The effects of hypothermia on endotoxin-primed lung

Mesenchymal Stem Cell-derived Type II Alveolar Epithelial Progenitor Cells Attenuate LPS-induced Acute Lung Injury and Reduce P63 Expression

AIM

Acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) is a severe clinical respiratory-failure disease mainly characterized by acute damage to the alveolar epithelium and pulmonary vascular endothelial cells. Stem cell therapy has emerged as a potential regenerative strategy for ARDS/ALI, however, the outcome is limited, and the underlying mechanisms are unclear.

INTRODUCTION

We established a differentiation system for bone marrow-derived mesenchymal stem cellderived (BM-MSC) type II alveolar epithelial progenitor cells (AECIIs) and assessed their regulatory effects on lipopolysaccharide (LPS)-induced ALI.

METHODS

We induced BM-MSC differentiation into AECIIs using a specific conditioned medium. After 26 days of differentiation, 3×105 BM-MSC-AECIIs were used to treat mice with LPS-induced ALI through tracheal injection.

RESULTS

After tracheal injection, BM-MSC-AECIIs migrated to the perialveolar area and reduced LPSinduced lung inflammation and pathological injury. RNA-seq suggested that P63 protein was involved in the effects of BM-MSC-AECIIs on lung inflammation.

CONCLUSION

Our results suggest that BM-MSC-AECIIs may reduce LPS-induced acute lung injury by decreasing P63 expression.

Design and rationale of the CHILL phase II trial of hypothermia and neuromuscular blockade for acute respiratory distress syndrome

The Cooling to Help Injured Lungs (CHILL) trial is an open label, two group, parallel design multicenter, randomized phase IIB clinical trial assessing the efficacy and safety of targeted temperature management with combined external cooling and neuromuscular blockade to block shivering in patients with early moderate-severe acute respiratory distress syndrome (ARDS). This report provides the background and rationale for the clinical trial and outlines the methods using the Consolidated Standards of Reporting Trials guidelines. Key design challenges include: [1] protocolizing important co-interventions; [2] incorporation of patients with COVID-19 as the cause of ARDS; [3] inability to blind the investigators; and [4] ability to obtain timely informed consent from patients or legally authorized representatives early in the disease process. Results of the Reevaluation of Systemic Early Neuromuscular Blockade (ROSE) trial informed the decision to mandate sedation and neuromuscular blockade only in the group assigned to therapeutic hypothermia and proceed without this mandate in the control group assigned to a usual temperature management protocol. Previous trials conducted in National Heart, Lung, and Blood Institute ARDS Clinical Trials (ARDSNet) and Prevention and Early Treatment of Acute Lung Injury (PETAL) Networks informed ventilator management, ventilation liberation and fluid management protocols. Since ARDS due to COVID-19 is a common cause of ARDS during pandemic surges and shares many features with ARDS from other causes, patients with ARDS due to COVID-19 are included. Finally, a stepwise approach to obtaining informed consent prior to documenting critical hypoxemia was adopted to facilitate enrollment and reduce the number of candidates excluded because eligibility time window expiration.

Soy isoflavone reduces LPS-induced acute lung injury via increasing aquaporin 1 and aquaporin 5 in rats

Acute lung injury (ALI) followed with severe inflammation and oxidative stress. Anti-inflammatory and antioxidant are the properties of aquaporin 1 (AQP1) and aquaporin 5 (AQP5). The goal of this study was to see if soy isoflavone can diminish lipopolysaccharide (LPS)-induced ALI and the underling mechanism. LPS-induced ALI was given to Sprague-Dawley rats 14 days following oophorectomy. One hour before the LPS challenge, estradiol (1 mg/kg) was administered subcutaneously as positive control and soy isoflavone was intragastric administration for 14 days prior to LPS challenge with different doses. Six hours after LPS challenge, the pulmonary edema, pathophysiology, inflammation, and the oxidative stress in lung tissues of rats were discovered. We found that soy isoflavone can reduce pulmonary edema and the lung pathology in a dose-dependent manner. Furthermore, tumor necrosis factor-alpha, interleukin-1β, and interleukin-6 were decreased in rats treated with soy isoflavone. Meanwhile, soy isoflavone reduced pulmonary oxidative stress by decreasing malondialdehyde levels, while increasing superoxide dismutase levels in lung tissues in a dose-dependent manner. Mechanically, we found that the mRNA and protein level of AQP1 and AOP5 were increased in lung tissues of rats treated with soy isoflavone compared the LPS-treated rats. Thus, soy isoflavone alleviates LPS-induced ALI through inducing AQP1 and AQP5.

Evaluation of the cooling efficacy of different equine leg cooling methods

The use of cold therapy or cryotherapy is widespread in human and veterinary medicine and sports medicine and ranges from focal, localised treatment to whole body treatment. In equestrian sport, a variety of methods and commercial products exist for cooling the lower limbs. To date, there have been no studies comparing the relative efficacy of these different cooling methods. Due to the difficulty in standardising techniques for comparing cooling on live horses, a repeatable laboratory method for determining cooling efficacy was developed using a metal flask. The amount of heat removed from the flask by different traditional methods (corrected for the heat lost over 30 min for the flask without treatment) and a variety of commercial cooling products was calculated by measuring the decrease in temperature (in triplicate) within the flask from an initial external temperature of 40.2±0.4 °C and an internal temperature of 42.1±0.9 °C (mean ± standard deviation) over 30 min. The methods compared were: cold hosing (15 °C), standing in ice and water (0 °C), ice-cube packs, instant cold-packs, ice boots, evaporative (water) cooled boots, ice gel and clay. The greatest amount of heat removed in 30 min was 134±4 kJ for standing in ice & water (0 °C). The next highest rates of removal were 66.4±1.3, 57.1±6.1 and 56.9±1.3 kJ for cold hosing (15 °C), Ice Horse (-23 °C) and Cryochaps (-23 °C), respectively. The lowest amount of heat removed was for covered clay (8±1 kJ; initial clay temperature 15 °C). This approach allows different methods of cooling to be compared without the difficulties encountered in standardisation in live horses.

Hypothermia alleviated LPS-induced acute lung injury in Rat models through TLR2/MyD88 pathway

Acute lung injury (ALI) is a common clinical syndrome in ICU departments with high mortality. The pathology of ALI is still not clear and there is no specific and efficient treatment against ALI. In this study, we established ALI rat model through lipopolysaccharide administration. We found that hypothermia therapy led to significant improvement in oxygenation index, edema formation and pathological score, demonstrating that hypothermia is beneficial to the recovery of lung function and alleviation of lung injury. Besides, hypothermia resulted in a decrease in plasminogen activator inhibitor-1(PAI-1) concentration, showing the inflammation was partially inhibited. This was also confirmed by a decrease in TNF-α mRNA and protein level in hypothermia group. The effect of hypothermia was mediated by TLR2/MyD88 signaling, which led to the alteration in NF-κB p65 level. Collectively, this study indicated that hypothermia therapy was potentially an efficient therapy against ALI.

Evaluation of digital cryotherapy using a commercially available sleeve style ice boot in healthy horses and horses receiving i.v. endotoxin

BACKGROUND

Continuous digital cryotherapy experimentally prevents development and reduces severity of sepsis-associated laminitis. A sleeve style ice boot where ice is in direct contact with the skin, and water drains from the boot is being used clinically for distal limb cryotherapy. The degree of cooling achieved by this boot is unknown.

OBJECTIVES

Evaluate skin and lamellar cooling after application of the ice sleeve in healthy horses, and the same horses during an endotoxaemia model.

STUDY DESIGN

Prospective study, crossover design.

METHODS

In eight healthy horses thermocouples were inserted into dorsal lamellae of both front feet, and under skin on both metacarpi. One forelimb received cryotherapy using sleeve style ice boot, with contralateral limb as control. Temperature was recorded on data logging devices at 5 min intervals during each cryotherapy session. Day 1: temperature data was collected for healthy horses. Day 2: data was collected for the same horses during i.v. administration of endotoxin.

RESULTS

In healthy and endotoxaemic horses, the sleeve style ice boot significantly decreased mean skin (7.2°C and 5.8°C respectively) and lamellar (10.8°C and 9.6°C respectively) temperatures compared with control limbs (P<0.001). Skin and lamellar temperatures in endotoxaemic horses undergoing cryotherapy were significantly colder than in healthy horses (P = 0.01).

MAIN LIMITATIONS

Order of treatment not randomised.

CONCLUSIONS

The boot caused significant decreases in lamellar temperatures compared with untreated control limbs in all horses. Endotoxaemic horses had significantly colder lamellae and skin than healthy horses. This study is the first to show that a sleeve style boot, where ice does not cover the hoof, can cause significant decreases in lamellar temperatures through cooling of blood as it travels to the foot.

Pterostilbene 4'-β-Glucoside Attenuates LPS-Induced Acute Lung Injury via Induction of Heme Oxygenase-1

Heme oxygenase-1 (HO-1) can exert anti-inflammatory and antioxidant effects. Acute lung injury (ALI) is associated with increased inflammation and influx of proinflammatory cells and mediators in the airspaces and lung parenchyma. In this study, we demonstrate that pterostilbene 4′-β-glucoside (4-PG), the glycosylated form of the antioxidant pterostilbene (PTER), can protect against lipopolysaccharide- (LPS-) or Pseudomonas aeruginosa- (P. aeruginosa-) induced ALI when applied as a pretreatment or therapeutic post-treatment, via the induction of HO-1. To determine whether HO-1 mediates the antioxidant and anti-inflammatory effects of 4-PG, we subjected mice genetically deficient in Hmox-1 to LPS-induced ALI and evaluated histological changes, HO-1 expression, and proinflammatory cytokine levels in bronchoalveolar lavage (BAL) fluid. 4-PG exhibited protective effects on LPS- or P. aeruginosa-induced ALI by ameliorating pathological changes in lung tissue and decreasing proinflammatory cytokines. In addition, HO-1 expression was significantly increased by 4-PG in cells and in mouse lung tissues. The glycosylated form of pterostilbene (4-PG) was more effective than PTER in inducing HO-1 expression. Genetic deletion of Hmox-1 abolished the protective effects of 4-PG against LPS-induced inflammatory responses. Furthermore, we found that 4-PG decreased both intracellular ROS levels and mitochondrial (mt) ROS production in a manner dependent on HO-1. Pharmacological application of the HO-1 reaction product carbon monoxide (CO), but not biliverdin or iron, conferred protection in Hmox-1-deficient macrophages. Taken together, these results demonstrate that 4-PG can increase HO-1 expression, which plays a critical role in ameliorating intracellular and mitochondrial ROS production, as well as in downregulating inflammatory responses induced by LPS. Therefore, these findings strongly suggest that HO-1 mediates the antioxidant and anti-inflammatory effects of 4-PG.

Effects of hypothermia on lung inflammation in a rat model of meconium aspiration syndrome

PURPOSE

To evaluate the effects of hypothermia treatment on meconium-induced inflammation.

METHODS

Fifteen rats were instilled with human meconium (MEC, 1.5 mL/kg, 65 mg/mL) intratracheally and ventilated for 3 hours. Eight rats that were ventilated and not instilled with meconium served as a sham group. In MEC-hypothermia group, the body temperature was lowered to 33±0.5°C. Analysis of the blood gases, interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α in bronchoalveolar lavage (BAL) fluid samples, and histological analyses of the lungs were performed.

RESULTS

The BAL fluid TNF-α, IL-1β, IL-6 and IL-8 concentrations were significantly higher in the MEC-hypothermia group than in the MEC-normothermia (p < 0.001, p < 0.001, p = 0.001, p < 0.001, respectively) and sham-controlled groups (p < 0.001, p < 0.001, p < 0.001, p < 0.001, respectively).

CONCLUSION

Meconium-induced inflammatory cytokine production is affected by the body temperature control.

Novel dry cryotherapy system for cooling the equine digit

Objectives

Digital cryotherapy is commonly used for laminitis prophylaxis and treatment. Currently validated methods for distal limb cryotherapy involve wet application or compression technology. There is a need for a practical, affordable, dry cryotherapy method that effectively cools the digit. The objective of this study was to evaluate the hoof wall surface temperatures (HWSTs) achieved with a novel dry cryotherapy technology.

Design

Repeated-measures in vivo experimental study.

Setting

Experimental intervention at a single site.

Participants

6 systemically healthy horses (3 mares, 3 geldings).

Interventions

Cryotherapy was applied to six horses for eight hours with a commercially available rubber and rubber and welded fabricice boot, which extended proximally to include the foot and pastern. Reusable malleable cold therapy packs were secured against the foot and pastern with the three built-in hook-and-loop fastener panels.

Primary and secondary outcome measures

HWST and pastern surface temperature of the cryotherapy-treated limb, HWST of the control limb and ambient temperature were recorded every five minutes throughout the study period.

Results

Results were analysed with mixed-effects multivariable regression analysis. The HWST (median 11.1°C, interquartile range 8.6°C–14.7°C) in the cryotherapy-treated limb was significantly decreased compared with the control limb (median 29.7°C, interquartile range 28.9°C–30.4°C) (P≤0.001). Cryotherapy limb HWST reached a minimum of 6.75°C (median) with an interquartile range of 4.1°C–9.3°C. Minimum HWST was achieved 68 minutes after cryotherapy pack application.

Conclusions

Dry application of cryotherapy significantly reduced HWST and reached minimums below the therapeutic target of 10°C. This cryotherapy method might offer an effective alternative for digital cooling.

Pilot Feasibility Study of Therapeutic Hypothermia for Moderate to Severe Acute Respiratory Distress Syndrome

OBJECTIVES

Prior studies suggest hypothermia may be beneficial in acute respiratory distress syndrome, but cooling causes shivering and increases metabolism. The objective of this study was to assess the feasibility of performing a randomized clinical trial of hypothermia in patients with acute respiratory distress syndrome receiving treatment with neuromuscular blockade because they cannot shiver.

DESIGN

Retrospective study and pilot, prospective, open-label, feasibility study.

SETTING

Medical ICU.

PATIENTS

Retrospective review of 58 patients with acute respiratory distress syndrome based on Berlin criteria and PaO2/FIO2 less than 150 who received neuromuscular blockade. Prospective hypothermia treatment in eight acute respiratory distress syndrome patients with PaO2/FIO2 less than 150 receiving neuromuscular blockade.

INTERVENTION

Cooling to 34-36°C for 48 hours.

MEASUREMENTS AND MAIN RESULTS

Core temperature, hemodynamics, serum glucose and electrolytes, and P/F were sequentially measured, and medians (interquartile ranges) presented, 28-day ventilator-free days, and hospital mortality were calculated in historical controls and eight cooled patients. Average patient core temperature was 36.7°C (36-37.3°C), and fever occurred during neuromuscular blockade in 30 of 58 retrospective patients. In the prospectively cooled patients, core temperature reached target range less than or equal to 4 hours of initiating cooling, remained less than 36°C for 92% of the 48 hours cooling period without adverse events, and was lower than the controls (34.35°C [34-34.8°C]; p < 0.0001). Compared with historical controls, the cooled patients tended to have lower hospital mortality (75% vs 53.4%; p = 0.26), more ventilator-free days (9 [0-21.5] vs 0 [0-12]; p = 0.16), and higher day 3 P/F (255 [160-270] vs 171 [120-214]; p = 0.024).

CONCLUSIONS

Neuromuscular blockade alone does not cause hypothermia but allowed acute respiratory distress syndrome patients to be effectively cooled. Results support conducting a randomized clinical trial of hypothermia in acute respiratory distress syndrome and the feasibility of studying acute respiratory distress syndrome patients receiving neuromuscular blockade.

Effect of Delayed Digital Hypothermia on Lamellar Inflammatory Signaling in the Oligofructose Laminitis Model

Background

In the oligofructose (OF) model of sepsis‐related laminitis (SRL), digital hypothermia (“cryotherapy”) initiated before the onset of clinical signs is reported not only to limit lamellar injury, but also to cause marked inhibition of lamellar inflammatory signaling.

Hypothesis/Objectives

Because hypothermia also has been reported to be protective when not initiated until the onset of lameness in the OF model of SRL, we hypothesized that the lamellar protection conferred by hypothermia is caused by local lamellar inhibition of inflammatory signaling as described when hypothermia was initiated earlier in the disease process.

Animals

Eight Standardbred geldings aged 3–11 years with no lameness and no abnormalities of the feet detectable by gross or radiographic examination.

Methods

Using the OF model of SRL, lamellar mRNA concentrations of proinflammatory cytokines, chemokines, and endothelial adhesion proteins were compared between samples from treated limbs (CRYO, submerged in ice water for 36 hour starting at the onset of lameness), untreated limbs (NON‐CRYO, opposite limb from CRYO limbs maintained at ambient temperature), and untreated limbs from normal horses in which laminitis was not induced (CON).

Results

Although OF administration resulted in increases in lamellar mRNA concentrations of several inflammatory mediators in NON‐CRYO limbs (vs CON), digital hypothermia had no significant effect on these increases.

Conclusions and Clinical Importance

The lack of inflammatory inhibition in lamellar tissue samples in our study indicates that the protective effects of digital hypothermia instituted at the onset of clinical signs of laminitis do not arise from inhibition of inflammatory pathways.

Expression profiling of microRNAs in lipopolysaccharide-induced acute lung injury after hypothermia treatment

We investigated the expression profiles of miRNAs in acute lung injury (ALI) rats after hypothermia treatment. ALI rats were induced with lipopolysaccharide (LPS) and maintained with hypothermia (HT) or normothermia (NT) for 6 hours. HT attenuated inflammatory cell infiltration in the lung and improved biochemical indicators of multi-organ dysfunction. Nineteen miRNAs were significantly differentially expressed in the HT group compared with the NT group. miR-142, miR-98, miR-541, miR-503, miR-653, miR- 223, miR-323 and miR-196b exhibited opposite patterns of expression between the two groups. These dysregulated miRNAs were mainly involved in the immune and inflammatory response on functional annotation analyses. This study shows that HT has lung protective effects and influences expression profiles of miRNAs in ALI. And dysregulated miRNAs after HT modulate the immune and inflammation in ALI. These results suggest that dysregulated miRNAs play a role in the mechanism of the lung protective effects of HT in ALI.

Lung Perfusion and Ventilation During Cardiopulmonary Bypass Reduces Early Structural Damage to Pulmonary Parenchyma

BACKGROUND

It is unclear whether maintaining pulmonary perfusion and ventilation during cardiopulmonary bypass (CPB) reduces pulmonary inflammatory tissue injury compared with standard CPB where the lungs are not ventilated and are minimally perfused. In this study, we tested the hypothesis that maintenance of lung perfusion and ventilation during CPB decreases regional lung inflammation, which may result in less pulmonary structural damage.

METHODS

Twenty-seven pigs were randomly allocated into a control group only submitted to sternotomy (n = 8), a standard CPB group (n = 9), or a lung perfusion group (n = 10), in which lung perfusion and ventilation were maintained during CPB. Hemodynamics, gas exchanges, respiratory mechanics, and systemic interleukins (ILs) were determined at baseline (T0), at the end of 90 minutes of CPB (T90), and 180 minutes after CPB (T180). Bronchoalveolar lavage (BAL) ILs were obtained at T0 and T180. Dorsal and ventral left lung tissue samples were examined for optical and electron microscopy.

RESULTS

At T90, there was a transient reduction in PaO2/FIO2 in CPB (126 ± 64 mm Hg) compared with the control and lung perfusion groups (296 ± 46 and 244 ± 57 mm Hg; P < 0.001), returning to baseline at T180. Serum ILs were not different among the groups throughout the study, whereas there were significant increases in BAL IL-6 (P < 0.001), IL-8 (P < 0.001), and IL-10 (P < 0.001) in both CPB and lung perfusion groups compared with the control group. Polymorphonuclear counts within the lung tissue were smaller in the lung perfusion group than in the CPB group (P = 0.006). Electron microscopy demonstrated extrusion of surfactant vesicles into the alveolar spaces and thickening of the alveolar septa in the CPB group, whereas alveolar and capillary histoarchitecture was better preserved in the lung perfusion group.

CONCLUSIONS

Maintenance of lung perfusion and ventilation during CPB attenuated early histologic signs of pulmonary inflammation and injury compared with standard CPB. Although increased compared with control animals, there were no differences in serum or BAL IL in animals receiving lung ventilation and perfusion during CPB compared with standard CPB.

Tristetraprolin mediates anti-inflammatory effects of carbon monoxide on lipopolysaccharide-induced acute lung injury

Low-dose inhaled carbon monoxide is reported to suppress inflammatory responses and exhibit a therapeutic effect in models of lipopolysaccharide (LPS)-induced acute lung injury (ALI). However, the precise mechanism by which carbon monoxide confers protection against ALI is not clear. Tristetraprolin (TTP; official name ZFP36) exerts anti-inflammatory effects by enhancing decay of proinflammatory cytokine mRNAs. With the use of TTP knockout mice, we demonstrate here that the protection by carbon monoxide against LPS-induced ALI is mediated by TTP. Inhalation of carbon monoxide substantially increased the pulmonary expression of TTP. carbon monoxide markedly enhanced the decay of mRNA-encoding inflammatory cytokines, blocked the expression of inflammatory cytokines, and decreased tissue damage in LPS-treated lung tissue. Moreover, knockout of TTP abrogated the anti-inflammatory and tissue-protective effects of carbon monoxide in LPS-induced ALI. These results suggest that carbon monoxide-induced TTP mediates the protective effect of carbon monoxide against LPS-induced ALI by enhancing the decay of mRNA encoding proinflammatory cytokines.

Cardiac arrest patients have an impaired immune response, which is not influenced by induced hypothermia

INTRODUCTION

Induced hypothermia is increasingly applied as a therapeutic intervention in ICUs. One of the underlying mechanisms of the beneficial effects of hypothermia is proposed to be reduction of the inflammatory response. However, a fear of reducing the inflammatory response is an increased infection risk. Therefore, we studied the effect of induced hypothermia on immune response after cardiac arrest.

METHODS

A prospective observational cohort study in a mixed surgical-medical ICU. Patients admitted at the ICU after surviving cardiac arrest were included and during 24 hours body temperature was strictly regulated at 33°C or 36°C. Blood was drawn at three time points: after reaching target temperature, at the end of the target temperature protocol and after rewarming to 37°C. Plasma cytokine levels and response of blood leucocytes to stimulation with toll-like receptor (TLR) ligands lipopolysaccharide (LPS) from Gram-negative bacteria and lipoteicoic acid (LTA) from Gram-positive bacteria were measured. Also, monocyte HLA-DR expression was determined.

RESULTS

In total, 20 patients were enrolled in the study. Compared to healthy controls, cardiac arrest patients kept at 36°C (n = 9) had increased plasma cytokines levels, which was not apparent in patients kept at 33°C (n = 11). Immune response to TLR ligands in patients after cardiac arrest was generally reduced and associated with lower HLA-DR expression. Patients kept at 33°C had preserved ability of immune cells to respond to LPS and LTA compared to patients kept at 36°C. These differences disappeared over time. HLA-DR expression did not differ between 33°C and 36°C.

CONCLUSIONS

Patients after cardiac arrest have a modest systemic inflammatory response compared to healthy controls, associated with lower HLA-DR expression and attenuated immune response to Gram-negative and Gram-positive antigens, the latter indicative of an impaired immune response to bacteria. Patients with a body temperature of 33°C did not differ from patients with a body temperature of 36°C, suggesting induced hypothermia does not affect immune response in patients with cardiac arrest.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01020916, registered 25 November 2009.

Effect of therapeutic hypothermia on gas exchange and respiratory mechanics: a retrospective cohort study

Targeted temperature management (TTM) may improve respiratory mechanics and lung inflammation in acute respiratory distress syndrome (ARDS) based on animal and limited human studies. We aimed to assess the pulmonary effects of TTM in patients with respiratory failure following cardiac arrest. Retrospective review of consecutive cardiac arrest cases occurring out of hospital or within 24 hours of hospital admission (2002-2012). Those receiving TTM (n=44) were compared with those who did not (n=42), but required mechanical ventilation (MV) for at least 4 days following the arrest. There were no between-group differences in age, gender, body mass index, APACHE II, or fluid balance during the study period. The TTM group had lower ejection fraction, Glasgow Coma Score, and more frequent use of paralytics. Matched data analyses (change at day 4 compared with baseline of the individual subject) showed favorable, but not statistically significant trends in respiratory mechanics endpoints (airway pressure, compliance, tidal volume, and PaO2/FiO2) in the TTM group. The PaCO2 decreased significantly more in the TTM group, as compared with controls (-12 vs. -5 mmHg, p=0.02). For clinical outcomes, the TTM group consistently, although not significantly, did better in survival (59% vs. 43%) and hospital length of stay (12 vs. 15 days). The MV duration and Cerebral Performance Category score on discharge were significantly lower in the TTM group (7.3 vs. 10.7 days, p=0.04 and 3.2 vs. 4, p=0.01). This small retrospective cohort suggests that the effect of TTM ranges from equivalent to favorable, compared with controls, for the specific respiratory and clinical outcomes in patients with respiratory failure following cardiac arrest.

Continuous digital hypothermia initiated after the onset of lameness prevents lamellar failure in the oligofructose laminitis model

REASONS FOR PERFORMING STUDY

Prophylactic digital hypothermia reduces the severity of acute laminitis experimentally but there is no evidence for its efficacy as a treatment once lameness has already developed.

OBJECTIVES

To investigate the therapeutic effects of digital hypothermia, applied after the onset of lameness, in an experimental acute laminitis model.

STUDY DESIGN

Randomised, controlled (within subject), blinded, experimental trial.

METHODS

Eight Standardbred horses underwent laminitis induction using the oligofructose model. Once lameness was detected at the walk, one forelimb was continuously cooled (CRYO), with the other forelimb maintained at ambient temperature (NON-RX). Dorsal lamellar sections (proximal, middle and distal) harvested 36 h after the onset of lameness/initiation of cryotherapy were analysed by 2 blinded observers: laminitis pathology was scored (0 [normal] to 4 [severe]) and morphometric analyses performed.

RESULTS

Median (interquartile range) histological scores were greater (P<0.05) in NON-RX (proximal 2.8 [2.5-4]; middle 3.5 [2-4]; distal 2.5 [2-3.8]) compared with CRYO limbs (proximal 0.5 [0.5-1.4]; middle 1 [0.6-1]; distal 0.75 [0.5-1]). There was complete physical separation of lamellar dermis from epidermis (score of 4) in 4 of the NON-RX feet at one or more section level(s), which was not observed in any CRYO sections. Histomorphometry was thus limited to sections that remained intact; there was a trend of increased total (TELL) and secondary (SELL) epidermal lamellar length and decreased secondary epidermal lamellar width (SELW) in NON-RX limbs compared with CRYO at all 3 levels; differences were significant (P<0.05) for SELL and SELW in the distal sections.

CONCLUSIONS

Digital hypothermia reduced the severity of lamellar injury and prevented lamellar structural failure (complete dermoepidermal separation) when initiated at the detection of lameness in an acute laminitis model. This study provides the first evidence to support the use of therapeutic digital hypothermia as a treatment for acute laminitis.

Hypothermic versus normothermic cardiopulmonary bypass in patients with valvular heart disease

OBJECTIVE

The aim of this study was to test the hypothesis that normothermic cardiopulmonary bypass (CPB) is as effective as hypothermic CPB in terms of cardiac protection (cTnI level) and outcome in patients with valvular heart disease.

DESIGN

Prospective randomized study.

SETTING

A tertiary cardiothoracic referral center.

PARTICIPANTS

140 patients who had valvular heart disease, with/without coronary artery disease, surgically treated under CPB.

INTERVENTIONS

The patients were allocated randomly to undergo either hypothermic (temperature [T], 31 °C-32 °C) or normothermic CPB (T>36 °C).

MEASUREMENTS AND MAIN RESULTS

The primary endpoint was the dynamics of troponin I. The secondary endpoints were ventilation time, the need for inotropic support, intensive care unit (ICU) and hospital stay durations, complications, and mortality. There were no significant intergroup differences in dynamics of troponin I. Ventilation time was significantly lower in the hypothermic group (6 (5-9) and 8 (5-12); p = 0.01).

CONCLUSIONS

Normothermic CPB in patients with valvular heart disease was as effective as hypothermic perfusion in terms of myocardial protection after the surgery assessed by cTnI release. The short ventilation duration in patients who underwent hypothermic CPB needs to be confirmed in a future investigation.

Hypothermia induced by adenosine 5'-monophosphate attenuates acute lung injury induced by LPS in rats

We have built a rat's model to investigate whether the hypothermia induced by adenosine 5′-monophosphate (5′-AMP) (AIH) could attenuate acute lung injury induced by LPS in rats. We detected the inflammatory cytokine levels in the plasma and bronchoalveolar lavage fluid samples, and we analyzed the pathological changes in the lungs. We have found that AIH can effectively inhibit acute inflammatory reactions and protect the lung from acute injury induced by LPS in rats.

Implication for long-term hypothermia on degradation of interleukin-8 mRNA in endothelial cells stimulated with lipopolysaccharides

This experimental study investigated the effects of long-term hypothermia on the production of interleukin (IL)-8 protein and its mRNA expression in endothelial cells stimulated by lipopolysaccharides (LPS). Human umbilical vein endothelial cells were separated into a non-cooling group (N group: 37°C) and a cooling group (C group: 30°C). These groups were incubated with LPS (1 μg/mL) for 0, 2, 6, 24, 48, 72, and 96 hours. Production of the IL-8 protein secreted into the supernatant and mRNA expression in the cells were measured using enzyme-linked immunoabsorbent assay (ELISA) and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis. To evaluate mRNA stability, both groups were incubated with actinomycin D at 6 hours after incubation with LPS for 24 hours. The degradation ratio was calculated by comparing the total expression of mRNA at 6 hours versus 0 hours. The protein levels in the C group were significantly lower than the N group between 6 and 96 hours. The mRNA expression in the C group was also significantly lower than in the N group up to 48 hours, but at 72 hours it was significantly higher than N group. IL-8 mRNA was less degraded in the C group compared to the N group. Under long-term hypothermia, IL-8 protein production was suppressed, while IL-8 mRNA was stabilized after LPS treatment. The potential of IL-8 to produce an inflammatory response in endothelial cells may persist even during long-term hypothermia.

Therapeutic hypothermia (cryotherapy) to prevent and treat acute laminitis

Digital hypothermia successfully reduces the severity of experimentally induced laminitis. Continuous-distal limb cryotherapy may be a useful technique in clinical cases that are at risk of developing laminitis. This article examines the effects of hypothermia on tissue as well as the rationale, and suggested protocols for the usage of distal limb cryotherapy in the prevention and treatment of laminitis.

The role of mild hypothermia in air embolism-induced acute lung injury

BACKGROUND

Mild hypothermia has become an important treatment for ischemic brain injury. However, the role of mild hypothermia in air embolism-induced lung injury has not been explored. In this study, we investigated whether treatment with mild hypothermia before and synchronous with air infusion can attenuate acute lung injury induced by air embolism.

METHODS

In this rat model study (Sprague-Dawley rats), pulmonary air embolism was induced by venous infusion of air at a rate of 25 microL/min for 40 minutes. Control animals received no air infusion. The rats were randomly assigned to 2 control groups of normothermia (37 degrees C) and mild hypothermia (34 degrees C) and 3 air embolism groups of mild hypothermia induced before air infusion, normothermia with air infusion, and mild hypothermia induced synchronous with air infusion. At the end of the experiment, the variables of lung injury were assessed.

RESULTS

Air infusion elicited a significant increase in lung wet/dry weight ratio and protein, lactate dehydrogenase, and tumor necrosis factor-alpha concentration of the bronchoalveolar lavage fluid. Myeloperoxidase activity, neutrophil infiltration, and interstitial edema in lung tissue were also significantly increased. In addition, nuclear factor-kappaB activity was significantly increased in the lungs. Treatment with mild hypothermia before air infusion reduced increases in these variables, whereas mild hypothermia synchronous with air infusion had no significant effect on them.

CONCLUSIONS

Our study suggests that mild hypothermia before air infusion decreases air embolism-induced acute lung injury. The protective mechanism seems to be the inhibition of inflammation.

Body temperature effects on lung injury in ventilated preterm lambs

AIMS

Mechanical ventilation causes lung injury in premature infants. Hypothermia may protect against and hyperthermia may augment lung injury. We tested the effects of hypo- and hyperthermia on ventilation induced acute lung injury in preterm lambs.

METHODS

Twin sheep fetuses at 128 d GA (term 150 d) were surgically delivered and randomized to unventilated control (UVC), normothermia (38-39 degrees C) without lung injury (NTNI), or to 1 of 3 injurious ventilation groups: hypothermic (33-34 degrees C, LT), normothermic (38-39 degrees C, NT) or hyperthermic (40-41 degrees C, HT). NT, LT and HT groups had 15 min of injurious ventilation (PEEP 0 cmH(2)O, V(T) escalation to 15 mL/kg) following delivery and prior to surfactant. The animals were then gently ventilated (PEEP 5cmH(2)O, V(T) 7.5 mL/kg) for 2h 45 min. NTNI lambs received surfactant at birth prior to gentle ventilation. The lambs were then euthanized, and bronchoalveolar lavage (BAL) fluid and lung tissue were used to evaluate lung injury, inflammatory cell counts, inflammatory markers and cytokine mRNA.

RESULTS

Target temperatures were achieved by 15 min of age and maintained for 3h. All ventilated groups had increased BAL protein, lung inflammation and increased cytokine mRNA. HT animals developed acidosis, premature death, pneumothoraces, impaired lung function and increased inflammatory mRNA expression. LT animals remained clinically stable without pneumothoraces or death, had improved ventilatory efficiency and trended toward lower inflammatory mRNA expression than NT animals.

CONCLUSION

Hyperthermia exacerbated ventilator induced lung injury, while hypothermia may protect against lung injury in the preterm lamb.

In Vitro Assessment of Apoptosis and Necrosis Following Cold Storage in a Human Airway Cell Model

As advances in medical technology improve the efficacy of cell and tissue transplantation, a void remains in our knowledge base as to the specific molecular responses of cells to low-temperature storage. While much focus has been given to solution formulation for tissue perfusion during storage, investigations into cold exposure-induced complex molecular changes remain limited. The intent of this study was to quantify the levels of cell death following hypothermic storage in a lung cell model, establishing a foundation for future in-depth molecular analysis. Normal human lung fibroblasts (IMR-90) were stored for 1 day or 2 days and small airway epithelial cells (SAEC) were stored for 5 days or 7 days at 4°C in complete media, ViaSpan, or ViaSpan + pan-caspase (VI) inhibitor. (Poststorage viability was assessed for 3 days using alamarBlue(™).) Sample analysis revealed that IMR-90 cells stored in ViaSpan remained 80% (±9) viable after 1 day of storage and 21% (±7) viable after 2 days of storage. SAEC cells stored in ViaSpan remained 81% (±5) viable after 5 days and 28% (±7) after 7 days. Microfluidic flow cytometry analysis of the apoptotic and necrotic populations in the ViaSpan-stored samples revealed that in the IMR-90 cells stored for 2 days, 7% of the population was apoptotic at 4-h poststorage, while ∼70% was identified as necrotic. Analysis of the SAEC cell system following 7 days of ViaSpan storage revealed an apoptotic peak of 19% at 4-h poststorage and a corresponding necrotic peak of 19%. Caspase inhibition during hypothermic storage increased viability 33% for IMR-90 and 25% for SAEC. Data revealed a similar pattern of cell death, through both apoptosis and necrosis, once the onset of cold storage failure began, implying a potential conserved mechanism of cold-induced cell death. These data highlight the critical need for a more in-depth understanding of the molecular changes that occur as a result of cold exposure in cells and tissues.

High and low body temperature during the initiation of ventilation for near-term lambs

AIMS

Recent literature suggests hypothermia may protect against lung injury. We evaluated body temperature as a variable in lung inflammation due to oxygenation and mechanical ventilation following delivery of near-term lambs.

METHODS

Twin fetuses were randomized prior to delivery at 140 d GA (term 150 d): unventilated controls, normothermic ventilated with room air, normothermic ventilated with 100% oxygen, low temperature ventilated (target 35 degrees C) with 100% oxygen, and high temperature (target 40 degrees C) with 100% oxygen. Lambs were intubated for gentle mechanical ventilation (tidal volume 7-8ml/kg). Temperature targeting was with radiant warmers and plastic wrap for normothermia, with heat lamps for hyperthermia, and with ice packs for hypothermia. Lambs were euthanized after 2h mechanical ventilation. Post-mortem, bronchoalveolar lavage fluid and lung tissue samples were evaluated for inflammatory responses by measuring inflammatory cell counts, protein, myeloperoxidase, protein carbonyl, and pro-inflammatory cytokine mRNA.

RESULTS

Target temperatures were achieved by 30min of age and tightly maintained for the 2h study. There were no differences in physiologic variables among groups except those directly resulting from study protocol-PaO2 from air vs. 100% oxygen and body temperature. Indicators of inflammation increased similarly in all ventilated groups compared to unventilated controls.

CONCLUSION

Moderate hyperthermia or hypothermia did not affect lung injury responses to the initiation of ventilation at birth in near-term lambs.

Early induction of moderate hypothermia suppresses systemic inflammatory cytokines and intracellular adhesion molecule-1 in rats with caerulein-induced pancreatitis and endotoxemia

OBJECTIVES

To evaluate the systemic effects of moderate hypothermia (MH) and the timing of induction on acute pancreatitis (AP) and endotoxemia in rats.

METHODS

The effects of MH were compared in 4 groups, that is, sham group (38 degrees C), control group (38 degrees C), early MH group (32 degrees C on administration of lipopolysaccharide [LPS]), and delayed MH group (32 degrees C 1 hour after LPS). AP and endotoxemia were induced by intramuscular injection of caerulein and intraperitoneal injection of LPS.

RESULTS

Serum interleukin 6 (IL-6) in both MH groups was significantly lower than that in the control group at 3 hours. Serum interleukin 10 (IL-10) in the early MH group was significantly higher than those in the other 3 groups at 1 hour. IL-10/IL-6 ratios in both MH groups were significantly higher than that in the control group at 3 hours. Serum soluble intercellular adhesion molecule (sICAM-1) in both MH groups was significantly lower than that in the control group at 3 hours. Serum sICAM-1 in the early MH group was significantly lower than that in the delayed MH group. The tendency of pancreatic ICAM-1 was similar to that of serum sICAM-1.

CONCLUSIONS

Early induction of MH might be protective against pancreatic injury and systemic inflammation in AP and endotoxemia.