MHH researchers want to help people with traumatic amputations by preserving their limbs until they can be reattached. The number of traumatic amputations is increasing worldwide - for example due to accidents on the road, at work or during leisure time, but also as a result of terrorist attacks or war. Only a few specialist clinics are able to perform autologous replantation on these often life-threatening injuries, i.e. to reconnect severed limbs to the body in such a way that they regain all or at least some of their function. The operation must also be carried out quickly, as the amputations are usually stored in an ice pack and can only survive for a few hours without a blood supply. Professor Dr. Bettina Wiegmann, emergency physician and specialist in cardiac surgery at the University of Würzburg, is investigating how this so-called ischemia time can be reduced and how the severed limbs can be better stored and cared for until the operation. Clinic for Cardiac, Thoracic, Transplantation and Vascular Surgery Hannover Medical School (MHH) and Professor Dr. Kirsten Haastert-Talini, head of the "Peripheral Nerve Regeneration" working group at the MHH Institute of Neuroanatomy and Cell Biology. The scientists want to develop a limb care system that fits into every emergency ambulance as a transportable storage box and gives seriously injured people the chance of a life without amputation and prostheses. On the other hand, it should be possible to use it in a similar way to organ transplants to preserve donor extremities and then transplant them successfully. The scientists have now developed an initial plan for the construction of such an ex vivo extremity perfusion (EVEP), including perfusion instructions, and published it in the journal "Military Medical Research". "In Germany alone, there are around 56,000 amputations every year," says Professor Wiegmann, head of the "Ex-vivo Organ Perfusion" working group at the Lower Saxony Center for Biomedical Engineering, Implant Research and Development (NIFE), where the project funded by the Federal Ministry of Defence is based. In most cases, traumatically amputated limbs are replaced by prostheses. On the one hand, this is due to the lack of expertise in many clinics for the complicated surgical procedure of replantation, in which bone fractures have to be repaired, blood vessels reattached and nerves reconnected. Secondly, time plays a decisive role, as seriously injured patients must be stabilized as a matter of priority if they are to survive at all. The limb is kept on ice for this time. "It can sometimes even take days before the patient is stable enough for another operation," says the surgeon. However, the extremities do not survive this, as they suffer ischemia damage after a certain period of time without blood flow, in which the cells die due to the lack of oxygen. In order to save both the lives of the severely injured and the limbs, the scientists are relying on a procedure that works in a similar way to a transportable organ care system. This connects donor organs to an artificial blood circulation system via a pump and thus maintains organ function outside the body until transplantation. Professor Wiegmann has already successfully used such a care system clinically on the heart and lungs many times. "We have tested different perfusion solutions on large animal extremities and collected initial evidence that our system works reliably and can preserve the tissue for over six hours using various values such as blood gas analysis, serum markers, thermal imaging and joint mobility," explains Professor Wiegmann. In order to create conditions that are as realistic as possible, the scientists have previously scheduled two hours of warm ischemia time, during which the limb is not supplied with blood or other supplies. "This simulates the time between the traumatic amputation and arrival at the replantation center." To ensure that the limb functions as well as possible after reattachment, the research team is also keeping an eye on the nerves for the first time worldwide. "Severed nerves in the limb stump can lengthen and become entangled, causing phantom pain," explains Professor Haastert-Talini. To prevent this from happening and to ensure that the nerves grow out and together again in a targeted manner, their destroyed parts in the limb must first be completely broken down and the surrounding area prepared for the absorption of newly growing nerve fibers. This requires, among other things, various messenger substances that initiate a type of inflammatory reaction. "This is why, unlike in the Organ Care System, we do not use anti-inflammatory drugs in our limb perfusion solution," says the anatomist. "The basic instructions for our EVEP are in place," says Professor Haastert-Talini. "We have the tissue supply under control and have significantly reduced the formation of harmful fluid accumulations." Next, the scientists want to investigate how they can improve the composition of the perfusion solution so that the nerves are optimally prepared at the same time. They also want to extend the perfusion times so that longer transport times are possible. "The fine-tuning of our system should then make it possible for one surgical team to take care of the patient while a second team can prepare the limb for replantation at the same time." The scientists are convinced that the medical need for their development will continue to increase. "According to scientific studies, the number of traumatic amputations is expected to increase by more than 70 percent by 2050," says Professor Wiegmann. Service: The original paper "Ex-vivo limb perfusion in military and civilian medicine: inspired by ex-vivo organ perfusion, pioneered for traumatic limb amputation and peripheral nerve regeneration" can be found at here. Source: MHH
Time plays a decisive role
Model organ care system
Prevent nerves from proliferating
Fine-tuning as the next goal
Text: Kirsten Pötzke