Systemic haemodynamics in haemodialysis: intradialytic changes and prognostic significance

BACKGROUND: Although haemodialysis (HD) leads to alterations of systemic haemodynamics that can be monitored using dilution methods, there is a lack of data on the diagnostic and prognostic significance of haemodynamic monitoring during routine HD. METHODS: In this multicentre study, we measured cardiac index (CI), access flow (AF) and central blood volume index (CBVI) during a single HD session in stable HD patients (n = 215) using the Transonic HD03 monitor (Transonic, Ithaca, NY, USA). Systemic CI (SCI) was defined as CI corrected for AF. In a subset of patients (n = 82), total end-diastolic volume index (TEDVI) and total ejection fraction (TEF) were derived from dilution curves. Data were correlated with clinical parameters, cardiac biomarkers and bioimpedance measurements (body composition monitor; Fresenius Medical Care, Homburg, Germany). Mortality was assessed prospectively after a median follow-up of 2.6 years. RESULTS: Median CI, CBVI and AF were 2.8 L/min/m(2) (interquartile range 2.4–3.4), 15 mL/kg (14.5–15.7) and 980 mL/min (740–1415), respectively, at the beginning of HD. At the end of HD, CI, CBVI and AF significantly fell by −10% (−22 to 3, P < 0.0001), −9% (−23 to 3, P < 0.0001) and −4% (−13 to 5, P = 0.0004), respectively. Peripheral resistance (PR) increased slightly (P = 0.01) and blood pressure fell by −6/−3 mmHg to 128/63 mmHg (P < 0.0001). Independent predictors of ΔCI were age and ultrafiltration rate, whereas AF, overhydration and PR were protective. TEF was strongly associated with mortality [area under the dilution curve 0.77, P < 0.0001], followed by TEDVI (0.72, P = 0.0002) and SCI (0.60, P = 0.02). CONCLUSIONS: HD leads to a reduction of CI due to ultrafiltration. Haemodynamic monitoring identifies a significant number of HD patients with cardiac impairment that are at risk for increased mortality.