Normothermic Perfusion

Normothermic Perfusion

June 2014

The Next Frontier in Organ Transplantation

42 Technology consultants recently attended the Cardiff Transplant Symposium, where this year’s core theme was organ preservation.

For many patients suffering major organ failure, a transplant offers the best prospect of a return to normal life, and in many cases it is the only therapy that can save their lives.

For all the major organs (liver, pancreas, kidney, heart and lung) there is a waiting list and the rate of transplantation is limited primarily by the availability of suitable donor organs.

One of the key potential areas for improvement is in the storage, transportation and assessment of donor organs. The traditional method of preservation has been to rapidly perfuse the organ with cold preserving fluid after extraction and keep it on ice during subsequent transportation, but organs are damaged both by being kept cold without oxygen and also during the period when they are re-perfused. Some benefit has been seen with cold machine perfusion where cooled fluid is continuously circulated through the organ but the results are mixed.

The future, therefore, may lie in Normothermic Perfusion (NP), whereby organs are kept at normal body temperature, with constant circulation of blood which is continually supplied with oxygen and nutrients.

With NP, the preserved heart continues to beat, lungs continue their breathing action and kidneys continue to make urine. NP offers both the chance to preserve the organ in optimal conditions, while restocking its reserves of ATP, but also to evaluate its actual performance prior to making the decision to transplant it.

It is, however, no trivial task to create a representative simulation of the human body in which to preserve the organ which is affordable, reliable, easy to use and transportable. For many organs an extended period of NP (long enough for transportation) would require complex processes to remove waste products which build up in the circulating blood. In effect, keeping a heart alive for an extended period requires a kidney.

Despite the challenges, research continues and great strides continue to be made. A team from Cambridge has successfully transported a beating heart from donor to recipient (including travel by plane); a team from Oxford has developed a transportable NP machine for livers; and a team in Leicester has demonstrated that simply using a period of NP as a functional evaluation technique could potentially enable up to 200 additional kidney transplants each year, by determining which of the kidneys traditionally rejected are in fact fully functional.

Though some of the hurdles are medical, there is a clear engineering challenge. Equipment for NP requires precise thermal and fluid management, inline measurement of a host of parameters, careful design to minimise the cost of the disposable parts of the machine, and implementation of numerous control algorithms to ensure reliable unattended operation of the equipment during transportation.

It’s worth noting that a kidney transplant can save the local healthcare system £250k in otherwise unavoidable dialysis costs over the lifetime of the successful transplant – a saving which is returned at a rate of £25k per annum from year 2 onwards. Any technique which increases the number of usable kidneys therefore offers a potentially strong return on investment.

Normothermic Perfusion is one of many medical areas where 42 Technology’s extensive experience in fluid and thermal management, sensor interfacing , complex control algorithms and user centred design makes it possible to replace a complex array of instruments with a single easy to use instrument, enabling best practice to be replicated and freeing the clinician to concentrate on patient needs.

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