A 68-year-old hypeensive man undergoes successful repair of a ruptured abdominal aoic aneurysm. He receives 9 L Ringer lactate solution and 4 units of whole blood during the operation. Two hours after transfer to the surgical intensive care unit, the following hemodynamic parameters are obtained: systemic blood pressure (BP) 90/60 mm Hg, pulse 110 beats per minute, central venous pressure (CVP) 7 mm Hg, pulmonary aery pressure 28/10 mm Hg, pulmonary capillary wedge pressure (PCWP) 8 mm Hg, cardiac output 1.9 L/min, systemic vascular resistance 1400 (dyne*s)/cm5 (normal is 900-1300), PaO2 140 mm Hg (FiO2 : 0.45), urine output 15 mL/h (specific gravity: 1.029), and hematocrit 35%. Given this data, which of the following is the most appropriate next step in management?

**Core Concept**
The patient is likely experiencing Distributive Shock, characterized by a state of low systemic vascular resistance, increased cardiac output, and a widened pulse pressure. This is often due to vasodilation and myocardial depression. Given the patient's history of abdominal aortic aneurysm repair and the use of large amounts of crystalloid and blood products, the most likely cause of distributive shock is anaphylactic reaction to the blood transfusion or vasodilation due to the high volume of crystalloid used.

**Why the Correct Answer is Right**
The patient's systemic vascular resistance is significantly decreased (1400 vs. normal 900-1300), indicating vasodilation. The cardiac output is increased, but the urine output is very low, suggesting inadequate perfusion of the kidneys despite an increased cardiac output. The central venous pressure and pulmonary capillary wedge pressure are low, which is consistent with a distributive type of shock. The hematocrit is low, but the patient has received 4 units of whole blood, which may not be sufficient to correct the anemia.

**Why Each Wrong Option is Incorrect**
**Option A:** Administering more blood products would not address the underlying cause of the distributive shock and may even worsen the situation by further diluting the blood and decreasing the hematocrit.

**Option B:** Increasing the FiO2 would not improve the patient's systemic blood pressure or urine output, and the PaO2 is already within a normal range.

**Option C:** Administering vasopressors such as norepinephrine would be appropriate if the patient had a cardiogenic or hypovolemic type of shock, but in this case, the patient has distributive shock due to vasodilation.

**Clinical Pearl / High-Yield Fact**
In a patient with distributive shock, it is essential to consider anaphylaxis as a potential cause, especially if the patient has received blood products or other medications recently. The use of vasopressors and inotropes may be necessary to support the patient's blood pressure and cardiac output.

**Correct Answer:** .

✓ Correct Answer: C. Administration of a fluid challenge to increase urine output