Impact of device variability and protocol differences on kidney function during normothermic machine perfusion: A comparative study using porcine and human kidneys

Abstract

Introduction: A growing interest in renal normothermic machine perfusion (NMP) has resulted in more clinically available perfusion devices. While all perfusion systems have the same aim, there are significant differences in their circuits, pumps, sensors, and software. Therefore, our objective was to assess the impact of different perfusion protocols and devices on kidney function and perfusion parameters during NMP.

Methods: Porcine kidneys were subjected to 30 min of warm ischemia, 24 h of static cold storage, and subsequently perfused for 6 h using (1) the Kidney Assist (KA) machine with a pressure of 75 mm Hg, (2) the KA device incorporating several adjustments and a pressure of 85 mm Hg (modified KA), or (3) the Perlife (PL) perfusion device (n = 4). Consecutively, discarded human kidneys were perfused using the KA or modified KA (n = 3) protocol.

Results: The PL group quickly reached the device's upper flow limit and consequently received a significantly lower pressure compared to the KA groups. The arterial pO₂ was significantly lower in the PL group. Yet, hemoglobin concentration increased over time, and oxygen consumption was significantly higher compared to the KA groups. Fractional sodium excretion was significantly lower in the PL group. Tissue ATP levels, urine production, and creatinine clearance rates did not differ between groups. In human kidneys, the modified KA group showed significantly lower vascular resistance, higher oxygen delivery, and lower levels of lactate in the perfusate compared to the KA group.

Conclusions: This study shows that perfusion characteristics and kidney function are significantly influenced by the perfusion protocol and the device and its settings during normothermic machine perfusion and therefore should be interpreted with caution.

Keywords: kidney transplantation; normothermic machine perfusion; perfusion device.

FIGURE 1

Experimental design. Fr, French; KA, Kidney Assist; KA+WA, Kidney Assist with workaround; (P), pressure setting; PL, perlife; m, medium; s, small; (T), temperature setting. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 2

Perfusion setup. (A). Schematic overview of Kidney Assist perfusion setup. The extra shunt line and the infusion of vasodilation of the modified protocol are shown in green. (B). Picture of Kidney Assist perfusion setup. (C). Schematic overview of PerLife perfusion setup. (D). Picture of PerLife perfusion setup. D, pressure dome; T, temperature sensor. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 3

Pressure drop versus flow rate for different cannulas. Measured for the (A) small (KP7‐15FJ) and medium (KP10‐20FJ) metal patch cannula recommended when using the Kidney Assist or PerLife perfusion device, and (B) 8, 10, and 12 French straight cannulas recommended by the manufacturers when lacking an arterial patch. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 4

Perfusion parameters during NMP. As shown by (A) the renal arterial flow, (B) mean arterial pressure, (C) the renal resistance, (D) the accumulative urine production, (E) perfusate temperature, and (F) the renal cortex temperature. *p < 0.05, **p < 0.01, and ****p < 0.0001. Values are expressed as mean ± SD (n = 4 kidneys per group). KA, Kidney Assist; PL, PerLife. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 5

Oxygenation and metabolism during NMP. As measured by the (A) arterial partial oxygen pressure, (B) venous partial oxygen pressure, (C) arterial hemoglobin levels, (D) oxygen delivery, (E) oxygen consumption, and (F) renal cortex ATP levels, (G) fractional sodium excretion, and (H) metabolic coupling. Values were measured at the arterial sample port. *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001. Values are expressed as mean ± SD (n = 4 kidneys). KA, Kidney Assist; PL, PerLife. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 6

Renal morphology and injury during NMP. As shown by the (A) general tissue morphology pre‐NMP, and (B) post‐nmp (200× magnification) (C) LDH levels in the perfusate, (D) ASAT levels in the perfusate, (E) lactate levels in the perfusate, (F) the hemolysis index. Values are expressed as mean ± SD (n = 4 kidneys). KA, Kidney Assist; PL, PerLife. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 7

External pressure and flow measurements. Measured by an external TruWave pressure transducer and an external Transonic flow sensor added to the (A) Kidney Assist circuit and (B) PerLife circuit. (C) Pressures measured in the Kidney Assist circuit, (D) pressures measured in the PerLife circuit, (E) flow measured in the Kidney Assist circuit, and (F) flow measured in the PerLife device circuit. **p < 0.01, ***p < 0.001, and ****p < 0.0001. Values are expressed as mean ± SD (n = 4 kidneys per group). KA, Kidney Assist; PL, PerLife. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 8

Perfusion parameters during pre‐clinical NMP. As shown by (A) the renal arterial flow, (B) renal resistance, (C) perfusate temperature, (D) accumulative urine production, (E) oxygen delivery, and (F) oxygen consumption. *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001. Values are expressed as mean ± SD (n = 3 kidneys). HC, historical cohort; KA, Kidney Assist; WA, workaround. [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 9

Injury markers during pre‐clinical NMP. As shown by the (A) LDH perfusate levels, (B) ASAT perfusate levels. (C) Arterial lactate levels, (D) hemolysis index. *p < 0.05. Values are expressed as mean ± SD (n = 3 kidneys). KA, Kidney Assist; WA, workaround. [Color figure can be viewed at wileyonlinelibrary.com]