NEW YORK (Reuters Health) – Recombinant surfactant protein C based surfactant (rSP-C, Nycomed) provides no benefit in patients with severe direct lung injury, but the information gained may still be of use, researchers report in a December 10th on-line paper in the American Journal of Respiratory and Critical Care Medicine.

As Dr Roger G. Spragg told Reuters Health by email, “The findings of our study do not support a current role for lung surfactant in the treatment of severe lung injury. They do, however, highlight important properties of lung surfactant that may be required for therapeutic benefit in future studies.”

Dr. Spragg of the University of California San Diego and San Diego Veterans Affairs Healthcare System and colleagues observe that there were a number of reasons for examining the approach. Among these were improvement in blood oxygenation.

The synthetic surfactant rSP-C, say the researchers, has excellent surface activity and markedly improves gas exchange in animal models of lung injury and has shown blood oxygenation improvement in unselected ARDS patients.

To investigate whether the approach might reduce mortality in severe lung injury, the team randomized 843 patients to receive usual care and up to 8 doses of rSP-C surfactant administered over 96 hours or to usual care alone.

Mortality at 28 days was 22.7% in the surfactant group and 23.8% in the usual care group. The proportion of patients still alive was also similar at 3 months (64.9% versus 65.6%) and at 6 months (62.5% versus 63.9%).

There was also no significant difference in oxygenation and the study was stopped for futility at a planned interim analysis.

The absence of benefit was surprising, but may have involved surface tension. The researchers had added a shearing step in order to improve dispersion of the surfactant, Examination in an in vivo rat model showed that this move had little adverse effect.

However, the investigators conclude that “Shearing of the surfactant during resuspension may have resulted in impairment of surface tension lowering function and increased susceptibility to inhibition by plasma proteins, hence explaining the apparent lack of clinical efficacy.”

Reference:
Recombinant Surfactant Protein C Based Surfactant for Patients with Severe Direct Lung Injury
Am J Respir Crit Care Med 2010.