Alvaro Rojas-Pena

Donation after circulatory determination of death: the university of michigan experience with extracorporeal support.

Background Extracorporeal support (ECS) during organ procurement from donors after circulatory determination of death (DCDD) could increase the number of donor organs and decrease posttransplant complications. This study reports the experience of a large transplant center with controlled DCDD. Methods A retrospective review of all potential controlled-DCDD cases between October 1, 2000 and July 31, 2013 was performed. We focused on methods, ethical and practical issues, and recipient outcome data of organs procured and transplanted in our institution using ECS-assisted DCDD (E-DCDD). Results ECS was used for organ procurement in 37 controlled DCDD. The number of organs procured per donor was 2.59, and the number of organs transplanted per donor was 1.68. Delayed graft function occurred in 31% of renal grafts. In three donors (8%), organ donation was not completed because of surgeon judgment. Forty-eight renal grafts (65.8%), thirteen livers (61.9%), and one pancreas (50%) were successfully transplanted. Conclusions ECS can be routinely implemented in controlled DCDD. In our experience, the organs provided per donor was 2.59. Widely applied, EDCDD could result in more donor organs, especially when applied to DCDD in uncontrolled conditions.

An extracorporeal artificial placenta supports extremely premature lambs for 1 week

PURPOSE The treatment of extreme prematurity remains an unsolved problem. We developed an artificial placenta (AP) based on extracorporeal life support (ECLS) that simulates the intrauterine environment and provides gas exchange without mechanical ventilation (MV) and compared it to the current standard of neonatal care. METHODS Extremely premature lambs (110-120 days; term=145d) were used. AP lambs (n=9) were cannulated (jugular drainage, umbilical vein reinfusion) for ECLS. Control lambs (n=7) were intubated, ventilated, given surfactant, and transitioned to high-frequency oscillatory ventilation. All lambs received parenteral nutrition, antibiotics, and steroids. Hemodynamics, blood gases, hemoglobin, and circuit flows were measured. RESULTS Four premature lambs survived for 1 week on the AP, with one surviving 6 days. Adequate oxygenation and ventilation were provided by the AP. The MV lambs survived 2-8 hours. Each of these lambs experienced a transient improvement with surfactant, but developed progressive hypercapnea and hypoxia despite high airway pressures and HFOV. CONCLUSIONS Extremely premature lambs were supported for 1 week with the AP with hemodynamic stability and adequate gas exchange. Mechanically ventilated lambs succumbed within 8 hours. Further studies will assess control of fetal circulation and organ maturation on the AP.

Development of an Artificial Placenta IV: 24-Hour Venovenous Extracorporeal Life Support in Premature Lambs

An extracorporeal artificial placenta would change the paradigm of treating extremely premature infants. We hypothesized that a venovenous extracorporeal life support (VV-ECLS) artificial placenta would maintain fetal circulation, hemodynamic stability, and adequate gas exchange for 24 hours. A near-term neonatal lamb model (130 days; term = 145 days) was used (n = 9). The right jugular vein was cannulated for VV-ECLS outflow, and an umbilical vein was used for inflow. The circuit included a peristaltic roller pump and a 0.5 m2 hollow fiber oxygenator. Lambs were maintained on VV-ECLS in an “amniotic bath” for up to 24 hours. Five of nine fetuses survived for 24 hours. In the survivors, average mean arterial pressure was 69 ± 10 mm Hg for the first 4 hours and 36 ± 8 mm Hg for the remaining 20 hours. The mean fetal heart rate was 202 ± 30. Mean VV-ECLS flow was 94 ± 20 ml/kg/min. Using a gas mixture of 50% O2/3% CO2 and sweep flow of 1–2 L/min, the mean pH was 7.27 ± 0.09, with Po2 of 35 ± 12 mm Hg and Pco2 of 48 ± 12 mm Hg. Necropsy revealed a patent ductus arteriosus in all cases, and there was no gross or microscopic intracranial hemorrhage. Complications in failed attempts included technically difficult cannulation and multisystem organ failure. Future studies will enhance stability and address the factors necessary for long-term support.

The Effect of Ex Situ Perfusion in a Swine Limb Vascularized Composite Tissue Allograft on Survival up to 24 Hours

PURPOSE To test the potential for the ex situ limb perfusion system to prolong limb allograft survival up to 24 hours. METHODS We used 20 swine for the study. In group 1 (control), 4 limbs were perfused with heparin solution and preserved at 4°C for 6 hours. In group 2, 4 limbs were perfused with autologous blood at 27°C to 32°C for 24 hours. In both groups, limbs were transplanted orthotopically to recipients and monitored for 12 hours. In addition to perfusion parameters, we recorded perfusate gases and electrolytes (pH, pCO2, pO2, O2 saturation, Na, K, Cl, Ca, HCO3, glucose, and lactate) and obtained functional electrostimulation hourly throughout the experiment. Histology samples were obtained for TUNEL staining and single-muscle fiber contractility testing. RESULTS In both groups, hemodynamic variables of circulation remained stable throughout the experiment. Neuromuscular electrical stimulation remained intact until the end of reperfusion in group 2 vs no response in group 1. In group 2, a gradual increase in lactate levels during pump perfusion returned to normal after transplantation. Compared with the contralateral limb in group 2, single-muscle fiber contractility testing showed no significant difference at the end of the experiment. CONCLUSIONS We demonstrated extended limb survival up to 24 hours using normothermic pulsatile perfusion and autologous blood. CLINICAL RELEVANCE Successful prolongation of limb survival using ex situ perfusion methods provides with more time for revascularization of an extremity.

Development of an artificial placenta V: 70 h veno-venous extracorporeal life support after ventilatory failure in premature lambs

PURPOSE An artificial placenta would change the paradigm of treating extremely premature infants. We hypothesized that using a veno-venous extracorporeal life support (VV-ECLS) artificial placenta after ventilatory failure would stabilize premature lambs and maintain normal fetal physiologic parameters for 70 h. METHODS A near-term neonatal lamb model (130 days; term=145) was used. The right jugular vein (drainage) and umbilical vein (reinfusion) were cannulated with 10-12 Fr cannulas. Lambs were then transitioned to an infant ventilator. After respiratory failure, the endotracheal tube was filled with amniotic fluid, and VV-ECLS total artificial placenta support (TAPS) was initiated. Lambs were maintained on TAPS for 70 h. RESULTS Six of seven lambs survived for 70 h. Mean ventilation time was 57 ± 22 min. During ventilation, mean MAP was 51 ± 14 mmHg, compared to 44 ± 14 mmHg during TAPS (p=0.001). Mean pH and lactate during ventilation were 7.06 ± 0.15 and 5.7 ± 2.3 mmol/L, compared to 7.33 ± 0.07 and 2.0 ± 1.8 mmol/L during TAPS (p<0.001 for both). pO(2) and pCO(2) remained within normal fetal parameters during TAPS, and mean carotid blood flow was 25 ± 7.5 mL/kg/min. Necropsy showed a patent ductus arteriosus and no intracranial hemorrhage in all animals. CONCLUSIONS The artificial placenta stabilized premature lambs after ventilatory failure and maintained fetal circulation, hemodynamic stability, gas exchange, and cerebral perfusion for 70 h.

Ex Situ Limb Perfusion System to Extend Vascularized Composite Tissue Allograft Survival in Swine.

Background Organ perfusion systems have successfully been applied in solid organ transplantations. Their use in limb transplantation and replantation has not been widely investigated. In this study, we tested the potential for ex situ perfusion system to prolong limb allograft viability in a swine forelimb amputation/replantation model. Methods Fourteen swine were used. In group 1 (n = 4), we perfused 4 amputated limbs for 12 hours using warm (27°C–32°C) autologous blood. Group 2 (n = 3) served as a cold preservation control group, preserving limbs for 6 hours at 4°C. All limbs were transplanted into healthy swine (n = 7) and observed for another 12 hours. Hemodynamic variables of circulation, as well as perfusate gases and electrolytes (pH, pCO2, pO2, O2 saturation, Na+, K+, Cl−, Ca2+, HCO3−, glucose, lactate) were measured. Muscle samples were used to measure single-muscle fiber contractility. Results In the control group, no microcirculation was observed after 6 hours of cold storage. In the pump perfusion group, all limbs displayed a gradual increase in lactate levels (P < 0.05) during ex situ perfusion that returned to normal after transplantation and reperfusion (P = 0.05). The pH and potassium remained stable throughout the experiment. Single-muscle fiber contractility testing showed near normal contractility at the end of the reperfusion period (P > 0.05). Limb weight did not increase significantly between the end of pump perfusion and reperfusion (P > 0.05). Conclusions We demonstrated the potential to preserve limb allograft using ex vivo circulation. This approach promises to extend the narrow time frame for revascularization of procured extremities in limb transplantation.

Ex situ perfusion of human limb allografts for 24 hours

Background Vascularized composite allografts, particularly hand and forearm, have limited ischemic tolerance after procurement. In bilateral hand transplantations, this demands a 2 team approach and expedited transfer of the allograft, limiting the recovery to a small geographic area. Ex situ perfusion may be an alternative allograft preservation method to extend allograft survival time. This is a short report of 5 human limbs maintained for 24 hours with ex situ perfusion. Methods Upper limbs were procured from brain-dead organ donors. Following recovery, the brachial artery was cannulated and flushed with 10 000 U of heparin. The limb was then attached to a custom-made, near-normothermic (30-33°C) ex situ perfusion system composed of a pump, reservoir, and oxygenator. Perfusate was plasma-based with a hemoglobin concentration of 4 to 6 g/dL. Results Average warm ischemia time was 76 minutes. Perfusion was maintained at an average systolic pressure of 93 ± 2 mm Hg, flow 310 ± 20 mL/min, and vascular resistance 153 ± 16 mm Hg/L per minute. Average oxygen consumption was 1.1 ± 0.2 mL/kg per minute. Neuromuscular electrical stimulation continually displayed contraction until the end of perfusion, and histology showed no myocyte injury. Conclusions Human limb allografts appeared viable after 24 hours of near-normothermic ex situ perfusion. Although these results are early and need validation with transplantation, this technology has promise for extending allograft storage times.

Development of a wearable bioartificial kidney using the Bioartificial Renal Epithelial Cell System (BRECS).

Cell therapy for the treatment of renal failure in the acute setting has proved successful, with therapeutic impact, yet development of a sustainable, portable bioartificial kidney for treatment of chronic renal failure has yet to be realized. Challenges in maintaining an anticoagulated blood circuit, the typical platform for solute clearance and support of the biological components, have posed a major hurdle in advancement of this technology. This group has developed a Bioartificial Renal Epithelial Cell System (BRECS) capable of differentiated renal cell function while sustained by body fluids other than blood. To evaluate this device for potential use in end‐stage renal disease, a large animal model was established that exploits peritoneal dialysis fluid for support of the biological device and delivery of cell therapy while providing uraemic control. Anephric sheep received a continuous flow peritoneal dialysis (CFPD) circuit that included a BRECS. Sheep were treated with BRECS containing 1 × 108 renal epithelial cells or acellular sham devices for up to 7 days. The BRECS cell viability and activity were maintained with extracorporeal peritoneal fluid circulation. A systemic immunological effect of BRECS therapy was observed as cell‐treated sheep retained neutrophil oxidative activity better than sham‐treated animals. This model demonstrates that use of the BRECS within a CFPD circuit embodies a feasible approach to a sustainable and effective wearable bioartificial kidney. Copyright

Timing of heparin and perfusion temperature during procurement of organs with extracorporeal support in donors after circulatory determination of death.

Despite successful resuscitation of donors after circulatory determination of death (DCD) with extracorporeal support (ECS), the technique is limited by ethical concerns about donor management (heparinization) and the complexity to operate the ECS circuit. This work studies different timing of heparin administration and the effects of ECS-perfusion temperature. Cardiac arrest (CA) was induced in swine. Heparin studies, three groups: 1) PRE5, heparin 5 minutes before CA; 2) POST5, heparin 5 minutes after CA, plus 2 minutes external chest compressions; and 3) POST30, heparin with the initiation of ECS after 30 minutes CA. Perfusion temperature study, two groups: 1) normothermic, ECS-38.5°C after 30 minutes CA and 2) room temperature, ECS-25.5°C for the first 90 minutes, followed by ECS-38.5°C. Heparin studies: ECS target flows (>50 ml/kg/min) were not achieved in the POST30 group, affecting local organ perfusion as observed with poor bile (<4 ml/min) and urine output (<25 ml/min), when compared with the other groups (normal values). Temperature study: In both groups, ECS target flows were reached, and urine/bile output was restored. Heparinization 5 minutes after CA is equivalent to premortem heparinization in this ECS-DCD model. Heparinization after CA could reduce ethical concerns. Donors after circulatory determination of death were successfully resuscitated at both temperatures, suggesting that the heat exchanger/water heater can be removed to simplify the ECS circuit.

In vivo testing of a novel blood pump for short-term extracorporeal life support.

BACKGROUND Centrifugal pumps are used increasingly for temporary mechanical support for the treatment of cardiogenic shock. However, centrifugal pumps can generate excessive negative pressure and are afterload sensitive. A previously developed modified roller pump mitigates these limitations both in vitro and in preliminary animal experiments. We report the results of intermediate-term testing of our evolving pump technology, known as the BioVAD. METHODS The BioVAD was implanted in 6 adult male sheep (62.5±3.9 kg), with drainage from the left atrium and reinfusion into the descending aorta. The sheep were monitored for 5 days. Heparin was given during the initial implantation, but no additional anticoagulants were given. Data collected included hemodynamic status, pump flow and pressures, laboratory values to monitor end-organ function and hemolysis, pathologic specimens to evaluate for thromboembolic events and organ ischemia, and explanted pump evaluation results. RESULTS All animals survived the planned experimental duration and there were no pump malfunctions. Mean BioVAD flow was 3.57±0.30 L/min (57.1 mL/kg/min) and mean inlet pressure was -30.51±4.25 mm Hg. Laboratory values, including plasma free hemoglobin, creatinine, lactate, and bilirubin levels, remained normal. Three animals had small renal cortical infarcts, but there were no additional thromboembolic events or other abnormalities seen on pathologic examination. No thrombus was identified in the BioVAD blood flow path. CONCLUSIONS The BioVAD performed well for 5 days in this animal model of temporary left ventricular assistance. Its potential advantages over centrifugal pumps may make it applicable for short-term mechanical circulatory support.