Autopsy diagnosis of fat embolism syndrome

Fat embolism: a systematic review to facilitate the development of standardised procedures in pathology

Fat embolism (FE) is a historically recognised but still actively researched topic in forensic pathology. Several aspects remain not fully elucidated, such as its aetiopathogenesis, its causal role in death determination, the impact of interfering factors (e.g. cardiopulmonary resuscitation or other medical procedures) and both qualitative and quantitative diagnostic methodologies in clinical and forensic contexts. These issues are further underscored by the potential involvement of FE in the causal determination of non-traumatic deaths, which often raises questions of professional liability. The present study aims to provide a comprehensive and up-to-date overview of the most recent scientific evidence relevant to forensic pathology. Our systematic research has included 58 articles from 1990 to the present on the topic of FE and fat embolism syndrome (FES). From these articles, we identified 45 case reports, from which the authors' descriptions were extracted to provide information on individual cases and the operational methods of forensic pathologists. Additionally, 21 experimental studies were identified, and their key findings have been summarised narratively. It has emerged that both traumatic and non-traumatic cases are frequently reported in the forensic context, with orthopaedic and cosmetic surgery being among the highest-risk specialities. Experimental studies have re-evaluated the role of a patent foramen ovale in the pathogenesis of FE, as well as the impact of cardiopulmonary resuscitation in causing FE severe enough to result in death. Additionally, there are new findings regarding diagnostic techniques, including radiological and immunohistological methods; however, they have not yet fully bridged the reliability gap compared to an accurate autopsy-histological evaluation. The major critical points that emerged include the lack of complete and detailed information on premortem clinical conditions, the underutilisation of grading systems and the methodological heterogeneity applied, resulting in considerable variability regarding the organs studied histologically and the diagnostic techniques used. Despite the limitations associated with the analysis of case reports and the heterogeneity of included experimental studies, we believe that this study can provide a comprehensive overview of the FE topic. It furnishes pathologists with an updated overview useful for clinical practice and guiding future research trends, as well as facilitating the development of standardised procedures.

Is That Innocent to Touch the Adipose Tissue?: An Autopsy Case Series of Fat Embolism Syndrome

ABSTRACT

Although fat embolism in the pulmonary or systemic circulation is usually associated with long bone fractures, it can also occur less frequently during surgical operations, such as liposuction, fat grafting, and joint repair. This study aims to present cases of macro fat embolism resulting in sudden death during the perioperative period. Three cases with a history of sudden death during the perioperative period were included in this study. The surgical operation histories, autopsy findings, and histopathological findings of the cases were evaluated. Fat globules were detected in the medium-sized vessel lumens in the lungs of the cases who died suddenly during surgery. Grade 4 fat embolism was observed in the capillaries, which stained positively with Oil-Red-O in all three cases. Fat embolism syndrome is a rare but life-threatening condition that should be considered in patients with respiratory distress and impaired neurological status in the postoperative period.

Pulmonary fat embolism in non-survivors after cardiopulmonary resuscitation

BACKGROUND

Blunt trauma acting against the human body presents the fundamental cause of pulmonary fat embolism (PFE) and fat embolism syndrome. The aim of the present study was to investigate PFE in non-survivors after cardiopulmonary resuscitation (CPR).

METHODS

This was a prospective cohort study conducted in University Hospital Ostrava, Czech Republic. Within a 4-year study period, all non-survivors after CPR because of out-of-hospital cardiac arrest were assessed for the study eligibility. The presence/seriousness of PFE was determined by microscopic examination of cryo-sections of lung tissue (staining with Oil Red O).

RESULTS

In total, 106 persons after unsuccessful CPR were enrolled in the study. The most frequent cause of death in the study population (63.2% of cases) was cardiac disease (ischemic heart disease); PFE was not determined as the cause of death in any of our study cases. Sternal fractures were identified 66.9%, rib fractures (usually multiple) in 80.2% of study cases; the median number of rib fractures was 10.2 fractures per person. Serious intra-thoracic injuries were found in 34.9% of cases. Microscopic examination of lung cryo-sections revealed PFE in 40 (37.7%) study cases; PFE was most frequently evaluated as grade I or II. Occurrence of sternal and rib fractures was significantly higher in persons with PFE than between persons without PFE (p = 0.033 and p = <0.001). Number of rib fractures was also significantly higher in persons with PFE. The occurrence of serious intra-thoracic injuries was comparable in both our study groups (p = 0.089).

CONCLUSIONS

PFE presents a common resuscitation injury which can be found in more than 30% of persons after CPR. Persons with resuscitation skeletal chest fractures have significantly higher risk of PFE development. During autopsy of persons after unsuccessful CPR, it is necessary to distinguish CPR-associated injuries including PFE from injuries that arise from other mechanisms.

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.

A case of fatal fulminant fat embolism syndrome following multiple fractures resulting from a fall

Fat embolism syndrome is a life-threatening condition in which fatty substances enter the circulation and cause respiratory distress and neurological symptoms. It can occur following trauma and severe fat embolism occurring soon after trauma is known as fulminant fat embolism syndrome. Although fat staining of the lungs is helpful for diagnosing fat embolism syndrome at autopsy, clinical and other information is needed to determine the relationship between cause of death and the syndrome. In this report, we describe the macroscopic, microscopic, and computed tomography (CT) findings specific for fat embolism that were observed in a patient with fulminant fat embolism syndrome who died soon after the injury. An 85-year-old woman fell from a bath stretcher during assisted bathing and died 3 h later. Autopsy revealed fractures of the left femoral neck and other bones, as well as large amounts of fat-like material in the right and left pulmonary arteries. Histological examination of the lung with Oil red O staining showed extensive fat vacuoles. Based on these findings and postmortem CT images of the fractures and fatty globules in the pulmonary arteries detected prior to death, the cause of death was determined to be blunt force trauma, with fat embolism syndrome playing a significant role. This case is an example of fulminant fat embolism, which can be fatal in a short period of time, and demonstrates that CT performed postmortem but before autopsy can be useful in detecting fat embolism syndrome due to trauma.

Increased early mortality after total knee arthroplasty using conventional instrumentation compared with technology-assisted surgery: an analysis of linked national registry data

OBJECTIVES

This study aims to compare early mortality after total knee arthroplasty (TKA) using conventional intramedullary instrumentation to TKA performed using technology-assisted (non-intramedullary) instrumentation.

DESIGN

Comparative observational study. Using data from a large national registry, the 30-day mortality after unilateral TKA performed for osteoarthritis was compared between procedures using conventional instrumentation and those using technology-assisted instrumentation. Firth logistic regression was used to calculate ORs, adjusting for age, sex, use of cement and procedure year for the whole period, and additionally adjusting for American Society of Anesthesiologists physical status classification system class and body mass index (BMI) for the period 2015 to 2019. This analysis was repeated for 7-day and 90-day mortality.

SETTING

National arthroplasty registry.

PARTICIPANTS

People undergoing unilateral, elective TKA for osteoarthritis from 2003 to 2019 inclusive.

INTERVENTIONS

TKA performed using conventional intramedullary instrumentation or technology-assisted instrumentation.

MAIN OUTCOME MEASURES

30-day mortality (primary), and 7-day and 90-day mortality.

RESULTS

A total of 581 818 unilateral TKA procedures performed for osteoarthritis were included, of which 602 (0.10%) died within 30 days of surgery. The OR of death within 30 days following TKA performed with conventional instrumentation compared with technology-assisted instrumentation, adjusted for age, sex, cement use, procedure year, American Society of Anesthesiologists and BMI was 1.72 (95% CI, 1.23 to 2.41, p=0.001). The corresponding ORs for 7-day and 90-day mortality were 2.21 (96% CI, 1.34 to 3.66, p=0.002) and 1.35 (95% CI, 1.07 to 1.69, p=0.010), respectively.

CONCLUSIONS

The use of conventional instrumentation during TKA is associated with higher odds of early postoperative death than when technology-assisted instrumentation is used. This difference may be explained by complications related to fat embolism secondary to intramedullary rods used in conventional instrumentation. Given the high number of TKA performed annually worldwide, increasing the use of technology-assisted instrumentation may reduce early post-operative mortality.

Increased Early Mortality in Bilateral Simultaneous TKA Using Conventional Instrumentation Compared with Technology-Assisted Surgery: A Study of 34,908 Procedures from a National Registry

BACKGROUND

Controversy exists regarding the safety of bilateral simultaneous total knee arthroplasty (BSTKA). When conventional instrumentation is used, the increased fat emboli that result from the insertion of intramedullary rods may increase the risk of perioperative complications. We hypothesized that the use of technology-assisted instrumentation (avoiding intramedullary involvement) would be associated with a lower rate of early postoperative death compared with the use of conventional instrumentation.

METHODS

We compared the 30 and 90-day rates of mortality following BSTKA performed with conventional versus technology-assisted instrumentation from 2003 to 2019, with use of data from a large national registry. Firth logistic regression analysis was utilized, adjusting for age, sex, and procedure year for all BSTKAs performed during the study period. For procedures performed from 2015 to 2019, odds ratios were additionally adjusted for American Society of Anesthesiologists physical status classification and body mass index.

RESULTS

A total of 34,908 BSTKAs were identified. The proportion of cases utilizing technology-assisted instrumentation increased over the study period. The odds ratio of death within 30 days after technology-assisted BSTKA, adjusted for age, sex, and procedure year, was 0.26 (95% confidence interval [CI], 0.08 to 0.83; p = 0.02). The odds ratio, adjusted for age, sex, procedure year, American Society of Anesthesiologists classification, and body mass index, was 0.26 (95% CI, 0.09 to 0.74; p = 0.01). The corresponding odds ratios for 90-day mortality were 0.25 (95% CI, 0.09 to 0.72; p = 0.01) and 0.26 (95% CI, 0.10 to 0.67; p = 0.005), respectively.

CONCLUSIONS

Technology-assisted BSTKA was associated with a significant reduction in early mortality compared with the use of conventional instrumentation. This difference may be explained by the reduced fat emboli associated with technology-assisted BSTKA and is likely to be clinically important on a population scale.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Application of Immunohistochemistry and Special Staining Technique in Forensic Traumatic Pathology Identification

In forensic traumatic pathology practice, immunohistochemistry and special staining technique play an important role in wound age estimation and complications of traumatic complication identification. They even play an important role in the identification of special cases, such as snakebites and insulin killings. This article reviews the application and value of immunohistochemistry and special staining techniques in forensic traumatic pathology based on the cases of forensic practice reported in literature.

Fat Embolism, Fat Embolism Syndrome and the Autopsy

Fat embolism is common following trauma and is a common autopsy finding in these cases. It may also be seen in non-traumatic cases and is seen in children as well as adults. In comparison fat embolism syndrome (FES) only occurs in a small number of trauma and non-trauma cases. Clinical diagnosis is based on characteristic clinical and laboratory findings. Fat embolism exerts its effect by mechanical blockage of vessels and/or by biochemical means including breakdown of fat to free fatty acids causing an inflammatory response. Fat embolism can be identified at autopsy on microscopy of the lungs using fat stains conducted on frozen tissue, including on formalin fixed but not processed tissue. With FES fat emboli can be seen in other organs including the brain, kidney and myocardium. Fat can also be identified with post-fixation staining, typically with osmium tetroxide. Scoring systems have been developed to try and determine the severity of fat embolism in lung tissue. Fat embolism is also common following resuscitation. When no resuscitation has taken place, the presence of fat on lung histology has been used as proof of vitality. Diagnosis of fat embolism syndrome at autopsy requires analysis of the history, clinical and laboratory findings along with autopsy investigations to determine its relevance, but is an important diagnosis to make which is not always identified clinically. This paper reviews the history, clinical and laboratory findings and diagnosis of fat embolism and fat embolism syndrome at autopsy.

Approaching pulmonary fat embolism on postmortem computed tomography

PURPOSE

Pulmonary fat embolism (PFE) is a relevant diagnosis playing a role as a sign of vitality or a cause of death. Its severity is assessed according to histological grading systems like that of Falzi. The aim of this study was to determine the utility of unenhanced postmortem computed tomography (PMCT) for PFE diagnosis based on the detection of fat layers.

METHODS

Consecutive cases with PMCT and autopsy were studied retrospectively. The case group consisted of cases with positive PFE, and the control group included cases with negative PFE. Three observers independently assessed PMCT data for fat layers in the pulmonary trunk and the right and left pulmonary artery. For cases with fat layers, autopsy protocols were assessed for the cause of death, relation to trauma, and undertaken resuscitation measures.

RESULTS

Eight hundred thirty cases were included: 366 PFE positive cases (144 of Falzi grade 1, 63 of 1.5, 99 of 2, 28 of 2.5, and 32 of 3) and 464 PFE negative cases. Interrater reliabilities varied between substantial and almost perfect, and discrepancies were solved according to majority. Eighteen cases showed fat layers on PMCT (2 controls-traumatic instantaneous deaths-, 16 PFE positive cases). PMCT showed low sensitivity but high specificity for PFE diagnosis. The layers were located at the same position in the pulmonary trunk directly adjacent to the pulmonary valve distal to the right ventricle.

CONCLUSION

Fat layer on PMCT is a rare finding but relates to PFE diagnosis, especially of severe histological grade. It is to be expected in a typical position within the pulmonary trunk.

Liposuction-Induced Fat Embolism Syndrome: A Brief Review and Postmortem Diagnostic Approach

Lipoplasty, or liposuction, the surgical process of removing excess fat, is an elective procedure with rising frequency in the United States. Fat embolism syndrome is a clinical diagnosis and is defined as fat in the circulation with an identifiable clinical pattern of signs and symptoms (eg, hypoxemia, respiratory insufficiency, neurologic impairment, and petechial rash) that occur in the appropriate clinical context. Fat embolism syndrome following liposuction is a life-threatening complication, although its incidence is low. Currently, there is no specific therapy for fat embolism syndrome, so prevention, early detection, and supportive therapy are critical. Many cases of fat embolism syndrome are undiagnosed or misdiagnosed; however, postmortem examination can provide the means for appropriate diagnosis. Therefore, a pathologist must keep a keen eye, as microscopic fat emboli are difficult to appreciate with routine tissue processing and staining.

Pulmonary Fat Embolism and Coronary Amyloidosis

BACKGROUND Fat embolism syndrome is a well-known complication in orthopedic and trauma surgery, caused by a massive release of fat into the circulation that can lead to cardiopulmonary insufficiency and multiorgan failure. CASE REPORT We present the case of a 72-year-old man with osteoarthritis who underwent an elective right cementless total hip arthroplasty. Two hours after surgery, the patient lost consciousness and was found hypotensive and with reduced oxygen saturation, with a severe right heart dilatation at echocardiographic evaluation. Death occurred after cardiopulmonary resuscitation attempts. Post-mortem microscopic examination revealed that the final cause of death was pulmonary fat embolism associated with coronary amyloidosis and atherosclerosis. CONCLUSIONS This case called our attention on the sudden onset of fat embolism syndrome after arthroplasty and the insidious nature of amyloidosis infiltrative disease. The autopsy findings substantially aided understanding the immediate cause of death.

A Rare Fatal Complication of Llizarov Procedure

Ilizarov process is used for the management of multiple fractures, polytrauma conditions, cosmetic limb lengthening, and fracture malunion. Complications associated with the process are nerve palsy, joint contracture, premature or delayed osseous consolidation, a nonunion and permanent stiffness of the joint, pin tract infection, edema, and transient paresthesia, etc. In our case, there was a fatal complication. A 25-year-old African lady underwent the Ilizarov procedure for femur lengthening in a hospital in New Delhi, India. During her first distraction process, she suddenly collapsed at the hospital and could not be revived. At postmortem, a small hematoma was seen around the surgically fractured area. On histopathology of internal organs, fat globules were present in the vasculature of brain and lungs. Cause of death was opined as due to fat embolism. This is the first case reported of a fatal fat embolism following Ilizarov procedure for limb lengthening in a healthy adult.

Prevention of Fat Embolism in Fat Injection for Gluteal Augmentation, Anatomic Study in Fresh Cadavers

INTRODUCTION

Liposuction is a popular surgical procedure. As in any surgery, there are risks and complications, especially when combined with fat injection. Case reports of fat embolism have described a possible explanation as the puncture and tear of gluteal vessels during the procedure, especially when a deep injection is planned.

METHODS

A total of 10 dissections were performed in five fresh cadavers. Each buttocks was divided into four quadrants. We focused on the location where the gluteal vessels enter the muscle and the diameter of the vessels. Colorant at two different angles was injected (30° and 45°). We evaluated the relation of the colorant with the main vessels.

RESULTS

We found two perforators per quadrant. The thickness of the gluteal muscle was 2.84 ± 1.54 cm. The area under the muscle where the superior gluteal vessels traverse the muscle was located 6.4 ± 1.54 cm from the intergluteal crease and 5.8 ± 1.13 cm from the superior border of the muscle. The inferior gluteal vessels were located 8.3 ± 1.39 cm from the intergluteal crease and 10 ± 2.24 cm from the superior border of the muscle. When we compared the fat injected at a 30° angle, the colorant stayed in the muscle. Using a 45° angle, the colorant was in contact with the superior gluteal artery and the sciatic nerve. No puncture or tear was observed in the vessels or the nerve.

CONCLUSIONS

The location where the vessels come in contact with the muscle, which can be considered for fat injection, were located in quadrants 1 and 3. A 30° angle allows for an injection into the muscle without passing into deeper structures, unlike a 45° injection angle.

Imaging and histological findings of fat embolism in the vena cava

We describe an unusual case of a post-traumatic fat embolism in the vena cava and left femoral vein identified on CT before the onset of fat embolism syndrome. The patient was successfully treated by insertion of a vena cava filter and venous thrombectomy. This is the first occurrence of early identification of a large fat embolus allowing its extraction before occurrence of severe respiratory failure.

Inflammatory responses to neutral fat and fatty acids in multiple organs in a rat model of fat embolism syndrome

Fat embolism syndrome (FES) is a common complication of long bone fractures. FES is rare but with significant morbidity and occasional fatalities. Studies of animal models of FES are numerous; however, few studies compare inflammatory reactions in multiple organs. The present study investigated the effect of neutral fat and fatty acids, which cause changes in multiple organs and induce FES. Using rats we evaluated the ratio of lung-to-body weight and conducted histological analyses and quantitative analysis of inflammatory cytokine mRNAs in the lungs following intravenous administration of neutral fat or fatty acids. Neutral fat increased the ratio of lung-to-body weight, and neutral fat formed emboli in lung capillaries. The levels of interleukin-1 beta (IL-1β), IL-6 and tumor necrosis factor-alpha (TNF-α) in the lungs increased after injection of neutral fat and oleic acid. Analysis of the histologic changes revealed that the highest numbers of fat droplets, occluding the capillaries of the lungs, kidney, heart, and brain formed 12h after the injection of neutral fat and fat droplets gradually diminished 48h later. Fat droplets were not detected in any organs after the injection of oleic acid. IL-1β and TNF-α levels in the lungs were elevated 9-24h after the injection of neutral fat, although IL-6 levels peaked at 6h. After injection of oleic acid, peak levels of IL-1β, IL-6, and TNF-α were detected at 6h, and IL-6 again increased in all organs and plasma at 15h. Neutral fat, but not fatty acids, formed emboli in the capillaries of multiple organs. These findings suggest that neutral fat increased inflammatory cytokine levels by forming emboli in organ capillaries, particularly in the lungs, while oleic acid augmented inflammatory cytokine levels by stimulating endothelial cells of multiple organs.

Fat Embolism and Severe Natural Disease: Challenges for Certification

Detectable intravascular fat has been reported in up to 90% of patients with long bone fractures. However, the more clinically significant fat embolism syndrome (FES) is less common. Despite its common occurrence, determining the significance of fat embolism as a cause of death remains controversial; however, helpful objective criteria through a tiered approach have recently been proposed. Patients with coexisting natural disease and fat embolism present an additional challenge for interpretation. We present an illustrative 59-year-old woman with severe comorbidities who died 11 days following a femoral neck fracture and discuss how the use of special techniques to demonstrate embolic fat and published guidelines for diagnosis were helpful in death certification. The case also provides a beautiful morphologic illustration of the accumulation of lipid laden alveolar macrophages as intravascular fat is absorbed into the tissues over time. Such macrophages can also be clinically detected by bronchoalveolar lavage, which can provide some objective support for a clinically suspected diagnosis of fat embolism.

Cerebral fat embolism detection with susceptibility-weighted images in sickle cell disease

Cerebral fat embolism is a known but feared complication of sickle cell disease, which leads to significant morbidity. Although trauma-related fat embolism is more frequent and its diagnosis is straightforward, fat embolism secondary to bone infarcts after vaso-occlusive events can be unrecognized. Lack of criteria make the clinical diagnosis of sickle cell disease related fat embolism challenging. The neuroimaging findings are helpful to support the clinical diagnosis. Magnetic resonance imaging findings of fat embolism have been described including those seen on susceptibility-weighted imaging. Even though susceptibility-weighted imaging has been used for the diagnosis of cerebral fat embolism due to trauma, to the best of our knowledge its use has not been described in patients with sickle cell disease. We report an uncommon case of a 60-year-old woman with sickle cell disease who developed cerebral fat embolism and in which the findings on susceptibility-weighted imaging were characteristic and established the diagnosis.