Effects of air embolism size and location on porcine hepatic microcirculation in machine perfusion

Abstract

The handling of donor organs frequently introduces air into the microvasculature, but little is known about the extent of the damage caused as a function of the embolism size and distribution. Here we introduced embolisms of different sizes into the portal vein, the hepatic artery, or both during the flushing stage of porcine liver procurement. The outcomes were evaluated during 3 hours of machine perfusion and were compared to the outcomes of livers with no embolisms. Dynamic contrast-enhanced ultrasound (DCEUS) was used to assess the perfusion quality, and it demonstrated that embolisms tended to flow mostly into the left lobe, occasionally into the right lobe, and rarely into the caudate lobe. Major embolisms could disrupt the flow entirely, whereas minor embolisms resulted in reduced or heterogeneous flow. Embolisms occasionally migrated to different regions of the same lobe and, regardless of their size, caused a general deterioration in the flow over time. Histological damage resulted primarily when both vessels of the liver were compromised, whereas bile production was diminished in livers that had arterial embolisms. Air embolisms produced a dose-dependent increase in vascular resistance and a decline in oxygen consumption. This is the first article to quantify the impact of air embolisms on microcirculation in an experimental model, and it demonstrates that air embolisms have the capacity to degrade the integrity of donor organs. The extent of organ damage is strongly dependent on the size and distribution of air embolisms. The diagnosis of embolism severity can be safely and easily made with DCEUS. Liver Transpl 20:601-611, 2014. V C 2014 AASLD.Received October 12, 2013; accepted January 5, 2014.Air embolisms in donor organs are a well-known occurrence. Wolf et al. 1 demonstrated that before transplantation, one-third of donor livers contain intrahepatic air, whereas Liu et al. 2 showed that embolisms occur largely as a result of the routine handling of donor organs. Air can be actively perfused into the donor organ's vasculature during the delivery of the cold flush at the time of procurement, 3,4 during a venovenous bypass, 5-7 and, as machine perfusion (MP) gains popularity, at the time of the connection and during dynamic donor organ preservation. 8 The passive introduction of air can occur when subatmospheric pressures are generated in the vasculature, such as when the organ is suspended above the fluid line and drained, the vasculature is perforated, or air is encapsulated during an anastomosis.2,4,9 Air embolisms are Abbreviations: ALT, alanine aminotransferase; CL, caudate lobe; DCEUS, dynamic contrast-enhanced ultrasound; HA, hepatic artery; LLL, left lateral lobe; LML, left medial lobe; MP, machine perfusion; PV, portal vein.

Layer-by-layer heparinization of decellularized liver matrices to reduce thrombogenicity of recellularized liver grafts

“…4BL hDLM grafts remained visually thrombogenic, with a similar distribution of clots as in the unmodified DLM, while an increased number of PDADMAC/heparin bilayers (8BL) resulted in a visually clot-free graft. Circulatory obstruction has been shown to lead to increases in vascular resistance during machine perfusion [22]. Higher efficiency of increasing number of BLs was confirmed by a dose–dependent increase in portal venous resistance; the lowest increase in resistance was observed in higher concentrations of heparin (4BL-2X, 8BL and 8BL–2X hDLM).…”

Intrapulmonary Shunting and Paradoxical Air Embolism in Liver Transplantation: A Case Report

“…The degree of air burden entering the right atrium in our patient did not exceed that which is typically observed with TEE during reperfusion, and only occurred at the time of reperfusion. It is also worth noting that air embolisms can occur during machine perfusion [ 7 ], potentially as a result of intravascular air entrapment from an incompletely sealed intravascular cannula, although machine perfusion can also wash out previously entrapped intravascular air due to continual flow through the allograft during preservation [ 8 ]. It is important to recognize the possibility of PAE during the time of reperfusion, which can be due to right-to-left shunting through a PFO or ASD from acute increases in right heart pressure, such as in the case of sudden RV dysfunction, increases in pulmonary vascular resistance, or increased preload.…”

Machine perfusion enhances hepatocyte isolation yields from ischemic livers

“…For human-sized organs the primary difference in perfusion design is that a dual inflow system would be set up to also accommodate flow to the hepatic artery. This can be done either with two separate circuits [54] or by using a split in flow after the pump [55]. …”