Effects of cyclosporine a in ex vivo reperfused pig lungs.

OBJECTIVE: Several works highlight the role of CsA in the prevention of IRI, but none focus on isolated lungs. Our objective was to evaluate the effects of CsA on IRI on ex vivo reperfused pig lungs. METHODS: Thirty-two pairs of pig lungs were collected and stored for 30 minutes at 4 °C. The study was performed in four groups. First, a control group and then three groups receiving different concentrations of CsA (1, 10, and 30 µM) at two different times: once at the moment of lung procurement and another during the reperfusion procedure. The ex vivo lung preparation was set up using an extracorporeal perfusion circuit. Gas exchange parameters, pulmonary hemodynamics, and biological markers of lung injury were collected for the evaluation. RESULTS: CsA improved the PaO2 /FiO2 ratio, but it also increased PAP, Pcap, and pulmonary vascular resistances with dose-dependent effects. Lungs treated with high doses of CsA displayed higher capillary-alveolar permeability to proteins, lower AFC capacities, and elevated concentrations of pro-inflammatory cytokines. CONCLUSIONS: These data suggest a possible deleterious imbalance between the beneficial cell properties of CsA in IRI and its hemodynamic effects on microvascularization.

Monitoring of endogenous nitric oxide exhaled by pig lungs during ex-vivo lung perfusion.

In the context of organ shortage for transplantation, new criteria for better organ evaluation should be investigated. Ex-vivo lung perfusion (EVLP) allows extra-corporal lung re-conditioning and evaluation, under controlled parameters of the organ reperfusion and mechanical ventilation. This work reports on the interest of exhaled gas analysis during the EVLP procedure. After a 1 h cold ischemia, the endogenous gas production by an isolated lung of nitric oxide and carbon monoxide is simultaneously monitored in real time. The exhaled gas is analysed with two very sensitive and selective laser spectrometers developed upon the technique of optical-feedback cavity-enhanced absorption spectroscopy. Exhaled gas concentration measured for an ex-vivo lung is compared to the corresponding production by the whole living pig, measured before euthanasia. On-line measurements of the fraction of nitric oxide in exhaled gas (FENO) in isolated lungs are reported here for the first time, allowing to resolve the respiratory cycles. In this study, performed on 9 animals, FENO by isolated lungs range from 3.3 to 10.6 ppb with a median value of 4.4 ppb. Pairing ex-vivo lung and pig measurements allows to demonstrate a systematic increase of FENO in the ex-vivo lung as compared to the living animal, by a factor of 3 ± 1.2. Measurements of the fraction of carbon monoxide in exhaled gas (FECO) confirm levels recorded during previous studies driven to evaluate FECO as a potential marker of ischemia reperfusion injuries. FECO production by ex-vivo lungs ranges from 0.31 to 2.3 ppm with a median value of 0.8 ppm. As expected, these FECO values are lower than the production by the corresponding whole pig body, by a factor of 6.9 ± 2.7.

Exhaled carbon monoxide is correlated with ischemia reperfusion injuries during ex vivo lung perfusion in pigs.

Measurement of exhaled carbon monoxide (eCO) might help in the selection of lung grafts during ex vivo lung perfusion (EVLP) since its endogenous production is increased under ischemia reperfusion. The objective of this study was to measure eCO variations depending on the extent of lung ischemia reperfusion injuries. Using a porcine model and a laser spectrometer instrument, eCO was measured during EVLP. eCO was compared after 30 min (D0) or 24 h (D1) of cold ischemia. The ability of eCO to distinguish lungs deemed suitable for transplantation was evaluated. Six lungs were studied at D0 and compared to six lungs studied at D1. eCO was systematically higher on D1 (1.35 ± 0.26 ppmv versus 0.95 ± 0.31 ppmv, p = 0.01). The best threshold concentration for eCO to select lungs was 0.86 ppmv (area under the receiver operating characteristic curve: 0.65 [95% confidence interval: 0.34-0.97], p = 0.40). These results show that eCO varies during EVLP. The interpretation of this variation and the role of eCO as a biomarker of ischemia reperfusion injuries during EVLP should be tested in further clinical studies.

Deep Hypothermic Cardiac Arrest Treated by Extracorporeal Life Support in a Porcine Model: Does the Rewarming Method Matter?

OBJECTIVES: Extracorporeal life support (ECLS) is the reference rewarming technique of accidental deep hypothermic cardiac arrest (DHCA). This study was designed to examine the impact of different rewarming blood flow rates and temperature setting of ECLS on cardiopulmonary lesions after DHCA in a porcine model of accidental hypothermia. METHODS: Twenty-four pigs were cannulated for ECLS, cooled until DHCA occurred, and subjected to 30 minutes of cardiac arrest. During the rewarming phase, we compared a low blood flow rate of 1.5 L/min versus a high flow rate of 3.0 L/min as well as two-temperature-setting rewarming strategies: a temperature during ECLS adjusted to 5°C above the central core temperature versus 38°C maintained throughout the rewarming phase. Cardiac output, hemodynamics and pulmonary function parameters were evaluated. Biologic markers of ischemia-reperfusion injuries were analyzed at baseline and at the end of the experiment. RESULTS: DHCA occurred at 21.2 ± 2°C. There was a trend for better cardiac output in groups with high blood flow (p = 0.053), with no interaction between ECLS flow and temperature (p = 0.63), a trend toward lower pulmonary vascular resistance (PVR; p = 0.075) and a significant decrease in arterial PVR in groups with high blood flow (p = 0.013) with no interaction (p = 0.47 and p = 0.60 for PVR and arterial PVR, respectively). Serum interleukin-6, tumor necrosis factor-α, receptor for advanced glycation end products (RAGE), and neuron-specific enolase were significantly increased between baseline and endpoint. The increase in the serum RAGE concentration was higher in the 38°C rewarming temperature groups compared to 5°C above adjusted temperature. There were no other significant differences in biomarkers. CONCLUSIONS: We developed a porcine model of DHCA treated by ECLS. Our data suggest that cardiac output tended to improve with a high-flow-rate rewarming strategy while a high-temperature delta between core temperature and ECLS increased the RAGE markers of lung injury.

Cardiopulmonary responses during the cooling and the extracorporeal life support rewarming phases in a porcine model of accidental deep hypothermic cardiac arrest.

BACKGROUND: This study aimed to assess cardiac and pulmonary pathophysiological responses during cooling and extracorporeal life support (ECLS) rewarming in a porcine model of deep hypothermic cardiac arrest (DHCA). In addition, we evaluated whether providing a lower flow rate of ECLS during the rewarming phase might attenuate cardiopulmonary injuries. METHODS: Twenty pigs were cannulated for ECLS, cooled until DHCA occurred and subjected to 30 min of cardiac arrest. In order to assess the physiological impact of ECLS on cardiac output we measured flow in the pulmonary artery using Doppler echocardiography as well as a modified thermodilution technique using the Swan-Ganz catheter (injection site in the right ventricle). The animals were randomized into two groups during rewarming: a group with a low blood flow rate of 1.5 L/min (LF group) and a group with a normal flow rate of 3.0 L/min (NF group). The ECLS temperature was adjusted to 5 °C above the central core. Cardiac output, hemodynamics and pulmonary function parameters were evaluated. RESULTS: During the cooling phase, cardiac output, heart rhythm and blood pressure decreased continuously. Pulmonary artery pressure tended to increase at 32 °C compared to the initial value (20.2 ± 1.7 mmHg vs. 29.1 ± 5.6 mmHg, p = 0.09). During rewarming, arterial blood pressure was higher in the NF than in the LF group at 20° and 25 °C (p = 0.003 and 0.05, respectively). After rewarming to 35 °C, cardiac output was 3.9 ± 0.5 L/min in the NF group vs. 2.7 ± 0.5 L/min in LF group (p = 0.06). At the end of rewarming under ECLS cardiac output was inversely proportional to the ECLS flow rate. Moreover, the ECLS flow rate did not significantly change pulmonary vascular resistance. DISCUSSION: Using a newly developed experimental model of DHCA treated by ECLS, we assessed the cardiac and pulmonary pathophysiological response during the cooling phase and the ECLS rewarming phase. Despite lower metabolic need during hypothermia, a low ECLS blood flow rate during rewarming did not improved cardiopulmonary injuries after rewarming. CONCLUSION: A low ECLS flow rate during the rewarming phase did not attenuate pulmonary lesions, increased blood lactate level and tended to decrease cardiac output after rewarming. A normal ECLS flow rate did not increase pulmonary vascular resistance compared to a low flow rate. This experimental model on pigs contributes a number of pathophysiological findings relevant to the rewarming strategy for patients who have undergone accidental DHCA.

Real-time measurements of endogenous carbon monoxide production in isolated pig lungs.

Ischemia-reperfusion injuries are a critical determinant of lung transplantation success. The endogenous production of carbon monoxide (CO) is triggered by ischemia-reperfusion injuries. Our aim was, therefore, to assess the feasibility of exhaled CO measurements during the ex vivo evaluation of lungs submitted to ischemia-reperfusion injuries. Five pigs were euthanized and their lungs removed after pneumoplegia. After cold storage (30 min, 4°C), the lungs were connected to an extracorporeal membrane oxygenation circuit, slowly warmed-up, and ventilated. At the end of a 45-min steady state, CO measurements were performed by optical-feedback cavity-enhanced absorption spectroscopy, a specific laser-based technique for noninvasive and real-time low gas concentration measurements. Exhaled CO concentration from isolated lungs reached 0.45±0.19 ppmv and was above CO concentration in ambient air and in medical gas. CO variations peaked during the expiratory phase. Changes in CO concentration in ambient air did not alter CO concentrations in isolated lungs. Exhaled CO level was also found to be uncorrelated to heme oxygenase (HO-1) gene expression. These results confirm the feasibility of accurate and real-time CO measurement in isolated lungs. The presented technology could help establishing the exhaled CO concentration as a biomarker of ischemia-reperfusion injury in ex vivo lung perfusion.