Hypokalaemia: an independent risk factor of Enterobacteriaceae peritonitis in CAPD patients.

BACKGROUND: Hypokalaemia is a relatively common complication in uraemic patients undergoing continuous ambulatory peritoneal dialysis (CAPD). The hazards of hypokalaemia are multiple and have been correlated with patient morbidity and mortality. Whether it is associated with increased risk of peritonitis remains to be addressed.
METHODS: We retrospectively analysed our CAPD patients who had complicating peritonitis in a 2-year period. The influence of hypokalaemia on the clinical features of peritonitis was assessed. From September 2003 to August 2005, 140 unselected patients undergoing CAPD treatment and followed up in our hospital were recruited for the study. Hypokalaemia was defined as a serum potassium level <3.5 mmol/l. The impact of hypokalaemia on several clinical parameters, including the nutrition status, dialysis adequacy, occurrence of peritonitis and the etiologic pathogens, was analysed.
RESULTS: During the study period, 462 determinations (23.6%) were below quantity <mmol/l. The overall peritonitis rate was 30.6 patient-month per episode (total 64 episodes). The prevalence of peritonitis was significantly higher in patients with hypokalaemia (6.9%) compared to those without hypokalaemia (2.1%, P < 0.001). Hypokalaemia was also associated with lower serum albumin (P < 0.001), serum phosphate (P < 0.001), total serum cholesterol (P = 0.049) and normalized protein nitrogen appearance (P < 0.001). There was no correlation between serum potassium level and daily PD exchange volume, total Kt/V, urine volume or daily ultrafiltration volume. The peritoneal equilibration test was not significantly different between patients with and without hypokalaemia. When the aetiologic organisms of peritonitis were grouped according to their usual site of colonization, Enterobacteriaceae appeared to be much more prevalent than epidermal microorganisms (53.1% versus 18.8%, P = 0.004) in the hypokalaemia group. However, this was not the case in patients with normal serum potassium.
CONCLUSION: CAPD patients with hypokalaemia are associated with a higher prevalence of peritonitis and poor nutritional status. Enterobacteriaceae were the predominant organisms causing peritonitis in the group with hypokalaemia. This unique and novel finding implies the translocation of these organisms from intestinal mucosa into the peritoneal cavity. A pathogenic mechanism linking malnutrition and hypokalaemia is also proposed.