206 TRACHEAL SURFACTANT INFUSION DURING 5 MIN IS LESS EFFECTIVE THAN BOLUS INSTILLATION IN RABBITS

Abstract

Surfactant bolus instillation has been reported to cause transient blood pressure (BP) changes in preterm infants. However, other methods of instillation such as slow tracheal infusion are less effective in improving oxygenation (Pediatr Res 34:490, 1993). Rapid tracheal infusion was evaluated as alternative method of surfactant instillation.

Respiratory distress was induced in 10 adult rabbits by repeated saline lung lavages until PaO₂ was <80 mmHg during mechanical ventilation with FiO₂ = 1.0. Curosurf (CS, 200mg/kg) labelled with colored microspheres was instilled either as bolus (n = 5) or as rapid infusion during 5 min (n=5). Blood gases and BP were monitored for 2 h. After sacrifice, the lungs of each animal were cut into 60-70 pieces to measure the number of microspheres in each piece.

After CS bolus, PaO₂ increased to 355 ± 28 mmHg (m±SEM) within 2 min and remained above this value for 2 h. Mean BP dropped transiently from 93 ± 2.8 to 71 ± 9.9 mmHg. Pulmonary CS distribution was fairly homogeneous. After rapid infusion, PaO₂ rose to 223 ± 55.3 mmHg within 15 min but decreased again thereafter (ANOVA comparing both groups: p <0.05). BP dropped transiently from 94 ± 5.9 to 81 ± 6.0 mmHg. CS distribution was very uneven.

With rapid tracheal infusion instead of bolus instillation, pulmonary distribution of exogenous surfactant is uneven, and oxygenation is less effectively improved. BP changes cannot be avoided.

Supported by Deutsche Forschungsgemeinschaft, DFG Ob 43/6-1

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