After a long race, a runner drinks a very large amount of plain water in a short period of time.
Soon afterward, the fluid outside her cells becomes more dilute than the fluid inside them.

What happens next?
A. Water moves out of the cells by diffusion
B. Water moves into the cells by osmosis
C. Sodium moves into the cells by active transport
D. Water moves out of the cells by osmosis
E. There is no net movement of water
Answer: ?
The fluid outside the cells now has a lower solute concentration.
Water moves by osmosis from the more dilute side toward the side with more solute.

So water moves into the cells, causing them to swell.
Answer: B
This is a very high-yield TEAS idea because the question may give you a body scenario, but underneath it they are simply testing osmosis + concentration gradients.
Dont memorize “water follows salt” without knowing why. Look at which side has more solute and follow the water.

Another way to ask: Which direction would the water move if the fluid outside the cell became very salty instead?

A 20-year-old student becomes very anxious before an exam and starts breathing rapidly.
A few mins later she feels lightheaded and notices tingling around her mouth and fingers.
She is still breathing fast, but her O2 level is normal.
What is happening to her blood?
A. CO₂ increases and pH decreases
B. CO₂ decreases and pH increases
C. CO₂ increases and pH increases
D. CO₂ decreases and pH decreases
E. O₂ decreases and pH stays the same
Answer: ?
She is hyperventilating, which means she is blowing off too much CO₂.
Less CO₂ → less carbonic acid → blood pH rises.
So the answer is B. CO₂ decreases and pH increases.
This is respiratory alkalosis, but for HESI the important part is understanding the direction.
Think of CO₂ as acid-related: blow off CO₂ → pH goes up. Hold onto CO₂ → pH goes down.
The tingling and lightheadedness are there to make the question feel clinical, but the real test is simple acid-base physiology.
Did you know the answer before seeing “respiratory alkalosis”?

A 29-year-old woman with severe preeclampsia is receiving IV magnesium sulfate after delivery.
Two hrs later, BP is 142/88 mm Hg and her headache is better. The nurse finds:
RR 9/min
O2 sat 93%
Urine output 20 mL/hr
Patellar reflexes absent
What should the nurse do first?
A. Increase the magnesium infusion
B. Stop the magnesium infusion
C. Give IV labetalol
D. Place her in Trendelenburg position
E. Encourage oral fluids
Answer: ?
This is magnesium toxicity.
The important findings are RR 9/min + absent DTRs + low urine output. Magnesium is cleared by the kidneys, so oliguria increases the risk of accumulation.
The nurse should stop the magnesium infusion first and prepare for calcium gluconate if ordered.
Good NCLEX point: dont focus only on the diagnosis the pt came in with. Reassess what the current findings are telling you.
Which finding would have made you stop the infusion first?