The relationship between phosphorus level and peak oxygen uptake in hemodialysis patients awaited for renal transplantation

Abstract

Introduction: End-stage renal disease (ESRD) is one of the most common diseases, which affects many aspects of patients’ lives. The measurement of exercise capacity through peak oxygen uptake is an important factor in predicting mortality and survival in patients with ESRD. Objectives: In the current study, we aimed to examine the relationship between phosphorus level and VO2 uptake in renal transplant candidates receiving hemodialysis. Patients and Methods: Thirty renal transplant candidates on hemodialysis were evaluated through spirometry and exercise tests. Then, the results were compared according to the inclusion criteria of age, gender, and phosphorus level. Results: All of cases were male with the mean age of 37.93±10.48 years (range; 20-55 years). Mean VO2 max was 23.46±8.22 mL/kg/min (range; 6.88 to 43.44 mL/kg/min). The mean phosphorus level was 6±2.3 mg/dL (range; 2-10.6 mg/dL) since eight patients had high levels of phosphorus (more than 5.5 mg/dL). In patients with low phosphorus level an abnormal VO2 max was detected (P=0.027). Furthermore, Fisher’s exact test reflected a significant association between higher levels of phosphorus with normal VO2 max (P=0.029). Conclusion: In hemodialysis, decreased blood phosphorus is a predisposing factor for reduced exercise capacity, while hypophosphatemia may lower VO2 max through reducing energy of skeletal muscles. The relationship between phosphorus level and VO2 max may be related to morbidity in hemodialysis patients. Hence, treatment modalities reducing serum levels of phosphorus should be conducted with caution in some patients.