**Core Concept**
In anaphylactic shock, a severe, life-threatening allergic reaction, prompt administration of an effective medication is crucial to restore blood pressure and prevent further complications. The correct drug choice must rapidly increase cardiac output and vascular tone.

**Why the Correct Answer is Right**
Intravenous adrenaline (epinephrine) is the preferred treatment for anaphylactic shock due to its rapid onset of action and ability to increase cardiac output, vascular tone, and improve respiratory function. Adrenaline acts by stimulating beta-1 and beta-2 adrenergic receptors, which increases heart rate and contractility, dilates airway smooth muscles, and causes vasoconstriction in peripheral blood vessels. This leads to an increase in blood pressure and improved perfusion of vital organs.

**Why Each Wrong Option is Incorrect**
**Option A:** Subcutaneous adrenaline is not the preferred route of administration in anaphylactic shock, as it may not provide a rapid enough increase in blood pressure to prevent organ damage.
**Option C:** Steroids, such as hydrocortisone, are used to prevent late-phase reactions and are administered after initial stabilization with adrenaline.
**Option D:** Atropine is used to treat bradycardia and excessive salivation in anaphylaxis but is not the primary treatment for anaphylactic shock.

**Clinical Pearl / High-Yield Fact**
In anaphylactic shock, the initial dose of intravenous adrenaline is typically 0.5-1 mg every 5-15 minutes, followed by continuous infusion at a rate of 0.1-1 mcg/kg/min.

**✓ Correct Answer: B. Intravenous Adrenaline**