COMPARISON OF PRECOLLAPSE AND POSTCOLLAPSE EFFETS OF A VENOUS FILTER ON THE EMBOLIC LOAD DURING MEDULLARY CANAL PRESSURIZATION: A CANINE STUDY

Abstract

Purpose: The purpose of this study is to evaluate the hemodynamic and pulmonary effects of intramedullary nailing with a removable filter placed into the common iliac vein.

Methods: Under general anaesthesia, a collapsible filter was inserted into the left common iliac vein in eight dogs and compared to a control group from a previous study. The left femora and tibiae were then pressurized by injection of bone cement and the insertion of intramedullary rods. Echocardiographic images and hemodynamic measurements including arterial blood gas, cardiac output, left atrial, right atrial, pulmonary arterial, and aortic pressure were recorded as baseline measurements and at 1, 5 and 15 minutes after medullary-canal pressurization. After fifteen minutes of pressurization the filter debris was evacuated, the samples sent for analysis and the filter was collapsed and removed. The dog’s hemodynamics were then monitored for a further fifteen minutes. The animals were killed and the lungs were harvested for histomorphometric analysis.

Results: Full hemodynamic and histomorphometric results of the lung tissue and debris collected from the evacuated filters are still pending at the time of this submission however initial findings indicate that the filter prevented an immediate increase in mean pulmonary artery pressure after canal pressurization. No large embolic event was visualized in any of the filtered dogs. In contrast, all animals in the control group demonstrated moderate-to-severe echogenic response with intense showering of echogenic material, including large embolic masses. Removal of the filter was safe and repeatable.

Conclusions: This experiment has shown that proximal venous blockade by means of a removable filter was able to reduce the size and the quantity of the embolic load on the lungs and the filter could be safely collapsed and removed after suctioning of the debris. High rates of embolization causing increased morbidity and mortality after intramedullary stabilization of pathological fractures and of traumatic fractures with concomitant lung injury have been reported. Prophylactic insertion of a removable temporary filter in this high-risk group prior to reamed intramedullary nailing may be beneficial.

Funding : Other Education Grant

Funding Parties : Synthes Canada