Time to failure of arterial shunts in a pig hemorrhagic shock model

Temporary vascular shunts (TVSs) are relied on frequently in the current military theater. Details of their physiology and outcome are of increasing interest and needed to further define their place in the management of trauma. This study was conducted using a porcine hemorrhagic shock model and aimed to 1) establish the time to failure of short, proximally placed vascular shunts; and 2) examine histological changes in the shunted artery. The external iliac artery of male pigs was transected and a straight shunt secured in place. Hemorrhagic shock was then induced by rapidly removing 40 per cent of blood volume and maintaining severe hypotension for 40 minutes before resuscitation. Animals were observed for up to 6 days for limb function as well as overall physiological status. At the conclusion of the experiment, status of the shunt and adjacent artery was evaluated by an independent pathologist. The presence of thrombi and inflammation within the proximal and distal artery was graded. Among the 10 animals tested, nine subjects survived the initial surgery. All shunts remained patent with mean time of 4.2±1.2 days of observation. Three-position histological analysis of the connected arterial tissues revealed minimal acute inflammation and minimal or thrombus. The results suggest that TVSs in proximal arteries remain functional for at least 48 to 72 hours in proximal arteries even without anticoagulation in the setting of brief hemorrhagic shock. This knowledge may aid combat evacuation patterns.