Use of a chronic prefemoral lymphatic fistula for monitoring systemic capillary integrity in unanesthetized sheep

Abstract

Alterations in fluid and protein flux across the soft tissue capillary resulting in edema formation is a common occurrence in the critically ill patient. The pathophysiology and therapeutic modalities for treating edema are poorly defined in large part due to the difficulty of monitoring capillary integrity. We have described a preparation using lymph flow (Q̇ L) from the prefemoral efferent lymphatic in sheep, which we have found to accurately reflect changes in capillary fluid and protein flux. The lymph fistula is easy to prepare and chronic studies can be performed in the unanesthetized state. A lung lymph fistula can be formed in the same animal which allows for the comparison of the pulmonary and systemic capillary effects of injury. We have found that prefemoral Q̇ L responds in a predictible manner to changes in Starling forces reflecting in changes in fluid flux. We also determined that the soft tissue capillary responds differently to different systemic insults, increasing both fluid and protein flux with a contralateral burn injury and demonstrating no effect from endotoxemia. Prefemoral and lung lymph flow also responded differently to the same insult indicating the importance of studying both capillary systems simultaneously. These findings reflect the need to monitor the systemic capillary. We consider this lymph preparation to be very useful for this purpose.