Kidney Week

Abstract: TH-PO0861

Urea Reduction Rate, Ultrafiltration Rate, and Middle Cerebral Artery Pulsatility Index During Incident Hemofiltration

Session Information

• Dialysis: Prescription, Physiology, and Treatment Optimization
  October 22, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Dialysis

• 801 Dialysis: Hemodialysis and Frequent Dialysis

Authors

• Ramirez-Calvillo, Luis Daniel, Instituto Nacional de Cardiologia Ignacio Chavez, Mexico City, CDMX, Mexico

Luis Daniel Ramirez-Calvillo, MD, MSc

• Cortez, Brenda, Instituto Nacional de Cardiologia Ignacio Chavez, Mexico City, CDMX, Mexico

Brenda Cortez, MD

• Garza Romero, Maria Fernanda, Instituto Nacional de Cardiologia Ignacio Chavez, Mexico City, CDMX, Mexico

Maria Fernanda Garza Romero, MD

• Leal, Gabriela, Instituto Nacional de Cardiologia Ignacio Chavez, Mexico City, CDMX, Mexico

Gabriela Leal

• Zepeda Pérez, Jorge Alejandro, Instituto Nacional de Neurologia y Neurocirugia Manuel Velasco Suarez, Mexico City, CDMX, Mexico

Jorge Alejandro Zepeda Pérez, MD

• Lopez-Gil, Salvador, Instituto Nacional de Cardiologia Ignacio Chavez, Mexico City, CDMX, Mexico

Salvador Lopez-Gil, MD

Background

Incident renal replacement therapy exposes patients to abrupt osmotic and hemodynamic changes that may compromise cerebral perfusion. Whether the urea reduction rate (URR) or ultrafiltration rate (UFR) modify cerebrovascular resistance during the first hemofiltration (HF) session has not been characterized with simultaneous transcranial Doppler (TCD) and measured plasma osmolality.

Methods

Single-center, prospective, observational cohort of adults initiating HF, hemodynamically stable, with adequate transtemporal window. The right MCA was insonated and plasma osmolality measured by freezing-point depression osmometry at pre-session (T1), mid-session (T2), end-session (T3), and 2h post-session (T4). Primary outcome: MCA pulsatility index (MCA-PI) trajectory by Friedman test. Secondary: Spearman correlations between URR (T1–T3), UFR, and intradialytic ΔMCA-PI.

Results

Fifteen patients were analyzed (age 60±11 years; 73% male; baseline BUN 104±23 mg/dL). Delivered therapy: URR 30.3±6.7%, UFR 6.2±4.5 mL/kg/h. Intradialytic hypotension occurred in 13%. MCA-PI did not change across the session (T1 0.38±0.14; T2 0.39±0.16; T3 0.38±0.16; T4 0.42±0.16; Friedman p=0.356), despite a fall in measured plasma osmolality of 12 mOsm/kg from T1 to T3 (p<0.001) and stable mean arterial pressure (p=0.671). Neither URR (ρ=+0.16, p=0.58) nor UFR (ρ=−0.04, p=0.88) correlated with ΔMCA-PI.

Conclusion

In incident HF patients, MCA-PI remained stable throughout the session and early recovery despite significant osmolality reduction. No association between URR or UFR and ΔMCA-PI suggests preserved cerebrovascular tone within prescribed ranges of solute clearance and volume removal. These findings provide a methodological reference for future studies on neurologically safe convective therapy.

Figure 1. MCA-PI trajectory during incident HF (A) and its correlation with URR (B) and UFR (C). n=15. Friedman test (A); Spearman (B, C).