Intradialytic exercise may improve hemodialysis efficiency. Because exercise interferes with thermal energy and fluid balance, relative blood volume changes (ΔBV%), arterial blood temperatures (Tart), mean arterial blood pressures, and heart rates (HR) were measured using different dialysate temperatures (Tdia). Four stable patients (age, 49.9 ± 7.7 years) were studied during 22 treatments that either maintained Tdia at 35.9°C ± 0.1°C (standard) or provided maximum extracorporeal cooling (cool, Tdia = 34.8°C ± 0.8°C) in attempts to maintain a constant Tart. Patients exercised for 1 hr at a resistance of 21 ± 5 W on a stationary bicycle ergometer. Energy expenditure monitored by indirect calorimetry increased from 117 ± 38 W (baseline) to 338 ± 116 W (exercise). Mean arterial blood pressures increased by 7 ± 7 mmHg with cool Tdia, but remained unchanged (−1 ± 4 mmHg) with standard Tdia (p < 0.05). However, the increase in Tart was smaller with cool (0.1°C ± 0.3°C) than with standard (0.3°C ± 0.2°C) Tdia (p < 0.05). The larger increase in O2 uptake per change in HR (68 ± 56 vs 38 ± 17 ml/beat) indicated an increase in stroke volume when cool dialysate was used (p = NS). Exercise produced a small (0.95% ± 0.95%), but significant, decrease in ΔBV% that reversed at the end of exercise. Intradialytic exercise was well tolerated, especially when Tdia was lowered such that hemodynamic stress to dissipate excess heat through the cutaneous circulation was reduced and blood pressure stability was improved.
Copyright © 1998 by the American Society for Artificial Internal Organs