Pharmacological interventions for the treatment of delirium in critically ill adults

Although delirium is typically an acute reversible cognitive impairment, its presence is associated with devastating impact on both short-term and long-term outcomes for critically ill patients. Advances in our understanding of the negative impact of delirium on patient outcomes have prompted trials evaluating multiple pharmacological interventions. However, considerable uncertainty surrounds the relative benefits and safety of available pharmacological interventions for this population.

Primary objective1. To assess the effects of pharmacological interventions for treatment of delirium on duration of delirium in critically ill adults with confirmed or documented high risk of deliriumSecondary objectivesTo assess the following:1. effects of pharmacological interventions on delirium-free and coma-free days; days with coma; delirium relapse; duration of mechanical ventilation; intensive care unit (ICU) and hospital length of stay; mortality; and long-term outcomes (e.g. cognitive; discharge disposition; health-related quality of life); and2. the safety of such treatments for critically ill adult patients.

We searched the following databases from their inception date to 21 March 2019: Ovid MEDLINE®, Ovid MEDLINE® In-Process & Other Non-Indexed Citations, Embase Classic+Embase, and PsycINFO using the Ovid platform. We also searched the Cochrane Library on Wiley, the International Prospective Register of Systematic Reviews (PROSPERO) (http://www.crd.york.ac.uk/PROSPERO/), the Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Web of Science. We performed a grey literature search of relevant databases and websites using the resources listed in Grey Matters developed by the Canadian Agency for Drugs and Technologies in Health (CADTH). We also searched trial registries and abstracts from annual scientific critical care and delirium society meetings.

We sought randomized controlled trials (RCTs), including quasi-RCTs, of any pharmacological (drug) for treatment of delirium in critically ill adults. The drug intervention was to be compared to another active drug treatment, placebo, or a non-pharmacological intervention (e.g. mobilization). We did not apply any restrictions in terms of drug class, dose, route of administration, or duration of delirium or drug exposure. We defined critically ill patients as those treated in an ICU of any specialty (e.g. burn, cardiac, medical, surgical, trauma) or high-dependency unit.

Two review authors independently identified studies from the search results; four review authors (in pairs) performed data extraction and assessed risk of bias independently. We performed data synthesis through pairwise meta-analysis and network meta-analysis (NMA). Our hypothetical network structure was designed to be analysed at the drug class level and illustrated a network diagram of 'nodes' (i.e. drug classes) and 'edges' (i.e. comparisons between different drug classes from existing trials), thus describing a treatment network of all possible comparisons between drug classes. We assessed the quality of the body of evidence according to GRADE, as very low, low, moderate, or high.

We screened 7674 citations, from which 14 trials with 1844 participants met our inclusion criteria. Ten RCTs were placebo-controlled, and four reported comparisons of different drugs. Drugs examined in these trials were the following: antipsychotics (n = 10), alpha₂ agonists (n = 3; all dexmedetomidine), statins (n = 2), opioids (n = 1; morphine), serotonin antagonists (n = 1; ondansetron), and cholinesterase (CHE) inhibitors (n = 1; rivastigmine). Only one of these trials consistently used non-pharmacological interventions that are known to improve patient outcomes in both intervention and control groups.Eleven studies (n = 1153 participants) contributed to analysis of the primary outcome. Results of the NMA showed that the intervention with the smallest ratio of means (RoM) (i.e. most preferred) compared with placebo was the alpha₂ agonist dexmedetomidine (0.58; 95% credible interval (CrI) 0.26 to 1.27; surface under the cumulative ranking curve (SUCRA) 0.895; moderate-quality evidence). In order of descending SUCRA values (best to worst), the next best interventions were atypical antipsychotics (RoM 0.80, 95% CrI 0.50 to 1.11; SUCRA 0.738; moderate-quality evidence), opioids (RoM 0.88, 95% CrI 0.37 to 2.01; SUCRA 0.578; very-low quality evidence), and typical antipsychotics (RoM 0.96, 95% CrI 0.64 to1.36; SUCRA 0.468; high-quality evidence).The NMAs of multiple secondary outcomes revealed that only the alpha₂ agonist dexmedetomidine was associated with a shorter duration of mechanical ventilation (RoM 0.55, 95% CrI 0.34 to 0.89; moderate-quality evidence), and the CHE inhibitor rivastigmine was associated with a longer ICU stay (RoM 2.19, 95% CrI 1.47 to 3.27; moderate-quality evidence). Adverse events often were not reported in these trials or, when reported, were rare; pair-wise analysis of QTc prolongation in seven studies did not show significant differences between antipsychotics, ondansetron, dexmedetomidine, and placebo.

We identified trials of varying quality that examined six different drug classes for treatment of delirium in critically ill adults. We found evidence that the alpha₂ agonist dexmedetomidine may shorten delirium duration, although this small effect (compared with placebo) was seen in pairwise analyses based on a single study and was not seen in the NMA results. Alpha₂ agonists also ranked best for duration of mechanical ventilation and length of ICU stay, whereas the CHE inhibitor rivastigmine was associated with longer ICU stay. We found no evidence of a difference between placebo and any drug in terms of delirium-free and coma-free days, days with coma, physical restraint use, length of stay, long-term cognitive outcomes, or mortality. No studies reported delirium relapse, resolution of symptoms, or quality of life. The ten ongoing studies and the six studies awaiting classification that we identified, once published and assessed, may alter the conclusions of the review.