Acid-base and electrolyte changes following maximal and submaximal exercise in hemodialysis patients

Maximal treadmill exercise was conducted in nine hemodialysis patients and in 15 unconditioned healthy subjects. Exercise capacity in the dialysis patients, as measured by duration of exercise, maximal oxygen consumption (VO2 max), and workload achieved (METS) was approximately 50% of that of the nonuremic volunteers. Four of the dialysis patients were studied on both dialysis (predialysis) and nondialysis days and also at 60% of VO2 max for 30 minutes on a nondialysis day. In these individuals, serum electrolytes, acid-base, and biochemical parameters were analyzed preexercise and at regular intervals following cessation of treadmill exercise. Transient metabolic acidosis and mild hyperkalemia developed after maximal exercise but not after prolonged submaximal exercise. Patients were slightly more acidotic and hyperkalemic on a dialysis day compared to a nondialysis day. Cardiopulmonary performance was similar on both days. These changes in serum electrolytes and acid-base parameters provide documentation of the extent of biochemical changes that develop following exercise in dialysis patients.