[The role of calcium ions and temperature on the effect of exogenous semisynthetic surfactants (experimental study)]

With the final aim of preventing neonatal respiratory distress syndrome (RDS), the present study was carried out on premature rabbits (28 days of gestation) that showed a moderate level of RDS. These animals were treated intratracheally with 25 microliters of semisynthetic surfactant, composed of natural adult rabbit surfactant/DPC/DPPG (1/0.6/0.6 mol P) in two types of carriers, saline solution (Sf) and a calcium solution (5 mM of Cl2Ca), which were also used as controls. This was maintained throughout the experimental period at 37 degrees C or 60 degrees C, while checking the effect of temperature on their behavior. The final results in the P/V curves showed a significant increase in the maximum distention in the cases treated with semisynthetic surfactant at 60 degrees C with calcium vehicle (60.96 ml/kg) and with saline solution as the vehicle (58.51 ml/kg) with respect to the control without treatment (44.08 ml/kg) (p < 0.05). In the morphometric quantification of the lungs fixed to 10 cm H2O, the highest distention (VV) is reached by the semisynthetic surfactant in calcium solution (Mez.Ca) at 37 degrees C (56.30%) and 60 degrees C (56.31%), followed by the semisynthetic surfactant in saline solution at 37 degrees C (55.17%). The maximum compliance expressed the highest distention (with or without emphysema) and the morphometric distention together with the compliance at 10 cm H2O showed the residual trapping and/or anticollapsing effect. The temperature and the type of vehicle used for the semisynthetic mixture did not significantly influence the lung distention.(ABSTRACT TRUNCATED AT 250 WORDS)