EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Observing graft blood supply post kidney trans-plantation is essential. Compromised graft perfusion must be identified without delay to preserve organ survival. Implantable probes have revolutionised the graft monitoring process in kidney transplantation leading to safe, continuous, and distinct monitoring of blood supply. The Implantable Cook-Swartz Doppler Flow Monitoring System allows immediate salvaging of a compressed kidney. The implantable Doppler probe can easily and effectively identify such cases and save the limited number of organs that are available to today’s patients.

Observing graft blood supply after a kidney transplant is essential. Compromised graft perfusion must be identified without delay to preserve organ survival. With today’s increasing demand for kidneys, postoperative surveillance must evolve to prolong transplant success. Traditional methods (eg, Doppler ultrasound) can be slow and ambiguous. They also must be performed repetitively after kidney transplantation.

Implantable probes have revolutionized graft monitoring during kidney transplantation, leading to safe, continuous, and distinct monitoring of vascular anastomoses. By adopting this technique (eg, initially introduced to observe microvascular tissue transplants,¹ free flaps,² and pediatric liver transplants³), surgeons have become more effective at monitoring postoperative grafts. Our team has used the probe quickly and effectively to monitor blood flow to the kidney. This technique provides immediate indication of blood flow and, should it be required, allows the surgeon to readjust the position of the kidney to maximize flow before incision closure, reducing the need for postoperative exploration. By adopting this method, we can be assured that the kidney is perfused, and we eliminate the need for ultrasound monitoring. 7 days after surgery the probes are removed. Removal is simple, and is done by gentle traction on the wire (1/10th lb approximately, 50 g pressure) that disengages the crystal from the cuff.

Implantation of the probe on the renal artery during transplant can ensure blood flow to the kidney. Venous return can also be monitored using the probe; however, it is costlier. Similarly, multiple probes may be inserted should there be multiple anastomoses; but again, this would increase cost. We use the Implantable Cook-Swartz Doppler Probe (Cook Vascular Inc, Vandergrift, PA, USA) (Figure 1).⁴

In March 2014, a 45-year-old man with chronic renal failure underwent a live-donor kidney transplant from his 31-year-old sister who had undergone a bone marrow transplant. The recipient had a body mass index of 28 kg/m². The same surgical team performed both the nephrectomy and the transplant. The “finger-assisted” nephrectomy technique⁵ was used to remove the healthy kidney. No complications were encountered during the nephrectomy.

Insertion was uneventful; and immediate perfusion was observed once the vascular clamps were removed and urine was produced instantly. The implantable Cook-Swartz Doppler Probe was secured to the renal artery using its silicone cuff. Monitoring of blood flow began once the probe was attached to the receiver. The instantaneous and loudly audible signal produced confirmed a continuous blood flow, in addition to the clearly visible healthy kidney. This allowed for closure of the incision. At this point, all was going well; however, by the time the oblique muscle layers were closed, the Doppler signal was lost completely. This prompted an urgent reopening of the wound to explore the kidney. The kidney was found to be poorly perfused; it was blue in color. Critical repositioning saw perfusion recover within seconds, allowing the surgeon to close the wound, with a sustained Doppler signal. The signal remained strong throughout the patient’s recovery.

Should the probe not have been inserted during surgery, there would have been no suspicion that they kidney was compressed at any time. Several hours would have gone by, before realising the lack of perfusion inevitably leading to a loss of the transplanted kidney.

Use of the implantable Doppler probe allowed immediate rectification of the severely reduced blood flow. No further treatment was required and the patient recovered quickly.

A 2011 London study⁶ conducted by the same surgical team, assessed the feasibility of the probe in renal transplant patients. Fifteen consecutive transplant recipients had the probe implanted. Results were excellent, with only 1 Doppler ultrasound having to be ordered during the 15 admissions. There were no reported complications, and all probes were easily removed.

A 2014 study by Wax and associates⁷ determined that an implantable Doppler probe used to monitor did increase detection of immediate flap failure. The authors’ prospective analysis comprised 1142 flaps in the study cohort. The implantable probe detected 134 intraoperative flow problems (11.7%), all were successfully revised. Overall survival was 97.6%. Sensitivity was 87%, with a specificity of 99%.

In 2013, a Canadian study by Poder and associates⁸ concluded that the implantable Doppler system is more effective than the conventional methods to monitor free flap perfusion. Sixty-eight cases of head and neck free flaps were performed during 4 years. Only 4 of the 68 free flaps presented with a compromised perfusion. The improved free flap success rate is because of the precise and early detection of compromised flap perfusion by the implantable Doppler. As a result, salvage rates improved as well.

In conclusion, immediate intervention is required when treating the lowering or cessation of blood supply to the transplanted organ. The implantable Doppler probe can easily and effectively identify such cases, and save the limited number of organs that are available to today’s patients.

Volume: 14 Issue: 4 August 2016

FULL TEXT