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

Baicalin and lung diseases

Studies focusing on natural products have been conducted worldwide, and the results suggest that their natural ingredients effectively treat a wide range of illnesses. Baicalin (BIA) is a glycoside derived from the flavonoid baicalein present in Scutellaria baicalensis of the Lamiaceae family. Interestingly, BIA has been shown to protect the lungs in several animal models used in numerous studies. Therefore, we fully analyzed the data of the studies that focused on BIA's lung protective function against various injuries and included them in this review. Interestingly, BIA exhibits promising effects against acute lung injury, lung fibrosis, pulmonary embolism, and lung remodelling associated with COPD, LPS, and paraquat insecticide. BAI exhibits anticancer activity against lung cancer. Additionally, BIA potently attenuates lung damage associated with infections. BIA primarily exerts its therapeutic effects by suppressing inflammation, oxidative stress immune response, and apoptosis pathways. Nrf2/HO-1, PI3K/Akt, NF-κB, STAT3, MAPKs, TLR4, and NLRP3 are important targets in the pulmonary therapeutic effects of BIA on different lung disease models. Consequently, we recommend using it in future potential clinical applications, its contribution to treatment guidelines, and translating its promising effects to clinical practice in lung diseases.

Iatrogenic air embolism: pathoanatomy, thromboinflammation, endotheliopathy, and therapies

Iatrogenic vascular air embolism is a relatively infrequent event but is associated with significant morbidity and mortality. These emboli can arise in many clinical settings such as neurosurgery, cardiac surgery, and liver transplantation, but more recently, endoscopy, hemodialysis, thoracentesis, tissue biopsy, angiography, and central and peripheral venous access and removal have overtaken surgery and trauma as significant causes of vascular air embolism. The true incidence may be greater since many of these air emboli are asymptomatic and frequently go undiagnosed or unreported. Due to the rarity of vascular air embolism and because of the many manifestations, diagnoses can be difficult and require immediate therapeutic intervention. An iatrogenic air embolism can result in both venous and arterial emboli whose anatomic locations dictate the clinical course. Most clinically significant iatrogenic air emboli are caused by arterial obstruction of small vessels because the pulmonary gas exchange filters the more frequent, smaller volume bubbles that gain access to the venous circulation. However, there is a subset of patients with venous air emboli caused by larger volumes of air who present with more protean manifestations. There have been significant gains in the understanding of the interactions of fluid dynamics, hemostasis, and inflammation caused by air emboli due to in vitro and in vivo studies on flow dynamics of bubbles in small vessels. Intensive research regarding the thromboinflammatory changes at the level of the endothelium has been described recently. The obstruction of vessels by air emboli causes immediate pathoanatomic and immunologic and thromboinflammatory responses at the level of the endothelium. In this review, we describe those immunologic and thromboinflammatory responses at the level of the endothelium as well as evaluate traditional and novel forms of therapy for this rare and often unrecognized clinical condition.

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.

Surfactant Attenuates Air Embolism-Induced Lung Injury by Suppressing NKCC1 Expression and NF-κB Activation

Excessive amounts of air can enter the lungs and cause air embolism (AE)-induced acute lung injury (ALI). Pulmonary AE can occur during diving, aviation, and iatrogenic invasive procedures. AE-induced lung injury presents with severe hypoxia, pulmonary hypertension, microvascular hyper-permeability, and severe inflammatory responses. Pulmonary AE-induced ALI is a serious complication resulting in significant morbidity and mortality. Surfactant is abundant in the lungs and its function is to lower surface tension. Earlier studies have explored the beneficial effects of surfactant in ALI; however, none have investigated the role of surfactant in pulmonary AE-induced ALI. Therefore, we conducted this study to determine the effects of surfactant in pulmonary AE-induced ALI. Isolated-perfused rat lungs were used as a model of pulmonary AE. The animals were divided into four groups (n = 6 per group): sham, air embolism (AE), AE + surfactant (0.5 mg/kg), and AE+ surfactant (1 mg/kg). Surfactant pretreatment was administered before the induction of pulmonary AE. Pulmonary AE was induced by the infusion of 0.7 cc air through a pulmonary artery catheter. After induction of air, pulmonary AE was presented with pulmonary edema, pulmonary microvascular hyper-permeability, and lung inflammation with neutrophilic sequestration. Activation of NF-κB was observed, along with increased expression of pro-inflammatory cytokines, and Na-K-Cl cotransporter isoform 1 (NKCC1). Surfactant suppressed the activation of NF-κB and decreased the expression of pro-inflammatory cytokines and NKCC1, thereby attenuating AE-induced lung injury. Therefore, AE-induced ALI presented with pulmonary edema, microvascular hyper-permeability, and lung inflammation. Surfactant suppressed the expressions of NF-κB, pro-inflammatory cytokines, and NKCC1, thereby attenuating AE-induced lung injury.

The Blockade of Store-Operated Calcium Channels Improves Decompression Sickness in Rats

Background

Previous investigations reveal that BTP2, a store-operated calcium channel blocker, has protective and anti-inflammatory properties in multiple inflammatory diseases. This study investigates whether BTP2 can protect against decompression sickness (DCS) in a rat model.

Methods

BTP2 (2 mg/kg) was administered to male Sprague–Dawley rats 30 min before subjecting them to hyperbaric pressure. Control rats were not treated. After decompression, signs of DCS were examined, and samples of bronchoalveolar lavage fluid and lung tissue were obtained for evaluation.

Results

The incidence and mortality of DCS were decreased significantly in rats treated with BTP2 compared to those treated with dimethyl sulfoxide. BTP2 significantly attenuated DCS-induced lung edema, histological evidence of lung inflammation, necroptosis, and apoptosis, while it decreased levels of tumor necrosis factor alpha, interleukin-6, and cytokine-induced neutrophil chemoattractant-1 in bronchoalveolar lavage fluid. In addition, BTP2 reduced the expression of nuclear factor of activated T cells and early growth response protein 3 in lung tissue. BTP2 also significantly increased the levels of inhibitor kappa B alpha and suppressed the levels of nuclear factor kappa B in lung tissue.

Conclusion

The results suggest that BTP2 may has potential as a prophylactic therapy to attenuate DCS-induced injury.

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.

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.

Effects of aspirin on the expression of nuclear factor-κB in a rat model of acute pulmonary embolism

BACKGROUND

Acute pulmonary embolism (APE) is a disorder involving the pulmonary circulation resulting from a blockage of the pulmonary artery. The present study aimed to investigate the effects of aspirin on the nuclear factor-κB (NF-κB) activity in a rat model of APE.

METHODS

A total of 108 healthy male Sprague-Dawley rats were randomly assigned into six groups (n=18 rats per group): control group, sham operation group, APE model group, and low-, medium- and high-dose aspirin groups. Six, 24, and 72 hours after the induction of APE, rats in the low-, medium- and high-dose aspirin groups were given aspirin at a respective daily dose of 150, 300, and 600 mg/kg by gavage for three consecutive days. Rats in the other groups were treated with equal volumes of normal saline. Six rats in each group were anesthetized with 10% chloral hydrate solution at each time point, and then the lung tissues were collected and analyzed using immunohistochemical staining.

RESULTS

Positive immunohistochemical staining was present in the bronchial epithelial cells, alveolar cells, macrophages, and surrounding bronchial smooth muscle cells. When compared with the APE model group, the number of positive cells was significantly lower in the other groups at each time point (P<0.001). Statistically significant differences were also observed among the aspirin-treated groups at 6 hours (P<0.05, P<0.001). Compared with the APE model group, NF-κB protein expression was reduced in the other groups at each time point (P<0.05, P<0.001). Rats from the APE model group had thrombosis, damaged alveolar walls, and pulmonary hemorrhage, along with different degrees of inflammatory cellular infiltration at each time point. However, pathological changes such as pulmonary hemorrhage and infiltration of inflammatory cells were attenuated after the aspirin treatment.

CONCLUSION

Aspirin can significantly inhibit NF-κB activity in the lung of rats with APE in a dose-dependent manner, and can alleviate lung injury after APE.

Basis for the use of localized hypothermia during radical pelvic surgery

Controlled tissue cooling, or hypothermia, has been used therapeutically for decades to mitigate the negative effects of traumatic, ischemic, and surgical insults. When applied systemically, moderate hypothermia can attenuate or prevent the extent of neurologic sequelae. Localized hypothermia, on the other hand, has the capacity to reduce tissue edema, suppress inflammation, and minimize the severity of peripheral nerve injury. Therapeutic hypothermia has been used in critical care, neurosurgery, ophthalmology, otolaryngology, cardiothoracic surgery and most recently in urology. Nerve injury during radical pelvic surgery can result in urinary incontinence or retention, impotence and bowel dysfunction. Localized hypothermia during radical prostatectomy has demonstrated improved recovery of urinary continence and erectile function, and similar benefits might be observed in other types of radical pelvic surgery.

Central venous catheters may be a potential source of massive air emboli during vascular procedures involving extracorporeal circulation: an experimental study

Central venous catheters are mandatory during every major procedure involving extracorporeal circulation. Air emboli potentially could enter the circulation through this device when negative pressure is applied in the venous cannula. The following experimental study was initiated by a fatal massive air embolus during a vascular procedure involving cardiopulmonary bypass. An experimental setup was established, simulating a real scenario. The experiment was performed with a 40% glycerol/water mixture which exhibits properties and fluid dynamics close to blood. A heart-lung machine provided circulation of the fluid. The flow was adjusted according to the gravitational status. A triple-lumen central venous catheter with one line open to air was lowered into the liquid. The disconnected lumen of the central venous catheter was manipulated so it approached and was located in close proximity to the venous cannula. An air flow of up to 300 ml/min could be obtained from the central venous catheter with a flow in the cardiopulmonary bypass circuit of 2.3 L/min. A linear relationship was observed between flow in the circuit and air flow. Consecutive measurements proved consistent with acceptable results, proving that a disconnected central venous catheter might, under certain circumstances, be a source of massive air emboli during cardiopulmonary bypass.