the legacy we must stand for.

The Societal and Caregiver Burden

It does not end when the ICU stay does. Delirium impacts future ripples, affecting families, caregivers, and health systems in ways that are invisible but profoundly disruptive.

For caregivers, the burden can be life-altering. When a loved one emerges from the ICU with cognitive decline, emotional instability, or personality changes, families are mandated to become untrained caregivers overnight. Many feel unprepared for the aftermath: forgetfulness, paranoia, and lack of insight or motivation. These changes can affect relationships, cause financial difficulties, and lead to emotional stress.

Studies have shown that caregivers of ICU survivors experience anxiety, depression, and even PTSD. Their roles change from partner or child to nurse, advocate, and protector, often with limited support. In the meantime, the healthcare system offers few pathways for follow-up, rehabilitation, or education tailored to post-delirium recovery.

Post-ICU cognitive impairment significantly impacts the economy. Patients often need long-term care or rehospitalisation, and both patients and caregivers suffer from lost productivity, affecting healthcare use and quality of life.

Despite this burden, delirium remains under-recognised. Unlike stroke or dementia, post-ICU cognitive dysfunction lacks public awareness, formal screening programmes, and institutional resources. Many patients and families suffer without language to express their experiences or systems to support them.

Evolution of ICU Environments to Reduce Delirium Risk

The modern ICU design aims to create a more comforting, home-like environment through architectural changes. Features like separate corridors for staff and families, and spacious, ergonomic rooms support this shift.

The visual art has shown potential in reducing stress and improving mental health. Art therapy is gaining recognition as a valuable tool for emotional expression and psychological support in ICU settings. Improvements in the ICU sounds, light control, floor planning, and room arrangement can facilitate a healing environment that minimises stressors and aids delirium prevention and management. The following pictures (Figures 4 and 5) demonstrate the future of delirium-free ICU design and highlight the importance of a healing environment (Kotfis et al. 2022).

From Awareness to Action

We must move beyond viewing delirium as a secondary concern and instead treat it as a central clinical, ethical, and human challenge.

The culture of many ICUs still prioritises stabilising haemodynamic, oxygenating lungs, and correcting labs. But the patient's mind, identity, and experience remain in the background. Delirium is frequently under-screened and under-addressed. Prevention is randomly applied. Education is minimal. Families are left out. And the result is predictable: patients leave the ICU alive, but cognitively impaired.

A change is a must. We need a culture where protecting the brain is as routine as protecting other organs, where multidisciplinary teams drive shared accountability for mental clarity, not just survival. Institutions must include delirium awareness into training, quality metrics, and resource allocation. A multicomponent delirium education and training programme for nurses was rated positively, improved CAM-ICU knowledge, and increased delirium detection. Delirium detection across the health system improved from 9.1% at baseline to 21.2% in ICUs that participated in a delirium education workshop (Sinvani et al. 2021).

Clinicians must use validated tools, act on assessments, and embrace non-pharmacologic strategies even when they require time and creativity. Nurses must be supported to engage in delirium preventive care. Families must be seen as collaborators, not visitors. Without consistent involvement from the healthcare team and patient families, opportunities may have been lost to optimise family-centred care practices in the ICU (Johnson et al. 2024).

Conclusion

Delirium remains hidden because we allow it to be. But behind each case is a voice, a life, and a future at risk. Making delirium visible means more than diagnosing it. It means understanding, preventing, treating it and never again accepting it as inevitable. In the ICU, we are stewards not just of survival, but of identity. This is a cultural issue. The evidence and the tools exist. What’s needed now is action. The ICU should be a place not just to preserve life, but to protect what makes that life worth living. Changing the culture around delirium is not optional. It is an ethical mandate.

Acknowledgement

We would like to thank the other agitation and delirium service evaluation project team members at our ICU department for their hard and dedicated work contributing to data collection, data analysis and presenting their research at the regional critical care connection symposium in South London. Dr Shams Hussien, Clinical Fellow, ICU, King’s College Hospital, Ms Anya Lee, specialist psychological therapist for long-term conditions and ND disorders.QI project led by Dr Rowena Carter, ICU psychiatry liaison consultant, King’s College Hospital and Dr Masumi Tanaka, NeuroICU consultant and EEG fellow, King’s College Hospital.  

Conflict of Interest

None