by Dr. Sunil Shenvi, Senior Consultant, HPB & Multiorgan Transplantation
Liver transplantation is a complex surgical procedure. It involves removing a liver from the donor and putting it into the recipient. After taking the liver out of the cadaveric donor, it has to be maintained in optimal condition so that it continues working well after transplantation. Currently practiced method involves storing the liver over ice to maintain low temperature. However, this process has a time limitation, may damage the liver further and may not be sufficient to protect the liver. For this reason, researchers are working hard to find new ways to keep donated liver viable. One of the recently invented methods is the use of perfusion machines which has shown promising results.
Where are we now?
Traditionally, harvested organs moved for transplantation are kept at a very low temperature by using infusing cold solution during removal of the organ and then storing it over ice. This process is called cold ischemia. Different organs can be kept in cold storage for different lengths before it becomes unusable. For example, a heart’s cold ischemia time is 4–6 hours, while a kidney lasts much longer, for 24–36 hours. The liver can be kept in cold storage between 8 and 12 hours. For a successful transplantation, efforts are made to keep cold ischemic time as short as possible.
According to the UNOS (United Network for Organ Sharing), more than 41,000 transplants occurred in 2021 in the United States of America. The liver is the second most commonly transplanted organ after the kidney worldwide. Unfortunately, the situation in India is not encouraging. The cadaveric donations are very few. Since most of the transplant centres are situated in big cities, the organ donations happen only in bigger cities. Even if organ donation happens in smaller cities, the transportation of donated organs becomes difficult. If machine perfusion becomes routine, this limitation can be circumvented.
What is a perfusion machine?
Perfusion machines as an alternative method of storing organs outside the body. The machine acts like the body’s heart and lungs, pumping blood like solution and oxygen into the donated organ. Additionally, hormones and nutrients are delivered to imitate what the liver would receive from the intestines and pancreas in a normal living person. It has been recently shown that a perfusion machine can preserve a liver graft for not a few hours but for several days. This makes it possible to perform liver transplant as an elective surgery rather than an emergency surgery in the middle of night. It also helps to assess the quality of the liver during the pumping process. We can conduct a few tests to check if the liver is fit for transplanting. If an unfit liver is transplanted into a recipient and if it does not work well, patients’ life is in danger and patients may need repeat transplant under emergency conditions. Machine perfusion is being widely used for Kidneys but its use in livers has been highlighted recently.
What’s the future of Machine perfusion?
Machine perfusion is theoretically suitable for all organs (apart from liver) although few adjustments have to be made in the technology being used currently. Machine perfusion of organs has an enormous potential to increase the number of organs available for transplants. Many livers are being discarded currently since surgeons are not sure if it’s worth transplanting those livers. If the organ is harvested in a remote area, it can be put on a pump and transported to a transplant centre. Machine perfusion can help to identify good livers and the number of unnecessary discards may come down. Researcher’s may develop therapies like gene therapy in future so that damaged livers can be repaired and used for transplantation.
But machine perfusion comes with a cost and it should be readily available even in remote places. The machines need to be maintained well. People have to be trained to use them and keep them in usable conditions. We need to overcome these limitations for machine perfusion to become widely available.
Dr. Sunil Shenvi, Senior Consultant, HPB & Multiorgan Transplantation