Normothermic renal artery perfusion: a comparison of perfusates

Perfusate Composition and Duration of Ex-Vivo Normothermic Perfusion in Kidney Transplantation: A Systematic Review

Ex-vivo normothermic perfusion (EVNP) is an emerging strategy in kidney preservation that enables resuscitation and viability assessment under pseudo-physiological conditions prior to transplantation. The optimal perfusate composition and duration, however, remain undefined. A systematic literature search (Embase; Medline; Scopus; and BIOSIS Previews) was conducted. We identified 1,811 unique articles dating from January 1956 to July 2021, from which 24 studies were deemed eligible for qualitative analysis. The perfusate commonly used in clinical practice consisted of leukocyte-depleted, packed red blood cells suspended in Ringer’s lactate solution with Mannitol, dexamethasone, heparin, sodium bicarbonate and a specific nutrient solution supplemented with insulin, glucose, multivitamins and vasodilators. There is increasing support in preclinical studies for non-blood cell-based perfusates, including Steen solution, synthetic haem-based oxygen carriers and acellular perfusates with supraphysiological carbogen mixtures that support adequate oxygenation whilst also enabling gradual rewarming. Extended durations of perfusion (up to 24 h) were also feasible in animal models. Direct comparison between studies was not possible due to study heterogeneity. Current evidence demonstrates safety with the aforementioned widely used protocol, however, extracellular base solutions with adequate oxygenation, supplemented with nutrient and metabolic substrates, show promise by providing a suitable environment for prolonged preservation and resuscitation.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021231381, identifier PROSPERO 2021 CRD42021231381

Efficacy of liver graft washout as a function of the perfusate, pressure, and temperature

Donor graft washout can be impaired by colloids in organ preservation solutions that increase the viscosity and agglutinative propensity of red blood cells (RBCs) and potentially decrease organ function. The colloid-induced agglutinative effects on RBCs and RBC retention after liver washout with Ringer's lactate (RL), histidine tryptophan ketoglutarate solution, University of Wisconsin solution, and Polysol were determined as a function of the washout pressure (15 or 100 mm Hg) and temperature (4 or 37°C) in a rat liver washout model with (99m) Tc-pertechnetate-labeled RBCs. Colloids (polyethylene glycol in Polysol and hydroxyethyl starch in University of Wisconsin) induced RBC agglutination, regardless of the solution's composition. RL was associated with the lowest degree of (99m) Tc-pertechnetate-labeled RBC retention after simultaneous arterial and portal washout at 37°C and 100 mm Hg. RL washout was also associated with the shortest washout time. A single portal washout with any of the solutions did not result in differences in the degree of RBC retention, regardless of the temperature or pressure. In conclusion, no differences were found in portal washout efficacy between colloidal solutions, histidine tryptophan ketoglutarate, and RL. Simultaneous arterial and portal washout with RL at 37°C and 100 mm Hg resulted in the least RBC retention and the shortest washout time.

Normothermic kidney preservation

PURPOSE OF REVIEW

Kidneys from marginal or donation after cardiac death (DCD) donors are particularly susceptible to injury during hypothermic preservation and may benefit from alternative methods of preservation. Normothermic preservation can be adapted to improve the quality of kidneys for transplantation by a variety of techniques.

RECENT FINDINGS

Extracorporeal membrane support to maintain circulation before cooling and organ retrieval has been used to improve the condition of DCD donor kidneys, with lower rates of delayed graft function (DGF) compared with standard retrieval conditions. Experimentally, normothermic perfusion has been used in conjunction with hypothermic techniques as a resuscitation technique to improve graft outcome. An ex-vivo porcine kidney model showed that energy levels could be replenished to improve tissue perfusion during reperfusion. This technique was translated into a porcine transplant model demonstrating that it was a feasible and safe method of preservation.

SUMMARY

Normothermic preservation techniques have the potential to be adapted into an improved method of retaining tissue viability compared with hypothermic techniques. Furthermore, they may be used as a device to enhance and assess the condition of the kidney which would be particularly beneficial for kidneys from DCD donors.