RESUMEN
We investigated the effects on cerebral hemodynamics of blood pressure changes during exchange transfusions in infants born at or near term, using near infrared spectroscopy in eight stable infants (mean gestational age, 36.2 +/- 1.3 weeks) who underwent a total of 21 exchange transfusions for erythroblastosis fetalis (rhesus hemolytic disease). Changes in mean arterial blood pressure derived from an indwelling umbilical arterial catheter, transcutaneous arterial oxygen and carbon dioxide tension, as well as changes in cerebral oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (HbR), and total hemoglobin (Hbtot = HbO2 + HbR), were recorded continuously from 15 minutes before until the completion of the exchange transfusion. Relative change(s) in cerebral blood volume (dCBV) were calculated as follows: dCBV = change in Hbtot x 0.89/Venous hemoglobin. Changes in mean arterial blood pressure and dCBV were observed during all exchange transfusions; a decrease was found during the withdrawal period and an increase during the infusion period. The mean response of dCBV to a change in mean arterial blood pressure was 0.011 ml.100 gm-1.mm Hg. Multivariate analysis showed that dCBV were primarily associated with changes in mean arterial blood pressure, followed by changes in arterial oxygen tension and in exchange cycle duration. We conclude that in stable term and near-term infants, hemorrhagically induced blood pressure changes provoke dCBV.
Asunto(s)
Volumen Sanguíneo/fisiología , Encéfalo/irrigación sanguínea , Recambio Total de Sangre , Presión Sanguínea , Circulación Cerebrovascular , Eritroblastosis Fetal/fisiopatología , Eritroblastosis Fetal/terapia , Humanos , Recién Nacido , Oxígeno/sangre , Espectrofotometría InfrarrojaRESUMEN
To define the course of neonatal circulatory transition and to identify clinically relevant echocardiographic measurements in the diagnosis of persistent pulmonary hypertension, we prospectively studied 32 healthy term infants from 30 minutes to 24 hours after birth with color and quantitative Doppler echocardiography on the first day of life, and compared them with 33 term infants supported by mechanical ventilation for respiratory failure. Color Doppler imaging included measurements of cardiac output, left pulmonary artery flow, aortopulmonary pressure difference, ductal flow, left-to-right color-flow jet area of the ductus arteriosus, and ductal flow characteristics. In healthy infants the majority of measurable changes in cardiopulmonary hemodynamics had occurred by 8 hours after birth, although some degree of right-to-left ductal shunting was found up to 12 hours after birth. In the infants with respiratory failure, ductal flow and maximum aortopulmonary pressure difference measurements at 8, 12, and 24 hours showed a significant delay in ductal closure and a high incidence of persistent pulmonary hypertension, which correlated well with the severity of their respiratory failure. Factors such as aortopulmonary pressure difference, prolonged right-to-left shunting with decreased left pulmonary artery flow, and failure to develop a left-to-right ductal color-flow jet were found to be practical markers for assessing the course of neonatal circulatory transition in sick term infants.