ABSTRACT
BACKGROUND: Transplant candidates on the waiting list are increasingly challenged by the lack of organs. Most of the organs can only be kept viable within very limited timeframes (e.g., mere 4-6 h for heart and lungs exposed to refrigeration temperatures ex vivo). Donation after circulatory death (DCD) using extracorporeal membrane oxygenation (ECMO) can significantly enlarge the donor pool, organ yield per donor, and shelf life. Nevertheless, clinical attempts to recover organs for transplantation after uncontrolled DCD are extremely complex and hardly reproducible. Therefore, as a preliminary strategy to fulfill this task, experimental protocols using feasible animal models are highly warranted. The primary aim of the study was to develop a model of ECMO-based cadaver organ recovery in mice. Our model mimics uncontrolled organ donation after an "out-of-hospital" sudden unexpected death with subsequent "in-hospital" cadaver management post-mortem. The secondary aim was to assess blood gas parameters, cardiac activity as well as overall organ state. The study protocol included post-mortem heparin-streptokinase administration 10 min after confirmed death induced by cervical dislocation under full anesthesia. After cannulation, veno-arterial ECMO (V-A ECMO) was started 1 h after death and continued for 2 h under mild hypothermic conditions followed by organ harvest. Pressure- and flow-controlled oxygenated blood-based reperfusion of a cadaver body was accompanied by blood gas analysis (BGA), electrocardiography, and histological evaluation of ischemia-reperfusion injury. For the first time, we designed and implemented, a not yet reported, miniaturized murine hemodialysis circuit for the treatment of severe hyperkalemia and metabolic acidosis post-mortem. RESULTS: BGA parameters confirmed profound ischemia typical for cadavers and incompatible with normal physiology, including extremely low blood pH, profound negative base excess, and enormously high levels of lactate. Two hours after ECMO implantation, blood pH values of a cadaver body restored from < 6.5 to 7.3 ± 0.05, pCO2 was lowered from > 130 to 41.7 ± 10.5 mmHg, sO2, base excess, and HCO3 were all elevated from below detection thresholds to 99.5 ± 0.6%, - 4 ± 6.2 and 22.0 ± 6.0 mmol/L, respectively (Student T test, p < 0.05). A substantial decrease in hyperlactatemia (from > 20 to 10.5 ± 1.7 mmol/L) and hyperkalemia (from > 9 to 6.9 ± 1.0 mmol/L) was observed when hemodialysis was implemented. On balance, the first signs of regained heart activity appeared on average 10 min after ECMO initiation without cardioplegia or any inotropic and vasopressor support. This was followed by restoration of myocardial contractility with a heart rate of up to 200 beats per minute (bpm) as detected by an electrocardiogram (ECG). Histological examinations revealed no evidence of heart injury 3 h post-mortem, whereas shock-specific morphological changes relevant to acute death and consequent cardiac/circulatory arrest were observed in the lungs, liver, and kidney of both control and ECMO-treated cadaver mice. CONCLUSIONS: Thus, our model represents a promising approach to facilitate studying perspectives of cadaveric multiorgan recovery for transplantation. Moreover, it opens new possibilities for cadaver organ treatment to extend and potentiate donation and, hence, contribute to solving the organ shortage dilemma.
ABSTRACT
Plasticizers in polyvinyl chloride (PVC) are not covalently bound to the polymer and can thus migrate into the contact medium. The presented study investigated the potential effects of phospholipid-lining as anti-coagulation coating (ACC) on the migration rate of plasticizers from PVC tubing into blood. For the in-vitro study, five different groups of tubing sets in six replicates were perfused with sheep blood (Group A: PVC plasticized with di-(2-ethylhexyl) phthalate (DEHP) without ACC, Group B: DEHP-plasticized PVC with ACC, Group C: PVC plasticized with tri-(2-ethylhexyl) trimellitate (TOTM) without ACC, Group D: TOTM-plasticized PVC with ACC, Group E (control group): polyolefin material with ACC but without plasticizers). Both the levels of the unchanged plasticizers in blood and the concentration levels of their primary degradation products were assessed. For DEHP, the primary metabolite MEHP (mono-(2-ethylhexyl) phthalate) was determined. The isomers of MEHTM (mono-(2-ethylhexyl) trimellitate) and DEHTM (di-(2-ethylhexyl) trimellitate), respectively, were investigated as primary metabolites of TOTM. The calculated DEHP equivalents (sum of determined levels of DEHP and MEHP) after 24â¯h of perfusion displayed a tendency towards lower levels in the tubing sets without ACC (Group A (201⯱â¯56.4⯵mol/L)) compared to the tubing sets with ACC (Group B (253⯱â¯369⯵mol/L)). Significantly different DEHP equivalents between Group A and Group B were found after a perfusion time of 6â¯h and 10â¯h, respectively. A similar effect was observed for the TOTM-containing tubing sets. However, the absolute plasticizer migration rate of TOTM (TOTM equivalents) after 24â¯h of perfusion was found to be significantly lower compared to that of DEHP (with a factor of over 200). The results indicate that phospholipid coating (ACC) rather enhances the migration of plasticizers and of their primary degradation products from PVC tubing into streaming blood. The enhancement effect was found to be slightly greater for TOTM, but as TOTM migrates in significantly lower levels than DEHP in all experimental settings, TOTM is confirmed to be a recommendable alternative plasticizer to DEHP in medical devices.
