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Aim: Head and thorax elevation during cardiopulmonary resuscitation improves cerebral hemodynamics and ultimate neurological outcome after cardiac arrest. Its effect during extracorporeal cardiopulmonary resuscitation (E-CPR) is unknown. We tested whether this procedure could improve hemodynamics in swine treated by E-CPR. Methods and Results: Pigs were anesthetized and submitted to 15 minutes of untreated ventricular fibrillation followed by E-CPR. Animals randomly remained in flat position (flat group) or underwent head and thorax elevation since E-CPR institution (head-up group). Electric shocks were delivered after 30 minutes until the return of spontaneous circulation (ROSC). They were followed during 120 minutes after ROSC. After 30 minutes of E-CPR, ROSC was achieved in all animals, with no difference regarding blood pressure, heart rate, and extracorporeal membrane of oxygenation flow among groups. The head-up group had an attenuated increase in ICP as compared with the flat group after cardiac arrest (13 ± 1 vs. 26 ± 2 mm Hg at the end of the follow-up, respectively). Cerebral perfusion pressure tended to be higher in the head-up versus flat group despite not achieving statistical difference (66 ± 1 vs 46 ± 1 mm Hg at the end of the follow-up). Carotid blood flow and cerebral oxygen saturation were not significantly different among groups. Conclusion: During E-CPR, head and thorax elevation prevents ICP increase. Whether it could improve the ultimate neurological outcome in this situation deserves further investigation.

Background: Cardio-Pulmonary Resuscitation (CPR) decreases lung volume below the functional residual capacity and can generate intrathoracic airway closure. Conversely, large insufflations can induce thoracic distension and jeopardize circulation. The capnogram (CO2 signal) obtained during continuous chest compressions can reflect intrathoracic airway closure and we hypothesized here that it can also indicate thoracic distension. Objectives: to test whether a specific capnogram may identify thoracic distension during CPR and assess its impact on gas exchange and hemodynamics. Methods: 1. In out-of-hospital cardiac arrest patients, we identified on capnograms three patterns: intrathoracic airway closure, thoracic distension or regular pattern. An algorithm was designed to identify them automatically.2. To link CO2 patterns with ventilation, we conducted three experiments:i) Reproducing the CO2 patterns in human cadavers. ii) Assessing the influence of tidal volume and respiratory mechanics on thoracic distension using a mechanical lung model. iii) Exploring the impact of thoracic distension patterns on different circulation parameters during CPR on a pig model. Measurements and main results: Clinical data: 202 patients were included. Intrathoracic airway closure was present in 35%, thoracic distension in 22% and regular pattern in 43%. Experiments:i) Higher insufflated volumes reproduced thoracic distension CO2 patterns in 5 cadavers. ii) In the mechanical lung model, thoracic distension patterns were associated with higher volumes and longer time constants. iii) In six pigs during CPR with various tidal volumes, a CO2 pattern of thoracic distension, but not tidal volume per se, was associated with a significant decrease in blood pressure and cerebral perfusion. Conclusions: During CPR, intrathoracic airway closure, thoracic distension or regular pattern can be identified by capnogram analysis. A thoracic distension pattern on the capnogram may indicate a negative impact of ventilation on blood pressure and cerebral perfusion during CPR, not predicted by tidal volume per se.

Introduction: Neuronal consumption of lactate is known to be protective after long duration of brain ischaemia. However, its consequences on neurological function after shorter duration of ischemia like after cardiac arrest are unknown. Hypothesis: We hypothesized that cerebral lactate consumption is deleterious for neurological outcome, whereas lactate dehydrogenase inhibition by oxamate could improve recovery. Methods: Male New-Zealand rabbits were anesthetized and surgically instrumented to assess lactate, glucose and O 2 cerebral consumption by measurement of the arterio-jugular differences. After 10 min of ventricular fibrillation, animals were resuscitated and randomly received a 30-min infusion of either saline (Control, n=6), lactate (Lact, 5 mg/kg/min, n=6) or oxamate (Oxa, 37.5 mg/kg/min, n=6). They were followed during 4 h. Additional animals were submitted to the same procedure without surgical instrumentation to allow recovery and assessment of neurological function during 48 h after cardiac arrest. In both experiments, neuronal death was assessed histologically by fluorojade C staining. Results: In Control group, a strong increase of the cerebral consumption of O 2 , glucose and lactate was observed during the 4 hours following resuscitation. In Lact group, lactate consumption was increased as compared to Control, whereas it was almost abolished in Oxa group (17.13±3.59, 32.60±6.24 and 4.04±1.58 mmol/L/min in Control, Lact and Oxa, respectively). Additionally, Oxa group presented a reduced consumption of glucose and O 2 after cardiac arrest as compared to other groups. Interestingly, administration of oxamate was highly neuroprotective whereas lactate administration worsened the neurological outcome after cardiac arrest (38±4, 64±10 and 15±6 % of neurological dysfunction score at 48h in Control, Lact and Oxa, respectively). Oxamate infusion was also associated with a significant reduction in the number of degenerative neurons at 4 h and 48 h of follow-up. Conclusions: The cerebral consumption of lactate appeared to be detrimental in rabbits after cardiac arrest. Its inhibition by oxamate is potently neuroprotective.

Introduction: Extracorporeal cardiopulmonary resuscitation (E-CPR) is used for the treatment of refractory cardiac arrest but the optimal target to reach for mean arterial pressure (MAP) remains to be determined. Hypothesis: We hypothesized that MAP levels modify cerebral hemodynamics during E-CPR. Accordingly, we tested two MAP targets (65-75 vs 80-90 mmHg) in a porcine model of E-CPR. Methods: Pigs were anesthetized and instrumented for the evaluation of cerebral and systemic hemodynamics. They were submitted to 15 min of untreated ventricular fibrillation followed by 30 min of E-CPR. Electric attempts of defibrillation were then delivered until resumption of spontaneous circulation (ROSC). Extracorporeal circulation was initially set to an average flow of 40 ml/kg/min with a standardized volume expansion in both groups. The dose of epinephrine was set to reach either a standard or a high MAP target level (65-75 vs 80-90 mmHg, respectively). Animals were followed during 120 min after ROSC. Results: Six animals were included in both groups. After cardiac arrest, MAP was maintained at the expected level (Figure). During E-CPR, high MAP transiently improved carotid blood flow as compared to standard MAP. This blood flow progressively decreased after ROSC in high vs standard MAP, while intra-cranial pressure increased. Interestingly, this was associated with a significant decrease in cerebral oxygen consumption (26±8 vs 54±6 L O 2 /min/kg at 120 min after ROSC, respectively; p Conclusion: Increasing MAP above 80 mmHg with epinephrine aggravates cerebral hemodynamics after E-CPR. Figure: Mean arterial pressure (MAP), cerebral blood flow and oxygen consumption (*, p

Background Ischemic spinal cord injury is a devastating condition after aortic surgery. We determined whether ultrafast and short whole-body hypothermia provided by total liquid ventilation (TLV) attenuated lower limb paralysis after aortic cross-clamping with a targeted temperature management at 33°C versus 36°C. Methods Anesthetized rabbits were submitted to infrarenal aortic cross-clamping during 15 min. A control group (n = 7) was maintained at normothermia (38°C to 38.5°C) with conventional mechanical ventilation. In TLV groups, TLV was started after reperfusion and maintained during 30 min with a target temperature at either 33°C or 36°C (TLV-33°C and TLV-36°C, respectively; n = 7 in each condition). After TLV, animals were resumed to conventional ventilation. Hypothermia was maintained during 120 min, before rewarming and awakening. Hind limb motor function was assessed with modified Tarlov score at day 2 and infarct size in the spinal cord was determined using triphenyltetrazolium chloride staining. Results Target temperature was achieved within 20 minutes in the two TLV groups. At day 2, the modified Tarlov score was significantly lower in the control group, as compared with TLV-33°C and TLV-36°C groups (0.0 ± 0.0 versus 3.1 ± 0.7 and 2.6 ± 0.6, respectively). The infarct size of the spinal cord was also significantly higher in the control group compared with TLV-33°C and TLV-36°C groups (75% ± 10% versus 32% ± 7% and 28% ± 10%, respectively). Neither motor function nor infarct size differed significantly between TLV-33°C and TLV-36°C groups. Conclusions Ultrafast hypothermic TLV attenuates spinal cord injury when applied after ischemic insult. Neurological outcome was similar with targeted temperature management at either 33°C or 36°C.

Mitochondria is often considered as the common nexus of cardiac and cerebral dysfunction after cardiac arrest. Here, our goal was to determine whether the time course of cardiac and cerebral mitochondrial dysfunction is similar after shockable versus non-shockable cardiac arrest in rabbits. Anesthetized rabbits were submitted to 10 min of no-flow by ventricular fibrillation (VF group) or asphyxia (non-shockable group). They were euthanized at the end of the no-flow period or 30 min, 120 min, or 24 h after resuscitation for in vitro evaluation of oxygen consumption and calcium retention capacity. In the brain (cortex and hippocampus), moderate mitochondrial dysfunction was evidenced at the end of the no-flow period after both causes of cardiac arrest versus baseline. It partly recovered at 30 and 120 min after cardiac arrest, with lower calcium retention capacity and higher substrate-dependant oxygen consumption after VF versus non-shockable cardiac arrest. However, after 24 h of follow-up, mitochondrial dysfunction dramatically increased after both VF and non-shockable cardiac arrest, despite greater neurological dysfunction after the latter one. In the heart, mitochondrial dysfunction was also maximal after 24 h following resuscitation, with no significant difference among the causes of the cardiac arrest. During the earlier timing of evaluation, calcium retention capacity and ADP-dependant oxygen consumption were lower and higher, respectively, after non-shockable cardiac arrest versus VF. In conclusion, the kinetics of cardiac and cerebral mitochondrial dysfunction suggests that mitochondrial function does not play a major role in the early phase of the post-resuscitation process but is only involved in the longer pathophysiological events.

International audience; Argon inhalation attenuates multiorgan failure (MOF) after experimental ischemic injury. We hypothesized that this protection could involve decreased High Mobility Group Box 1 (HMGB1) systemic release. We investigated this issue in an animal model of MOF induced by aortic cross-clamping. Anesthetized rabbits were submitted to supra-coeliac aortic cross-clamping for 30 min, followed by 300 min of reperfusion. They were randomly divided into three groups (n = 7/group). The Control group inhaled nitrogen (70%) and oxygen (30%). The Argon group was exposed to a mixture of argon (70%) and oxygen (30%). The last group inhaled nitrogen/oxygen (70/30%) with an administration of the HMGB1 inhibitor glycyrrhizin (4 mg/kg i.v.) 5 min before aortic unclamping. At the end of follow-up, cardiac output was significantly higher in Argon and Glycyrrhizin vs. Control (60 ± 4 and 49 ± 4 vs. 33 ± 8 mL/kg/min, respectively). Metabolic acidosis was attenuated in Argon and Glycyrrhizin vs. Control, along with reduced amount of norepinephrine to reverse arterial hypotension. This was associated with reduced interleukin-6 and HMGB1 plasma concentration in Argon and Glycyrrhizin vs. Control. End-organ damages were also attenuated in the liver and kidney in Argon and Glycyrrhizin vs. Control, respectively. Argon inhalation reduced HMGB1 blood level after experimental aortic cross-clamping and provided similar benefits to direct HMGB1 inhibition.

Background Extracorporeal cardiopulmonary resuscitation (E-CPR) is used for the treatment of refractory cardiac arrest. However, the optimal target to reach for mean arterial pressure (MAP) remains to be determined. We hypothesized that MAP levels critically modify cerebral hemodynamics during E-CPR and tested two distinct targets (65–75 vs 80–90 mmHg) in a porcine model. Methods Pigs were submitted to 15 min of untreated ventricular fibrillation followed by 30 min of E-CPR. Defibrillations were then delivered until return of spontaneous circulation (ROSC). Extracorporeal circulation was initially set to an average flow of 40 ml/kg/min. The dose of epinephrine was set to reach a standard or a high MAP target level (65–75 vs 80–90 mmHg, respectively). Animals were followed during 120-min after ROSC. Results Six animals were included in both groups. During E-CPR, high MAP improved carotid blood flow as compared to standard MAP. After ROSC, this was conversely decreased in high versus standard MAP, while intra-cranial pressure was superior. The pressure reactivity index (PRx), which is the correlation coefficient between arterial blood pressure and intracranial pressure, also demonstrated inverted patterns of alteration according to MAP levels during E-CPR and after ROSC. In standard-MAP, PRx was transiently positive during E-CPR before returning to negative values after ROSC, demonstrating a reversible alteration of cerebral autoregulation during E-CPR. In high-MAP, PRx was negative during E-CPR but became sustainably positive after ROSC, demonstrating a prolonged alteration in cerebral autoregulation after ROSC. It was associated with a significant decrease in cerebral oxygen consumption in high- versus standard-MAP after ROSC. Conclusions During early E-CPR, MAP target above 80 mmHg is associated with higher carotid blood flow and improved cerebral autoregulation. This pattern is inverted after ROSC with a better hemodynamic status with standard versus high-MAP.

Introduction: Profound immune disorders are triggered by cell death and subsequent release of danger signals after cardiac arrest (CA). Hypothesis: High mobility group box-1 (HMGB1) is one of the main endogenous mediators released by ischemic cell death. Our goal was to determine whether its inhibition could provide neuroprotection and improve the outcome after experimental CA. Methods: After 10 min of ventricular fibrillation and resuscitation, rabbits either received an administration of saline (CT group, n=10) or glycyrrhizin (GL group, n=10), a direct inhibitor of HMGB1 (4 mg/kg, i.v.). Animals were followed during 3 days after CA to evaluate the neurological dysfunction. Additional animals were submitted to the same protocol with brain withdrawal 2 or 6 h after CA for immune cell count by cytometry. Results: After CA, HMGB1 blood levels was significantly reduced in CT vs GL group (30±7 vs 17±2 ng/ml at t=30 min after CA). The systemic inflammatory response was subsequently attenuated in GL vs CT, as shown by reduced interleukin-6 concentration (231±34 vs 993±331 pg/ml at 180 min, respectively). In the CT group, a rapid accumulation of neutrophils (CD11b+) and T cells (CD3+, CD4+ and CD8+) was also evidenced in the brain after cardiac arrest. GL specifically reduced the influx of T cells (e.g., 2.7±0.3 vs 7.3±2.6% of CD3+ cells in the brain at 6 h after CA in GL vs CT, respectively) without modifying neutrophils counts. This effect was neither related to differences in blood cells counts nor a modification of blood-brain-barrier permeability between groups, which then suggests a specific inhibition of cerebral chemo-attraction of T cells by glycyrrhizin. Those modifications were ultimately associated with a reduction in neuronal cell death (fluorojade C staining), as well as improved neurological recovery in GL vs CT groups (mean neurological dysfunction scores at day 3 = 58±13 vs 100±0 %, respectively). Conclusion: HMGB1 is a major mediator of the cerebral early infiltration by T cells following CA. Its inhibition by glycyrrhizin could be a relevant therapeutic target to prevent the propagation of neurological damages.

Aims Argon has been shown to prevent ischaemic injuries in several scenarios of regional ischaemia. We determined whether it could provide a systemic effect in a model of multiorgan failure (MOF) induced by aortic cross-clamping. Methods Anaesthetized rabbits were submitted to aortic cross-clamping (30 min) and subsequent reperfusion (300 min). They were either ventilated with oxygen-enriched air throughout the protocol [fraction of inspired oxygen (FiO2 ) = 30%; control group) or with a mixture of 30% oxygen and 70% argon (argon groups). In a first group treated with argon ('Argon-Total'), its administration was started 30 min before ischaemia and maintained throughout the protocol. In the two other groups, the administration was started either 30 min before ischaemia ('Argon-Pre') or at the onset of reperfusion ('Argon-Post'), for a total duration of 2 h. Cardiovascular, renal and inflammatory endpoints were assessed throughout protocol. Results Compared with control, shock was significantly attenuated in Argon-Total and Argon-Pre but not Argon-Post groups (e.g. cardiac output = 62±5 vs. 29 ± 5 ml min-1 kg-1 in Argon-Total and control groups at the end of the follow-up). Shock and renal failure were reduced in all argon vs. control groups. Histopathological examination of the gut showed attenuation of ischaemic lesions in all argon vs. control groups. Blood transcription levels of interleukin (IL) 1β, IL-8, IL-10 and hypoxia-inducible factor 1α were not significantly different between groups. Conclusion Argon attenuated clinical and biological modifications of cardiovascular, renal and intestinal systems, but not the inflammatory response, after aortic cross-clamping. The window of administration was crucial to optimize organ protection.

Introduction Rapid induction of therapeutic hypothermia is known to prevent neurological sequelae after cardiac arrest. Its mechanism of action could involve a preservation of astrocytes function, which are known to fuel neuron with lactate in stress conditions. Objectives We investigated whether a specific stimulation of astrocyte metabolism by pyruvate administration could induce lactate release and exacerbate the neuronal death as compared to direct stimulation of neurons by lactate administration. Method Eighteen rabbits were anesthetized and instrumented for cerebral microdialysis and evaluation of cerebral consumption of O2, lactate and glucose. After 10 min of ventricular fibrillation and resuscitation, animals received an intravenous infusion of saline (control group, n = 6), sodium lactate (5 mg/kg/min, Lac group, n = 6) or pyruvate (5 mg/kg/min, Py group, n = 6). Neuronal death was quantified by fluorojade C staining after 240 min of follow-up. Results After cardiac arrest, cerebral concentration of lactates and glucose increased in all groups, with a concomitant decreased oxygen consumption and increased lactate and glucose consumption. In the Py group, pyruvate was reduced in lactate as suggested by a significant increase in cerebral lactate concentration in Py group vs others (8.0 ± 0.8, 3.5 ± 0.5 vs 4.4 ± 1.2 μmol/L in Py, Lac and Control groups at 30 min post-cardiac arrest, respectively). This led to a greater neuronal death (25 ± 6, 34 ± 6 vs 50 ± 6 dead neurons per field, in Control, Lac and Py groups, respectively), suggesting that astrocyte fuelling with pyruvate is worse than direct neuronal fuelling with lactate. Conclusion Neuron fuelling with lactate after cardiac arrest is deleterious for neurons. Specific stimulation of astrocytes by pyruvate administration enhances lactate production and worsen the neurological death.

Introduction: Ultra-fast cooling with total liquid ventilation (TLV) is potently protective in animal models of cardiac arrest. Hypothesis: Here, we hypothesized that this protection involves a mitigation of the acute phase of the inflammatory syndrome after cardiac arrest. Methods: Rabbits were anesthetized and submitted to 10 min of ventricular fibrillation. After resuscitation, animals underwent normothermic follow-up (Control, n=6) or ultra-fast cooling by TLV started after resuscitation (TLV, n=6). TLV was used for induction of cooling during 20 min and hypothermia was further maintained during 3 h using external techniques before rewarming. A third group was submitted to a Sham procedure (n=5). Survival and neurological dysfunction were assessed during 3 days. Results: TLV improved the clinical neurological recovery as compared to Control group after cardiac arrest. It was corroborated by histological examination showing an attenuation of neuronal degeneration in parasagittal cortex and hippocampus in TLV vs Control groups. After resuscitation, TLV delayed the elevation of interleukin-6 blood levels as compared to Control after cardiac arrest (e.g., 298±63 vs 991±471 pg/ml at 180 min after cardiac arrest in TLV vs Control, respectively). Blood cytometry analyses showed a massive recruitment of neutrophils and leukocytes (including T4, T8 and B-lymphocytes) in both groups. The early lymphocytosis was attenuated in TLV vs Control groups, despite not achieving statistical significance. Blood levels of high-mobility group box 1 increased rapidly and similarly in both groups after cardiac arrest. This suggests that TLV does not mitigate the early release of danger-associated molecular patterns after resuscitation, which is closely related to the immediate cell death after resuscitation. Altogether, these results show an attenuation of the early inflammatory response during hypothermia, suggesting a role of early but not delayed inflammation in the mechanism of ultra-fast cooling after cardiac arrest. Conclusion: Beneficial effect of hypothermic TLV could be explained by a delay in immune peripheral cells activation and cytokine release, rather than sustained inhibition of inflammation after cardiac arrest.

Introduction Lactate can be used by neurons as a metabolic substrate after an ischemic injury. Though, its consequences on neuronal mortality are still unknown after cardiac arrest. Objective We investigated the neurological consequences of blood lactate after cardiac arrest by administration of exogenous lactate or pyruvate, its main metabolite. Then, we tested the effect of oxamate, which inhibits the reduction of lactate to pyruvate. Method Anesthetized rabbits were submitted to 10 min of ventricular fibrillation and resuscitated. In a first set of experiments, they randomly received saline (Control group, n = 7), lactate (Lac group, 10 mg/kg/min, n = 6) or pyruvate (Pyr group, 10 mg/kg/min, n = 7). In a second set of experiments, they randomly received saline (Control group, n = 7) or oxamate (Oxa group, 37.5 mg/kg/min, n = 6). Animals were followed during 48 h for neurological and survival evaluation. Neuronal death and astrogliosis were quantified by immunostaining (fluorojade C and GFAP, respectively). Results Lactate and pyruvate administration significantly exacerbated blood lactate levels 30 min after cardiac arrest as compared to Control group (15.8 ± 0.8 and 15.0 ± 0.8 vs. 13.1 ± 0.9 mmol/L in Lac, Pyr and Control groups, respectively). This led to a greater neuronal death and neurological dysfunction vs. Control (66 ± 12 and 100 ± 6 vs. 48 ± 8% of neuronal dysfunction after 48 h, in Lac, Pyr and Control groups respectively). Astrogliosis significantly increased after pyruvate infusion vs. other groups (68 ± 5 vs. 49 ± 4 and 54 ± 3 reactive astrocytes per field, in Pyr, Lac and Control groups respectively). In the second set of experiment, oxamate infusion was potently neuroprotective (13 ± 5 vs. 60 ± 10% of neuronal dysfunction after 48 h, in Oxa and Control groups, respectively). Conclusion Lactate and pyruvate administration enhances blood lactate levels and worsen the neurological death while inhibition of lactate dehydrogenase is neuroprotective.

In animal models, whole-body cooling reduces end-organ injury after cardiac arrest and other hypoperfusion states. The benefits of cooling in humans, however, are uncertain, possibly because detrimental effects of prolonged cooling may offset any potential benefit. Total liquid ventilation (TLV) provides both ultrafast cooling and rewarming. In previous reports, ultrafast cooling with TLV potently reduced neurological injury after experimental cardiac arrest in animals. We hypothesized that a brief period of rapid cooling and rewarming via TLV could also mitigate multiorgan failure (MOF) after ischemia-reperfusion induced by aortic cross-clamping.Anesthetized rabbits were submitted to 30 minutes of supraceliac aortic cross-clamping followed by 300 minutes of reperfusion. They were allocated either to a normothermic procedure with conventional ventilation (control group) or to hypothermic TLV (33°C) before, during, and after cross-clamping (pre-clamp, per-clamp, and post-clamp groups, respectively). In all TLV groups, hypothermia was maintained for 75 minutes and switched to a rewarming mode before resumption to conventional mechanical ventilation. End points included cardiovascular, renal, liver, and inflammatory parameters measured 300 minutes after reperfusion.In the normothermic (control) group, ischemia-reperfusion injury produced evidence of MOF including severe vasoplegia, low cardiac output, acute kidney injury, and liver failure. In the TLV group, we observed gradual improvements in cardiac output in post-clamp, per-clamp, and pre-clamp groups versus control (53 ± 8, 64 ± 12, and 90 ± 24 vs 36 ± 23 mL/min/kg after 300 minutes of reperfusion, respectively). Liver biomarker levels were also lower in pre-clamp and per-clamp groups versus control. However, acute kidney injury was prevented in pre-clamp, and to a limited extent in per-clamp groups, but not in the post-clamp group. For instance, creatinine clearance was 4.8 ± 3.1 and 0.5 ± 0.6 mL/kg/min at the end of the follow-up in pre-clamp versus control animals (P = .0004). Histological examinations of the heart, kidney, liver, and jejunum in TLV and control groups also demonstrated reduced injury with TLV.A brief period of ultrafast cooling with TLV followed by rapid rewarming attenuated biochemical and histological markers of MOF after aortic cross-clamping. Cardiovascular and liver dysfunctions were limited by a brief period of hypothermic TLV, even when started after reperfusion. Conversely, acute kidney injury was limited only when hypothermia was started before reperfusion. Further work is needed to determine the clinical significance of our results and to identify the optimal duration and timing of TLV-induced hypothermia for end-organ protection in hypoperfusion states.

Introduction: Hypothermic total liquid ventilation (TLV) has been shown to be highly protective in adult models of cardiac arrest. Hypothesis: TLV could also provide benefits through ultrafast cooling during neonatal cardiac arrest and subsequent hypoxic-ischemic encephalopathy in piglets. Methods: Newborn piglets were anesthetized and submitted to 30 min of hypoxia (FiO 2 =10%) followed by 7 min of asphyxia. After resucitation, animals underwent either normothermic follow-up (38°C; Control, n=6) or ultra-fast cooling by TLV (TLV, n=6). TLV was implemented during 30 min for cooling induction and hypothermia was further maintained during 3 h using external techniques before rewarming. A third group of piglets was submitted to a Sham procedure (n=4) with neither hypoxia nor ischemia. All groups underwent mechanical ventilation during 6-8 h before awakening. Survival and neurological dysfunction were assessed during 7 days. Animals were then euthanized and histological brain damages were assessed (fluorojade-C staining). Results: After hypoxia-ischemia, Control and TLV animals presented marked metabolic acidosis and lactate levels elevation as compared to Sham (e.g., pH=6.91±0.05, 6.93±0.02 vs 7.33±0.05 at t=30 min after ischemia in Control, TLV and Sham, respectively; p Conclusion: Hypothermic TLV improves neurological recovery in a swine model of neonatal cardiac arrest and hypoxic-ischemic encephalopathy when started early after resuscitation.

Background Ultrafast cooling by total liquid ventilation (TLV) provides potent cardio- and neuroprotection after experimental cardiac arrest. However, this was evaluated in animals with no initial lung injury, whereas out-of-hospital cardiac arrest is frequently associated with early-onset pneumonia, which may lead to acute respiratory distress syndrome (ARDS). Here, our objective was to determine whether hypothermic TLV could be safe or even beneficial in an aspiration-associated ARDS animal model. Methods ARDS was induced in anesthetized rabbits through a two-hits model including the intra-tracheal administration of a pH = 1 solution mimicking gastric content and subsequent gaseous non-protective ventilation during 90 min (tidal volume [Vt] = 10 ml/kg with positive end-expiration pressure [PEEP] = 0 cmH2O). After this initial period, animals either received lung protective gas ventilation (LPV; Vt = 8 ml/kg and PEEP = 5 cmH2O) under normothermic conditions, or hypothermic TLV (TLV; Vt = 8 ml/kg and end-expiratory volume = 15 ml/kg). Both strategies were applied for 120 min with a continuous monitoring of respiratory and cardiovascular parameters. Animals were then euthanized for pulmonary histological analyses. Results Eight rabbits were included in each group. Before randomization, all animals elicited ARDS with arterial oxygen partial pressure over inhaled oxygen fraction ratios (PaO2/FiO2) below 100 mmHg, as well as decreased lung compliance. After randomization, body temperature rapidly decreased in TLV versus LPV group (32.6 ± 0.6 vs. 38.2 ± 0.4 °C after 15 min). Static lung compliance and gas exchanges were not significantly different in the TLV versus LPV group (PaO2/FiO2 = 62 ± 4 vs. 52 ± 8 mmHg at the end of the procedure, respectively). Mean arterial pressure and arterial bicarbonates levels were significantly higher in TLV versus LPV. Histological analysis also showed significantly lower inflammation in TLV versus LPV group (median histological score = 3 vs. 4.5/5, respectively; p = 0.03). Conclusion Hypothermic TLV can be safely induced in rabbits during aspiration-associated ARDS. It modified neither gas exchanges nor respiratory mechanics but reduced lung inflammation and hemodynamic failure in comparison with LPV. Since hypothermic TLV was previously shown to provide neuro- and cardio protective effects after cardiac arrest, these findings suggest a possible use of TLV in the settings of cardiac arrest-associated ARDS.

Sudden death in ambulatory is a major public health issue: only few survivors, severe brain damage, high socio-economic cost. To improve survival and neurological recovery of these patients, an early therapeutic moderate hypothermia could be promising, as strongly suggested by previous preclinical studies on small animals through hypothermic total liquid ventilation (TLV) with perfluorocarbons (PFC) that maintain normal gas exchanges, and where lungs act as a heat exchanger (INSERM U955-E3, partner and pioneer of this project). Before translation of hypothermic TLV to humans, studies on large animals are necessary. The project ABYSS concerns the development and validation of a total liquid ventilator prototype suitable for large animals (no suitable devices exist on the market). ABYSS involves a consortium of 4 partners: an industrial company (Bertin Technologies) and three academic laboratories (INSERM U955-E3, INSERM U955-E13 and IR4M CNRS UMR8081). The study, which lasted three years, has led to: 1) Realize a prototype of total liquid ventilator for ventilating and cooling large animals, 2) Study the cooling on large animals with TLV, both on beating heart and under external cardiac massage, 3) Study another therapeutic indication: organ preservation of dead patients, 4) Compare three PFC already used as medical devices and analyze the impact of using PFCs with quite unusual physical properties on respiratory flows and airway resistance, 5) Study the miniaturization of the ventilator to enable its use in mobile intensive care unit. The next task will be to improve the understanding of the broncho-alveolar response (at various scales from organ to pulmonary cells) under total liquid ventilation on large animals, in order to get knowledge to improve and to optimize the tolerance of the respiratory system to liquid ventilation with PFC.

Background Extracorporeal cardiopulmonary resuscitation ( ECPR ) is widely proposed for the treatment of refractory cardiac arrest. It should be associated with coronary angiography if coronary artery disease is suspected. However, the prioritization of care remains unclear in this situation. Our goal was to determine whether coronary reperfusion should be instituted as soon as possible in such situations in a pig model. Methods and Results Anesthetized pigs were instrumented and submitted to coronary artery occlusion and ventricular fibrillation. After 5 minutes of untreated cardiac arrest, conventional cardiopulmonary resuscitation ( CPR ) was started. Fifteen minutes later, ECPR was initiated for a total duration of 240 minutes. Animals randomly underwent either early or late coronary reperfusion at 20 or 120 minutes of ECPR , respectively. This timing was adapted to the kinetic of infarct extension in pigs. Return of spontaneous circulation was determined as organized electrocardiogram rhythm with systolic arterial pressure above 80 mm Hg. During conventional CPR , hemodynamic parameters were not different between groups. Carotid blood flow then increased by 70% after the onset of ECPR in both groups. No animal (0 of 7) elicited return of spontaneous circulation after late reperfusion versus 4 of 7 after early reperfusion ( P =0.025). The hemodynamic parameters, such as carotid blood flow, were also improved in early versus late reperfusion groups (113±20 vs 43±17 mL/min after 240 minutes of ECPR , respectively; P =0.030), along with infarct size decrease (71±4% vs 84±2% of the risk zone, respectively; P =0.013). Conclusions Early reperfusion improved hemodynamic status and facilitated return of spontaneous circulation in a porcine model of ischemic cardiac arrest treated by ECPR .

Background Mitochondrial dysfunction is critical following ischemic disorders. Our goal was to determine whether mild hypothermia could limit this dysfunction through per-ischemic inhibition of reactive oxygen species (ROS) generation. Methods First, ROS production was evaluated during simulated ischemia in an vitro model of isolated rat cardiomyocytes at hypothermic (32°C) vs. normothermic (38°C) temperatures. Second, we deciphered the direct effect of hypothermia on mitochondrial respiration and ROS production in oxygenated mitochondria isolated from rabbit hearts. Third, we investigated these parameters in cardiac mitochondria extracted after 30-min of coronary artery occlusion (CAO) under normothermic conditions (CAO-N) or with hypothermia induced by liquid ventilation (CAO-H; target temperature: 32°C). Results In isolated rat cardiomyocytes, per-ischemic ROS generation was dramatically decreased at 32 vs. 38°C ( e.g. , −55±8% after 140min of hypoxia). In oxygenated mitochondria isolated from intact rabbit hearts, hypothermia also improved respiratory control ratio (+22±3%) and reduced H 2 O 2 production (−41±1%). Decreased oxidative stress was further observed in rabbit hearts submitted to hypothermic vs. normothermic ischemia (CAO-H vs. CAO-N), using thiobarbituric acid-reactive substances as a marker. This was accompanied by a preservation of the respiratory control ratio as well as the activity of complexes I, II and III in cardiac mitochondria. Conclusion The cardioprotective effect of mild hypothermia involves a direct effect on per-ischemic ROS generation and results in preservation of mitochondrial function. This might explain why the benefit afforded by hypothermia during regional myocardial ischemia depends on how fast it is instituted during the ischemic process.

Mild hypothermia (32°C-34°C) exerts a potent cardioprotection in animal models of myocardial infarction. Recently, it has been proposed that this beneficial effect is related to survival signaling. We, therefore, hypothesized that the well-known cardioprotective pathways dependent on adenosine and/or opioid receptors could be the trigger of hypothermia-induced salvage. Open-chest rabbits were accordingly exposed to 30 minutes of coronary artery occlusion (CAO) under normothermic (NT) or hypothermic ([HT] 32°C) conditions. In the latter, hypothermia was induced by total liquid ventilation with temperature-controlled perfluorocarbons in order to effect ultrafast cooling and to accurately control cardiac temperature. After 4 hours of reperfusion, infarct and no-reflow zone sizes were assessed and quantified as a percentage of the risk zone. In animals experiencing HT ischemia, the infarct size was dramatically reduced as compared to NT animals (9% ± 3% vs 55% ± 2% of the risk zone, respectively). Importantly, administration of opioid and adenosine receptor antagonists (naloxone [6 mg/kg iv] and 8-( p-sulfophenyl) theophylline [20 mg/kg iv], respectively) did not alter the infarct size or affect the cardioprotective effect of hypothermia. Doses of these 2 antagonists were appropriately chosen since they blunted infarct size reduction induced by selective opioid or adenosine receptor stimulation with morphine (0.3 mg/kg iv) or N6-cyclopentyladenosine ([CPA] 100 μg/kg iv), respectively. Therefore, the cardioprotective effect of mild hypothermia is not triggered by either opioid or adenosine receptor activation, suggesting the involvement of other cardioprotective pathways.

Introduction Hypoxic-ischemic encephalopathy is a frequent and unexpected birth complication causing major neurological disorders in newborn infants. Objectives Our goal was to elaborate a standardized protocol of hypoxia-ischemia in piglets for the further evaluation of innovating cardio- and neuroprotective strategies. Method Newborn piglets were anesthetized and submitted to 30 min of hypoxia (FiO2 = 10%) followed by ischemia induced by 7 minutes of respiratory arrest (HI group). Cardiopulmonary resuscitation was instituted through external cardiac massage and epinephrine administration (4 μg/kg, i.v.). Another group of piglets was submitted to a Sham procedure with neither hypoxia nor ischemia. In both groups, animals were maintained under mechanical ventilation during 6 hours. After weaning, survival and neurological dysfunction were assessed during 7 days. Animals were then euthanized and histologic damage was assessed in the brain (HE and fluorojade-B staining). Results Eight and four animals were submitted to HI or Sham procedure, respectively. In the HI group, a severe bradycardia and hypotension was observed at the end of the ischemic period (mean arterial pressure = 28 ± 2 vs. 59 ± 3 mmHg in HI vs. Sham, respectively; P Conclusion This model is suitable for the evaluation of new protective therapies after neonatal asphyxia.

Introduction Total liquid ventilation (TLV) can cool down the entire body within 10–15 min in small animals. Our goal was to determine whether it could also induce ultra-fast and whole-body cooling in large animals using a specifically dedicated liquid ventilator. Cooling efficiency was evaluated under physiological conditions (beating-heart) and during cardiac arrest with automated chest compressions (CC, intra-arrest). Methods In a first set of experiments, beating-heart pigs were randomly submitted to conventional mechanical ventilation or hypothermic TLV with perfluoro-N-octane (between 15 and 32 °C). In a second set of experiments, pigs were submitted to ventricular fibrillation and CC. One group underwent continuous CC with asynchronous conventional ventilation (Control group). The other group was switched to TLV while pursuing CC for the investigation of cooling capacities and potential effects on cardiac massage efficiency. Results Under physiological conditions, TLV significantly decreased the entire body temperatures below 34 °C within only 10 min. As examples, cooling rates averaged 0.54 and 0.94 °C/min in rectum and esophageous, respectively. During cardiac arrest, TLV did not alter CC efficiency and cooled the entire body below 34 °C within 20 min, the low-flow period slowing cooling during CC. Conclusion Using a specifically designed liquid ventilator, TLV induced a very rapid cooling of the entire body in large animals. This was confirmed in both physiological conditions and during cardiac arrest with CC. TLV could be relevant for ultra-rapid cooling independently of body weight.

Total liquid ventilation provides ultrafast and potently neuro- and cardioprotective cooling after shockable cardiac arrest and myocardial infarction in animals. Our goal was to decipher the effect of hypothermic total liquid ventilation on the systemic and cerebral response to asphyxial cardiac arrest using an original pressure- and volume-controlled ventilation strategy in rabbits.Randomized animal study.Academic research laboratory.New Zealand Rabbits.Thirty-six rabbits were submitted to 13 minutes of asphyxia, leading to cardiac arrest. After resumption of spontaneous circulation, they underwent either normothermic life support (control group, n = 12) or hypothermia induced by either 30 minutes of total liquid ventilation (total liquid ventilation group, n = 12) or IV cold saline (conventional cooling group, n = 12).Ultrafast cooling with total liquid ventilation (32 °C within 5 min in the esophagus) dramatically attenuated the post-cardiac arrest syndrome regarding survival, neurologic dysfunction, and histologic lesions (brain, heart, kidneys, liver, and lungs). Final survival rate achieved 58% versus 0% and 8% in total liquid ventilation, control, and conventional cooling groups (p0.05), respectively. This was accompanied by an early preservation of the blood-brain barrier integrity and cerebral hemodynamics as well as reduction in the immediate reactive oxygen species production in the brain, heart, and kidneys after cardiac arrest. Later on, total liquid ventilation also mitigated the systemic inflammatory response through alteration of monocyte chemoattractant protein-1, interleukin-1β, and interleukin-8 transcripts levels compared with control. In the conventional cooling group, cooling was achieved more slowly (32 °C within 90-120 min in the esophagus), providing none of the above-mentioned systemic or organ protection.Ultrafast cooling by total liquid ventilation limits the post-cardiac arrest syndrome after asphyxial cardiac arrest in rabbits. This protection involves an early limitation in reactive oxidative species production, blood-brain barrier disruption, and delayed preservation against the systemic inflammatory response.

International audience; BACKGROUND: Therapeutic hypothermia was shown to facilitate resumption of spontaneous circulation when instituted during cardiac arrest. Here, we investigated whether it directly improved the chance of successful resuscitation independently of adrenaline administration in rabbits. We further evaluated the direct effect of hypothermia on vascular function in vitro. METHODS: In a first set of experiments, four groups of anesthetized rabbits were submitted to 15 min of cardiac arrest and subsequent cardiopulmonary resuscitation (CPR). The "control" group underwent CPR with only cardiac massage and defibrillation attempts. Two other groups received cold or normothermic saline infusion during CPR (20 mL/kg of NaCl 0.9% at 4°C or 38°C, respectively). In a last group, the animals received adrenaline (15 µg/kg intravenously) during CPR. In a second set of experiments, we evaluated at 32°C vs. 38°C the vascular function of aortic rings withdrawn from healthy rabbits or after cardiac arrest. RESULTS: In the first set of experiments, cardiac massage efficiency was improved by adrenaline but neither by hypothermic nor normothermic saline administration. Resumption of spontaneous circulation was observed in five of eight animals after adrenaline as compared with none of eight in other groups. Defibrillation rates were conversely similar among groups (7/8 or 8/8). In the second set of experiments, in vitro hypothermia (32°C) was not able to prevent the dramatic alteration of vascular function observed after cardiac arrest. It also did not directly modify vasocontractile or the vasodilating functions in healthy conditions. CONCLUSION: In rabbits, hypothermia did not exert a direct hemodynamic or vascular effect that might explain its beneficial effect during CPR.

International audience; OBJECTIVES: Ultrafast and whole-body cooling can be induced by total liquid ventilation with temperature-controlled perfluorocarbons. Our goal was to determine whether this can afford maximal cardio- and neuroprotections through cooling rapidity when coronary occlusion is complicated by cardiac arrest. DESIGN: Prospective, randomized animal study. SETTING: Academic research laboratory. SUBJECTS: Male New Zealand rabbits. INTERVENTIONS: Chronically instrumented rabbits were submitted to coronary artery occlusion and ventricular fibrillation. After 8 minutes of cardiac arrest, animals were resuscitated and submitted to a normothermic follow-up (control group) or to 3 hours of mild hypothermia induced by total liquid ventilation (total liquid ventilation group) or by combination of cold saline infusion and cold blankets application (saline group). Coronary reperfusion was permitted 40 minutes after the onset of occlusion. After awakening, rabbits were followed up during 7 days. MEASUREMENTS AND MAIN RESULTS: Ten animals were resuscitated in each group. In the control group, all animals secondarily died of cardiac/respiratory failure (8 of 10) or neurological dysfunction (2 of 10). In the saline group, the target temperature of 32°C was achieved within 30-45 minutes after cooling initiation. This slightly reduced infarct size versus control (41% ± 16% vs 54% ± 8% of risk zone, respectively; p < 0.05) but failed to significantly improve cardiac output, neurological recovery, and survival rate (three survivors, six death from cardiac/respiratory failure, and one from neurological dysfunction). Conversely, the 32°C temperature was achieved within 5-10 minutes in the total liquid ventilation group. This led to a dramatic reduction in infarct size (13% ± 4%; p < 0.05 vs other groups) and improvements in cardiac output, neurological recovery, and survival (eight survivors, two deaths from cardiac/respiratory failure). CONCLUSIONS: Achieving hypothermia rapidly is critical to improve the cardiovascular outcome after cardiac arrest with underlying myocardial infarction.

Introduction L’administration intrapulmonaire de perfluorocarbones par ventilation liquide totale (VLT) permet un refroidissement ultra-rapide tout en maintenant les echanges gazeux. La VLT hypothermisante (VLTH) a montre des effets benefiques neurologiques et cardiaques dans des modeles animaux de choc et d’arret cardiaque. L’objectif de ce travail etait d’etudier son interet sur l’atteinte motrice des membres inferieurs dans un modele d’ischemie-reperfusion medullaire par clampage aortique. Nous avons evalue l’effet de la profondeur de l’hypothermie (33 vs 36 °C) et de la severite de l’ischemie (15 vs 20 minutes). Materiel et methodes Des lapins ont ete anesthesies, instrumentes et soumis a une ischemie medullaire par clampage de l’aorte abdominale infra-renale pendant 15 ou 20 min. Ils ont ensuite aleatoirement subi une procedure « temoin » (ventilation conventionnelle et normothermie a 38,5 °C) ou une VLTH avec des temperatures cibles de 33 °C ou 36 °C. La VLTH etait debutee immediatement apres la reperfusion (declampage). Apres 30 min de VLTH, l’hypothermie etait maintenue durant 120 min avant de rechauffer les animaux (1 °C/h) et de les reveiller. L’evaluation neurologique etait conduite 48 h apres l’ischemie medullaire a l’aide du score de Tarlov (0 : paraplegie totale ; 5 : fonction motrice normale). Resultats Trente animaux ont ete inclus dans cette etude ( n = 5 par groupe). En conditions temoin, tous les animaux presentaient une paraplegie totale avec un score de Tarlov egal a 0, quelle que soit la duree de l’ischemie initiale (15 ou 20 min). Dans les groupes VLTH, la temperature cible etait atteinte tres rapidement, c’est-a-dire en moins 15-20 min dans tout l’organisme apres la reperfusion. Apres 15 min d’ischemie, la VLTH apportait une amelioration significative de l’atteinte motrice par rapport au groupe temoin, quelle que soit la temperature etudiee (Fig. 1 : * p Discussion En cas d’ischemie-reperfusion medullaire de gravite moderee, l’hypothermie ultra-rapide induite par VLT permet d’attenuer la souffrance neurologique quelle que soit la temperature cible. A contrario, une temperature plus basse semble necessaire pour obtenir un benefice en cas d’ischemie-reperfusion medullaire plus severe. L’hypothermie par VLT pourrait ouvrir des perspectives de protection en cas d’atteinte medullaire post-operatoire lors des chirurgies aortiques majeures.

International audience; Background: The respiratory properties of perfluorocarbons (PFC) have been widely studied for liquid ventilation inhumans and animals. Several PFC were tested but their tolerance may depend on the species. Here, the effects of asingle administration of liquid PFC into pig lungs were assessed and compared. Three different PFC having distinctevaporative and spreading coefficient properties were evaluated (Perfluorooctyl bromide [PFOB], perfluorodecalin[PFD] and perfluoro-N-octane [PFOC]).Methods: Pigs were anesthetized and submitted to mechanical ventilation. They randomly received an intra-trachealadministration of 15 ml/kg of either PFOB, PFD or PFOC with 12 h of mechanical ventilation before awakening andweaning from ventilation. A Control group was submitted to mechanical ventilation with no PFC administration. Allanimals were followed during 4 days after the initial PFC administration to investigate gas exchanges and clinicalrecovery. They were ultimately euthanized for histological analyses and assessment of PFC residual concentrationswithin the lungs using dual nuclei fluorine and hydrogen Magnetic Resonance Imaging (MRI). Sixteen animals wereincluded (4/group).Results: In the PFD group, animals tended to be hypoxemic after awakening. In PFOB and PFOC groups, blood gaseswere not significantly different from the Control group after awakening. The poor tolerance of PFD was likely related toa large amount of residual PFC, as observed using MRI in all lung samples (≈10% of lung volume). This percentage waslower in the PFOB group (≈1%) but remained significantly greater than in the Control group. In the PFOC group, thepercentage of residual PFC was not significantly different from that of the Control group (≈0.1%). Histologically, themost striking feature was an alveolar infiltration with foam macrophages, especially in the groups treated by PFD orPFOB.Conclusions: Of the three tested perfluorocarbons, PFOC offered the best tolerance in terms of lung function, gasexchanges and residuum in the lung. PFOC was rapidly cleared from the lungs and virtually disappeared after 4 dayswhereas PFOB persisted at significant levels and led to foam macrophage infiltration. PFOC could be relevant for shortterm total liquid ventilation with a rapid weaning.

Background: Total liquid ventilation (TLV) with perfluorocarbons has been shown to induce rapid protective cooling in animal models of myocardial ischemia and cardiac arrest, with improved neurological and cardiovascular outcomes after resuscitation. In this study, the authors hypothesized that hypothermic TLV can also limit kidney injury after cardiac arrest. Methods: Anesthetized rabbits were submitted to 15 min of untreated ventricular fibrillation. After resuscitation, three groups of eight rabbits each were studied such as (1) life support plus hypothermia (32°–33°C) induced by cold TLV (TLV group), (2) life support without hypothermia (control group), and (3) Sham group (no cardiac arrest). Life support was continued for 6 h before euthanasia and kidney removal. Results: Time to target esophageal temperature was less than 5 min in the TLV group. Hypothermia was accompanied by preserved renal function in the TLV group as compared with control group regarding numerous markers including creatinine blood levels (12 ± 1 vs. 16 ± 2 mg/l, respectively; mean ± SEM), urinary N-acetyl-β-(d)-glucosaminidase (1.70 ± 0.11 vs. 3.07 ± 0.10 U/mol of creatinine), γ-glutamyltransferase (8.36 ± 0.29 vs. 12.96 ± 0.44 U/mol of creatinine), or β2-microglobulin (0.44 ± 0.01 vs. 1.12 ± 0.04 U/mol of creatinine). Kidney lesions evaluated by electron microscopy and conventional histology were also attenuated in TLV versus control groups. The renal-protective effect of TLV was not related to differences in delayed inflammatory or immune renal responses because transcriptions of, for example, interferon-γ, tumor necrosis factor-α, interleukin-1β, monocyte chemoattractant protein-1, toll-like receptor-2, toll-like receptor-4, and vascular endothelial growth factor were similarly altered in TLV and control versus Sham. Conclusion: Ultrafast cooling with TLV is renal protective after cardiac arrest and resuscitation, which could increase kidney availability for organ donation.

Background— In animal models of cardiac arrest, the benefit afforded by hypothermia is closely linked to the rapidity of the decrease in body temperature after resuscitation. Because total liquid ventilation (TLV) with temperature-controlled perfluorocarbons induces a very rapid and generalized cooling, we aimed to determine whether this could limit the post–cardiac arrest syndrome in a rabbit model. We especially focused on neurological, cardiac, pulmonary, liver and kidney dysfunctions. Methods and Results— Anesthetized rabbits were submitted to either 5 or 10 minutes of untreated ventricular fibrillation. After cardiopulmonary resuscitation and resumption of a spontaneous circulation, the animals underwent either normothermic life support (control) or therapeutic hypothermia induced by TLV. The latter procedure decreased esophageal and tympanic temperatures to 32°C to 33°C within only 10 minutes. After rewarming, the animals submitted to TLV exhibited an attenuated neurological dysfunction and decreased mortality 7 days later compared with control. The neuroprotective effect of TLV was confirmed by a significant reduction in brain histological damages. We also observed limitation of myocardial necrosis, along with a decrease in troponin I release and a reduced myocardial caspase 3 activity, with TLV. The beneficial effects of TLV were directly related to the rapidity of hypothermia induction because neither conventional cooling (cold saline infusion plus external cooling) nor normothermic TLV elicited a similar protection. Conclusions— Ultrafast cooling instituted by TLV exerts potent neurological and cardiac protection in an experimental model of cardiac arrest in rabbits. This could be a relevant approach to provide a global and protective hypothermia against the post–cardiac arrest syndrome.

International audience; STUDY AIM: Total liquid ventilation (TLV) with cooled perfluorocarbons has been demonstrated to induce an ultrafast cardioprotective cooling in rabbits. However, it remains unknown whether this technically challenging strategy would be actually more potent than a conventional external cooling after a prolonged ischemia inducing transmural myocardial infarction. METHODS: Anesthetized rabbits were randomly submitted to 60min of coronary artery occlusion (CAO) under normothermic conditions (Control group, n=7) or with cooling started at the 5th min of CAO (target left atrial temperature: 32 degrees C). Cooling procedures were either external cooling using cold blankets (EC group, n=7) or ultrafast cooling initiated by 20min of TLV (TLV group, n=6). An additional group underwent a similar ultrafast cooling protocol started at the 20th min of CAO (TLV(delayed) group, n=6). After reperfusion, all hypothermic animals were rewarmed and infarct size was assessed after 4h. RESULTS: In the EC group, the target temperature was reached only at 60min of CAO whereas this time-interval was dramatically reduced to 15 and 25min of CAO in TLV and TLV(delayed), respectively. Infarct sizes were significantly reduced in TLV and TLV(delayed) but not in EC groups as compared to Control (45+/-18%, 58+/-5%, 78+/-10% and 82+/-7% of the risk zone, respectively). Similar significant differences were observed for the sizes of the no-reflow zones (15+/-9%, 23+/-8%, 49+/-11% and 58+/-13% of the risk zone, respectively). CONCLUSION: Cooling induced by TLV afforded a potent cardioprotection and prevented transmural infarction following prolonged and severe ischemia, even when started later than a surface cooling in rabbits.

International audience; AIMS: We investigated whether rapid cooling instituted by total liquid ventilation (TLV) improves cardiac and mitochondrial function in rabbits submitted to ischaemia-reperfusion. METHODS AND RESULTS: Rabbits were chronically instrumented with a coronary artery occluder and myocardial ultrasonic crystals for assessment of segment length-shortening. Two weeks later they were re-anaesthetized and underwent either a normothermic 30-min coronary artery occlusion (CAO) (Control group, n = 7) or a comparable CAO with cooling initiated by a 10-min hypothermic TLV and maintained by a cold blanket placed on the skin. Cooling was initiated after 5 or 15 min of CAO (Hypo-TLV and Hypo-TLV(15') groups, n = 6 and 5, respectively). A last group underwent normothermic TLV during CAO (Normo-TLV group, n = 6). Wall motion was measured in the conscious state over three days of reperfusion before infarct size evaluation and histology. Additional experiments were done for myocardial sampling in anaesthetized rabbits for mitochondrial studies. The Hypo-TLV procedure induced a rapid decrease in myocardial temperature to 32-34 degrees C. Throughout reperfusion, segment length-shortening was significantly increased in Hypo-TLV and Hypo-TLV(15') vs. Control and Normo-TLV (15.1 +/- 3.3%, 16.4 +/- 2.3%, 1.8 +/- 0.6%, and 1.1 +/- 0.8% at 72 h, respectively). Infarct sizes were also considerably attenuated in Hypo-TLV and Hypo-TLV(15') vs. Control and Normo-TLV (4 +/- 1%, 11 +/- 5%, 39 +/- 2%, and 42 +/- 5% infarction of risk zones, respectively). Mitochondrial function in myocardial samples obtained at the end of ischaemia or after 10 min of reperfusion was improved by Hypo-TLV with respect to ADP-stimulated respiration and calcium-induced opening of mitochondrial permeability transition pores (mPTP). Calcium concentration opening mPTP was, e.g., increased at the end of ischaemia in the risk zone in Hypo-TLV vs. Control (157 +/- 12 vs. 86 +/- 12 microM). Histology and electron microscopy also revealed better preservation of lungs and of cardiomyocyte ultrastructure in Hypo-TLV when compared with Control. CONCLUSION: Institution of rapid cooling by TLV during ischaemia reduces infarct size as well as other sequelae of ischaemia, such as post-ischaemic contractile and mitochondrial dysfunction.

Introduction: Total liquid ventilation with temperature-controlled perfluorocarbons induces an ultra-fast cardioprotective cooling when instituted during a 30-min coronary artery occlusion (CAO) in rabbits. Hypothesis: We hypothesized that ultra-fast hypothermia instituted with a short total liquid ventilation episode would be still beneficial after a prolonged CAO as compared to conventional low rate surface cooling. Methods: Anesthetized rabbits underwent a 60-min CAO followed by 4 hours of reperfusion before infarct size and no reflow evaluations. Rabbits randomly underwent either a normothermic CAO (Control group, n=7) or cooling from 5th min of CAO to the end of CAO (target left atrial temperature: 32°C). Cooling procedures were either low rate surface cooling (LRC) using ice-filled cold blankets (LRC group, n=7) or ultra-fast cooling (UFC) initiated by 20 min of hypothermic total liquid ventilation and maintained if necessary by cold blankets (UFC group, n=6). An additional group underwent a similar ultra-fast cooling protocol started at the 20th min of CAO (UFC-delayed group, n=6). After reperfusion, all hypothermic animals were rewarmed. Results: Left atrial temperature was similar in all groups at baseline (Table ). Hypothermia was modest in LRC vs UFC and UFC-delayed groups at 30-min CAO but reached similar level at the end of ischemia (i.e., 60-min CAO). Interestingly, no reflow and infarct sizes were only significantly reduced in UFC and UFC-delayed but not in LRC groups as compared to Control. Infarct size reduction was significantly better predicted by the integrated decrease in left atrial temperature throughout ischemia than by the temperature at the end of ischemia. Conclusion: Ultra-fast cooling induced by total liquid ventilation afforded cardioprotection against prolonged ischemia in rabbits, even when instituted later than a low rate surface cooling. Left atrial temperature (LAT) at different times of the protocol and infarct and no reflow sizes