Intramedullary femoral nailing in sheep: does severe injury predispose to pulmonary dysfunction?

Abstract

Objective: To find out if intramedullary nailing affects lung function and microvascular permeability whether or not the lung is already injured; if so whether a different method of fixation would diminish the effect; and are the pathogenetic changes related to mechanisms known to precipitate adult respiratory distress syndrome?

Design: Experimental study.

Setting: University hospital, Germany.

Material: 29 Adult female merino sheep.

Interventions: Chronic lung lymph fistulas were created. Two of the three groups (1 and 3) underwent right sided lung contusion and haemorrhage to a mean blood pressure of 50 mm Hg for 2 hours. On day 3 groups 1 and 2 underwent intramedullary nailing, and group 3 had external fixators applied.

Main outcome measures: Pulmonary arterial pressure, concentrations of triglycerides, chemiluminescence of isolated polymorphonuclear leucocytes (PMN), lymph flow, microvascular pressure, filtration coefficient, and permeability.

Results: Intramedullary nailing caused a transient significant increase in pulmonary arterial pressure and triglycerides in groups 1 and 2. Chemiluminescence of isolated PMN decreased in group 1 and increased in group 2. Lymph flow increased 2.5 times in group 1 while microvascular pressure decreased; in group 2 the increase was less but microvascular pressure increased. Filtration coefficient in group 1 was five times that of group 2 and there was a twofold increase in permeability. There were no changes in group 3.

Conclusion: Intramedullary nailing causes additional damage to lungs after lung damage and haemorrhagic shock in sheep. This can be avoided if (in the presence of additional injuries) alternative methods are used.