Ex vivo lung perfusion (EVLP) shows promise in ameliorating pretransplant acute lung injury (ALI) and expanding the donor organ pool, but the mechanisms of ex vivo repair remain poorly understood. We aimed to assess the utility of gene expression for characterizing ALI during EVLP. One hundred sixty-nine porcine lung samples were collected in vivo (n = 25), after 0 (n = 11) and 12 (n = 11) hours of cold static preservation (CSP), and after 0 (n = 57), 6 (n = 8), and 12 (n = 57) hours of EVLP, utilizing various ventilation and perfusate strategies. The expression of 53 previously described ALI-related genes was measured and correlated with function and histology. Twenty-eight genes were significantly upregulated and 6 genes downregulated after 12 hours of EVLP. Aggregate gene sets demonstrated differential expression with EVLP (P < .001) but not CSP. Upregulated 28-gene set expression peaked after 6 hours of EVLP, whereas downregulated 6-gene set expression continued to decline after 12 hours. Cellular perfusates demonstrated a greater reduction in downregulated 6-gene set expression vs acellular perfusate (P < .038). Gene set expression correlated with relevant functional and histologic parameters, including P/F ratio (P < .001) and interstitial inflammation (P < .005). Further studies with posttransplant results are warranted to evaluate the clinical significance of this novel molecular approach for assessing organ quality during EVLP.
Normothermic ex vivo lung perfusion (EVLP) allows for assessment and reconditioning of donor lungs. Although a leukocyte filter (LF) is routinely incorporated into the EVLP circuit; its efficacy remains to be determined. Twelve pig lungs were perfused and ventilated ex vivo in a normothermic state for 12 hours. Lungs (n = 3) were allocated to four groups according to perfusate composition and the presence or absence of a LF in the circuit (acellular ± LF, cellular ± LF). Acceptable physiologic lung parameters were achieved during EVLP; however, increased amounts of pro-inflammatory cytokines (TNF-α and IL-6) and leukocytes in the perfusate were observed despite the presence or absence of a LF. Analysis of cells washed off the LF demonstrates that it trapped leukocytes although being ineffective throughout perfusion as it became saturated over 12 hours of EVLP. We conclude that there is no objective evidence to support the routine incorporation of a LF during EVLP as it does not provide further benefit and its removal does not appear to cause harm. The lack of hypothesized benefit to a LF may be because of the saturation of the LF with donor leukocytes, leading to similar amounts of circulating leukocytes still present in the perfusate with and without a LF.
Background One of the most promising applications of liver normothermic machine perfusion (NMP) is the potential to directly assess graft viability and injury. In most NMP studies, perfusate transaminases are utilized as markers of graft injury. Our aim was to further elucidate the metabolism of transaminases by healthy porcine livers during NMP, specifically whether such livers could clear circuit perfusate transaminases. Methods A highly concentrated transaminase solution was prepared from homogenized liver, with an aspartate aminotransferase (AST) level of 107,427 U/L. Three livers in the treatment group were compared to three controls, during 48 hours of NMP. In the treatment group, the circuit perfusate was injected with the transaminase solution to artificially raise the AST level to a target of 7,500 U/L. Perfusate samples were taken at two-hour intervals and analyzed for biochemistry until NMP end. Graft oxygen consumption and vascular parameters were monitored. Results Compared to controls, treated perfusions demonstrated abrupt elevations in transaminase levels (p>0.0001) and lactate dehydrogenase (LDH) (p>0.0001), which decreased over time, but never to control baseline. Liver function, as demonstrated by lactate clearance and oxygen consumption was not different between groups. The treatment group demonstrated a higher portal vein resistance (p = 0.0003), however hepatic artery resistance was similar. Treated livers had higher bile production overall (p<0.0001). Conclusions Addition of high levels of transaminases and LDH to a healthy porcine liver during ex situ perfusion results in progressive clearance of these enzymes, suggesting preserved liver metabolism. Such tolerance tests may provide valuable indicators of prospective graft function.
Normothermic ex vivo lung perfusion (EVLP) is an evolving technology to evaluate function of donor lungs to determine suitability for transplantation. We hypothesize that hypoxic pulmonary vasoconstriction (HPV) during EVLP will provide a more sensitive parameter of lung function to determine donor lung quality for lung transplantation. Eight porcine lungs were procured, and subsequently underwent EVLP with autologous blood and STEEN solution for 10 h. Standard physiologic parameters including dynamic compliance, peak airway pressure, and pulmonary vascular resistance (PVR) remained stable (P = 0.055), mean oxygenation (PO /FiO ) was 400 ± 18 mm Hg on average throughout perfusion. Response to hypoxia resulted in a robust increase in PVR (ΔPVR) up to 4 h of perfusion, however the HPV response then blunted beyond T6 (P < 0.01). The decrease in HPV response inversely correlated to cytokine concentrations of Interleukin-6 and tumor necrosis factor-α (P < 0.01). Despite acceptable lung oxygenation and standard physiologic parameters during 10 h of EVLP, there is a subclinical deterioration of lung function. HPV challenges can be performed during EVLP as a simple and more sensitive index of pulmonary vascular reactivity.
Purpose: Ex vivo heart perfusion (EVHP) has been proposed as a means improving heart preservation and expanding the donor pool. Current clinical EVHP protocols involve preservation in an unloaded and non-working state; however, the impact of this approach on the preservation of donor heart function is unknown. We sought to determine if myocardial load during EVHP impacts the preservation of donor heart function. Methods: Donor porcine hearts were perfused ex vivo in a beating state for 12 hours. Loaded hearts (N= 4) were perfused in a working mode (left atrial pressure= 6 mmHg, heart rate= 100 beats/minute) for the entire EVHP interval. Unloaded hearts (N= 4) were briefly transitioned into a working mode at hours 1 (T1), 5 (T5), and 11 (T11) for metabolic and functional assessments, but were otherwise perfused in a resting mode (left atrial pressure= 0 mmHg). Results: Myocardial function (T11 cardiac index (mL/minute/gram): loaded= 6.9±1.0 vs. unloaded= 2.0±1.2, p= 0.02) and mechanical efficiency (T11: loaded= 11±1 vs. unloaded= 2±1 %, p< 0.01) were better preserved in loaded hearts. Myocardial injury (T11 troponin I (ng/mL): loaded= 11.6±0.4 vs. unloaded= 12.1±0.3, p= 0.39) and edema formation (% weight gain: loaded= 14±8 vs. unloaded= 24±3 %, p= 0.15) did not account for these differences. Free fatty acids were rapidly depleted in both groups; however, triglycerides were continually consumed by loaded hearts and secreted by unloaded heats (Figure 1). Conclusion: EVHP in a loaded state improves the preservation of myocardial function. Uncoupling of fatty acid oxidation may contribute to the decline in myocardial function observed in unloaded hearts; however, further research is required to elucidate the mechanism underlying these observations. These results highlight the need for an EVHP device capable of preserving the donor heart in a physiologic working mode. ( 492)Purpose: Testing genetically modified (gm) porcine hearts in ex vivo perfusions with human blood remain as the final test before introducing
Objective: The goal of this manuscript was to report the clinical outcomes of the initial series of 100 consecutive Right Anterior Mini Thoracotomy (RAMT) aortic valve replacement (AVR) implantations at a Canadian Center.Methods: This retrospective study reported the clinical outcomes of the first 100 patients who underwent the RAMT approach for isolated surgical AVR in Calgary, Canada, between 2016 and 2020. Primary outcomes were death within 30 days of surgery and disabling stroke. Secondary outcomes included surgical times, the need for permanent pacemaker (PPM), incidence of postoperative blood transfusion in the intensive care unit (ICU), postsurgical atrial fibrillation (AF), length of ICU/hospital stay, postsurgical AF, residual paravalvular leak (PVL), postoperative transvalvular gradient, need for postsurgical intravenous opioids, duration of invasive ventilation in the ICU, and chest tube output in the first 12 h postsurgery.Results: In this study, 54 patients were male, and the average age of the cohort was 72 years. Mortality within 30 days of surgery was 1% with no disabling postoperative strokes. Mean cardiopulmonary bypass and cross clamp was 84 and 55 min, respectively. PPM rate was 3%, incidence of blood transfusion in the ICU was 4%, and the rate of postoperative AF was 23%. Median length of ICU and hospital stay was 1 and 5 days, respectively. Rate of mild or greater residual PVL was 3%, while the average residual transvalvular mean gradient was 8.5 mmHg. Conclusion:The sternum-sparing RAMT approach can be safely integrated into surgical practice as a minimally invasive alternative for isolated AVR, and can reduce postoperative bleeding and narcotic requirements.
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