Acute myocardial mechanical responses to colloid and crystalloid volume loading: A randomized double‐blind crossover study

Aim The superiority of colloids over crystalloids for volume resuscitation remains uncertain despite theoretical advantages in intravascular expansion. We hypothesized that distinct myocardial mechanical responses may explain this discrepancy. Methods In this single‐centre, double‐blind, randomized crossover trial, participants received sequential 500‐ and 1000‐mL infusions of either Gelafundin 4% (colloid) or 0.9% sodium chloride (crystalloid), with a 7‐day washout before crossover. Left ventricular global longitudinal strain (GLS), torsion (TOR), left atrial strain (LAS) and right ventricular (RV) free wall strain curves were acquired by speckle‐tracking echocardiography. Functional data analysis was applied to entire strain curves to detect time‐specific differences across the cardiac cycle. Results Twenty healthy volunteers were enrolled (mean age 27.2 ± 4.3 years; 20% women). Conventional echocardiographic and hemodynamic parameters remained comparable across groups. GLS differed significantly between fluids around end‐systole (maximum difference −1%), favouring colloids. RV strain showed significant between‐fluid differences primarily during diastole (maximum difference +2%). LV torsion increased significantly with colloid (maximum difference +3%), with a fluid‐specific response during untwist. LAS exhibited the largest between‐group differences at both infusion volumes (maximum difference +6%), and within‐group analysis revealed distinct phase‐specific adaptations, predominantly affecting LA phasic function and LV twist–untwist dynamics. Conclusion Volume loading produces changes in GLS and RV longitudinal strain that are similar in pattern but greater in amplitude, favouring colloids, whereas twist mechanics and left atrial reservoir and conduit function exhibit distinct, volume‐dependent and fluid‐modulated myocardial deformation patterns.