Blood-pressure-induced oscillations of cerebral hemodynamics during hemodialysis

In a study on one patient during hemodialysis, we used near-infrared spectroscopy (NIRS) to measure coherent oscillations of cerebral concentrations of oxyhemoglobin ([HbO2]), deoxyhemoglobin ([Hb]), and total-hemoglobin ([HbT]) induced by systemic oscillations in mean arterial pressure (MAP) at a frequency of 0.07 Hz. During hemodialysis, we observed that the phase of [Hb] versus [HbO2] becomes less negative, whereas the phase of [HbT] versus MAP becomes more negative. By applying a quantitative hemodynamic model, we assign these phase changes to an increase in venous blood transit time and a less effective cerebral autoregulation during the hemodialysis process.