Thyroid hormone resuscitation after brain death in potential organ donors: A primer for neurocritical care providers and narrative review of the literature

Thyroid hormone protects human lung epithelial cells from cold preservation and warm reperfusion-induced injury

BACKGROUND

Cellular stress associated with static-cold storage (SCS) and warm reperfusion of donor lungs can contribute to ischemia-reperfusion (IR) injury during transplantation. Adding cytoprotective agents to the preservation solution may be conducive to reducing graft deterioration and improving post-transplant outcomes.

METHODS

SCS and warm reperfusion were simulated in human lung epithelial cells (BEAS-2B) by exposing cells to low potassium dextran glucose solution at 4 °C for different periods and then switching back to serum-containing culture medium at 37 °C. Transcriptomic analysis was used to explore potential cytoprotective agents. Based on its results, cell viability, caspase activity, cell morphology, mitochondrial function, and inflammatory gene expression were examined under simulated IR conditions with or without thyroid hormones (THs).

RESULTS

After 18 h SCS followed by 2 h warm reperfusion, genes related to inflammation and cell death were upregulated, and genes related to protein synthesis and metabolism were downregulated in BEAS-2B cells, which closely mirrored gene profiles found in thyroid glands of mice with congenital hypothyroidism. The addition of THs (T3 or T4) to the preservation solution increases cell viability, inhibits activation of caspase 3, 8 and 9, preserves cell morphology, enhances mitochondrial membrane potential, reduces mitochondrial superoxide production, and suppresses inflammatory gene expression.

CONCLUSION

Adding THs to lung preservation solutions may protect lung cells during SCS by promoting mitochondrial function, reducing apoptosis, and inhibiting pro-inflammatory pathways. Further in vivo testing is warranted to determine the potential clinical application of adding THs as therapeutics in lung preservation solutions.

Donor heart selection: Evidence-based guidelines for providers

The proposed donor heart selection guidelines provide evidence-based and expert-consensus recommendations for the selection of donor hearts following brain death. These recommendations were compiled by an international panel of experts based on an extensive literature review.

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

Primary graft dysfunction is an important cause of morbidity and mortality after cardiac transplantation. Donor brain stem death (BSD) is a significant contributor to donor heart dysfunction and primary graft dysfunction. There remain substantial gaps in the mechanistic understanding of peritransplant cardiac dysfunction. One of these gaps is cardiac metabolism and metabolic function. The healthy heart is an "omnivore," capable of utilizing multiple sources of nutrients to fuel its enormous energetic demand. When this fails, metabolic inflexibility leads to myocardial dysfunction. Data have hinted at metabolic disturbance in the BSD donor and subsequent heart transplantation; however, there is limited evidence demonstrating specific metabolic or mitochondrial dysfunction. This review will examine the literature surrounding cardiometabolic and mitochondrial function in the BSD donor, organ preservation, and subsequent cardiac transplantation. A more comprehensive understanding of this subject may then help to identify important cardioprotective strategies to improve the number and quality of donor hearts.

Hypothalamic function in patients diagnosed as brain dead and its practical consequences

Some patients who have been diagnosed as "dead by neurologic criteria" continue to exhibit certain brain functions, most commonly, neuroendocrine functions. In this chapter, we review the pathophysiology of brain death that can lead either to neuroendocrine failure or to preserved neuroendocrine functioning. We review the evidence on continued hypothalamic functioning in patients who have been declared "brain dead," examine potential mechanisms that would explain these findings, and discuss how these findings create additional confounds for brain death testing. We conclude by reviewing the evidence for the management of hypothalamic-pituitary failure in the setting of brain death and organ transplantation.

Renal Procurement: Techniques for Optimizing the Quality of the Graft in the Cadaveric Setting

PURPOSE OF REVIEW

Kidney transplantation is the best treatment for end-stage renal disease. However, due to organ shortage, suboptimal grafts are increasingly being used.

RECENT FINDINGS

We carried out a review on the methods and techniques of organ optimization in the cadaveric setting. Donor care is the first link in a chain of care. Right after brain death, there is a set of changes, of which hormonal and hemodynamic changes are the most relevant. Several studies have been conducted to determine which drugs to administer, although in most cases, the results are not definitive. The main goal seems rather achieve a set of biochemical and hemodynamic objectives. The ischemia-reperfusion injury is a critical factor for kidney damage in transplantation. One of the ways found to deal with this type of injury is preconditioning. Local and remote ischemic preconditioning has been studied for various organs, but studies on the kidney are scarce. A new promising area is pharmacological preconditioning, which is taking its first steps. Main surgical techniques were established in the late twentieth century. Some minor new features have been introduced to deal with anatomical variations or the emergence of donation after circulatory death. Finally, after harvesting, it is necessary to ensure the best conditions for the kidneys until the time of transplantation. Much has evolved since static cold preservation, but the best preservation conditions are yet to be determined. Conservation in the cold has come to be questioned, and great results have appeared at temperatures closer to physiological.

A Randomized Trial of Intravenous Thyroxine for Brain-Dead Organ Donors With Impaired Cardiac Function

RATIONALE

Brain death (BD) precipitates cardiac dysfunction impairing the ability to transplant hearts from eligible organ donors. Retrospective studies have suggested that thyroid hormone may enhance myocardial recovery and increase hearts transplanted. We performed a randomized trial evaluating whether intravenous thyroxine (T4) improves cardiac function in BD donors with impaired ejection fraction (EF).

METHODS

All heart-eligible donors managed at a single-organ procurement organization (OPO) underwent protocolized fluid resuscitation. Those weaned off vasopressors underwent transthoracic echocardiography (TTE) within 12 hours of BD and, if EF was below 60%, were randomized to T4 infusion or no T4 for 8 hours, after which TTE was repeated.

RESULTS

Of 77 heart-eligible donors, 36 were weaned off vasopressors. Ejection fraction was depressed in 30, of whom 28 were randomized to T4 (n = 17) vs control (n = 11). Baseline EF was comparable (45%, interquartile range [IQR] 42.5-47.5 vs 40%, 40-50, P = .32). Ejection fraction did not improve more with T4 (10%, IQR 5-15 vs 5%, 0-12.5, P = .24), although there was a trend to more hearts transplanted (59% vs 27%, P = .14). This difference appeared to be accounted for by more donors with a history of drug use in the T4 group, who exhibited greater improvements in EF (15% vs 0% without drug use, P = .01) and more often had hearts transplanted (12 of 19 vs 1 of 9, P = .01).

CONCLUSIONS

In this small randomized study of BD donors with impaired cardiac function, T4 infusion did not result in greater cardiac recovery. A larger randomized trial comparing T4 to placebo appears warranted but would require collaboration across multiple OPOs.

The Impact of l-Thyroxine Treatment of Donors and Recipients on Postoperative Outcomes After Heart Transplantation

OBJECTIVE

The effect of thyroid dysfunction on adverse outcomes has been studied in many different patient populations. The objective of this study was to investigate the effect of thyroid hormone supplementation of donors and recipients on postoperative outcomes after orthotopic heart transplantation.

DESIGN

Retrospective.

SETTING

Single center, university hospital.

PARTICIPANTS

Two-hundred and sixty-six consecutive patients undergoing heart transplantation.

INTERVENTIONS

No interventions.

MEASUREMENTS AND MAIN RESULTS

Demographic, hemodynamic, and clinical characteristics; donor and recipient United Network for Organ Sharing scores; and information on thyroid hormone support of donors and recipients were recorded. During the median follow-up of 4.59 years (interquartile range 4.26-4.92 y), 70 patients (26.3%) died. After adjustments were made for the United Network for Organ Sharing score, recipients who were treated preoperatively with l-thyroxine had a lower risk for all-cause mortality (adjusted hazard ratio [HR] 0.24, 95% confidence interval [CI] 0.06-0.98; p = 0.047) compared with recipients who were not treated with l-thyroxine. In addition, l-thyroxine treatment of donors was associated with a better recipient survival (HR 0.31, 95% CI 0.11-0.87; p = 0.025).

CONCLUSIONS

Pretransplantation thyroid hormone supplementation of donors and recipients was associated with improved long-term survival after heart transplantation.