Postoperative delirium: the tryptophan dyregulation model

Tryptophan: A Unique Role in the Critically Ill

Tryptophan is an essential amino acid whose metabolites play key roles in diverse physiological processes. Due to low reserves in the body, especially under various catabolic conditions, tryptophan deficiency manifests itself rapidly, and both the serotonin and kynurenine pathways of metabolism are clinically significant in critically ill patients. In this review, we highlight these pathways as sources of serotonin and melatonin, which then regulate neurotransmission, influence circadian rhythm, cognitive functions, and the development of delirium. Kynurenines serve important signaling functions in inter-organ communication and modulate endogenous inflammation. Increased plasma kynurenine levels and kynurenine-tryptophan ratios are early indicators for the development of sepsis. They also influence the regulation of skeletal muscle mass and thereby the development of polyneuromyopathy in critically ill patients. The modulation of tryptophan metabolism could help prevent and treat age-related disease with low grade chronic inflammation as well as post intensive care syndrome in all its varied manifestations: cognitive decline (including delirium or dementia), physical impairment (catabolism, protein breakdown, loss of muscle mass and tone), and mental impairment (depression, anxiety or post-traumatic stress disorder).

Biomarkers in delirium: A systematic review

BACKGROUND

Delirium is a common neuropsychiatric disorder associated with prolonged hospital stays, and increased morbidity and mortality. Diagnosis is frequently missed due to varying disease presentation and lack of standardized testing. We examined biomarkers as diagnostic or prognostic indicators of delirium, and provide a rational basis for future studies.

METHOD

Systematic review of literature published between Jan 2000 and June 2019. Searches included: PubMed; Web of Science; CINAHL; EMBASE; COCHRANE and Medline. Additional studies were identified by searching bibliographies of eligible articles.

RESULTS

2082 relevant papers were identified from all sources. Seventy-three met the inclusion criteria, all of which were observational. These assessed a range of fourteen biomarkers. All papers included were in the English language. Assessment methods varied between studies, including: DSM criteria; Confusion Assessment Method (CAM) or CAM-Intensive Care Unit (ICU). Delirium severity was measured using the Delirium Rating Scale (DRS). Delirium was secondary to post-operative dysfunction or acute medical conditions.

CONCLUSION

Evidence does not currently support the use of any one biomarker. However, certain markers were associated with promising results and may warrant evaluation in future studies. Heterogeneity across study methods may have contributed to inconclusive results, and more clarity may arise from standardization of methods of clinical assessment. Adjusting for comorbidities may improve understanding of the pathophysiology of delirium, in particular the role of confounders such as inflammation, cognitive disorders and surgical trauma. Future research may also benefit from inclusion of other diagnostic modalities such as EEG as well as analysis of genetic or epigenetic factors.

Effects of perioperative interventions for preventing postoperative delirium: A protocol for systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Postoperative delirium (POD) not only increases the medical burden but also adversely affects patient prognosis. Although some cases of delirium can be avoided by early intervention, there is no clear evidence indicating whether any of these measures can effectively prevent POD in specific patient groups.

OBJECTIVE

The aim of this meta-analysis was to compare the efficacy and safety of the existing preventive measures for managing POD.

METHODS

The PubMed, OVID (Embase and MEDLINE), Web of Science, and the Cochrane Library databases were searched for articles published before January 2020. The relevant randomized controlled trials (RCTs) were selected based on the inclusion and exclusion criteria. Data extraction and methodological quality assessment were performed according to a predesigned data extraction form and scoring system, respectively. The interventions were compared on the basis of the primary outcome like incidence of POD, and secondary outcomes like duration of delirium and the length of intensive care unit and hospital stay.

RESULTS

Sixty-three RCTs were included in the study, covering interventions like surgery, anesthesia, analgesics, intraoperative blood glucose control, cholinesterase inhibitors, anticonvulsant drugs, antipsychotic drugs, sleep rhythmic regulation, and multi-modal nursing. The occurrence of POD was low in 4 trials that monitored the depth of anesthesia with bispectral index during the operation (P < .0001). Two studies showed that supplementary analgesia was useful for delirium prevention (P = .002). Seventeen studies showed that perioperative sedation with α2-adrenergic receptor agonists prevented POD (P = .0006). Six studies showed that both typical and atypical antipsychotic drugs can reduce the incidence of POD (P = .002). Multimodal nursing during the perioperative period effectively reduced POD in 6 studies (P < .00001). Furthermore, these preventive measures can reduce the duration of delirium, as well as the total and postoperative length of hospitalized stay for non-cardiac surgery patients. For patients undergoing cardiac surgery, effective prevention can only reduce the length of intensive care unit stay.

CONCLUSION

Measures including intraoperative monitoring of bispectral index, supplemental analgesia, α2-adrenergic receptor agonists, antipsychotic drugs, and multimodal care are helpful to prevent POD effectively. However, larger, high-quality RCTs are needed to verify these findings and develop more interventions and drugs for preventing postoperative delirium.

Unexpected awakenings in severe dementia from case reports to laboratory

OBJECTIVE

Case report notions of unexpected memory retrieval in patients with severe dementia near to death are starting to alter the central "irreversible" paradigm of dementia and locate dementia as a problem of memory retrieval, not consolidation. We suggest that the most likely central tenet of this paradoxical memory retrieval is the fluctuation of neuromodulators projecting from the brain stem to the medial prefrontal cortex and the hippocampus. The neuromodulation-centric explanation of this phenomenon aims to open the "irreversible" paradigm of dementia up for discussion and suggest a plausible treatment strategy by questioning how the devastating process of death fluctuates memory performance in severe dementia.

BACKGROUND

Supporting demented patients, who are mostly unresponsive, without making demands or asking a question and regarding them as valuable human beings unexpectedly improve their memory performance around the time of death.

NEW LUCIDITY HYPOTHESIS

Around the time of death, neurological signs (hyper-arousal and -attention) of demented people point out that neurotransmitter discharges are dramatically changed. Relatively resistant neuromodulator circuits to neurodegeneration can maintain optimal levels of arousal and attention for memory processing. In this way, unexpected episodes of lucidity can be triggered. Also, corticotropin-releasing peptides might increase mental clarity by increasing the excitability of the neuromodulator circuits. The science of memory retrieval is more complicated and nuanced than retrieval observations in case reports, but the rapid development of new techniques holds promise for future understanding of lucidity in severe dementia.

MAJOR CHALLENGE FOR THE MODEL

There is no an animal or human model to test this hypothesis; however, the similarities between neurological signs (instantaneous cognitive fluctuations) of delirium and paradoxical lucidity could provide a unique window to understand neural events of terminal lucidity on a modified animal model of delirium. Likewise, similarities between unexpected consciousness signs of terminal lucidity and lucid dreaming suggest that lucid dreaming episodes might be considered a human model for terminal lucidity research.

Sleep Disturbances After General Anesthesia: Current Perspectives

The purpose of this article is to review (1) sleep mechanism under general anesthesia, harmful effects of postoperative sleep disturbances; (2) risk factors associated with postoperative sleep disturbances; (3) measures to prevent and improve postoperative sleep disturbances. General anesthesia changes the postoperative sleep structure especially in elderly patients after major surgery and results in a high incidence rate of sleep disturbances. Sleep disturbances produce harmful effects on postoperative patients and lead to a higher risk of delirium, more cardiovascular events, and poorer recovery. Some researchers do propose non-pharmacological treatments such as attention to environmental and psychological factors, application of electroacupuncture (EA) technology and pharmacological treatments are helpful, but larger high-quality clinical trials with longer following-up are needed to further investigate the efficacy and safety.

Melatonin and its analogues for the prevention of postoperative delirium: A systematic review and meta-analysis

It remains unclear whether melatonin and its analogues prevent postoperative delirium (POD). Therefore, we conducted a systematic review and meta-analysis to evaluate the effect of melatonin and its analogues on POD prevention. PubMed, Cochrane Library, Web of Science, Embase and CINAHL databases were searched. Primary outcome was the incidence of POD. Six randomized controlled trials, 2 cohort studies and 1 case-control study were included in this meta-analysis. Results showed that melatonin and its analogue ramelteon decreased the incidence of POD in the entire adult surgical population (odds ratio [OR] = 0.45, 95% confidence interval [CI] 0.24-0.84, P = .01). When administered at a higher dose (5 mg), melatonin was effective in reducing the POD incidence (OR = 0.32, 95% CI 0.20-0.52, P < .00001). Melatonin administered less than 5 elimination half-lives before the surgery significantly reduced the POD incidence (OR = 0.31, 95% CI 0.19-0.49, P < .00001). Current literature supports the effectiveness of melatonin and its analogue ramelteon in POD prevention. However, the present study was limited by the significant heterogeneity of the included studies. More studies are needed to ascertain the preventive effect of melatonin and its analogues on the incidence of delirium after cardiac and noncardiac surgeries.

Interventions for preventing delirium in hospitalised non-ICU patients

BACKGROUND

Delirium is a common mental disorder, which is distressing and has serious adverse outcomes in hospitalised patients. Prevention of delirium is desirable from the perspective of patients and carers, and healthcare providers. It is currently unclear, however, whether interventions for preventing delirium are effective.

OBJECTIVES

To assess the effectiveness of interventions for preventing delirium in hospitalised non-Intensive Care Unit (ICU) patients.

SEARCH METHODS

We searched ALOIS - the Cochrane Dementia and Cognitive Improvement Group's Specialized Register on 4 December 2015 for all randomised studies on preventing delirium. We also searched MEDLINE (Ovid SP), EMBASE (Ovid SP), PsycINFO (Ovid SP), Central (The Cochrane Library), CINAHL (EBSCOhost), LILACS (BIREME), Web of Science core collection (ISI Web of Science), ClinicalTrials.gov and the WHO meta register of trials, ICTRP.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of single and multi- component non-pharmacological and pharmacological interventions for preventing delirium in hospitalised non-ICU patients.

DATA COLLECTION AND ANALYSIS

Two review authors examined titles and abstracts of citations identified by the search for eligibility and extracted data independently, with any disagreements settled by consensus. The primary outcome was incidence of delirium; secondary outcomes included duration and severity of delirium, institutional care at discharge, quality of life and healthcare costs. We used risk ratios (RRs) as measures of treatment effect for dichotomous outcomes; and between group mean differences and standard deviations for continuous outcomes.

MAIN RESULTS

We included 39 trials that recruited 16,082 participants, assessing 22 different interventions or comparisons. Fourteen trials were placebo-controlled, 15 evaluated a delirium prevention intervention against usual care, and 10 compared two different interventions. Thirty-two studies were conducted in patients undergoing surgery, the majority in orthopaedic settings. Seven studies were conducted in general medical or geriatric medicine settings.We found multi-component interventions reduced the incidence of delirium compared to usual care (RR 0.69, 95% CI 0.59 to 0.81; seven studies; 1950 participants; moderate-quality evidence). Effect sizes were similar in medical (RR 0.63, 95% CI 0.43 to 0.92; four studies; 1365 participants) and surgical settings (RR 0.71, 95% CI 0.59 to 0.85; three studies; 585 participants). In the subgroup of patients with pre-existing dementia, the effect of multi-component interventions remains uncertain (RR 0.90, 95% CI 0.59 to 1.36; one study, 50 participants; low-quality evidence).There is no clear evidence that cholinesterase inhibitors are effective in preventing delirium compared to placebo (RR 0.68, 95% CI, 0.17 to 2.62; two studies, 113 participants; very low-quality evidence).Three trials provide no clear evidence of an effect of antipsychotic medications as a group on the incidence of delirium (RR 0.73, 95% CI, 0.33 to 1.59; 916 participants; very low-quality evidence). In a pre-planned subgroup analysis there was no evidence for effectiveness of a typical antipsychotic (haloperidol) (RR 1.05, 95% CI 0.69 to 1.60; two studies; 516 participants, low-quality evidence). However, delirium incidence was lower (RR 0.36, 95% CI 0.24 to 0.52; one study; 400 participants, moderate-quality evidence) for patients treated with an atypical antipsychotic (olanzapine) compared to placebo (moderate-quality evidence).There is no clear evidence that melatonin or melatonin agonists reduce delirium incidence compared to placebo (RR 0.41, 95% CI 0.09 to 1.89; three studies, 529 participants; low-quality evidence).There is moderate-quality evidence that Bispectral Index (BIS)-guided anaesthesia reduces the incidence of delirium compared to BIS-blinded anaesthesia or clinical judgement (RR 0.71, 95% CI 0.60 to 0.85; two studies; 2057 participants).It is not possible to generate robust evidence statements for a range of additional pharmacological and anaesthetic interventions due to small numbers of trials, of variable methodological quality.

AUTHORS' CONCLUSIONS

There is strong evidence supporting multi-component interventions to prevent delirium in hospitalised patients. There is no clear evidence that cholinesterase inhibitors, antipsychotic medication or melatonin reduce the incidence of delirium. Using the Bispectral Index to monitor and control depth of anaesthesia reduces the incidence of postoperative delirium. The role of drugs and other anaesthetic techniques to prevent delirium remains uncertain.

The Healthy Heart-Mind trial: melatonin for prevention of delirium following cardiac surgery: study protocol for a randomized controlled trial

Background

Delirium is a common occurrence in patients undergoing major cardiac surgery and is associated with a number of adverse consequences for the individual, their family and the health system. Current approaches to the prevention of delirium include identifying those at risk together with various non-pharmacological and pharmacological strategies, although the efficacy of these is often modest. Emerging evidence suggests that melatonin may be biologically implicated in the development of delirium and that melatonin supplementation may be beneficial in reducing the incidence of delirium in medical and surgical patients. We designed this trial to determine whether melatonin reduces the incidence of delirium following cardiac surgery compared with placebo.

Methods/Design

The Healthy Heart-Mind trial is a randomized, double-blind, placebo-controlled clinical trial of 3 mg melatonin or matching placebo administered on seven consecutive days for the prevention of delirium following cardiac surgery. We will recruit 210 adult participants, aged 50 and older, undergoing elective or semi-elective cardiac surgery with the primary outcome of interest for this study being the difference in the incidence of delirium between the groups within 7 days of surgery. Secondary outcomes of interest include the difference between groups in the severity and duration of delirious episodes, hospital length of stay and referrals to mental health services during admission. In addition, we will assess differences in depressive and anxiety symptoms, as well as cognitive performance, at discharge and 3 months after surgery.

Discussion

The results of this trial will clarify whether melatonin reduces the incidence of delirium following cardiac surgery.

Trial registration

The trial is registered with the Australian Clinical Trials Registry, trial number ACTRN12615000819527 (10 August 2015).

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1163-1) contains supplementary material, which is available to authorized users.

The diurnal profile of melatonin during delirium in elderly patients--preliminary results

Delirium is an acute-onset syndrome that exacerbates patients' condition and significantly increases consequential morbidity and mortality. There is no comprehensive, cellular and tissue-level, pathophysiological theory. The melatonin hormone imbalance has been shown to be linked to circadian rhythms, sleep-wake cycle disturbances, and delirium incidence. There has been relatively little research about melatonin in delirium, and there has been no such study done in the group of elderly patients of a general medicine ward yet. The aim of our study was to compare melatonin hormone concentration in relation to the presence of delirium in elderly patients hospitalized in the general medicine ward. Blood samples were collected four times a day for two days (at 12:00, 18:00, 00:00 and 6:00), on the day when delirium was diagnosed and 72 h after the delirium resolution. Delirium was diagnosed with the Confusion Assessment Method and the criteria of the Diagnostic and Statistic Manual of Mental Disorders, 4th Revision. The mean age of 30 patients (73.3% women) was 86.5 ± 5.2 years. Delirium was diagnosed most often on the second and third day of hospitalization. A lot of predisposing and precipitating factors for delirium were identified. There was a significant difference in the melatonin hormone concentration measurement at 12:00 when patients had acute delirium and after its resolution [18.5 (13.8, 27.5) vs 12.9 (9.8, 17.8), p<0.01]. Different patterns of the melatonin hormone concentration were shown in analyses in the subgroups defined according to the patients' diagnosis of dementia. We found that the delirium recovery was, in fact, associated with the alteration of the daily profile of melatonin.

Tryptophan supplementation and postoperative delirium--a randomized controlled trial

OBJECTIVES

To determine whether the postoperative administration of tryptophan would be beneficial for elderly adults undergoing surgery who are at risk of developing postoperative delirium.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

Denver Veterans Affairs Medical Center.

PARTICIPANTS

Individuals aged 60 and older undergoing major elective operations requiring a postoperative intensive care unit (ICU) admission (n = 325).

INTERVENTION

L-tryptophan, 1 g orally three times a day or placebo was started after surgery and continued for up to 3 days postoperatively.

MEASUREMENTS

Delirium and its motor subtypes were measured using the Confusion Assessment Method-Intensive Care Unit (CAM-ICU) and the Richmond Agitation and Sedation Scale. The primary outcome for between-group comparison was the incidence of excitatory (mixed and hyperactive) postoperative delirium. The secondary outcomes for comparison were the incidence and duration of overall postoperative delirium.

RESULTS

The overall incidence of postoperative delirium was 39% (95% confidence interval = 34-44%) (n = 116). Seventeen percent of participants in the tryptophan group and 9% in the placebo group had excitatory delirium (P = .18), and the duration of excitatory delirium was 3.3 ± 1.7 days for tryptophan and 3.1 ± 1.9 days for placebo (P = .74). Forty percent of participants in the tryptophan group and 37% in the placebo group had overall delirium (P = .60), and the duration of overall delirium was 2.9 ± 1.8 days for tryptophan and 2.4 ± 1.6 days for placebo (P = .17).

CONCLUSION

Postoperative tryptophan supplementation in older adults undergoing major elective operations requiring postoperative ICU admission did not reduce the incidence or duration of postoperative excitatory delirium or overall delirium.

'Chronomics' in ICU: circadian aspects of immune response and therapeutic perspectives in the critically ill

Complex interrelations exist between the master central clock, located in the suprachiasmatic nuclei of the hypothalamus, and several peripheral clocks, such as those found in different immune cells of the body. Moreover, external factors that are called ‘timekeepers’, such as light/dark and sleep/wake cycles, interact with internal clocks by synchronizing their different oscillation phases. Chronobiology is the science that studies biologic rhythms exhibiting recurrent cyclic behavior. Circadian rhythms have a duration of approximately 24 h and can be assessed through chronobiologic analysis of time series of melatonin, cortisol, and temperature. Critically ill patients experience severe circadian deregulation due to not only the lack of effective timekeepers in the intensive care unit (ICU) environment but also systemic inflammation. The latter has been found in both animal and human studies to disrupt circadian rhythmicity of all measured biomarkers. The aims of this article are to describe circadian physiology during acute stress and to discuss the effects of ICU milieu upon circadian rhythms, in order to emphasize the value of considering circadian-immune disturbance as a potential tool for personalized treatment. Thus, besides neoplastic processes, critical illness could be linked to what has been referred as ‘chronomics’: timing and rhythm. In addition, different therapeutic perspectives will be presented in association with environmental approaches that could restore circadian connection and hasten physical recovery.

Delirium: a disturbance of circadian integrity?

Delirium is a serious neuropsychiatric syndrome of acute onset that occurs in approximately one in five general hospital patients and is associated with serious adverse outcomes that include loss of adaptive function, persistent cognitive problems and increased mortality. Recent studies indicate a three-domain model for delirium that includes generalised cognitive impairment, disturbed executive cognition, and disruption of behaviours that are under circadian control such as sleep-wake cycle and motor activity levels. As a consequence, attention has focused upon the possible role of the circadian timing system (CTS) in the pathophysiology of delirium. We explored this possibility by reviewing evidence that (1) many symptoms that occur in delirium are influenced by circadian rhythms, (2) many features of recognised circadian rhythm disorders are similar to characteristic features of delirium, (3) common risk factors for delirium are known to disrupt circadian systems, (4) physiological disturbances of circadian systems have been noted in delirious patients, and (5) positive effects in the treatment of delirium have been demonstrated for melatonin and related agents that influence the circadian timing system. A programme of future studies that can help to clarify the relevance of circadian integrity to delirium is described. Such work can provide a better understanding of the pathophysiology of delirium while also identifying opportunities for more targeted therapeutic efforts.

Delirium: is sleep important?

Delirium and poor sleep quality are common and often co-exist in hospitalised patients. A link between these disorders has been hypothesised but whether this link is a cause-and-effect relationship or simply an association resulting from shared mechanisms is yet to be determined. Potential shared mechanisms include: abnormalities of neurotransmitters, tissue ischaemia, inflammation and sedative exposure. Sedatives, while decreasing sleep latency, often cause a decrease in slow wave sleep and stage rapid eye movement (REM) sleep and therefore may not provide the same restorative properties as natural sleep. Mechanical ventilation, an important cause of sleep disruption in intensive care unit (ICU) patients, may lead to sleep disruption not only from the discomfort of the endotracheal tube but also as a result of ineffective respiratory efforts and by inducing central apnoea events if not properly adjusted for the patient's physiologic needs. When possible, efforts should be made to optimise the patient-ventilator interaction to minimise sleep disruptions.

Perioperative plasma melatonin concentration in postoperative critically ill patients: its association with delirium

PURPOSE

Delirium is a common complication in postoperative critically ill patients. Although abnormal melatonin metabolism is thought to be one of the mechanisms of delirium, there have been few studies in which the association between alteration of perioperative plasma melatonin concentration and postoperative delirium was assessed.

MATERIALS

We conducted a prospective observational study to assess the association of perioperative alteration of plasma melatonin concentration with delirium in 40 postoperative patients who required intensive care for more than 48 hours. We diagnosed postoperative delirium using Confusion Assessment Method for the intensive care unit and measured melatonin concentration 4 times (before the operation as the preoperative value, 1 hour after the operation, postoperative day 1, and postoperative day 2).

RESULTS

Postoperative delirium occurred in 13 (33%) of the patients. Although there was no significant difference in preoperative melatonin concentration, Δ melatonin concentration at 1 hour after the operation was significantly lower in patients with delirium than in those without delirium (-1.1 vs 0 pg/mL, P = .036). After adjustment of relevant confounders, Δ melatonin concentration was independently associated with risk of delirium (odds ratio, 0.50; P = .047).

CONCLUSIONS

Delta melatonin concentration at 1 hour after the operation has a significant independent association with risk of postoperative delirium.

The association of the kynurenine pathway of tryptophan metabolism with acute brain dysfunction during critical illness*

OBJECTIVES

Plasma tryptophan levels are associated with delirium in critically ill patients. Although tryptophan has been linked to the pathogenesis of other neurocognitive diseases through metabolism to neurotoxins via the kynurenine pathway, a role for kynurenine pathway activity in intensive care unit brain dysfunction (delirium and coma) remains unknown. This study examined the association between kynurenine pathway activity as determined by plasma kynurenine concentrations and kynurenine/tryptophan ratios and presence or absence of acute brain dysfunction (defined as delirium/coma-free days) in intensive care unit patients.

DESIGN, SETTING, AND PATIENTS

This was a prospective cohort study that utilized patient data and blood samples from the Maximizing Efficacy of Targeted Sedation and Reducing Neurologic Dysfunction trial, which compared sedation with dexmedetomidine vs. lorazepam in mechanically ventilated patients.

MEASUREMENTS AND MAIN RESULTS

Baseline plasma kynurenine and tryptophan concentrations were measured using high-performance liquid chromatography with or without tandem mass spectrometry. Delirium was assessed daily using the Confusion Assessment Method for the Intensive Care Unit. Linear regression examined associations between kynurenine pathway activity and delirium/coma-free days after adjusting for sedative exposure, age, and severity of illness. Among 84 patients studied, median age was 60 yrs and Acute Physiology and Chronic Health Evaluation II score was 28.5. Elevated plasma kynurenine and kynurenine/tryptophan ratio were both independently associated with significantly fewer delirium/coma-free days (i.e., fewer days without acute brain dysfunction). Specifically, patients with plasma kynurenine or kynurenine/tryptophan ratios at the 75th percentile of our population had an average of 1.8 (95% confidence interval 0.6-3.1) and 2.1 (95% confidence interval 1.0-3.2) fewer delirium/coma-free days than those patients with values at the 25th percentile (p = .006 and p < .001, respectively).

CONCLUSIONS

Increased kynurenine pathway activation, assessed by plasma kynurenine and kynurenine/tryptophan ratio, was associated with fewer days alive and without acute brain dysfunction in intensive care unit patients. Future studies are warranted to clarify this relationship and investigate potential therapeutic interventions.

The effects of melatonin versus placebo on delirium in hip fracture patients: study protocol of a randomised, placebo-controlled, double blind trial

Background

With an ageing population, older persons become a larger part of the hospital population. The incidence of delirium is high in this group, and experiencing delirium has major short- and long-term sequelae, which makes prevention crucial. During delirium, a disruption of the sleep-wake cycle is frequently observed. Melatonin plays an important role in the regulation of the sleep-wake cycle, so this raised the hypothesis that alterations in the metabolism of melatonin might play an important role in the development of delirium. The aim of this article is to describe the design of a randomised, placebo controlled double-blind trial that is currently in progress and that investigates the effects of melatonin versus placebo on delirium in older, postoperative hip fracture patients.

Methods/Design

Acutely hospitalised patients aged 65 years or older admitted for surgical repair of hip fracture are randomised (n = 452) into a treatment or placebo group. Prophylactic treatment consists of orally administered melatonin (3 mg) at 21:00 h on five consecutive days. The primary outcome is the occurrence of delirium, to be diagnosed according to the Confusion Assessment Method, within eight days after start of the study medication. Secondary outcomes are delirium severity, measured by the Delirium Rating Scale; duration of delirium; differences in subtypes of delirium; differences in total length of hospital stay; total dose of antipsychotics and/or benzodiazepine use during delirium; and in-hospital complications. In the twelve-month follow up visit, cognitive function is measured by a Mini-Mental state examination and the Informant Questionnaire on Cognitive Decline in the Elderly. Functional status is assessed with the Katz ADL index score (patient and family version) and grip strength measurement. The outcomes of these assessments are compared to the outcomes that were obtained during admission.

Discussion

The proposed study will contribute to our knowledge because studies on the prophylactic treatment of delirium with long term follow up remain scarce. The results may lead to a prophylactic treatment for frail older persons at high risk for delirium that is safe, effective, and easily implementable in daily practice.

Trial registration

Dutch Clinical Trial Registry: NTR1576

Melatonin decreases delirium in elderly patients: a randomized, placebo-controlled trial

BACKGROUND

Disturbance in the metabolism of tryptophan and tryptophan-derived compounds (e.g., melatonin) may have a role in the pathogenesis of delirium.

OBJECTIVE

To evaluate the efficacy of low dose exogenous melatonin in decreasing delirium.

DESIGN

A randomized, double-blinded, placebo-controlled study.

SETTING

An Internal Medicine service in a tertiary care centre in London, Ontario, Canada.

PARTICIPANTS

145 individuals aged 65 years or over admitted through the emergency department to a medical unit in a tertiary care hospital.

INTERVENTION

Patients were randomized to receive either 0.5 mg of melatonin or placebo every night for 14 days or until discharge.

MEASUREMENTS

The primary outcome was the occurrence of delirium as determined by Confusion Assessment Method (CAM) criteria.

RESULTS

Of a total of 145 individuals (mean age (standard deviation): 84.5 (6.1) years) 72 were randomly assigned to the melatonin group and 73 to the placebo group. Melatonin was associated with a lower risk of delirium (12.0% vs. 31.0%, p = 0.014), with an odds ratio (OR), adjusted for dementia and co-morbidities of 0.19 (95% confidence intervals (CI): 0.06-0.62). Results were not different when patients with prevalent delirium were excluded.

LIMITATION

An intention to treat analysis was not possible due to loss to follow-up.

CONCLUSION

Exogenous low dose melatonin administered nightly to elderly patients admitted to acute care may represent a potential protective agent against delirium.

Effectiveness of melatonin treatment on circadian rhythm disturbances in dementia. Are there implications for delirium? A systematic review

OBJECTIVE

Circadian rhythm disturbances, like sundowning, are seen in dementia. Because the circadian rhythm is regulated by the biological clock, melatonin might be effective in the treatment of these disturbances. We systematically studied the effect of melatonin treatment in patients with dementia. In addition, we elaborate on the possible effects one might expect of melatonin treatment in patients with delirium, since dementia and delirium are strongly related. Moreover, some evidence exists that sundowning in patients with dementia and the alterations in the sleep/wake cycle, seen in patients with delirium both originate from circadian rhythm disturbances.

DESIGN

A systematic search of the literature, published between 1985 and April 2009, was performed using PubMed and other databases. All papers on melatonin treatment in dementia were retrieved. Effects of melatonin on circadian rhythm disturbances were scored by means of scoring sundowning/agitated behaviour, sleep quality and daytime functioning.

RESULTS

Nine papers, including four randomised controlled trials (RCTs) (n = 243), and five case series (n = 87) were reviewed. Two of the RCTs found a significant improvement on sundowning/agitated behaviour. All five case series found an improvement. The results on sleep quality and daytime functioning were inconclusive.

CONCLUSION

Sundowning/agitated behaviour improves with melatonin treatment in patients with dementia. There are several arguments that sundowning in patients with dementia and the alterations in the sleep/wake cycle in patients with delirium have a common background, namely a disturbance of the circadian rhythm. This suggests that melatonin treatment could also have the same positive effects in patients with delirium.

Plasma tryptophan and tyrosine levels are independent risk factors for delirium in critically ill patients

AIM

The pathophysiology of delirium remains elusive though neurotransmitters and their precursor large neutral amino acids (LNAAs) may play a role. This pilot study investigated whether alterations of tryptophan (Trp), phenylalanine (Phe), and tyrosine (Tyr) plasma levels were associated with a higher risk of transitioning to delirium in critically ill patients.

METHODS

Plasma LNAA concentrations were determined on days 1 and 3 in mechanically ventilated (MV) patients from the MENDS randomized controlled trial (dexmedetomidine vs. lorazepam sedation). Three independent variables were calculated by dividing plasma concentrations of Trp, Phe, and Tyr by the sum of all other LNAA concentrations. Delirium was assessed daily using the confusion assessment method for the intensive care unit (CAM-ICU). Markov regression models were used to analyze independent associations between plasma LNAA ratios and transition to delirium after adjusting for covariates.

RESULTS

The 97 patients included in the analysis had a high severity of illness (median APACHE II, 28; IQR, 24-32). After adjusting for confounders, only high or very low tryptophan/LNAA ratios (p = 0.0003), and tyrosine/LNAA ratios (p = 0.02) were associated with increased risk of transitioning to delirium, while phenylalanine levels were not (p = 0.27). Older age, higher APACHE II scores and increasing fentanyl exposure were also associated with higher probabilities of transitioning to delirium.

CONCLUSIONS

In this pilot study, plasma tryptophan/LNAA and tyrosine/LNAA ratios were associated with transition to delirium in MV patients, suggesting that alterations of amino acids may be important in the pathogenesis of ICU delirium. Future studies evaluating the role of amino acid precursors of neurotransmitters are warranted in critically ill patients.

Delirium: sifting through the confusion

Delirium is commonly encountered in the hospital setting, particularly in the intensive care unit. However, the diagnosis is often missed, due in part to the nature of the illness, fluctuating levels of consciousness, and varied presentation. Even when it is recognized, delirium can be hard to manage, with multiple factors contributing to its course. In this article, we review the latest information regarding the underlying mechanisms of the syndrome and treatment options available. This is accomplished by examining two complex cases encountered at a university medical center-based psychosomatic service.

Executive function and depression as independent risk factors for postoperative delirium

BACKGROUND

Postoperative delirium has been associated with greater complications, medical cost, and increased mortality during hospitalization. Recent evidence suggests that preoperative executive dysfunction and depression may predict postoperative delirium; however, the combined effect of these risk factors remains unknown. This study examined the association among preoperative executive function, depressive symptoms, and established clinical predictors of postoperative delirium among 998 consecutive patients undergoing major noncardiac surgery.

METHODS

A total of 998 patients were screened for postoperative delirium (n = 998) using the Confusion Assessment Method as well as through retrospective chart review. Patients underwent cognitive, psychosocial, and medical assessments preoperatively. Executive function was assessed using the Concept Shifting Task, Letter-Digit Coding, and a modified Stroop Color Word Interference Test. Depression was assessed by the Beck Depression Inventory.

RESULTS

Preoperative executive dysfunction (P = 0.007) and greater levels of depressive symptoms (P = 0.049) were associated with a greater incidence of postoperative delirium, independent of other risk factors. Secondary analyses of cognitive performance demonstrated that the Stroop Color Word Interference Test, the executive task with the greatest complexity in this battery, was more strongly associated with postoperative delirium than simpler tests of executive function. Furthermore, patients exhibiting both executive dysfunction and clinically significant levels of depression were at greatest risk for developing delirium postoperatively.

CONCLUSIONS

Preoperative executive dysfunction and depressive symptoms are predictive of postoperative delirium among noncardiac surgical patients. Executive tasks with greater complexity are more strongly associated with postoperative delirium relative to tests of basic sequencing.

Evaluation and management of the elderly patient at risk for postoperative delirium

Geriatric patients are at a high risk for the development of postoperative delirium. By recognizing predisposing and precipitating risk factors, preventive measures can be undertaken to reduce this risk. Accurate and timely diagnosis is essential, and we offer therapeutic strategies to help reduce the high morbidity and mortality of this important condition.

Motor subtypes of delirium: past, present and future

Clinical subtyping of delirium according to motor-activity profile has considerable potential to account for the heterogeneity of this complex and multifactorial syndrome. Previous work has identified a range of clinically important differences between motor subtypes in relation to detection, causation, treatment experience and prognosis, but studies have been hampered by inconsistent methodology, especially in relation to definition of subtypes. This article considers research to date, including a number of recent studies that have attempted to address these issues and identify a means of achieving greater consistency in approaches to subtyping. Possibilities for future work are discussed and a research plan for the field is outlined.

Sleep and delirium in ICU patients: a review of mechanisms and manifestations

Sleep deprivation and delirium are conditions commonly encountered in intensive care unit patients. Sleep in these patients is characterized by sleep fragmentation, an increase in light sleep, and a decrease of both slow wave sleep and rapid eye movement sleep. The most common types of delirium in this population are hypoactive and mixed-type. Knowledge about the mechanisms of sleep and delirium has evolved over time, but these phenomena are not yet well understood. What is known, however, is that different areas in the brainstem transmit information to the thalamus and cortex necessary for sleep-wake regulation. Delirium is related to an imbalance in the synthesis, release, and inactivation of some neurotransmitters, particularly acetylcholine and dopamine. The relationship between sleep deprivation and delirium has been studied for many years and has been viewed as reciprocal. The link between them may be ascribed to shared mechanisms. An imbalance in neurotransmitters as well as alteration of melatonin production may contribute to the pathogenesis of both phenomena. A better understanding of the mechanisms and factors that contribute to sleep deprivation and delirium can guide the development of new methods and models for prevention and treatment of these problems and consequently improve patient outcomes.

Drug treatment of delirium: past, present and future

OBJECTIVE

The aim of this review was to summarize and critically evaluate the current literature regarding the safety and efficacy of drug therapy in delirium. We also identified recent research developments and highlighted some ongoing clinical trials to explore future directions in drug treatment and prevention of delirium.

METHODS

We conducted a literature search of Medline, Embase, PsychInfo, and Cochrane Review databases, which included both prospective and retrospective clinical trials and case studies on delirium and drug therapy in adult patients up to March 2008. Abstracts from recent topical conferences were also reviewed. Ongoing delirium drug studies were identified via the WHO International Clinical Trials Registry Platform Search Portal, accessed March 12, 2008.

RESULTS

The evidence base for effective drug treatment of delirium is restricted by limitations in many of the studies conducted to date. However, there has been an increase in the quantity and quality of delirium drug studies in recent years; preliminary reports and ongoing studies add to this trend. Although efficacy rates between typical and atypical antipsychotic agents are similar, the latter are associated with fewer extrapyramidal side effects. Prophylactic interventions with antipsychotic and cholinesterase inhibitors in high-risk patients provide an opportunity to improve postoperative patient care. Alternative techniques and medication opportunities could be explored in attempts to minimize drug induced delirium potential.

CONCLUSIONS

Appropriate drug therapy should be considered part of systematic approaches to delirium treatment and prevention. There is a need for well-designed randomized, double-blind placebo-controlled trials investigating the drug management of various aspects of delirium, including delineating treatment by delirium subtype, dose ranging studies, and optimal duration of therapy.

Mechanisms of neurologic failure in critical illness

Critical illness frequently is associated with neurologic failure that may involve the central and peripheral nervous systems. Central nervous system failure is associated with a spectrum of neurobehavioral changes including delirium, coma, and long-term cognitive dysfunction. Peripheral neurologic failure, or critical illness neuromuscular abnormalities, is suggested by diffuse arreflexic weakness and protracted respiratory insufficiency, and may also persist long after the acute hospitalization. While the burden of neurological disease complicating critical illness is considerable, preventive or therapeutic options are limited. This article provides an overview of research evaluating the relationship between critical illness and neurologic function, with a special emphasis on underlying mechanisms.

Impact of delirium on cognition, distress, and health-related quality of life after hematopoietic stem-cell transplantation

PURPOSE

To determine the impact of delirium during the acute phase of myeloablative hematopoietic stem-cell transplantation (HSCT) on health-related quality of life (HRQOL), distress, and neurocognitive functioning 30 and 80 days after transplantation.

PATIENTS AND METHODS

Ninety patients completed a battery assessing HRQOL, distress, and neuropsychological functioning before receiving their first HSCT. Delirium was assessed three times per week using the Delirium Rating Scale and the Memorial Delirium Assessment Scale from 7 days before transplantation through 30 days after transplantation. At 30 days after transplantation, distress and neurocognitive functioning were assessed. At 80 days after transplantation, HRQOL, distress, and neuropsychological functioning were re-evaluated.

RESULTS

After adjusting for confounding factors, patients who experienced a delirium episode, versus patients who did not, reported significantly worse depression, anxiety, and fatigue symptoms at 30 days (linear regression beta(s) = 0.2, 0.3, and 0.5, respectively; P < .04). At 80 days, patients with a delirium episode had significantly worse executive functioning (beta = -1.1; P < .02), attention and processing speed (beta(s) = -4.7 and -5.4, respectively; P < .03), mental health on the Medical Outcomes Study Health Survey, 12-item short form (beta = -6.5; P < .02), and anxiety, fatigue, and cancer and treatment distress symptoms (beta(s) = 0.4, 0.6, and 0.3, respectively; P < .03).

CONCLUSION

Patients with a malignancy who experience delirium during myeloablative HSCT showed impaired neurocognitive abilities and persistent distress 80 days after transplantation. Effective prevention or treatment of delirium during HSCT may improve both cognitive and psychological outcomes.

Serum biomarkers for delirium

This narrative review examines serum biomarkers for the diagnosis and monitoring of delirium. Serum biomarkers for delirium fall into three major groups: 1) those that are present or elevated prior to disease onset-risk markers, 2) those that rise with onset and fall with recovery-disease markers, and 3) those that rise in proportion to the consequences of disease-end products. As risk markers, we examine serum chemistries and genetic risk markers. As disease markers, we examine serum anticholinergic activity, amino acids, melatonin, cytokines, cortisol, and gene expression. As end products of delirium, we examine markers of neuronal injury. Finally, we discuss methodological and biostatistical considerations for future biomarker studies. Identifying accurate biomarkers for delirium may shed further light into its pathophysiology and on the interrelationship between delirium and dementia.

Melatonin: possible implications for the postoperative and critically ill patient

There is increasing interest in the hormone melatonin in postoperative and critically ill patients. The roles of melatonin in the regulation of the sleep-wake cycle, resetting of circadian rhythm disturbances and its extensive antioxidant activity have potential applications in these patient groups. The interaction between melatonin and the stresses of surgery and critical illness are explored in the context of circadian rhythms, sleep disorders and delirium. The antioxidant activity is discussed in terms of the reduction of ischaemic reperfusion injury, prevention of multi-organ failure and treatment of sepsis. Unfortunately, there is currently insufficient evidence that exogenous melatonin is effective in preventing or treating postoperative delirium. Similarly, in the critically ill patient, sleep disorders are associated with disrupted melatonin circadian secretion, but there is a paucity of data to support routine exogenous melatonin supplementation. More clinical evidence to confirm the potential benefits of melatonin therapy is required before it can be routinely used in the postoperative or critically ill patient.