Nephro SA 1
A 75-year-old man (height 73 inches, weight 92.5
kg) presents to your institution with abdominal
pain and dizziness. He has a brief history of gastroenteritis and has had
nothing to eat or drink for
24 hours. His blood pressure reading while sitting
is 120/80 mm Hg, which decreases to 90/60 mm Hg
when standing. His heart rate is 90 beats/minute.
His basic metabolic panel shows sodium (Na) 135
mEq/L, chloride (Cl) 108 mEq/L, potassium (K)
4.7 mEq/L, carbon dioxide (CO2) 26 mEq/L, blood
urea nitrogen (BUN) 40 mg/dL, serum creatinine
(SCr) 1.5 mg/dL, and glucose 188 mg/dL. He has
no known drug allergies. Which is best for treating
this patient?
A. Administer furosemide 40 mg intravenously ×
1 dose.
B. Insert Foley catheter to check for residual
urine.
C. Administer fluid bolus (500 mL of normal
saline solution).
D. Administer insulin lispro 3 units
subcutaneously. ✔️Ans - Answer: C
Initial treatment of AKI requires identifying and reversing (if possible) the
insult to the kidney. This patient's symptoms and presentation are
consistent with prerenal azotemia because of volume depletion, so fluid
administration would be the best choice (Answer C is correct).
Nephro SA 2
A 44-year-old man is admitted with gram-negative
bacteremia. He receives 4 days of parenteral aminoglycoside therapy and
develops acute tubular necrosis (ATN). Antibiotic therapy is adjusted on
the basis of culture and sensitivity results. Which laboratory value is most
consistent with this
presentation?
, A. BUN/SCr ratio greater than 20:1.
B. Urinalysis with no casts visible.
C. Fractional excretion of sodium (FENa) more
than 2%.
D. Urinary sodium less than 20 mEq/L. ✔️Ans - Answer C:
Fractional excretion of sodium also distinguishes prerenal and intrinsic
renal damage. A low FENa (less than 1%) in an oliguric patient suggests
that tubular function is still intact, whereas a FENa greater than 2% is
common in intrinsic renal failure (Answer C is correct).
Nephro SA 3
A patient with chronic kidney disease (CKD) category
G4 (estimated glomerular filtration rate [eGFR] 25 mL/minute/1.73 m2)
has received a diagnosis of gram-positive bacteremia, which is susceptible
only to drug X. There are no published reports on how to adjust the dose of
drug X in patients with impaired kidney function. Review of the drug X
package insert shows that drug X has significant renal elimination, with
40% excreted unchanged in the urine. The usual dose for drug X is 600
mg/day intravenously and is provided as 100 mg/mL in a 6-mL vial. Which
is the best dose
(in milliliters of drug X) for this patient?
A. 3.6.
B. 4.1.
C. 4.5.
D. 5.5. ✔️Ans - Answer: B
Information regarding the fraction of drug excreted in
the urine (Fe) can help determine the proper dose of
a drug when specific dosing guidelines are not available. The Rowland-
Tozer equation can determine the percentage of the usual dose to give a
patient with known kidney disease (Q), considering the ratio of the
patient's renal function to normal (KF). For a patient with an estimated
CrCl of 25 mL/minute/1.73 m2, Q = 1 − [Fe(1 − KF)] = 1 − [0.4(1 −
25/120)] = 1 − 0.32 =
0.68, or 68% of the usual dose. If the usual dose is 600
mg, the adjusted dose would be 410 mg (600 mg × 0.68). Thus, the patient
should receive 4.1 mL of the 100-mg/mL preparation (410 mg/100
mg/mL) (Answer B is correct; Answers A, C, and D are incorrect).