Peritransplant Cardiometabolic and Mitochondrial Function: The Missing Piece in Donor Heart Dysfunction and Graft Failure

Metabolic Considerations in Direct Procurement and Perfusion Protocols with DCD Heart Transplantation

Heart transplantation with donation after circulatory death (DCD) provides excellent patient outcomes and increases donor heart availability. However, unlike conventional grafts obtained through donation after brain death, DCD cardiac grafts are not only exposed to warm, unprotected ischemia, but also to a potentially damaging pre-ischemic phase after withdrawal of life-sustaining therapy (WLST). In this review, we aim to bring together knowledge about changes in cardiac energy metabolism and its regulation that occur in DCD donors during WLST, circulatory arrest, and following the onset of warm ischemia. Acute metabolic, hemodynamic, and biochemical changes in the DCD donor expose hearts to high circulating catecholamines, hypoxia, and warm ischemia, all of which can negatively impact the heart. Further metabolic changes and cellular damage occur with reperfusion. The altered energy substrate availability prior to organ procurement likely plays an important role in graft quality and post-ischemic cardiac recovery. These aspects should, therefore, be considered in clinical protocols, as well as in pre-clinical DCD models. Notably, interventions prior to graft procurement are limited for ethical reasons in DCD donors; thus, it is important to understand these mechanisms to optimize conditions during initial reperfusion in concert with graft evaluation and re-evaluation for the purpose of tailoring and adjusting therapies and ensuring optimal graft quality for transplantation.

Comment on Oehler et al. Outcome and Midterm Survival after Heart Transplantation Is Independent from Donor Length of Stay in the Intensive Care Unit. Life 2022, 12, 1053

Oehler et al. described an interesting finding, stating that length of stay (LOS) of the donors in the intensive care unit (ICU) did not have an impact on the outcomes and survival of recipients up to 5 years after heart transplantation (HTx) [...].

Mitochondrial responses to brain death in solid organ transplant

Mitochondrial dynamics are central to the pathophysiology of cellular damage and inflammatory responses. In the context of solid organ transplantation, mitochondria are implicated in immune activation in donor organs that occurs after brain death, as they are critical to the regulation of cellular stress response, cell death, and display energetic adaptations through the adjustment of respiratory capacity depending on the cellular milieu. Mitochondrial damage activates mitochondrial systems of fission, fusion, biogenesis, and mitochondrial autophagy, or mitophagy. The mechanistic pathways as well as therapies targeting mitochondrial physiology have been studied as plausible ways to mitigate the negative effects of brain death on donor organs, though there is no summative evaluation of the multiple efforts across the field. This mini-review aims to discuss the interplay of donor brain death, mitochondrial dynamics, and impact on allograft function as it pertains to heart, lung, liver, and kidney transplants.

Whole Blood Thiamine in Organ Donors After the Neurologic Determination of Death

INTRODUCTION

Metabolic resuscitation of organ donors and the attenuation of oxidative stress incurred by organs following brain death and transplantation have the potential to improve organ yield and allograft function. Thiamine (vitamin B1) is a vital coenzyme in both energy metabolism and the production of antioxidants that has not been studied in the donor population.

RESEARCH AIM

To determine the frequency of subclinical thiamine deficiency in brain-dead organ donors and its correlation with demographics, length of hospitalization, donor management, lactic acidosis, and the requirement for vasoactive support.

DESIGN

Prospective cohort study of brain-dead donors managed at a single organ procurement organization's organ recovery facility.

RESULTS

A total 64 donors were enrolled; 24 donors had thiamine levels drawn upon arrival and 40 donors had levels drawn at the time of organ procurement. Whole blood thiamine levels were inversely correlated with the time from death (P = .007) and 20% (8/40) of donors had levels below the normal range at the time of organ procurement. Demographic features of the donor were not associated with thiamine levels although longer hospital stays prior to death were associated with lower levels (P < .05). The presence and resolution of lactic acidosis was not associated with whole blood thiamine level. Higher thiamine levels were associated with earlier discontinuation of vasoactive support (P = .04).

DISCUSSION

Whole blood thiamine deficiency was not uncommon at the time of organ procurement. Thiamine may be associated with the requirement for hemodynamic support.