• Kristoffer Berg-Hansen, Nigopan Gopalasingam, Mette Glavind Bülow Pedersen, Jakob Tobias Nyvad, Nikolaj Rittig, Esben Søndergaard, Henrik Wiggers, Niels Møller, and Roni Nielsen.
• Department of Cardiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark. krisbe@rm.dk.
• Crit Care. 2025 Jan 17; 29 (1): 3030.

BackgroundLow-volume hypertonic solutions, such as half-molar lactate (LAC), may be a potential treatment used for fluid resuscitation. This study aimed to evaluate the underlying cardiovascular effects and mechanisms of LAC infusion compared to sodium-matched hypertonic sodium chloride (SAL).MethodsEight healthy male participants were randomized in a controlled, single-blinded, crossover study. Each participant received a four-hour infusion of LAC and SAL in a randomized order. Assessor-blinded echocardiography and blood samples were performed. The primary endpoint was cardiac output (CO) measured by echocardiography.ResultsDuring LAC infusion, circulating lactate levels increased by 1.9 mmol/L (95% CI 1.8-2.0 mmol/L, P < 0.001) compared with SAL. CO increased by 1.0 L/min (95% CI 0.5-1.4 L/min, P < 0.001), driven primarily by a significant increase in stroke volume of 11 mL (95% CI 4-17 mL, P = 0.002), with no significant change in heart rate. Additionally, left ventricular ejection fraction improved by 5 percentage points (P < 0.001) and global longitudinal strain by 1.5 percentage points (P < 0.001). Preload indicators were elevated during SAL infusion compared with LAC infusion. Concomitantly, afterload parameters, including systemic vascular resistance and effective arterial elastance, were significantly decreased with LAC infusion compared with SAL, while mean arterial pressure remained similar. Indicators of contractility improved during LAC infusion.ConclusionsIn healthy participants, LAC infusion enhanced cardiac function, evidenced by increases in CO, stroke volume, and left ventricular ejection fraction compared with SAL. Indicators of contractility improved, afterload decreased, and preload remained stable. Therefore, LAC infusion may be an advantageous resuscitation fluid, particularly in patients with cardiac dysfunction.Clinical Trial Registrationshttps://clinicaltrials.gov/ct2/show/NCT04710875 . Registered 1 December 2020.© 2025. The Author(s).

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