The Journal of Maharashtra Orthopaedic Association September / December - 2006 Fat Embolism Syndrome And Crush Syndrome Dr. Shivaprasad D. Khot M.S. Orth., D. Orth. ( Mumbai) Dr. Rahul S. Khot M.B.B.S., D. Orth., D.N.B. v Introduction v v Causes v Fat Embolism syndrome is a major cause of FES occurs most commonly as an early morbidity and mortality after multiple long bone complication of fractures of the pelvis and long fractures and is an important cause of ARDS. bones. FES is also reported in other entities: FES may be defined as, “a complex alteration l As a complication of reaming of medullary of homeostasis that occurs as an infrequent canals of long bones complication of fractures of long bones and pelvis l As a complication of reaming and cementation and manifests clinically as acute respiratory during joint replacement ? Massive soft tissue insufficiency”. injury ? Severe burns FES develops when fat emboli become l Liposuction impacted in pulmonary microcirculation and other l Chronic osteomyelitis microvascular beds such as the brain and is l Metabolic disorders characterized by respiratory failure, cerebral l dysfunction and petechiae. In-patients with pre Neoplasms existing pulmonary disease the addition of FES can l Renal transplant be life threatening. FES is an a important cause of l Bone infarcts in hemoglobinopathoies acute respiratory distress syndrome. With prompt l Collagen disease recognition, the treatment of the fat embolism l syndrome has become more specific and less empiric, Diabetes resulting in decrease morbidity and mortality. In l Severe infection recent years prevention of fat embolism syndrome l Inhalation anesthesia by early fracture fixation and patient mobilization l Blood transfusion has become the focus of a wave of clinical v Historical Aspects v investigation. Acute respiratory insufficiency after skeletal FES is a well-known entity as a complication of long bone fractures from one and half centuries. trauma has multiple causes : Zenker in 1861 described fat droplets in the l Fat embolism lung capillaries of a rail-road worker with fatal l Aspiration of gastric contents thoraco-abdominal crush injury. l Pulmonary edema Wagner in 1865 described the pathologic l Airway obstruction features of fat embolism. l Pneumonia Von Bergmann in 1873 was the first to establish FES in a patient with femoral fractures by l Pulmonary contusions postmortem demonstration of a large amount of l Shock lung pulmonary fat. Vol. 5 / 6 - Year 2 - Sept. / Dec. 2006 209 Czerny in 1875 described the symptoms of others proposed a biochemical theory which FES and the importance of fundoscopic examination incriminates free fatty acids. in its diagnosis. According to them, local hydrolysis of Fenger and Salisbury in 1879 made the first triglycerides and neutral fat emboli by pneumocyte clinical diagnosis of FES in a patient with femoral lipase results in increased free fatty acids. fractures and confirmed it by demonstrating massive v Free fatty acids have been shown to be toxic fat emboli in the lung at autopsy. to lung parenchyma and lead to v Incidence v l Disruption of alveolar capillary membrane The exact incidence of FES is not known. The l Decreased surfactant production clinical signs and symptoms develop in 0.5% to 2% l Interstitial hemorrhage and of patients with long bone fractures and in 10% of patients with multiple fractures. The risk of FES l Pulmonary edema resulting in pulmonary increases with the increased incidence of multiple dysfunction. fractures in major automobile accidents. FES is rare Thus, the latent period before clinical in children probably because of low fat content in manifestations appear may be explained by the time their marrow. needed for lipoprotein lipase to convert neutral fat v Pathogenesis And Pathophysiology v to toxic free fatty acids. v Clinical Presentation v This is a subject of conjecture and controversy. The source of embolic fat is thought by most to be Onset of symptoms is usually within 12 to 72 the bone marrow. Bone marrow elements have been hours but may manifest as early as 6 hours and as demonstrated in lung sections, indicating that late as 10 days. mechanical fat embolization does occur. Two Arterial hypoxemia is the hallmark of FES and theories have been offered for the pathogenesis of the clinical manifestations are a result of reduced FES: blood flow to the lungs and brain (a) Mechanical theory : This classic theory Early symptoms are : postulates that triglyceride particles from injured fat l Shortness of breath marrow enter the circulation and obstruct the pulmonary micro vessels. Fat globules vary in size l Restlessness from 2 to 200 microns and most get lodged in vessels l Confusion less than 75 microns in diameter. The classic triad of FES involves : v The blockage of pulmonary capillaries l Pulmonary dysfunction results in : l Cerebral dysfunction and l Venoarterial shunting l Cutaneous changes. l Hypoxemia and Pulmonary Dysfunction l Alveolar hypoperfusion leading to pulmonary dysfunction. Features of pulmonary insufficiency are the earliest signs of FES and include : (B) Biochemical Theory : As FES has also l been documented in non traumatic disorders, the Tachypnoea with respiratory rate more than mechanical theory cannot adequately explain the 30 per minute phenomenon. Alternative or additional mechanisms l Dyspnoea have therefore been suggested. Peltier, Barie and l Cyanosis Vol. 5 / 6 - Year 2 - Sept. / Dec. 2006 210 l Rales and rhonchi Sevitt classified FES into 3 distinguishable clinical l Respiratory failure and ARDS presentations : l l Occasionally hemoptysis and pulmonary Sub clinical FES edema l Non fulminant FES l Cerebral Dysfunction Fulminant FES Features include : Sub clinical FES l Restlessness l Probably occurs in almost all long bone fractures of the lower extremity and fractures l Confusion and disorientation of the pelvis l Irritability and delirium l Characterised by decreased PaO2, decreased l Stupor and coma Hb% and decreased platelets. No clinical l Convulsions signs and symptoms of respiratory insufficiency. l Diffuse neurological deficit. The neurological features in FES appear to Non-fulminant FES change periodically and may sometimes progress l Clinical signs and symptoms are clearly very rapidly. evident. l Cutaneous Changes Respiratory insufficiency, cerebral symptoms and petechiae appear classically Are characterized by : l Typical radiological and haematological l Petechiael rashes located in the upper anterior changes can be detected chest, axilla, neck, oral mucous membrane and conjunctiva. Fulminant FES l Appear on the second to third day l Rarer form and appears within hours of injury l May occur periodically with accompanying l Characterised by severe respiratory failure and attacks of coma altered mental status and convulsions. l Resolve within 7 days FES should be Strongly Suspected if the Patient The distribution of petechiae is theorized to has the related fat particles floating in the aortic arch l Unexplained Dyspnoea and Tachycardia and embolising to non-depended skin areas via l Unexplained confusion and cerebral subclavian and carotid arteries. dysfunction The other signs of FES include : l Petechiae in the upper half of the body. l Pyrexia : Fracture fever / haematoma fever Often the signs and symptoms may be masked l Tachycardia: pulse rate more than 140 per by shock, coma, head injury and anesthetic drugs. minute v Diagnosis v l Retinal changes which include edema, The diagnosis of FES is essentially by clinical hemorrhage or intravascular fat globules as features and there are no pathognomonic tests for seen on fundoscopy confirmation. However certain laboratory and x-ray l Renal changes like lipuria features aid in the diagnosis of FES. l Hepatic changes like jaundice Laboratory Investigations l Urinary incontinence l Sustained reduction in PaO2 levels (partial Vol. 5 / 6 - Year 2 - Sept. / Dec. 2006 211 pressure of oxygen in arterial blood) below w Cerebral dysfunction w Tachycardia 60 mm of Hg as detected by arterial blood gas w Petechiael rash w Retinal changes analysis indicates FES. Serial determination of PaO2 levels is necessary. Clinical features w Jaundice appear only when the levels fall below 65 mm w Renal changes of Hg. l Thrombocytopenia; platelets below 150000 Laboratory Features (at least one) cell per cubic millimeter is commonly seen. w Fat macroglobulinemia l Detection of fat globules in urine, sputum, w Anemia CSF and blood; usually difficult to do. Gurd w Thrombocytopenia suggested detection of pathological fat in filtered venous blood. Cryostat frozen section w High ESR of clotted blood may reveal fat globules. They proposed that if any one major and four l Biopsy of petechiael skin lesions may reveal minor features are present after a latent period after presence of fat. injury, then a diagnosis of FES could be made. l Elevated serum lipase and free fatty acid levels Schonfeld et al proposed a quantitative means l Broncho alveolar lavage and detection of fat of diagnosing FES droplets within cells recovered by lavage may v Schonfelds Fat Embolism Index v aid in rapid diagnosis of FES. v ECG v Symptoms Score Show only non-specific changes like T wave w Petechiae 5 inversion, prominent S waves and occasional w Diffuse alveolar infiltrates 4 arrhythmias. w Hypoxemia (PaO2 less than 9.3 kPa) 3 X-ray w Confusion 1 Chest X-ray reveals a diffuse fluffy bilateral w Fever (more than 38’C) 1 infiltrate classically called “snow storm” appearance. w Tachycardia 1 This may progress to widespread airspace (more than 120 beats per min) consolidation caused by alveolar hemorrhage and edema. w Tachypnea (more than 30 per min) 1 A differential diagnosis of cardiogenic edema A cumulative score greater than 5 is necessary and traumatic lung contusion must be kept in mind. for a positive diagnosis of FES. Since there are no definitive and pathogn- v Differential Diagnosis v omonic features of FES, several authors have Since FES involves respiratory insufficiency suggested some aids in diagnosing FES.