Current Strategies in Donor Selection and Management

Donor and recipient risk factors for the development of primary graft dysfunction following lung transplantation

Primary Graft Dysfunction (PGD) is a major cause of both short-term and long-term morbidity and mortality following lung transplantation. Various donor, recipient, and technical risk factors have been previously identified as being associated with the development of PGD. Here, we present a comprehensive review of the current literature as it pertains to PGD following lung transplantation, as well as discussing current strategies to mitigate PGD and future directions. We will pay special attention to recent advances in lung transplantation such as ex-vivo lung perfusion, thoracoabdominal normothermic regional perfusion, and up-to-date literature published in the interim since the 2016 ISHLT consensus statement on PGD and the COVID-19 pandemic.

Evaluation of Donor Lungs for Transplantation: The Efficacy of Screening Bronchoscopy for Detecting Donor Aspiration and Its Relationship to the Resulting Allograft Function in Corresponding Recipients

BACKGROUND

Potential organ donors often have suffered anoxic and/or traumatic brain injury during which they may have experienced aspiration of gastric material (AGM). Evaluation of such donors typically includes a screening bronchoscopic examination during which determinations of aspiration are made. The efficacy of this visual screening and its relationship to post-transplant allograft function are unknown.

METHODS

Before procurement, bronchoscopy was performed on donors in which both bronchoalveolar lavage fluid (BALF) was collected and a visual inspection made. As a marker of AGM, BALF specimens were analyzed for the presence of bile salts. Data collected on the corresponding recipients included primary graft dysfunction (PGD) score, post-transplant spirometry, acute rejection scores (ARS), and overall survival.

RESULTS

Of 31 donors evaluated, bronchoscopies revealed only 2 with visual evidence of AGM, whereas BALF analysis for bile salts indicated AGM in 14. As such, screening bronchoscopy had a sensitivity of only 7.1%. Visual detection of AGM via bronchoscopy was not associated with any resulting grade of PGD (χ2 = 2.96, P = .23); however, AGM defined by detection of bile salts was associated (χ2 = 7.56, P = .02). Over the first post-transplant year, the corresponding recipients experienced a similar improvement in allograft function (χ2 = 1.63, P = .69), ARS (P = .69), and survival (P = .24).

CONCLUSION

Visual inspection during a single bronchoscopic examination of lung donors underestimates the prevalence of AGM. The detection of bile salts in donor BALF is associated with early allograft dysfunction in the corresponding recipients but not with later allograft proficiency, acute rejection responses, or 1-year post-transplant survival.

Primary Graft Dysfunction: The Role of Aging in Lung Ischemia-Reperfusion Injury

Transplant centers around the world have been using extended criteria donors to remedy the ongoing demand for lung transplantation. With a rapidly aging population, older donors are increasingly considered. Donor age, at the same time has been linked to higher rates of lung ischemia reperfusion injury (IRI). This process of acute, sterile inflammation occurring upon reperfusion is a key driver of primary graft dysfunction (PGD) leading to inferior short- and long-term survival. Understanding and improving the condition of older lungs is thus critical to optimize outcomes. Notably, ex vivo lung perfusion (EVLP) seems to have the potential of reconditioning ischemic lungs through ex-vivo perfusing and ventilation. Here, we aim to delineate mechanisms driving lung IRI and review both experimental and clinical data on the effects of aging in augmenting the consequences of IRI and PGD in lung transplantation.

Management of the Potential Lung Donor

The use of donor management protocols has significantly improved recovery rates; however, the inherent instability of lungs after death results in low utilization rates of potential donor lungs. Donor lungs are susceptible to direct trauma, aspiration, neurogenic edema, ventilator-associated barotrauma, and ventilator-associated pneumonia. After irreversible brain injury and determination of futility of care, the goal of medical management of the donor shifts to maintaining hemodynamic stability and maximizing the likelihood of successful organ recovery.

Donor selection for multiorgan transplantation

PURPOSE OF REVIEW

There is limited data and guidance on donor selection for multiorgan transplantation. In this article, we review the current Organ Procurement and Transplantation Network policy on multiorgan allocation and the ideal donor criteria for each specific organ, in order to provide a framework to guide donor selection for various scenarios of multiorgan transplantation, including heart-kidney, heart-lung, heart-liver and heart-kidney-liver transplant procedures.

RECENT FINDINGS

Combined heart-kidney transplantation is the most common multiorgan transplant procedure and requires the most stringent HLA matching to ensure optimal graft survival. Using the virtual crossmatch and desensitization therapies can shorten waitlist times without increasing posttransplant rejection or mortality rates. The ideal heart-lung donor tends to be younger than other multiorgan transplants, and more tolerant to HLA mismatch, but ideally requires donors with no prior history of smoking, a short period of time on mechanical ventilation, adequate oxygenation and absence of pulmonary infection. The ideal heart-liver donor is often driven by criteria specific to the donor heart. Finally, several observational studies suggest that livers are more tolerant to HLA mismatch than other organs, and offer some degree of immune protection in combined organ transplants.

SUMMARY

Multiorgan transplantation is a steadily growing field. The required short ischemic time for the donor heart is often the limiting factor, as well as the scarcity of appropriate donors available within geographical confines. In general, as with single organ transplantation, younger age, size matching, few medical comorbidities and HLA compatibility confer the best posttransplant outcomes.

Donor selection for lung transplant in Turkey: Is it necessary to wait for an ideal donor?

Background

The aim of this study was to evaluate the donor criteria used in lung transplantation in our clinic.

Methods

A total of 55 cadaveric donors who were accepted for lung transplantation in our clinic between December 2016 and January 2019 were retrospectively analyzed according to ideal donor criteria. The donors were divided into two groups as ideal and non-ideal ones according to their age, partial pressure of oxygen in arterial blood, history of smoking, and ventilation day. Donor data, recipient characteristics and survival outcomes were evaluated.

Results

Of 55 donors accepted for lung transplantation, 24 (43.7%) were ideal and 31 (56.3%) were non-ideal donors. The 90-day mortality and one-year survival rates were not significantly different between the two groups. The 90-day mortality was 25% in the ideal group and 22.6% in the non-ideal group (p=0.834). The one-year survival rates after lung transplantation were 64.5% versus 70.6% in the ideal and non-ideal groups, respectively (p=0.444).

Conclusion

The whole clinical picture should be evaluated before accepting or rejecting donors for lung transplantation. The use of lung donors that do not meet the ideal criteria does not impair short- and mid-term results, compared to ideal lung donors. Strict implementation of donor criteria may prevent using suitable donors for lung transplantation. Use of non-ideal donors can reduce waiting list mortality.

Chest X-ray Sizing for Lung Transplants Reflects Pulmonary Diagnosis and Body Composition and Is Associated With Primary Graft Dysfunction Risk

BACKGROUND

Donor-recipient oversizing based on predicted total lung capacity (pTLC) is associated with a reduced risk of primary graft dysfunction (PGD) following lung transplant but the effect varies with the recipient's diagnosis. Chest x-ray (CXR) measurements to estimate actual total lung capacity (TLC) could account for disease-related lung volume changes, but their role in size matching is unknown.

METHODS

We reviewed adult double lung transplant recipients 2007-2016 and measured apex-to-costophrenic-angle distance (=lung height) on pretransplant donor and recipient CXRs (oversized donor-recipient ratio >1; undersized ≤1]. We tested the relationship between recipient lung height to actual TLC; between lung height ratio and donor/recipient characteristics; and between both lung height ratio or pTLC ratio and grade 3 PGD with logistic regression.

RESULTS

Two hundred six patients were included and 32 (16%) developed grade 3 PGD at 48 or 72 hours. Recipient lung height was related to TLC (r2=0.7297). Pulmonary diagnosis, donor BMI, and recipient BMI were the major determinants of lung height ratio (AUC 0.9036). Lung height ratio oversizing was associated with increased risk of grade 3 PGD (odds ratio, 2.51; 95% confidence interval, 1.17-5.47; P = 0.0182) in this cohort, while pTLC ratio oversizing was not.

CONCLUSIONS

CXR lung height estimates actual TLC and reflects pulmonary diagnosis and body composition. Oversizing via CXR lung height ratio increased PGD risk moreso than pTLC-based oversizing in our cohort.

Bioengineering of Pulmonary Epithelium With Preservation of the Vascular Niche

The shortage of transplantable donor organs directly affects patients with end-stage lung disease, for which transplantation remains the only definitive treatment. With the current acceptance rate of donor lungs of only 20%, rescuing even one half of the rejected donor lungs would increase the number of transplantable lungs threefold, to 60%. We review recent advances in lung bioengineering that have potential to repair the epithelial and vascular compartments of the lung. Our focus is on the long-term support and recovery of the lung ex vivo, and the replacement of defective epithelium with healthy therapeutic cells. To this end, we first review the roles of the lung epithelium and vasculature, with focus on the alveolar-capillary membrane, and then discuss the available and emerging technologies for ex vivo bioengineering of the lung by decellularization and recellularization. While there have been many meritorious advances in these technologies for recovering marginal quality lungs to the levels needed to meet the standards for transplantation – many challenges remain, motivating further studies of the extended ex vivo support and interventions in the lung. We propose that the repair of injured epithelium with preservation of quiescent vasculature will be critical for the immediate blood supply to the lung and the lung survival and function following transplantation.

Systematic review on the treatment of deceased organ donors

BACKGROUND

Currently, there is no consensus on which treatments should be a part of standard deceased-donor management to improve graft quality and transplantation outcomes. The objective of this systematic review was to evaluate the effects of treatments of the deceased, solid-organ donor on graft function and survival after transplantation.

METHODS

Pubmed, Embase, Cochrane, and Clinicaltrials.gov were systematically searched for randomized controlled trials that compared deceased-donor treatment versus placebo or no treatment.

RESULTS

A total of 33 studies were selected for this systematic review. Eleven studies were included for meta-analyses on three different treatment strategies. The meta-analysis on methylprednisolone treatment in liver donors (two studies, 183 participants) showed no effect of the treatment on rates of acute rejection. The meta-analysis on antidiuretic hormone treatment in kidney donors (two studies, 222 participants) indicates no benefit in the prevention of delayed graft function. The remaining meta-analyses (seven studies, 334 participants) compared the effects of 10 min of ischaemic preconditioning on outcomes after liver transplantation and showed that ischaemic preconditioning improved short-term liver function, but not long-term transplant outcomes.

CONCLUSIONS

There is currently insufficient evidence to conclude that any particular drug treatment or any intervention in the deceased donor improves long-term graft or patient survival after transplantation.

Mechanical ventilatory support in potential lung donor patients

Lung transplantation reduces mortality in patients with end-stage lung disease; however, only approximately 21% of lungs from potential donor patients undergo transplantation. A large number of donor lungs become categorized as unsuitable for lung transplantation as a result of lung injury around the time of brain death. Limiting this injury is key to increasing the number of successful lung procurements and subsequent transplants. This narrative review by a working group of pulmonologists, respiratory therapists, and lung transplant specialists elucidates principles of mechanical ventilatory support that can be used to limit lung injury in potential lung donor patients and examines the implementation of protocolized strategies in enhancing the procurement of donor lungs for transplantation.

Lung donor selection criteria

The criteria that define acceptable physiologic and social parameters for lung donation have remained constant since their empiric determination in the 1980s. These criteria include a donor age between 25-40, a arterial partial pressure of oxygen (PaO2)/FiO2 ratio greater than 350, no smoking history, a clear chest X-ray, clean bronchoscopy, and a minimal ischemic time. Due to the paucity of organ donors, and the increasing number of patients requiring lung transplant, finding a donor that meets all of these criteria is quite rare. As such, many transplants have been performed where the donor does not meet these stringent criteria. Over the last decade, numerous reports have been published examining the effects of individual acceptance criteria on lung transplant survival and graft function. These studies suggest that there is little impact of the historical criteria on either short or long term outcomes. For age, donors should be within 18 to 64 years old. Gender may relay benefit to all female recipients especially in male to female transplants, although results are mixed in these studies. Race matched donor/recipients have improved outcomes and African American donors convey worse prognosis. Smoking donors may decrease recipient survival post transplant, but provide a life saving opportunity for recipients that may otherwise remain on the transplant waiting list. No specific gram stain or bronchoscopic findings are reflected in recipient outcomes. Chest radiographs are a poor indicator of lung donor function and should not adversely affect organ usage aside for concerns over malignancy. Ischemic time greater than six hours has no documented adverse effects on recipient mortality and should not limit donor retrieval distances. Brain dead donors and deceased donors have equivalent prognosis. Initial PaO2/FiO2 ratios less than 300 should not dissuade donor organ usage, although recruitment techniques should be implemented with intent to transplant.

Critical care of the potential organ donor

Organ transplantation represents one of the great success stories of 20th century medicine. However, its continued success is greatly limited by the shortage of donor organs. This has led to an increased focus within the critical care community on optimal identification and management of the potential organ donor. The multi-organ donor can represent one of the most complex intensive care patients, with numerous competing physiological priorities. However, appropriate management of the donor not only increases the number of organs that can be successfully donated but has long-term implications for the outcomes of multiple recipients. This review outlines current understandings of the physiological derangements seen in the organ donor and evaluates the available evidence for management strategies designed to optimize donation potential and organ recovery. Finally, emerging management strategies for the potential donor are discussed within the current ethical and legal frameworks permitting donation after both brain and circulatory death.

Endogenous lung regeneration: potential and limitations

The exploration of the endogenous regenerative potential of the diseased adult human lung represents an innovative and exciting task. In this pulmonary perspective, we discuss three major components essential for endogenous lung repair and regeneration: epithelial progenitor populations, developmental signaling pathways that regulate their reparative and regenerative potential, and the surrounding extracellular matrix in the human diseased lung. Over the past years, several distinct epithelial progenitor populations have been discovered within the lung, all of which most likely respond to different injuries by varying degrees. It has become evident that several progenitor populations are mutually involved in maintenance and repair, which is highly regulated by developmental pathways, such as Wnt or Notch signaling. Third, endogenous progenitor cells and developmental signaling pathways act in close spatiotemporal synergy with the extracellular matrix. These three components define and refine the highly dynamic microenvironment of the lung, which is altered in a disease-specific fashion in several chronic lung diseases. The search for the right mixture to induce efficient and controlled repair and regeneration of the diseased lung is ongoing and will open completely novel avenues for the treatment of patients with chronic lung disease.

Donor evaluation for lung transplantation in Korea

Lung transplantation for end-stage lung disease results in prolonged survival and improved pulmonary function. However, the shortage of donor lungs has been a major limiting factor in Korea. We sought to investigate the number and utilization of donor lungs by the five institutions performing LTx in Korea, retrospectively reviewing outcomes of organs registered in the Korean Network for Organ Sharing from January to December, 2010. Lungs were offered from 270 brain-dead patients (189 males and 81 females) of mean age of 45.2 ± 14.2 years (range, 12 to 77 years). The most common cause of brain death was hemorrhage (n = 219, 81%). Only 18 (6.7%) donor lungs were used, which was low compared with kidney (93.3%), liver (86.3%), heart (26.7%), and pancreas (11.1%) use. The mean age of donors of transplanted lungs was 35.7 years (range, 14 to 51 years) compared with 45.9 years for other organs (P = .003). The characteristics of utilized donor lungs were: mean partial pressure of oxygen (PaO(2)), 300.9 mm Hg; mean smoking history, as 2.7 pack-years; and mean body mass index, 21.2 kg/m(2). The causes of refusal were medical ineligibility (n = 129) including poor PaO(2), abnormal chest x-ray, long smoking history, older age (n = 46), no properly matched recipient (n = 46), unknown (n = 17), and family withdrawal (n = 14). Only 8 (33.3%) were transplanted from standard criteria and 10 from the lungs that did not satisfy these criteria. An efficient utilization system is needed to improve lung transplantations.

[Organ protective intensive care treatment and simulation-based training]

In Germany the extent of organ donation is still inadequate and not sufficient to address patients on the waiting lists. Nevertheless, intensive care treatment of potential organ donors does not receive adequate attention. However, because of the increasing age and comorbidities of organ donors in recent years, a sufficient intensive care treatment is indispensable for the success of organ transplantations. Sufficient randomized clinical trials are lacking. This article reviews the current literature and describes approaches for improvement. Multicentre studies and education of medical staff of intensive care units, for example in intensive care simulation for organ protection, could potentially be a successful approach. The improvement and establishment of curricular training and education particularly in simulation workshops might be a promising approach to enhance the quantity and quality of organ donations.

Management of the heartbeating brain-dead organ donor

The main factor limiting organ donation is the availability of suitable donors and organs. Currently, most transplants follow multiple organ retrieval from heartbeating brain-dead organ donors. However, brain death is often associated with marked physiological instability, which, if not managed, can lead to deterioration in organ function before retrieval. In some cases, this prevents successful donation. There is increasing evidence that moderation of these pathophysiological changes by active management in Intensive Care maintains organ function, thereby increasing the number and functional quality of organs available for transplantation. This strategy of active donor management requires an alteration of philosophy and therapy on the part of the intensive care unit clinicians and has significant resource implications if it is to be delivered reliably and safely. Despite increasing consensus over donor management protocols, many of their components have not yet been subjected to controlled evaluation. Hence the optimal combinations of treatment goals, monitoring, and specific therapies have not yet been fully defined. More research into the component techniques is needed.

Brain death and its implications for management of the potential organ donor

The systemic physiologic changes that occur during and after brain death affect all organs suitable for transplantation. Major changes occur in the cardiovascular, pulmonary, endocrine, and immunological systems, and, if untreated may soon result in cardiovascular collapse and somatic death. Understanding these complex physiologic changes is mandatory for developing effective strategies for donor resuscitation and management in such a way that the functional integrity of potentially transplantable organs is maintained. This review elucidates these physiological changes and their consequences, and based on these consequences the rationale behind current medical management of brain-dead organ donors is discussed.