**Core Concept**
The management of cardiac arrest involves a series of steps to restore spontaneous circulation and ensure adequate oxygenation and ventilation. After successful resuscitation, the next step is to establish a secure airway, ensure adequate ventilation, and maintain a stable circulation.

**Why the Correct Answer is Right**
The American Heart Association (AHA) guidelines recommend that, after achieving stable spontaneous circulation, the focus should shift to maintaining oxygenation and ventilation. This involves ensuring a secure airway, often with endotracheal intubation, and providing adequate mechanical ventilation. The goal is to maintain an optimal partial pressure of arterial carbon dioxide (PaCO2) and oxygen saturation (SpO2) to prevent further cardiac decompensation. Secure airway management is critical to prevent aspiration and ensure effective ventilation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, while cardiac output monitoring is essential, it is not the next step after achieving stable spontaneous circulation. Cardiac output monitoring can be done simultaneously with airway management and ventilation.
**Option B:** This option is incorrect because, although chest X-ray is crucial for assessing post-cardiac arrest complications, it is not the immediate next step after achieving stable spontaneous circulation. Chest X-ray can be ordered after the patient is stabilized.
**Option C:** This option is incorrect because, although vasopressor therapy may be necessary to maintain blood pressure, it is not the next step after achieving stable spontaneous circulation. Vasopressor therapy should be initiated based on the patient's hemodynamic status and not as a routine step.

**Clinical Pearl / High-Yield Fact**
In the post-cardiac arrest period, maintaining a PaCO2 between 35-45 mmHg and an SpO2 above 94% is crucial to prevent further cardiac decompensation.

**Correct Answer:** B. Establish a secure airway and ensure adequate ventilation.