Alertness, cognition and morphine in patients with advanced cancer

Opioids and driving: education gaps in advanced cancer

OBJECTIVES

Opioids may impair the ability to drive safely, particularly when first prescribed or with dose titration. We investigated whether clinicians evaluate driving status and provide opioid-related driving advice when initiating opioids among people with advanced lung cancer.

METHODS

A retrospective medical record review of outpatients with advanced non-small cell lung cancer seen at an Australian tertiary referral centre between 1 January 2015 and 31 December 2019 was undertaken to determine frequency of opioid prescription and documentation of driving status and education regarding driving safety while taking opioids.

RESULTS

Of 1022 patients screened, 205 were commenced on opioid therapy. Forty-seven (23%) patients had driving status documented. According to medical records, education about driving safety while on opioids was provided to two (1%) patients on opioid initiation. Ten (5%) patients received opioid-related driving education at least once at follow-up appointments. The content of the education was infrequently documented, and when documented, focused on opioid side effects impacting driving. Opioid doses were often escalated at follow-up appointments.

CONCLUSIONS

According to documentation in medical records, clinicians infrequently assessed driving status on opioid initiation and rarely provided education regarding opioid-related driving risks. Further research and clearer guidance regarding opioids and driving safety in the cancer population are required.

Neurocognitive predictors of adherence to an online pain self-management program adjunct to long-term opioid therapy

INTRODUCTION

While pain self-management programs can significantly improve patient outcomes, poor adherence is common and the need for research on predictors of adherence has been noted. A potential, but commonly overlooked, predictor is cognitive function. Our aim, then, was to examine the relative influence of various cognitive functional domains on engagement with an online pain self-management program.

METHOD

A secondary analysis of a randomized controlled trial testing the impact of E-health (a 4-month subscription to the online Goalistics Chronic Pain Management Program) plus treatment as usual, relative to treatment as usual alone, on pain and opioid dose outcomes in adults receiving long-term opioid therapy of morphine equivalence dose ≥20 mg; 165 E-health participants who completed an on-line neurocognitive battery were included in this sub-analysis. A variety of demographic, clinical, and symptom rating scales were also examined. We hypothesized that better processing speed and executive functions at baseline would predict engagement with the 4-month E-health subscription.

RESULTS

Ten functional cognitive domains were identified using exploratory factor analysis and the resultant factor scores applied for hypothesis testing. The strongest predictors of E-health engagement were selective attention, and response inhibition and speed domains. An explainable machine learning algorithm improved classification accuracy, sensitivity, and specificity.

CONCLUSIONS

The results suggest that cognition, especially selective attention, inhibitory control, and processing speed, is predictive of online chronic pain self-management program engagement. Future research to replicate and extend these findings seems warranted.

CLINICALTRIALS.GOV REGISTRATION NUMBER

NCT03309188.

The Effects of Opioids on Cognition in Older Adults With Cancer and Chronic Noncancer Pain: A Systematic Review

CONTEXT

Opioids are prescribed to manage moderate-to-severe pain and can be used with older adults; however, they may lead to several adverse effects, including cognitive impairment.

OBJECTIVES

To identify, appraise, and synthesize evidence on the impact of opioids on cognition in older adults with cancer/chronic noncancer pain, and screening tools/neuropsychological assessments used to detect opioid-induced cognitive impairment.

METHODS

A systematic literature review following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (international prospective register of systematic reviews registration: CRD42018092943). MEDLINE, EMBASE, PsycINFO, CINAHL, Cochrane Library, and Web of Science were searched up to December 2018. Randomized controlled trials, quasi-experimental studies, and observational studies of adults aged 65 years and older with cancer/chronic noncancer pain taking opioids were included. A narrative synthesis was conducted.

RESULTS

From 4036 records, 10 met inclusion criteria. Five studies used one screening tool, and five studies used a range of neuropsychological assessments; assessing 14 cognitive domains. Most studies demonstrated no effect of opioid use on cognitive domains, whereas four studies showed mixed effects. In particular, attention, language, orientation, psychomotor function, and verbal working/delayed episodic memory were worsened. Changes to cognitive function were predominantly observed in studies with higher mean doses of opioids (120-190.7mg oral morphine equivalent daily dose).

CONCLUSION

Both improvements and impairments to cognition were observed in studies with higher mean opioid doses. In clinical practice, a brief screening tool assessing attention, language, orientation, psychomotor function, and verbal working/delayed episodic memory may be beneficial to detect worsening cognition in older adults with chronic pain using opioids.

Sleep abnormalities associated with alcohol, cannabis, cocaine, and opiate use: a comprehensive review

Sleep abnormalities are associated with acute and chronic use of addictive substances. Although sleep complaints associated with use and abstinence from addictive substances are widely recognized, familiarity with the underlying sleep abnormalities is often lacking, despite evidence that these sleep abnormalities may be recalcitrant and impede good outcomes. Substantial research has now characterized the abnormalities associated with acute and chronic use of alcohol, cannabis, cocaine, and opiates. This review summarizes this research and discusses the clinical implications of sleep abnormalities in the treatment of substance use disorders.

Neuropsychological assessment of chronic non-malignant pain patients treated in a multidisciplinary pain centre

The aim of the study was to investigate the influence of pain, sedation, pain medications and socio-demographics on cognitive functioning in chronic non-malignant pain patients. Chronic non-malignant pain patients (N=91) treated in a multidisciplinary pain centre were compared with age and sex matched healthy volunteers (N=64). Furthermore four subgroups of patients were examined: Group 1 (N=21) received no pain medications, group 2 (N=19) were in long-term oral opioid treatment, group 3 (N=18) were treated with antidepressants and/or anticonvulsants and group 4 (N=33) were treated with a combination of long-term oral opioids and antidepressants and/or anticonvulsants. Assessments comprised pain (PVAS) and sedation (SVAS), Continuous Reaction Time (CRT) testing for sustained attention, Finger Tapping Test (FTT) testing for psychomotor speed, Paced Auditory Serial Addition Task (PASAT) testing for information processing and working memory and Mini Mental State Examination (MMSE). CRT and FTT were impaired in the total patient sample. Treatment with opioids was associated with poorer performance of PASAT. High scores of PVAS and SVAS were associated with poor performance of PASAT and CRT, respectively. MMSE seems to be too insensitive for detecting the milder forms of cognitive impairment found in chronic non-malignant patients.

Buprenorphine disrupts sleep and decreases adenosine concentrations in sleep-regulating brain regions of Sprague Dawley rat

BACKGROUND

Buprenorphine, a partial μ-opioid receptor agonist and κ-opioid receptor antagonist, is an effective analgesic. The effects of buprenorphine on sleep have not been well characterized. This study tested the hypothesis that an antinociceptive dose of buprenorphine decreases sleep and decreases adenosine concentrations in regions of the basal forebrain and pontine brainstem that regulate sleep.

METHODS

Male Sprague Dawley rats were implanted with intravenous catheters and electrodes for recording states of wakefulness and sleep. Buprenorphine (1 mg/kg) was administered systemically via an indwelling catheter and sleep-wake states were recorded for 24 h. In additional rats, buprenorphine was delivered by microdialysis to the pontine reticular formation and substantia innominata of the basal forebrain while adenosine was simultaneously measured.

RESULTS

An antinociceptive dose of buprenorphine caused a significant increase in wakefulness (25.2%) and a decrease in nonrapid eye movement sleep (-22.1%) and rapid eye movement sleep (-3.1%). Buprenorphine also increased electroencephalographic delta power during nonrapid eye movement sleep. Coadministration of the sedative-hypnotic eszopiclone diminished the buprenorphine-induced decrease in sleep. Dialysis delivery of buprenorphine significantly decreased adenosine concentrations in the pontine reticular formation (-14.6%) and substantia innominata (-36.7%). Intravenous administration of buprenorphine significantly decreased (-20%) adenosine in the substantia innominata.

CONCLUSIONS

Buprenorphine significantly increased time spent awake, decreased nonrapid eye movement sleep, and increased latency to sleep onset. These disruptions in sleep architecture were mitigated by coadministration of the nonbenzodiazepine sedative-hypnotic eszopiclone. The buprenorphine-induced decrease in adenosine concentrations in basal forebrain and pontine reticular formation is consistent with the interpretation that decreasing adenosine in sleep-regulating brain regions is one mechanism by which opioids disrupt sleep.

Cognitive impairment in cancer pain patients receiving opioids: a pilot study

This study aimed to compare cognitive function of cancer pain patients being given opioids during their cancer treatment (n = 14) with that of patients receiving treatment without opioids (n = 12). Correlations between cognitive function, pain intensity, and opioid dose were analyzed. Patients were assessed 3 times in a 1-month period, using the Trail-Making Test, Mini-Mental State Examination, Digit Span, and Brief Cognitive Screening Battery. Opioid use was not associated with clear cognitive impairment. Patients being treated without opioids did perform better in the Digit Span Test reverse-order test (P = .029) and the clock drawing test (P = .023), but the differences arose in just 1 assessment in each case. Pain intensity correlated negatively with scores in the Mini-Mental State Examination (P = .001) and some Brief Cognitive Screening Battery tests (incidental recall, immediate recall, and late recall; P <or= .042) in the group receiving opioids. Opioid dose did not correlate with any of the measures of cognitive performance. However, the patients with the worst performance scores were those with more severe pain. Further studies are needed to clearly distinguish between the effects of opioids versus the effects of pain.

Assessing cognitive and psychomotor performance under long-term treatment with transdermal buprenorphine in chronic noncancer pain patients

BACKGROUND

The therapeutic use of opioids has been associated with altered cognition and impaired psychomotor function. Several studies have demonstrated the impact of opioid therapy on psychomotor performance and cognition, but there are no data about the effect of long-term treatment with transdermal buprenorphine on driving ability.

METHODS

Thirty patients suffering from chronic noncancer pain, who had been treated with stable doses of transdermal buprenorphine, included in a prospective trial and compared with 90 healthy volunteers (matched pairs). A computerized test battery, developed to assess the driving ability of traffic delinquents in Germany, was used. Attention reaction, visual orientation, motor coordination, and vigilance were evaluated. The data from 14 variables were assessed, and for each test, a relevant score was defined. As the primary end-point, the sum score of the three relevant scores was determined. A weaker statistical means to assess the patient's performance is to compare the test results to an age-independent control group. Individuals performing worse than the 16th percentile of this control group are considered to be unable to drive according to German law.

RESULTS

According to tests that predict driving ability, patients receiving transdermal buprenorphine were shown to be noninferior to the control group. Driving ability, as defined as a result above the 16th percentile, did not differ significantly between the patients and the control group.

CONCLUSION

Long-term use of transdermal buprenorphine for chronic noncancer pain does not impair driving ability, but because of the individual variability of test results, an individual assessment is recommended.

Side-effects of opioids in chronic pain treatment

The emergence of opioid-induced neurotoxicity has gained increasing recognition in the literature in the past decade. Exciting developments at the receptor and intracellular level have revealed some insights into the potential mechanisms underlying this phenomenon. The hitherto reported clinical benefits of opioid rotation and dose reduction in the treatment of opioid toxicity warrant further clarification in prospective studies, particularly in relation to their relative value.

Sleep and GABA levels in the oral part of rat pontine reticular formation are decreased by local and systemic administration of morphine

Morphine, a mu-opioid receptor agonist, is a commonly prescribed treatment for pain. Although highly efficacious, morphine has many unwanted side effects including disruption of sleep and obtundation of wakefulness. One mechanism by which morphine alters sleep and wakefulness may be by modulating GABAergic signaling in brain regions regulating arousal, including the pontine reticular nucleus, oral part (PnO). This study used in vivo microdialysis in unanesthetized Sprague-Dawley rat to test the hypothesis that mu-opioid receptors modulate PnO GABA levels. Validation of the high performance liquid chromatographic technique used to quantify GABA was obtained by dialyzing the PnO (n=4 rats) with the GABA reuptake inhibitor nipecotic acid (500 microM). Nipecotic acid caused a 185+/-20% increase in PnO GABA levels, confirming chromatographic detection of GABA and demonstrating the existence of functional GABA transporters in rat PnO. Morphine caused a concentration-dependent decrease in PnO GABA levels (n=25 rats). Coadministration of morphine (100 microM) with naloxone (1 microM), a mu-opioid receptor antagonist, blocked the morphine-induced decrease in PnO GABA levels (n=5 rats). These results show for the first time that mu-opioid receptors in rat PnO modulate GABA levels. A second group of rats (n=6) was used to test the hypothesis that systemically administered morphine also decreases PnO GABA levels. I.v. morphine caused a significant (P<0.05) decrease (19%) in PnO GABA levels relative to control i.v. infusions of saline. Finally, microinjections followed by 2 h recordings of electroencephalogram and electromyogram tested the hypothesis that PnO morphine administration disrupts sleep (n=8 rats). Morphine significantly (P<0.05) increased the percent of time spent in wakefulness (65%) and significantly (P<0.05) decreased the percent of rapid eye movement (REM) sleep (-53%) and non-REM sleep (-69%). The neurochemical and behavioral data suggest that morphine may disrupt sleep, at least in part, by decreasing GABAergic transmission in the PnO.

Assessing cognition and psychomotor function under long-term treatment with controlled release oxycodone in non-cancer pain patients

BACKGROUND

The therapeutic use of opioids can be associated with altered cognition and impaired psychomotor function. Several studies have demonstrated the impact of opioid therapy on psychomotor performance and cognition, but no data exist about the effect of long-term treatment with controlled release oxycodone (CRO) on driving ability.

METHODS

Thirty patients suffering from chronic non-cancer pain who had been treated with stable doses of CRO where included in a prospective trial and compared with 90 healthy volunteers (matched pairs). A computerized test battery that was developed to assess the driving ability of traffic delinquents in Germany was employed. Attention reaction, visual orientation, motor coordination and vigilance were evaluated. The data from a total of 11 parameters were assessed and for each test a relevant score was defined. As the primary endpoint the sum score of the three relevant scores was determined. A weaker statistical means to assess the patients' performance is to compare the test results with an age-independent control group. Individuals performing worse than the 16th percentile of this control group are considered to be unable to drive according to German legislation.

RESULTS

Significant non-inferiority could not be demonstrated for the primary endpoint. However, driving ability as defined as a result above the 16th percentile did not differ significantly between the patients receiving CRO and the age-independent control group.

CONCLUSION

The use of CRO does not prohibit driving, but individual assessment is necessary.

[Medication and memory: interactions among the elderly]

Several different systems govern human memory, and different drugs may act specifically on one or more of them. The central nervous system in the elderly is particularly sensitive to drugs, and an iatrogenic cause must be sought for all recent and/or sudden alterations in memory functions. In the case of recent alterations in memory, all nonessential drugs, especially psychotropic agents; should be withdrawn or reduced. Elderly persons, especially those with dementia, are at risk because of the frequent and substantial effects of drugs on their memory: the benefit-risk ratio must be evaluated regularly and essential treatments maintained.

Therapie chronischer Schmerzen mit oralem retardiertem Oxycodon

Oral controlled-release oxycodone has been available for the treatment of chronic pain in Germany since 1998. Controlled trials have shown good clinical efficacy and tolerability. This survey reports results from six open prospective multicenter trials. In these trials 4196 patients suffering from cancer pain and non-cancer-related pain with inadequate pain relief were treated with oral controlled-release oxycodone for 3-4 weeks. Only a few participating physicians were pain specialists. A total of 356 patients suffering from pain of the musculoskeletal system and receiving oxycodone therapy were monitored for 6 months. Exclusion from the studies was due mainly to inadequate analgesia, side effects, and noncompliance. The efficacy of oxycodone was rated to be better than moderate by most of the patients, quality of life parameters increased significantly, and patient satisfaction was high. The treatment with oral controlled-release oxycodone was a safe and effective option even when used by nonspecialized physicians.

The cognitive effects of opioids

Successful opioid therapy often depends on achieving a balance between analgesic effectiveness and side effects. The risk of opioid-induced cognitive impairment often hinders clinicians and patients from initiating or optimizing opioid therapy. Despite subjective experiences of mental dullness and sedation, objective tests of cognitive functioning do not always demonstrate marked changes following opioid administration. To guide clinical practice, as well as patient and family teaching, pain management nurses should be familiar with literature regarding this topic. The purpose of this article is to review the empiric literature on opioids and cognitive functioning, including the relationships among pain, cognition, delirium, and opioids. In general, research reflects minimal to no significant impairments in cognitive functioning. If impairment does occur, it is most often associated with parenteral opioids administered to opioid-naive individuals. Some evidence suggests that opioids may actually enhance cognitive function and decrease delirium in some patient populations. This article describes this research and explores the clinical implications of the research in this area.

The effects of transdermal fentanyl on driving, cognitive performance, and balance in patients with chronic nonmalignant pain conditions

OBJECTIVE

To evaluate driving performance, cognition, and balance in patients with chronic nonmalignant pain before and after the addition of transdermal fentanyl to their treatments.

DESIGN

Prospective, one-group pretest-posttest design.

SETTING

Outpatient pain center associated with a large, urban medical school.

INTERVENTIONS

Patients taking less than a 15-mg equivalent of oxycodone per day took baseline driving performance, cognitive, and balance tests. Transdermal fentanyl was initiated and titrated in 25-microg/hour increments, weighing benefits and side effects. At the end of a 1-month period, the achieved dose was maintained for another month. After they were stabilized for 1 month, patients repeated driving, cognitive, and balance tests.

RESULTS

Twenty three patients completed the study; three discontinued secondary to side effects. The median dose at the end of the titration period was 50 microg/hour (48%). No differences were found in driving simulation measures between the pretreatment and posttreatment periods. No decrements in cognitive performance were found. Improvements in visual motor tracking, visual memory, and attention were found during treatment with transdermal fentanyl. No differences in balance or body sway were found. Pain decreased over the course of treatment.

CONCLUSIONS

The addition of transdermal fentanyl to a treatment regimen containing no opiates or small amounts of opiates for patients with chronic nonmalignant pain did not negatively affect their driving performances, reaction times, cognition, or balance. Future studies in this area are needed to guide treatment decisions.

Long term effects of oral sustained release morphine on neuropsychological performance in patients with chronic non-cancer pain

Morphine is increasingly used in patients with chronic non-cancer pain, but a major concern associated with chronic use relates to possible cognitive side-effects. The aim of this long-term prospective study was to evaluate the cognitive impact of oral sustained release morphine in patients with non-cancer pain. A battery of neuropsychological tests to explore attention, psychomotor speed and memory was administered. The effects of morphine on pain, quality of life, mood, subjective memory impairment and side-effects were also investigated. Evaluations were performed at baseline in patients free from opioids and then after 3, 6 and 12 months. Twenty-eight patients were included: 18 received oral sustained morphine (range 40-140 mg/day), ten patients stopped morphine prematurely because of side-effects or insufficient pain relief and were followed as a control group. There was no impairment of any neuropsychological variable over time in the morphine treated patients in comparison with the control group. Two measures of information processing speed - the Stroop interference score and the digit symbol test were improved at 6 and 12 months and there were significant correlations with the pain relief and improvement of mood. Self-reported memory impairment improved notably in responders to morphine. Morphine induced persisting effects on pain, and to a lesser extent on quality of life and mood. The visual analog scale score for side-effects increased at 12 months and essentially consisted of gastrointestinal disorders. This study demonstrates that 12 months treatment with oral morphine does not disrupt cognitive functioning in patients with chronic non-cancer pain and instead results in moderate improvement of some aspects of cognitive functioning, as a consequence of the pain relief and concomitant improvement of well-being and mood.

Are opioid-dependent/tolerant patients impaired in driving-related skills? A structured evidence-based review

Previous reviewers have concluded that opioids cause dose-related impairment in opioid-naive volunteers on psychomotor skills related to driving. Data relating to opioid-dependent/tolerant patients have not yet been reviewed. To determine what evidence, if any, exists for or against opioid-related driving skill impairment in opioid-dependent/tolerant patients, we performed a structured evidence-based review of all available studies addressing the issue of whether opioid-dependent/tolerant patients are impaired in driving-related skills. A computer and manual literature search for studies relating to opioid-dependent/tolerant patients and driving-related skills produced 48 relevant reports. These references were reviewed in detail, sorted, and placed into tabular form according to the following subject areas: (1) psychomotor abilities studies; (2) cognitive function studies; (3) effect of opioid dosing on psychomotor abilities studies; (4) motor vehicle driving violations and motor vehicle accident studies; and (5) driving impairment as measured in driving simulators and off/on road driving studies. For each topic area, each study was categorized for the type of study it represented according to guidelines developed by the Agency for Health Care Policy Research (AHCPR). The strength and consistency of the evidence in each subject area also then was categorized according to AHCPR guidelines and a quantitative method. This evidence-based review indicated the following: (1) There was moderate, generally consistent evidence for no impairment of psychomotor abilities of opioid-maintained patients; (2) There was inconclusive evidence on multiple studies for no impairment on cognitive function of opioid- maintained patients; (3) There was strong consistent evidence on multiple studies for no impairment of psychomotor abilities immediately after being given doses of opioids; (4) There was strong, consistent evidence for no greater incidence in motor vehicle violations/motor vehicle accidents versus comparable controls of opioid-maintained patients; and (5) There was consistent evidence for no impairment as measured in driving simulators off/on road driving of opioid-maintained patients. Based on the above results, it can be concluded that the majority of the reviewed studies appeared to indicate that opioids do not impair driving-related skills in opioid-dependent/tolerant patients. This evidence was consistent in four out of five research areas investigated, but inconclusive in one. As such, additional controlled studies are required. Until more data are available, however, physicians may wish to consider the approach to this problem recommended in this review.

Opioid switching from morphine to transdermal fentanyl for toxicity reduction in palliative care

The study objective was to determine whether switching patients from morphine to transdermal fentanyl resulted in a reduction of morphine-associated side effects, and an improvement in cognitive function and patients' well being while maintaining adequate pain and symptom control. Nineteen patients aged 42-86 with terminal cancer, maintained on morphine for pain and distressed as a result of morphine toxicity, were given the dose of fentanyl corresponding to their current morphine dose. Pain control was then maintained (mostly fentanyl 50-100 microg/h) over the 14-day study period. Throughout the study, patients' global assessment of well being (primary efficacy variable) was statistically significantly improved. Sleepiness and drowsiness were significantly less of a problem. There was a trend towards improvement in attention span/concentration, and in the power and quality of concentration. Cognitive function tests also revealed a significant improvement in working (short term) and speed of memory although not in secondary (long term) memory. Patients did not experience hallucinations or delusions and there was no change in levels of anxiety or depression (Hospital Anxiety Depression Scale). The incidence of dizziness was significantly reduced, and there was a nonsignificant decrease in number of patients who suffered myoclonus and in the severity of this condition over the 14 days. The investigator's overall impression of treatment with transdermal fentanyl was 'fair', which was not in agreement with the positive impression expressed by patients (score 74, range: 0 worst, 100 best). Further work is required to determine if the improvement in patients' well being and cognitive function is achieved in larger study populations.

Effects of intermediate- and long-term use of opioids on cognition in patients with chronic pain

The authors review research on the intermediate- and long-term effects of taking opioid medication on cognitive functioning in patients with chronic cancer and noncancer pain. Opioids seem to be more likely to worsen cognitive performance during the first few days of use and during the first few hours after a given dose, particularly on timed performance in psychomotor tasks. Results have been inconsistent regarding what decrements in cognitive performance are observed when patients with chronic pain who have been using opioids for more than three days are compared with healthy volunteers. Relatively few differences have been found when cognitive performance in these patients is compared with their performance before taking opioids, or with the performance of a comparable pain population not taking opioids. Major unresolved questions remain regarding such important issues as effects of different types of opioids, dose effects, interactions with other medications, and subject variables.

The panorama of opioid-related cognitive dysfunction in patients with cancer: a critical literature appraisal

BACKGROUND

Opioids have an essential role in the management of pain in cancer patients, particularly those with advanced disease. Cognitive dysfunction is a recognized complication of opioid use. However, misconceptions and controversy surround the nature and prevalence of its occurrence. A projected increase in the aging cancer population highlights the need for a better understanding of this phenomenon.

METHODS

A critical appraisal of the literature evidence in relation to the pattern, pathophysiology, assessment, impact, and management of cognitive dysfunction due to opioid use in cancer pain management is given.

RESULTS

Studies in cancer patients with less advanced disease reveal subtle evidence of cognitive impairment, largely related to initial dosing or dose increases. In advanced cancer, opioid-induced cognitive dysfunction usually occurs in the form of delirium, a multifactorial syndrome. The presence of both cognitive impairment and delirium frequently is misdiagnosed or missed. Potential risk factors include neuropathic and incidental pain, opioid tolerance, somatization of psychologic distress, and a history of drug or alcohol abuse. Elevation of opioid metabolites with renal impairment may contribute to cognitive dysfunction. Recognition of opioid-related cognitive dysfunction is improved by objective screening. Successful management requires either dose reduction or a change of opioid, in addition to addressing other reversible precipitants such as dehydration or volume depletion.

CONCLUSIONS

Opioid-related cognitive dysfunction tends to be subtle in the earlier stages of cancer, whereas delirium, a more florid form with behavioral disturbance is likely to be present in the advanced cancer population. In patients with advanced disease, an optimal management approach requires careful clinical assessment, identification of risk factors, objective monitoring of cognition, maintenance of adequate hydration, and either dose reduction or switching to a different opioid.

Measurement of opioid-induced sedation

One of the major side effects of opioid analgesics is sedation. Despite the fact that neither a universal definition nor a gold standard for the measurement of opioid-induced sedation exists, various neurophysiologic and psychomotor measures are used to quantify the sedative effects of opioids. This report reviews the strengths and weaknesses of various approaches that are used to measure opioid-induced sedation. The first section summarizes various neurophysiologic measures (i.e., electroencephalogram, autonomic reflexes, and evoked responses), and the second section reviews psychomotor measures (i.e., visual analog scales, observer assessments, motor performance tests, tests of perceptual processes, tests of information processing, tests of memory, and composite tests) that are used to evaluate the sedative effects of opioids. Implications for future research on opioid-induced sedation are discussed.

Definition of and mechanism for opioid-induced sedation

Although sedation is acknowledged to be one of the most common side effects of opioid analgesics, the mechanisms and characteristics of this phenomenon remain elusive, and research in this area is extremely limited. This report integrates research findings on the mechanism of action of opioids with research findings on the phenomenon of consciousness to develop a model of how opioids may act in the central nervous system to produce sedation. Based on this integration, a definition of opioid-induced sedation is proposed to encourage dialogue and research on this perplexing and clinically significant phenomenon.

Neuropsychological performance in cancer patients: the role of oral opioids, pain and performance status

The aim of the present study was to evaluate the possible influence of oral opioids, pain and performance status on some aspects of psychomotor function and cognition in cancer patients. One hundred and thirty cancer patients between 40 and 76 years of age were consecutively included in the study. In order to separate the impact of performance status, pain and oral opioids on neuropsychological functioning the patients were allocated in a cross-sectional design to five different groups. Group 1 (N=40), which was considered the control group, was characterized by being in Karnofsky Performance Status (KPS) A ('Able to carry on normal activity and work. No special care is needed'), had no pain and received no oral opioid medication. Group 2 (N=19) was characterized by being in KPS B ('Unable to work. Able to live at home and care for most personal needs. A varying degree of assistance is needed'), had no pain and received no oral opioid medication. Group 3 (N=19) was characterized by being in KPS B, had pain, but received no oral opioid medication. Group 4a (N=31) was characterized by being in KPS B, had pain and received stable doses of oral opioids. Group 4b (N=21) was characterized by being in KPS B, had no pain and received stable doses of opioids. Assessments comprised pain intensity, sedation, opioid doses, time from ingestion of last opioid dose to testing and opioid side effects. The neuropsychological tests used were continuous reaction time (CRT), finger tapping test (FTT) and paced auditory serial addition task (PASAT). Regarding the neuropsychological tests group 1 was compared with each of the other groups and respecting the hierarchy of increasing numbers of stigmatizing factors group 1 was compared with group 2, group 2 with group 3 and so forth. Concerning CRT, group 1 performed statistically significantly faster than groups 2, 4a and 4b. Concerning FTT, group 1 performed statistically significantly faster than groups 3 and 4a. Concerning PASAT, groups 1 and 4b performed statistically significantly better than group 4a. Furthermore, the pain-relieved groups 2 and 4b performed statistically significantly better in PASAT than the pain-suffering groups 3 and 4a. We conclude that in cancer patients the impact of stigmatizing factors (oral opioids, pain and reduced performance status) seems to impair some important aspects of neuropsychological performance, but more specifically our results indicate that (1) the use of long-term oral opioid treatment in cancer patients per se did not affect any of the neuropsychological tests used in the present study, (2) cancer patients being in KPS B had statistically significantly slower CRT than patients being in KPS A and (3) pain itself may deteriorate the performance of PASAT more than oral opioid treatment.

Impaired neuropsychological performance in chronic nonmalignant pain patients receiving long-term oral opioid therapy

The study investigated neuropsychological performance in chronic nonmalignant pain patients receiving long-term oral opioid therapy. Forty patients treated solely with regular and stable doses of an oral opioid were compared with 40 healthy volunteers. The patients received daily opioid doses of 15-300 mg of oral morphine (median: 60 mg) or equianalgesic doses of other opioids. The neuropsychological tests consisted of continuous reaction time (CRT), which measured vigilance/attention; finger tapping test (FTT), which measured psychomotor speed; and paced auditory serial addition task (PASAT), which measured working memory. Three months after the study had been carried out, 14 of the controls were retested in order to determine the reliability of the three tests. The patients performed statistically significantly poorer than the controls in all the tests. Significantly positive correlations were found between the PASAT and pain visual analogue scales (VAS). In the retesting of 14 controls, it was found that the tests showed high reliability. Vigilance/attention, psychomotor speed, and working memory were significantly impaired in chronic nonmalignant pain patients. The present study cannot determine which factors influenced the test results, but pain itself seemed to have an arousal effect on working memory.