**Core Concept**
The management of a thyroid crisis involves addressing both the hyperthyroid state and its life-threatening complications, such as hyperpyrexia, cardiac instability, and shock. In this context, beta-blockers play a crucial role in mitigating the symptoms of excess thyroid hormones.

**Why the Correct Answer is Right**
Propranolol, a non-selective beta-blocker, is the correct choice because it helps to counteract the peripheral effects of excess thyroid hormones, including tachycardia, tremors, and hyperpyrexia. By blocking beta-1 and beta-2 adrenergic receptors, propranolol reduces the heart rate, cardiac output, and peripheral vascular resistance, thereby alleviating the cardiovascular instability associated with thyroid crisis.

**Why Each Wrong Option is Incorrect**
**Option A:** Metaraminol is a vasopressor agent that increases blood pressure by stimulating alpha-1 adrenergic receptors. In a thyroid crisis, the primary concern is not hypertension but rather hypotension and shock due to vasodilation and decreased cardiac output. Metaraminol would exacerbate these conditions.

**Option B:** Glucocorticoids, such as dexamethasone, are used to manage thyroid crisis by inhibiting the peripheral conversion of T4 to T3 and reducing the release of thyroid hormones from the thyroid gland. However, they are not the first line of treatment for the acute symptoms of thyroid crisis, such as hyperpyrexia and tachycardia.

**Option C:** Intravenous saline is essential for managing dehydration and shock in thyroid crisis but does not address the underlying cause of the symptoms. While IV fluids are crucial for replenishing lost volume and maintaining blood pressure, they do not correct the hypermetabolic state and cardiovascular instability associated with excess thyroid hormones.

**Clinical Pearl / High-Yield Fact**
In managing thyroid crisis, it is essential to remember that beta-blockers, such as propranolol, should be administered in conjunction with antithyroid medications, such as propylthiouracil or methimazole, to effectively manage the hyperthyroid state.

**Correct Answer Line**
✓ Correct Answer: D. Propranolol