A Cause Of Spurious Hypotension In Newborn

Normative values of intra-arterial blood pressure (ABP) in newborns were obtained using a strain gauge connected to an umbilical artery catheter without interposition of continuous infusion devices. Currently values on which treatment decisions are based, are obtained while systems for continuous infusion of fluids - (intraflow-IF), even though ABP values from these different techniques have not been compared. We evaluated 170 pairs of direct umbilical ABP measurements obtained, with and without IF systems, from 16 infants, BW range 730-4790 gm, during the first week of life. Mean systolic blood pressures were 4 and diastolic 4.2 mmHg lower while using IF systems than without (p<.001). The size of the infant and the infusion capacity through the IF system influence the magnitude of the observed differences. The smaller the infant-with lower blood pressure-and the greater the capacity of the IF system, the lower will be the ABP values obtained. Under these conditions hypotension will be overdiagnosed, leading to overtreatment especially of the very immature infant. In order to avoid iatrogenic disease in these infants, if IF systems are used, ABP values should be obtained with and without IF before therapy for hypotension is initiated.