Low dialysate potassium and central arterial pressure waveform

BACKGROUND Cardiovascular mortality is high in hemodialysis (HD) patients. Early arterial pressure wave reflections predict mortality in HD patients, and HD acutely improves the central pressure waveform. Potassium (K) plays a crucial role in cardiac electrophysiology, and patients with end-stage kidney disease depend on HD for neutral K balance. We aimed to study the impact of dialysate K concentrations on central arterial pressure waveform. METHODS Thirty-three chronic HD patients were studied before and after a HD session, and the prescribed dialysate K concentration was recorded. In a subset of 23 patients without arrhythmias, pulse wave analysis was performed on radial arteries. Nine patients had dialysate K set to 1 mmol/L (group 1), and 14 patients had K set to 2 or 3 mmol/L (group 2). Augmentation index (AIx), defined as difference between the second and first systolic peak divided by central pulse pressure, was used as a measure of arterial stiffness. RESULTS HD reduced the AIx in group 1 only (p = 0.0005). Likewise, central systolic pressure was reduced in group 1 only (p = 0.006). The relative reduction of AIx post-HD was significantly higher in group 1 compared with group 2 (p < 0.0001). The association between low dialysate K and AIx reduction remained statistically significant after adjustment for variables including the change in central and peripheral systolic pressure and mean arterial pressure. CONCLUSION Low dialysate K is strongly and independently associated with the acute improvement of AIx.