13 CEREBRAL CIRCULATION IN THE NEONATE: ASSESSMENT USING TRANSCEPHALIC IMPEDANCE AND DOPPLER ULTRASOUND

Abstract

It has been suggested that fluctuations in arterial blood pressure and cerebral arterial flow velocity (CAFV) alter brain perfusion and lead to intraventricular haemorrhage (Perlman et al, New Eng J Med 309: 209, 1983). Although intermittent measurements of CAFU can be obtained by Doppler ultrasound, a major problem is the inability to monitor cerebral circulation continuously.Experimental design: A microprocessor based technique of transcephalic electrical impedance (dZc) was used to monitor the cerebral circulation continuously (Murphy et al, in “Electronics in Medicine and Biology”, IERE, London 1986). Average dZc, arterial blood pressure and heart rate were continuously displayed and stored. Measurements of avg dZc amplitude were compared with intermittent values of CAFV (Angioscan III) obtained from the anterior cerebral artery. Neonates with birth weight <1500g were studied for the first 48 hours. Those who received either indomethacin or aminophylline were studied before and for one hour after the dose.Results and comments: In the 48-hour studies (n=3) the r values for the intra-individual correlation between avg dZc and mean CAFV were 0.40, 0.70 and 0.74 (all p<0.05). In the 1-hour studies (n=5) indomethacin caused a decrease of 25-30% in both signals. CAFV is an estimate of blood flow in the anterior cerebral artery whereas dZc reflects global changes in instantaneous intracerebral pulsatile blood volume. Our preliminary results suggest a relationship between these signals.Financial support: The Medical Foundation - University of Sydney; the English Speaking Union and Nestle (PBC): The British Council, Turku University Foundation, and Academy of Finland (JATV).