Background: Intravenous (IV) fluid therapy has become a ubiquitous intervention in everyday clinical practice. Several types of fluid are available including isotonic crystalloid fluids. Among crystalloid fluids, buffered solutions (derivatives of the original Hartmann's and Ringer's solutions) are increasingly recommended as first-line resuscitation fluids. However, the choice between different buffered solutions appears to be difficult with limited data to support the use of lactate vs. acetate buffered solutions. Accordingly, we aim at systematically describing the body of evidence on the use of the different types of buffered crystalloid solutions in hospitalised patients. Methods: We will conduct a scoping review of all study designs (i.e. no study design will per se be excluded from the proposed review) in accordance with the Preferred Reporting Items for Systematic reviews and Meta Analyses (PRISMA) statement. Results: We will provide descriptive analysis of the included studies/trials, i.e. no meta-analyses will be conducted. We will include studies on adult hospitalised patients receiving IV fluid for any reason. Studies must compare any crystalloid solution primarily buffered with lactate versus any primarily acetate buffered solution. All outcome measures will be reported. The quality of evidence will be assessed according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Conclusion: This outlined scoping review will provide a summary of the current body of evidence on the use, effects and side-effects of buffered crystalloid solutions. This will provide an important update of the current evidence on the use, of “buffered” crystalloid solutions including evidence of potential benefits and harms.