BACKGROUND: Very aggressive ultrafiltration rate (lasting 3.5–4 h) may result in inadequate hemodialysis (HD). Our aim was to characterize HD-induced cardiovascular adaptation and its links to fluid removal during 4- vs. 5-h HD sessions.

MATERIAL AND METHODS: The study involved 50 HD patients. A Cardioscreen device (Messtechnik, Ilmenau, Germany) was used to perform non-invasive hemodynamic measurements during mid-week HD sessions. Body fluids and nutritional status were assessed with a Body Composition Monitor (Fresenius Medical Care). Clinical and laboratory data were also analyzed.

RESULTS: It was shown that when comparing 3 times a week 4- vs. 5-h dialysis sessions, body mass index (BMI [kg/m²]), Kt/V, and ultrafiltration volume (UFV [mL]) were significantly lower in the 4-h dialysis group (23.1±3.5 vs. 27.1±4.7; 1.36±0.28 vs. 1.55±0.23; 1770±601 vs. 2831±836; P<0.05, respectively). Cardiac index (CI [L/min/m²]) and thoracic fluid content (TFC [1/kW]) were significantly reduced in 4-h dialysis sessions (3.1±0.6 to 2.7±0.7; 35.1±8.4 to 32.8±6.8; P<0.05, respectively). In patients treated with 5-h dialysis sessions, we found that heart rate (HR [bpm]) was significantly increased (69±10 to 74±15; P<0.05) and TFC was reduced (34.3±8.9 to 31.5±8.2; P<0.05). In patients treated with 4-h dialysis sessions, systemic vascular resistance index (SVRI [dyn·s·cm^–5/m²]) increased from 2369±799 before HD to 2592±735 after HD (P=0.342).

CONCLUSIONS: The obtained data indicate that in extended (5-h) HD sessions, hemodynamic compensation occurred with increased HR, while in short (4-h) HD sessions, compensation occurred with increased SVRI. Providing longer but less intensive HD is more physiologic than the conventional therapy, and will improve patient tolerability and clinical outcomes.

Keywords: arterial pressure, Cardiac Output, Cardiography, Impedance, Dialysis