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Increased risk of Staphylococcus epidermidis peritonitis in patients on dialysate containing 1.25 mmol/L calcium
B Piraino1, J Bernardini, J L Holley
1Department of Medicine, University of Pittsburgh, PA.
Abstract:
Peritoneal macrophage function is decreased in vitro in the presence of dialysate with 1.25 mmol/L calcium compared with that containing 1.75 mmol/L calcium. Theoretically, patients using this dialysate may have a higher risk of peritonitis. Nineteen patients on continuous ambulatory peritoneal dialysis (CAPD) or continuous cycling peritoneal dialysis (CCPD) were converted from dialysate with 1.75 mmol/L calcium (mean time, 33 +/- 26 months) to that with 1.25 mmol/L calcium, for some or all exchanges (mean time, 10 +/- 4.7 months). Peritonitis rates were compared with 19 control patients who remained on dialysate with 1.75 mmol/L calcium. The two groups were matched for the proportion of diabetics, sex, age, use of the Y-set, and dialysis modality (CAPD, CCPD). Peritonitis rates were similar in the study patients before conversion to 1.25 mmol/L calcium dialysate and in the control patients (0.49 v 0.58 episodes/patient-year, respectively). After conversion to dialysate with 1.25 mmol/L calcium, the peritonitis rate was 0.82 episodes/patient-year contrasted to 0.58 episodes/patient-year in the control patients (P = 0.09). The peritonitis rate due to Staphylococcus epidermidis was 0.51 episodes/patient-year when 1.25 mmol/L calcium dialysate was used, and 0.19 episodes/patient-year for the comparable period in the control patients on 1.75 mmol/L calcium dialysate (P = 0.005). The proportion of peritonitis episodes due to S epidermidis increased from 20% to 61% after conversion to 1.25 mmol/L calcium (P = 0.01). The increased risk of peritonitis due to S epidermidis in patients using dialysate with 1.25 mmol/L calcium is consistent with a previous study demonstrating that clearance of S epidermidis by peritoneal macrophages is less effective with a decrease in the dialysate calcium content.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Lowering dialysate calcium to 1.25 mmol/L in peritoneal dialysis may increase peritonitis risk, particularly from Staphylococcus epidermidis. This change impacts peritoneal macrophage function, potentially leading to more infections in patients on continuous ambulatory peritoneal dialysis (CAPD) and continuous cycling peritoneal dialysis (CCPD).
Area of Science:
- Nephrology
- Infectious Diseases
- Biomedical Science
Background:
- Peritoneal macrophage function is impaired in vitro with lower dialysate calcium (1.25 mmol/L vs. 1.75 mmol/L).
- Reduced macrophage function theoretically increases peritonitis risk in patients undergoing peritoneal dialysis.
Purpose of the Study:
- To investigate the clinical impact of switching peritoneal dialysis patients from 1.75 mmol/L calcium dialysate to 1.25 mmol/L calcium dialysate on peritonitis rates.
- To determine if lower dialysate calcium levels correlate with an increased incidence of peritonitis, specifically caused by Staphylococcus epidermidis.
Main Methods:
- A cohort study comparing 19 patients switched to 1.25 mmol/L calcium dialysate with 19 control patients on 1.75 mmol/L calcium dialysate.
- Patients were on continuous ambulatory peritoneal dialysis (CAPD) or continuous cycling peritoneal dialysis (CCPD).
- Peritonitis rates and causative organisms were analyzed before and after the dialysate calcium switch, with matching for key demographic and clinical factors.
Main Results:
- While overall peritonitis rates showed a trend towards increase (0.82 vs. 0.58 episodes/patient-year, P=0.09), the rate of peritonitis due to Staphylococcus epidermidis significantly increased (0.51 vs. 0.19 episodes/patient-year, P=0.005).
- The proportion of peritonitis episodes attributed to S. epidermidis rose from 20% to 61% after switching to the lower calcium dialysate (P=0.01).
- These findings align with in vitro data showing reduced S. epidermidis clearance by macrophages with decreased calcium.
Conclusions:
- Switching to 1.25 mmol/L calcium dialysate in peritoneal dialysis is associated with a significant increase in Staphylococcus epidermidis peritonitis.
- The findings suggest that lower dialysate calcium content may compromise peritoneal host defenses against specific bacterial pathogens.
- Further research is warranted to confirm these findings and explore strategies to mitigate this increased infection risk.