1006 RELIABILITY OF SKIN (tc)PO₂ ELECTRODE HEATING POWER AS A CONTINUOUS NON INVASIVE MONITOR OF MEAN ARTERIAL PRESSURE IN SICK NEWBORNS

Abstract

In 10 sick newborns (850-4140 gm) we continuously monitored, for 2-7 hrs, central mean aortic blood pressure ≥ and the incremental power (ΔHP) used to heat the Huch PO₂ electrode to 44°, having offset the HP recording to zero during leg cuff occlusion. We term ΔHP/≥ the power pressure ratio (PPR), assuming that 44° gives full vasodilation and that flow under the electrode is proportional to pressure. The tc electrode was insulated from ambient with 2 cm of ensolite. In the 10 babies (34<≥<66), mean PPR was 0.32mw/torr ±11% coefficient of variation (CV=100sd/mean) while mean individual CV=4.1±1.9%. The variation among babies appears due to differences in skin thickness and temperature. ΔHP correlated well with ≥ during changes induced by crying, straining (fig.l), apnea, transfusion and curare administration, but correlated inversely during tolazoline infusion when asphyxial episodes increased ≥ but decreased ΔHP. We conclude that ΔHP is a useful and reliable index of in most sick infants although PPR appears to be affected by skin thickness, body temperature and by infusion of tolazoline.

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