Special issues in the management and selection of the donor for lung transplantation

A systematic review and meta-analysis of coronary artery disease and revascularization in lung transplant patients

Coronary artery disease (CAD) is common in candidates for lung transplantation (LTx) and has historically been considered a relative contraindication to transplantation. We look to review the outcomes of LTx in patients with CAD and determine the optimum revascularization strategy in LTx candidates. PubMed, Medline and Web of Science were systematically searched by three authors for articles comparing the outcomes of LTx in patients with CAD and receiving coronary revascularization. In total 1668 articles were screened and 12 were included in this review.Preexisting CAD in LTx recipients was not associated with significantly increased postoperative morbidity or mortality. The pooled estimates of mortality rate at 1, 3 and 5 years indicated significantly inferior survival in LTx recipients with a prior history of coronary artery bypass grafting (CABG) [odds ratio (OR), 1.84; 95% confidence interval (CI), 1.53-2.22; P < 0.00001; I2 = 0%; OR, 1.52; 95% CI, 1.21-1.91; P = 0.0003; I2 = 0%; OR, 1.62; 95% CI, 1.13-2.33; P = 0.008; I2 = 71%, respectively). However, contemporary literature suggests that survival rates in LTx recipients with CAD that received revascularization either by percutaneous coronary intervention (PCI), previous or concomitant CABG, are similar to patients who did not receive revascularization. Trends in postoperative morbidity favored CABG in the rates of myocardial infarction and repeat revascularization, whereas rates of stroke favored PCI. The composite results of this study support the consideration of patients with CAD or previous coronary revascularization for LTx. Prospective, randomized controlled trials with consistent patient populations and outcomes reporting are required to fully elucidate the optimum revascularization strategy in LTx candidates.

Point-of-care blood gas analyzers have an impact on the acceptance of donor lungs for transplantation

An organ donor PaO2 above 40 kPa is generally required for lung transplantation. Point-of-care (POC) blood gas analyzers are commonly used by organ procurement organizations (OPO) but may underestimate the PaO2 at high levels. We hypothesized that changing to a more accurate blood gas analyzer would result in additional lungs transplanted. All PaO2 measurements on organ donors managed at one OPO's recovery center were performed on an i-STAT POC analyzer prior to October 2015, and on a GEM 4000 subsequently. For 24 weeks, all blood gases were tested simultaneously on both analyzers. We compared lung outcomes of 147 donors in the year prior to this change (using the i-STAT) with 56 donors in the 24-week study period (using the GEM 4000 for lung allocation). When the PaO2 was above 40 kPa, the i-STAT PaO2 was 7.2 kPa lower on average than the GEM 4000. When the GEM PaO2 measured between 40 and 50 kPa, the corresponding i-STAT PaO2 value registered less than 40 kPa 25 out of 48 times (52%), with an average difference of 7.3 kPa (SD = 2.9). The rate of lungs transplanted using the GEM 4000 was 48% compared with 35% in the year prior using the i-STAT (p = .11), with equivalent recipient outcomes. The i-STAT analyzer underestimated the PaO2 above 40 kPa and changing to a more accurate PaO2 analyzer may increase lungs transplanted.

Applications of Out of Body Lung Perfusion

RATIONALE AND OBJECTIVES

Out of body organ perfusion is a concept that has been around for a long time. As technology has evolved, so have the systems available for out of body perfusion making whole organ preservation for extended evaluation, resuscitation, and discovery routine.

MATERIALS AND METHODS

Clinical use of ex vivo lung perfusion (EVLP) systems has continued to expand as evidence has accumulated to suggest EVLP transplants experience similar mortality, ICU length of stay, length of mechanical ventilation, hospital length of stay, and rates of primary graft dysfunction as conventional lung transplants. In 2017, more lung transplants were performed than any previous year in the US history.

RESULTS

Early success of EVLP has motivated groups to evaluate additional donor types and methods for expanding the donor pool. The ability to keep a lung alive in a physiologically neutral environment opens the ability to better understand organ quality, define pathophysiology in certain disease conditions, and provides a platform for interventions to prevent or repair injury.

CONCLUSION

The next several years will usher in significant changes in understanding and interventions focused on lung injury. This manuscript highlights applications of EVLP to clarify how this system can be used for basic and translational research.

Critical Care before Lung Transplantation

Lung transplantation is widely accepted as the only viable treatment option for patients with end-stage lung disease. However, the imbalance between the number of suitable donor lungs available and the number of possible candidates often results in intensive care unit (ICU) admission for the latter. In the ICU setting, critical care is essential to keep these patients alive and to successfully bridge to lung transplantation. Proper management in the ICU is also one of the key factors supporting long-term success following transplantation. Critical care includes the provision of respiratory support such as mechanical ventilation (MV) and extracorporeal life support (ECLS). Accordingly, a working knowledge of the common critical care issues related to these unique patients and the early recognition and management of problems that arise before and after transplantation in the ICU setting are crucial for long-term success. In this review, we discuss the management and selection of candidates for lung transplantation as well as existing respiratory support strategies that involve MV and ECLS in the ICU setting.

Human immunology studies using organ donors: Impact of clinical variations on immune parameters in tissues and circulation

Organ donors are sources of physiologically healthy organs and tissues for life-saving transplantation, and have been recently used for human immunology studies which are typically confined to the sampling of peripheral blood. Donors comprise a diverse population with different causes of death and clinical outcomes during hospitalization, and the effects of such variations on immune parameters in blood and tissues are not known. We present here a coordinate analysis of innate and adaptive immune components in blood, lymphoid (bone marrow, spleen, lymph nodes), and mucosal (lungs, intestines) sites from a population of brain-dead organ donors (2 months-93 years; n = 291) across eight clinical parameters. Overall, the blood of donors exhibited similar monocyte and lymphocyte content and low serum levels of pro-inflammatory cytokines as healthy controls; however, donor blood had increased neutrophils and serum levels of IL-8, IL-6, and MCP-1 which varied with cause of death. In tissues, the frequency and composition of monocytes, neutrophils, B lymphocytes and T cell subsets in lymphoid or mucosal sites did not vary with clinical state, and was similar in donors independent of the extent of clinical complications. Our results reveal that organ donors maintain tissue homeostasis, and are a valuable resource for fundamental studies in human immunology.

Primary Graft Dysfunction After Lung Transplantation

Primary graft dysfunction is a form of acute injury after lung transplantation that is associated with significant short- and long-term morbidity and mortality. Multiple mechanisms contribute to the pathogenesis of primary graft dysfunction, including ischemia reperfusion injury, epithelial cell death, endothelial cell dysfunction, innate immune activation, oxidative stress, and release of inflammatory cytokines and chemokines. This article reviews the epidemiology, pathogenesis, risk factors, prevention, and treatment of primary graft dysfunction.

Worldwide trends in heart and lung transplantation: Guarding the most precious gift ever

Transplantation is sadly a therapy to die for. The survival of a recipient with end-stage heart or lung disease requires the demise of a human being through brain death or cessation of circulation, with the noblest final act of offering one's organs to another. However, transplantation is constrained by severe hemodynamic, regulatory, inflammatory, and metabolic stresses in the donor, rendering the majority of offered organs unsuitable for transplantation. Coupled with our inability to acquire exact molecular and cellular information and missed opportunities for effectively modulating deteriorations of donors and allografts, anesthesia and critical care contributes to ongoing organ shortages. Progress is made with improving waiting lists by bridging patients for transplantation using mechanical support. However, this represents more complex recipients, higher risk transplant operations, and increased resource utilization. The advent of ex vivo perfusion allows implementing novel diagnostic and therapeutic strategies with real potential of reconditioning less ideal organs. This review advocates a paradigm change in critical care management of the potential donor for improving retrieval practices and for more intellectual involvement of our specialties in organ preservation, ex vivo evaluation and reconditioning, and the need for great advancement in our efficiency in converting unacceptable allografts to suitable donor organs.

Massive donor transfusion potentially increases recipient mortality after lung transplantation

OBJECTIVE

Donor blood transfusion has been identified as a potential risk factor for primary graft dysfunction and by extension early mortality. We sought to define the contributing risk of donor transfusion on early mortality for lung transplant.

METHODS

Donor and recipient data were abstracted from the Organ Procurement and Transplantation Network database updated through June 30, 2014, which included 86,398 potential donors and 16,255 transplants. Using the United Network for Organ Sharing 4-level designation of transfusion (no blood, 1-5 units, 6-10 units, and >10 units, massive), we analyzed all-cause mortality at 30-days with the use of logistic regression adjusted for confounders (ischemic time, donor age, recipient diagnosis, lung allocation score and recipient age, and recipient body mass index). Secondary analyses assessed 90-day and 1-year mortality and hospital length of stay.

RESULTS

Of the 16,255 recipients transplanted, 8835 (54.35%) donors received at least one transfusion. Among those transfused, 1016 (6.25%) received a massive transfusion, defined as >10 units. Those donors with massive transfusion were most commonly young trauma patients. After adjustment for confounding variables, donor massive transfusion was associated significantly with an increased risk in 30-day (P = .03) and 90-day recipient mortality (P = .01) but not 1-year mortality (P = .09). There was no significant difference in recipient length of stay or hospital-free days with respect to donor transfusion.

CONCLUSIONS

Massive donor blood transfusion (>10 units) was associated with early recipient mortality after lung transplantation. Conversely, submassive donor transfusion was not associated with increased recipient mortality. The mechanism of increased early mortality in recipients of lungs from massively transfused donors is unclear and needs further study but is consistent with excess mortality seen with primary graft dysfunction in the first 90 days posttransplant.

Lung Ultrasound Utility in the Management of the Neurologically Deceased Organ Donor

CONTEXT

Lung transplantation is limited by donor lung availability with ∼20% of deceased donor lungs transplanted. Diagnostic testing identifying pulmonary derangements guide donor management strategies to maximize lung transplantation. Lung ultrasound (LUS) identifies pathology in critically ill patients equivalent or superior to chest radiograph (CXR) or computed tomography (CT) scans. No published studies have reported on LUS in neurologically deceased donors (DNDDs).

OBJECTIVE

We evaluated LUS in identifying abnormal lung pathology in DNDDs and related these findings to the standard approach.

DESIGN

Prospective pilot study.

SETTING

Intensive care units, university-associated teaching hospital.

PARTICIPANTS

Six DNDDs evaluated during donor management.

INTERVENTIONS

Deceased donors were enrolled based on the availability of ultrasound operators (USOs). Bedside LUS was performed using Lichtenstein 3- or Volpicelli 4-zone method based on the operator preference. Lungs were evaluated for sliding, A/B profile, consolidation, or pleural fluid. Ultrasound operators were blinded to donor management data. Lung ultrasound interpretations were compared for interindividual variability. Ultrasound and anteroposterior portable CXR (AP-CXR) results were compared by Organ Procurement Organization medical directors.

MEASUREMENTS AND MAIN RESULTS

Bedside LUS compared well to AP-CXRs during donor management. There was no interindividual variability noted among USOs. Lung ultrasound identified all findings on AP-CXR and additional clinical pathology not reported on AP-CXR. Reports on AP-CXRs took a median 202 (13-696) minutes to occur, with LUS results available immediately.

CONCLUSIONS

Lung ultrasound may play a significant role in donor management providing real-time clinical data, allowing for rapid identification of abnormalities, and leading to management interventions that may increase the number of transplanted lungs.

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.

Use of lung allografts from brain-dead donors after cardiopulmonary arrest and resuscitation

RATIONALE

Patients who progress to brain death after resuscitation from cardiac arrest have been hypothesized to represent an underused source of potential organ donors; however, there is a paucity of data regarding the viability of lung allografts after a period of cardiac arrest in the donor.

OBJECTIVES

To analyze postoperative complications and survival after lung transplant from brain-dead donors resuscitated after cardiac arrest.

METHODS

The United Network for Organ Sharing database records donors with cardiac arrest occurring after brain death. Adult recipients of lung allografts from these arrest/resuscitation donors between 2005 and 2011 were compared with nonarrest donors. Propensity score matching was used to reduce the effect of confounding. Postoperative complications and overall survival were assessed using McNemar's test for correlated binary proportions and Kaplan-Meier methods.

MEASUREMENTS AND MAIN RESULTS

A total of 479 lung transplant recipients from arrest/resuscitation donors were 1:1 propensity matched from a cohort of 9,076 control subjects. Baseline characteristics in the 1:1-matched cohort were balanced. There was no significant difference in perioperative mortality, airway dehiscence, dialysis requirement, postoperative length of stay (P ≥ 0.38 for all), or overall survival (P = 0.52). A subanalysis of the donor arrest group demonstrated similar survival when stratified by resuscitation time quartile (P = 0.38).

CONCLUSIONS

There is no evidence of inferior outcomes after lung transplant from brain-dead donors who have had a period of cardiac arrest provided that good lung function is preserved and the donor is otherwise deemed acceptable for transplantation. Potential expansion of the donor pool to include cardiac arrest as the cause of brain death requires further study.

Brain Death: Assessment, Controversy, and Confounding Factors

When brain injury is refractory to aggressive management and is considered nonsurvivable, with loss of consciousness and brain stem reflexes, a brain death protocol may be initiated to determine death according to neurological criteria. Clinical evaluation typically entails 2 consecutive formal neurological examinations to document total loss of consciousness and absence of brain stem reflexes and then apnea testing to evaluate carbon dioxide unresponsiveness within the brain stem. Confounding factors such as use of therapeutic hypothermia, high-dose metabolic suppression, and movements associated with complex spinal reflexes, fasciculations, or cardiogenic ventilator autotriggering may delay initiation or completion of brain death protocols. Neurodiagnostic studies such as 4-vessel cerebral angiography can rapidly document absence of blood flow to the brain and decrease intervals between onset of terminal brain stem herniation and formal declaration of death by neurological criteria. Intracranial pathophysiology leading to brain death must be considered along with clinical assessment, patterns of vital signs, and relevant diagnostic studies.

Early metabolic/cellular-level resuscitation following terminal brain stem herniation: implications for organ transplantation

Patients with terminal brain stem herniation experience global physiological consequences and represent a challenging population in critical care practice as a result of multiple factors. The first factor is severe depression of consciousness, with resulting compromise in airway stability and lung ventilation. Second, with increasing severity of brain trauma, progressive brain edema, mass effect, herniation syndromes, and subsequent distortion/displacement of the brain stem follow. Third, with progression of intracranial pathophysiology to terminal brain stem herniation, multisystem consequences occur, including dysfunction of the hypothalamic-pituitary axis, depletion of stress hormones, and decreased thyroid hormone bioavailability as well as biphasic cardiovascular state. Cardiovascular dysfunction in phase 1 is a hyperdynamic and hypertensive state characterized by elevated systemic vascular resistance and cardiac contractility. Cardiovascular dysfunction in phase 2 is a hypotensive state characterized by decreased systemic vascular resistance and tissue perfusion. Rapid changes along the continuum of hyperperfusion versus hypoperfusion increase risk of end-organ damage, specifically pulmonary dysfunction from hemodynamic stress and high-flow states as well as ischemic changes consequent to low-flow states. A pronounced inflammatory state occurs, affecting pulmonary function and gas exchange and contributing to hemodynamic instability as a result of additional vasodilatation. Coagulopathy also occurs as a result of consumption of clotting factors as well as dilution of clotting factors and platelets consequent to aggressive crystalloid administration. Each consequence of terminal brain stem injury complicates clinical management within this patient demographic. In general, these multisystem consequences are managed with mechanism-based interventions within the context of caring for the donor's organs (liver, kidneys, heart, etc.) after death by neurological criteria. These processes begin far earlier in the continuum of injury, at the moment of terminal brain stem herniation. As such, aggressive, mechanism-based care, including hormonal replacement therapy, becomes clinically appropriate before formal brain death declaration to support cardiopulmonary stability following terminal brain stem herniation.

Coronary revascularization in lung transplant recipients with concomitant coronary artery disease

Coronary artery disease (CAD) is not uncommon among lung transplant candidates. Several small, single-center series have suggested that short-term outcomes are acceptable in selected patients who undergo coronary revascularization prior to, or concomitant with, lung transplantation. Our objective was to evaluate perioperative and intermediate-term outcomes in this patient population at our institution. We performed a retrospective, observational cohort analysis of 898 lung transplant recipients between 1997 and 2010. Pediatric, multivisceral, lobar or repeat transplantations were excluded, resulting in 791 patients for comparative analysis, of which 49 (median age 62, 79.6% bilateral transplant) underwent concurrent coronary artery bypass and 38 (median age 64, 63.2% bilateral transplant) received preoperative percutaneous coronary intervention (PCI). Perioperative mortality, overall unadjusted survival and adjusted hazard ratio for cumulative risk of death were similar among both revascularization groups as well as controls. The rate of postoperative major adverse cardiac events was also similar among groups; however, concurrent coronary artery bypass was associated with longer postoperative length of stay, more time in the intensive care unit and more postoperative days requiring ventilator support. These results suggest that patients with CAD need not be excluded from lung transplantation. Preferential consideration should be given to preoperative PCI when feasible.

Primary graft dysfunction

Primary graft dysfunction (PGD) is a syndrome encompassing a spectrum of mild to severe lung injury that occurs within the first 72 hours after lung transplantation. PGD is characterized by pulmonary edema with diffuse alveolar damage that manifests clinically as progressive hypoxemia with radiographic pulmonary infiltrates. In recent years, new knowledge has been generated on risks and mechanisms of PGD. Following ischemia and reperfusion, inflammatory and immunological injury-repair responses appear to be key controlling mechanisms. In addition, PGD has a significant impact on short- and long-term outcomes; therefore, the choice of donor organ is impacted by this potential adverse consequence. Improved methods of reducing PGD risk and efforts to safely expand the pool are being developed. Ex vivo lung perfusion is a strategy that may improve risk assessment and become a promising platform to implement treatment interventions to prevent PGD. This review details recent updates in the epidemiology, pathophysiology, molecular and genetic biomarkers, and state-of-the-art technical developments affecting PGD.

Early Metabolic/Cellular-Level Resuscitation Following Terminal Brain Stem Herniation

Patients with terminal brain stem herniation experience global physiological consequences and represent a challenging population in critical care practice as a result of multiple factors. The first factor is severe depression of consciousness, with resulting compromise in airway stability and lung ventilation. Second, with increasing severity of brain trauma, progressive brain edema, mass effect, herniation syndromes, and subsequent distortion/displacement of the brain stem follow. Third, with progression of intracranial pathophysiology to terminal brain stem herniation, multisystem consequences occur, including dysfunction of the hypothalamic-pituitary axis, depletion of stress hormones, and decreased thyroid hormone bioavailability as well as biphasic cardiovascular state. Cardiovascular dysfunction in phase 1 is a hyperdynamic and hypertensive state characterized by elevated systemic vascular resistance and cardiac contractility. Cardiovascular dysfunction in phase 2 is a hypotensive state characterized by decreased systemic vascular resistance and tissue perfusion. Rapid changes along the continuum of hyperperfusion versus hypoperfusion increase risk of end-organ damage, specifically pulmonary dysfunction from hemodynamic stress and high-flow states as well as ischemic changes consequent to low-flow states. A pronounced inflammatory state occurs, affecting pulmonary function and gas exchange and contributing to hemodynamic instability as a result of additional vasodilatation. Coagulopathy also occurs as a result of consumption of clotting factors as well as dilution of clotting factors and platelets consequent to aggressive crystalloid administration. Each consequence of terminal brain stem injury complicates clinical management within this patient demographic. In general, these multisystem consequences are managed with mechanism-based interventions within the context of caring for the donor’s organs (liver, kidneys, heart, etc.) after death by neurological criteria. These processes begin far earlier in the continuum of injury, at the moment of terminal brain stem herniation. As such, aggressive, mechanism-based care, including hormonal replacement therapy, becomes clinically appropriate before formal brain death declaration to support cardiopulmonary stability following terminal brain stem herniation.

Critical care management of the lung transplant recipient

Lung transplantation provides the prospect of improved survival and quality of life for patients with end stage lung and pulmonary vascular diseases. Given the severity of illness of such patients at the time of surgery, lung transplant recipients require particular attention in the immediate post-operative period to ensure optimal short-term and long-term outcomes. The management of such patients involves active involvement of a multidisciplinary team versed in common post-operative complications. This review provides an overview of such complications as they pertain to the practitioners caring for post-operative lung transplant recipients. Causes and treatment of conditions affecting early morbidity and mortality in lung transplant recipients will be detailed, including primary graft dysfunction, cardiovascular and surgical complications, and immunologic and infectious issues. Additionally, lung donor management issues and bridging the critically ill potential lung transplant recipient to transplantation will be discussed.