Treatment standards for hypotension on hemodialysis - physiology-based phenotyping of acute and chronic scenarios

Intradialytic hypotension (IDH) is a pervasive complication of hemodialysis, yet the clinical scenarios in which IDH occurs vary widely. To guide treatment standards, we describe five cases corresponding to typical IDH phenotypes: (i) acute intradialytic allergic event, with abrupt early hypotension reproducible with specific dialyzers; (ii) acute unexpected IDH due to autonomic imbalance (here, postprandial), with disproportionate symptoms despite modest blood pressure drops; (iii) chronic IDH due to hypovolemia from an overly ambitious target weight; (iv) chronic IDH with ultrafiltration-refill mismatch, where blood volume falls despite fluid overload; and (v) chronic hypotension due to limited cardiac reserve. In the acute setting (i-ii), immediate rescue-interruption of ultrafiltration and/or the dialysis session, Trendelenburg positioning, and isotonic fluid bolus-should be combined with rapid bedside phenotyping to identify allergic, autonomic, hypovolemic or cardiac triggers. Material hypersensitivity must be recognized, as rechallenge can be harmful, but is avoidable by dialyzer substitution. In the chronic setting (iii-v), prevention centers on reduced ultrafiltration stress: lower ultrafiltration rates with longer or more frequent sessions, and objective reassessment of target weight. The chronic phenotypes are often clinically indistinguishable yet require different corrections-a higher target weight in hypovolemia, gentler fluid removal that supports refilling in refill mismatch, and acceptance of some fluid overload with limited cardiac reserve-making objective volume assessment the decisive first step. The unifying concern is organ hypoperfusion, not blood pressure. Future trials should enroll phenotype-defined rather than heterogeneous 'IDH-prone' populations and use hard outcomes, end-organ ischemia and patient-reported outcomes.