Vasopressin is a key regulator of water and vascular homeostasis, acting through V2 receptors to control renal water reabsorption and through V1a receptors to influence vascular tone. Copeptin, a stable surrogate marker of vasopressin release, provides a reliable measure of vasopressin activity. In hemodialysis, where ultrafiltration and osmotic shifts challenge fluid balance, the contribution of vasopressin to intradialytic blood pressure regulation remains uncertain. Elevated copeptin levels in dialysis patients have been associated with interdialytic weight gain and adverse cardiovascular outcomes. This study (CODIALHYP) tests the hypothesis that vasopressin activity, assessed through copeptin levels, is associated with intradialytic hypertension. The primary objective is to evaluate the relationship between copeptin concentrations and blood pressure changes during hemodialysis. Secondary objectives include assessing whether vasopressin's antidiuretic effect is preserved in hemodialysis patients and exploring the contribution of other hormonal pathways involved in fluid and vascular regulation.

This study investigates the role of vasopressin activity, assessed through copeptin levels, in the hemodynamic changes occurring during hemodialysis. Vasopressin is involved in both water homeostasis and vascular regulation, yet its contribution to intradialytic blood pressure variations remains insufficiently characterized. Hemodialysis induces rapid shifts in osmotic gradients and extracellular volume, creating conditions in which vasopressinmediated mechanisms may influence vascular tone and fluid balance. The research is based on a retrospective observational design involving chronic hemodialysis patients. Clinical records were reviewed to collect blood pressure measurements obtained before, during, and after dialysis sessions, as well as laboratory data including copeptin, plasma osmolality, cortisol, and aldosterone.

When residual diuresis was present, urinary volume and osmolality were documented. Additional information related to dry weight, ultrafiltration parameters, and routine markers of fluid balance was extracted from standard clinical evaluations.

These data provide a framework for examining the association between vasopressin activity and intradialytic hypertension, and for exploring the contribution of other hormonal pathways involved in fluid and vascular regulation.

Inclusion Criteria:

• Adult patients (≥18 years old).
• Undergoing chronic hemodialysis treatment > 3 months.
• Availability of routine predialysis blood samples for copeptin and biochemical measurements.
• Availability of blood pressure recordings before, during, and after hemodialysis sessions.

No exclusion criteria if inclusion criteria is filled

The study population consists of adult patients (≥18 years old) undergoing chronic hemodialysis for more than three months. All included patients were clinically stable, not hospitalized at the time of data collection, and received treatment within the ALTIR network (Association Lorraine pour le Traitement de l'Insuffisance Rénale).

Data were obtained from three hemodialysis centers: Nancy-Brabois, Champelle, and Épinal.

The investigators designed the study as a pilot study and do not intend to share IPD with other study