Lack of Evidence to Support Increased Salt For Orthostatic Intolerance Syndromes: A Systematic Review and Meta-Analysis.

Abstract Background Guidelines recommend increased salt intake as first-line in the management of orthostatic hypotension and syncope. There have been no systematic reviews of this intervention. We sought to summarize the evidence for this recommendation in patients with orthostatic intolerance. Methods We planned a systematic review and meta-analysis of studies in PubMed, EMBASE and CINAHL. Individuals with orthostatic intolerance syndromes were included. Intervention of interest was increased salt intake. Primary outcome measures included reduced falls and injuries, and rates of syncope and presyncope. Results Fourteen studies were eligible including participants with orthostatic hypotension, syncope, Postural Orthostatic Tachycardia Syndrome, and idiopathic orthostatic tachycardia (n=391). Mean age was 35.6 (±15) years. All studies were small and short-term (0-60 days). No study assessed the effect of salt on falls. Meta-analysis demonstrated that during head-up tilt, time to presyncope with salt intake increased by 1.57 minutes (95% confidence interval (CI), 1.26 to 1.88), systolic blood pressure increased by 12.27 mm Hg (95% CI, 10.86 to 13.68), and heart rate decreased by -3.97 beats per minute (95% CI, -4.08 to -3.86), compared with control. Salt had a minimal effect on supine blood pressure. Studies evaluating symptoms reported improvement with salt. Methodological quality of studies was low, with high heterogeneity. Conclusions Our meta-analysis provides low-quality evidence of a short-term improvement in orthostatic tolerance. There were no long-term clinical trials demonstrating the efficacy on clinical or safety outcomes. Overall, there is a paucity of evidence to support a cornerstone recommendation in the management of orthostatic intolerance.