Effects of brain death on donor organ viability

Energy status of pig donor organs after ischemia is independent of donor type

BACKGROUND

Literature is controversial whether organs from living donors have a better graft function than brain dead (BD) and non-heart-beating donor organs. Success of transplantation has been correlated with high-energy phosphate (HEP) contents of the graft.

METHODS

HEP contents in heart, liver, kidney, and pancreas from living, BD, and donation after cardiac death in a pig model (n=6 per donor type) were evaluated systematically. BD was induced under general anesthesia by inflating a balloon in the epidural space. Ten hours after confirmation, organs were retrieved. Cardiac arrest was induced by 9V direct current. After 10min of ventricular fibrillation without cardiac output, mechanical and medical reanimation was performed for 30min before organ retrieval. In living donors, organs were explanted immediately. Freeze-clamped biopsies were taken before perfusion with Celsior solution (heart) or University of Wisconsin solution (abdominal organs) in BD and living donors or with Histidine-Tryptophan-Ketoglutaric solution (all organs) in non-heart-beating donors, after perfusion, and after cold ischemia (4h for heart, 6h for liver and pancreas, and 12h for kidney). HEPs (adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, and phosphocreatine), xanthine, and hypoxanthine were measured by high-performance liquid chromatography. Energy charge and adenosine triphosphate-to-adenosine diphosphate ratio were calculated.

RESULTS

After ischemia, organs from different donor types showed no difference in energy status. In all organs, a decrease of HEP and an increase in hypoxanthine contents were observed during perfusion and ischemia, irrespective of the donor type.

CONCLUSION

Organs from BD or non-heart-beating donors do not differ from living donor organs in their energy status after average tolerable ischemia.

Endothelial activation in the transplanted human heart from organ retrieval to 3 months after transplantation: an observational study

BACKGROUND

Endothelial activation in the donor heart has been described variably after brain death and transplantation. We aimed to characterize the time course of endothelial activation in right ventricle (RV) and left ventricle (LV) during the acute phase of clinical transplantation.

METHODS

We studied biopsy specimens from the RVs and the LVs of 40 donor hearts: at initial assessment of the donor, at end-ischemia, and after 10 minutes of reperfusion. We also included follow-up RV biopsy specimens at 1 week, 1 month, and 3 months after surgery. Six of the patients had cystic fibrosis and were domino donors.

RESULTS

P-selectin and vascular cell adhesion molecule 1 (VCAM-1), but not E-selectin were up-regulated in brain-dead and in domino donors vs controls. Unused donor hearts (n = 6) had significantly less up-regulation of P-selectin and of VCAM-1. We found no difference between the RV and the LV during surgery, but we did see important time-dependent variations. P-selectin was present in 85% of vessels throughout transplantation and decreased to approximately 60% after transplantation (p < 0.001). We initially detected VCAM-1 in 20% of vessels, which decreased to 5% during storage, then increased to 47% at reperfusion, and gradually decreased thereafter (p < 0.001). E-selectin expression increased progressively from 15% initially to 45% at reperfusion and then decreased after surgery (p = 0.001). Thrombomodulin expression was decreased at baseline, and the decrease was accentuated afterward (p = 0.02). Patients with donor organ failure did not have a specific pattern of endothelial activation.

CONCLUSION

Cardiac transplantation is associated with marked endothelial activation, with no difference between the two ventricles. The changes persist in the post-operative period, even in the absence of acute rejection.

Immunosuppression for lung transplantation

As a result of advances in surgical techniques, immunosuppressive therapy, and postoperative management, lung transplantation has become an established therapeutic option for individuals with a variety of end-stage lung diseases. The current 1-year actuarial survival rate following lung transplantation is approximately 75%. However, the processes of acute and chronic lung allograft rejection have limited the long-term success of lung transplantation. Clinicians currently rely on a vast armamentarium of immunosuppressive agents to ameliorate graft rejection, but find themselves limited by an inescapable therapeutic paradox. Insufficient immunosuppression results in graft loss due to rejection, while excess immunosuppression results in increased morbidity and mortality from opportunistic infections and malignancies. Indeed, graft rejection, infection, and malignancy are the three principal causes of mortality for the lung transplant recipient. One should also keep in mind that graft loss in a lung transplant recipient is usually a fatal event, since there is no practical means of long-term mechanical support, and since the prospects of re-transplantation are low, given the shortage of acceptable donor grafts. This chapter reviews the current state of immunosuppressive therapy for lung transplantation, and suggests alternative paradigms for the management of future lung transplant recipients.

The influence of brain death on liver function

BACKGROUND

In this study, we investigated the influence of brain death on inflammatory response and the effects of brain death on liver function both directly after explantation and after reoxygenation.

METHODS

The influence of brain death on liver function was studied in rats using a brain death model and the liver slice model to mimic reoxygenation. Liver function was assessed by measuring the ATP content and the ATP-driven urea synthesis. The activation of non-parenchymal cells was studied by measuring mRNA levels of IL-10, cytokine production (IL-10 and IL-1 beta) and inducible nitric oxide synthases (iNOS) upregulation (mRNA) and protein level.

RESULTS

Brain death had no direct influence on the ATP content of the liver. However, it led to induction of several cytokines because of activation of non-parenchymal cells, which led to upregulation of iNOS and to nitric oxide metabolites production. It is known that cytokine production may influence the drug metabolism capacity; however, no influence of brain death on drug metabolism was observed. An explanation may be the relatively short experimental period.

CONCLUSIONS

Kupffer cells seem to be activated during the onset of brain death induction; however, they become quiescent when liver slices of brain dead rats were reoxygenated during incubation. Other non-parenchymal cells, possibly the endothelial cells, remain activated during incubation and reoxygenation in slices from brain death donors but not in slices from control livers. Future experiments in our rat liver transplantation model need to elucidate the implications of these findings.

Brainstem death testing in the UK'time for reappraisal? †

BACKGROUND

A diagnosis of brainstem death in the UK is based on clinical assessment rather than technical investigations, but is considered rigorous enough to be legally synonymous with death.

METHODS

A questionnaire in five sections concerning clinician details, initiation of support, criteria for testing, conduct of the tests, and the process of organ donation, was sent to all members of the Neuroanaesthesia Society.

RESULTS

The survey reveals evidence of failure to apply existing guidelines accurately and a wide variation in practice where the recommendations are not specific.

CONCLUSIONS

In an era of scrutiny of medical process, it is timely to consider whether the current guidelines should be revisited. Clarification of the approach to biochemical derangement, and the role of confirmatory tests when the residual effect of sedative agents cannot be excluded, are two areas worthy of debate.

Recent advances in the immunology of chronic rejection

Chronic allograft rejection is a slowly progressive, insidious process in which the host immune system continues to mount an immunological attack on a transplanted organ, ultimately resulting in the failure of the graft. To varying degrees, all solid organ grafts are at risk for chronic rejection and undergo a stereotypic process of injury and inflammation, eventually leading to parenchymal fibrosis. The clinical consequences of chronic rejection are particularly apparent in thoracic transplantation, where both patient and graft survival decline steadily over time and the opportunities for re-transplantation or long-term extracorporeal support are limited. A variety of antigen-dependent and antigen-independent factors are known to modulate the propensity for an organ to undergo chronic rejection. Recent clinical and laboratory research has suggested that distinct immunologic mechanisms may underlie the process of chronic rejection. Ultimately, strategies to induce long-term tolerance to alloantigens will be necessary to prevent chronic rejection and to abrogate the deleterious sequelae of chronic immunosuppression.