Abstract 1178 Poster Session IV, Tuesday, 5/4 (poster 267)

Background: Pulsed-wave CDD sonography allows accurate measurements of cerebral blood flow velocity (CBFV) but because of the high energy output individual studies are limited in time. A modified TCD technique for use in newborns permits long-term measurements of CBFV (low energy output, Ispta < 5 mW/cm2). However, the placement of the sample volume is blind and the insonation angle cannot be corrected. We compared the results of these two Doppler techniques.

Methods: We studied 11 healthy neonates (GA 40±1 wks and BW 3612±518 g) on day 2 of life. CBFV was measured in the middle cerebral artery by the trans-temporal approach. Each infant was consecutively examined by 3 investigators with both Doppler techniques on two occasions within a 2-hr period (examinations began approx. 30 min after the infants were breast fed at about 7 pm). Each investigator measured CBFV first with TCD (DWL Multi-Dop X, buttonshaped 2.0 MHz probes, Ispta = 3.5 mW/cm2) and then with CDD (Acuson 128XP, 2.0 MHz linear transducer) creating measurement pairs (TCD:CDD). Six measurement pairs per infant were recorded. To detect artifacts during later data analysis heart rate and thoracic impedance were recorded (HP68S-monitor) and all studies were videotaped. For each Doppler recording the median of a 1-min artifact-free period was used for statistical analysis. The CBFV data were analyzed for peak-systolic (Vmax), mean (Vmean), and end-diastolic (Vmin) blood flow velocity, and resistance index {RI=(Vmax - Vmin)/Vmax}. The Doppler techniques were compared using the Bland-Altman method. The investigator effect was tested by multifactorial analysis of variance (SAS).

Results: The mean differences between the techniques (TCD - CDD; Table) were not investigator dependent.

Table 1 No caption
Full size table

Conclusions: TCD yielded lower values of V min and higher values of RI than CDD. The two techniques were in good agreement for Vmax and Vmean measurements with respect to the mean values. However, the high SD indicates the high variability for Vmax and Vmean recordings, which may have therefore not shown statistical significance because of the small number of recordings. We hypothesize that compared to CDD, TCD may underestimate CBFV because of either less exact placement of the sample volume or differences in the shape of the transmitted ultrasound beams.

Funded by the Austrian Research Foundation, Vienna (FWF-Project Nr. 9342-Med)