Effect of lung water content, manipulated by intratracheal furosemide, surfactant, or a mixture of both, on compliance and viscoelastic tissue forces in lung-lavaged newborn piglets

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Abstract
Objective To study the impact of lung water content and its reduction by a topically applied diuretic on respiratory and lung tissue mechanics in comparison with surfactant administration in surfactant-deficient newborn piglets with lavage-induced lung injury. Design Controlled, randomized study. Setting Animal research facility. Subjects Newborn piglets. Treatment Piglets were surfactant depleted by lung lavage and, after a pretreatment period, randomly treated with intratracheal furosemide, furosemide and surfactant, or with surfactant alone. Measurements and Main Results Dynamic compliance (Cdyn), static compliance (Cst), stress-adaptation pressures (Pdiff) and post mortem lung water content were determined. Static compliance in the furosemide-surfactant group was not significantly higher than in the surfactant group. At the end of the study, Cst did not differ between the three groups because Cst in the furosemide group had increased to values similar to those of the surfactant-containing treatment groups: Cst F+S: 0.73 ± 0.2 mL/cm H2O/kg body weight (BW); Cst S: 0.61 ± 0.11 mL/cm H2O/kg BW; and Cst F: 0.60 ± 0.19 mL/cm H2O/kg BW). Compliance was inversely and Pdiff was directly correlated to lung water (LW) content (Cst vs. LW: r2 = .59, p = .001; Cdyn vs. LW: r2 = .49, p = .006; Pdiff vs. LW: r2 = .37, p = .059), independent of the type of treatment. Changes in Cst and Cdyn were inversely related to changes in Pdiff. Intrapulmonary furosemide was more rapidly absorbed when administered to the surfactant-depleted lung alone compared with the mixture with surfactant, and intrapulmonary furosemide had a rapid systemic effect. Conclusion Although the combination of surfactant with a diuretic failed to increase respiratory compliance to a significantly larger extent than surfactant alone, furosemide at the end of the study increased respiratory compliance to a level similar to surfactant-containing treatments. Lung water content and, to a lesser extent, the absence or presence of surfactant appeared to determine lung mechanics, and its impact on lung mechanics was similar to surfactant administration.