
Research
Relevant publications relating to DeltaScan
- In 2009, Van Eijk, Slooter et al. published an article about the under-diagnosis of delirium in general and the hypo-active form of delirium in particular. Van Eijk, M., Marum, R., Klijn, A., de Wit, N., Kesecioglu, J., Slooter, A.J. (2019). Comparison of delirium assessment tools in a mixed intensive care unit. Critical Care Medicine. 37(6):1881-1885.
- In 2011, Van Eijck, Slooter et al. examined how delirium screening instruments performed in daily clinical practice. The results demonstrated a low sensitivity of 47%. In the case of hypo-active delirium – the most prevalent form – the sensitivity was only 31%. This formed the motivation to develop an objective screening instrument. Boogaard, M. van den, van Eijk, M., Eikelenboom, P., van Matrum, R., Benner, P., Honing, M. (2011). Routine use of the confusion assessment method for the intensive care unit. American Journal of Respiratory Critical Care Medicine, 184(3), 340-344.
- In 2015, Van der Kooi, Slooter et al. published an article describing the technological basic principles of screening for delirium using EEG. Van Der Kooi, A.W., I. J., Klijn, F.A., Koek, H.L., Meijer, R. C., Leijten, F. S., & Slooter, A. J. (2015). Delirium detection using EEG: what and how to measure. CHEST Journal, 147(1), 94-101.
- In 2017, Numan et al. published a study demonstrating how difficult it is to recognise delirium. The gold standard for the diagnosis of delirium is an evaluation by a delirium expert. In 21% of the cases these experts differed in their opinions. Only 32% of the actual cases of delirium were recorded in the nursing files, which points to under-detection of delirium in clinical practice. There is a clear need for a user-friendly, reliable method to recognise delirium in clinical practice. EEG could potentially serve as an objective screening method for delirium. Numan, T., Boogaard, M. van den, Kamper, A.M., Rood, P. J., Peelen, L. M., & Slooter, A. J. (2017). Recognition of Delirium in Postoperative Elderly Patients: A Multicenter Study. Journal of the American Geriatrics Society.
- In 2019, Numan et al. published results which demonstrate that it is possible to diagnose delirium in older post-operative patients using an automatically analysed 1-channel EEG. This method could facilitate objective screening of delirium, in which the result is not dichotomised but instead provides a continuous scale. Numan, T., Boogaard, M. van den, Kamper, A.M., Rood, P. J., Peelen, L. M., & Slooter, A. J. (2018). Delirium detection using relative delta power based on 1 minute single-channel EEG: a Multicenter Study. British Journal of Anaesthesia.
- In 2019, a study by Fleischmann et al. demonstrated that a combination of several EEG electrodes can be used for accurate identification and diagnosis of patients with delirium in a mixed cohort of several thousand patients. The diagnostic performance of qualitative EEG exceeded that of classical clinical delirium tests, despite the absence of a priori information about the condition of the patient. Fleischmann et al.(2019). Diagnostic Performance and Utility of Quantitative EEG Analyses in Delirium Confirmatory Results From a Large Restrospective Case-Control Study. Clinical EEG and Neuroscience, 50 (2), 111-120.
- In 2019, Kimchi et al. demonstrated that EEG retardation detected in clinical practice was correlated to the severity of delirium and was a predictor of unfavourable clinical outcomes, such as prolonged hospitalisation, poorer functional outcomes and increased mortality. Kimchi E.Y., Neelagiri A., Whitt W., Rao A.S., Ryan, S.L., Gadbois, G., Groothuysen, D., Westover, M.B., (2019). Clinical EEG slowing correlates with delirium severity and predicts poor clinical outcomes. Neurology.
- In 2020, Tanabe et al. published research stating that delirium is related to retarded frontal and occipital EEG activity. Tanabe, S., Mohanty, R., Lindroth, H., Prabhakaran V., Bank, M., Sander, R. Cohort Study into the neural correlates of postoperative delirium: the role of connectivity and slow-wave activity. BJA, 125(1): 55-56, juli 2020.
- In 2021, Slooter et al. published a position paper that urges to end segregation between acute encephalopathy and delirium under the title “Updated nomenclature of delirium and acute encephalopathy: statement of ten Societies“. 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. Intensive Care Med, 2020 May;46(5):1020-1022.
- In 2021 Hut et al. published a study that demonstrates that acute encephalopathy in single channel EEG largely overlaps with a clinical diagnosis of delirium. Hut, S.C., Dijkstra-Kersten, S.M., Numan, T., Henriquez, N.R., Teunissen, N.W., Boogaard, M. van den, Leijten, F.S., Slooter, A.J., EEG and the Clinical assessment in delirium and acute encephalopathy. Psychiatry Clin Neurosci, 2021 Aug;75(8):265-266.
- In 2022 Ditzel et al. published that automated polymorphic delta activity detection in 1-channel EEG [ed.: DeltaScan algorithm] had high sensitivity and specificity for acute encephalopathy and delirium. Ditzel, F.L., Hut, S.C., Dijkstra-Kersten, S.M., Numan, T., Boogaard, M. van den, Leijten, F.S., Slooter, A.J., an automated EEG algorithm to detect polymorphic delta activity in acute encephalopathy presenting as po delirium. Psychiatry Clin Neurosci, 2022.
Breakthroughs in delirium research
The severity of acute encephalopathy and delirium is increasingly recognised. This is reflected in the enormous increase in the number of publications on this topic. Only 10 articles about delirium were published in 1995, compared to more than 250 articles in 2015. We developed DeltaScan to meet the obvious need for improved and early detection of delirium. Listed below are several publications that encouraged us to get a better grip on delirium.
In 2010, Heymann (Germany) demonstrated that treating delirium too late results in worse outcomes for the patient[1]. In 2011, Leslie and Inouye (USA) determined that the healthcare costs attributable to delirium are so high that they are ranked between the costs for diabetes and cardiovascular diseases[2]. In 2013, Pandharipande, Ely et al. (USA) demonstrated that a longer duration of delirium is associated with more significant long-term cognitive deterioration[3]. Ely[4] and later Pisani[5] demonstrated that each day that delirium persists is independently associated with an increase in the mortality risk by 10%.
Slooter (NL) has demonstrated that delirium results in worse outcomes in many cases and that this deterioration is independent of the severity of the underlying disease[6]. As it became increasingly clear how severe delirium actually is, various groups of scientists started searching for ways to recognise delirium in an early stage. As early as 2001, Marcantonio (USA) and others had determined that intensive screening by geriatric specialists can limit the burden of delirium[7]. However, Slooter (NL) and others demonstrated in 2011 that the screening instruments currently in use in daily practice in the intensive care units have a poor sensitivity (47%)[8].
A large meta-analysis by Marcantonio (USA) in 2017 concluded that up to 75% of the patients had a hypo-active or silent delirium and that only 12% to 35% of delirium patients are diagnosed. The patients that do receive a diagnosis are mainly those with hyperactive delirium [9]. Inouye et al. (USA) described in 2014 that suffering from delirium not only contributes to a higher risk of mortality, but also to an increased risk of admission to a nursing home due to loss of ADL functionalities [10].
In 2010, Martin et al. (USA) studied the relationship between delirium and (post-operative) sepsis, in which they stated that delirium is an independent predictor of sepsis [11]. Van den Boogaard et al. (NL) demonstrated that the cognitive problems following hospitalisation were significantly higher in patients who had suffered delirium, compared to patients without delirium [12]. Mulkey et al. (USA) recently described the use of EEG in the detection of delirium, stating that EEG – with use of the latest techniques – allows for earlier and improved detection of delirium [13].
Download publications
[1] Heymann et al, 2010, J Int Med Res [2] Leslie and Inouye, 2011, JAGS [3] Pandharipande, et al., 2013, NEJM [4] Ely et al, 2004, JAMA [5] Pisani et al, 2009, AJRCCM [6] Slooter, 2013,Nat Rev Neurol [7] Marcantonio et al., 2001, JAGS [8] Slooter et al., 2011, AJRCCM [9] Marcantonio, 2017, NEJM [10] Inouye et al., 2014, Lancet [11] Martin et al., 2010, Crit Care [12] Van Den Boogaard, 2012, Crit Care Med [13] Mulkey et al., 2019, Dimens Crit Care Nurs
Research within UMC Utrecht
that resulted in DeltaScan
- Numan published her thesis “EEG in delirium” in 2017. Numan, T. (2017) EEG in delirium (Thesis, University of Utrecht).
- In 2014, Van der Kooi published her thesis on the neurophysiology of delirium, in which she examined whether neurophysiological changes related to delirium offer opportunities for the detection of delirium. Van der Kooi, A.W. (2014) “Neurophysiology of delirium” (Thesis, University of Utrecht). Link: document.

EEG-registration without delirium

EEG-registration with delirium
The international guidelines are unambiguous
Every single guideline states that there is a need for improved and early detection of delirium.
“Considering the enormous burden that post-operative delirium imposes on patients, their loved ones, healthcare organisations and public resources, the anaesthesiologists employed in Europe should make every effort to establish integrated measures to reduce the incidence and duration of post-operative delirium.”
“Early diagnosis of post-operative delirium is vital in facilitating targeted and effective treatment.”
“Due to the fluctuating nature of post-operative delirium, staff in the recovery room should screen patients for post-operative delirium at least once per shift.”
“Figures show that delirium remains undiagnosed in more than half of all cases.”
“Delayed treatment appears to result in a prolonged duration of the delirium, which in turn is associated with a deterioration in cognitive and functional recovery and with an increase in morbidity and mortality amongst hospitalised patients.”
“Compared to patients of the same age without delirium, patients with delirium have an increased mortality risk, a longer hospitalisation period, a higher risk of falling, a higher risk of becoming more dependent on care after discharge and a higher risk of developing dementia.”
“Although delirium is a common condition, its detection leaves much to be desired and many cases are missed.”
“Rapid diagnosis & timely treatment of underlying causes are important factors in limiting the severity and the duration of delirium and in reducing the risk of complications.”
“[Delirium] is a serious condition that is associated with unfavourable outcomes. However, with timely intervention, this condition can be prevented and treated.”
“Despite the negative prognostic implications of suffering delirium, most hospitals do not pay sufficient attention to the occurrence of delirium… Research indicates that delirium is not recognised in two thirds of patients.”
“Early diagnosis [of delirium] can result in rapid identification and (if possible) correction of the etiology, reassurance of patients who experience frightening symptoms, (drug and non-drug) treatment and evaluation of the efficacy of the treatment.”
“Delayed treatment appears to result in a prolonged duration of the delirium, which in turn is associated with a deterioration in cognitive and functional recovery and with an increase in morbidity and mortality amongst hospitalised patients.”
Systematic screening for pain, degree of sedation and delirium and use of targeted sedation, analgesia and delirium protocols have been linked to a lower incidence of nosocomial infections, shorter ventilation times, shorter ICU admission, lower mortality and savings on resources.”
“Screening for delirium should be performed regularly (every 8 hours) and the results should be documented.”
Page 153:
“Post-operative delirium can have detrimental consequences, such as delayed mobilisation, prolonged treatment, prolonged hospitalisation and obstruction of early rehabilitation. There are various diagnostic instruments that healthcare providers can use to assess their patients effectively and uniformly. Healthcare organisations should consider the use of such an instrument.”
Delirium that is diagnosed early enough can be treated
There are clear recommendations about how delirium should be treated. These recommendations are included in the following guidelines:
- “Clinical Practice Guideline for Postoperative Delirium in Older Adults” by the American Geriatrics Society (USA, 2014);
- “Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU” by the Society of Critical Care Medicine (USA, 2018);
- “Delirium: prevention, diagnosis and management” by the National Institute for Health and Care Excellence (NICE) (United Kingdom, 2019).

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