PULMONARY DISTRIBUTION AND EFFICACY OF EXOGENOUS SURFACTANT IN LUNG-LAVAGED RABBITS ARE INFLUENCED BY THE INSTILLATION TECHNIQUE

Surfactant bolus instillation has been reported to cause changes in ar terial blood pressure (BP) and cerebral blood flow velocities which ma y increase the risk of intraventricular haemorrhage. To avoid these ef fects, slow tracheal infusion was evaluated as a possible alternative method of surfactant administration. Saline lung lavages were performe d in 13 anesthetized and artificially ventilated adult rabbits to prod uce respiratory distress syndrome. Curosurf (CS, 200 mg/kg) labeled wi th C-14-dipalmitoyl-phosphatidylcholine (-DPPC) and/or red microsphere s (RMS) was instilled into the trachea either as a single bolus (n = 8 ) or by infusion during 45 min via a side-channel within the wall of t he tracheal tube (n = 5). An arterial cannula was placed for monitorin g of blood gases and BP. To determine surfactant distribution, the lun gs were cut into 60-70 pieces and radioactivity and/or the number of R MS were measured in each piece. The distribution of RMS was closely re lated to the distribution of C-14-DPPC (r = 0.96). Bolus instillation of CS led to a prompt and sustained increase in PaO2 (from <10.5 to >4 0 kPa within 2 min), a transient decrease in BP, and a reasonably homo geneous pulmonary surfactant distribution. Tracheal infusion of CS cha nged neither BP nor PaO2 during the observation period of 60 min. The pulmonary distribution of CS was extremely uneven after infusion. The distribution of exogenous surfactant and its effects on gas exchange a re influenced by the instillation method. An inadequate instillation t echnique may add to the causes of ''poor response'' after surfactant r eplacement.