What is the most likely diagnosis for a postoperative patient who develops pain at the infusion site, fever, and chest tightness with a temperature of hyperthermia after starting a blood transfusion for postoperative bleeding?

Acute Hemolytic Transfusion Reaction

The most likely diagnosis is C. Hemolytic reaction, as the clinical triad of pain at the IV site, fever (38°C), and chest tightness occurring within minutes of starting blood transfusion represents the classic presentation of an acute hemolytic transfusion reaction—a medical emergency requiring immediate cessation of transfusion. 1

Why This is an Acute Hemolytic Transfusion Reaction

The combination of three key features occurring within minutes distinguishes this from other transfusion reactions:

• Pain at the infusion site is pathognomonic for acute hemolytic reaction and does not occur with febrile non-hemolytic reactions 1
• Chest tightness/dyspnea reflects the acute systemic inflammatory response from complement activation and cytokine release, not simple fever 1, 2
• Rapid onset (within minutes) indicates intravascular hemolysis from ABO incompatibility, the most common cause of acute hemolytic reactions 2, 3

The pathophysiology involves complete complement activation leading to intravascular hemolysis, formation of anaphylatoxins (C3a, C5a), cytokine release causing systemic inflammatory response, and activation of the kinin system—all occurring within minutes of incompatible blood exposure 2, 4.

Why the Other Options Are Incorrect

Febrile Non-Hemolytic Reaction (Option A)

• Presents with isolated fever and chills only, without pain at the IV site 1
• Lacks acute respiratory distress and hemodynamic instability 1
• Has an incidence of 1.1-2.15% and is generally benign 1
• Does not cause the characteristic IV site pain that this patient experienced 1

Bacterial Blood Contamination (Option B)

• While bacterial contamination can present with fever and hypotension, it typically occurs within 6 hours after platelet transfusion specifically 5
• The pain at the infusion site is not a characteristic feature of bacterial contamination 5
• Most commonly associated with platelet products rather than RBC transfusions for postoperative bleeding 5

Allergic Reaction (Option D)

• Manifests with urticaria, pruritus, and skin flushing rather than IV site pain 1
• Respiratory symptoms in allergic reactions are due to bronchospasm or laryngeal edema, not the acute dyspnea from systemic inflammation seen here 1
• Does not typically cause fever as a primary symptom 1

Critical Management Steps Required Immediately

Stop the transfusion immediately—this is the single most critical intervention that can prevent progression to severe morbidity or mortality 1, 6:

• Maintain IV access with normal saline for medication administration and fluid resuscitation 1
• Monitor vital signs every 5-15 minutes (heart rate, blood pressure, respiratory rate, oxygen saturation) 1
• Administer high-flow oxygen to address potential hypoxemia 6
• Maintain mean arterial pressure >65-70 mmHg with IV fluid resuscitation 1

Send urgent laboratory studies 1, 6:

• Return the blood component bag with administration set to transfusion laboratory 1
• Collect post-reaction blood samples for repeat crossmatch and direct antiglobulin test (Coombs test) 1
• Visual inspection of plasma for hemolysis 1
• Urine analysis for hemoglobinuria 1
• Complete blood count, PT, aPTT, fibrinogen 6

Prepare for potential complications 2, 4:

• Disseminated intravascular coagulation from activation of intrinsic clotting cascade 2
• Renal failure from disruption of microcirculation—maintain urine output >100 mL/hour with aggressive fluid resuscitation 5
• Hypotension and shock from kinin system activation 2, 4

Common Pitfalls to Avoid

• Never continue the transfusion despite thinking symptoms might be "just fever"—general anesthesia and critical illness can mask early signs of serious reactions 5
• Do not restart the transfusion before laboratory clearance, even if symptoms improve, as the reaction may worsen with continued exposure 5
• Double-check all documentation for administration errors, particularly patient identification and blood component compatibility, as most hemolytic reactions result from ABO-incompatible blood due to clerical errors 3

The risk of acute hemolytic transfusion reactions is approximately 1:70,000 per unit, with an estimated mortality risk of 1:1,250,000 RBC units transfused 1, 2. However, when they occur, they represent true medical emergencies requiring immediate recognition and intervention.