Resuscitation of Ischemic Donor Livers with Normothermic Machine Perfusion: A Metabolic Flux Analysis of Treatment in Rats

Normothermic machine perfusion has previously been demonstrated to restore damaged warm ischemic livers to transplantable condition in animal models. However, the mechanisms of recovery are unclear, preventing rational optimization of perfusion systems and slowing clinical translation of machine perfusion. In this study, organ recovery time and major perfusate shortcomings were evaluated using a comprehensive metabolic analysis of organ function in perfusion prior to successful transplantation. Two groups, Fresh livers and livers subjected to 1 hr of warm ischemia (WI) received perfusion for a total preservation time of 6 hrs, followed by successful transplantation. 24 metabolic fluxes were directly measured and 38 stoichiometrically-related fluxes were estimated via a mass balance model of the major pathways of energy metabolism. This analysis revealed stable metabolism in Fresh livers throughout perfusion while identifying two distinct metabolic states in WI livers, separated at t = 2 hrs, coinciding with recovery of oxygen uptake rates to Fresh liver values. This finding strongly suggests successful organ resuscitation within 2 hrs of perfusion. Overall perfused livers regulated metabolism of perfusate substrates according to their metabolic needs, despite supraphysiological levels of some metabolites. This study establishes the first integrative metabolic basis for the dynamics of recovery during perfusion treatment of marginal livers. Our initial findings support enhanced oxygen delivery for both timely recovery and long-term sustenance. These results are expected to lead the optimization of the treatment protocols and perfusion media from a metabolic perspective, facilitating translation to clinical use

A Fitness Index for Transplantation of Machine-Perfused Cadaveric Rat Livers

Background: The 110,000 patients currently on the transplant waiting list reflect the critical shortage of viable donor organs. However, a large pool of unused organs, from donors after cardiac death (DCD) that are disqualified because of extensive ischemic injury, may prove transplantable after machine perfusion treatment, fundamentally impacting the availability of treatment for end-stage organ failure. Machine perfusion is an ex-vivo organ preservation and treatment procedure that has the capacity to quantitatively evaluate and resuscitate cadaveric organs for transplantation. Methods To diagnose whether an organ was fresh or ischemic, an initial assessment of liver quality was conducted via dynamic discriminant analysis. Subsequently, to determine whether the organs were sufficiently viable for successful implantation, fitness indices for transplantation were calculated based on squared prediction errors (SPE) for fresh and ischemic livers. Results: With just three perfusate metabolites, glucose, urea and lactate, the developed MPLSDA model distinguished livers as fresh or ischemic with 90% specificity. The SPE analyses revealed that fresh livers with SPEF < 10.03 and WI livers with SPEWI < 3.92 yield successful transplantation with 95% specificity. Conclusions: The statistical methods used here can discriminate between fresh and ischemic livers based on simple metabolic indicators measured during perfusion. The result is a predictive fitness index for transplantation of rat livers procured after cardiac death. The translational implications of this study are that any donor organ procured from controlled, but most especially from uncontrolled cardiac death donors, will be objectively assessed and its recovery monitored over time, minimizing the critical loss of otherwise viable organs

Recovery of donor hearts after circulatory death with normothermic extracorporeal machine perfusion

OBJECTIVES A severe donor organ shortage leads to the death of a substantial number of patients who are listed for transplantation. The use of hearts from donors after circulatory death could significantly expand the donor organ pool, but due to concerns about their viability, these are currently not used for transplantation. We propose short-term ex vivo normothermic machine perfusion (MP) to improve the viability of these ischaemic donor hearts. METHODS Hearts from male Lewis rats were subjected to 25 min of global in situ warm ischaemia (WI) (37°C), explanted, reconditioned for 60 min with normothermic (37°C) MP with diluted autologous blood and then stored for 4 h at 0-4°C in Custodiol cold preservation solution. Fresh and ischaemic hearts stored for 4 h in Custodiol were used as controls. Graft function was assessed in a blood-perfused Langendorff circuit. RESULTS During reconditioning, both the electrical activity and contractility of the ischaemic hearts recovered rapidly. Throughout the Langendorff reperfusion, the reconditioned ischaemic hearts had a higher average heart rate and better contractility compared with untreated ischaemic controls. Moreover, the reconditioned ischaemic hearts had higher tissue adenosine triphosphate levels and a trend towards improved tissue redox state. Perfusate levels of troponin T, creatine kinase and lactate dehydrogenase were not significantly lower than those of untreated ischaemic controls. The micro- and macroscopic appearance of the reconditioned ischaemic hearts were improved compared with ischaemic controls, but in both groups myocardial damage and oedema were evident. CONCLUSIONS Our results indicate that functional recovery from global WI is possible during short-term ex vivo reperfusion, allowing subsequent cold storage without compromising organ viability. We expect that once refined and validated, this approach may enable safe transplantation of hearts obtained from donation after circulatory deat

Median sternotomy

Sternotomy is considered to be the gold standard incision in cardiac surgery, resulting in low failure rates and excellent proven long-term outcomes. It can also be used in thoracic surgery for mediastinal, bilateral pulmonary or lower trachea and main stem bronchus surgery. Sternotomy has to be performed properly to avoid short- and long-term morbidity and mortality. The surgical technique is well established and certain principles are recognized to be crucial to minimize complications. The identification of the correct landmarks, midline tissue preparation, osteotomy with the avoidance of injury to underlying structures like pleura, pericardium, innominate vein, brachiocephalic artery and ectatic ascending aorta, and targeted bleeding control are important steps of the procedure. As important as the performance of a proper sternotomy is a correct sternal closure. An override or shift of the sternal edges has to be avoided by placing the wires at a proper distance from each other without injuring the thoracic pedicle. The two sternal halves have to be tightly re-approximated to facilitate healing of the bone and to avoid instability, which is a risk factor for wound infection. With a proper performance of sternotomy and sternal closure, instability and wound infections are rare and depend on patient-related risk factors

Recovery of donor hearts after circulatory death with normothermic extracorporeal machine perfusion

OBJECTIVES A severe donor organ shortage leads to the death of a substantial number of patients who are listed for transplantation. The use of hearts from donors after circulatory death could significantly expand the donor organ pool, but due to concerns about their viability, these are currently not used for transplantation. We propose short-term ex vivo normothermic machine perfusion (MP) to improve the viability of these ischaemic donor hearts. METHODS Hearts from male Lewis rats were subjected to 25 min of global in situ warm ischaemia (WI) (37°C), explanted, reconditioned for 60 min with normothermic (37°C) MP with diluted autologous blood and then stored for 4 h at 0-4°C in Custodiol cold preservation solution. Fresh and ischaemic hearts stored for 4 h in Custodiol were used as controls. Graft function was assessed in a blood-perfused Langendorff circuit. RESULTS During reconditioning, both the electrical activity and contractility of the ischaemic hearts recovered rapidly. Throughout the Langendorff reperfusion, the reconditioned ischaemic hearts had a higher average heart rate and better contractility compared with untreated ischaemic controls. Moreover, the reconditioned ischaemic hearts had higher tissue adenosine triphosphate levels and a trend towards improved tissue redox state. Perfusate levels of troponin T, creatine kinase and lactate dehydrogenase were not significantly lower than those of untreated ischaemic controls. The micro- and macroscopic appearance of the reconditioned ischaemic hearts were improved compared with ischaemic controls, but in both groups myocardial damage and oedema were evident. CONCLUSIONS Our results indicate that functional recovery from global WI is possible during short-term ex vivo reperfusion, allowing subsequent cold storage without compromising organ viability. We expect that once refined and validated, this approach may enable safe transplantation of hearts obtained from donation after circulatory death

A fitness index for transplantation of machine-perfused cadaveric rat livers

Abstract Background The 110,000 patients currently on the transplant waiting list reflect the critical shortage of viable donor organs. However, a large pool of unused organs, from donors after cardiac death (DCD) that are disqualified because of extensive ischemic injury, may prove transplantable after machine perfusion treatment, fundamentally impacting the availability of treatment for end-stage organ failure. Machine perfusion is an ex-vivo organ preservation and treatment procedure that has the capacity to quantitatively evaluate and resuscitate cadaveric organs for transplantation. Methods To diagnose whether an organ was fresh or ischemic, an initial assessment of liver quality was conducted via dynamic discriminant analysis. Subsequently, to determine whether the organs were sufficiently viable for successful implantation, fitness indices for transplantation were calculated based on squared prediction errors (SPE) for fresh and ischemic livers. Results With just three perfusate metabolites, glucose, urea and lactate, the developed MPLSDA model distinguished livers as fresh or ischemic with 90% specificity. The SPE analyses revealed that fresh livers with SPEF WI  Conclusions The statistical methods used here can discriminate between fresh and ischemic livers based on simple metabolic indicators measured during perfusion. The result is a predictive fitness index for transplantation of rat livers procured after cardiac death. The translational implications of this study are that any donor organ procured from controlled, but most especially from uncontrolled cardiac death donors, will be objectively assessed and its recovery monitored over time, minimizing the critical loss of otherwise viable organs.</p

Mid-term outcomes of minimally invasive direct coronary artery bypass grafting

Background Minimally invasive direct coronary artery bypass grafting (MIDCAB) has gained wide acceptance for the treatment of single vessel disease of the left anterior descending artery (LAD). Here, we present our single center experience of 152 consecutive patients. Materials and Methods All patients underwent MIDCAB through a left anterior minithoracotomy between January 1, 2009, and December 31, 2012. Preoperative, intraoperative, postoperative, and follow-up data including major adverse cardiac and cerebrovascular events (MACCE) and need for re-intervention were collected. Results Mean age was 64.4 ± 11 years, median additive EuroSCORE 3 (0-11), 84% were male. All except one patient were successfully operated without cardiopulmonary bypass. Seven patients with unexpected severely calcified LADs were converted to sternotomy (4.6%); 91.3% were extubated in the operating room or on the day of surgery. Median stay at the intensive care unit and in hospital were 1 (0-97) and 7 (1-49) days, respectively. Thirty-day mortality was 1.9%. There was no stroke. Five patients (3.2%) had to be re-explored for bleeding and 95% received no transfusion. Median follow-up was 24 months (0-97) and complete in 93.3% with overall survival of 92.4 ± 0.2% and MACCE-free survival of 96.1 ± 1.7%. Two patients had a re-intervention of the LAD. Conclusion MIDCAB is a safe procedure with low postoperative morbidity, mortality, and favorable mid-term MACCE-free survival in selected patients that should be discussed in a heart team setting to evaluate the "ideal" individual treatment option