Rapid Tracheal Infusion of Surfactant versus Bolus Instillation in Rabbits: Effects on Oxygenation, Blood Pressure and Surfactant Distribution

Abstract

Surfactant bolus instillation may be associated with a drop in blood pressure. Platelet-activating factor (PAF) has been found in surfactant preparations. The aim of this study was to evaluate rapid tracheal infusion of surfactant during 5 min as an alternative to bolus instillation and to examine whether a PAF receptor antagonist is able to prevent the decrease in blood pressure. Methods: Surfactant deficiency was induced in 16 adult rabbits by lung lavages with saline. Six animals received a bolus of a porcine surfactant preparation (Curosurf® (CS); 200 mg/kg), labeled with red microspheres to assess pulmonary distribution. In another 5 rabbits, the same amount of labelled CS was instilled by tracheal infusion within 5 min. A third group of 5 animals received 3 mg/kg body weight of the PAF antagonist WEB 2170 before CS bolus instillation. Results: After CS bolus administration, mean PaO₂ increased by 44.7 ± 8.3 kPa (mean ± SD) within 2 min and remained at this level. Mean arterial blood pressure dropped transiently by 2.3 ± 2 kPa within 5 min. Pulmonary distribution of surfactant was even. After infusion, mean PaC₂ rose by 22.4 ± 16.3 kPa within 15 min. Blood pressure dropped by 1.8 ± 1.1 kPa within 15 min. The distribution was extremely uneven. Blood pressure decreases also occurred after pretreatment with PAF receptor antagonist. Conclusion: Rapid tracheal infusion of surfactant results in poorer oxygenation, an inhomogeneous distribution and a similar decrease in blood pressure compared to the bolus instillation method. Blood pressure changes could not be prevented by a PAF receptor-specific antagonist.