A Randomized Controlled Trial of Naloxone for Optimization of Hypoxemia in Lung Donors After Brain Death

A Recruitment Maneuver After Apnea Testing Improves Oxygenation and Reduces Atelectasis in Organ Donors After Brain Death

BACKGROUND

Hypoxemia is the main modifiable factor preventing lungs from being transplanted from organ donors after brain death. One major contributor to impaired oxygenation in patients with brain injury is atelectasis. Apnea testing, an integral component of brain death declaration, promotes atelectasis and can worsen hypoxemia. In this study, we tested whether performing a recruitment maneuver (RM) after apnea testing could mitigate hypoxemia and atelectasis.

METHODS

During the study period, an RM (positive end-expiratory pressure of 15 cm H2O for 15 s then 30 cm H2O for 30 s) was performed immediately after apnea testing. We measured partial pressure of oxygen, arterial (PaO2) before and after RM. The primary outcomes were oxygenation (PaO2 to fraction of inspired oxygen [FiO2] ratio) and the severity of radiographic atelectasis (proportion of lung without aeration on computed tomography scans after brain death, quantified using an image analysis algorithm) in those who became organ donors. Outcomes in RM patients were compared with control patients undergoing apnea testing without RM in the previous 2 years.

RESULTS

Recruitment maneuver was performed in 54 patients after apnea testing, with a median immediate increase in PaO2 of 63 mm Hg (interquartile range 0-109, p = 0.07). Eighteen RM cases resulted in hypotension, but none were life-threatening. Of this cohort, 37 patients became organ donors, compared with 37 donors who had apnea testing without RM. The PaO2:FiO2 ratio was higher in the RM group (355 ± 129 vs. 288 ± 127, p = 0.03), and fewer had hypoxemia (PaO2:FiO2 ratio < 300 mm Hg, 22% vs. 57%; p = 0.04) at the start of donor management. The RM group showed less radiographic atelectasis (median 6% vs. 13%, p = 0.045). Although there was no difference in lungs transplanted (35% vs. 24%, p = 0.44), both better oxygenation and less atelectasis were associated with a higher likelihood of lungs being transplanted.

CONCLUSIONS

Recruitment maneuver after apnea testing reduces hypoxemia and atelectasis in organ donors after brain death. This effect may translate into more lungs being transplanted.

The 20-year paradigm shift toward organ recovery centers: 2500 donors at Mid-America Transplant and broader adoption across the United States

On March 1, 2001, Mid-America Transplant, the organ procurement organization (OPO) located in St Louis, Missouri, performed the first organ recovery of a brain-dead donor in a hospital-independent, free-standing, organ recovery center (ORC), with successful transplantation of a liver. This was the inception of a paradigm shift in donor management and organ procurement, moving away from the traditional method of using the donor hospital. In the last 20 years, many advances have occurred in the ORC. Brain-dead donors are moved within hours of authorization to fully equipped intensive care units. Some ORCs are equipped with computed tomography scanners, portable radiography, laboratory facilities, bronchoscopy, and a cardiac catheterization laboratory. ORCs have dedicated surgical suites, and operating time is frequently during the day and is rarely delayed. Donor management in an ORC is more consistent, efficient, and effective than that in a donor hospital, and studies have demonstrated increased organ yield. Multiple studies have demonstrated a cost benefit of an ORC as well as providing an ideal environment for donor research studies. Currently, there are 24 of 57 OPOs that are using an independent or hospital-based ORC to manage their donors. We review the history and describe the current state of ORCs.

Centralized Organ Recovery and Reconditioning Centers

An increased focus on improving efficiency and decreasing costs has resulted in alternative models of donor management and organ recovery. The specialized donor care facility model provides highly efficient and cost-effective donor care at a free-standing facility, resulting in improved organ yield, shorter ischemic times, decreased travel, and fewer nighttime operations. Ex vivo lung perfusion (EVLP) improves utilization of extended criteria donor lungs, and centralized EVLP facilities have the potential to increase transplant volumes for smaller transplant programs in specified geographic regions. These alternative models are increasingly being used in the United States to improve waitlist mortality and combat the ongoing donor organ shortage.

A multicenter randomized placebo-controlled trial of intravenous thyroxine for heart-eligible brain-dead organ donors

Background

Brain death frequently induces hemodynamic instability and cardiac stunning. Impairments in cardiac performance are major contributors to hearts from otherwise eligible organ donors not being transplanted. Deficiencies in pituitary hormones (including thyroid-stimulating hormone) may contribute to hemodynamic instability, and replacement of thyroid hormone has been proposed as a means of improving stability and increasing hearts available for transplantation. Intravenous thyroxine is commonly used in donor management. However, small controlled trials have not been able to demonstrate efficacy.

Methods

This multicenter study will involve organ procurement organizations (OPOs) across the country. A total of 800 heart-eligible brain-dead organ donors who require vasopressor support will be randomly assigned to intravenous thyroxine for at least 12 h or saline placebo. The primary study hypotheses are that thyroxine treatment will result in a higher proportion of hearts transplanted and that these hearts will have non-inferior function to hearts not treated with thyroxine. Additional outcome measures are the time to achieve hemodynamic stability (weaning off vasopressors) and improvement in cardiac ejection fraction on echocardiography.

Discussion

This will be the largest randomized controlled study to evaluate the efficacy of thyroid hormone treatment in organ donor management. By collaborating across multiple OPOs, it will be able to enroll an adequate number of donors and be powered to definitively answer the critical question of whether intravenous thyroxine treatment increases hearts transplanted and/or provides hemodynamic benefits for donor management.

Trial registration

ClinicalTrials.govNCT04415658. Registered on June 4, 2020

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05797-2.

Outcome measures in solid organ donor management research: a systematic review

AIM

We systematically reviewed published outcome measures across randomised controlled trials (RCTs) of donor management interventions.

METHODS

The systematic review was conducted in accordance with recommendations by the Cochrane Handbook and Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. We searched MEDLINE, Embase, CENTRAL, Web of Science, and trial databases from 1980 to February 2021 for RCTs of donor management interventions.

RESULTS

Twenty-two RCTs (n=3432 donors) were included in our analysis. Fourteen RCTs (63.6%) reported a primary outcome relating to a single organ only. Eight RCTs primarily focused on aspects of donor optimisation in critical care. Thyroid hormones and methylprednisolone were the most commonly evaluated interventions (five and four studies, respectively). Only two studies, focusing on single organs (e.g. kidney), evaluated outcomes relating to other organs. The majority of studies evaluated physiological or biomarker-related outcomes. No study evaluated recipient health-related quality of life. Only one study sought consent from potential organ recipients.

CONCLUSIONS

The majority of RCTs evaluating donor management interventions only assessed single-organ outcomes or effects on donor stability in critical care. There is a need for an evaluation of patient-centred recipient outcomes and standardisation and reporting of outcome measures for future donor management RCTs.

Specialized Donor Care Facility Model and Advances in Management of Thoracic Organ Donors

BACKGROUND

Donor hearts and lungs are more susceptible to the inflammatory physiologic changes that occur after brain death. Prior investigations have shown that protocolized management of potential organ donors can rehabilitate donor organs that are initially deemed unacceptable. In this review we discuss advances in donor management models with particular attention to the specialized donor care facility model. In addition we review specific strategies to optimize donor thoracic organs and improve organ yield in thoracic transplantation.

METHODS

We performed a literature review by searching the PubMed database for medical subject heading terms associated with organ donor management models. We also communicated with our local organ procurement organization to gather published and unpublished information first-hand.

RESULTS

The specialized donor care facility model has been shown to improve the efficiency of organ donor management and procurement while reducing costs and minimizing travel and its associated risks. Lung protective ventilation, recruitment of atelectatic lung, and hormone therapy (eg, glucocorticoids and triiodothyronine/thyroxine) are associated with improved lung utilization rates. Stroke volume-based resuscitation is associated with improved heart utilization rates, whereas studies evaluating hormone therapy (eg, glucocorticoids and triiodothyronine/thyroxine) have shown variable results.

CONCLUSIONS

Lack of high-quality prospective evidence results in conflicting practices across organ procurement organizations, and best practices remain controversial. Future studies should focus on prospective, randomized investigations to evaluate donor management strategies. The specialized donor care facility model fosters a collaborative environment that encourages academic inquiry and is an ideal setting for these investigations.

Ventilation in the prone position improves oxygenation and results in more lungs being transplanted from organ donors with hypoxemia and atelectasis

BACKGROUND

Hypoxemia is the most common barrier to lungs being transplanted from eligible organ donors who are brain dead (BD). Atelectasis is the principal reversible contributing factor to hypoxemia after brain death. We evaluated prospectively whether ventilation in the prone position in donors who are BD would reverse atelectasis, improve oxygenation, and result in more lungs being transplanted.

METHODS

Organ donors managed at the recovery center of 1 organ procurement organization over a 2-year period who exhibited hypoxemia (partial pressure of arterial oxygen [PaO₂]/fraction of inspired oxygen of <300 mm Hg) and had evidence of atelectasis were ventilated in the prone position for 12 hours or longer during donor management. A subset underwent computed tomography (CT) imaging to quantify the degree of atelectasis before and after prone positioning. Outcomes were compared with those of a control group with hypoxemia and atelectasis managed similarly but in the supine position in the previous 2 years.

RESULTS

A total of 40 lung-eligible donors who were BD with hypoxemia and atelectasis were managed in a prone position and compared with 79 donors in supine position. Baseline PaO₂ was similar between the prone and the supine groups (194 ± 78 vs 177 ± 77 mm Hg, p = 0.26) but increased more in the prone group at 4 hours (by 113 vs 54 mm Hg, p = 0.001) and remained 74-mm Hg higher at 12 hours (340 vs 266 mm Hg, p = 0.0006). CT-graded atelectasis was significantly reduced after ventilation in the prone position but persisted in the supine group (p = 0.001). Final PaO₂ was not significantly higher (344 vs 306, p = 0.12), but lungs were more often transplanted in the prone group (45% vs 24%, p = 0.03).

CONCLUSIONS

Ventilation in the prone position reverses atelectasis and rapidly and sustainably improves oxygenation in organ donors who are BD with hypoxemia. This effect appears to translate into more lungs being transplanted.

Therapeutic Hypothermia in Organ Donors: Follow-up and Safety Analysis

BACKGROUND

In a recent trial, targeted mild hypothermia in brain-dead organ donors significantly reduced the incidence of delayed graft function after kidney transplantation. This trial was stopped early for efficacy. Here, we report long-term graft survival for all organs along with donor critical care end points.

METHODS

We assessed graft survival through 1 year of all solid organs transplanted from 370 donors who had been randomly assigned to hypothermia (34-35°C) or normothermia (36.5-37.5°C) before donation. Additionally, changes in standardized critical care end points were compared between donors in each group.

RESULTS

Mild hypothermia was associated with a nonsignificant improvement in 1-year kidney transplant survival (95% versus 92%; hazard ratio, 0.61 [0.31-1.20]; P = 0.15). Mild hypothermia was associated with higher 1-year graft survival in the subgroup of standard criteria donors (97% versus 93%; hazard ratio, 0.39 [0.15 to -1.00]; P = 0.05). There were no significant differences in graft survival of extrarenal organs. There were no differences in critical care end points between groups.

CONCLUSIONS

Mild hypothermia in the donor safely reduced the rate of delayed graft function in kidney transplant recipients without adversely affecting donor physiology or extrarenal graft survival. Kidneys from standard criteria donors who received targeted mild hypothermia had improved 1-year graft survival.

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.

Noteworthy Literature Published in 2018 for Thoracic Organ Transplantation

Publications of note from 2018 are reviewed for the cardiothoracic transplant anesthesiologist. Strategies to expand the availability of donor organs were highlighted, including improved donor management, accumulating experience with increased-risk donors, ex vivo perfusion techniques, and donation after cardiac death. A number of reports examined posttransplant outcomes, including outcomes other than mortality, with new data-driven risk models. Use of extracorporeal support in cardiothoracic transplantation was a prominent theme. Major changes in adult heart allocation criteria were implemented, aiming to improve objectivity and transparency in the listing process. Frailty and prehabilitation emerged as targets of comprehensive perioperative risk mitigation programs.