Evaluation of a noninvasive transcranial doppler and blood pressure-based method for the assessment of cerebral perfusion pressure in pregnant women

Objective: We have developed a Doppler method for the estimation of cerebral perfusion pressure (CPP) using noninvasive techniques. Our objective was to evaluate our new method in pregnant women. Methods and Materials: Laboring women with a lumbar epidural in situ had transcranial Doppler interrogation of the maternal middle cerebral artery (MCA) to measure systolic, diastolic, and mean velocities. A pressure transducer was connected to the epidural catheter and pressure was recorded. Systolic (SBP), diastolic (DBP), and mean (MAP) blood pressure were taken with a Dinamap monitor. Doppler estimated CPP (mm Hg) = [V(mean)/(V(mean)-V(diastolic)](MAP - DBP) and directly measured CPP = MAP - Epidural pressure data were plotted on a Bland-Altman graph with limits of agreement. The mean difference (the mean of the sum of both positive and negative differences) and absolute difference (the mean of the sum of the absolute differences) were calculated. In addition, linear and polynomial regression analyses were performed. Results: Twenty laboring women were studied. All had normal pregnancies. The mean maternal age was 28 ± 7 years and the mean gestational age was 39 ± 2 weeks. The mean maternal MAP was 77 ± 12 mm Hg. The Bland-Airman plot showed a mean difference of 2.2 mm Hg at a mean CPP of 65 ± 12 mm Hg; with a standard deviation of 4.8 mm Hg, the absolute difference was 3.9 ± 3.0 mm Hg at a mean CPP of 65 ± 12 mm Hg. The regression analysis showed an r = 0.92, r² = 0.86, and p < 0.0001. Conclusions: Our formula allows the estimation of CPP using a simple calculation and noninvasively acquired data. This method may be of use for frequent, easy, and accurate CPP and intracranial pressure estimation and may, as such, have significant research and clinical applications.