Total Liquid Ventilation Group Research Articles

Ultrafast Cooling With Total Liquid Ventilation Mitigates Early Inflammatory Response and Offers Neuroprotection in aPorcine Model of Cardiac Arrest.

Brain injury is one of the most serious complications after cardiac arrest (CA). To prevent this phenomenon, rapid cooling with total liquid ventilation (TLV) has been proposed in small animal models of CA (rabbits and piglets). Here, we aimed to determine whether hypothermic TLV can also offer neuroprotection and mitigate cerebral inflammatory response in large animals. Anesthetized pigs were subjected to 14 minutes of ventricular fibrillation followed by cardiopulmonary resuscitation. After return of spontaneous circulation, animals were randomly subjected to normothermia (control group, n=8) or ultrafast cooling with TLV (TLV group, n=8). In the latter group, TLV was initiated within a window of 15 minutes after return of spontaneous circulation and allowed to reduce tympanic, esophageal, and bladder temperature to the 32 to 34 °C range within 30 minutes. After 45 minutes of TLV, gas ventilation was resumed, and hypothermia was maintained externally until 3 hours after CA, before rewarming using heat pads (0.5 °C-1 °C/h). After an additional period of progressive rewarming for 3 hours, animals were euthanized for brain withdrawal and histological analysis. At the end of the follow-up (ie, 6 hours after CA), histology showed reduced brain injury as witnessed by the reduced number of Fluroro-Jade C-positive cerebral degenerating neurons in TLV versus control. IL (interleukin)-1ra and IL-8 levels were also significantly reduced in the cerebrospinal fluid in TLV versus control along with cerebral infiltration by CD3+ cells. Conversely, circulating levels of cytokines were not different among groups, suggesting a discrepancy between local and systemic inflammatory levels. Ultrafast cooling with TLV mitigates neuroinflammation and attenuates acute brain lesions in the early phase following resuscitation in large animals subjected to CA.

Abstract 19: Ultra-Fast Cooling Induced by Total Liquid Ventilation Provides Neuroprotection Through a Delay in the Acute Systemic Inflammatory Response After Cardiac Arrest in Rabbits

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.

Protection against cardiac ischemia-reperfusion injury by hypothermia and by inhibition of succinate accumulation and oxidation is additive

Hypothermia induced at the onset of ischemia is a potent experimental cardioprotective strategy for myocardial infarction. The aim of our study was to determine whether the beneficial effects of hypothermia may be due to decreasing mitochondria-mediated mechanisms of damage that contribute to the pathophysiology of ischemia/reperfusion injury. New Zealand male rabbits were submitted to 30 min of myocardial ischemia with hypothermia (32 °C) induced by total liquid ventilation (TLV). Hypothermia was applied during ischemia alone (TLV group), during ischemia and reperfusion (TLV-IR group) and normothermia (Control group). In all the cases, ischemia was performed by surgical ligation of the left anterior descending coronary artery and was followed by 3 h of reperfusion before assessment of infarct size. In a parallel study, male C57BL6/J mice underwent 30 min myocardial ischemia followed by reperfusion under either normothermia (37 °C) or conventionally induced hypothermia (32 °C). In both the models, the levels of the citric acid cycle intermediate succinate, mitochondrial complex I activity were assessed at various times. The benefit of hypothermia during ischemia on infarct size was compared to inhibition of succinate accumulation and oxidation by the complex II inhibitor malonate, applied as the pro-drug dimethyl malonate under either normothermic or hypothermic conditions. Hypothermia during ischemia was cardioprotective, even when followed by normothermic reperfusion. Hypothermia during ischemia only, or during both, ischemia and reperfusion, significantly reduced infarct size (2.8 ± 0.6%, 24.2 ± 3.0% and 49.6 ± 2.6% of the area at risk, for TLV-IR, TLV and Control groups, respectively). The significant reduction of infarct size by hypothermia was neither associated with a decrease in ischemic myocardial succinate accumulation, nor with a change in its rate of oxidation at reperfusion. Similarly, dimethyl malonate infusion and hypothermia during ischemia additively reduced infarct size (4.8 ± 2.2% of risk zone) as compared to either strategy alone. Hypothermic cardioprotection is neither dependent on the inhibition of succinate accumulation during ischemia, nor of its rapid oxidation at reperfusion. The additive effect of hypothermia and dimethyl malonate on infarct size shows that they are protective by distinct mechanisms and also suggests that combining these different therapeutic approaches could further protect against ischemia/reperfusion injury during acute myocardial infarction.

Abstract 201: Neuroprotective Effect of Hypothermic Total Liquid Ventilation in Newborn Piglets Subjected to Neonatal Cardiac Arrest

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<0.05). Despite a trend toward reduced mortality, survival was not significantly different between TLV and Control groups at the end of the survival follow-up (survival = 0/6, 3/6 and 3/4 in Control, TLV and Sham groups). Nevertheless, neurological dysfunction was significantly reduced in TLV as compared to Control (median scores = 23% vs 87 at day 2, respectively; Sham value = 0%). Blood levels of the brain injury biomarker protein S100B were also reduced at the time of euthanasia in TLV vs Control. Fluoro-jade C staining showed a significantly lower number of degenerating neurons in TLV vs Control (e.g., medians = 17 vs 39 degenerating neurons per field in caudate nucleus, respectively; Sham value = 1). Conclusion: Hypothermic TLV improves neurological recovery in a swine model of neonatal cardiac arrest and hypoxic-ischemic encephalopathy when started early after resuscitation.

Targeted Temperature Management With Total Liquid Ventilation After Ischemic Spinal Cord Injury

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. 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. 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. 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.

Hypothermic total liquid ventilation after experimental aspiration-associated acute respiratory distress syndrome

BackgroundUltrafast 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.MethodsARDS 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.ResultsEight 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).ConclusionHypothermic 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.

A Brief Period of Hypothermia Induced by Total Liquid Ventilation Decreases End-Organ Damage and Multiorgan Failure Induced by Aortic Cross-Clamping.

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.

Abstract 11465: Ultrafast Cooling With Total Liquid Ventilation Attenuates Multi-organ Failure and Sepsis-like Response After Experimental Shock Induced by Aortic Cross Clamping

Introduction: Total liquid ventilation (TLV) provides ultrafast cooling and potent neuro- and cardioprotection after experimental cardiac arrest. Hypothesis: We determined whether it could also mitigate multi-organ failure and sepsis-like response after abdominal ischemia/reperfusion and subsequent shock. Methods: Anesthetized rabbits were submitted to 30 min of supracoeliac aortic cross-clamping and 300 min of reperfusion. They underwent a normothermic procedure (Control group) or rapid cooling toward 32-33°C with TLV started either before, during or after aortic clamping (PRE, PER and POST groups, respectively). TLV was maintained during 75 min after which rabbits were rapidly rewarmed and switched to conventional mechanical ventilation. Results: Control animals elicited a dramatic shock state with a low cardiac output, high demand in norepinephrine, liver failure and acute kidney injury. Cardiac output was gradually improved in POST, PER and PRE groups as compared to Control (53±3, 64±5, 90±10 and 36±8 ml/min/kg after 300 min, respectively; all p<0.05). A significant protection was also observed in the TLV groups regarding liver enzymes (ASAT, ALAT, L-FABP), acute kidney injury markers (nNAG, KIM-1, NGAL, β2-microglobulin) and renal function parameters (creatinine clearance and fractional Na+ excretion). The protection was maximal in the PRE group and achieved a lower extent in PER and POST groups when compared to Control. As example, urinary clearance of creatinine achieved 4.8±1.2, 1.3±0.9, 0.9±1.4 in PRE, PER and POST groups vs 0.5±0.4 ml/kg/min in Control (all p<0.05), respectively. Importantly, multi-organ failure was associated with elevated blood transcripts of inflammatory markers (e.g., IL-1β, IL-8, IL-10). This was attenuated in all groups submitted to TLV with no difference between PRE, PER and POST groups. As example, changes in IL-1β achieved 2.7±0.4, 3.8±0.4 and 3.2±1.1 in PRE, PER and POST groups vs 5.6±0.7 in Control (fold-change from baseline; p<0.05), respectively. Conclusions: Ultra-fast cooling with TLV attenuates shock and multi-organ failure in a model of abdominal ischemia/reperfusion. The cardiac, liver and renal protections but not anti-inflammatory effects depend upon the window of application.

0093 : Therapeutic hypothermia induced by total liquid ventilation reduces cardiac and cerebral production of free radicals after non shockable cardiac arrest

Ultra-fast cooling induced by total liquid ventilation (TLV) has been shown to be potently neuro and cardioprotective after shockable cardiac arrest and/or acute myocardial infarction . In this study we examined a possible underlying mechanism of this protection, in particular reduced free radicals production. Thirty six rabbits subjected to asphyxia cardiac arrest were divided into three groups: normothermic life support (Control group, n=12) or hypothermia induced by either i.v. cold saline (CONV group; n=12) or by TLV (TLV group, n=12). Using electronic paramagnetic resonance spectroscopy (EPR) and 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine hydrochloride (CMH) as spin probe, we observed a decrease in the production of free radicals in various organs including the heart and the cerebral cortex in TLV and CONV groups as compared to Control, however the effect of TLV was significantly more marked. These results were associated with a significant improvement of the neurological status and an increase in the survival rate as compared to Control and CONV groups. Therapeutic hypothermia induced by TLV could be a promising approach to improve organ preservation before irreversible alteration by free radicals.

Kidney Protection by Hypothermic Total Liquid Ventilation after Cardiac Arrest in Rabbits

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. 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. 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. Ultrafast cooling with TLV is renal protective after cardiac arrest and resuscitation, which could increase kidney availability for organ donation.

Hypothermic Liquid Ventilation Prevents Early Hemodynamic Dysfunction and Cardiovascular Mortality After Coronary Artery Occlusion Complicated by Cardiac Arrest in Rabbits

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. Prospective, randomized animal study. Academic research laboratory. Male New Zealand rabbits. 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. 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). Achieving hypothermia rapidly is critical to improve the cardiovascular outcome after cardiac arrest with underlying myocardial infarction.

Cardiopulmonary function and oxygen delivery during total liquid ventilation

Total liquid ventilation (TLV) with perfluorocarbons has shown to improve cardiopulmonary function in the injured and immature lung; however there remains controversy over the normal lung. Hemodynamic effects of TLV in the normal lung currently remain undetermined. This study compared changes in cardiopulmonary and circulatory function caused by either liquid or gas tidal volume ventilation. In a prospective, controlled study, 12 non-injured anesthetized, adult New Zealand rabbits were primarily conventionally gas-ventilated (CGV). After instrumentation for continuous recording of arterial (AP), central venous (CVP), left artrial (LAP), pulmonary arterial pressures (PAP), and cardiac output (CO) animals were randomized into (1) CGV group and (2) TLV group. In the TLV group partial liquid ventilation was initiated with instillation of perfluoroctylbromide (12 ml/kg). After 15 min, TLV was established for 3 hr applying a volume-controlled, pressure-limited, time-cycled ventilation mode using a double-piston configured TLV. Controls (CGV) remained gas-ventilated throughout the experiment. During TLV, heart rate, CO, PAP, MAP, CVP, and LAP as well as derived hemodynamic variables, arterial and mixed venous blood gases, oxygen delivery, PVR, and SVR did not differ significantly compared to CGV. Liquid tidal volumes suitable for long-term TLV in non-injured rabbits do not significantly impair CO, blood pressure, and oxygen dynamics when compared to CGV.

Total Liquid Ventilation Provides Superior Respiratory Support to Conventional Mechanical Ventilation in a Large Animal Model of Severe Respiratory Failure

Total liquid ventilation (TLV) has the potential to provide respiratory support superior to conventional mechanical ventilation (CMV) in the acute respiratory distress syndrome (ARDS). However, laboratory studies are limited to trials in small animals for no longer than 4 hours. The objective of this study was to compare TLV and CMV in a large animal model of ARDS for 24 hours. Ten sheep weighing 53 ± 4 (SD) kg were anesthetized and ventilated with 100% oxygen. Oleic acid was injected into the pulmonary circulation until PaO2:FiO2 ≤ 60 mm Hg, followed by transition to a protective CMV protocol (n = 5) or TLV (n = 5) for 24 hours. Pathophysiology was recorded, and the lungs were harvested for histological analysis. Animals treated with CMV became progressively hypoxic and hypercarbic despite maximum ventilatory support. Sheep treated with TLV maintained normal blood gases with statistically greater PO2 (p < 10(-9)) and lower PCO2 (p < 10(-3)) than the CMV group. Survival at 24 hours in the TLV and CMV groups were 100% and 40%, respectively (p < 0.05). Thus, TLV provided gas exchange superior to CMV in this laboratory model of severe ARDS.

Rapid cooling of the heart with total liquid ventilation prevents transmural myocardial infarction following prolonged ischemia in rabbits

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 60 min 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 °C). Cooling procedures were either external cooling using cold blankets (EC group, n = 7) or ultrafast cooling initiated by 20 min 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 4 h. Results In the EC group, the target temperature was reached only at 60 min of CAO whereas this time-interval was dramatically reduced to 15 and 25 min 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.

Perfluorocarbon induced intra-arrest hypothermia does not improve survival in a swine model of asphyxial cardiac arrest

Background Pulseless electrical activity is an important cause of cardiac arrest. Our purpose was to determine if induction of hypothermia with a cold perfluorocarbon-based total liquid ventilation (TLV) system would improve resuscitation success in a swine model of asphyxial cardiac arrest/PEA. Methods Twenty swine were randomly assigned to control (C, no ventilation, n = 11) or TLV with pre-cooled PFC ( n = 9) groups. Asphyxia was induced by insertion of a stopper into the endotracheal tube, and continued in both groups until loss of aortic pulsations (LOAP) was reached, defined as a pulse pressure less than 2 mmHg. The TLV animals underwent asphyxial arrest for an additional 2 min after LOAP, followed by 3 min of hypothermia, prior to starting CPR. The C animals underwent 5 min of asphyxia beyond LOAP. Both groups then underwent CPR for at least 10 min. The endpoint was the resumption of spontaneous circulation maintained for 10 min. Results Seven of 9 animals achieved resumption of spontaneous circulation (ROSC) in the TLV group vs. 5 of 11 in the C group ( p = 0.2). The mean pulmonary arterial temperature was lower in total liquid ventilation animals starting 4 min after induction of hypothermia (TLV 36.3 ± 0.2 °C vs. C 38.1 ± 0.2 °C, p < 0.0001). Arterial p O 2 was higher in total liquid ventilation animals at 2.5 min of CPR (TLV 76 ± 12 mmHg vs. C 44 ± 2 mmHg; p = 0.03). Conclusion Induction of moderate hypothermia using perfluorocarbon-based total liquid ventilation did not improve ROSC success in this model of asphyxial cardiac arrest.

TOTAL LIQUID VENTILATION IN PRETERM LAMBS: REPORT OF IN VIVO TESTS OF A VENTILATOR PROTOTYPE

The purpose of this study was to perform in vivo animal tests of a novel ventilator prototype for Total Liquid Ventilation (TLV). A total of 17 preterm lambs (gestational age 110±5 days; body weight 3.1±1.2kg), under general anesthesia, were instrumented to record hemodynamic values and gas exchange which were monitored throughout the experiments. Tracheostomy and intratracheal intubation were performed, as well as instrumentation with ex uterus intrapartum treatment (EXIT) support. All fetuses were maintained connected to the placental circulation for the first 10 minutes of ventilation. After complete extraction and disconnection from the mother circulation, the lambs were ventilated for 6 hours. Eleven lambs were ventilated with the prototype ventilator (TLV group); the other 6 lambs (gas ventilation, GV group) were ventilated, as control, with a conventional mechanical ventilator (Siemens Servoventilator 900B). The TLV prototype consists of a volume-controlled, pressure-limited ventilator; it comprises a double-piston system performing respiratory cycles and an uncoupled refresh circuit to achieve perfluorocarbon (PFC) filtration, thermo-regulation, oxygenation, and CO2washout. TLV was performed using PFC FC77 (3M Corp.). At the end of each experiment, fetal lungs were excised and processed for light microscopy to verify airway and lung parenchyma condition. Adequate oxygenation was achieved, while hypercapnia was shown in both groups. Mean arterial pO2 and pCO2 were respectively 72.6 mmHg and 77.8 mmHg, in the TLV group, while 86.6 mmHg and 67.9 mmHg, in the GV group. Higher mortality occurred in the gas ventilation group (67%) than in the TLV group (45%). The histological analyses highlighted a more homogeneous distribution of the respiratory medium in the TLV-ventilated animals (49.3%) with respect to the control group (38.8%) and the histological analyses showed minimal signs of inflammation of the airways and lung parenchyma in the TLV-ventilated animals. The outcomes of the experiments showed the capacity of the TLV ventilator to support the life of very preterm neonatal animals, on the other hand it could be useful to refine the approach to the firsts breathes to minimize the possible lungs damages and improve distribution of the respiratory medium.

Liquid assisted ventilation: An alternative ventilatory strategy for acute meconium aspiration injury

Evidence of surfactant inactivation by meconium has led to the use of exogenous surfactant therapy in the management of meconium aspiration syndrome (MAS). Liquid assisted ventilation has been shown to improve the cardiopulmonary function in lungs with high surface tension. We compared exogenous surfactant therapy with liquid assisted ventilation in the management of experimental acute meconium aspiration injury. Thirty-two newborn lambs were ventilated at peak inspiratory pressures of 13-16 cm H2O, positive end expiratory pressure of 3-4 cm H2O, fractional inspired oxygen concentration (FiO2) of 1.0, and a respiratory frequency range between 30 and 35 breaths/min. Baseline arterial blood gases, pulmonary function, and arterial blood pressure measurements were taken. All lambs were given 2-3 ml/kg of an unfiltered 25% meconium solution. Lambs were then randomized into either gas-ventilated meconium control, or one of three treatment groups: 1) surfactant; 2) partial liquid ventilation (PLV); or 3) total liquid ventilation (TLV) for 4 hours after meconium injury. All treated groups demonstrated a significant increase in arterial oxygenation (P < 0.05); surfactant and PLV-treated lambs demonstrated significantly decreased arterial PCO2 (P < 0.05). Compliance in all groups increased compared with injury values; compliance of the TLV group increased more than in all other treatment groups (P < 0.05). In addition, lung histology of the TLV group demonstrated clear, intact alveolar epithelium and homogeneously expanded alveoli, while no such improvement was evident in the other groups. These data suggest roles for both exogenous surfactant therapy and liquid assisted ventilation techniques in the management of MAS.