In Vivo and Ex Vivo Models to Study Ischemia/Reperfusion Injury, Endothelial Cell Protection, and Limb Preservation in a Prolonged Field Care Scenario
Abstract
This proposal addresses the development of in vivo and ex vivo models to assess strategies for the prevention of ischemia reperfusion injury in a prolonged field care (PFC) scenario. Today, amputated limbs need to be replanted by a surgeon within about 6 hours after the amputation occurred. The same is true for severe limb injuries in which the blood supply to the injured extremity needs to be interrupted by use of a tourniquet to prevent fatal blood loss of the patient. Also, here the injured limb or part of a limb needs to be reconnected to the blood circulation (revascularized) at least 6 hours after the injury. In a PFC scenario, this is often not possible. Replantation or revascularization after more than 6 hours of interruption of blood supply (ischemia) will lead to a severe inflammatory reaction, called ischemia/reperfusion (I/R) injury. I/R injury induces dramatic swelling of the affected tissue, which will lead to interruption of the blood circulation and partial or total loss of the limb. In addition, I/R injury can have systemic consequences and may cause the death of the affected patient. In this project, an animal model using pigs will be developed in which novel strategies can be tested to extend the time from injury to replantation. We propose to protect the amputated extremity within 2 hours after the injury is incurred by rinsing it with a solution containing a drug that reduces the severity of I/R injury later on. This can be done by combat medics under battlefield conditions at the so-called RUCK or TRUCK stages of a PFC. The next step will then be connection of the amputated limb to a machine perfusion system. This will occur when the patient has arrived at a team house, firebase, or other mission support site or during medical evacuation by helicopter or airplane (the HOUSE/PLANE stage of a PFC scenario). Machine perfusion of the limb bridges the time to replantation for up to 24 hours by providing oxygen and nutrients to the tissue. Amputated pig forelimbs will be used to test the different parts, as well as the complete PFC scenario for limb salvage. The occurrence of I/R injury will be assessed either by ex vivo perfusing the limbs with pig blood to simulate replantation for 12 hours or by reconnecting the amputated limbs to the blood vessels of the donor pig and reperfusing them in vivo (also for 12 hours). The main deliverable of the proposed project is a strategy to prevent I/R injury of amputated or completely devascularized limbs in a PFC scenario and an in vitro – in vivo model in which different drugs (limb protection at the RUCK/TRUCK stage) and machine perfusion systems/perfusate solutions (the HOUSE/PLANE stage) can be tested. The envisaged extension of the time to replantation from 6 hours to 33 hours would allow saving significantly more extremities than currently possible. In the vast majority of cases, replanted limbs provide a much better functional, esthetic, and psychological outcome for affected Service members and/or Veterans with orthopaedic injuries sustained in combat or combat-related activities, as well as for their families, caregivers, and the general public.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 19, 2019
- Source ID
- W81XWH1910714
Entities
People
- Robert Rieben
Organizations
- United States Army
- University of Bern