AUTONOMIC DYSFUNCTION IN HEMODIALYSIS-PATIENTS WITH PERSISTENT HYPOTENSION

To investigate autonomic mechanisms underlying persistent hypotension in long-term hemodialysis patients, high-frequency (HF, >0.15 Hz) and low-frequency (LF, 0.04-0.15 Hz) components of heart rate variability and plasma noradrenaline were analyzed in 10 persistently hypotensive hemodialysis patients (group H), 11 normotensive patients (group N) an d 10 healthy controls (group C). The HF amplitude, an index of cardiac parasympathetic activity, and LF-to-HF ratio, an index of sympathetic predominance, were in the order of groups C > N > H (p < 0.01). While the HF amplitude decreased with standing in all three groups (p < 0.0 5 for all), the LF-to-HF ratio increased only in groups N and C (p < 0 .05 for both) but not in group H. Conversely, plasma noradrenaline lev el was in the order of groups C < N < H (p < 0.001). Furthermore, whil e the LF-to-HF ratio correlated positively with the plasma noradrenali ne level in group C (r = 0.73, p < 0.01), it correlated negatively in group H (r = 0.69, p < 0.05). These results indicate that an impairmen t in both parasympathetic and sympathetic functions exists in hemodial ysis patients with persistent hypotension, and that the apparent sympa thetic dysfunction could result from a reduction in cardiovascular res ponsiveness to sympathetic stimulation.