**Question:** Concentration of sodium in Ringer's lactate is:

**Core Concept:** Ringer's lactate is a balanced electrolyte solution used for fluid replacement in clinical practice. It consists of various electrolytes, including sodium, potassium, calcium, and chloride.

**Why the Correct Answer is Right:** Ringer's lactate solution contains sodium chloride (NaCl) as the primary salt. The concentration of sodium in Ringer's lactate is approximately 140 mEq/L (milliequivalents per liter). This concentration is close to the normal serum sodium concentration (135-145 mEq/L), making it suitable for maintaining electrolyte balance during fluid replacement.

**Why Each Wrong Option is Incorrect:**

A. **145 mEq/L**: This is too high, which could lead to hypernatremia, a condition where the sodium level in the blood becomes too high. Hypernatremia can cause dehydration, brain swelling, and potentially life-threatening complications.

B. **100 mEq/L**: This is too low, which could lead to hyponatremia, a condition where the sodium level in the blood becomes too low. Hyponatremia can cause neurological symptoms, seizures, and even coma.

C. **Ringer's lactate is a balanced salt solution**: Although Ringer's lactate contains balanced salt concentrations, it does not specifically mention the sodium concentration.

D. **Lactated Ringer's solution**: This is a similar solution to Ringer's lactate but with a slightly higher sodium concentration (145 mEq/L), which is also too high and can lead to hypernatremia.

**Clinical Pearl:** Ringer's lactate solution is commonly used in clinical practice for fluid replacement in various medical conditions like dehydration, burns, and surgical procedures. When selecting an electrolyte solution, it is essential to consider not only the sodium concentration but also the overall balance of electrolytes to prevent complications associated with electrolyte imbalances.

**Correct Answer:** 140 mEq/L (milliequivalents per liter)

Ringer's lactate solution is a balanced salt solution, meaning it contains an equal amount of potassium (K+) and calcium (Ca2+) and a slightly lower chloride (Cl-) concentration compared to serum levels. Its primary purpose is to maintain electrolyte balance during fluid replacement therapy.