#1806 Cycling is safe – effect of intradialytic cycle ergometry on cerebral oxygenation and cognitive function – a pilot study

Abstract

Abstract Background and Aims Patients on chronic hemodialysis benefit from intradialytic exercise with improvements in endurance, muscle strength and health-related quality of life. It is not known whether the increased oxygen demand during intradialytic exercise negatively affects cerebral oxygenation and cerebral function. The aim of the study was to assess the risk of cerebral undersupply by measuring cerebral oxygenation, perfusion and cognitive function during and after intradialytic ergometer training. Method Twelve patience on maintenance hemodialysis (HD) trice weekly were included in the study. In an initial ramp test, using bed cycle ergometer, we first determined the maximum physical strength (Pmax) at the level of exhaustion (HD A). Then, one hour after start of a second HD (HD B), patients performed 40%, 50% and 60% of Pmax for 6 min. Pulmonary function tests, blood volume (BVM), cardiac output (by electrical cardiometry), regional cerebral oxygen saturation (rSO2) (by near-infrared spectroscopy) and cerebral blood flow (CBF, by Doppler sonography) were measured. The relative changes in rSO2, CBF and hematocrit were used to calculate cerebral oxygen supply (DO2). Cognitive tests (Stroop, Trail Making and Mini Addenbrookes Cognitive Examination Test) were performed before and after HD sessions with and, as controls, without ergometry (HD-C). Results Median age was 68 (42-85) years, 9/12 were male, complete data set was obtained in 10 patients. During step test exercise (HD B), at the highest exercise level (according to Borg (1-10) 6.75 ± 2.9), rSO2 increased (+6 ± 9%, p=0.034) without a significant change in CBF. In the meantime, relative blood volume decreased during ergometry (-5.8 ± 2.73%; p=0.002), causing a temporary increase of hematocrit. Despite a small decrease in CBF in 3 patients, the mean change of rSO2, CBF and hematocrit always had a positive trend in all patients, as a surrogate of stable cerebral oxygen supply (Table 1). In comparative cognitive tests (B vs. C), we observed no significant changes in cognitive functions. Conclusion In this pilot study, intradialytic bed-cycle ergometry during the first hour of HD for <20 min at 40-60% of patients’ individual maximum intensity had no negative effects on cerebral oxygenation and function. Specific studies testing the safety intradialytic exercise with different conditions, such as increasing intensity or duration, are needed.