A child taken for CECT chest was injected a contrast. Immediately after the injection she developed a swelling at the site of injection which gradually increased. She also complained of numbness and pain on passive extension of fingers. On examination radial pulse is feeble. What should be done next?

**Core Concept**
The child likely experienced a severe allergic reaction to the contrast agent used in the CECT chest scan, which led to a systemic response affecting multiple body systems. This reaction is commonly referred to as a Type I hypersensitivity reaction, also known as anaphylaxis.

**Why the Correct Answer is Right**
The symptoms described, such as swelling at the injection site, numbness, pain on passive extension of fingers, and a feeble radial pulse, are indicative of a severe systemic reaction. The numbness and pain on passive extension of fingers suggest involvement of the median nerve, which is a common manifestation of anaphylaxis affecting the upper limb. The feeble radial pulse indicates compromised vascular flow due to the reaction. The correct management of anaphylaxis involves administering epinephrine (adrenaline) immediately to alleviate symptoms and prevent further complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** Administering antihistamines alone is not sufficient to manage anaphylaxis, as these medications do not address the underlying pathophysiology of the reaction.
* **Option B:** Activating the emergency medical services (EMS) is a crucial step in managing anaphylaxis, but it is not the most immediate action required in this scenario.
* **Option C:** Administering oxygen may be helpful in managing respiratory symptoms associated with anaphylaxis, but it does not address the underlying cause of the reaction.

**Clinical Pearl / High-Yield Fact**
In cases of suspected anaphylaxis, it is essential to administer epinephrine (adrenaline) immediately, as it is the most effective medication in alleviating symptoms and preventing further complications.

**Correct Answer: C. Administer epinephrine (adrenaline) immediately.**

✓ Correct Answer: C. Immediate fasciotomy