Perfusion System for Organ Preservation

This invention relates to perfusion systems for organ preservation and particularly for preservation of kidneys.

In the procurement and transplantation of organs such as kidneys, it is essential to properly preserve the organ, and it has been customary to subject the organ to lower temperatures and a perfusion with a suitable perfusate.

Several methods of kidney perfusion have been used. Folkert O. Belzer, B. Sterry Ashby and J. Englebert Dunphy in Ann. Surg, 172:394, 1970, described a system for perfusion of kidneys by hypothermic pulsatile perfusion utilizing a pulsatile pump, a membrane oxygenator, a heat exchanger and a refrigeration unit. The perfusate was supplied by the pump through the heat exchanger and the oxygenator to the organ.

In another system described by A. W. Moberg, E. A. Santiago, R. V. Mason, M. J. Mozes, R. A. Campos and J. S. Najarian, in The Lancet, Dec. 25, 1971, a smaller self-contained system was provided utilizing an organ cassette which included an organ chamber, circulating fluid, membrane oxygenator and heat exchanger.

In a third type of system described by G. Claes, I. Blohme and L. E. Gelin in a paper to be published in preceedings from EDTA meeting in Berlin, July 1971, a similar system was provided which included non-pulsatile perfusion, i.e., a pump that did not pulsate.

Among the objects of the present invention are to provide an improved perfusion system which is simpler, more compact and can be utilized portably or otherwise, which does not utilize pulsatile perfusion, and which incorporates an organ cassette that can be interchanged with other systems.

FIG. 1 is a perspective view of an apparatus embodying the invention.

FIG. 2 is a partly diagrammatic view on an enlarged scale of a portion of the system shown in FIG. 1.

FIG. 3 is a partly diagrammatic plan view of a portion of the system.

Referring to FIG. 1, the perfusion system embodying the invention comprises a wheeled cart 10, a refrigeration unit 11, a pump unit 12 and a cassette 13.

The cassette 13 is preferably made of walls of transparent material such as acrylic plastic and includes an organ receptacle portion 14 removably mounted on a second portion 15. The bottom wall 16 of the portion 14 is adapted to support the organ such as the kidney. A bubble trap 17 is mounted on the side wall of the portion 14 and includes an outlet 18 that extends through the wall and is adapted to be connected to the organ K. The perfusate is supplied to the bubble trap 17 through a line 19 extending from a pump 20 in the pump unit 12. The pump 20 is of the roller type, that is, a non-pulsatile pump. Liquid or perfusate from the kidney K passes through an oxygenator 21 on the wall of the portion 15 of cassette 13 after flowing across the bottom wall 16 and is subjected to oxygen or a mixture of oxygen and carbon dioxide through a line 22 extending from a supply tank or tanks 23 on the cart which have the usual pressure controls 24. The oxygenator is of the well-known membrane type wherein the liquid passes over a membrane and is subjected to the gas. The perfusate after passing through the oxygenator 21 extends to a line 24 that passes to a heat exchanger 25 and, in turn, to an inlet line 26 extending to the pump 20. The refrigeration unit 11 includes inlet and outlet lines 26, 27 extending to the heat exchanger 25 for cooling for the perfusate. A flow regulator is preferably provided on the cart for use in connection with each supply tank 23.

The refrigeration unit 11 includes the usual compressor that is driven electrically so that an electric cord may be used to energize the motor driving the compressor. The pump unit 12 similarly includes an electric cord for driving the motor of the pump. In addition, the pump unit 12 includes a self-contained battery for operating the pump when it is desired to transport the organ. The pump unit 12 thus includes a battery 28, a switching device and converter 29 for providing power from an AC line or the battery 28 to drive the AC-DC motor 30 that in turn drives the pump 20.

It can thus be seen that the perfusion system basically includes a cart 10, a refrigeration unit 11, a pump 12 and a cassette 13, the cassette 13 containing the organ chamber 14, bubble trap 17, heat exchanger 25, and membrane oxygenator 21. When it is desired to transport the organ, ice can be incorporated into the area surrounding the heat exchanger of portion 15 of the cassette 13, the refrigeration lines 26, 27 being disconnected, and the power supply being switched so that the pump is operated by the battery. Then by merely grasping handles 31 on the pump unit, the pump unit 12 and cassette 13 can be transported. Where it is desired to connect the cassette to other systems, the cassette 13 can be disconnected from the pump unit. For purposes of monitoring the pressure of the perfusate, a line 32 extends from a pressure gauge 33 in the pump unit to above the level of the liquid in the bubble chamber 17.

The apparatus described has been found to produce excellent results. Thus, when canine kidneys were perfused for 48 to 72 hours, the viability parameters (flow, pressure, oxygen tension, lactic acid, pH) were within normal limits. Minimal weight gain was observed after preservation. After transplantation, the kidneys perfused for 48 hours showed a good vascular perfusion throughout the kidney as well as good urine output. After transplantation, the kidneys perfused for 72 hours functioned but did not show as good results as the kidneys perfused for 48 hours.

Typical operating conditions were: pressure of perfusate of cryoprecipitated plasma, 25-30 mm. of mercury; rate of flow of perfusate, 150 mil/min.; oxygen flow, 1 liter/min.; CO.sub.2 flow 8 mil/min.; pH 7.38-7.4; and average kidney weight 50 grams.

Although the apparatus has been described in connection with the preservation of kidneys, it can also be used in the preservation of other organs such as hearts, pancreases and livers.