Novel Use of Normothermic Machine Perfusion of the Liver: A Strategy to Mitigate Unexpected Clinical Events

We would like to highlight to the readership a case that demonstrates utility of normothermic machine perfusion (NMP), to facilitate a complex liver retransplant, pushing the boundaries in liver transplantation (LT) overcoming unpredictable clinical circumstances.

Over the last 5 years, there is a growing body of evidence supporting the safety and efficacy of NMP in LT.¹ The question now is not “can NMP be used,” but how best should it be used and in which circumstances?

We present a case of a 34-year-old man listed for his third liver transplant for late hepatic artery thrombosis, transplanted aged 4 years for biliary atresia, and aged 26 years for graft cirrhosis with unsuccessful hepatic vein stenting causing caval narrowing. His previous operations were complicated by significant intraabdominal adhesions, extensive portal hypertension, cocoon abdomen, enterocutaneous fistula, and multiple relaparotomies. This surgical complexity meant an extended explant time was anticipated, which would have caused a prolonged cold ischemia time (CIT) for any graft.

A fast-tracked liver graft from a donor after brain stem death was accepted (44-y-old woman, bilateral intracranial hemorrhage, body mass index 17 kg/m², alanine aminotranferase 60 IU/L) that had been declined by other centers due to positive screening for the human T-lymphotropic virus (HTLV) 1 antibody. Considering deterioration of the patients health, this graft was accepted, because he had lower limb edema progressing up to the thoracic wall, and a computed tomography scan demonstrated thrombosis of the inferior vena cava (IVC) and right hepatic vein, without extension to the right atrium on echocardiogram and a negative thrombophilia screen. His United Kingdom End Stage Liver Disease (UKELD) and Model for End Stage Liver Disease (MELD) were 63 and 17, respectively. With the recognized high false-positive rate of HTLV screening assays,² we utilized NMP after 07:34 hours of CIT, allowing additional time to repeat tests and clear doubts of HTLV status (Figure 1A).

FIGURE 1.: A, Liver perfusion circuit; (B) transesophageal echocardiogram identifying right atrial thrombus; (C) extracted right atrial thrombus; (D) schematic of heart bypass circuit utilized. A, donor liver on NMP with the OrganOx Metra (OrganOx Ltd, Oxford, United Kingdom): note the color coding of the cannulae: red—hepatic arterial cannula, yellow—portal venous cannula, and blue—inferior vena cava (IVC) return cannula; (B) dimensions of right atrial thrombus on echocardiogram marked by crosses and dotted lines; (C) extracted right atrial thrombus from with fleshy appearance denoting recent propagation. Histology of this extracted thrombus was rich with platelets, and there are plentiful neutrophils and relatively scanty fungal spores. Microbiology of this thrombus grew Candida albicans, and the patient was treated with an extended course of antimicrobials; and (D) superior vena cava (SVC) and left common femoral vein (LCFV) drainage with the return into the main pulmonary artery (PA). The SVC was snared before opening the right atrium (RA) as the cannula in the LCFV was short (32 cm); there was no need to snare the IVC.

The graft fulfilled the NMP Birmingham Viability Criteria for transplantation,³ and the patient was anesthetized for transplantation. Transesophageal echocardiogram had a new finding of a propagated IVC thrombus into the right atrium (Figure 1B), with significant risk of acute dislodgment and embolization within hours to days. Proceeding with the transplant held a risk of on-table death but represented the only chance of survival.

With the graft on NMP, the cardiothoracic team were consulted, proposing open extraction of the right atrial thrombus (Figure 1C) on a beating heart utilizing a novel right heart bypass support circuit (Figure 1D). LT was followed with the bypass support, with a total of 23 hours of NMP and a combined preservation time of 30.5 hours. A successful transplant operation was performed (extubated on D5, transferred to the ward on D26, and discharged home on D40). The patient has an excellent quality of life without any significant complications at 12 months follow-up.

We believe this case demonstrates how NMP is a vital tool to facilitate complex LT, where it is anticipated there will be prolonged CIT, the importance, in this case, being to mitigate the further increased CIT due to evolving unpredictable clinical events.