**Core Concept**
Succinylcholine is a depolarizing neuromuscular blocking agent that works by mimicking the action of acetylcholine at the neuromuscular junction. It binds to nicotinic receptors on skeletal muscle, causing initial muscle depolarization and contraction, followed by prolonged muscle relaxation due to desensitization of these receptors.

**Why the Correct Answer is Right**
The correct answer is related to the mechanism of action of succinylcholine. When succinylcholine binds to nicotinic receptors, it causes an initial increase in muscle depolarization, leading to a transient increase in muscle tone, also known as fasciculations. This is followed by prolonged muscle relaxation due to desensitization of nicotinic receptors. The transient increase in muscle tone is more pronounced in patients with burns, spinal cord injuries, or other conditions that lead to denervation of muscles.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the effect of succinylcholine. While succinylcholine can cause hyperkalemia, this is not the primary effect described in the question.

**Option B:** This option is incorrect because it is not a direct effect of succinylcholine. While succinylcholine can cause muscle relaxation, the question is asking about a specific effect of the drug.

**Option C:** This option is incorrect because it is not a common side effect of succinylcholine. While succinylcholine can cause bradycardia, this is not the primary effect described in the question.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that succinylcholine can cause hyperkalemia, especially in patients with burns, spinal cord injuries, or other conditions that lead to denervation of muscles. This is because denervated muscles have a higher concentration of nicotinic receptors, making them more sensitive to succinylcholine.

**Correct Answer: D. Fasciculations**