Electrocardiography and serum potassium before and after hemodialysis sessions

This study was undertaken to assess potassium level and electrocardiographic (ECG) changes post hemodialysis and whether fall in potassium level during dialysis may potentiate cardiac arrythemia. We studied 21 chronic hemodialysis (HD) patients who had their serum electrolytes measured before and immediately after dialysis session, and ECG performed at the same time. The patients included 14 females and 7 males with a mean age of 53.1+/-15.6 years and range from 26 to 81 years; 9 (43%) patients were diabetics. All the patients had been on dialysis for a minimum of 6 months each Pre-HD serum potassium levels had no correlation with any ECG parameters except a negative correlation with the T wave amplitude r=-0.5, p=0.021. ECG parameters significantly changed post-HD; the T wave amplitude decreased, and the R wave amplitude increased. A comparatively higher R wave significantly decreased the T to R wave ratio post dialysis. The QRS duration and QTc interval also increased significantly. The patients with post-HD serum potassium of < or = 3.5 -in comparison to those with levels > 3.5 mmol/L -had a higher R wave amplitude and a significantly less T to R wave ratio (11.8+/-9.7 vs 6.4+/-5.1, p=0.045 and 0.4+/-0.38 vs 1.0+/-0.97, p=0.049, respectively. In patients with serum potassium decrement of > 2.0 mmol/L, the T to R wave ratio decreased significantly, 0.32+/-0.21 vs 0.85 +/-0.26, p=0.023; The T wave amplitude decreased more than the rise in R wave. Multiple regression analysis did not reveal any relationship of pre or post HD ECG changes and serum potassium, serum calcium or net change in serum potassium post-HD. We conclude that post-HD serum potassium decrement results in a decrease in T to R wave ratio on ECG; this change may have an arrhythmogenic potential.