Acute effect of a peritoneal dialysis exchange on electrolyte concentration and QT interval in uraemic patients.

Background: Hemodialysis (HD) sessions induce changes in plasma electrolytes that lead to modifications of QT interval, virtually associated with dangerous arrhythmias. It is not known whether such a phenomenon occurs even during peritoneal dialysis (PD). The aim of the study is to analyze the relationship between dialysate and plasma electrolyte modifications and QT interval during a PD exchange.
Methods: In 15 patients, two manual PD 4-h exchanges were performed, using two isotonic solutions with different calcium concentration (Ca ⁺⁺ 1.25 and Ca1.75 ⁺⁺  mmol/L). Dialysate and plasma electrolyte concentration and QT interval (ECG Holter recording) were monitored hourly. A computational model simulating the ventricular action potential during the exchange was also performed.
Results: Dialysis exchange induced a significant plasma alkalizing effect (p < 0.001). Plasma K ⁺ significantly decreased at the third hour (p < 0.05). Plasma Na ⁺ significantly decreased (p < 0.001), while plasma Ca ⁺⁺ slightly increased only when using the Ca 1.75 ⁺⁺  mmol/L solution (p < 0.01). The PD exchange did not induce modifications of clinical relevance in the QT interval, while a significant decrease in heart rate (p < 0.001) was observed. The changes in plasma K ⁺ values were significantly inversely correlated to QT interval modifications (p < 0.001), indicating that even small decreases of K ⁺ were consistently paralleled by small QT prolongations. These results were perfectly confirmed by the computational model.
Conclusions: The PD exchange guarantees a greater cardiac electrical stability compared to the HD session and should be preferred in patients with a higher arrhythmic risk. Moreover, our study shows that ventricular repolarization is extremely sensitive to plasma K ⁺ changes, also in normal range.