A 55-year-old man is evaluated for acute onset of respiratory distress. He was admitted to the hospital after a highway traffic accident, which resulted in a left femur and wrist fracture. He was immediately taken to the operating room and underwent open reduction and internal fixation. The total blood loss was estimated at 1.1 liters and he was given 2 liters of intravenous normal saline and one unit of packed red blood cells intraoperatively. He was extubated and transferred to the postoperative recovery room. One hour following extubation, he developed acute respiratory distress requiring reintubation. His other medical problems include inferior wall myocardial infarction with right coronary artery stent placement 3 years ago, hypertension, hyperlipidemia, and type 2 diabetes mellitus. His home medications include aspirin, metoprolol, lisinopril, metformin, and rosuvastatin. His temperature is 38.1 C (100.6 F), blood pressure is 110/70 mm Hg, pulse is 110/min, respirations are 30/min, and oxygen saturation is 90% on 100% FiO₂ and 10 mm Hg of PEEP. He is drowsy from the sedation and intravenous hydromorphone infusion. There is no jugular venous distention or lower extremity edema. Pulmonary examination reveals diffuse crackles throughout the lungs. There are no heart murmurs. Skin examination reveals no rashes. Arterial blood gas shows a pH of 7.47, PaCO₂ of 32 mm Hg, and PaO₂ of 65 mm Hg. ECG shows sinus tachycardia. His preoperative chest x-ray was within normal limits. Repeat chest x-ray taken before reintubation is shown below. Which of the following is the most likely cause of his current condition?

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11ec193a_9715_0f2b_853d_693503d8677e_MD0002_00 This patient's presentation is consistent with transfusion-related acute lung injury (TRALI). Plasma is most frequently responsible for TRALI, but packed red blood cells, platelets, and other blood derivatives have also been implicated. Transfusion-related acute lung injury is likely due to anti-leukocyte antibodies from the donor's plasma reacting with antigens on the recipient's leukocytes to initiate an inflammatory response within the pulmonary microvasculature. Patients with TRALI usually present with sudden onset dyspnea, hypoxemia, and pulmonary infiltrates during or within 6 hours of any blood product transfusion (in the absence of circulatory overload). Chest x-ray shows bilateral patchy alveolar infiltrates consistent with ARDS. Importantly, TRALI diagnosis requires that patients not have preexisting ALI or other established ALI risk factors (e.g., septic shock, pneumonia, inhalation injury, etc.). Management of TRALI involves immediately stopping the transfusion, providing respiratory support (sometimes intubation), and vasopressors for hypotension. Clinical improvement occurs rapidly, even with severe hypoxemia, and most patients are extubated within 2 days. Patients with TRALI should receive no further plasma-containing blood products from the implicated donor. In addition, the blood bank should be notified and the donor investigated to prevent future incidents to other transfusion recipients from the donor. Patients recovering from TRALI are not at a significantly increased risk for recurrent episodes following transfusions from other donors. (Choice A) Anaphylactic transfusion reaction (more common in patients with IgA deficiency) presents with a rapid onset of dyspnea, stridor, wheezing, respiratory distress, and hypotension. However, anaphylactic transfusion reaction is not usually associated with abnormal chest x-ray findings, as seen in this patient. (Choice B) Aspiration pneumonia usually presents with cough, fever, purulent sputum, and dyspnea. However, symptoms usually evolve over a period of time. Aspiration pneumonitis (acid chemical pneumonitis) can cause acute distress and infiltrates but is rarely severe enough to cause florid ARDS. Infiltrates are typically localized to one or both lower lobes. (Choice C) The probability of fat embolism syndrome (FES) with a single long bone fracture is 1-3%; this increases to 33% with bilateral femur fractures. Fat embolism syndrome usually presents with the clinical triad of acute-onset neurologic abnormalities (e.g., confusion), hypoxemia, and petechial rash. FES typically manifests 24-72 hours after the initial insult and usually with a normal chest x-ray in the majority of patients. (Choice E) Transfusion-associated circulatory overload (TACO) usually presents with physical findings suggesting volume overload (e.g., elevated JVD, presence of an S3). Measurement of serum brain natriuretic peptide (BNP) or NT-Pro-BNP can also help in distinguishing TRALI from TACO. This patient received approximately 2.5 liters of fluid and has had 1.1 liters of blood loss, making volume overload unlikely. Educational objective: Transfusion-related acute lung injury (TRALI) should be considered in patients with acute onset dyspnea, hypoxemia, and pulmonary infiltrates that occur during or within 6 hours after transfusion of any plasma containing blood product. Treatment involves mainly supportive care, stopping the transfusion, and vasopressor support for hypotension. The blood bank should be notified and the blood donor investigated to prevent future incidents in other recipients. __________ References: Transfusion-related acute lung injury: Definition and review (http://www.ncbi.nlm.nih.gov/pubmed/15818095) Transfusion-related acute lung injury: a review. (http://www.ncbi.nlm.nih.gov/pubmed/15249468)

A 55-Year-Old Man Is Evaluated for Acute Onset of Respiratory