Question

Given below are two statements:
Statement I: Intravenous infusion of 100 ml normal saline to a healthy cow does not change its blood pH
Statement II: Intravenous infusion of 10 ml phosphate-buffered saline to a healthy cow does not change its blood pH
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

Blood Buffer Reserve: Massive blood volume and bicarbonate buffer reserve easily maintain constant blood pH ($7.35-7.45$) against minor isotonic volume infusions.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Physiological blood buffering capacity (bicarbonate, phosphate, plasma proteins, and hemoglobin) resists systemic pH shifts following isotonic saline infusions.

Step 2: Detailed Explanation:
In veterinary physiology and fluid therapy:
1. Statement I: In an adult healthy cow (circulating blood volume $\approx 35 - 45\text{ litres}$), infused with an isotonic, isosmotic fluid volume of only $100\text{ mL}$ of normal saline ($0.9\%\text{ NaCl}$), the tremendous buffer capacity of the bicarbonate-carbonic acid system immediately absorbs any minor ion shifts, maintaining systemic blood pH at $7.40 \pm 0.05$. Hence, Statement I is true.
2. Statement II: Phosphate-buffered saline (PBS, $\text{pH } 7.4$) is an isotonic, buffered solution that perfectly matches physiological plasma pH and tonicity. A $10\text{ mL}$ infusion has zero impact on blood pH. Hence, Statement II is true.

Step 3: Final Answer:
Therefore, Both Statement I and Statement II are true, corresponding to option (A).