Fluids, Electrolytes and Renal Nursing

Why C is correct

In renal failure the kidneys cannot excrete magnesium, so magnesium-containing antacids can cause dangerous hypermagnesemia with flushing, hypotension, bradycardia, and a prolonged PR interval; this medication history is the most significant to report because it identifies a reversible, ongoing source.

Why the other options are wrong

• A — Missed dialysis: Concerning and contributory, but the antacid intake is the specific exogenous load driving the toxicity.
• B — Facial flushing: An effect of the hypermagnesemia, not the root cause to report.
• D — Low-normal BP: Also an effect of the magnesium load rather than the cause.

Why B is correct

Mannitol should be avoided in a client with acute kidney injury, oliguria or anuria, and its adverse effects are volume overload and hyperosmolality.

An osmotic diuretic needs kidneys that still make urine.

Why the other options are wrong

• A — "Give the mannitol now so the pigment is flushed through his kidneys": Mannitol is part of some crush-injury care, but it starts only after the client keeps up an adequate output.
• C — "Hold the mannitol until the dark color of his urine has cleared": Urine color does not decide this order; his scant output does.
• D — "Give the mannitol together with sodium bicarbonate to protect his kidneys": Evidence does not support pairing mannitol with bicarbonate, and his scant output still rules mannitol out.

Why B is correct

Dry weight is her weight after a hemodialysis session has removed all extra fluid from her body. If too much fluid builds up between sessions, it is harder to reach, so controlling her liquid intake matters.

Why the other options are wrong

• A — "Her weight at the end of each session, whatever amount of fluid was removed": Dry weight is a weight taken after a session, but it counts only when all the extra fluid has come off.
• C — "Her weight before a session, including the fluid gained since the last one": That reading still carries the fluid gained between sessions, which the run has to remove.
• D — "Her usual weight from before her kidneys failed, used as a long-term goal": Dry weight is set for her body as it is now, without extra fluid, and her provider helps decide it.

Why A is the answer

An arterial line is a thin tube placed in an artery, usually at the wrist, to show the blood pressure beat by beat and to draw blood. Maintenance fluid, drugs and boluses must never run through it; the maintenance fluid belongs on the peripheral IV.

Why the other options are not the answer

• B — "Drawing the ordered blood samples through the arterial line": Sampling is a correct use of the line, but blood only comes out through it; nothing is infused except its pressurized flush.
• C — "Checking the color and warmth of the hand beyond the arterial line": Accurate; the blood flow to that hand is watched the whole time the line is in.
• D — "Keeping the arterial line's pressure tubing connected to its pressure bag": Accurate; the firm tubing and pressure bag keep the line filled under steady pressure and mark it as arterial.

Why D is correct

Two separate processes are pushing the pH up at the same time. Prolonged vomiting strips away gastric acid and lifts the bicarbonate to 30 mEq/L — a metabolic alkalosis. Anxious hyperventilation independently blows off carbon dioxide and drops the PaCO2 to 32 mm Hg — a respiratory alkalosis. Because both push in the same alkalotic direction instead of one offsetting the other, the pH climbs to 7.59, which is the signature of a mixed disturbance.

Reference values

• pH: 7.35 to 7.45; 7.59 is well above this range
• PaCO2: 35 to 45 mm Hg; 32 mm Hg is below this range
• HCO3: 22 to 26 mEq/L (some labs cite up to 28); 30 mEq/L is above every variant

Why the other options are wrong

• A — Pure metabolic alkalosis, with the low PaCO2 as appropriate respiratory compensation: the metabolic alkalosis this names is present, but respiratory compensation for a metabolic alkalosis runs the other way — the lungs slow down and the PaCO2 would RISE toward about 44 mm Hg, not fall to 32. A falling PaCO2 here is a second alkalotic process, not compensation for the first.
• B — Pure respiratory alkalosis, with HCO3 reflecting early renal compensation: renal compensation for a respiratory alkalosis lowers the bicarbonate. This bicarbonate is elevated at 30, so it cannot be compensation — and the vomiting history explains why it is up.
• C — Compensated metabolic alkalosis with the pH fully corrected: compensation never overshoots past normal into the opposite direction, and a pH of 7.59 is nowhere near corrected.