Clinical and pathological features of fat embolism with acute respiratory distress syndrome

By activating endothelium histone H4 mediates oleic acid-induced acute respiratory distress syndrome

OBJECTIVE

This study investigated pathogenic role and mechanism of extracellular histone H4 during oleic acid (OA)-induced acute respiratory distress syndrome (ARDS).

METHODS

ARDS was induced by intravenous injection of OA in mice, and evaluated by blood gas, pathological analysis, lung edema, and survival rate. Heparan sulfate (HS) degradation was evaluated using immunofluorescence and flow cytometry. The released von Willebrand factor (vWF) was measured using ELISA. P-selectin translocation and neutrophil infiltration were measured via immunohistochemical analysis. Changes in VE-cadherin were measured by western blot. Blocking antibodies against TLRs were used to investigate the signaling pathway.

RESULTS

Histone H4 in plasma and BALF increased significantly after OA injection. Histone H4 was closely correlated with the OA dose, which determined the ARDS severity. Pretreatment with histone H4 further aggravated pulmonary edema and death rate, while anti-H4 antibody exerted obvious protective effects. Histone H4 directly activated the endothelia. Endothelial activation was evidently manifested as HS degradation, release of vWF, P-selectin translocation, and VE-Cadherin reduction. The synergistic stimulus of activated endothelia was required for effective neutrophil activation by histone H4. Both TLRs and calcium mediated histone H4-induced endothelial activation.

CONCLUSIONS

Histone H4 is a pro-inflammatory and pro-thrombotic molecule in OA-induced ARDS in mice.

Ursodeoxycholic acid alleviates fat embolism syndrome-induced acute lung injury by inhibiting the p38 MAPK/NF-κB signalling pathway through FXR

Acute lung injury (ALI) caused by fat embolism syndrome (FES) is a disease with high mortality. This study aimed to explore the roles of ursodeoxycholic acid (UDCA) in FES-induced ALI and its underlying mechanisms. An ALI mouse model was established by allografting mouse perinephric fat. For in vitro experiments, human pulmonary microvascular endothelial cells (HPMEC) were treated with FFAs. The effects of UDCA on the expression of farnesoid X receptor (FXR) and the inflammatory response in endothelial cells were investigated. UDCA significantly inhibited the inflammatory response and the expression of proinflammatory markers during FES-induced ALI. UDCA markedly decreased TNF-α and IL-1β expression in vitro. UDCA administration markedly upregulated FXR expression and significantly reduced the phosphorylation of p38 MAPK and NF-κB p65. Knock down FXR expression decreased the effect of UDCA in vivo. Furthermore, knock down FXR expression and overexpressing FXR increased and decreased the inflammatory response, respectively, in vitro. Moreover, administration of a p38 MAPK activator reversed the anti-inflammatory effect of FXR overexpression. UDCA ameliorated inflammation during FES-induced ALI by suppressing p38 MAPK/NF-κB signalling and activating FXR. These findings provide new evidence for the potential of UDCA for FES-induced ALI treatment.

Fat embolism syndrome after trauma: What you need to know

ABSTRACT

Fat embolism syndrome refers to a systemic condition caused by the circulation of fat droplets in the bloodstream, reaching various target organs typically after major bone fractures or related surgical procedures. Although most cases resolve spontaneously, severe instances can lead to significant respiratory failure, neurological damage, and even mortality. Therefore, appropriate prevention, timely diagnosis, and management are crucial for trauma patients at risk. The objective of this review article is to explore the definition, epidemiology, risk factors, clinical presentation, and pathophysiology of fat embolism syndrome. Furthermore, it aims to examine current recommendations for the accurate diagnosis, prevention, and treatment of it, providing a comprehensive guide for the effective management of patients prone to this condition.

Bone marrow embolism: should it result from traumatic bone lesions? A histopathological human autopsy study

Bone marrow embolism (BME) is likely a consequence of fractures in which pulmonary vessels are the most affected. However, some cases of BME were reported in the absence of trauma. Thus, a traumatic injury might not be necessary for developing BME. This study discusses BME cases in patients without signs of fractures or blunt trauma. The discussion addresses various possible mechanisms for the appearance of BME. Options include cancer in which bone marrow metastasis is a suggestive cause. Another proposal is the chemical theory where bone marrow fats are released via lipoprotein lipase in a pro-inflammatory state, resulting in vascular/pulmonary obstruction. Other cases discussed in this study are hypovolemic shock and drug-abuse related BME. All autopsy cases with BME were included regardless of the cause of death for a period of 2 years. Autopsies involved complete dissection with the macroscopic evaluation of the affected organs, including the heart, lungs, and brain. Tissues were also prepared for microscopic examination. Of the 11 cases, eight showed non-traumatic BME (72%). These findings conflict with theories in the literature that BME most commonly occurs after fractures or trauma. One of the eight cases exhibited mucinous carcinoma; one is presented with hepatocellular carcinoma; and two cases showed severe congestion. Lastly, one case was found to be associated with each of the following conditions: liposuction, drug abuse, pulmonary hypertension, and heart failure. Each case suggests a different pathophysiology for developing BME, yet the exact mechanisms are not fully understood. Further study of non-traumatic associated BME is recommended.

Fat embolism syndrome associated with atraumatic compartment syndrome of the bilateral upper extremities: An unreported etiology

Fat embolism syndrome (FES) is a potentially life-threatening condition that develops when fat embolism leads to clinical symptoms and multisystem dysfunction. The classic triad of respiratory distress, neurologic symptoms, and petechial rash are non-specific, and the lack of specific laboratory tests makes the diagnosis of FES difficult. Although FES is most common after long bone fractures, multiple conditions some of which are atraumatic have been associated with the development of FES. We report a case of FES that occurred in the setting of a non-traumatic compartment syndrome of the upper extremities. The pathologic and clinical findings, pathophysiology, diagnostic challenges, and pathologic methods to properly diagnose FES are discussed with a review of the relevant literature. This case highlights the importance of the autopsy in making a diagnosis of FES in cases where death could otherwise be incorrectly attributed to multi-organ system failure, shock, or sepsis.

Fat emboli-Related diffuse alveolar haemorrhage (FEDAH) an acronym to remember-Case series

Fat embolism syndrome (FES) is a rare but potentially fatal complication of trauma or orthopaedic surgery, which presents predominantly with pulmonary symptoms. The rapid worsening respiratory failure in a previously normal orthopaedic surgery or trauma patients usually get evaluated for pulmonary embolism, fat-embolism-related acute respiratory distress or transfusion related acute lung injury. Orthopaedic surgeons and clinicians need to be aware of related entity termed 'Fat Embolism related Diffuse Alveolar Haemorrhage' (FEDAH). The clinical presentation in an orthopaedic surgery of trauma patient with FEDAH are haemoptysis, worsening type 1 respiratory failure and oxygen requirement, drop in haemoglobin levels with chest x-ray/computed tomography suggestive of Diffuse alveolar haemorrhage (DAH). Early bronchoscopy and bronchoalveolar lavage (BAL) confirmation of DAH, presence of BAL haemosiderophages and lipid-laden macrophages are the pointers in the early diagnosis of FEDAH. It needs a high clinical suspicion and interdepartmental collaborative measures. Timely referral from orthopaedic surgeons, early bronchoscopy and treatment with steroids is key in diagnosis and management.

Fat Embolism: A Rare Complication of Bone Biopsy

We report a woman who was admitted to the hospital with a sudden onset of extensive maculopapular erythematous rash involving the trunk and extremities, six weeks after initiating antihypertensive medication. She had atypical lymphocytosis with Gumprecht shadows, elevated liver enzymes, and acute kidney injury. The diagnosis of drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome secondary to antihypertensive drugs was suspected and the antihypertensive drugs were suspended. A hypothesis of lymphoproliferative disease was also considered, and consequently, a myelogram and bone biopsy of the iliac crest were performed. After the procedure, the patient developed acute hypoxemia. After the exclusion of pulmonary thromboembolism by CT angiography, we assumed a presumptive diagnosis of iatrogenic fat embolism syndrome (FES) associated with bone biopsy. The patient deteriorated with worsening hypoxemia and ultimately died. This case represented a diagnostic challenge and highlighted iatrogenesis's undesirable and potentially fatal effects. Careful consideration of the risk-benefit ratio of all medical procedures is paramount in daily medical practice and knowledge of the possible risks is necessary for their early recognition and therapeutic approach.

Fat Pulmonary Embolism With Crazy-Paving Pattern Opacities and Pneumothorax: A Rare Complication of Liposuction

Fat embolism syndrome (FES) is a rare multiorgan disease caused by microvascular obstruction by fat globules and free fatty acid-mediated endothelial injury leading to pro-inflammatory cytokine release. We present a rare case of a 54-year-old woman who underwent elective aesthetic liposuction and developed FES and pneumothorax within 12 hours of the procedure.

Rare case of pulmonary fat embolism and acute respiratory distress syndrome after liposuction and fat grafting: a case report

BACKGROUND

Pulmonary fat embolism usually occurs after fracture, yet rarely observed after liposuction and fat grafting.

CASE PRESENTATION

We describe a 19-year-old female patient who presented with acute respiratory failure and diffuse pulmonary opacities on chest radiographic image shortly after liposuction and fat grafting. Bronchoalveolar lavage was performed and lipid content in alveolar cells contribute to the diagnosis of the fat embolism syndrome. The patient was successfully treated with noninvasive mechanical ventilation and a short course of glucocorticoids.

CONCLUSIONS

Early recognition and appropriate treatment are very important to improve the outcome of pulmonary fat embolism. Considering that liposuction and fat grafting are increasingly common cosmetic surgeries, our aim is to raise awareness for this rare adverse event.

Fat Embolism Syndrome Without Bone Fracture: Is It Possible?

BACKGROUND: Fat embolism syndrome is a life challenge syndrome. Early diagnosing and treatment can significantly improve the patient’s prognosis and likelihood of success. This syndrome occurs mainly after long bones fractures or orthopedic surgery up to 95% of diagnosed cases, but in unusual situation can be faced as well. These rare situations include diabetes mellitus, video-assisted thoracoscopies, fatty liver, and fat injection in plastic and cosmetic procedures. The likelihood of this syndrome can be increased if multiplex long bones fractures occur in the same patient simultaneously. This syndrome is usually manifested with respiratory changes (hypoxemia and ARDS), neurological focal symptoms (confusion, headache, aphasia, and hemiplegia), and skin abnormalities (petechias, and rush in conjunctiva and oral mucosa). The clinical scenario begins typically after 24−72 h of injury, and mainly, respiratory changes are the first, followed by neurological abnormalities and finally petechias as the most significant sign. CASE REPORT: In this case, we report a rare case of unexpected fat embolism syndrome after soft-tissue minimal trauma. This is the first case that we faced according to literature, and the aim of reporting this case is to emphasize that fat syndrome embolism can happen perhaps in every trauma patient even in minor soft-tissue trauma in absence of bone fractures. CONCLUSION: We strongly suggest that this case should make the physicians taking in consideration fat embolism syndrome even if bone fracture missed, to early diagnosing and adequately treating the patient, and optimizing his chances to survive.

Bone marrow necrosis and fat embolism syndrome in sickle cell disease during COVID-19 infection treated successfully with sequential red cell and plasma exchange

Fat embolism syndrome (FES) is a rare life-threatening condition that is particularly seen in milder forms of sickle cell disease (SCD). Widespread systemic fat emboli are generated in the context of extensive bone marrow necrosis. Multi-organ failure with a high morbidity and mortality may quickly develop. Infection with Parvovirus B19 is a common precipitant. Here, the authors report the case of a 35-year-old Afro-Caribbean man with HbSC disease who presented with FES having tested positive for SARS-COV-2. He rapidly became critically ill and required admission to the intensive care unit for organ support. He was treated with red cell exchange and plasma exchange and made a good recovery to leave hospital at week 7.

Ursodeoxycholic acid protects against lung injury induced by fat embolism syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a life‐threatening disease with a high mortality rate, which was a common complication of fat embolism syndrome (FES). Ursodeoxycholic acid (UDCA) has been reported to exert potent anti‐inflammatory effects under various conditions. In vivo, perinephric fat was injected via tail vein to establish a rat FES model, the anti‐inflammatory effects of UDCA on FES‐induced lung injury were investigated through histological examination, ELISA, qRT‐PCR, Western blot and immunofluorescence. In vitro, human lung microvascular endothelial cells (HPMECs) were employed to understand the protective effects of UDCA. The extent of ALI/ARDS was evaluated and validated by reduced PaO₂/FiO₂ ratios, increased lung wet/dry (W/D) ratios and impaired alveolar‐capillary barrier, up‐regulation of ALI‐related proteins in lung tissues (including myeloperoxidase [MPO], vascular cell adhesion molecule 1 [VCAM‐1], intercellular cell adhesion molecule‐1 [ICAM‐1]), elevated protein concentration and increased proinflammatory cytokines levels (TNF‐α and IL‐1β) in bronchoalveolar lavage fluid (BALF). Pre‐treatment with UDCA remarkably alleviated these pathologic and biochemical changes of FES‐induced ALI/ARDS; our data demonstrated that pre‐treatment with UDCA attenuated the pathologic and biochemical changes of FES‐induced ARDS, which provided a possible preventive therapy for lung injury caused by FES.

Fatal diffuse pulmonary fat microemboli following reperfusion in liver transplantation with the use of marginal steatotic allografts

Organ shortage is a major cause of delayed liver transplantation and increased waitlist time. The level of donor steatosis is a significant determinant in organ selection. Scarcity of organs has led some programs to expand their acceptable criteria for the percentage of steatosis. We report two cases of liver transplantation of steatotic donor organs that resulted in mortality within hours from transplantation. Postmortem analysis showed evidence of diffuse pulmonary fat microemboli likely originating from the donor organ, with marked preservation reperfusion injury. The mechanism of diffuse fat microemboli in this setting and possible relationship to other perioperative syndromes (transfusion-related lung injury, acute kidney injury, and postreperfusion syndrome) is discussed.

VEGF mediates fat embolism-induced acute lung injury via VEGF receptor 2 and the MAPK cascade

Fat embolism (FE) is a lethal medical emergency often caused by fracture of long bones and amputation of limbs. Vascular endothelial growth factor (VEGF) promotes angiogenesis and increases vascular permeability. We tested the hypothesis that VEGF plays a critical role in FE-induced acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Fat tissues were collected from male Sprague-Dawley rats, and animal oil was extracted and mixed with water to form fatty micelles. The micelles were then injected into the tail vein to produce FE and ALI in rats. Lung weight gain was measured as the index of pulmonary edema. The expression of pulmonary VEGF was evaluated by real-time PCR and western blot analysis. Inducible nitric oxide synthase (iNOS) and phosphorylation of mitogen-activated protein kinase (MAPK) were determined by western blot analyses. Interleukin-1β (IL-1β) was quantified by ELISAs. Hematoxylin and eosin staining was used to evaluate the pathological damage of ALI. In this study, we found that animal oil-induced FE significantly increased pulmonary VEGF expression and MAPK phosphorylation. We also evaluated the inflammatory response after FE and found that iNOS and IL-1β significantly increased after FE. Systemic administration of SU-1498, an antagonist of VEGF receptor 2 (VEGFR-2), significantly attenuated the FE-induced inflammatory response and histological damage. This study suggested that VEGF is involved in FE-induced ARDS via the VEGFR-2 and MAPK cascades, which induce IL-1β release and iNOS upregulation. Blockade of could be used to treat FE-induced pulmonary damage.

Case 254: Posttraumatic Migrating Fat Embolus Causing Fat Emboli Syndrome

History An otherwise healthy 18-year-old man was admitted to the emergency department with a closed displaced fracture of the left femoral shaft ( Fig 1 ) after a high-velocity motorbike accident. At admission, other physical examination findings were unremarkable. Initial unenhanced and contrast material-enhanced (120 mL of Iomeron 400; Bracco Imaging, Milan, Italy) computed tomography (CT) was performed in the arterial and venous phases from the head to the knees. No abnormalities were noted in the brain or chest at initial CT. [Figure: see text] Within a few hours, the patient developed sudden mental confusion and severe hypoxemia, with rapidly worsening tachypnea and perturbed arterial blood gas with low partial pressure of oxygen (61 mmHg [8.1 kPa]; normal range, 75-100 mmHg [10.0-13.3 kPa]) and low partial pressure of carbon dioxide (32 mmHg [4.3 kPa]; normal range, 38-42 mmHg [5.1-5.6 kPa]). A second contrast-enhanced chest CT examination and initial brain magnetic resonance (MR) imaging were performed. Femoral fracture was stabilized with external fixation, and the patient was admitted to the intensive care unit, with progressive neurologic recovery at day 3 and respiratory improvement at day 4. Treatment included intubation with mechanical ventilation and intravenous administration of steroids and noradrenaline. Afterward, the femoral fracture was stabilized with an intramedullary nail. The patient made a full neurologic recovery 1 month after the accident.

Fat attacks!: a case of fat embolisation syndrome postliposuction

Liposuction is a procedure commonly performed in the UK usually with a low incidence of serious sequelae; however with larger patients and increased volumes of lipoaspirate, complications have been reported more frequently. One of the rare but very serious complications postliposuction is fat embolism syndrome (FES), a life-threatening condition difficult to diagnose and limited in treatment.The authors present the case of a 45-year-old woman who was admitted to the intensive care unit postelective liposuction for bilateral leg lipoedema. She presented with the triad of respiratory failure, cerebral dysfunction and petechial rash requiring a brief period of organ support. This case highlights that with the recent increase in liposuction procedures worldwide, FES is a differential to always consider. Although still a rare condition this article emphasises the importance of thinking outside the box and how to identify and manage such a life-threatening complication.

Fat Embolism Syndrome: Lung Computed Tomography Findings in 18 Patients

OBJECTIVE

The purpose of this study was to evaluate the lung computed tomography (CT) findings in fat embolism (FE) syndrome.

METHODS

We retrospectively evaluated 19 CT examinations of 18 patients with FE syndrome, diagnosed clinically using the Gurd and Wilson criteria.

RESULT

Fat embolism syndrome showed 3 patterns: negative examination, bilateral interstitial-alveolar involvement, and adult respiratory distress syndrome like. Frequent findings included consolidations (17 patients), mostly with gravity dependent distribution, and ground-glass opacities (17 patients), mostly with patchy distribution. Fifteen patients showed an overlapping random nodular pattern. Less common findings included lobular ground-glass opacities and lobular consolidations, smooth septal thickening, thickening of the bronchial wall, and areas of crazy paving. The extension of the consolidations correlates with the duration of assisted ventilation.

CONCLUSIONS

In FE syndrome, pulmonary CT findings are ground-glass opacities and dependent consolidations, associated with other variably overlapping signs, such as lobular opacities, random nodules, septal thickening, and bronchial wall thickening.

Pulmonary embolism after arterial chemoembolization for hepatocellular carcinoma: An autopsy case report

We report an extremely rare case of pulmonary lipiodol embolism with acute respiratory distress syndrome (ARDS) after transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC). A 77-year-old man who was diagnosed with a huge HCC was admitted for TACE. Immediately after the procedure, this patient experienced severe dyspnea. We suspected that his symptoms were associated with a pulmonary lipiodol embolism after TACE, and we began intensive treatment. However, his condition did not improve, and he died on the following day. A subsequent autopsy revealed that the cause of death was ARDS due to pulmonary lipiodol embolism. No cases have been previously reported for which an autopsy was performed to explain the most probable mechanism of pulmonary lipiodol embolism; thus, ours is the first report for such a rare case.

Lipiodol embolism following transarterial chemoembolization: an atypical case

OBJECTIVE

Transarterial chemoembolization is a widely used therapy for the treatment of hepatocellular carcinoma. A rare adverse event is acute respiratory distress syndrome from pulmonary embolization of Lipiodol, an iodinated oil commonly used during the procedure. The objective of this report is to describe an atypical case of acute respiratory distress syndrome from Lipiodol embolization in a patient who underwent transarterial chemoembolization for hepatocellular carcinoma 9 days prior to presentation, despite having received relatively small amounts of Lipiodol (5.5 mL). Although this diagnosis has classically been based on radiological findings, we established a diagnosis after lipid-laden macrophages were detected in bronchial alveolar lavage fluid.

DESIGN

Case report.

SETTING

ICU of a major metropolitan academic medical center.

PATIENTS

Single case.

INTERVENTIONS

Diagnostic interventions included noncontrast CT scan of the chest and cytologic examination of bronchial alveolar lavage fluid with oil red O staining. Therapeutic interventions included mechanical ventilation and methylprednisolone infusions.

MEASUREMENTS AND MAIN RESULTS

Noncontrast CT demonstrated nonspecific diffuse ground glass opacification, most prominent within the upper lobes. Mechanical ventilation was begun for hypoxemic respiratory failure. Cytologic examination of bronchial alveolar lavage fluid revealed a high proportion of lipid-laden macrophages, findings consistent with Lipiodol embolism. Despite infusions of methylprednisolone, the patient expired on hospital day 8.

CONCLUSIONS

Acute respiratory distress syndrome from Lipiodol embolization following transarterial chemoembolization can occur even with small Lipiodol volumes. Cytologic examination of bronchial alveolar lavage fluid with oil red O staining is a useful diagnostic modality, especially when imaging studies are equivocal.

Automatic protective ventilation using the ARDSNet protocol with the additional monitoring of electrical impedance tomography

INTRODUCTION

Automatic ventilation for patients with respiratory failure aims at reducing mortality and can minimize the workload of clinical staff, offer standardized continuous care, and ultimately save the overall cost of therapy. We therefore developed a prototype for closed-loop ventilation using acute respiratory distress syndrome network (ARDSNet) protocol, called autoARDSNet.

METHODS

A protocol-driven ventilation using goal-oriented structural programming was implemented and used for 4 hours in seven pigs with lavage-induced acute respiratory distress syndrome (ARDS). Oxygenation, plateau pressure and pH goals were controlled during the automatic ventilation therapy using autoARDSNet. Monitoring included standard respiratory, arterial blood gas analysis and electrical impedance tomography (EIT) images. After 2-hour automatic ventilation, a disconnection of the animal from the ventilator was carried out for 10 seconds, simulating a frequent clinical scenario for routine clinical care or intra-hospital transport.

RESULTS

This pilot study of seven pigs showed stable and robust response for oxygenation, plateau pressure and pH value using the automated system. A 10-second disconnection at the patient-ventilator interface caused impaired oxygenation and severe acidosis. However, the automated protocol-driven ventilation was able to solve these problems. Additionally, regional ventilation was monitored by EIT for the evaluation of ventilation in real-time at bedside with one prominent case of pneumothorax.

CONCLUSIONS

We implemented an automatic ventilation therapy using ARDSNet protocol with seven pigs. All positive outcomes were obtained by the closed-loop ventilation therapy, which can offer a continuous standard protocol-driven algorithm to ARDS subjects.

Autopsy diagnosis of fat embolism syndrome

The fat embolism syndrome (FES) is considered a clinical diagnosis. It typically occurs within several days following major traumatic injury, usually involving fractures of the pelvis and/or lower extremities. Fat embolism syndrome is characterized by the onset of respiratory, neurological, cutaneous, and hematologic manifestations and is thought to be related to intravascular embolization of fat, presumably arising from within the fractured bone marrow space. In its most severe form, FES can be lethal. The presence of fat emboli within the microvasculature of the lungs, brain, and sometimes other organs verifies the clinical impression of FES. Despite its relatively well-known clinical characterization, debate exists within the clinical literature regarding the most appropriate diagnostic criteria for FES. Given this fact, along with the fact that FES is a clinical diagnosis, it is not surprising that forensic pathologists may be somewhat reluctant to make a postmortem diagnosis of FES, especially in cases where insufficient clinical information is available. A case of fatal FES is presented in which rapid clinical deterioration occurred, followed by death, such that a clinical diagnosis of FES was never rendered. We propose that, given the correct circumstances, clinical scenario, and autopsy findings, it is appropriate and acceptable to make a postmortem diagnosis of FES. A multitiered approach to the postmortem diagnosis of FES is presented.

Pulmonary fat embolism and related effects during femoral intramedullary surgery: An experimental study in dogs

The aim of the present study was to develop an animal model of pulmonary fat embolism (PFE) caused by femoral intramedullary procedures, and to investigate the initial changes in the hemodynamics, cytokines and risk factors of PFE. Sixteen dogs were randomly divided into two groups: Group A (intramedullary reaming and bone cement injection, n=8) and Group B (surgical approach without opening the medullary cavity, n=8). The hemodynamics, arterial blood gases and relevant cytokines were evaluated, and the lungs were examined using Oil Red O staining. In the animals of Group A, the heart rate, central venous pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure and extravascular lung water (EVLW) were increased compared with the baseline levels, while the mean arterial pressure was decreased immediately following the reaming and bone cement infusion (P<0.05). Furthermore, there was a significant reduction in the pH and the arterial oxygen tension (PaO₂), and a significant increase in the arterial carbon dioxide tension (PaCO₂; P<0.05 for all) following the bilateral intramedullary surgery. The EVLW was correlated with the PaO₂ (P<0.001) and PaCO₂ (P=0.046). Following surgery, there was a significant increase in tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 levels in Group A (P<0.05). However, there were no significant changes in these parameters in Group B. The parameters tested, with the exception of pH, were significantly different in Group A compared with those in Group B (P<0.05) following the bilateral intramedullary surgery. Oil Red O staining was positive for all animals in Group A and negative for those in Group B. Femoral intramedullary surgery may induce PFE and subsequently affect hemodynamics and arterial blood gases. EVLW was correlated with the PaO₂ (P<0.001) and the PaCO₂ (P=0.046). These results demonstrated that EVLW and cytokines may serve as predictors of the development of fat embolism syndrome (FES).

Fatal fat embolism syndrome in a case of isolated L1 vertebral fracture-dislocation

Although fat embolism syndrome is a well-known complication of fractures of the long bones or pelvis, fat embolism syndrome occurring subsequent to fracture of the lumbar spine is rare. We report a fatal case of fat embolism syndrome characterized by fat and bone marrow embolism that occurred 36 h after an isolated fracture-dislocation of the L1 vertebra. A postmortem examination was performed and pathological finding demonstrated fat and bone marrow tissue which were disseminated in the bilateral pulmonary arteries. We need to be aware of the possibility of fat embolism syndrome as a complication of spinal fractures, including isolated vertebral body fractures.

Acute lung injury and acute respiratory distress syndrome: experimental and clinical investigations

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) can be associated with various disorders. Recent investigation has involved clinical studies in collaboration with clinical investigators and pathologists on the pathogenetic mechanisms of ALI or ARDS caused by various disorders. This literature review includes a brief historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the long-term experimental studies and clinical investigations from our laboratory, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Acute respiratory distress syndrome and lung injury: Pathogenetic mechanism and therapeutic implication

To review possible mechanisms and therapeutics for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). ALI/ARDS causes high mortality. The risk factors include head injury, intracranial disorders, sepsis, infections and others. Investigations have indicated the detrimental role of nitric oxide (NO) through the inducible NO synthase (iNOS). The possible therapeutic regimen includes extracorporeal membrane oxygenation, prone position, fluid and hemodynamic management and permissive hypercapnic acidosis etc. Other pharmacological treatments are anti-inflammatory and/or antimicrobial agents, inhalation of NO, glucocorticoids, surfactant therapy and agents facilitating lung water resolution and ion transports. β-adrenergic agonists are able to accelerate lung fluid and ion removal and to stimulate surfactant secretion. In conscious rats, regular exercise training alleviates the endotoxin-induced ALI. Propofol and N-acetylcysteine exert protective effect on the ALI induced by endotoxin. Insulin possesses anti-inflammatory effect. Pentobarbital is capable of reducing the endotoxin-induced ALI. In addition, nicotinamide or niacinamide abrogates the ALI caused by ischemia/reperfusion or endotoxemia. This review includes historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Effects of phorbol myristate acetate and sivelestat on the lung injury caused by fat embolism in isolated lungs

Background

Fat embolism syndrome (FES) associated with acute lung injury (ALI) is a clinical condition following long bone fracture. We have reported 14 victims due to ALI with FES. Our laboratory has developed an animal model that produced fat emboli (FE). The major purpose of this study was to test whether neutrophil activation with phorbol myristate acetate (PMA) and inhibition with sivelestat (SVT) exert protection on the lung.

Methods

The lungs of Sprague-Dawley rats were isolated and perfused. FE was produced by addition of corn oil micelles into the lung perfusate. PMA and SVT were given simultaneously with FE. Parameters such as lung weight/body weight ratio, LW gain, exhaled nitric oxide (NO), protein concentration in bronchoalveolar lavage relating to ALI were measured. The neutrophil elastase (NE), myeloperoxidase, malondialdehyde and phopholipase A₂ activity were determined. We also measured the nitrate/nitrite, methyl guanidine (MG), and cytokines. Pulmonary arterial pressure and microvascular permeability were assessed. Lung pathology was examined and scored. The inducible and endothelial NO synthase (iNOS and eNOS) were detected.

Results

FE caused ALI and increased biochemical factors. The challenge also resulted in pulmonary hypertension and increased microvascular permeability. The NE appeared to be the first to reach its peak at 1 hr, followed by other factors. Coadministration with PMA exacerbated the FE-induced changes, while SVT attenuated the effects of FE.

Conclusions

The FE-induced lung changes were enhanced by PMA, while SVT had the opposite effect. Sivelestat, a neutrophil inhibitor may be a therapeutic choice for patients with acute respiratory distress syndrome (ARDS) following fat embolism.

Use of low-dose steroids in decreasing cytokine release during bilateral total knee replacement

BACKGROUND

Interleukin 6 (IL-6), a marker of inflammation, is one of the major cytokines released during joint replacement. In the orthopedic patient population, high levels have been linked to many adverse effects including acute respiratory distress syndrome, postoperative mental status changes, and fever. We looked to assess the efficacy of low-dose steroids on the postinflammatory response as measured by IL-6 in patients undergoing bilateral total knee replacement (BTKR). The role of steroids has never been evaluated before in that setting.

METHODS

Double-blind, randomized, placebo-controlled study of 30 patients undergoing BTKR. The study was powered in order to detect at least a 25% decrease in IL-6 from control. Hydrocortisone (100 mg) or placebo was given at 2 doses 8 hrs apart to the study and control group respectively. Clinical outcome was assessed as well.

RESULTS

Levels of IL-6 were 40% lower in the study group by 10 hrs (P = 0.0037) but were similar to the control group at 24 hrs. Greater hemodynamic stability was noted in the study group with fewer episodes of hypotension postoperatively (P = 0.031). Range of motion gained on discharge was also greatest in the study group (P = 0.049). Absence of infection and normal wound healing were noted in all patients.

CONCLUSIONS

The use of hydrocortisone significantly decreased the inflammatory response in patients undergoing BTKR as measured by IL-6 production. Further studies looking at clinical implications of such findings in a larger patient population and with a longer course of steroids are warranted.

[Intra-alveolar hemorrhage: rare presentation of fat pulmonary embolism]

INTRODUCTION

Fat embolism syndrome is a severe complication of long bone fractures, corresponding to the obstruction of small vessels by microdroplets of fat, originating from medulla ossium. Pulmonary involvement, present in 90% cases, makes the severity of the disease.

CASE REPORT

We report the case of a 22-year-old man who presented, two days after industrial accident causing an opened tibial fracture, acute dyspnea with hemoptysis. Angio-CT-scan didn't show any proximal vascular obstruction, but parenchymal sections showed diffuse, bilateral and multifocal hyperdensities predominating at the periphery. Broncho-alveolar lavage brought a hemorrhagic liquid, with a high macrophage content and lipid inclusions in macrophages. Exams for the etiologic diagnosis of intra-alveolar hemorrhage were negative: renal function, 24-hour proteinuria, antinuclear antibodies, antineutrophil cytoplasmic antibodies. The diagnosis of intra-alveolar hemorrhage secondary to fat embolism was established. The outcome was spontaneously favorable.

CONCLUSION

The occurrence of intra-alveolar hemorrhage in the course fat embolism is rarely reported. Its pathogenic mechanisms are not understood. It is mandatory to eliminate the other causes of alveolar hemorrhage before holding the diagnosis of fat embolism. Treatment is only symptomatic, based on respiratory reanimation.

Fat embolism: evolution of histopathological changes in the rat lung

The pathophysiology of Fat Embolism Syndrome (FES) is poorly understood and subject to some controversy. Evaluation of the evolution of histological changes in the lungs of patients with FES is impractical. The current theories of FES were established through acute clinical observations and acute animal experiments, but sequential changes in the histology of lungs over a prolonged period have not been made. The progressive effects of fat embolization of the lungs were examined in a rat model over a period of 11 days. Triolein, a major bone marrow fat, was administered to conscious Sprague-Dawley rats via the caudal vein. Rats were euthanized at 24, 48, 96 h, and 11 days, but some died within a few hours. Histomorphometric evaluations of lung tissue were made, including stains for fat, collagen, and smooth muscle actin. Arterial and arteriolar patency decreased progressively up to 96 h, but returned toward normal after 11 days. A striking finding was the very early presence of inflammation and fibrosis after only several hours, persisting up to 11 days. The results of this study provide evidence of both very early and prolonged changes due to fat embolization.

Acute respiratory distress syndrome after transcatheter arterial chemoembolization of hepatocellular carcinomas

BACKGROUND

Acute respiratory distress syndrome (ARDS) associated with pulmonary lipiodol embolism is a rare complication of transcatheter arterial chemoembolization (TACE). We performed a survey of ARDS associated with pulmonary lipiodol embolism after TACE.

METHODS

A retrospective analysis of the cases of all patients with hepatic tumors who received transcatheter arterial embolization or TACE between January 2006 and December 2006 was performed. The diagnosis of pulmonary lipiodol embolism was confirmed by chest computed tomography (CT).

RESULTS

The diagnosis of ARDS associated with pulmonary lipiodol embolism was confirmed in 4 patients. All had large (> or =5 cm) and hypervascular tumors. There was no evidence of hepatocellular carcinoma arteriovenous shunting in any of our patients as determined by angiography and multidetector CT. The volumes of lipiodol infused in the 4 patients were 50, 20, 30, and 20 mL. Only 2 patients received injections of carcinostatic agents. The onset of respiratory symptoms occurred between 1 hour and 4 days after TACE. Respiratory symptoms consisted of dyspnea and tachypnea. Chest CT scans revealed linear high-density shadows, suggestive of lipiodol retention in both lungs of all patients.

CONCLUSION

Pulmonary lipiodol embolism after TACE can occur within a short time frame. Whether or not there is intrahepatic arteriovenous shunting detected by multidetector CT and angiography, clinicians should avoid high doses of iodized oil and carcinostatic agents. We suggest that CT should be used for the diagnosis of pulmonary lipiodol embolism.

Fat embolism

Fat embolism refers to the presence of fat droplets within the peripheral and lung microcirculation with or without clinical sequelae. The pathologic consequences of fat embolism are well recognized. Fat embolism is most often associated with trauma and orthopedic injuries. Fat embolism syndrome (FES) is a serious manifestation of fat embolism that involves a cascade of clinical signs such as petechial rash, deteriorating mental status, and progressive respiratory insufficiency, usually occurring within 24 hours of injury. This article reviews the definition, epidemiology, etiology, pathophysiology, clinical presentation, diagnosis, management, and prognosis of FES.

Histopathological and biochemical changes following fat embolism with administration of corn oil micelles

Several experimental models have been used to produce intravascular fat embolism. We have developed a simple technique to induce fat embolism using corn oil emulsified with distilled water to form fatty micelles. Fat embolism was produced by intravenous administration of these fatty micelles in anaesthetised rats, causing alveolar oedema, haemorrhage and increased lung weight.

Histopathological examination revealed fatty droplets and fibrin thrombi in the lung, kidney and brain. The arteriolar lumen was filled with fatty deposits. Following fat embolism, hypoxia and hypercapnia occurred. The plasma phospholipase A2, nitrate/nitrite, methylguidanidine and proinflammatory cytokines were significantly increased. Mass spectrometry showed that the main ingredient of corn oil was oleic acid.

This simple technique may be applied as a new animal model for the investigation of the mechanisms involved in the fat embolism syndrome.

Fat embolism syndromes following liposuction

Fat embolism syndrome (FES) after liposuction is likely a life-threatening disorder, though its incidence is low. The three chief clinical manifestations include respiratory insufficiency, cerebral involvement, and petechial rash. Although FES is a multisystem disorder, the most seriously affected organs are the lungs, brain, cardiavascular system, and skin. Many laboratory findings are characteristic but nonspecific. The pathogenesis of FES after liposuction has been looked at both mechanically and biochemically. Diagnosis is difficult; Gurd and Wilson's diagnostic criteria based on clinical examination is still extensively used in clinics at present. There is no specific therapy for FES after liposuction for the moment, so prevention, early diagnosis, and supportive therapies are important. In this article we discuss the clinical presentation, pathogensis, and current methods to prevent FES and, if possible, ways to treat this complication.

Protective effects of propofol on acute lung injury induced by oleic acid in conscious rats

OBJECTIVES

Oleic acid has been used to induce acute lung injury (ALI) in animals. In patients with acute respiratory distress syndrome (ARDS), the blood level of oleic acid was increased. The mechanism and therapeutic regimen of ARDS and oleic acid-induced ALI remain undefined. In the present study, we investigated the oleic acid-induced changes in lung variables for the measure of ALI, inflammatory mediators, and neutrophil-derived substances. We evaluated the effects of pretreatment and posttreatment with propofol.

DESIGN

Randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Fifty adult male Sprague-Dawley rats weighing 250-300 g.

INTERVENTIONS

We employed a conscious and unrestrained rat model. Oleic acid at a dose of 100 mg/kg was administered intravenously. Propofol (30 mg/kg) was given by intravenous infusion (6 mg/kg/min for 5 mins) 30 mins before (pretreatment) and 30 mins after (posttreatment) oleic acid.

MEASUREMENTS AND MAIN RESULTS

We monitored the arterial pressure, heart rate, and blood gas. The lung weight changes, exhaled nitric oxide, protein concentration in bronchoalveolar lavage, and Evans blue content in lung tissue were determined. The plasma nitrate/nitrite, methylguanidine, cytokines (tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, and interleukin-10), neutrophil elastase, myeloperoxidase, malondialdehyde, and sodium- and potassium-activated adenosine triphosphatase (Na+-K+-ATPase) were detected. Histopathological examination of the lung was performed. Oleic acid caused systemic hypotension and severe ALI as evidenced by the increases in the extent of ALI, impairment of pulmonary functions (blood gas variables), and lung pathology. In addition, oleic acid significantly increased inflammatory mediators and neutrophil-derived factors but depressed Na+-K+-ATPase. The inducible nitric oxide synthase was up-regulated. Pre- or posttreatment with propofol was capable of reversing the oleic acid-induced changes and attenuating the extent of ALI.

CONCLUSIONS

Oleic acid resulted in sepsis-like responses including ALI, inflammatory reaction, and increased neutrophil-derived factors. It depressed the Na+-K+-ATPase activity but up-regulated inducible nitric oxide synthase. Treatment with propofol abrogated or reversed the oleic acid-induced changes.

N-acetylcysteine attenuates acute lung injury induced by fat embolism

OBJECTIVES

Fat embolism syndrome is a clinical issue in subjects with long-bone fracture. It may lead to acute lung injury. The mechanisms and therapeutic regimen remain unclear. The present study was designed to investigate the pathologic and biochemical changes after fat embolization in isolated rat lungs, and to test the effects of posttreatment with N-acetylcysteine (NAC).

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

A total of 36 perfused lungs isolated from Sprague-Dawley rats.

INTERVENTIONS

The isolated lungs were randomly assigned to receive physiologic saline solution (vehicle group), fat embolism (FE group), or FE with NAC posttreatment (FE + NAC group). There were 12 isolated lungs in each group. FE was produced by introduction of corn oil micelles. NAC at a dose 150 mg/kg was given 10 mins after FE.

MEASUREMENTS AND MAIN RESULTS

The extent of acute lung injury was evaluated by lung weight change, protein concentration in bronchoalveolar lavage, and exhaled nitric oxide. We also measured the pulmonary arterial pressure and capillary filtration coefficient and determined the nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate. Histopathologic changes of the lung were examined and quantified. The levels of neutrophil elastase and myeloperoxidase were determined. The expression of inducible nitric oxide synthase was detected. FE caused acute lung injury as evidenced by the lung weight changes, increases in exhaled nitric oxide and protein concentration in bronchoalveolar lavage, pulmonary hypertension, increased capillary filtration coefficient, and lung pathology. The insult also increased nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate, increased neutrophil elastase and myeloperoxidase levels, and upregulated inducible nitric oxide synthase expression. Posttreatment with NAC abrogated these changes induced by FE.

CONCLUSION

FE caused acute lung injury and associated biochemical changes. Posttreatment with NAC was effective to alleviate the pathologic and biochemical changes caused by FE.