Influences of the Intrapulmonary R-->L Shunt on PaO2 and PaCO2 after Instillation of Exogenous Pulmonary Surfactant to Premature Neonates with Respiratory Distress Syndrome

Park, Yoon Hyung; Chung, Sei Woo; Han, Seung Baik; Kwon, Young Se; Kim, Ji Youn; Cheong, Woo Sik; Lim, Dae Hyun; Son, Byong Kwan

Abstract

PURPOSE
We are inclined to analyze the relationship between the intrapulmonary right-to-left shunt and the PaO2/PaCO2 after endotracheal single-dose surfactant instillation to premature neonates with respiratory distress syndrome within 6 hours after birth.
METHODS
From Jan. 1993 to Jun. 1995, we have conducted a clinical trial of surfactant replacement therapy to the premature neonates with respiratory distress syndrome at the neonatal intensive care unit of InHa University Hospital. The surfactant group (n=17) was given Surfactant-TA and mechanical ventilator care, but the control group (n=22) was treated with only mechanical ventilator. We analyzed umbilical arterial blood gases and estimated respiratoy indexes before and after treatment.
RESULTS
1) The QSP/QT decreased initially in the surfactant group, but significantly increased 24 hours after treatment in the control group (40.6+/-4.7%, P<0.05). 2) The PaO2 significantly decreased 2 hours and 24 hours after treatment in the control group (60.8+/-10.1mmHg, 63.5+/-7.6mmHg, P<0.05 respectively). There were significant correlations between the QSP/QT and the PaO2 in both groups, and specifically in the conrol group 24 hours after treatment (r=-0.94, P<0.001). 3) The PaCO2 significantly increased 1 hour after treatment, but significantly decreased specifically in the control group 24 hours after treatment (32.5+/-1.8mmHg, P<0.01). However, there were no signifacnt correlations between the QSP/QT and the PaCO2 in both groups.
CONCLUSIONS
Specifically in the control group 24 hours after treatment, with hypocapnia, significant increase in pulmonary blood flow to capillary shunt and low VA/Q units (VA/Q<0.1) at high FIO2 (>0.5) resulted in a decrease in PaO2 and also a significant relationship was found between the QSP/QT and the PaO2. However, there was no significant relationship between the QSP/QT and the PaCO2.