QW55 October 2025

Question 1

Clinical Case Scenario : QA

A 70-year-old man with known decompensated alcoholic liver cirrhosis presents to the ICU.

History

One-day history of worsening confusion, reduced urine output, and refractory hypotension despite fluids.
Hypertension, type 2 diabetes mellitus.
No history of chronic kidney disease before this admission.

Vital Signs

HR: 104/min, BP: 84/60 mmHg (MAP 64 on norepinephrine infusion).
Temp: 38.7°C.
SpO₂: 94% on 4L O₂ via nasal cannula.
RR: 22/min.

Laboratory Findings

Serum Na⁺: 172 mmol/L
Serum osmolarity: 350 mOsm/kg
pH: 7.32, HCO₃⁻: 18 mmol/L
MAP: 64 mmHg on norepinephrine infusion

Which of the following is the most appropriate way to use 3% NaCl during CRRT to safely manage this patient’s hypernatremia?

A. Add 3% NaCl directly into the CRRT substitution/replacement fluid to match the patient’s serum sodium, thereby preventing rapid correction.

B. Infuse 3% NaCl as a separate infusion running via a central line and titrate rate to counteract sodium removal during CRRT.

C. Increase dialysate sodium concentration by adding 3% NaCl into the dialysate bag and run CRRT at high efficiency to normalize sodium quickly.

D. Withhold CRRT until serum sodium is below 155 mmol/L, then initiate standard prescription to avoid osmotic shifts.

Question 2

Clinical Case Scenario: QB

The same patient is started on continuous renal replacement therapy (CRRT). On day 1, his laboratory results are:

Serum sodium: 172 mmol/L
Weight: 70 kg
CRRT prescription: CVVHDF with dialysate sodium concentration of 140 mmol/L, total effluent rate 25 mL/kg/hr
No ongoing free water losses (insensible losses balanced by replacement)

To buffer sodium loss, you decide to infuse 3% NaCl via a central line during CRRT.
(Assume distribution volume of Na = 0.6 × body weight, and [Na] in 3% NaCl = 513 mmol/L).

What is the approximate rate (mL/hr) of 3% NaCl infusion required to limit the serum sodium drop to less than 10 mmol/L/day?

A. 30 mL/hr

B. 50 mL/hr

C. 75 mL/hr

D. 120 mL/hr