Intra-abdominal Cooling System for the Transplanted Kidney

Since its introduction, the minimally invasive, robot-assisted approach has become an important alternative in kidney transplantation surgery.¹ However, there is a concern about possible increases in warm ischemia time of the transplanted kidney. Recently, Meier et al² described a novel intra-abdominal cooling system to address the lengthened ischemia time. In robot-assisted kidney transplantation in porcine models, they succeeded in suppressing the temperature elevation of the donated kidney during anastomosis with their cooling device. Similarly, we developed simple thermo-barrier bags (TBBs) which aim to suppress the temperature of the transplanted kidney in the intra-abdominal cavity. In a porcine kidney transplantation model, the TBB, which was designed to look like a purse, was effective in suppressing the temperature. The temperature of the porcine model with a TBB was 20°C with an operative time of 30 minutes, whereas the temperature of a porcine model without a TBB rose as high as 30°C.³ Meier et al² reported that their novel cooling device kept the temperature of the recovered kidney at 4°C to 6°C for 70 minutes during vascular anastomosis until reperfusion. On the other hand, the temperature of the porcine model without a cooling device elevated as high as 30°C at 30 minutes in the abdominal cavity, similar to our data.

At present, the use of topical ice-cold solution to maintain the kidney temperature at 20°C during anastomosis in a robot-assisted surgery is thought to be effective.⁴ Therefore, we additionally tested the method of preserving the transplanted kidney with the ice-cold solution in a newly developed TBB when performing anastomosis (Figure 1). This modified method enabled us to keep the temperature of the transplanted kidney at 20°C for >60 minutes.

FIGURE 1.

TBB in place after anastomosis of the back wall of the renal artery. A new TBB was made of medical grade silicone. Topical ice-cold solution was also dripped on the surface of the transplanted kidney. TBB, thermo-barrier bag.

The other issue is the safety of their device concerning the potential for ignition caused by the surgical knife. Energy devices, such as surgical knives, are commonly adopted in robot-assisted surgeries. As the Active Cooling System developed by Meier et al uses reperfusion by ethanol for cooling, potential ignition should always be taken into consideration. The safety features, as well as the cost-effectiveness of the device, should be of utmost importance.

As reported by Meier, there are challenges with large animal experiments, such as kidney transplant in porcine models. It is usually difficult to conduct assessments of live pigs and to demonstrate their improved renal function because of the ethical issues. In contrast to rats and mice, in-bred pigs are limited in availability. Therefore, when conducting pig experiments that require duration of >4 days, researchers are often forced to administer immunosuppressive drugs to the pigs. Are there any alternative assessments to confirm the effectiveness of the temperature control of the intra-abdominal transplanted kidney in the acute phase other than evaluating the urine output?⁴

In this Letter to the Editor, we seek to exchange opinions with kidney transplantation experts, based on our experiments in this field, regarding the effectiveness and the safety features of Dr. Meier's medical device.