Parenteral thiamine for prevention and treatment of delirium in critically ill adults: a systematic review protocol

BACKGROUND: Delirium is an acute confusional state, common in critical illness and associated with cognitive decline. There is no effective pharmacotherapy to prevent or treat delirium, although it is scientifically plausible that thiamine could be effective. Thiamine studies in dementia patients are inconclusive. Aside from small numbers, all used oral administration: bioavailability of thiamine is poor; parenteral thiamine bypasses this. In the UK, parenteral thiamine is administered as a compound vitamin B and C solution (Pabrinex®). The aim of this review is to evaluate the effectiveness of parenteral thiamine (alone or in a compound solution) in preventing or treating delirium in critical illness. METHODS: We will search for studies in electronic databases (MEDLINE (Pro-Quest), EMBASE, CINAHL, LILACS, CNKI, AMED, and Cochrane CENTRAL), clinical trials registries (WHO International Clinical Trials Registry, ClinicalTrials.gov, and Controlled-trials.com), and grey literature (Google Scholar, conference proceedings, and Index to Theses). We will perform complementary searches of reference lists of included studies, relevant reviews, clinical practice guidelines, or other pertinent documents (e.g. official documents and government reports). We will consider quasi-randomised or randomised controlled trials in critically ill adults. We will include studies that evaluate parenteral thiamine versus standard of care, placebo, or any other non-pharmacological or pharmacological interventions. The primary outcomes will be the delirium core outcome set, including incidence and severity of delirium and cognition. Secondary outcomes are adapted from the ventilation core outcome set: duration of mechanical ventilation, length of stay, and adverse events incidence. Screening, data extraction, and risk of bias assessment will be undertaken independently by two reviewers. If data permits, we will conduct meta-analyses using a random effects model and, where appropriate, sensitivity and subgroup analyses to explore sources of heterogeneity. DISCUSSION: This review will provide evidence for the effectiveness of parental thiamine in the prevention or treatment of delirium in critical care. Findings will contribute to establishing the need for a multicentre study of parenteral thiamine in the prevention and treatment of critical care delirium. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42019118808