Exercise tolerance in patients on chronic hemodialysis

Twenty-two patients on chronic hemodialysis were tested on a bicycle ergometer to determine their near-maximal physical work capacity. The patients were found to have low physical work capacity that averaged 51.6 +/- 3.8 (SE)% predialysis and 50.3 +/- 3.7% postdialysis, when compared with the physical work capacity of healthy control subjects. The exercise was stopped when patients complained of muscular fatigue, and the work load at this point was considered their subjective maximal work capacity. At this stage the patients had high blood lactic acid levels and an increased double product (systolic blood pressure x heart rate), the latter indicating a high stage of cardiac output. The oxygen consumption and oxygen pulse were similar to those obtained from control individuals at the same work load. This study suggests that limited physical work capacity of chronic hemodialysis patients is due to early muscular fatigue. This phenomenon is associated with the rapid onset of anaerobic metabolism and may thus be caused by limited maximal oxygen uptake.