SIMULTANEOUS INFLUENCE OF BLOOD-PRESSURE, PCO2, AND PO2 ON CEREBRAL BLOOD-FLOW VELOCITY IN PRETERM INFANTS OF LESS-THAN 33 WEEKS GESTATION

In extremely preterm infants, the protective capacity for cerebral blo od flow (CBF) autoregulation may be impaired or absent, which increase s the risk for developing cerebral lesions. The purpose of this study was to quantify the simultaneous influence of several vital parameters , such as mean arterial blood pressure (MABP), PCO2, and PO2, on cereb ral blood flow velocity (CBFv), which is used as a measure for CBF. In 16 mechanically ventilated infants of <33 wk gestation, the CBFv in t he internal carotid artery was measured every minute for 1 h by a comp uter-controlled pulsed Doppler device. MABP and transcutaneous PCO2 an d PO2 were recorded as well. A multiple linear regression analysis was performed in each patient to determine the individual MABP, PCO2, and PO2 reactivities as a measure for CBF autoregulation. The medians (an d ranges) of the whole group were an MABP reactivity of 7.5% (-12.5 to 20.1%) rise in CBFv/1 kPa rise in MABP, a PCO2 reactivity of 32.7% (- 8.1 to 79.5%) rise in CBFv/1 kPa rise in PCO2, and a PO2 reactivity of -3.1% (-14.2 to 7.9%) fall in CBFv/1 kPa rise in PO2. In preterm infa nts, the individual's capacity for MABP-, PCO2-, and PO2-dependent CBF autoregulation can be estimated by means of the present method, even if the vital parameters change simultaneously.