Cholinergic deficiency hypothesis in delirium: a synthesis of current evidence

Delirium from the gliocentric perspective

Delirium is an acute state marked by disturbances in cognition, attention, memory, perception, and sleep-wake cycle which is common in elderly. Others have shown an association between delirium and increased mortality, length of hospitalization, cost, and discharge to extended stay facilities. Until recently it was not known that after an episode of delirium in elderly, there is a 63% probability of developing dementia at 48 months compared to 8% in patients without delirium. Currently there are no preventive therapies for delirium, thus elucidation of cellular and molecular underpinnings of this condition may lead to the development of early interventions and thus prevent permanent cognitive damage. In this article we make the case for the role of glia in the pathophysiology of delirium and describe an astrocyte-dependent central and peripheral cholinergic anti-inflammatory shield which may be disabled by astrocytic pathology, leading to neuroinflammation and delirium. We also touch on the role of glia in information processing and neuroimaging.

Review of delirium in patients with Parkinson's disease

Parkinson's disease (PD) is common and has a number of associated neuropsychiatric disturbances. Of these, delirium has historically been under-recognised. Delirium is an acute disturbance of attention and awareness that fluctuates, and is accompanied by an additional disturbance of cognition. As delirium is known to carry a particularly poor prognosis in terms of morbidity and mortality, and the relationship between delirium and dementia is becoming better defined, we completed a literature review of delirium in the context of PD. A literature search was completed using the databases PubMed, Embase and Ovid Medline. PubMed (1945-2014) was searched in September 2014; Embase (1974-2014); and Ovid Medline (1946-2014) in October 2014. The search terms 'delirium' and 'Parkinsons' in combination were used. Large studies using a robust definition of delirium were lacking in PD. There is the suggestion that PD is a risk factor for delirium and that delirium negatively impacts upon the motor symptom trajectory. Deficits in the neurotransmitters dopamine and acetylcholine are implicated in the pathophysiology of delirium in PD. Systemic inflammation also appears to have a role. Treatment of delirium in PD should include medication review and cautious use of atypical antipsychotics where pharmacological treatment is indicated. Of the atypical antipsychotics studied, quetiapine has the least extrapyramidal side effects. Evidence suggests a specific link between delirium and PD but well-designed clinical studies to evaluate the prevalence, impact and treatment of delirium in PD are required. Given the potential to improve outcomes through delirium prevention we conclude that delirium in PD is an area worthy of further study.

Management of delirium in palliative care: a review

Delirium is a complex but common disorder in palliative care with a prevalence between 13 and 88 % but a particular frequency at the end of life (terminal delirium). By reviewing the most relevant studies (MEDLINE, EMBASE, PsycLit, PsycInfo, Cochrane Library), a correct assessment to make the diagnosis (e.g., DSM-5, delirium assessment tools), the identification of the possible etiological factors, and the application of multicomponent and integrated interventions were reported as the correct steps to effectively manage delirium in palliative care. In terms of medications, both conventional (e.g., haloperidol) and atypical antipsychotics (e.g., olanzapine, risperidone, quetiapine, aripiprazole) were shown to be equally effective in the treatment of delirium. No recommendation was possible in palliative care regarding the use of other drugs (e.g., α-2 receptors agonists, psychostimulants, cholinesterase inhibitors, melatonergic drugs). Non-pharmacological interventions (e.g., behavioral and educational) were also shown to be important in the management of delirium. More research is necessary to clarify how to more thoroughly manage delirium in palliative care.

Recent progress in research of postoperative delirium after abdominal surgery

Postoperative delirium (POD) is a common acute cerebral syndrome after abdominal surgery, with disturbance of consciousness, cognition and attention as the main clinical manifestations, found mostly in elderly male patients. POD often increases mortality dramatically and prolongs the length of hospital stay. There are many factors responsible for the occurrence of POD, such as age, underlying diseases and antipsychotic drugs. Due to the complex onset of the disease, multicomponent intervention strategies have been recommended and proved effective. In contrast, there has been no evidence that pharmacological prevention or therapy could reduce the incidence or shorten the duration of POD. This paper reviews the recent progress in research of postoperative delirium after abdominal surgery with regards to its mechanism, risk factors, prevention and treatment.

Delirium and dementia with Lewy bodies: distinct diagnoses or part of the same spectrum?

Dementia with Lewy bodies (DLB) is recognised as the second most common form of dementia in older people. Delirium is a condition of acute brain dysfunction for which a pre-existing diagnosis of dementia is a risk factor. Conversely delirium is associated with an increased risk of developing dementia. The reasons for this bidirectional relationship are not well understood. Our aim was to review possible similarities in the clinical presentation and pathophysiology between delirium and DLB, and explore possible links between these diagnoses. A systematic search using Medline, Embase and Psychinfo was performed. References were scanned for relevant articles, supplemented by articles identified from reference lists and those known to the authors. 94 articles were selected for inclusion in the review. Delirium and DLB share a number of clinical similarities, including global impairment of cognition, fluctuations in attention and perceptual abnormalities. Delirium is a frequent presenting feature of DLB. In terms of pathophysiological mechanisms, cholinergic dysfunction and genetics may provide a common link. Neuroimaging studies suggest a brain vulnerability in delirium which may also occur in dementia. The basal ganglia, which play a key role in DLB, have also been implicated in delirium. The role of Cerebrospinal fluid (CSF) and serum biomarkers for both diagnoses is an interesting area although some results are conflicting and further work in this area is needed. Delirium and DLB share a number of features and we hypothesise that delirium may, in some cases, represent early or 'prodromal' DLB. Further research is needed to test the novel hypothesis that delirium may be an early marker for future DLB, which would aid early diagnosis of DLB and identify those at high risk.

Relationship between cobalamin deficiency and delirium in elderly patients undergoing cardiac surgery

BACKGROUND

Delirium is common after cardiac surgery and is independently associated with increased morbidity, mortality, prolonged hospital stays, and higher costs. Cobalamin (vitamin B12) deficiency is a common cause of neuropsychiatric symptoms and affects up to 40% of elderly people. The relationship between cobalamin deficiency and the occurrence of delirium after cardiac surgery has not been examined in previous studies. We examined the relationship between cobalamin deficiency and delirium in elderly patients undergoing coronary artery bypass grafting (CABG) surgery.

MATERIAL AND METHODS

A total of 100 patients with cobalamin deficiency undergoing CABG were enrolled in this retrospective study. Control group comprised 100 patients without cobalamin deficiency undergoing CABG. Patients aged 65 years or over were included. Diagnosis of delirium was made using Intensive Care Delirium Screening Checklist. Delirium severity was measured using the Delirium Rating Scale-revised-98.

RESULTS

Patients with cobalamin deficiency had a significantly higher incidence of delirium (42% vs 26%; P=0.017) and higher delirium severity scores (16.5±2.9 vs 15.03±2.48; P=0.034) than patients without cobalamin deficiency. Cobalamin levels were significantly lower in patients with delirium than patients without delirium (P=0.004). Delirium severity score showed a moderate correlation with cobalamin levels (ρ=-0.27; P=0.024). Logistic regression analysis demonstrated that cobalamin deficiency was independently associated with postoperative delirium (OR 1.93, 95% CI 1.03-3.6, P=0.038).

CONCLUSION

The results of our study suggest that cobalamin deficiency may be associated with increased risk of delirium in patients undergoing CABG. In addition, we found that preoperative cobalamin levels were associated with the severity of delirium. This report highlights the importance of investigation for cobalamin deficiency in patients undergoing cardiac surgery, especially in the elderly.

The attributable mortality of delirium in critically ill patients: prospective cohort study

OBJECTIVE

To determine the attributable mortality caused by delirium in critically ill patients.

DESIGN

Prospective cohort study.

SETTING

32 mixed bed intensive care unit in the Netherlands, January 2011 to July 2013.

PARTICIPANTS

1112 consecutive adults admitted to an intensive care unit for a minimum of 24 hours.

EXPOSURES

Trained observers evaluated delirium daily using a validated protocol. Logistic regression and competing risks survival analyses were used to adjust for baseline variables and a marginal structural model analysis to adjust for confounding by evolution of disease severity before the onset of delirium.

MAIN OUTCOME MEASURE

Mortality during admission to an intensive care unit.

RESULTS

Among 1112 evaluated patients, 558 (50.2%) developed at least one episode of delirium, with a median duration of 3 days (interquartile range 2-7 days). Crude mortality was 94/558 (17%) in patients with delirium compared with 40/554 (7%) in patients without delirium (P<0.001). Delirium was significantly associated with mortality in the multivariable logistic regression analysis (odds ratio 1.77, 95% confidence interval 1.15 to 2.72) and survival analysis (subdistribution hazard ratio 2.08, 95% confidence interval 1.40 to 3.09). However, the association disappeared after adjustment for time varying confounders in the marginal structural model (subdistribution hazard ratio 1.19, 95% confidence interval 0.75 to 1.89). Using this approach, only 7.2% (95% confidence interval -7.5% to 19.5%) of deaths in the intensive care unit were attributable to delirium, with an absolute mortality excess in patients with delirium of 0.9% (95% confidence interval -0.9% to 2.3%) by day 30. In post hoc analyses, however, delirium that persisted for two days or more remained associated with a 2.0% (95% confidence interval 1.2% to 2.8%) absolute mortality increase. Furthermore, competing risk analysis showed that delirium of any duration was associated with a significantly reduced rate of discharge from the intensive care unit (cause specific hazard ratio 0.65, 95% confidence interval 0.55 to 0.76).

CONCLUSIONS

Overall, delirium prolongs admission in the intensive care unit but does not cause death in critically ill patients. Future studies should focus on episodes of persistent delirium and its long term sequelae rather than on acute mortality.Trial registration Clinicaltrials.gov NCT01905033.

Dexmedetomidine reduces the risk of delirium, agitation and confusion in critically Ill patients: a meta-analysis of randomized controlled trials

OBJECTIVES

Delirium frequently is observed in critically ill patients in the intensive care unit (ICU) and is associated strongly with a poor outcome. Dexmedetomidine seems to reduce time to extubation and ICU stay without detrimental effects on mortality. The objective of the authors' study was to evaluate the effect of this drug on delirium, agitation, and confusion in the ICU setting.

DESIGN

Meta-analysis of all the randomized clinical trials ever performed on dexmedetomidine versus any comparator in the ICU setting.

SETTING

Intensive care units.

PARTICIPANTS

Critically ill patients.

INTERVENTIONS

None

MEASUREMENTS AND MAIN RESULTS

Pertinent studies were independently searched in BioMedCentral, PubMed, Embase, and the Cochrane Central Register of clinical trials. Primary endpoint was the rate of delirium, including the adverse events, agitation and confusion. The 13 included manuscripts (14 trials) randomized 3,029 patients. Overall analysis showed that the use of dexmedetomidine was associated with significant reductions in the incidence of delirium, agitation and confusion (298/1,565 [19%] in the dexmedetomidine group v 337/1,464 [23%] in the control group, RR = 0.68 [0.49 to 0.96], p = 0.03). Results were confirmed in subanalyses performed on patients undergoing noninvasive ventilation (1/53 [2%] in the dexmedetomidine group v 7/49 [14%] in the control group, RR=0.18 [0.03 to 1.01], p = 0.05), receiving midazolam as a comparator (268/1,164 [23%] in the dexmedetomidine group v 277/1,025 [27%] in the control group, RR = 0.68 [0.47 to 1.00], p = 0.05) and in general ICU setting patients (204/688 [30%] in the dexmedetomidine group v 204/560 [36%] in the control group, RR = 0.68 [0.45 to 0.81], p < 0.01).

CONCLUSIONS

This meta-analysis of randomized controlled studies suggests that dexmedetomidine could help to reduce delirium in critically ill patients.

Cigarette smoking as a risk factor for delirium in hospitalized and intensive care unit patients. A systematic review

BACKGROUND

Active smokers are prevalent in hospitalized and critically ill patients. Cigarette smoking and nicotine withdrawal may increase delirium in these populations. This systematic review aims to determine whether active cigarette smoking increases the risk for delirium in hospitalized and intensive care unit (ICU) patients.

METHODS

A systematic search of English-, Spanish-, and French-language articles published from 1966 to April 2013 was performed. Studies were included if they measured cigarette smoking as a risk factor and delirium as an outcome in adult hospitalized or ICU patients. Methodologic quality of studies was assessed using both the validated Newcastle Ottawa Scale and an additional evidence-based quality rating scale.

RESULTS

A total of 14 cohort studies of surgical and ICU populations were included in the review. No studies in non-ICU inpatients were identified. The incidence of delirium ranged from 9 to 52%, and the prevalence of active smokers ranged from 9 to 44%. The quality of assessment for active smoking varied widely. None of the studies used biochemical measures to determine cigarette smoke exposure. Of the six studies restricting the smoking group to active smokers only, active smoking was independently associated with delirium in one study, trended toward an association in one study, and showed a dose response in one study. Quantitative summary measures were not calculated due to study heterogeneity and missing data.

CONCLUSIONS

There is currently insufficient evidence to determine if cigarette smoking is a risk factor for delirium. Future studies should consider using biochemical measures of cigarette smoke exposure to objectively quantify smoking behavior.

Electroconvulsive therapy as a treatment for protracted refractory delirium in the intensive care unit--five cases and a review

PURPOSE

Delirium in the intensive care unit (ICU) is conventionally treated pharmacologically but can progress into a protracted state refractory to medical treatment--a potentially life-threatening condition in itself.

METHODS

We treated 5 cases of severe protracted delirium in our ICU with electroconvulsive therapy (ECT) after failure of conventional medical therapy.

RESULTS

The delirious state of long standing agitation, anxiety, and discomfort was controlled in all patients. Electroconvulsive therapy was effective in controlling delirium in 4 patients. The last patient became calm, relieved of stress, and able to cooperate with the ventilator but remained in a state of posttraumatic amnesia after a head trauma.

CONCLUSION

Although controversial, ECT is nevertheless recognized as an efficient and safe treatment for various psychiatric illnesses including delirium. Considering the significantly increased mortality and severe cognitive decline associated with delirium in the ICU, we find ECT to be a valuable treatment option for this vulnerable patient population. It can be considered when agitation cannot be controlled with medical treatment, when agitation and delirium make weaning impossible, or prolonged deep sedation the only alternative.

Protective effects of bajijiasu in a rat model of Aβ₂₅₋₃₅-induced neurotoxicity

ETHNOPHARMACOLOGICAL RELEVENCE

Neurodegenerative diseases (NDs) caused by neurons and/or myelin loss lead to devastating effects on patients׳ lives. Although the causes of such complex diseases have not yet been fully elucidated, oxidative stress, mitochondrial and energy metabolism dysfunction, excitotoxicity, inflammation, and apoptosis have been recognized as influential factors. Current therapies that were designed to address only a single target are unable to mitigate or prevent disease progression, and disease-modifying drugs are desperately needed, and Chinese herbs will be a good choice for screening the potential drugs. Previous studies have shown that bajijiasu, a dimeric fructose isolated from Morinda officinalis radix which was used frequently as a tonifying and replenishing natural herb medicine in traditional Chinese medicine clinic practice, can prevent ischemia-induced neuronal damage or death.

MATERIALS AND METHODS

In order to investigate whether bajijiasu protects against beta-amyloid (Aβ₂₅₋₃₅)-induced neurotoxicity in rats and explore the underlying mechanisms of bajijiasu in vivo, we prepared an Alzheimer׳s disease (AD) model by injecting Aβ25-35 into the bilateral CA1 region of rat hippocampus and treated a subset with oral bajijiasu. We observed the effects on learning and memory, antioxidant levels, energy metabolism, neurotransmitter levels, and neuronal apoptosis.

RESULTS

Bajijiasu ameliorated Aβ-induced learning and memory dysfunction, enhanced antioxidative activity and energy metabolism, and attenuated cholinergic system damage. Our findings suggest that bajijiasu can enhance antioxidant capacity and prevent free radical damage. It can also enhance energy metabolism and monoamine neurotransmitter levels and inhibit neuronal apoptosis.

CONCLUSION

The results provide a scientific foundation for the use of Morinda officinalis and its constituents in the treatment of various AD. Future studies will assess the multi-target activity of the drug for the treatment of AD.

The association between C-reactive protein and delirium in 710 acute elderly hospital admissions

BACKGROUND

Delirium is a common neuropsychiatric syndrome associated with poor outcomes. Evidence supports a neuroinflammatory etiology, but the role of the inflammatory marker C-reactive protein (C-RP) remains unclear. We investigated the relationship between C-RP and delirium and its severity as well as interaction with medical diagnosis.

METHODS

From an existing database (710 patients over 70 years old admitted to a Medical Acute Admissions Unit) we analyzed data which included C-RP levels, delirium (using the Confusion Assessment Method), and other clinical and demographic factors. Primary diagnoses were grouped (cardiovascular, musculoskeletal, infection, metabolic, and other).

RESULTS

There was a strong association between elevated C-RP and delirium (t = 5.09; p < 0.001), independent of other potential risk factors for delirium (odds ratio (OR) = 1.32 (95% CI: 1.10-1.58) p = 0.003). There was no significant association between C-RP and delirium severity, and between C-RP and delirium in the populations with cardiovascular disease, infection upon admission, or from the metabolic group despite an OR of 2.24 (95% CI: 0.92-5.45). There was an association in the musculoskeletal group (OR 2.19 (95% CI: 1.19-4.02)).

CONCLUSIONS

There is an association between elevated C-RP and delirium. This is strongest in patients admitted with musculoskeletal disease but not in others, implying that C-RP is involved in the genesis of delirium in musculoskeletal disease, but that other factors or processes may be more important in those with cardiovascular disease or infection.

Delirium in the cardiac surgical ICU

PURPOSE OF REVIEW

Evidence is emerging that delirium is associated with both short-term and long-term morbidity and mortality. This review highlights the epidemiology, outcomes, prevention and treatment strategies associated with delirium after cardiac surgery.

RECENT FINDINGS

The incidence of delirium after cardiac surgery is estimated to be 26-52%, with a significant percentage being hypoactive delirium. It is clear that without an appropriate structured test for delirium, the incidence of delirium will be underrecognized clinically. Delirium after cardiac surgery is associated with poor outcomes, including increased long-term mortality, increased risk of stroke, poor functional status, increased hospital readmissions and substantial cognitive dysfunction for 1 year following surgery. The effectiveness of prophylactic antipsychotics to reduce the risk of delirium is controversial, with data from recent small studies in noncardiac surgery potentially showing a benefit. Although antipsychotic medications are often used to treat delirium, the evidence that antipsychotics in cardiac surgery patients reduce duration of delirium or improve long-term outcomes following delirium is poor.

SUMMARY

Clinicians in the ICU must recognize the impact of delirium in predicting long-term outcomes for patients. Further research is needed in determining interventions that will be effective in preventing and treating delirium in cardiac surgical setting.

Sleep disorders and acute nocturnal delirium in the elderly: a comorbidity not to be overlooked

Delirium is a disturbance of consciousness and cognition that results in a confusional state. It tends to fluctuate in intensity and is often observed in older patients. Sleep is a window of vulnerability for the occurrence of delirium and sleep disorders can play a role in its appearance. In particular, delirious episodes have been associated with obstructive sleep apnoea syndrome, which is reported to be frequent in the elderly. Hereby, we present a case-report documenting the sudden onset of a confusional state triggered by obstructive sleep apnoea-induced arousal, together with a review of the literature on the topic. We emphasise that, among the many pathogenic factors implicated in delirium, it is worth considering the possible link between nocturnal delirium and the occurrence of impaired arousals. Indeed, the complex confusional manifestations of delirium could be due, in part, to persistence of dysfunctional sleep activity resulting in an inability to sustain full arousal during behavioural wakefulness. Arousals can be triggered by sleep disturbances or other medical conditions. Clinicians should be aware that older patients may present disordered sleep patterns, and make investigation of sleep patterns and disorders potentially affecting sleep continuity a key part of their clinical workup, especially in the presence of cognitive comorbidities. Correct diagnosis and optimal treatment of sleep disorders and disrupted sleep can have a significant impact in the elderly, improving sleep quality and reducing the occurrence of abnormal sleep-related behaviours.

Delirium in elderly people

Delirium is an acute disorder of attention and cognition in elderly people (ie, those aged 65 years or older) that is common, serious, costly, under-recognised, and often fatal. A formal cognitive assessment and history of acute onset of symptoms are necessary for diagnosis. In view of the complex multifactorial causes of delirium, multicomponent non-pharmacological risk factor approaches are the most effective strategy for prevention. No convincing evidence shows that pharmacological prevention or treatment is effective. Drug reduction for sedation and analgesia and non-pharmacological approaches are recommended. Delirium offers opportunities to elucidate brain pathophysiology--it serves both as a marker of brain vulnerability with decreased reserve and as a potential mechanism for permanent cognitive damage. As a potent indicator of patients' safety, delirium provides a target for system-wide process improvements. Public health priorities include improvements in coding, reimbursement from insurers, and research funding, and widespread education for clinicians and the public about the importance of delirium.

Sepsis Associated Encephalopathy

Sepsis associated encephalopathy (SAE) is a common but poorly understood neurological complication of sepsis. It is characterized by diffuse brain dysfunction secondary to infection elsewhere in the body without overt CNS infection. The pathophysiology of SAE is complex and multifactorial including a number of intertwined mechanisms such as vascular damage, endothelial activation, breakdown of the blood brain barrier, altered brain signaling, brain inflammation, and apoptosis. Clinical presentation of SAE may range from mild symptoms such as malaise and concentration deficits to deep coma. The evaluation of cognitive dysfunction is made difficult by the absence of any specific investigations or biomarkers and the common use of sedation in critically ill patients. SAE thus remains diagnosis of exclusion which can only be made after ruling out other causes of altered mentation in a febrile, critically ill patient by appropriate investigations. In spite of high mortality rate, management of SAE is limited to treatment of the underlying infection and symptomatic treatment for delirium and seizures. It is important to be aware of this condition because SAE may present in early stages of sepsis, even before the diagnostic criteria for sepsis can be met. This review discusses the diagnostic approach to patients with SAE along with its epidemiology, pathophysiology, clinical presentation, and differential diagnosis.

Intensive care unit delirium: a review of the literature

PURPOSE

The recent literature regarding intensive care unit (ICU) delirium and updated clinical practice guidelines are reviewed.

SUMMARY

Recent studies show that ICU delirium in critically ill patients is an independent predictor of higher mortality, longer ICU and hospital stay, and is associated with multiple clinical complications. Delirium has been reported to occur in greater than 80% of hospitalized critically ill patients, yet it remains an underdiagnosed condition. Several subtypes of delirium have been identified including hypoactive, hyperactive, and mixed presentation. Although the exact mechanism is unknown, several factors are thought to interact to cause delirium. Multiple risk factors related to medications, acute illness, the environment, and patient characteristics may contribute to the development of delirium. Practical bedside screening tools have been validated and are recommended to identify ICU patients with delirium. Nonpharmacologic interventions such as early mobilization have resulted in better functional outcomes, decreased incidence and duration of delirium, and more ventilator-free days. Data supporting pharmacologic treatments are limited.

CONCLUSION

Clinicians should become familiar with tools to identify delirium in order to initiate treatment and remove mitigating factors early in hospitalization to prevent delirium. Pharmacists are in a unique position to reduce delirium through minimization of medication-related risk factors and development of protocols.

Hypovitaminosis D in Delirium: a Retrospective Cross-sectional Study

Background

As vitamin D may have a neuroprotective effect, the authors studied the association of biomarkers of vitamin D status and delirium to see if low vitamin D status was common in delirium cases.

Methods

Biochemical measures of vitamin D (25-hydroxyvitamin D [25-OHD]) and calcium metabolism were used in this retrospective cross-sectional analysis of adult in-patients with delirium, admitted at three Canadian academic hospitals from January 2011 to July 2012. Primary outcome was to determine estimates of the prevalence of hypovitaminosis D in this group in whom vitamin D was checked.

Results

Seventy-one (5.8%) out of 1,232 delirium inpatients had their vitamin D measured. Thirty-nine (55%) showed vitamin D insufficiency (25-OHD of 25-75 nmol/L) and 8 (11%) showed vitamin D deficiency (25-OHD < 25 nmol/L). Mean serum 25-OHD levels were lower in males (57.1±7.7 nmol/L) than in females (78.2±6.1 nmol/L), p = .01, even when controlled for age and season. Men were younger than the women (74.4±2.3 vs. 82.4±1.7, p = .005). Mean age was 78.7±1.5 years, and 33 (47%) were male.

Conclusions

Although vitamin D is rarely checked during delirium workup and/or management, high rates of hypovitaminosis D were found to be common in the delirium in-patients in whom it was checked. Larger studies would be needed to estimate the prevalence of hypovitaminosis D in delirium and whether hypovitaminosis D plays a role in the pathogenesis of delirium.

Neuropathogenesis of delirium: review of current etiologic theories and common pathways

Delirium is a neurobehavioral syndrome caused by dysregulation of neuronal activity secondary to systemic disturbances. Over time, a number of theories have been proposed in an attempt to explain the processes leading to the development of delirium. Each proposed theory has focused on a specific mechanism or pathologic process (e.g., dopamine excess or acetylcholine deficiency theories), observational and experiential evidence (e.g., sleep deprivation, aging), or empirical data (e.g., specific pharmacologic agents' association with postoperative delirium, intraoperative hypoxia). This article represents a review of published literature and summarizes the top seven proposed theories and their interrelation. This review includes the "neuroinflammatory," "neuronal aging," "oxidative stress," "neurotransmitter deficiency," "neuroendocrine," "diurnal dysregulation," and "network disconnectivity" hypotheses. Most of these theories are complementary, rather than competing, with many areas of intersection and reciprocal influence. The literature suggests that many factors or mechanisms included in these theories lead to a final common outcome associated with an alteration in neurotransmitter synthesis, function, and/or availability that mediates the complex behavioral and cognitive changes observed in delirium. In general, the most commonly described neurotransmitter changes associated with delirium include deficiencies in acetylcholine and/or melatonin availability; excess in dopamine, norepinephrine, and/or glutamate release; and variable alterations (e.g., either a decreased or increased activity, depending on delirium presentation and cause) in serotonin, histamine, and/or γ-aminobutyric acid. In the end, it is unlikely that any one of these theories is fully capable of explaining the etiology or phenomenologic manifestations of delirium but rather that two or more of these, if not all, act together to lead to the biochemical derangement and, ultimately, to the complex cognitive and behavioral changes characteristic of delirium.

Atypical antipsychotics in the treatment of delirium

The aim of this study was to review the efficacy and safety of atypical antipsychotics, comparing within class, placebo, or compared to another active treatment for delirium. A literature search was conducted using PubMed, EMBASE, and the Cochrane database (1 January 1990-5 November 2012). Selection criteria for review were prospective, controlled studies (comparison studies), using validated delirium rating scales as outcome measures. A total of six prospective, randomized controlled studies were included in the review. It was found that atypical antipsychotics are effective and safe in treating delirium, even though there seemed to be no difference between each agent. In particular, comparison studies with haloperidol showed that the efficacy of atypical antipsychotics was similar to that of low-dose haloperidol. It was concluded that atypical antipsychotics appear to be effective and tolerable in the management of delirium, even though the evidence is limited.

Symptom communication during critical illness: the impact of age, delirium, and delirium presentation

Symptom communication is integral to quality patient care. Communication between patients and nurses in the intensive care unit (ICU) is complicated by oral or endotracheal intubation and fluctuating neurocognitive status or delirium. We report the (a) prevalence of delirium and its subtypes in non-vocal, mechanically ventilated, critically ill patients; (b) impact of age on delirium; and (c) influence of delirium and age on symptom communication. Videorecorded interactions between patients (N = 89) and nurses (N = 30) were analyzed for evidence of patient symptom communication at four time points across 2 consecutive days. Delirium was measured at enrollment and following sessions. Delirium prevalence was 23.6% at enrollment and 28.7% across sessions. Participants age >60 were more likely to be delirious on enrollment and during observational sessions. Delirium was associated with self-report of pain, drowsiness, and feeling cold. Patients were significantly less likely to initiate symptom communication when delirious. Symptom identification should be carefully undertaken in older adults with or without delirium.

Understanding brain dysfunction in sepsis

Sepsis often is characterized by an acute brain dysfunction, which is associated with increased morbidity and mortality. Its pathophysiology is highly complex, resulting from both inflammatory and noninflammatory processes, which may induce significant alterations in vulnerable areas of the brain. Important mechanisms include excessive microglial activation, impaired cerebral perfusion, blood-brain-barrier dysfunction, and altered neurotransmission. Systemic insults, such as prolonged inflammation, severe hypoxemia, and persistent hyperglycemia also may contribute to aggravate sepsis-induced brain dysfunction or injury. The diagnosis of brain dysfunction in sepsis relies essentially on neurological examination and neurological tests, such as EEG and neuroimaging. A brain MRI should be considered in case of persistent brain dysfunction after control of sepsis and exclusion of major confounding factors. Recent MRI studies suggest that septic shock can be associated with acute cerebrovascular lesions and white matter abnormalities. Currently, the management of brain dysfunction mainly consists of control of sepsis and prevention of all aggravating factors, including metabolic disturbances, drug overdoses, anticholinergic medications, withdrawal syndromes, and Wernicke's encephalopathy. Modulation of microglial activation, prevention of blood-brain-barrier alterations, and use of antioxidants represent relevant therapeutic targets that may impact significantly on neurologic outcomes. In the future, investigations in patients with sepsis should be undertaken to reduce the duration of brain dysfunction and to study the impact of this reduction on important health outcomes, including functional and cognitive status in survivors.

Association between intraoperative blood transfusions and early postoperative delirium in older adults

OBJECTIVES

To determine whether intraoperative blood transfusion, a known trigger and amplifier of inflammation, is an independent risk factor for early postoperative delirium (POD), an acute state of confusion with fluctuating consciousness and inattention after surgery, in older adults undergoing surgery.

DESIGN

Secondary analysis using a database created for a prospective cognitive outcomes study.

SETTING

University hospital.

PARTICIPANTS

Four hundred seventy-two individuals aged 65 and older undergoing major noncardiac surgery.

MEASUREMENTS

Perioperative data were examined for association with POD on the first postoperative day. Multivariable logistic regression analysis was conducted to determine whether intraoperative blood transfusion independently predicts POD after adjusting for covariates known to be associated with onset of delirium and blood transfusions.

RESULTS

One hundred thirty-seven individuals (29%) developed delirium on the first postoperative day. The multivariable logistic regression model identified age, sex, history of central nervous system disorder, preoperative cognitive dysfunction, and pain, as well as blood transfusions, as independent risk factors for POD. Intraoperative administration of more than 1,000 mL of red blood cells (RBCs) was the strongest predictor of POD on the first postoperative day (odds ratio = 3.68; 95% confidence interval = 1.32–10.94; P < .001).

CONCLUSION

Intraoperative blood transfusion of more than 1,000 mL of RBCs increases the risk of delirium on the first postoperative day in older adults undergoing noncardiac surgery.

Delirium after cardiac surgery: have we overlooked obstructive sleep apnea?

Obstructive sleep apnea is common in patients with cardiovascular disease. It is well known that cardiac surgery is a risk factor for delirium. Researchers have shown that obstructive sleep apnea is an independent risk factor for the occurrence of delirium. In this manuscript we speculate on how obstructive sleep apnea may increase the risk of delirium in patients with cardiac surgery. If this is found to be confirmed, we would have another target through which we can decrease the risk of delirium in this population.

Obstructive sleep apnea and delirium: exploring possible mechanisms

INTRODUCTION

Obstructive sleep apnea (OSA) is a medical disorder strongly associated with multiple comorbidities and postoperative complications. Current evidence suggests that OSA disturbs fundamental biochemical processes, leading to low-grade systemic inflammation and oxidative stress. Animal models have shown that OSA may lead to apoptosis of central neurons. In clinical studies, oxygen desaturation index and sleep fragmentation have been shown to be independently associated with cognitive dysfunction. Moreover, in several studies, patients with OSA were shown to have decreased brain activation in multiple brain areas.

OSA AND DELIRIUM

The possibility of an association between OSA and delirium has been highlighted in several case reports. The first prospective study of the possible link between apnea and delirium showed that the presence of OSA was independently associated with the occurrence of delirium after knee replacement surgery.

CONCLUSIONS

Therefore, we suggest that OSA should be considered as a risk factor for delirium, and clinicians should assess patients for OSA and related risk factors prior to surgery. However, further research is required to shed light on the mechanisms connecting these disorders and on whether the treatment of OSA affects the incidence of delirium.

Association of pre-operative brain pathology with post-operative delirium in a cohort of non-small cell lung cancer patients undergoing surgical resection

OBJECTIVE

Post-operative delirium is associated with pre-operative cognitive difficulties and diminished functional independence, both of which suggest that brain pathology may be present in affected individuals prior to surgery. Currently, there are few studies that have examined imaging correlates of post-operative delirium. To our knowledge, none have examined the association of delirium with existing structural pathology in pre-operative cancer patients. Here, we present a novel, retrospective strategy to assess pre-operative structural brain pathology and its association with post-operative delirium. Standard of care structural magnetic resonance imaging (MRIs) from a cohort of surgical candidates prior to surgery were analyzed for white matter hyperintensities and cerebral atrophy.

METHODS

We identified 23 non-small cell lung cancer patients with no evidence of metastases in the brain pre-operatively, through retrospective chart review, who met criteria for post-operative delirium within 4 days of surgery. 24 age- and gender-matched control subjects were identified for comparison to the delirium sample. T1 and fluid-attenuated inversion recovery sequences were collected from standard of care pre-operative MRI screening and assessed for white matter pathology and atrophy.

RESULTS

We found significant differences in white matter pathology between groups with the delirium group exhibiting significantly greater white matter pathology than the non-delirium group. Measure of cerebral atrophy demonstrated no significant difference between the delirium and non-delirium group.

CONCLUSIONS

In this preliminary study utilizing standard of care pre-operative brain MRIs for assessment of structural risk factors to delirium, we found white matter pathology to be a significant risk factor in post-operative delirium. Limitations and implications for further investigation are discussed.

Future directions of delirium research and management

Delirium is a prevalent organ dysfunction in critically ill patients associated with significant morbidity and mortality, requiring advancements in the clinical and research realms to improve patient outcomes. Increased clinical recognition and utilisation of delirium assessment tools, along with clarification of specific risk factors and presentations in varying patient populations, will be necessary in the future. To improve predictive models for outcomes, the continued development and implementation of delirium assessment tools and severity scoring systems will be required. The interplay between the pathophysiological pathways implicated in delirium and resulting clinical presentations and outcomes will need to guide the development of appropriate prevention and treatment protocols. Multicentre randomised controlled trials of interventional therapies will then need to be performed to test their ability to improve clinical outcomes. Physical and cognitive rehabilitation measures need to be further examined as additional means of improving outcomes from delirium in the hospital setting.

Pharmacologic prevention and treatment of delirium in critically ill and non-critically ill hospitalised patients: a review of data from prospective, randomised studies

Delirium occurs commonly in acutely ill hospitalised patients, particularly in the elderly or in cardiac or orthopaedic surgery patients, or those in intensive care units (ICUs). Delirium worsens outcome. Pharmaceutical agents such as antipsychotics and, in the critically ill, dexmedetomidine, are considered therapeutic despite uncertainty regarding their efficacy and safety. Using MEDLINE, we reviewed randomised controlled trials (RCTs) published between 1977 and April 2012 evaluating a pharmacologic intervention to prevent or treat delirium in critically ill and non-critically ill hospitalised patients. The number of prospective RCTs remains limited. Any conclusions about pharmacologic efficacy are limited by the small size of many studies, the inconsistency by which non-pharmacologic delirium prevention strategies were incorporated, the lack of a true placebo arm and a failure to incorporate ICU and non-ICU clinical outcomes. A research framework for future evaluation of the use of medications in both ICU and non-ICU is proposed.

A systematic review of amnestic and non-amnestic mild cognitive impairment induced by anticholinergic, antihistamine, GABAergic and opioid drugs

BACKGROUND

Mild cognitive deficits are experienced by 18% of community-dwelling older adults, many of whom do not progress to dementia. The effect of commonly used medication on subtle impairments in cognitive function may be under-recognized.

OBJECTIVE

The aim of the review was to examine the evidence attributing amnestic or non-amnestic cognitive impairment to the use of medication with anticholinergic, antihistamine, GABAergic or opioid effects.

METHODS

MEDLINE and EMBASE were searched for randomized, double-blind, placebo-controlled trials of adults without underlying central nervous system disorders who underwent detailed neuropsychological testing prior to and after oral administration of drugs affecting cholinergic, histaminergic, GABAergic or opioid receptor pathways. Seventy-eight studies were identified, reporting 162 trials testing medication from the four targeted drug classes. Two investigators independently appraised study quality and extracted relevant data on the occurrence of amnestic, non-amnestic or combined cognitive deficits induced by each drug class. Only trials using validated neuropsychological tests were included. Quality of the evidence for each drug class was assessed based on consistency of results across trials and the presence of a dose-response gradient.

RESULTS

In studies of short-, intermediate- and long-acting benzodiazepine drugs (n = 68 trials), these drugs consistently induced both amnestic and non-amnestic cognitive impairments, with evidence of a dose-response relationship. H(1)-antihistamine agents (n = 12) and tricyclic antidepressants (n = 15) induced non-amnestic deficits in attention and information processing. Non-benzodiazepine derivatives (n = 29) also produced combined deficits, but less consistently than benzodiazepine drugs. The evidence was inconclusive for the type of cognitive impairment induced by different bladder relaxant antimuscarinics (n = 9) as well as for narcotic agents (n = 5) and antipsychotics (n = 5). Among healthy volunteers >60 years of age, low doses of commonly used medications such as lorazepam 0.5 mg, oxybutynin immediate release 5 mg and oxycodone 10 mg produced combined deficits.

CONCLUSION

Non-amnestic mild cognitive deficits are consistently induced by first-generation antihistamines and tricyclic antidepressants, while benzodiazepines provoke combined amnestic and non-amnestic impairments. Risk-benefit considerations should be discussed with patients in order to enable an informed choice about drug discontinuation or substitution to potentially reverse cognitive adverse effects.

Pathophysiology of acute brain dysfunction: what's the cause of all this confusion?

PURPOSE OF REVIEW

To survey the recent medical literature examining the pathophysiology of acute brain dysfunction (delirium and coma) in the ICU.

RECENT FINDINGS

Clinical risk factors for brain dysfunction in the ICU continue to be elucidated and prediction models developed. Multiple studies have identified sedatives, especially benzodiazepines, as modifiable risk factors for delirium. Imaging studies examining global brain disorders have demonstrated white matter lesions and brain atrophy to be associated with delirium. Endothelial dysfunction, increased blood-brain barrier permeability, and reduced blood flow have also been implicated in cerebral perfusion abnormalities associated with brain dysfunction. The response of the brain to inflammation, including activation of microglia and neuronal apoptosis, leads to synaptic and neurochemical disturbances. Decreased availability of acetylcholine during critical illness leads to decreased counter-regulatory activity in response to inflammatory disease states, likely causing additional injury and further neurotransmitter imbalances. Dopamine, norepinephrine, and serotonin excess and their respective amino acid precursors have also been associated with brain dysfunction.

SUMMARY

The multifactorial pathophysiology of acute brain dysfunction remains incompletely understood. Multiple clinical risk factors have been identified and numerous pathophysiologic pathways have been hypothesized. Future research is required to investigate the roles of these pathways on differing clinical presentations, potential therapeutic options, and patient outcomes.

The impact of intra- and postoperative albumin levels as a biomarker of delirium after cardiopulmonary bypass: results of an exploratory study

In this prospective study the frequency of delirium after cardiac surgery with cardiopulmonary bypass (CPB) was determined. Furthermore, we investigated the impact of intra- and postoperative levels of albumin as a biomarker of delirium. Thirty-four patients who underwent elective CPB at the Department of Cardiac Surgery, Ludwig-Maximilians-University of Munich, Germany, were enroled in this prospective study. During the intensive care unit (ICU) stay and shortly after discharge from the ICU, delirious state was evaluated daily using the Delirium-Rating-Scale. Albumin was assayed pre-anaesthesia, immediately after induction of anaesthesia, at the beginning of the heart-lung-apparatus period, immediately before the opening and 5min after the opening of the aortic clamp, 24h and 48h postoperatively and on the day before discharge. After CPB, a clinical significant delirious state was observed in 11 patients (32.4%). The albumin level decreased during the surgical intervention and increased postoperatively with a maximum level at the time of discharge. CPB patients with delirious state showed a significantly lower albumin level 24h and 48h postoperatively than those without delirium. A low level of postoperative albumin seems to be a useful biomarker to identify patients with high risk of delirious state after CPB.

Delirium in the ICU: an overview

Delirium is characterized by a disturbance of consciousness with accompanying change in cognition. Delirium typically manifests as a constellation of symptoms with an acute onset and a fluctuating course. Delirium is extremely common in the intensive care unit (ICU) especially amongst mechanically ventilated patients. Three subtypes have been recognized: hyperactive, hypoactive, and mixed. Delirium is frequently undiagnosed unless specific diagnostic instruments are used. 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. The presence of delirium has important prognostic implications; in mechanically ventilated patients it is associated with a 2.5-fold increase in short-term mortality and a 3.2-fold increase in 6-month mortality. Nonpharmacological approaches, such as physical and occupational therapy, decrease the duration of delirium and should be encouraged. Pharmacological treatment for delirium traditionally includes haloperidol; however, more data for haloperidol are needed given the paucity of placebo-controlled trials testing its efficacy to treat delirium in the ICU. Second-generation antipsychotics have emerged as an alternative for the treatment of delirium, and they may have a better safety profile. Dexmedetomidine may prove to be a valuable adjunctive agent for patients with delirium in the ICU.

Delirium in critically ill patients: epidemiology, pathophysiology, diagnosis and management

Delirium is commonly observed in critically ill patients and is associated with negative outcomes. The pathophysiology of delirium is not completely understood. However, alterations to neurotransmitters, especially acetylcholine and dopamine, inflammatory pathways and an aberrant stress response are proposed mechanisms leading to intensive care unit (ICU) delirium. Detection of delirium using a validated delirium assessment tool makes early treatment possible, which may improve prognosis. Patients at high risk of delirium, especially those with cognitive decline and advanced age, should be identified in the first 24 hours of admission to the ICU. Whether these high-risk patients benefit from haloperidol prophylaxis deserves further study. The effectiveness of a multicomponent, non-pharmacological approach is shown in non-ICU patients, which provides proof of concept for use in the ICU. The few studies on this approach in ICU patients suggest that the burden of ICU delirium may be reduced by early mobility, increased daylight exposure and the use of earplugs. In addition, the combined use of sedation, ventilation, delirium and physical therapy protocols can reduce the frequency and severity of adverse outcomes and should become part of routine practice in the ICU, as should avoidance of deliriogenic medication such as anticholinergic drugs and benzodiazepines. Once delirium develops, symptomatic treatment with antipsychotics is recommended, with haloperidol being the drug of first choice. However, there is limited evidence on the safety and effectiveness of antipsychotics in ICU delirium.