Revista Brasileira de Ginecologia e Obstetrícia (Jun 2004)
Dopplerfluxometria de ducto venoso: identificação não invasiva da acidemia em fetos prematuros centralizados Ductus venosus velocimetry: noninvasive identification of fetal acidemia in preterm fetuses with brain sparing reflex
Abstract
OBJETIVO: estabelecer o ponto de corte a partir do qual seja possível identificar fetos prematuros com centralização do fluxo sangüíneo que apresentem gasometria anormal. MÉTODO: foi realizado estudo observacional transversal, cuja população consistia de 60 gestantes com fetos centralizados (relação umbílico-cerebral maior que 1), com idade gestacional entre 25 e 33 semanas. O ducto venoso foi identificado com auxílio da dopplerfluxometria colorida e obtida a relação S/A a partir do sonograma (relação entre a velocidade de pico da sístole ventricular e a velocidade de pico da sístole atrial). Imediatamente após a cesariana foi colhida amostra de sangue da veia umbilical para gasometria. Os conceptos foram classificados de acordo com a análise gasométrica e considerados anormais quando pH OBJECTIVE: to assess through Dopllerfluxometry the S/A ratio of the ductus venosus and determine the cut-off point to identify preterm fetuses with the 'brain sparing phenomenon". METHOD: a cross-sectional study was performed in 60 pregnant women that presented the "brain sparing phenomenon" (umbilical cerebral ratio >1) and gestational age between 25 and 33 weeks. The following parameters were studied: S/A ratio of the ductus venosus, pH and base excess (BE) of a fetal blood sample collected from the umbilical vein immediately after birth. The fetuses were classified according to the gas analysis result. They were considered abnormal when pH <7.20 and BE < -6 mmol/l. A receiver operator characteristic (ROC) curve analysis was performed to examine the relationship between S/A ratio and fetal acidemia. RESULTS: sixty pregnant women in the period of January 1998 to January 2003 were selected. In the moment of the study the gestational age varied from 25 to 33 weeks, with an average of 29.7 weeks (±1.8 weeks). All of the fetuses presented the "brain sparing phenomenon". Among them 14 presented abnormal gas analysis at birth and 46 presented normal gas analysis. The prevalence of fetuses with abnormal gas analysis in the studied material was 23.33%. Significant association was observed between the abnormal ductus venosus velocimetry and abnormal gas analysis at birth (chi2 = 784.44, p < 0.00001) in preterm fetuses with "brain sparing phenomenon". The best cut-off point of the S/A ratio (where the ROC curves bent) was 3.4. CONCLUSION: fetal acidemia in preterm fetuses with "brain sparing phenomenon" may be noninvasively identified by Doppler measurement of the ductus venosus when the S/A rises above 3.4.
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