Hypernatremia is defined as a plasma sodium concentration more than
**Core Concept**
Hypernatremia is a condition characterized by an elevated plasma sodium concentration, which can lead to dehydration and increased intracranial pressure. This condition occurs when there is an excessive loss of water or an excessive intake of sodium, disrupting the balance of electrolytes in the body.
**Why the Correct Answer is Right**
The correct answer is 145 mmol/L. This is because hypernatremia is typically defined as a plasma sodium concentration greater than 145 mmol/L. When sodium levels exceed this threshold, it can lead to an imbalance of fluids within the cells, causing them to shrink and potentially leading to damage to the brain, kidneys, and other organs.
**Why Each Wrong Option is Incorrect**
* **Option A:** 135 mmol/L is within the normal range for plasma sodium concentration, and levels below this threshold would be considered hyponatremia.
* **Option B:** 155 mmol/L is above the threshold for hypernatremia, but it is not the defining value.
* **Option D:** This option is not provided, so it cannot be evaluated.
**Clinical Pearl / High-Yield Fact**
In clinical practice, it is essential to differentiate between hypernatremia and hyponatremia, as their treatment strategies are distinct. Hypernatremia often requires correction with hypotonic fluids, whereas hyponatremia may require hypertonic saline.
**Correct Answer:** 145 mmol/L