The fat embolism syndrome: a review

Pulmonary and Systemic Skeletal Muscle Embolism in a Beaked Whale with a Massive Trauma of Unknown Aetiology

Simple Summary

A severe trauma of unknown aetiology was suspected as the cause of death in an adult female Sowerby’s beaked whale found floating dead in the Canary Islands in December 2016. Many bruises in the skin and muscles (contusions) were observed in the chest wall and bone fractures, mainly located in the mandible and ribs. The broken rib bones also affected thoracic muscles, which escaped into the blood circulation once ruptured, reaching several organic locations, including the lungs, where they became trapped within the small lumen of pulmonary blood vessels, leading to a systemic and pulmonary skeletal muscle embolism. An embolism occurs when a piece of intravascular internal or foreign material obstructs the lumen of a blood vessel, starving tissues of blood and oxygen. An embolism necessarily needs cardiac function, indicating a survival time after trauma. This case report aimed to include the diagnosis of skeletal muscle embolism as a routine tool to determine if the traumatic event occurred before or after death. This is especially valuable when working with dead animals because no other evidence of traumatic injury may be recorded if carcasses are in advanced decay.

Abstract

An adult female Sowerby’s beaked whale was found floating dead in Hermigua (La Gomera, Canary Islands, Spain) on 7 December 2016. Severe traumas of unknown aetiology were attributed, and the gross and microscopic findings are consistent with catastrophic trauma as a cause of death. Rib fractures affected the intercostals, transverse thoracis skeletal muscles, and thoracic rete mirabile. Degenerated muscle fibres were extruded to flow into vascular and lymphatic vessels travelling to several anatomic locations into the thoracic cavity, including the lungs, where they occluded the small lumen of pulmonary microvasculature. A pulmonary and systemic skeletal muscle embolism was diagnosed, constituting the first description of this kind of embolism in an animal. The only previous description has been reported in a woman after peritoneal dialysis. Skeletal pulmonary embolism should be considered a valuable diagnostic for different types of trauma in vivo in wild animals. This is especially valuable when working with decomposed carcasses, as in those cases, it is not always feasible to assess other traumatic evidence.

Early, reliable, utilitarian predictive factors for fat embolism syndrome in polytrauma patients

BACKGROUND

Fat embolism is one of the apocalyptic pulmonary complications following high energy trauma situations. Since delay in diagnosis may have devastating consequences, early, easily accessible and relatively inexpensive investigations for risk stratification may prove useful, especially in developing nations.

MATERIALS AND METHODS

This prospective trial included a total of 67 young polytrauma patients, in whom the role of nine easily available, rapidly performable clinical or laboratory investigations (or observations noted at admission) in predicting the later occurrence of fat embolism syndrome were assessed. All the patients also underwent continuous monitoring of oxygen saturation with pulsoximetry.

RESULTS

The correlation between initial serum lactate (within 12 hours of injury) and hypoxia was statistically significant. There was a trend towards correlation with FES(by Gurd's criteria) (P=0.07), Sensitivity of 24-hour monitoring of oxygen saturation in predicting later pulmonary deterioration approached 100%.

CONCLUSIONS

The combination of three factors including polytrauma (with NISS >17), serum lactate >22 mmol/l at admission (within 12 hours of injury) fall in oxygen saturation (SaO2 below 90% in the initial 24 hours) predict the development of post-traumatic pulmonary complications, especially the fat embolism syndrome.

Forensic Lung Pathology

Sudden and unexpected natural deaths and nonnatural deaths may result from various pulmonary conditions. Additionally, several nonpulmonary conditions of forensic significance may be complicated by the development of respiratory lesions. Certain situations with pulmonary pathology are particularly likely to be critically scrutinized and may form the basis of allegations of medical negligence, other personal injury liability, or wrongful death.1

Prevention of fat embolism syndrome

Fat embolism syndrome is a condition of acute respiratory distress following long-bone trauma. This condition may involve not only the lungs but also a number of other body systems. The pathophysiology is not as yet clearly understood, however, intravasation of fat from long-bone fractures may play a role. Early recognition of the severity of injury both on clinical and biochemical grounds and early surgical stabilization of long bones may help to decrease its incidence. However, the best surgical technique with which to do this stabilization has not yet been clearly determined. Surgical and pharmacological techniques have been developed in an attempt to either decrease the intravasation of fat during long-bone stabilization or block the inflammatory cascade with varying degrees of efficacy. Ongoing research focuses on both the prevention and treatment of this condition.

The role of rehydration in the prevention of fat embolism syndrome

We encountered three cases of young sportsmen developing fat embolism syndrome (FES) after sustaining isolated tibial shaft fractures whilst playing football. All fractures were treated with intra-medullary nails and all three patients were kept nil-by-mouth pre-operatively without intravenous fluids. Correction of shock is often quoted as an important factor in the prevention of FES. However, animal studies have shown that dehydration, as opposed to hypovolaemia, may also be of great importance. We therefore examined the specific gravity of the urine of 20 patients with musculoskeletal injuries sustained during sport. The mean urinary specific gravity was significantly higher than that of a control group of 10 members of staff. We emphasise the importance of adequate pre-operative rehydration, especially if injuries were sustained during heavy exercise, as this may reduce the risk of developing FES.

Fat distribution and changes in the blood brain barrier in a rat model of cerebral arterial fat embolism

This study was designed to determine the distribution of fat which reaches the brain by the internal carotid artery, and the consequent alterations in the blood brain barrier, in a rat model of cerebral arterial fat embolism. The distribution of the blood flow in this model was determined by the injection of radiolabelled microspheres. Over 44% were trapped in the brain, 43% in the extracerebral tissues of the head and neck, and 7% in the lungs. Over 30% of radiolabelled triolein was present within the brain 30 min after injection, and 4% still remained after 17 days. Approximately 25% of the triolein which went to the brain moved through the cerebral vessels and left within the first 15 min. The majority of the triolein distributed to the ipsilateral cerebral hemisphere, with significantly less to the contralateral cerebral hemisphere, brain stem and cerebellum. The blood brain barrier opened, as measured by uptake of 99mTc, within the first 15 min and remained open for at least 3 days. A significant percentage of fat reaching the brain persists for days, and causes rapid and long-lasting damage to the blood brain barrier.

Fat embolism syndrome

Since it was initially described, fat embolism syndrome (FES) has remained one of the least clearly understood complications of trauma. This article is a review of the classic and current literature on FES with regard to its causes, pathophysiology, clinical presentation, diagnosis, and treatment. FES is associated with many traumatic and nontraumatic conditions, but is most commonly associated with fractures of long bones of the lower extremity. The pathophysiology is thought to be a cascade of events which can lead to adult respiratory distress syndrome (ARDS). Signs and symptoms of clinical FES usually begin within 24 to 48 hours after trauma. The classic triad involves pulmonary changes, cerebral dysfunction, and petechial rash. Clinical diagnosis is key because laboratory and roentgenographic diagnosis is not specific. Treatment consists of careful initial handling, early stabilization of fractures, careful volume replacement, analgesia, respiratory support, and perhaps steroids. The vast majority of patients today survive FES without sequelae.

Cerebral arterial fat embolism in the rabbit

This study was designed to measure the effects of cerebral arterial fat embolism on cerebral blood flow and function. Rabbits were injected via the left internal carotid artery with the neutral triglyceride triolein. Left cerebral blood flow was measured by laser Doppler flowmetry, and left sided brain function by electrocorticogram and cortical somatosensory evoked responses following electrical stimulation of the forepaw. Readings were taken for 2 h before injection to establish a baseline, and for 3 h after injection. Cerebral blood flow was significantly decreased at 45 min after the injection of the lipid, then progressively decreased further to approximately 50% of baseline after 2 h, at which level it remained for the last hour of the experiment. The electrocorticogram was rapidly, but transiently, suppressed. The evoked responses did not differ from baseline at each of the time points measured. Using 125I-triolein, 2.49% of the injected dose was measured in the brain 3 min after injection. The results show that in this rabbit model of cerebral arterial fat embolism only a small percentage of injected lipid passes into the brain, but this is sufficient to cause a reduction in cerebral blood flow over the following 2 h. The evoked responses never alter significantly from baseline values.

Cerebral fat embolism studied with MRI and SPECT

In a patient with fat embolism to the brain CT showed no abnormality. MRI performed after recovery from coma, when the patient had aphasia and quadriparesis, demonstrated multiple high signal abnormalities in the white matter on both T1- and T2-weighted images. HMPAO-SPECT showed left-sided hypoperfusion which resolved in parallel with clinical improvement 1 month later.

Fat embolism syndrome in a child with muscular dystrophy

Fat embolism syndrome is a relatively common complication of orthopedic trauma. Once thought to be rare in children, it probably occurs with a similar frequency as in adults, but is often subclinical. Clinically apparent fat embolism syndrome may exhibit neurologic, pulmonary, and cutaneous manifestations. It often resolves without sequelae if it is recognized promptly and supportive treatment is provided. We present a pediatric case of fat embolism syndrome and review the literature on its diagnosis and management in children.

Fat embolism syndrome and pulmonary microvascular cytology

Pulmonary microvascular cytology consists of analysis of capillary blood sampled while a Swan-Ganz catheter is in the wedge position. This technique has proved to be useful in the diagnosis of lymphangitic spread of carcinoma in the lungs and there are case reports of their use in amniotic fluid embolism. Its usefulness in diagnosing fat embolism syndrome has been shown only rarely. We report a new case in which pulmonary microvascular cytologic study allowed a definite diagnosis of fat embolism syndrome. We suggest obtaining routinely samples of capillary blood when a pulmonary catheter is in place and fat embolism is suspected on a clinical basis.

Fat embolism--a review

The subject of fat embolism is of recurring interest to those managing trauma. This article covers the topic of fat embolism in general, and presents a case of fulminant fat embolism syndrome which highlights the importance of clinical expertise, and whatever technological aids are available to diagnose and appropriately treat this relatively rare, but highly significant form of the syndrome. Fulminant fat embolism syndrome has a very high mortality and should be watched for in patients who have experienced major trauma.

Fatal fat embolism following total condylar knee arthroplasty

Although fatality from fat emboli syndrome following total knee arthroplasty has been reported, most cases occurred following the insertion of hinged prostheses and few are documented with detailed pathology. The authors present the case of a 75-year-old patient with long-standing rheumatoid arthritis who underwent a total condylar type total knee arthroplasty procedure using an intramedullary femoral alignment system and expired 6 hours following surgery. On autopsy he had multiple organ involvement with fat emboli. Especially with the present use of intramedullary alignment systems and the increasing numbers of one-stage bilateral total knee arthroplasty procedures the potential for this problem must be recognized so that early therapy can be instituted.

Computed tomography for diagnosis and assessment of cerebral fat embolism

A patient with cerebral fat embolism was followed by computed tomography (CT). For the first few days after injury, CT revealed no abnormality. About a week later, multiple low density areas appeared in the white matter of the frontal region. They disappeared within the subsequent 2 weeks while subdural effusions developed in the fronto-parieto-temporal regions. As neurologic recovery progressed, the subdural effusions gradually diminished and cerebral atrophy was seen.

Fat embolism syndrome. Changing prognosis

Patients with the fat embolism syndrome are reported to have a severe course, with mortality as high as 15 percent. Recent studies have attributed improved prognosis to one or another treatment modality. We reviewed the 54 patients with clinical evidence of the posttraumatic fat embolism syndrome documented at the Foothills Hospital from 1968 to 1977. The criteria for diagnosis were fever (54/54), hypoxemia (52/52), diffuse pulmonary infiltrates (49/54), changes in sensorium (41/54), and petechiae (39/54). Therapy included supplemental oxygen (54), assisted ventilation with positive end-expiratory pressure (5), and corticosteroids (7). There were no deaths. Patients who have the fat embolism syndrome without associated life-threatening disease have a relatively good prognosis with modern therapy, in contrast to reports in most of the published literature.

Acute hemiplegia of childhood

Acute hemiplegia of childhood is briefly reviewed with examples of various etiologies. The role of brain scans in diagnosing and following children with this syndrome is emphasized. Cerebral angiography and computer tomography represent complementary examinations in the evaluation of these patients.

The fat embolism syndrome, results of a therapeutic regime

Results of a therapeutic regime for the fat embolism syndrome are presented. The basis of this regime is to prevent hypoxia by use of oxygen and if necessary intermittent positive pressure ventilation. Prophylactic oxygen therapy in patients likely to develop the fat embolism syndorme is suggested.

The changing pattern of post-traumatic respiratory distress syndrome

During a one year period, 78 patients at the Denver General Hospital required mechanical ventilation following injury. Thirteen patients were judged to have Respiratory Distress Syndrome. Of these, 9 had classic early onset RDS but, with intravenous fluid restriction following resuscitation, diuretics and careful mechanical ventilation, all recovered. Six patients, all of whom were septic, developed late onset RDS 5 or more days after injury; 5 died. Disparity between early and late onset of RDS is emphasized; the one with good, the other with dismal prognosis. The current need is to improve treatment of late onset RDS, which frequently is associated with bacterial infection.