Treatment for Hyperosmolar Dehydration in Hospitalised Adults: Protocol for a Scoping Review of Current Evidence and Gaps.

Background: Dehydration-specifically hyperosmolar dehydration (HD)-in adults is a common clinical condition affecting an estimated 25%-58% of adults admitted to the hospital, depending on the method used to assess HD and the patient group. HD is defined as low total body water and increased serum osmolality over 300 mOsm/kg. Hypernatremia, increased blood urea nitrogen (BUN)/creatinine ratio, and calculated serum osmolarity are often used as proxy markers. The condition is associated with an increased risk of a range of complications, including increased morbidity and mortality. Despite the high prevalence, current treatment guidelines often fail to distinguish HD from hypovolemia. As a result, HD is often treated like hypovolemia with fluids containing isotonic saline rather than hypotonic fluids. Objective: The objective of this review is to identify and summarize existing studies on the treatment of HD in adults and to map the current evidence, highlight gaps in the literature and guide future research. Methods: The planned review will be conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. A systematic search will be conducted in MEDLINE (PubMed), Embase (Ovid), Scopus, and the Cochrane Central Register of Controlled Trials, with additional examination of reference lists and citations (backward snowballing) and a search for completed trials based on found protocols (forward snowballing). Original studies of any design focusing on adult patients with a suspected low total body water and biochemically-confirmed HD receiving treatment for HD will be included. Studies will be excluded if: conducted on a non-adult population, no diagnoses of HD, focusing solely on hypovolaemia, or conducted in a non-hospital setting. Data charting will contain study characteristics, participant demographics, details of HD diagnosis, treatment approaches, and reported outcomes. Relevant information from the included studies will be reported in a narrative summary, supported by descriptive analyses of quantitative data where appropriate. Results: The primary search was completed in September 2025. An updated search will be performed before the completion of the review. As of April 2026, data extraction using Covidence on the relevant studies found in the primary search has been completed. Conclusions: This scoping review will provide an overview of the current evidence on the treatment of HD in patients referred to hospital, identifying key insights and evidence gaps to inform future research.