Effects of plasmapheresis on short-term variability of blood pressure in healthy donors.

The acute effect of mild central hypovolaemia induced by plasmapheresis on the short-term variability of blood pressure and heart rate was evaluated in ten healthy donors. Indirect finger blood pressure was measured by a non-invasive device (Finapres). Analogue-to-digital conversion of the blood pressure was used to determine systolic, diastolic and mean blood pressure and heart rate every second. The equidistant sampling allowed a direct spectral analysis using a fast Fourier transform algorithm. Blood pressure and heart rate were maintained while an increased overall variability of blood pressure was observed after plasmapheresis. The increased total area under the curve of the systolic and diastolic blood pressure spectra was documented with the selective analysis of the three main components of the spectra: the increase in the oscillations of blood pressure following plasmapheresis predominated in the 66-129 mHz region, corresponding to Mayer waves. The spectral profile of HR was unaffected by plasmapheresis. The significant increase in the 10-s period oscillations of blood pressure after the mild central hypovolaemia could result from the unloading of cardiopulmonary (and arterial) baroreceptors which in turn could buffer the arterial pressure through sympathetic activation, detected on the systolic and diastolic pressure spectra in the low-frequency range.