Spectral analysis of heart rate variability during hemodialysis in stable and unstable patients

Spectral analysis of heart rate variability was used to study the different reactions to hypovolemia in patients under chronic hemodialytic treatment. Autoregressive power spectra of the R-R signal were calculated in twenty uremic patients during the hemodialytic sessions. Patients were earlier classified as hemodynamically stable or unstable on the basis of their historical propensity to hypotension. Stable patients shown a large power component in the LF band, and a ratio between the powers in LF and HF band greater than one. On the contrary, all the unstable patients, were characterised by a value of the LF/HF ratio less than one. Therefore, the hemodynamic instability of the hypotension-prone patients, may be due to a deficiency in the short-term regulatory response. Relaxation of the compensatory response to the hypovolemia induced by the hemodialysis may be caused by an impairment of the baroreceptor reflex