Measurement of renovascular circulating volume during hypothermic organ perfusion

Dynamic Parameters of Hypothermic Machine Perfusion-An Image of Initial Graft Function in Adult Kidney Transplantation?

Kidney allografts are subjected to ischemia reperfusion injury during the process of transplantation. Hypothermic machine perfusion (HMP) of deceased donor kidneys from organ procurement until transplantation is associated with a superior outcome when compared to static cold storage (SCS). Nevertheless, cold ischemia time (CIT) remains an independent risk factor for delayed graft function (DGF) in HMP-preserved kidney allografts as well. We performed a retrospective single-center study including all adult recipients who underwent deceased donor kidney-only transplantation at our center between January 2019 and December 2020. Beside the clinicopathological donor and recipient data, flow and resistance data during HMP were assessed. Short- and long-term kidney allograft outcome after end-ischemic HMP and SCS were analyzed and compared. Organ preservation consisted of either SCS (n = 88) or HMP (n = 45). There were no differences in recipient demographics and donor details between groups. CIT was significantly longer in the HMP group (16.5 [8.5−28.5] vs. 11.3 [5.4−24.1], p < 0.0001). The incidence of DGF as well as serum creatinine at discharge and at 1 year post transplant were comparable between groups. Duration of SCS prior to HMP was comparable among grafts with and without DGF. Flow rate and organ resistance at the start of HMP were significantly worse in DGF-kidney grafts (arterial flow 22.50 [18.00−48.00] vs. 51.83 [25.50−92.67] ml/min, p = 0.0256; organ resistance 123.33 [57.67−165.50] vs. 51.33 [28.17−111.50] mmHg/mL/min, p = 0.0050). Recipients with DGF had significantly worse creatinine levels at discharge (2.54 [1.08−7.64] vs. 1.67 [0.90−6.56], p < 0.0001) and at 1 year post transplant (1.80 [1.09−7.95] vs. 1.59 [0.87−7.40], p = 0.0105). In conclusion, baseline HMP parameters could be applied as a predictive tool for initial graft function, which in turn determines long-term outcome.

Assessing Kidney Graft Viability and Its Cells Metabolism during Machine Perfusion

Kidney transplantation is the golden treatment for end-stage renal disease. Static cold storage is currently considered the standard method of preservation, but dynamic techniques, such as machine perfusion (MP), have been shown to improve graft function, especially in kidneys donated by extended criteria donors and donation after circulatory death. With poor organ quality being a major reason for kidneys not being transplanted, an accurate, objective and reliable quality assessment during preservation could add value and support to clinicians’ decisions. MPs are emerging technologies with the potential to assess kidney graft viability and quality, both in the hypothermic and normothermic scenarios. The aim of this review is to summarize current tools for graft viability assessment using MP prior to implantation in relation to the ischemic damage.

The Benefits of Hypothermic Machine Preservation and Short Cold Ischemia Times in Deceased Donor Kidneys

BACKGROUND

Hypothermic machine perfusion (HMP) of deceased donor kidneys is associated with better outcome when compared to static cold storage (CS). Nevertheless, there is little evidence whether kidneys with short cold ischemia time (CIT) also benefit from HMP and whether HMP can safely extend CIT.

METHODS

We analyzed prospectively collected data from the Machine Preservation Trial, an international randomized controlled trial. Seven hundred fifty-two consecutive renal transplants were included: 1 kidney of each of the 376 donors was preserved by HMP, the contralateral organ was preserved by CS.

RESULTS

The mean CIT was 3:05 PM (SD, 4:58 AM). A subgroup analysis was performed, groups were based on CIT duration: 0 to 10 hours, 10 to 15 hours, 15 to 20 hours, or 20 hours or longer. Delayed graft function (DGF) incidence in the subgroup with up to 10 hours CIT was 6.0% (N = 3/50) in the HMP arm and 28.1% (N = 18/64) in the CS arm (univariable P = 0.002; multivariable odds ratio [OR], 0.02; P = 0.007). Cold ischemia time remained an independent risk factor for DGF for machine perfused kidneys recovered from donation after brain death donors (OR, 1.06; 95% confidence interval [CI], 1.017-1.117; P = 0.008), donation after circulatory death donors (OR, 1.13; 95% CI, 1.035-1.233; P = 0.006) and expanded criteria donors (OR, 1.14; 95% CI, 1.057-1.236; P = 0.001).

CONCLUSIONS

In conclusion, HMP resulted in remarkably lower rates of DGF in renal grafts that were transplanted after a short CIT. Also, CIT remained an independent risk factor for DGF in HMP-preserved kidneys.

Capsulotomy of Ischemically Damaged Donor Kidneys: A Pig Study

BACKGROUND

Ischemia-reperfusion injury of donor kidneys may worsen transplant outcome. Kidneys with severe injury, such as kidneys of donors after circulatory death, develop edema, which may lead to renal compartment syndrome with reduced tissue perfusion.

OBJECTIVE

We studied the effect of capsulotomy during hypothermic machine perfusion (HMP) of ischemically damaged porcine kidneys.

METHODS

Eight pairs of kidneys from slaughterhouse pigs were assigned to two groups (20 and 45 min of warm ischemia). After 21 h of HMP, capsulotomy was performed, and perfusion was continued for 2 h. During perfusion, machine flow (Q), renal resistance (RR), renovascular circulating volume (RCV), intraparenchymal pressure (IPP) and weight were recorded. Parenchymal injury was examined with methylene blue infusion.

RESULTS

Mean Q and RCV increased directly after capsulotomy [percentage increase (95% confidence interval): x0394;Q = 32% (17, 47), p = 0.001, and x0394;RCV = 19% (3, 35), p = 0.023]. Mean RR decreased [x0394;RR = -23% (-31, -15), p < 0.001]. Subanalysis comparing both warm ischemia groups showed no significantly different effect of capsulotomy between groups. There was no methylene blue leakage after capsulotomy in any kidney.

CONCLUSIONS

Renovascular perfusion can be improved with capsulotomy during HMP, without damaging the renal parenchyma. Follow-up studies need to determine which donor kidneys may benefit from capsulotomy.