Nitric oxide is a marker of peritonitis in patients on continuous ambulatory peritoneal dialysis

The aim of this study was to determine whether nitric oxide (NO) production is altered during peritonitis in patients receiving continuous ambulatory peritoneal dialysis (CAPD), and if so, whether there is an association between this alteration and the severity and prognosis of CAPD-induced peritonitis. The study population comprised 30 patients with 30 episodes of peritonitis. Thirteen patients without peritonitis were used as CAPD-control, and eighteen patients with normal renal function were used as normal-control. Total NO metabolites (NOx; nitrite + nitrate) were measured by the Griess method to reflect nitric oxide production. Peritoneal dialysate effluent and plasma were collected from 30 patients during episodes of peritonitis every day for the first 3 days, and then every 3 days for 2 weeks or until the patients were discharged. Plasma NOx levels in the control, CAPD-control, and CAPD-peritonitis groups were 87.0 +/- 11.5, 163.0 +/- 30.7 and 146.3 +/- 18.1 microM, respectively. Dialysate NOx levels in the CAPD-control and CAPD-peritonitis groups were 91.8 +/- 13.1 and 103.8 +/- 14.1 microM, respectively, and dialysate NOx levels did not differ between the two groups. The peak dialysate/plasma (D/P) ratios during the acute phase exceeded 1.0 in 46.7% of the patients of the CAPD-peritonitis group. The D/P ratios of NOx levels before and after treatment were 1.03 +/- 0.07 and 0.56 +/- 0.05, respectively. On the contrary, NOx levels in dialysate after treatment were not decreased, but those in plasma were increased after effective treatment. The peak D/P ratio increased 2.1-fold in the bacterial peritonitis group and 2.3-fold in the fungal peritonitis group, compared with the CAPD-control group. The lowest D/P ratios after treatment were similar to those in the CAPD-control group in patients with effective treatment, but remained 1.5-fold higher in patients for whom treatment was ineffective. In the evolutional study, the D/P ratios of NOx levels gradually declined to CAPD-control group levels (6.6 +/- 2.5 days) after effective antibiotic treatment, but it took longer for leukocyte counts in the peritoneal dialysate effluents (3.8 +/- 1.2 days) to normalize. In 5 patients with refractory peritonitis (Candida infection in three, Staphylococcus aureus infection in two), the D/P ratios of NOx levels remained elevated by 1.5-fold despite treatment, and the catheters were removed. These results suggest that dialysate NOx may be influenced not only by local NO production, but also by plasma NO or NOx diffusion. Therefore, we can suppose that the D/P ratio of NOx levels provides more clinical significance than dialysate NOx levels only. In conclusion, the D/P ratios of NOx levels may serve as a marker to assess the severity of peritoneal inflammation, treatment efficacy, and progression of refractory peritonitis in CAPD patients with peritonitis.