Factors associating with oxygenation of lower-limb muscle tissue in hemodialysis patients

AIM: To evaluate the lower-limb muscle oxygenation in hemodialysis (HD) patients and identify the factors associating with muscle oxygenation. METHODS: Sixty-seven HD patients (53 men and 14 women; mean age, 67.1 ± 1.2 years; mean HD duration, 5.6 ± 0.9 years) were recruited. In addition, 15 healthy individuals (nine men and six women; mean age, 38.2 ± 4.6 years) were recruited as the control group. Lower-limb muscle regional saturation of oxygen (rSO(2)) was monitored on the lateral side of the gastrocnemius muscle before HD using an INVOS 5100C (Covidien Japan, Tokyo, Japan), which utilizes near-infrared spectroscopy. Here, we evaluated the association between lower-limb muscle rSO(2) and clinical parameters. RESULTS: The rSO(2) values were significantly lower in patients undergoing HD than in healthy individuals (50.0% ± 1.7% vs 76.8% ± 2.5%, P < 0.001). Lower-limb muscle rSO(2) showed significant positive correlations with diastolic blood pressure, blood urea nitrogen concentration, serum creatinine concentration, serum potassium concentration, serum inorganic phosphate concentration, and serum albumin concentration as well as negative correlation with HD duration. We conducted a multiple linear regression analysis using parameters that were significantly correlated with the lower-limb muscle rSO(2) in a simple linear regression analysis. Multiple regression analysis demonstrated that lower-limb muscle rSO(2) was independently associated with serum inorganic phosphate (standardized coefficient: 0.27) and serum albumin concentrations (standardized coefficient: 0.24). In addition, there were no differences in lower-limb muscle rSO(2) between diabetic and non-diabetic HD patients. This study has several limitations. Firstly, its sample size was relatively small. Secondly, we could not evaluate the association between lower-limb muscle rSO(2) and calculated nutritional markers, including normalized protein catabolic rate and body mass index, anthropometric measurements representing nutritional status, and the severity of protein-energy wasting. Finally, we did not routinely examine the arterial vascular status of HD patients without symptoms of peripheral artery disease. As such, it is possible that some HD patients with subclinical peripheral artery disease may have been included in this study. CONCLUSION: In HD patients, the oxygenation of lower-limb muscle tissue was associated with serum inorganic phosphate and albumin concentrations, both of which represent nutritional status.