Artificial Surfactant Administration in an Animal Model of Near Drowning

Objective: To study the use of exogenous surfactant in a rabbit freshwater near-drowning model. Methods: In a randomized, placebo-controlled experiment, 21 rabbits were anesthetized, paralyzed, and subjected to near drowning with 6 mL/kg of distilled water. Vital signs, arterial blood gases, and pulmonary compliance were measured at predetermined intervals. The animals were randomized into two groups: a normal O2 group that had their pO2 levels adjusted to 75–150 torr using supplemental O2 as needed, and a high O2 group ventilated with an FiO2 = 100%. Ventilator settings were further adjusted to normalize pH and pCO2 levels prior to instillation of distilled water. The two groups were further divided and 15 minutes after simulated near drowning, the animals were either treated with surfactant (5 mL/kg instilled en-dotracheally) or not treated. Data were analyzed by repeated-measures analysis of variance. Results: Near drowning had no significant effect on heart rate or blood pressure. Acidosis was not changed by surfactant; hypoxia was worsened by surfactant: 158 ± 54 torr before and 66 ± 19 torr after administration (p < 0.01). Compliance did not change as a result of surfactant administration. Only the animals (n = 3) in the normal O2 plus surfactant group died during the 90-minute post-near-drowning period of the study. Conclusions: Surfactant administration (5 mL/kg) in this animal model of freshwater near drowning offers no benefit over simple ventilation. Assessment of the merit of smaller volumes of surfactant should be investigated because administration of this solution may represent a second pulmonary insult, given current volume recommendations.