Abstract
HD tissue hypoxia associates with organ dysfunctions. OER, the ratio between SaO2 and central-venous-oxygen-saturation, could estimate oxygen requirements during sessions, but no data are available. We evaluated OER behavior in 20 HD patients with permanent central venous catheter (CVC) as vascular access. Pre-HD OER (33.6 ± 1.4%; M ± SE) was higher than normal (range 20–30%). HD sessions increased OER to 39.2 ± 1.5% (M ± SE; p < 0.05) by 30′ and to 47.4 ± 1.5% (M ± SE; p < 0.001) by end of treatment (delta 40%). During HD sessions of the long and short interdialytic intervals, OER values overlapped, suggesting no influence of patient’s hydration status shifts. OER increased (p < 0.05) after 30′ of isolated HD (zero ultrafiltration), but not during isolated ultrafiltration (zero dialysate flow), suggesting a role for blood-membrane-dialysate interaction, independent of volume reduction. In ten patients, individual variability of pre-HD OER was low and repeatable (maximum calculated difference over time 6.6%), and negatively correlated with HD-induced OER increments (r = 0.860; p < 0.005), suggesting a decline in the adaptive response along with resting OER increments. In 30 prevalent patients, adjusted multivariate analysis showed that pre-HD OER (HR = 0.88, CI 0.79–0.99, p = 0.028) and percent HD-induced OER (HR = 1.04, CI 1.01–1.08, p = 0.015) were both associated with mortality, with threshold values respectively <32% and >40%. In HD patients with CVC as vascular access, OER is a cheap, easily measurable and repeatable parameter useful to assess intradialytic hypoxia, and a potential biomarker of HD related stress and morbidity, helpful to recognize patients at increased risk of mortality.
Highlights
Values over 50% are considered indicative, in intensive care unit (ICU) patients, of hemodynamic shock, worse prognosis and lower survival rate[9,10,11]
Our aims were the following: to describe the changes, if any, of OER during HD sessions; to evaluate if OER is sensibly affected by the interdialytic changes in patient’s hydration status; to verify if OER is differently induced by isolated UF dialysis or isolated Diffusion dialysis; to establish its stability in the individual patient, and to evaluate possible associations with clinical outcomes
We demonstrate that OER changes significantly during HD sessions, is not affected by the interdialytic shifts of patient’s hydration status, is differently induced by isolated Diffusion dialysis (iD) and isolated UF dialysis (iUF) and is stable and repeatable in the individual patient
Summary
Values over 50% are considered indicative, in intensive care unit (ICU) patients, of hemodynamic shock, worse prognosis and lower survival rate[9,10,11]. Nephrologists, who are less familiar with respiratory parameters of acid base balance, may be reluctant to use OER. ScvO2, the second parameter necessary to calculate OER, cannot be measured in every hemodialysis patient, but only in those with central venous catheter (CVC) as vascular access. To the best of our knowledge, no OER data are available in HD patients and only few papers deal with ScvO2, which is less precise than OER. Our aims were the following: to describe the changes, if any, of OER during HD sessions; to evaluate if OER is sensibly affected by the interdialytic changes in patient’s hydration status; to verify if OER is differently induced by isolated UF dialysis (iUF) or isolated Diffusion dialysis (iD); to establish its stability in the individual patient, and to evaluate possible associations with clinical outcomes
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