Transfer function analysis of dynamic cerebral autoregulation in preeclampsia

Abstract

Objective The cerebral circulatory effects of preeclampsia on the latency (phase) and the efficiency (gain) of the cerebral autoregulatory response is unknown. Preeclampsia causes a progressive impairment of the cerebral autoregulatory response. We sought to identify these dynamic cerebral autoregulation changes in preeclampsia. Study design We simultaneously measured continuously beat to beat outputs of mean arterial pressure (MAP) (Pilot 9200) and beat to beat, systolic, diastolic, and mean cerebral blood flow (MCBFV) (Nicolet Vascular TCD) for 2 min with the patient during supine rest. Five preeclamptic and 5 matched normotensive controls were studied. R-R intervals, MAP, and MCBFV were analyzed in the frequency domain. Data sets were fast Fourier transformed and power spectral densities were calculated. We calculated the phase angle (which represents the temporal relationship between the MAP and mean MCBFV) and the transfer function (amplitude or gain between changes in the MCBFV signal and the MAP signal). All continuous data was compared between the two groups using T tests. Results We identified a significant difference between (1) the gain between the normotensive and preeclamptic groups (.29 ±.07 vs.10 ±.04) (p