A 26-year-old woman is brought to the emergency department after a motor vehicle accident. She was driving on the highway when she was struck by a van. At the hospital she was conscious but was bleeding heavily from an open wound in her left leg. Pulse is 120/min and blood pressure is 96/68 mm Hg. She receives 3 L of intravenous saline and her pulse slowed to 80/min and blood pressure elevated to 116/70 mm Hg. The next morning she is found to have a hemoglobin of 6.2 g/dL. Her team decides to transfuse 1 unit of packed RBCs. Twenty minutes into the transfusion she develops a diffuse urticarial rash, wheezing, fever, and hypotension. The transfusion is immediately stopped and intramuscular epinephrine is administered. Which of the following scenarios is most consistent with this patient's reaction to the blood transfusion?

A patient history of frequent sinopulmonary infections

A patient history of cardiovascular disease

Unsanitary blood product storage practices in the hospital

Facial twitching when the patient's cheek is tapped

Prior transfusion reactions caused by the same donor

A 35-year-old patient is brought into the emergency department post motor vehicle crash. Stabilization of the patient in the trauma bay requires endotracheal intubation. The patient has a laceration on the femoral artery from shrapnel and seems to have lost large quantities of blood. The patient is transfused with 13 units of packed red blood cells. His vitals are T 96.5, HR 150, BP 90/40. Even with the direct pressure on the femoral artery, the patient continues to bleed. Results of labs drawn within the last hour are pending. Which of the following is most likely to stop the bleeding in this patient?

Fresh frozen plasma and platelets

A 34-year-old primigravida was brought to an obstetric clinic with a chief complaint of painless vaginal bleeding. She was diagnosed with placenta praevia and transfused with 2 units of whole blood. Five hours after the transfusion, she developed a fever and chills. How could the current situation be prevented?

Transfusing leukocyte reduced blood products

Administering prophylactic epinephrine

ABO grouping and Rh typing before transfusion

Performing Coombs test before transfusion

Administering prophylactic immunoglobulins

A 43-year-old man presents to the emergency department following a work-related accident in which both arms were amputated. The patient lost a substantial amount of blood prior to arrival, and his bleeding is difficult to control due to arterial damage and wound contamination with debris. His complete blood count (CBC) is significant for a hemoglobin (Hgb) level of 5.3 g/dL. The trauma surgery resident initiates the massive transfusion protocol and orders whole blood, O negative, which she explains is the universal donor. The patient receives 6 units of O negative blood prior to admission. He subsequently develops fever, chills, hematuria, and pulmonary edema. Several hours later, the patient goes into hemodynamic shock requiring the emergent administration of vasopressors. Of the following options, which hypersensitivity reaction occurred?

Type 2 hypersensitivity reaction

Type 1 hypersensitivity reaction

Combined type 1 and type 4 hypersensitivity reaction

Type 3 hypersensitivity reaction

Type 4 hypersensitivity reaction

A 16-year-old boy is brought to the emergency department following a car accident in which he suffered multiple injuries. He is accompanied by his mother. She reports that his medical history is notable only for recurrent sinusitis and otitis as a child. He lost a significant amount of blood from the accident, and he is transfused two units of O-negative blood on arrival at the emergency department. Shortly thereafter, he complains of itching and increasing shortness of breath. He develops stridor. Which of the following could have prevented this reaction?

Administering washed blood products

Administering IVIG with transfusion

Pre-transfusion diphenhydramine

Administering type-specific blood

A 36-year-old man presents with massive hematemesis. Past medical history is significant for a gastric ulcer. He has a pulse of 115/min, respiratory rate of 20/min, temperature of 36°C (96.8°F), and blood pressure of 90/59 mm Hg. The patient receives a transfusion of 2 units of packed red blood cells. Around 5–10 minutes after the transfusion, he starts having chills, pain in the lumbar region, and oliguria. His vital signs change to pulse of 118/min, respiratory rate of 19/min, temperature of 38°C (100.4°F), and blood pressure of 60/40 mm Hg. Which of the following is the most likely cause of this patient’s condition?

Acute hemolytic transfusion reaction

Transfusion-related acute lung injury

Anaphylactic transfusion reaction

A 22-year-old woman in the intensive care unit has had persistent oozing from the margins of wounds for 2 hours that is not controlled by pressure bandages. She was admitted to the hospital 13 hours ago following a high-speed motor vehicle collision. Initial focused assessment with sonography for trauma was negative. An x-ray survey showed opacification of the right lung field and fractures of multiple ribs, the tibia, fibula, calcaneus, right acetabulum, and bilateral pubic rami. Laboratory studies showed a hemoglobin concentration of 14.8 g/dL, leukocyte count of 10,300/mm3, platelet count of 175,000/mm3, and blood glucose concentration of 77 mg/dL. Infusion of 0.9% saline was begun. Multiple lacerations on the forehead and extremities were sutured, and fractures were stabilized. Repeat laboratory studies now show a hemoglobin concentration of 12.4 g/dL, platelet count of 102,000/mm3, prothrombin time of 26 seconds (INR=1.8), and activated partial thromboplastin time of 63 seconds. Which of the following is the next best step in management?

Transfuse packed RBC, fresh frozen plasma, and platelet concentrate in a 1:1:1 ratio

Transfuse packed RBC and fresh frozen plasma in a 1:1 ratio

Transfuse fresh frozen plasma and platelet concentrate in a 1:1 ratio

Transfuse whole blood and administer vitamin K

A 72-year-old man with coronary artery disease comes to the emergency department because of chest pain and shortness of breath for the past 3 hours. Troponin levels are elevated and an ECG shows ST-elevations in the precordial leads. Revascularization with percutaneous coronary intervention is performed, and a stent is successfully placed in the left anterior descending artery. Two days later, he complains of worsening shortness of breath. Pulse oximetry on 3L of nasal cannula shows an oxygen saturation of 89%. An x-ray of the chest shows distended pulmonary veins, small horizontal lines at the lung bases, and blunting of the costophrenic angles bilaterally. Which of the following findings would be most likely on a ventilation-perfusion scan of this patient?

Normal perfusion with bilateral ventilation defects

Matched ventilation and perfusion bilaterally

Normal ventilation with multiple, bilateral perfusion defects

Normal perfusion with decreased ventilation at the right base

Increased apical ventilation with normal perfusion bilaterally

A 25-year-old man comes to the emergency department because of a 1-week-history of progressively worsening dyspnea and intermittent chest pain that increases on inspiration. He had an upper respiratory tract infection 2 weeks ago. His pulse is 115/min and blood pressure is 100/65 mm Hg. Examination shows inspiratory crackles bilaterally. His serum troponin I is 0.21 ng/mL (N < 0.1). An x-ray of the chest shows an enlarged cardiac silhouette and prominent vascular markings in both lung fields; costophrenic angles are blunted. A rhythm strip shows inverted T waves. Which of the following additional findings is most likely in this patient's condition?

Elevated brain natriuretic peptide

Opening snap with low-pitched diastolic rumble

A 65-year-old man presents to the emergency department due to an episode of lightheadedness. The patient was working at his garage workbench when he felt like he was going to faint. His temperature is 98.8°F (37.1°C), blood pressure is 125/62 mmHg, pulse is 117/min, respirations are 14/min, and oxygen saturation is 98% on room air. Laboratory values are ordered as seen below. Hemoglobin: 7 g/dL Hematocrit: 22% Leukocyte count: 6,500/mm^3 with normal differential Platelet count: 197,000/mm^3 The patient is started on blood products and a CT scan is ordered. Several minutes later, his temperature is 99.5°F (37.5°C), blood pressure is 87/48 mmHg, and pulse is 180/min. The patient's breathing is labored. Which of the following is also likely to be true?

Acute hemolytic transfusion reaction

Transfusion-related acute lung injury (TRALI)

Bacterial contamination of blood products

Transfusion medicine for USMLE Step 1: High-Yield Internal Medicine Lessons

Blood Products - The Component Toolkit

Packed Red Blood Cells (PRBCs): For symptomatic anemia or acute hemorrhage. 1 unit ↑ Hb by 1 g/dL & Hct by 3%.
Platelets: For severe thrombocytopenia (<10,000/μL) or bleeding with counts <50,000/μL. 1 apheresis pack ↑ count by 30-60k.
Fresh Frozen Plasma (FFP): Replaces all clotting factors. Use for coagulopathy (e.g., liver disease, warfarin reversal with bleeding). INR > 1.7.
Cryoprecipitate: Concentrated fibrinogen, Factor VIII, XIII, vWF. Use for hypofibrinogenemia (<100 mg/dL).

Blood Component Separation: Centrifugation vs. Passive

⭐ Leukoreduction: Filtering donated blood to remove WBCs. Reduces risk of febrile non-hemolytic transfusion reactions, CMV transmission, and HLA alloimmunization.

Transfusion Reactions - When Good Blood Goes Bad

Immediate Management:

Acute Reactions (< 24 hrs):
- Allergic/Urticarial: IgE-mediated. Urticaria, pruritus. Tx: Antihistamines.
- Febrile Non-Hemolytic (FNHTR): Cytokine-mediated. Fever, chills. Tx: Antipyretics.
- Acute Hemolytic (AHTR): ⚠️ ABO incompatibility. Fever, flank pain, hemoglobinuria. Positive Coombs test.
- TRALI: Donor anti-leukocyte Abs. Respiratory distress, non-cardiogenic pulmonary edema.
- TACO: Volume overload. Dyspnea, hypertension, cardiogenic pulmonary edema.
Delayed Reactions (> 24 hrs):
- Delayed Hemolytic: Anamnestic response (e.g., Kidd, Kell antigens). Mild jaundice, ↓Hct.
- TA-GVHD: Donor T-cells attack host. Pancytopenia, rash, diarrhea. Prevent with irradiated blood.

⭐ TRALI is the leading cause of transfusion-related mortality. It presents as acute hypoxemic respiratory failure with bilateral pulmonary infiltrates on CXR, in the absence of circulatory overload.

Indications & Special Products - The Right Stuff

Packed Red Blood Cells (PRBCs)
- Indication: Symptomatic anemia, acute hemorrhage.
- Threshold: Hb < 7 g/dL (or < 8 g/dL in cardiac disease/sepsis).
- Effect: 1 unit ↑ Hb by ~1 g/dL.
Platelets
- Indication: Bleeding with thrombocytopenia (<50,000/μL) or dysfunction.
- Prophylaxis: < 10,000/μL.
Fresh Frozen Plasma (FFP)
- Indication: Coagulopathy (e.g., liver disease, DIC, urgent warfarin reversal). Contains all clotting factors.
Cryoprecipitate
- Indication: Hypofibrinogenemia (<100-150 mg/dL), vWD.
- Contains: Fibrinogen, Factor VIII, Factor XIII, vWF.

Blood Components, Separation, and Transfusion Products

Special Preparations
- Leukoreduced: ↓ Febrile non-hemolytic reactions, CMV risk.
- Irradiated: Prevents TA-GVHD in immunocompromised (e.g., transplant, hematologic malignancy).
- Washed: Removes plasma proteins; for severe allergic reactions (e.g., IgA deficiency).

⭐ For urgent warfarin reversal, Prothrombin Complex Concentrate (PCC) is preferred over FFP due to faster action and lower volume.

High‑Yield Points - ⚡ Biggest Takeaways

Febrile non-hemolytic is the most common transfusion reaction, caused by pre-formed cytokines.

Acute hemolytic reactions from ABO incompatibility are life-threatening, causing intravascular hemolysis and DIC.

TRALI is due to donor anti-leukocyte antibodies, leading to acute respiratory distress.

TACO is volume overload; differentiate from TRALI with an elevated BNP.

Suspect anaphylaxis in IgA-deficient patients receiving blood products.

Washed RBCs are used for patients with a history of severe allergic reactions.

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