Patient undergoing surgery was given a muscle relaxant. It produced marked fall in B.P. and increase in airway resistance which were reversed with diphenhydramine. The muscle relaxant was most probably :
**Core Concept**
The question revolves around the pharmacological properties of muscle relaxants used in surgery, specifically their effects on blood pressure and airway resistance. **Muscle relaxants** can have various side effects, including histamine release, which can lead to hypotension and increased airway resistance.
**Why the Correct Answer is Right**
The correct answer is likely related to a muscle relaxant that causes histamine release, leading to a fall in blood pressure and an increase in airway resistance. This is because **diphenhydramine**, an antihistamine, was used to reverse these effects. The muscle relaxant **tubocurarine** is known to cause histamine release, leading to these side effects.
**Why Each Wrong Option is Incorrect**
**Option A:** May not be correct as it doesn't specify a muscle relaxant known for histamine release.
**Option B:** Similarly, may not be the correct answer if it doesn't match the profile of a histamine-releasing muscle relaxant.
**Option D:** Is incorrect as it doesn't align with the clinical scenario described, particularly the reversal with diphenhydramine.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember that certain muscle relaxants can cause histamine release, leading to significant hypotension and bronchospasm, which can be life-threatening. Recognizing the signs and having antihistamines like **diphenhydramine** available is key.
**Correct Answer:** C. Tubocurarine.