Heart Donation From Donors After Controlled Circulatory Death

Normothermic Ex Vivo Heart Perfusion With Exosomes From Human Umbilical Cord Mesenchymal Stem Cells Improves Graft Function in Donation After Circulatory Death Hearts

BACKGROUND

This study aimed to investigate the cardioprotective effect of exosomes derived from human umbilical cord mesenchymal stem cells on donation after circulatory death (DCD) hearts preserved with normothermic ex vivo heart perfusion (EVHP) in a rat heart transplantation model.

METHODS

Thirty-two male Lewis rats were divided into 2 groups: the control group and the exosome group. The donor-heart rats were subjected to the DCD procedure by suffering a 15-min warm ischemia injury, subsequently preserved with EVHP for 90 min, and then transplanted into recipients via abdominal heterotopic heart transplantation. Vehicle or exosome was added into the perfusate of normothermic EVHP in the control or exosome group. We evaluated left ventricular graft function, myocardial inflammation, and myocardial apoptosis of the donor heart 1.5 h after heart transplantation. Furthermore, we investigate the alternation of myocardial gene expression in the donor hearts between both groups by transcriptome sequencing.

RESULTS

The treatment with exosome significantly enhanced cardiac function through increasing left ventricular developed pressure, dp/dtmax, and dp/dtmin of DCD hearts at 90 min after heart transplantation compared with the control group. The myocardial cells in the exosome group exhibited an orderly arrangement without obvious edema. Furthermore, exosome added into perfusate in the exosome group significantly attenuated the level of inflammatory response and apoptosis. Transcriptome sequencing and RT-qPCR showed the phosphoinositide 3-kinase/protein kinase B pathway was activated after exosome treatment.

CONCLUSIONS

Normothermic EVHP combined with exosome can be a promising and novel DCD heart preservation strategy, alleviating myocardial ischemia-reperfusion injury in the DCD heart.

Impact of Hemoglobin Level in Ex Vivo Heart Perfusion on Donation After Circulatory Death Hearts: A Juvenile Porcine Experimental Model

BACKGROUND

Ex vivo heart perfusion (EVHP) of donation after circulatory death (DCD) hearts has become an effective strategy in adults; however, the small circulating volume in pediatrics poses the challenge of a low-hemoglobin (Hb) perfusate. We aimed to determine the impact of perfusate Hb levels during EVHP on DCD hearts using a juvenile porcine model.

METHODS

Sixteen DCD piglet hearts (11-14 kg) were reperfused for 4 h in unloaded mode followed by working mode. Metabolism, cardiac function, and cell damage were compared between the low-Hb (Hb, 5.0-5.9 g/dL; n = 8) and control (Hb, 7.5-8.4 g/dL; n = 8) groups. Between-group differences were evaluated using 2-sample t-tests or Fisher's Exact tests.

RESULTS

During unloaded mode, the low-Hb group showed lower myocardial oxygen consumption (P < 0.001), a higher arterial lactate level (P = 0.001), and worse systolic ventricular function (P < 0.001). During working mode, the low-Hb group had a lower cardiac output (mean, 71% versus 106% of normal cardiac output, P = 0.010) and a higher arterial lactate level (P = 0.031). Adjusted cardiac troponin-I (P = 0.112) did not differ between the groups. Morphological myocyte injury in the left ventricle was more severe in the low-Hb group (P = 0.028).

CONCLUSIONS

Low-Hb perfusate with inadequate oxygen delivery induced anaerobic metabolism, resulting in suboptimal DCD heart recovery and declined cardiac function. Arranging an optimal perfusate is crucial to organ protection, and further endeavors to refine the priming volume of EVHP or the transfusion strategy are required.

Outcomes of liver transplantation with thoracoabdominal normothermic regional perfusion: a matched-controlled initial experience in Spain

Thoracoabdominal (TA) normothermic regional perfusion (NRP) should allow the safe recovery of heart and liver grafts simultaneously in the context of controlled donation after circulatory death (cDCD). We present the initial results of cDCD liver transplantation with simultaneous liver and heart procurement in Spain until October 2021. Outcomes were compared with a matched cohort of cDCD with abdominal NRP (A-NRP) from participating institutions. Primary endpoints comprised early allograft dysfunction (EAD) or primary non-function (PNF), and the development of ischemic-type biliary lesions (ITBL). Six transplants were performed using cDCD with TA-NRP during the study period. Donors were significantly younger in the TA-NRP group than in the A-NRP group (median 45.6 years and 62.9 years respectively, p = 0.011), with a median functional warm ischemia time of 12.5 min in the study group and 13 min in the control group. Patient characteristics, procurement times, and surgical baseline characteristics did not differ significantly between groups. No patient in the study group developed EAD or PNF, and over a median follow-up of 9.8 months, none developed ITBL or graft loss. Extending A-NRP to TA-NRP for cardiac procurement may be technically challenging, but it is both feasible and safe, showing comparable postoperative outcomes to A-NRP.

Dilemmas concerning heart procurement in controlled donation after circulatory death

With an expanding population at risk for heart failure and the resulting increase in patients admitted to the waiting list for heart transplantation, the demand of viable organs exceeds the supply of suitable donor hearts. Use of hearts after circulatory death has reduced this deficit. Two primary techniques for heart procurement in circulatory death donors have been described: direct procurement and perfusion and thoraco-abdominal normothermic regional perfusion. While the former has been accepted as an option for heart procurement in circulatory death donors, the latter technique has raised some ethical questions in relation to the dead donor rule. In this paper we discuss the current dilemmas regarding these heart procurement protocols in circulatory death donors.

Anesthetic Considerations of Organ Procurement After Brain and Cardiac Death: A Narrative Review

Organ donation procedures have become more frequent in the US as the need for transplants is increasing. Defining the anesthesiologist's role in organ donations after brain and cardiac death is important, as is understanding its ethics and practical physiologic and perioperative implications. Despite this, there are few papers specifically addressing the anesthetic management of organ donors. This review summarizes the preoperative, intraoperative, and postmortem considerations for the anesthesiologist involved in organ donation after either brain or cardiac death. A search of the published literature was performed using PubMed, Excerpta Medica dataBASE (EMBASE), and Google Scholar in March of 2022 for articles addressing anesthetic considerations of organ procurement surgeries after brain and cardiac death. This review demonstrates that anesthesiologists play a significant role in the organ procurement process. Their role in the perioperative management of the donor may affect the outcomes of organ transplantation. The gap between the number of organs harvested and the number of patients awaiting organ transplantation remains high despite continued efforts to increase the number of available organs. Perioperative management of organ donors aims at counteracting the associated unique physiologic derangements and targets optimization of oxygenation of the organs intended for procurement. Optimizing care after death can help ensure the viability of organs and the best outcomes for recipients. As organ donation after cardiac death (DCD) becomes more frequent in the US, anesthesiologists should be aware of the DCD classifications of donors and emerging novel perfusion techniques.

Clamping of the Aortic Arch Vessels During Normothermic Regional Perfusion Does Not Negatively Affect Donor Cardiac Function in Donation After Circulatory Death

BACKGROUND

The hemodynamic effects of aortic arch vessel (AAV) clamping during normothermic regional perfusion (NRP) in donation after circulatory death is unknown. We investigated effects of AAV clamping during NRP compared with no clamping in a porcine model.

METHODS

In 16 pigs, hemodynamic parameters were recorded including biventricular pressure-volume measurements and invasive blood pressure. Additionally, blood gas parameters and inflammatory cytokines were used to assess the effect of AAV clamping. The animals were centrally cannulated for NRP, and baseline measurements were obtained before hypoxic circulatory arrest was induced by halting mechanical ventilation. During an 8-min asystole period, the animals were randomized to clamp (n = 8) or no-clamp (n = 8) of the AAV before commencement of NRP. During NRP, circulation was supported with norepinephrine (NE) and dobutamine. After 30 min of NRP, animals were weaned and observed for 180 min post-NRP.

RESULTS

All hearts were successfully reanimated and weaned from NRP. The nonclamp groups received significantly more NE to maintain a mean arterial pressure >60 mm Hg during and after NRP compared with the clamp group. There were no between group differences in blood pressure or cardiac output. Pressure-volume measurements demonstrated preserved cardiac function' including ejection fraction and diastolic and systolic function. No between group differences in inflammatory markers were observed.

CONCLUSIONS

AAV clamping did not negatively affect donor cardiac function or inflammation after circulatory death and NRP. Significantly less NE was used to support in the clamp group than in the nonclamp group.

Normothermic Regional Perfusion is an Emerging Cost-Effective Alternative in Donation After Circulatory Death (DCD) in Heart Transplantation

In donation after circulatory death (DCD) organ transplantation, normothermic regional perfusion (NRP) restores oxygenated blood flow following cardiac arrest and reverses warm ischemia. Recently, NRP has also been used to help recover DCD hearts in addition to the abdominal organs. While DCD donation has increased the number of abdominal organs and lungs pool, it has not been able to increase the number of heart transplants, despite the fact that it has the potential to increase the number of heart transplants by 15-30%. Thoracoabdominal normothermic regional perfusion makes heart transplantation feasible and permits assessing heart function before an organ procurement without affecting the preservation of abdominal organs. NRP can be used in two ways for DCD donor heart transplants: normothermic regional perfusion followed by machine perfusion (NRP-MP) and normothermic regional perfusion followed by static cold storage (NRP-SCS). Normothermic regional perfusion is an emerging technology, a cost-effective alternative in donation after circulatory death (DCD), and will increase the pool of donors in heart transplantation.

High Oxygenation During Normothermic Regional Perfusion After Circulatory Death Is Beneficial on Donor Cardiac Function in a Porcine Model

BACKGROUND

Thoracoabdominal normothermic regional perfusion (NRP) is a new method for in situ reperfusion and reanimation of potential donor organs in donation after circulatory death by reperfusion of the thoracic and abdominal organs with oxygenated blood. We investigated effects of high oxygenation (HOX) versus low oxygenation (LOX) during NRP on donor heart function in a porcine model.

METHODS

Pigs (80 kg) underwent a 15-min anoxic cardiac arrest followed by cardiac reanimation on NRP using a heart-lung bypass machine with subsequent assessment 180 minutes post-NRP. The animals were randomized to HOX (FiO2 1.0) or LOX (FiO2 0.21 increased to 0.40 during NRP). Hemodynamic data were obtained by invasive blood pressure and biventricular pressure-volume measurements. Blood gases, biomarkers of inflammation, and oxidative stress were measured.

RESULTS

Eight of 9 animals in the HOX group and 7 of 10 in the LOX group were successfully weaned from NRP. Right ventricular end-systole elastance was significantly improved in the HOX group compared with the LOX group, whereas left ventricular end-systole elastance was preserved at baseline levels. Post-NRP cardiac output, mean arterial, central venous, and pulmonary capillary wedge pressure were all comparable to baseline. Creatinine kinase-MB increased more in the LOX group than the HOX group, whereas proinflammatory cytokines increased more in the HOX group than the LOX group. No difference was found in oxidative stress between groups.

CONCLUSIONS

All hearts weaned from NRP showed acceptable hemodynamic function for transplantation. Hearts exposed to LOX showed more myocardial damage and showed poorer contractile performance than hearts reperfused with high oxygen.

Critical warm ischemia time point for cardiac donation after circulatory death

Donation after circulatory death (DCD) represents a promising opportunity to overcome the relative shortage of donors for heart transplantation. However, the necessary period of warm ischemia is a concern. This study aims to determine the critical warm ischemia time based on in vivo biochemical changes. Sixteen DCD non-cardiac donors, without cardiovascular disease, underwent serial endomyocardial biopsies immediately before withdrawal of life-sustaining therapy (WLST), at circulatory arrest (CA) and every 2 min thereafter. Samples were processed into representative pools to assess calcium homeostasis, mitochondrial function and cellular viability. Compared to baseline, no significant deterioration was observed in any studied parameter at the time of CA (median: 9 min; IQR: 7-13 min; range: 4-19 min). Ten min after CA, phosphorylation of cAMP-dependent protein kinase-A on Thr197 and SERCA2 decreased markedly; and parallelly, mitochondrial complex II and IV activities decreased, and caspase 3/7 activity raised significantly. These results did not differ when donors with higher WLST to CA times (≥9 min) were analyzed separately. In human cardiomyocytes, the period from WLST to CA and the first 10 min after CA were not associated with a significant compromise in cellular function or viability. These findings may help to incorporate DCD into heart transplant programs.

Clamping of the Aortic Arch Vessels During Normothermic Regional Perfusion After Circulatory Death Prevents the Return of Brain Activity in a Porcine Model

BACKGROUND

The cerebral effect of clamping following normothermic regional perfusion (NRP) in donation after circulatory death (DCD) remains unknown. We investigated the effect of cerebral reperfusion during NRP and the preventive effect of clamping on brain function in a porcine model.

METHODS

In 16 pigs, intracranial physiological parameters were recorded, including pressure, cerebral blood perfusion (CBF), temperature, and oxygen. Additionally, electroencephalography (EEG) and somatosensory evoked potentials (SSEPs) were used to assess brain function. The animals were cannulated for the heart-lung machine, and baseline measurements were performed before withdrawal from life support. After 8 min of mechanical asystole, the animals were randomly allocated to clamp (n = 8) or nonclamp (n = 8) of the aortic arch vessels. After 30 min of NRP, the animals were monitored for 3 h after weaning (AW).

RESULTS

Intracranial measurements of CBF, oxygen, and temperature indicated successful occlusion of the arch vessels following NRP and AW in the clamp group versus the nonclamp group. In the clamp group, EEG was isoelectric and SSEPs were absent AW in all pigs. In the nonclamp group, EEG activity was observed in all 8 pigs, whereas SSEPs were observed in 6 of 8 pigs. Additionally, agonal respiratory movements in the form of gasping were observed in 6 of 8 pigs in the nonclamp group.

CONCLUSIONS

Reperfusion of the brain during NRP led to a return of brain activity. Conversely, clamping of the arch vessels halted cerebral circulation, ensuring the permanent cessation of brain function and maintaining the determination of death in DCD.