If a healthy man drinks one litre of water on occasion A and one litre of 0.9% saline on occasion B, what shall we expect in two hours?

Options

A. `{:(" Occasion A",," Occassion B"),(underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) "in")("Concentration"),,underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) " in ")("Concentration")),(+++" " +,, " "+ " "+++):}`
B. `{:(" Occasion A",," Occassion B"),(underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) "in")("Concentration"),,underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) " in ")("Concentration")),(+++" " +,, " "+ " "+):}`
C. `{:(" Occasion A",," Occassion B"),(underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) "in")("Concentration"),,underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) " in ")("Concentration")),(++" " ++,, " "++ " "+++):}`
D. `{:(" Occasion A",," Occassion B"),(underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) "in")("Concentration"),,underset("of urine")("Volume")" " underset("urine")underset("of " Na^(+) " in ")("Concentration")),(+++" " ++,, ""+++ " "+++):}`

Explanation

To solve the question regarding the effects of drinking one liter of water versus one liter of 0.9% saline on urine output and sodium concentration in a healthy man over two hours, we can break it down into the following steps:

### Step 1: Understand the Composition of the Fluids
- **Occasion A**: The man drinks 1 liter of pure water.
- **Occasion B**: The man drinks 1 liter of 0.9% saline, which contains sodium chloride (NaCl) dissolved in water.

### Step 2: Analyze the Effects of Drinking Pure Water
- When a healthy person consumes pure water, it dilutes the blood plasma.
- This dilution leads to a decrease in plasma osmolarity, which triggers the kidneys to excrete more urine to restore balance.
- Therefore, we can expect a **normal volume of urine** to be produced, and the concentration of sodium (Na+) in the urine will be relatively low since the body is trying to excrete excess water.

### Step 3: Analyze the Effects of Drinking 0.9% Saline
- Drinking 0.9% saline increases the sodium concentration in the blood.
- The body responds to this increase in osmolarity by retaining water to dilute the sodium concentration back to normal levels.
- As a result, the volume of urine produced will be **less than normal** because the kidneys will reabsorb more water to maintain homeostasis.
- The concentration of sodium in the urine will also be **lower** since the kidneys are trying to conserve sodium due to its increased presence in the bloodstream.

### Step 4: Summarize the Expected Outcomes
- **For Occasion A (1 liter of water)**:
- Volume of urine: **Increased** (more urine output)
- Sodium concentration in urine: **Low**

- **For Occasion B (1 liter of 0.9% saline)**:
- Volume of urine: **Decreased** (less urine output)
- Sodium concentration in urine: **Low** (but lower than in occasion A due to conservation)

### Conclusion
In conclusion, after two hours:
- For the water intake (occasion A), expect increased urine volume and low sodium concentration.
- For the saline intake (occasion B), expect decreased urine volume and low sodium concentration.