Stone, P., & Minton, O. (2011). European Palliative Care Research collaborative pain guidelines. Central side-effects management: What is the evidence to support best practice in the management of sedation, cognitive impairment and myoclonus? Palliative Medicine, 25, 431–441.

To provide a systematic review examining the management of opioid-induced central side effects including sedation, cognitive failure, sleep disturbance and myoclonus

• The literature reviewed included research, case reports, and retrospective chart reviews in an effort to establish evidence levels for practice guidelines and make recommendations for future research and practice. 
• This review is part of a larger review to produce guidelines on the use of opioids in adult patients with cancer pain.

Databases: Medline, EMBASE, Cochrane Library

Keywords: Narcotic, opioid analgesics, opioid, neoplasms, myoclonus, sleep initiation and maintenance disorders, hallucination, sleep disorder, fatigue, delirium, hyperalgesia, sedation, confusion, opioid-induced hyperalgesia, analgesics

Inclusion criteria: Studies were included that were conducted with human, adult patients with chronic cancer pain, contained data on the efficacy of a treatment for an opioid central nervous system adverse effect (e.g., sedation, cognitive impairment, myoclonus, hyperalgaesia, insomnia), and were published in the English language.

Exclusion criteria: Studies were excluded if they were comparing the efficacy or side effects of different opioids, the efficacy or side effects of adjuvant analgaesics, different doses of opioids, or different routes of administration of opioids.
 

A total of 318 manuscripts were screened. Inclusion and exclusion criteria were screened from titles and abstracts; duplication studies were eliminated. No scoring criteria for evidence recommendations were presented, but levels of evidence were presented for each central side effect.

Cognitive failure was evaluated by sedation and psychomotor speed; those studies consisted of two randomized controlled trials, one retrospective chart review, and four case reports. Four studies were focused on the central side effect of delirium, and two randomized controlled trials were focused on psychomotor aspects of cognitive function. Five side effects of opioid therapy were identified: sedation, cognitive impairment, myoclonus, sleep disturbance, and hyperalgesia.

Forty studies were potentially eligible, with a final 26 meeting all inclusion criteria. The final sample of studies included 86 subjects, ranging from case reports of one subject (n = 2), a case report of six subjects (n = 1), a retrospective chart review of 40 subjects (n = 1), and randomized controlled trials of 12–20 subjects (n = 2).

The adult subjects in the studies had varying cancers and were receiving opioid administration for chronic pain in palliative care inpatient and outpatient settings. Ages, education, occupational attainment, and socioeconomic data were not provided across the studies.

This systematic review is applicable in palliative care.

In two similar randomized controlled trials using the same psychomotor test battery, methylphenidate improved verbal and visual memory, arithmetic, and tapping speed as compared to placebo for subjects receiving morphine, whereas IV infusion only improved tapping speed. Delirium was improved by donepezil in 7 of 9 patients as measured by the Clinical Global Impression of Improvement Scale on retrospective chart review, whereas improvements were observed in only 2 of 6 patients with delirium receiving donepezil in a case report series. Atypical antipsycholtics and neuroleptics have also been used to improve delirium that is resistant to donepezil, according to three additional case reports: physostigmine (N = 1), olanzapine (N = 1), and quetiapine (N = 6).                                                                     

Seven studies were identified as related to cognitive impairment: two were randomized controlled, and five were case reports or case series.Three of the case reports combined totaled 12 patients. Two more studies were related to delirium.

The authors weakly recommended the use of methylphenidate for the symptom management of opioid-induced cognitive failure. Other agents lack evidence to make a recommendation.

Further study is warranted with incorporation of cognitive test batteries for multiple cognitive domains.

Limitations include small sample size, use of varying medications as the intervention, outcome focus on delirium as cognitive impairment, and use of case reports and retrospective chart reviews.