Objective: To assess the possible effects of peritonitis on peritoneal and systemic acid-base status. Design: pH, pCO2, lactate, and total leukocyte and differential count were simultaneously determined in the overnight dwell peritoneal dialysis effluent (PDE) and arterial blood in noninfected patients (controls) and on days 1, 3, and 5 from the onset of peritonitis. Setting: University multidisciplinary dialysis program. Patients: Prospective analysis of 63 peritonitis episodes occurring in 30 adult CAPD patients in a single center. Results: In controls, mean (+/-SD) acid-base parameters were pH 7.41+/-0.05, pCO2 43.5+/-2.6 mm Hg, lactate 2.5+/-1.5 mmol/L in the PDE, and pH 7.43+/-0.04, PaCO2 36.8+/-3.8 mm Hg, lactate 1.4+/-0.7 mmol/L in the blood. In sterile (n=6), gram-positive (n=34), and Staphylococcus aureus (n=9) peritonitis PDE pH's on day 1 were, respectively, 7.29+/-0.07, 7.32+/-0.07, and 7.30+/-0.08 (p<0.05 vs control). In gram-negative peritonitis (n=14) PDE pH was 7.21+/-0.08 (p<0.05 vs all other groups). A two-to-threefold increase in PDE lactate was observed in all peritonitis groups, but a rise in pCO2 was only seen in gram-negative peritonitis. Acid-base profile of PDE had returned to control values by day 3 in sterile, gram-positive and Staphylococcus aureus peritonitis and by day 5 in gram-negative peritonitis. Despite a slight increase in plasma lactate on the first day of peritonitis, arterial blood pH was not affected by peritonitis. Conclusion: PDE pH is decreased in continuous ambulatory peritoneal dialysis (CAPD) peritonitis, even in the absence of bacterial growth. In gram-negative peritonitis, PDE acidosis is more pronounced and prolonged, and pCO2 is markedly increased. Arterial blood pH is not affected by peritonitis.
