Pre-arrest heparinization and ventilation during warm ischemia preserves lung function in non-heart-beating donors

Antemortem Heparin in Organ Donation After Circulatory Death Determination: A Systematic Review of the Literature

Donation after circulatory death determination frequently involves antemortem heparin administration to mitigate peri-arrest microvascular thrombosis. We systematically reviewed the literature to: (1) describe heparin administration practices and (2) explore the effects on transplant outcomes. We searched MEDLINE and EMBASE for studies reporting donation after circulatory death determination heparin practices including use, dosage, and timing (objective 1). To explore associations between antemortem heparin and transplant outcomes (objective 2), we (1) summarized within-study comparisons and (2) used meta-regression analyses to examine associations between proportions of donors that received heparin and transplant outcomes. We assessed risk of bias using the Newcastle Ottawa Scale and applied the GRADE methodology to determine certainty in the evidence. For objective 1, among 55 eligible studies, 48 reported heparin administration to at least some donors (range: 15.8%-100%) at variable doses (up to 1000 units/kg) and times relative to withdrawal of life-sustaining therapy. For objective 2, 7 studies that directly compared liver transplants with and without antemortem heparin reported lower rates of primary nonfunction, hepatic artery thrombosis, graft failure at 5 y, or recipient mortality (low certainty of evidence). In contrast, meta-regression analysis of 32 liver transplant studies detected no associations between the proportion of donors that received heparin and rates of early allograft dysfunction, primary nonfunction, hepatic artery thrombosis, biliary ischemia, graft failure, retransplantation, or patient survival (very low certainty of evidence). In conclusion, antemortem heparin practices vary substantially with an uncertain effect on transplant outcomes. Given the controversies surrounding antemortem heparin, clinical trials may be warranted.

Ethical and legal issues related to the donation and use of nonstandard organs for transplants

Transplantation of nonstandard or expanded criteria donor organs creates several potential ethical and legal problems in terms of consent and liability, and new challenges for research and service development; it highlights the need for a system of organ donation that responds to an evolving ethical landscape and incorporates scientific innovation to meet the needs of recipients, but which also safeguards the interests and autonomy of the donor. In this article, the use of deceased donor organs for transplants that fail to meet standard donor criteria and the legitimacy of interventions and research aimed at optimizing their successful donation are discussed.

Retrograde flush is more protective than heparin in the uncontrolled donation after circulatory death lung donor

BACKGROUND

Formation of microthrombi after circulatory arrest is a concern for the development of reperfusion injury in lung recipients from donation after circulatory death (DCD) donors. In this isolated lung reperfusion study, we compared the effect of postmortem heparinization with preharvest retrograde pulmonary flush or both.

METHODS

Domestic pigs (n = 6/group) were sacrificed by ventricular fibrillation and left at room temperature for 1 h. This was followed by 2.5 h of topical cooling. In control group [C], no heparin and no pulmonary flush were administered. In group [R], lungs were flushed with Perfadex in a retrograde way before explantation. In group [H], heparin (300 IU/kg) was administered 10 min after cardiac arrest followed by closed chest massage for 2 min. In the combined group, animals were heparinized and the lungs were explanted after retrograde flush [HR]. The left lung was assessed for 60 min in an ex vivo reperfusion model.

RESULTS

Pulmonary vascular resistance at 50 and 55 min was significantly lower in [R] and [HR] groups compared with [C] and [H] groups (P < 0.01 and P < 0.001) and at 60 min in [R], [H], and [HR] groups compared with [C] group (P < 0.001). Oxygenation, compliance, and plateau airway pressure were more stable in [R] and [HR] groups. Plateau airway pressure was significantly lower in [R] group compared with the [H] group at 60 min (P < 0.05). No significant differences in wet-dry weight ratio were observed between the groups.

CONCLUSIONS

This study suggests that preharvest retrograde flush is more protective than postmortem heparinization to prevent reperfusion injury in lungs recovered from donation after circulatory death donors.

Present state of nonheart-beating lung donation

PURPOSE OF REVIEW

Indications for lung transplantation have increased through the years, and currently we have to face a lack of grafts to attend this growing demand with the subsequent increase in waiting-list deaths. Several strategies have been proposed to solve this challenging problem (living-lobe donors, extended donors, size-reduced lung grafts and so on), the use of nonheart-beating donors (NHBDs) being the most promising of them.

RECENT FINDINGS

The last experimental works concerning NHBDs have focused on the improvement of graft preservation in order to minimize warm ischemic injury and the capacity of noninvasive parameters in bronchial lavage to predict good function after implantation. There have also been several reports on the clinical use of controlled and uncontrolled NHBDs with excellent results.

CONCLUSION

Several methods have been effective in protecting these grafts from ischemic damage. Functional predictors will be very useful in the near future allowing us to know in a simple and noninvasive way which grafts are suitable for transplantation. Definitely, NHBDs for lung transplantation are no more a promising source of grafts but a real one, with encouraging short-term and mid-term results.

Pro/con debate: in patients who are potential candidates for organ donation after cardiac death, starting medications and/or interventions for the sole purpose of making the organs more viable is an acceptable practice

Several hospitals have been developing programmes for organ donation after cardiac death. Such programmes offer options for organ donation to patients who do not meet brain-death criteria but wish to donate their organs after withdrawal of life-support. These programmes also increase the available organ pool at a time when demand exceeds supply. Given that potential donors are managed in intensive care units, intensivists will be key components of these programmes. Donation after cardiac death clearly carries a number of important ethical issues with it. In the present issue of Critical Care two established groups debate the ethical acceptability of using medications/interventions in potential organ donors for the sole purpose of making the organs more viable. Such debates will be an increasingly common component of intensivists' future practice.

Evaluation of techniques for lung transplantation following donation after cardiac death

BACKGROUND

Lung transplantation using "donation after cardiac death" donors is a potential means to alleviate the shortage of suitable donor lungs for transplantation, but the practicality and utility of the various possible techniques need to be clarified.

METHODS

Using a dog model, we explored seven variations of standoff (ischemic) time (50 to 240 minutes), topical cooling (60 to 120 minutes), and flush cooling and cold storage (30 to 140 minutes) to mimic different human donor lung retrieval scenarios that can follow donation after cardiac death. The functional status of donation after cardiac death donor lungs was assessed initially with a 250 mL pulmonary arterial blood flush while ventilating with 100% oxygen and then on an ex-vivo perfusion rig for 120 minutes after retrieval.

RESULTS

All lungs achieved an excellent pO2/FiO2 ratio ranging from 472 to 586 with stable pulmonary artery pressures and pulmonary vascular resistance and no net weight gain (952 +/- 221 g versus 1,006 +/- 235 g) during the 120-minute evaluation period. Initial blood flush correlated well with measured perfusion rig pO2 at 30 minutes (R2 = 0.63).

CONCLUSIONS

This canine study suggests that lungs donated after cardiac death are reproducibly useable for transplantation with ischemic times of as long as 60 minutes. Although more study is needed, a blood flush evaluation is simple and may have a role as a secondary allograft assessment tool. The existing techniques of donor lung evaluation and preservation after donation following cardiac death thus appear both feasible and practical.

Non-heart beating organ donation: overview and future perspectives

New indications for organ transplantation combined with a stagnating number of available donor grafts have severely lengthened the waiting list for almost all types of transplantations. This has led to a renewed interest in non-heart beating (NHB) donation, as a possible solution to bridge the gap between supply and demand. In this review, we present an overview of current NHB donation practice, outcome, existing problems and future perspectives. We focus on possible improvements in donor management, recipient care and new methods of organ preservation that may be better suited for these marginal organs. Successful institution of NHB protocols depends on adapting current transplantation practice at all levels, which is one of the greatest challenges for researchers and professionals in this interesting re-emerging field.

Endobronchial donor pre-treatment with ventavis: is a second administration during reperfusion beneficial to optimize post-ischemic function of non-heart beating donor lungs?

BACKGROUND

Lung retrieval from non-heart-beating donors (NHBD) has been introduced into clinical practice successfully. However, because of potentially deleterious effects of warm ischemia on microvascular integrity, use of NHBD lungs is limited by short tolerable time periods before preservation. Recently, improvement of NHBD graft function was demonstrated by donor pre-treatment using aerosolized Ventavis (Schering Inc., Berlin, Germany). Currently, there is no information whether additional application of this approach in reperfusion can further optimize immediate graft function.

MATERIAL AND METHODS

Asystolic pigs (n = 5/group) were ventilated for 180-min of warm ischemia (groups 1-3). In groups 2 and 3, 100 microg Ventavis were aerosolized over 30-min using an ultrasonic nebulizer (Optineb). Lungs were then retrogradely preserved with Perfadex and stored for 3-h. After left lung transplantation and contralateral lung exclusion, grafts were reperfused for 6-h. Only in group 3, another dose of 100 microg Ventavis was aerosolized during the first 30-min of reperfusion. Hemodynamics, pO2/FiO2 and dynamic compliance were monitored continuously and compared to controls. Intraalveolar edema was quantified stereologically, and extravascular-lung-water-index (EVLWI) was measured. Statistics comprised ANOVA analysis with repeated measurements.

RESULTS

Dynamic compliance was significantly lower in both Ventavis groups, but additional administration did not result in further improvement. Oxygenation, pulmonary hemodynamics, EVLWI and intraalveolar edema formation were comparable between groups.

CONCLUSIONS

Alveolar deposition of Ventavis in NHBD lungs before preservation significantly improves dynamic lung compliance and represents an important strategy for improvement of preservation quality and expansion of warm ischemic intervals. However, additional application of this method in early reperfusion is of no benefit.

Donor pretreatment using the aerosolized prostacyclin analogue iloprost optimizes post-ischemic function of non-heart beating donor lungs

BACKGROUND

Ischemia-reperfusion injury accounts for one-third of early deaths after lung transplantation. To expand the limited donor pool, lung retrieval from non-heart beating donors (NHBD) has been introduced recently. However, because of potentially deleterious effects of warm ischemia on microvascular integrity, use of NHBD lungs is limited by short tolerable time periods before preservation. After intravenous prostanoids are routinely used to ameliorate reperfusion injury, the latest evidence suggests similar efficacy of inhaled prostacyclin. Therefore, the impact of donor pretreatment with the prostacyclin analogue iloprost on postischemic NHBD lung function and preservation quality was evaluated.

METHODS

Asystolic pigs (5 per group) were ventilated for 180 minutes of warm ischemia (Group 2). In Group 3, 100 microg iloprost was aerosolized during the final 30 minutes of ventilation with a novel mobile ultrasonic nebulizer. Lungs were then retrogradely preserved with Perfadex and stored for 3 hours. After left lung transplantation and contralateral lung exclusion, hemodynamics, rO2/FiO2, and dynamic compliance were monitored for 6 hours and compared with sham-operated controls (Group 1). Pulmonary edema was determined both stereologically and by wet-to-dry weight ratio (W/D). Statistics comprised analysis of variance with repeated measures and Mann-Whitney test.

RESULTS

Flush preservation pressures, dynamic compliance, inspiratory pressures, and W/D were significantly superior in iloprost-treated lungs, and oxygenation and pulmonary hemodynamics were comparable between groups. Stereology revealed a trend toward lower intraalveolar edema formation in iloprost-treated lungs compared with untreated grafts.

CONCLUSIONS

Alveolar deposition of Iloprost and NHBD lungs before preservation ameliorates postischemic edema and significantly improves lung compliance. This easily applicable innovation approach, which uses a mobile ultrasonic nebulizer, offers an important strategy for improvement of pulmonary preservation quality and might expand the pool of donor lungs.

Non-heart-beating donors

The widespread application of lung transplantation is limited by the shortage of suitable donor organs resulting in longer waiting times for listed patients with a substantial risk of dying before transplantation. To overcome this critical organ shortage, some transplant programs have now begun to explore the use of lungs from circulation-arrested donors, so called non-heart-beating donors (NHBDs). This review outlines the different categories of NHBDs, the relevant published experimental data that support the use of lungs coming from these donors and the clinical experience worldwide so far. Techniques for NHBD lung preservation and pretransplant functional assessment are reviewed. Ethical issues involved in transplanting lungs from asystolic donors are discussed.

Lung Retrieval from Non-Heart-Beating Donors: First Experience with an Innovative Preservation Strategy in a Pig Lung Transplantation Model

OBJECTIVE

Lung transplantation is limited by the scarcity of donor organs. Lung retrieval from non-heart-beating donors (NHBD) might extend the donor pool and has been reported recently. However, no studies in NHBD exist using the novel approach of retrograde preservation with Perfadex solution.

METHODS

Heparinized asystolic pigs (n = 5, 30-35 kg) were ventilated for 90 min. The lungs were retrogradely preserved with Perfadex solution and stored inflated at 4 degrees C for 3 h. Left lung transplantation in the recipient was followed by exclusion of the right lung. Results were compared to sham-operated animals. Oxygenation, hemodynamics and dynamic compliance were monitored for 4 h. Infiltration of polymorphonuclear cells (PMNs) and stereological quantification of alveolar edema was performed. Statistical analysis comprised Kruskal-Wallis and Mann-Whitney tests and ANOVA analysis with repeated measures.

RESULTS

No mortality was observed. During preservation, continuous elimination of blood clots via the pulmonary artery venting site was observed. Oxygenation and compliance were similar between groups, but sham controls showed significantly lower pulmonary vascular resistance. Stereological quantification revealed higher volume fractions of intra-alveolar edema in NHBD grafts, while PMN infiltration was comparable to sham controls.

CONCLUSIONS

Use of NHBD lungs results in excellent outcome after 90 min of warm ischemia followed by retrograde preservation with Perfadex solution. This novel approach can optimize lung preservation by eliminating clots from the pulmonary circulation and might clinically be considered in brain-dead organ donors who become hemodynamically unstable prior to organ harvest. Further trials with longer warm and cold ischemic periods are necessary to further elucidate this promising approach to donor pool expansion.