CDN Fluid and Electrolyte Balance in Dialysis 1 — Questions and Answers
Question 1: Which parameter is used to determine the ultrafiltration volume goal for a hemodialysis patient?
- Predialysis BUN level
- Difference between current weight and estimated dry weight (Correct answer)
- Serum creatinine level
- Residual renal function
Correct answer: Difference between current weight and estimated dry weight
Ultrafiltration volume is calculated as the difference between the patient's current (wet) weight and their estimated dry weight (ideal fluid-free weight).
Question 2: A dialysis patient's predialysis serum potassium is 6.8 mEq/L. Which dialysate potassium concentration is most appropriate?
- 4.0 mEq/L
- 3.0 mEq/L
- 2.0 mEq/L (Correct answer)
- 0 mEq/L
Correct answer: 2.0 mEq/L
A 2.0 mEq/L dialysate potassium provides adequate gradient to remove excess potassium while reducing the risk of arrhythmia from overly rapid shifts.
Question 3: What is the normal serum phosphorus target range for dialysis patients per KDIGO guidelines?
- 1.0–2.0 mg/dL
- 2.5–4.5 mg/dL (Correct answer)
- 3.5–5.5 mg/dL
- 4.5–6.5 mg/dL
Correct answer: 2.5–4.5 mg/dL
KDIGO guidelines recommend lowering elevated serum phosphorus toward the normal range of approximately 2.5–4.5 mg/dL in dialysis patients.
Question 4: Which fluid restriction guideline is commonly recommended for anuric hemodialysis patients?
- 500 mL/day
- Urine output plus 500–750 mL/day (Correct answer)
- Urine output plus 1,000 mL/day
- No restriction needed
Correct answer: Urine output plus 500–750 mL/day
Non-anuric patients are restricted to their urine output plus 500–750 mL/day to account for insensible losses while preventing interdialytic fluid overload.
Question 5: Hypermagnesemia in dialysis patients most commonly results from which of the following?
- Excessive dietary protein intake
- Regular use of magnesium-containing antacids or laxatives (Correct answer)
- High dialysate magnesium concentration
- Hyperparathyroidism
Correct answer: Regular use of magnesium-containing antacids or laxatives
Dialysis patients who use magnesium-containing antacids or laxatives are at risk for hypermagnesemia because the kidneys cannot excrete excess magnesium.
Question 6: A dialysis patient presents with a serum calcium of 11.8 mg/dL. Which medication is the most likely culprit?
- Sevelamer carbonate
- Calcium carbonate phosphate binder (Correct answer)
- Cinacalcet
- Lanthanum carbonate
Correct answer: Calcium carbonate phosphate binder
Calcium carbonate is a calcium-based phosphate binder that contributes to hypercalcemia when taken in excess or with high-calcium dialysate.
CDN Fluid and Electrolyte Balance in Dialysis 1
Which parameter is used to determine the ultrafiltration volume goal for a hemodialysis patient?