Association of cumulative fluid balance trajectories with haemodynamics, inflammation, and long-term mortality in critically ill patients with circulatory failure: bridging physiology and causal inference with target trial emulation. Comment on Br J Anaesth 2026; 136: 542–51

The article comments on a study by Ruste and colleagues and physiological reflections by Ripollés-Melchor and colleagues published in the British Journal of Anaesthesia. The authors emphasize that cumulative fluid balance trajectories should be viewed as integrative markers of underlying shock pathophysiology, rather than as completely independent and modifiable exposures. The article highlights the importance of this perspective as a foundation for further analyses. The authors point out several methodological aspects that could improve the causal interpretability of such analyses. The goal is to better guide future research in this field. The article focuses on bridging physiological knowledge with causal inference and target trial emulation.