This prospective, multicenter observational study aims to describe how often intradialytic hypotension (IDH) occurs and to identify its risk factors in adult patients receiving maintenance hemodialysis. Intradialytic hypotension is a common complication during dialysis that can lead to symptoms, organ hypoperfusion, and interruption of treatment.

Participants will be adults on regular maintenance hemodialysis who meet predefined inclusion and exclusion criteria. Routine clinical information will be collected, including demographics, primary kidney disease, comorbidities, medications, dialysis vintage, dialysis prescription (ultrafiltration volume and rate, dialysate composition, treatment time), and standard laboratory tests. During a defined observation period, blood pressure and related symptoms will be recorded across dialysis sessions to document the frequency, severity, and patterns of IDH.

The main goals are to estimate the incidence and prevalence of intradialytic hypotension in maintenance hemodialysis patients and to explore potential risk factors, such as patient characteristics, cardiovascular status, volume status, and dialysis-related parameters. The findings may help clinicians better recognize patients at high risk of IDH and optimize dialysis prescriptions and monitoring strategies to reduce the occurrence of IDH and its adverse consequences.

This is a prospective, multicenter, observational study designed to characterize the epidemiology and risk factors of intradialytic hypotension (IDH) in adult patients undergoing maintenance hemodialysis. No study-specific interventions will be assigned; all dialysis treatments and medical therapies will be conducted according to routine clinical practice at each participating center.

Eligible participants are adults receiving thrice-weekly or regular maintenance hemodialysis for end-stage kidney disease. After obtaining informed consent (as required by local regulations), baseline data will be collected from the medical record and patient interview. Baseline variables will include:

Demographics (age, sex, body mass index, smoking status) Primary kidney disease and dialysis vintage Comorbidities (e.g., diabetes mellitus, hypertension, cardiovascular disease, heart failure, arrhythmia) Usual medications, with a focus on antihypertensive agents, diuretics, and cardiovascular drugs Pre-dialysis clinical parameters (weight, dry weight, interdialytic weight gain, pre-dialysis blood pressure) Routine laboratory values (e.g., hemoglobin, albumin, electrolytes, calcium-phosphate metabolism indices, markers of inflammation and nutrition, as available) Dialysis prescription and treatment-related parameters will be documented, including dialyzer type, blood flow rate, dialysate flow, dialysate composition (sodium, calcium, bicarbonate), treatment duration, and planned and achieved ultrafiltration volume and ultrafiltration rate.

During the observation period (covering a predefined number of consecutive dialysis sessions per patient), blood pressure will be monitored according to local standard practice (for example, before dialysis, at regular intervals during dialysis, and at the end of treatment). Episodes of intradialytic hypotension will be identified using a pre-specified definition (e.g., absolute blood pressure thresholds and/or drop from baseline, with or without associated symptoms), which will be applied consistently across all centers. When feasible, associated symptoms (such as dizziness, cramps, chest discomfort, nausea) and interventions (e.g., reduction or cessation of ultrafiltration, saline infusion, change in dialysate temperature, adjustment of position, or early termination of dialysis) will be recorded.

The primary analyses will describe:

The incidence and prevalence of intradialytic hypotension in this maintenance hemodialysis population The distribution of IDH episodes by dialysis session phase (early, middle, late), severity, and need for intervention

Secondary analyses will evaluate potential risk factors for IDH. These may include:

Baseline patient characteristics (age, sex, body mass index, primary disease, comorbidities) Indicators of cardiovascular function and volume status (pre-dialysis blood pressure, interdialytic weight gain, dry weight assessment) Laboratory parameters reflecting anemia, nutritional status, mineral metabolism, and inflammation Dialysis-related factors (treatment time, ultrafiltration volume and rate, dialysate sodium and temperature, antihypertensive medications taken before dialysis) Multivariable regression models or other appropriate statistical methods will be used to examine associations between candidate risk factors and the occurrence of IDH, while adjusting for potential confounders. Subgroup or sensitivity analyses may be performed according to age groups, presence of diabetes or cardiovascular disease, or different ultrafiltration rate categories, depending on sample size and data completeness.

This study is not intended to test a specific therapeutic intervention but to provide a comprehensive, real-world description of intradialytic hypotension and its determinants in maintenance hemodialysis patients across multiple centers. The results may support the development of risk stratification tools and guide future interventional studies aimed at preventing or mitigating intradialytic hypotension.

Inclusion Criteria:

• Adults (≥18 years) with end-stage renal disease on maintenance hemodialysis
• Receiving thrice-weekly (or routine) in-center hemodialysis for ≥3 months before enrollment
• Scheduled for a standard hemodialysis session of approximately 3-5 hours on the study day
• Able to provide informed consent (or via legally authorized representative, if applicable)

Exclusion Criteria:

• Acute medical instability precluding observation of a routine dialysis session (e.g., active sepsis requiring vasopressors, uncontrolled arrhythmias)
• Recent acute coronary syndrome or stroke within 3 months
• Pre-dialysis systolic blood pressure <90 mmHg on the study day before starting dialysis
• Ongoing active major bleeding or anticipated urgent transfusion during the session
• Pregnancy
• Participation in an interventional trial expected to alter intradialytic blood pressure during the observed session

Adults with end-stage renal disease receiving routine maintenance hemodialysis at participating centers. Consecutive eligible patients will be observed during one scheduled dialysis session to estimate single-session IDH incidence and explore associated factors.