Antepartum middle mean cerebral blood flow velocity correlation with maternal hemodynamics

To determine the correlation between simultaneous assessment of maternal middle cerebral blood flow velocity with the other maternal hemodynamic factors of cardiac output and mean arterial pressure.

Eight normotensive patients were assessed. Maternal cerebral blood flow velocity was assessed using transcranial Doppler. Cardiac output was assessed noninvasively using the thoracic electrical bioimpedance technique over four cycles. Transcranial assessment of cerebral blood flow velocity was done over four cycles. Statistical analysis was then done using the Pearson correlation coefficient and linear regression analysis with stepwise regression. A p-value of < 0.05 was considered significant.

The value of the hemodynamic parameters were cardiac output 8.6 +/- 2.6 L/min, mean arterial pressure 82 +/- 9.7 mm Hg, and mean maternal cerebral blood flow velocity 59.6 +/- 11 cm/s. The pulsatility index was 0.85 +/- 0.15. The mean blood pressure could only explain 42% of the variation in systolic maternal cerebral blood flow velocity and 32% of the variation in mean maternal cerebral blood flow velocity. The mean middle cerebral blood flow velocity did not correlate with cardiac output.

Middle cerebral artery velocity correlates moderately with mean arterial pressure but not with cardiac output. The control of mean arterial pressure cannot be used as the only indicator of appropriate reduction in cerebral blood flow velocity.