Blood pressure and sympathetic nerve tone relation during hemodialysis may reflect cardiovascular dysfunction

The blood pressure response to the rapid removal of fluid during hemodialysis is complex and the pathophysiological mechanisms underlying intradialytic hypotension are not clear and sometimes these mechanisms render dialysis difficult to continue.

We analyzed the changes in blood pressure and sympathetic nerve tone and attempted to clarify whether the dynamic pattern of this relationship reflects cardiovascular dysfunction.

The dynamic pattern of sympathetic nerve activity throughout dialysis was analyzed by frequency analysis of RR intervals recorded by 24 hours Holter electrocardiography in 64 patients and 3 minutes ECG every 15 minutes during dialysis in 121 stable end-stage renal failure patients who underwent maintenance hemodialysis. Blood pressure and fluid volume removed was measured every 15-30 minutes during dialysis and the average value of the ratio of low to high frequency components (LF/HF) was calculated as an index of sympathetic nerve tone. The relationship between removed fluid volume, systolic blood pressure (Bp) and LF/HF was analyzed.

The patients were classified into 3 groups based on the correlation between the LF/HF and Bp as follows: positive (52 cases), inverse (54 cases), and not significant (NS; 61 cases). Eighteen patients who showed multiple arrhythmias, atrial fibrillation and other artifacts or noises were eliminated as they were inadequate for frequency analysis of RR intervals. The positive group was characterized by a hypotension-resistant response with a low LF/HF, whereas the inverse group was characterized by a hypotension-prone response with high LF/HF. These results suggest that cardiovascular dysfunction is responsible for the inverse correlation.

Analysis of the relationship between sympathetic nerve tone and Bp is effective in predicting the existing of cardiovascular dysfunction.