Publications by authors named "Michael A Zimmerman"

Ischemia-reperfusion injury (IRI) profoundly impacts organ transplantation, especially in orthotopic liver transplantation (OLT). Disruption of the mitochondrial respiratory chain during ischemia leads to ATP loss and ROS production. Reperfusion exacerbates mitochondrial damage, triggering the release of damage-associated molecular patterns (DAMPs) and inflammatory responses.

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Orthotopic liver transplantation remains the definitive treatment for patients with end-stage liver disease. Unfortunately, the increasing demand for donor livers and the limited supply of viable organs have both led to a critical need for innovative strategies to expand the pool of transplantable organs. The mitochondrion, central to hepatic cellular function, plays a pivotal role in hepatic ischemic injury, with impaired mitochondrial function and oxidative stress leading to cell death.

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Debate continues as to whether choledochoduodenostomy (CDD) can be used instead of Roux-en-Y choledochojejunostomy (CDJ) when duct-to-duct (DTD) is not an option. We hypothesized that CDD and CDJ had similar rates of complications. All deceased-donor liver transplantations from September 2011 to March 2020 were categorized by biliary reconstruction.

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Quantitative measurement of the degree of hepatic ischemia-reperfusion injury (IRI) is crucial for developing therapeutic strategies for its treatment. We hypothesized that clearance of fluorescent dye through bile metabolism may reflect the degree of hepatic IRI. In this study, we investigated sodium fluorescein clearance kinetics in blood and bile for quantifying the degree of hepatic IRI.

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Article Synopsis
  • The study aimed to explore the effects of various pre-reperfusion treatments on pig livers following warm and cold ischemic injuries, simulating conditions relevant to liver transplants.
  • Results indicated that the subnormothermic regulated hepatic reperfusion (RHR-S) treatment significantly improved liver cell viability, reduced indicators of injury, and enhanced mitochondrial function compared to other treatment methods.
  • The findings suggest that RHR-S not only mitigates ischemia-reperfusion injury but also activates protective genes, indicating its potential for improving liver transplantation outcomes.
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Significance: Real-time information about oxygen delivery to the hepatic graft is important to direct care and diagnose vascular compromise in the immediate post-transplant period.

Aim: The current study was designed to determine the utility of visible diffuse reflectance spectroscopy (vis-DRS) for measuring liver tissue saturation in vivo.

Approach: A custom-built vis-DRS probe was calibrated using phantoms with hemoglobin (Hb) and polystyrene microspheres.

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Liver injury is one of the nonpulmonary manifestations described in coronavirus disease 2019 (COVID-19). Post-COVID-19 cholangiopathy is a special entity of liver injury that has been suggested as a variant of secondary sclerosing cholangitis in critically ill patients (SSC-CIP). In the general population, the outcome of SSC-CIP has been reported to be poor without orthotopic liver transplantation (OLT).

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We describe the challenging perioperative course of a 55-year-old patient with hepatic failure requiring liver transplantation (LT). Different modalities of the extracorporeal device were successfully used, ranging from veno-veno bypass to partial and full veno-veno extracorporeal membrane oxygenation (ECMO) in order to optimize preload, reduce bleeding from the collateral circulation, optimize acid base balance and/or improve oxygenation. The case highlights the potential use of the device as a rescue method in challenging cases.

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Background: Cholestasis is a sign of hepatic ischemia-reperfusion injury (IRI), which is caused by the dysfunction of hepatocyte membrane transporters (HMTs). As transcriptional regulation of HMTs during oxidative stress is mediated by nuclear factor erythroid 2-related factor 2, we hypothesized that bardoxolone methyl (BARD), a nuclear factor erythroid 2-related factor 2 activator, can mitigate cholestasis associated with hepatic IRI.

Methods: BARD (2 mg/kg) or the vehicle was intravenously administered into rats immediately before sham surgery, 60 min of ischemia (IR60), or 90 min of ischemia (IR90); tissue and blood samples were collected after 24 h to determine the effect on key surrogate markers of bile metabolism and expression of HMT genes (Mrp (multidrug resistance-associated protein) 2, bile salt export pump, , sodium-taurocholate cotransporter, and organic anion-transporting polypeptide 1).

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Neuroendocrine tumors (NET) are rare neoplasms with generally indolent growth behavior. The liver is the most common site of NET metastasis. The NET metastatic spread to the liver are usually multiple tumors involving bilateral hemilivers.

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Background: Patients undergoing liver transplantation (LT) frequently receive platelet transfusion (PLT) to minimize their risk of hemorrhage. Alloimmunization to platelets may lead to refractoriness to PLT. Data on the implications of platelet alloimmunization in patients undergoing LT remain limited.

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Background And Aims: The Organ Procurement and Transplantation Network recently approved liver transplant (LT) prioritization for patients with hepatocellular carcinoma (HCC) beyond Milan Criteria (MC) who are down-staged (DS) with locoregional therapy (LRT). We evaluated post-LT outcomes, predictors of down-staging, and the impact of LRT in patients with beyond-MC HCC from the U.S.

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Unlabelled: Biliary complications (BC) following orthotopic liver transplantation (OLT) is strongly associated with inferior patient outcomes and increased healthcare cost. BC in high-acuity patients can be lethal. While the utility of staged biliary reconstruction after liver transplantation (SBRALT) has been reported in adult and pediatric OLT, biliary outcome data are scarce.

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Background: Orthotopic liver transplantation (OLT) after neoadjuvant therapy (NT) in well-selected patients with unresectable hilar cholangiocarcinoma (CCA) achieves excellent recurrence-free survival. Current criteria for NT-OLT exclude patients with locally advanced hilar and intrahepatic CCA from potential cure. We sought to evaluate the efficacy of NT in downstaging locally advanced CCA, and examine outcomes after OLT.

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Objective: The aim of the study was to determine the rate, predictors, and impact of complete pathologic response (cPR) to pretransplant locoregional therapy (LRT) in a large, multicenter cohort of hepatocellular carcinoma (HCC) patients undergoing liver transplantation (LT).

Background: LRT is used to mitigate waitlist dropout for patients with HCC awaiting LT. Degree of tumor necrosis found on explant has been associated with recurrence and overall survival, but has not been evaluated in a large, multicenter study.

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Background: The effect of hepatic ischemia-reperfusion injury (IRI) on bile transporter (BT) gene expression is unknown. We hypothesized that abnormal expression of BTs during hepatic IRI is dependent on nuclear factor erythroid 2-related factor 2 (NRF2), which contributes to the cholestasis after reperfusion.

Methods: Sham surgery and short (60 min) or long (90 min) periods of warm ischemia time (WIT) with or without reperfusion for 24 h were applied to wild-type Sprague-Dawley rats and Nrf2 knockout rats (n = 5 per group).

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Introduction: Biliary complications after pediatric orthotopic liver transplantation remain causes of significant patient morbidity. Staged operative approach in complex hepatobiliary surgery has improved postoperative outcomes but has not been evaluated in pediatric orthotopic liver transplantation. We sought to analyze the outcomes of staged biliary reconstruction after orthotopic liver transplantation in high acuity patients.

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Deterioration in mitochondrial function leads to hepatic ischemia and reperfusion injury (IRI) in liver surgery and transplantation. 3D optical cryoimaging was used to measure the levels of mitochondrial coenzymes NADH and FAD, and their redox ratio (NADH/FAD) gave a quantitative marker for hepatocyte oxidative stress during IRI. Using a rat model, five groups were compared: control, ischemia for 60 or 90 minutes (Isc60, Isc90), ischemia for 60 or 90 minutes followed by reperfusion of 24 hours (IRI60, IRI90).

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Living donor liver transplantation (LDLT) is a technically demanding endeavor, requiring command of the complex anatomy of partial liver grafts. We examined the influence of anatomic variation and reconstruction techniques on surgical outcomes and graft survival in the 9-center Adult-to-Adult Living Donor Liver Transplantation Cohort Study (A2ALL). Data from 272 adult LDLT recipients (2011-2015) included details on anatomic characteristics and types of intraoperative biliary reconstruction.

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Objective: To evaluate the effect of pretransplant bridging locoregional therapy (LRT) on hepatocellular carcinoma (HCC) recurrence and survival after liver transplantation (LT) in patients meeting Milan criteria (MC).

Summary Background Data: Pre-LT LRT mitigates tumor progression and waitlist dropout in HCC patients within MC, but data on its impact on post-LT recurrence and survival remain limited.

Methods: Recurrence-free survival and post-LT recurrence were compared among 3601 MC patients with and without bridging LRT utilizing competing risk Cox regression in consecutive patients from 20 US centers (2002-2013).

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Restoration of blood flow to an ischemic organ results in significant tissue injury. In the field of liver transplantation, ischemia-reperfusion injury (IRI) has proven to be a formidable clinical obstacle. In addition to metabolic stress and inflammation, IRI results in profound graft dysfunction and loss.

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: For patients with hepatoblastoma, a timely and complete resection of the tumor is critical to the patient's tumor recurrence-free survival. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS), a 2-stage hepatectomy procedure, has revolutionized the surgical management of large hepatic tumors with insufficient future liver remnant (FLR) at presentation. Although existing data support the utility of ALPPS in adults with primary and metastatic hepatobiliary malignancy, the literature in children is scarce.

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Background: Orthotopic liver transplantation is the definitive treatment modality for patients with end-stage liver disease. Pre-orthotopic liver transplantation renal dysfunction has a significant negative influence on outcomes post-orthotopic liver transplantation. Intraoperative renal replacement therapy is an adjunctive therapy to address the metabolic challenges during orthotopic liver transplantation in patients with a high acuity of illness.

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