Unravelling the pathophysiology of delirium: a focus on the role of aberrant stress responses

A clinical update on delirium: from early recognition to effective management

Delirium is a neuropsychiatric syndrome characterized by altered consciousness and attention with cognitive, emotional and behavioural symptoms. It is particularly frequent in elderly people with medical or surgical conditions and is associated with adverse outcomes. Predisposing factors render the subject more vulnerable to a congregation of precipitating factors which potentially affect brain function and induce an imbalance in all the major neurotransmitter systems. Early diagnosis of delirium is crucial to improve the prognosis of patients requiring the identification of subtle and fluctuating signs. Increased awareness of clinical staff, particularly nurses, and routine screening of cognitive function with standardized instruments, can be decisive to increase detection rates of delirium. General measures to prevent delirium include the implementation of protocols to systematically identify and minimize all risk factors present in a particular clinical setting. As soon as delirium is recognized, prompt removal of precipitating factors is warranted together with environmental changes and early mobilization of patients. Low doses of haloperidol or olanzapine can be used for brief periods, for the behavioural control of delirium. All of these measures are a part of the multicomponent strategy for prevention and treatment of delirium, in which the nursing care plays a vital role.

Urinary protein profiling in hyperactive delirium and non-delirium cardiac surgery ICU patients

BACKGROUND

Suitable biomarkers associated with the development of delirium are still not known. Urinary proteomics has successfully been applied to identify novel biomarkers associated with various disease states, but its value has not been investigated in delirium patients.

RESULTS

In a prospective explorative study hyperactive delirium patients after cardiac surgery were included for urinary proteomic analyses. Delirium patients were matched with non-delirium patients after cardiac surgery on age, gender, severity of illness score, LOS-ICU, Euro-score, C-reactive protein, renal function and aorta clamping time. Urine was collected within 24 hours after the onset of delirium. Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) was applied to detect differences in the urinary proteome associated with delirium in these ICU patients. We included 10 hyperactive delirium and 10 meticulously matched non-delirium post-cardiac surgery patients. No relevant differences in the urinary excretion of proteins could be observed.

CONCLUSIONS

We conclude that MALDI-TOF MS of urine does not reveal a clear hyperactive delirium proteome fingerprint in ICU patients.

TRIAL REGISTRATION

Clinical Trial Register number: NCT00604773.

Review: delirium in the elderly: a comprehensive review

Delirium is a common neuropsychiatric syndrome in the elderly characterized by concurrent impairments in cognition and behaviors. The etiologies for delirium are often multifactorial and are due to underlying medical illnesses and/or due to medication effect. The diagnosis of delirium is often missed in elderly patients and this condition may be mislabeled as depression or dementia. Untreated, delirium can have devastating consequences in the elderly with high rates of morbidity and mortality. Available evidence indicates that early detection, reduction of risk factors, and better management of this condition can decrease its morbidity rates. In this review, we discuss the etiology, neurobiology, diagnosis, prevention, and treatments for this potentially lethal condition in the elderly.

Preventing postoperative complications in the elderly

Postoperative complications are directly related to poor surgical outcomes in the elderly. This review outlines evidence based quality initiatives focused on decreasing neurologic, cardiac, and pulmonary complications in the elderly surgical patient. Important anesthesia quality initiatives for prevention of delirium, the most common neurologic complication in elderly surgical patients, are outlined. There are few age-specific quality measures aimed at prevention of cardiac and pulmonary complications. However, some recommendations for adults can be applied to the geriatric surgical population. In the future, process measures may provide a more global assessment of quality in the elderly surgical population.

Remifentanil Reduces the Incidence of Post-Operative Delirium

A secondary exploratory analysis of data from an observational study was used to study the influence of the opioid used for intraoperative anaesthesia on the incidence of post-operative delirium. Patients who had been admitted to the recovery room following elective general anaesthesia were divided into those who had received fentanyl or remifentanil. For unbiased patient analysis, matched pairs were built with respect to gender, age, physical status, anaesthetic type and surgery duration. In 752 patients, the overall incidence of delirium was 9.9% in the recovery room and 3.8% on the first post-operative day. Compared with the remifentanil group, the fentanyl group had a significantly higher incidence of delirium in the recovery room (12.2% versus 7.7%) and on the first post-operative day (5.8% versus 1.9%). Delirium in the recovery room and on the first post-operative day were both associated with a significantly prolonged post-operative hospital stay. The choice of intraoperative opioid influences the incidence of post-operative delirium. Remifentanil was associated with a lower incidence of post-operative delirium in the early post-operative period.

Hospital use, institutionalisation and mortality associated with delirium

BACKGROUND

Delirium is a disorder affecting consciousness, which gives rise to core clinical features and associated symptoms. Older patients are particularly prone, owing to higher rates of pre-existing cognitive impairment, frailty, co-morbidity and polypharmacy.

OBJECTIVES

The aim of this study was to investigate the hypotheses that delirium affects the most vulnerable older adults and is associated with long-term adverse health outcome.

METHODS

This prospective cohort study evaluated 278 medical patients aged > or = 75 years admitted acutely to a district general hospital in South Wales. Patients were screened for delirium at presentation and on alternate days throughout their hospital stay. Assessments also included illness severity, preadmission cognition, co-morbidity and functional status. Patients were followed for 5 years to determine rates of institutionalisation and mortality. Number of days in hospital in the 4 years prior to and 5 years after index admission were recorded.

RESULTS

Delirium was detected in 103 patients and excluded in 175. Median time to death was 162 days (interquartile range 21-556) for those with delirium compared with 1,444 days (25% mortality 435 days, 75% mortality>5 years) for those without (P < 0.001). After adjusting for multiple confounders, delirium was associated with an increased risk of death (hazard ratio range 2.0-3.5; P < or = 0.002). Institutionalisation was higher in the first year following delirium (P = 0.03). While those with delirium tended to be older with more preadmission cognitive impairment, greater functional dependency and more co-morbidity, they did not spend more days in hospital in the 4 years prior to index admission.

CONCLUSIONS

Delirium is associated with high rates of institutionalisation and an increased risk of death up to 5 years after index event. Prior to delirium, individuals seem to compensate for their vulnerability. The impact of delirium itself, directly or indirectly, may convert vulnerability into adverse outcome.

The role of inflammation in the pathogenesis of delirium and dementia in older adults: a review

AIMS

To review recent evidence that suggests inflammation plays a similar role in the pathogenesis of delirium and dementia.

METHODS

We performed a literature search of original research and review articles in PubMed using the keywords: delirium, dementia, and inflammation. We summarized the evidence linking inflammation to the pathogenesis of delirium and dementia.

DISCUSSION

Delirium and dementia share similarities in clinical and pathogenic features, leading to the speculation that instead of being distinct clinical entities, the two age-related conditions may be linked by a common pathogenic mechanism. Inflammatory markers have been shown to be elevated in both delirium and dementia, thereby implicating inflammation as a possible mediating factor in their genesis. There is evidence in both basic science and clinical research literature that elevated cytokines play a crucial role in the development of cognitive dysfunction observed in both dementia and delirium.

CONCLUSION

Mounting evidence supports the role of inflammation in the development of both dementia and delirium. Further studies are needed to elucidate the mechanisms underlying these relationships.

Serum S100B in elderly patients with and without delirium

OBJECTIVE

Elevation of S100B has been shown after various neurologic diseases with cognitive dysfunction. The aim of this study was to compare the serum level of S100B of patients with and without delirium and investigate the possible associations with different subtypes of delirium.

METHODS

Acutely admitted medical patients aged 65 years or more were included from 2005 through 2008. Delirium was diagnosed by Confusion Assessment Method, delirium subtype by Delirium Symptom Interview and preexistent global cognitive function by the 'Informant Questionnaire on Cognitive Decline-short form'. S100B levels were determined in serum by electrochemiluminescence immunoassay.

RESULTS

Samples of 412 patients were included, 91 during delirium, 35 after delirium and 286 of patients without delirium. Patients with delirium (31%) were significantly older, 81.5 versus 76.6 years (p < 0.001) and experienced significantly more often preexistent cognitive and functional impairment (p < 0.001). S100B level differed significantly (p = 0.004) between the three groups: median 0.07 microg/L (inter-quartile ranges: 0.05-0.14 microg/L) during delirium, 0.12 microg/L (0.05-0.29 microg/L) after delirium and 0.06 microg/L (0.03-0.10 microg/L) in patients without delirium. Combining the impact of cognitive impairment, infection and age on S100B, highest S100B was observed in the oldest patients after delirium with preexistent cognitive impaired and infection. Delirium subtype and S100B level were not significantly correlated.

CONCLUSION

Higher S100B levels were found in patients with delirium than in patients without delirium, with highest levels of S100B in samples taken after delirium. Future studies are needed to elucidate the mechanism responsible for the increase of S100B and the possible association with long term cognitive impairment.

Cerebrospinal fluid cortisol levels are higher in patients with delirium versus controls

Background

High plasma cortisol levels can cause acute cognitive and neuropsychiatric dysfunction, and have been linked with delirium. CSF cortisol levels more closely reflect brain exposure to cortisol, but there are no studies of CSF cortisol levels in delirium. In this pilot study we acquired CSF specimens at the onset of spinal anaesthesia in patients undergoing hip fracture surgery, and compared CSF and plasma cortisol levels in delirium cases versus controls.

Findings

Delirium assessments were performed the evening before or on the morning of operation with a standard battery comprising cognitive tests, mental status assessments and the Confusion Assessment Method. CSF and plasma samples were obtained at the onset of the operation and cortisol levels measured. Twenty patients (15 female, 5 male) aged 62 - 93 years were studied. Seven patients were diagnosed with delirium. The mean ages of cases (81.4 (SD 7.2)) and controls (80.5 (SD 8.7)) were not significantly different (p = 0.88). The median (interquartile range) CSF cortisol levels were significantly higher in cases (63.9 (40.4-102.1) nmol/L) than controls (31.4 (21.7-43.3) nmol/L; Mann-Whitney U, p = 0.029). The median (interquartile range) of plasma cortisol was also significantly higher in cases (968.8 (886.2-1394.4) nmol/L, than controls (809.4 (544.0-986.4) nmol/L; Mann Whitney U, p = 0.036).

Conclusions

These findings support an association between higher CSF cortisol levels and delirium. This extends previous findings linking higher plasma cortisol and delirium, and suggests that more definitive studies of the relationship between cortisol levels and delirium are now required.

Neurobiology of cognitive disorders

PURPOSE OF REVIEW

Neurodegenerative brain diseases, including Alzheimer's disease, frontotemporal degeneration and Lewy body disease, are the most frequent pathologies underlying cognitive disorders in old age. This review outlines recent advances in the understanding of key molecular mechanisms involved in these neurodegenerations, particularly with regard to the abnormal processing of proteins. The consequences of these novel insights for therapeutic interventions are also explained.

RECENT FINDINGS

Aberrant processing, misfolding, and subsequent deposition of amyloid beta protein, TAU, alpha-synuclein, and TDP-43 are key events in the pathological cascades of neurodegenerations leading to cognitive impairment and dementia. The nonpolymerized, oligomeric forms of these proteins have neurotoxic properties including the disruption of synaptic function and the induction of oxidative stress. The aggregation and deposition of these proteins may represent a neuronal repair mechanism which ultimately worsens the deleterious effects of the preaggregated forms. Novel disease-modifying treatment strategies aim at down-regulating protein production, inhibiting polymerization, or removing preaggregated forms of the proteins from the brain.

SUMMARY

Recent research has elucidated important molecular events in neurodegenerative diseases upstream of the aggregation and deposition of proteins which forms their histopathological hallmarks. These insights translate into novel therapeutic strategies which are currently evaluated in clinical trials.

Diagnostic considerations regarding pediatric delirium: a review and a proposal for an algorithm for pediatric intensive care units

CONTEXT

If delirium is not diagnosed, it is unlikely that any effort will be made to reverse it. Given evidence for under-diagnosis, tools that aid recognition are required.

OBJECTIVE

Relating three presentations of pediatric delirium (PD) to standard criteria and developing a diagnostic algorithm.

RESULTS

Delirium-inducing factors, disturbance of consciousness and inattention are common in PICU patients: a pre-delirious state is present in most. An algorithm is introduced, containing (1) evaluation of the sedation-agitation level, (2) psychometric assessment of behavior and (3) opinion of the caregivers.

DISCUSSION

It may be argued that the behavioral focus of the algorithm would benefit from the inclusion of neurocognitive measures.

LIMITATIONS

No sufficiently validated diagnostic instrument covering the entire algorithm is available yet.

CONCLUSION

This is the first proposal for a PD diagnostic algorithm. Given the high prevalence of predelirious states at the PICU, daily evaluation is mandatory. Future algorithmic refinement is urgently required.

Impact of delirium on short-term mortality in elderly inpatients: a prospective cohort study

BACKGROUND

Delirium is an important problem especially in older medical inpatients.

OBJECTIVE

The authors asked whether delirium and its duration are associated with higher mortality in a 3-month follow-up period.

METHOD

In this prospective cohort study, inpatients age 65 and older were assessed every 48 hours with the Confusion Assessment Method.

RESULTS

Of 542 patients enrolled, 192 (35.4%) developed delirium. After 3 months, mortality in the delirium cohort was 25.9%, and in the nondelirium cohort was 5.8%. Delirium was independently associated with mortality, and increased by 11% for every 48 hours of delirium.

CONCLUSION

Delirium and increased delirium durations are significantly associated with higher mortality.

Delirium in elderly adults: diagnosis, prevention and treatment

Delirium is a common and serious acute neuropsychiatric syndrome with core features of inattention and global cognitive dysfunction. The etiologies of delirium are diverse and multifactorial and often reflect the pathophysiological consequences of an acute medical illness, medical complication or drug intoxication. Delirium can have a widely variable presentation, and is often missed and underdiagnosed as a result. At present, the diagnosis of delirium is clinically based and depends on the presence or absence of certain features. Management strategies for delirium are focused on prevention and symptom management. This article reviews current clinical practice in delirium in elderly individuals, including the diagnosis, treatment, outcomes and economic impact of this syndrome. Areas of future research are also discussed.

Delirium in elderly adults: diagnosis, prevention and treatment

Delirium is a common and serious acute neuropsychiatric syndrome with core features of inattention and global cognitive dysfunction. The etiologies of delirium are diverse and multifactorial and often reflect the pathophysiological consequences of an acute medical illness, medical complication or drug intoxication. Delirium can have a widely variable presentation, and is often missed and underdiagnosed as a result. At present, the diagnosis of delirium is clinically based and depends on the presence or absence of certain features. Management strategies for delirium are focused on prevention and symptom management. This article reviews current clinical practice in delirium in elderly individuals, including the diagnosis, treatment, outcomes and economic impact of this syndrome. Areas of future research are also discussed.

Markers of cerebral damage during delirium in elderly patients with hip fracture

Background

S100B protein and Neuron Specific Enolase (NSE) can increase due to brain cell damage and/or increased permeability of the blood-brain-barrier. Elevation of these proteins has been shown after various neurological diseases with cognitive dysfunction. Delirium is characterized by temporal cognitive deficits and is an important risk factor for dementia. The aim of this study was to compare the level of S100B and NSE of patients before, during and after delirium with patients without delirium and investigate the possible associations with different subtypes of delirium.

Methods

The study population were patients aged 65 years or more acutely admitted after hip fracture. Delirium was diagnosed by the Confusion Assessment Method and the subtype by Delirium Symptom interview. In maximal four serum samples per patient S100B and NSE levels were determined by electrochemiluminescence immunoassay.

Results

Of 120 included patients with mean age 83.9 years, 62 experienced delirium. Delirious patients had more frequently pre-existing cognitive impairment (67% vs. 18%, p < 0.001). Comparing the first samples during delirium to samples of non-delirious patients, a difference was observed in S100B (median 0.16 versus 0.10 μg/L, p = < 0.001), but not in NSE (median 11.7 versus 11.7 ng/L, p = 0.97). Delirious state (before, during, after) (p < 0.001), day of blood withdrawal (p < 0.001), pre- or postoperative status (p = 0.001) and type of fracture (p = 0.036) were all associated with S100B level. The highest S100B levels were found 'during' delirium. S100B levels 'before' and 'after' delirium were still higher than those from 'non-delirious' patients. No significant difference in S100B (p = 0.43) or NSE levels (p = 0.41) was seen between the hyperactive, hypoactive and mixed subtype of delirium.

Conclusion

Delirium was associated with increased level of S100B which could indicate cerebral damage either due to delirium or leading to delirium. The possible association between higher levels of S100B during delirium and the higher risk of developing dementia after delirium is an interesting field for future research. More studies are needed to elucidate the role of S100B proteins in the pathophysiological pathway leading to delirium and to investigate its possibility as biomarker for delirium.

Delirium and long-term cognitive impairment

Delirium is a severe, acute neuropsychiatric syndrome that is highly prevalent in acute hospital populations. Delirium has noticeable effects on length of hospitalization, cost of care, mortality and morbidity. In addition to these well-established adverse consequences, there is increasing evidence linking delirium and a higher risk of long-term cognitive impairment (LTCI), including dementia. A prior review (Jackson, Gordon, Hart, Hopkins, & Ely, 2004), in which nine studies (total N = 1,885, years 1989-2003) were considered, concluded that there was evidence for an association between delirium and LTCI. Here we provide a review of studies published since Jackson's review. We included nine reports, with a total of 2,025 patients. The studies show diverse sample sizes, methodologies, designs and patient populations. However, taken together, the results of these new studies broadly confirm that there is a link between delirium and LTCI. We go on to discuss putative mechanisms and explanations. These include (1) delirium as a marker of chronic progressive pathology, but unrelated to any progression, (2) delirium as a consequence of acute brain damage which is also responsible for a 'single hit' or triggering of active processes causing LTCI, (3) delirium itself as a cause of LTCI, and (4) drug treatment of delirium or other conditions as a cause of LTCI. We conclude with suggestions for future research.