CHBT Dialysate Composition and Chemistry 2 — Questions and Answers
Question 1: Why must acid and bicarbonate concentrates be kept separate until just before mixing in the proportioning system?
- Premixing causes bicarbonate to precipitate as calcium and magnesium carbonate (Correct answer)
- The mixture is explosive
- Premixed solution becomes too acidic
- Regulations require separate storage only
Correct answer: Premixing causes bicarbonate to precipitate as calcium and magnesium carbonate
When acid and bicarbonate concentrates are combined early, calcium and magnesium ions react with bicarbonate and precipitate out of solution, clogging lines and altering composition.
Question 2: What does the 'A concentrate' (acid concentrate) typically contain that is NOT in the 'B concentrate' (bicarbonate concentrate)?
- Calcium, magnesium, potassium, glucose, and acetic acid or citric acid (Correct answer)
- Sodium bicarbonate only
- Sodium chloride only
- Phosphate buffer
Correct answer: Calcium, magnesium, potassium, glucose, and acetic acid or citric acid
The acid concentrate contains the divalent cations (calcium, magnesium), potassium, glucose, and an acid (acetic or citric) to keep them in solution; the B concentrate contains sodium bicarbonate.
Question 3: Sodium profiling during hemodialysis involves:
- Varying the dialysate sodium concentration during treatment to improve hemodynamic stability and reduce intradialytic symptoms (Correct answer)
- Restricting sodium intake on dialysis days
- Using a fixed low-sodium dialysate throughout treatment
- Measuring serum sodium every 30 minutes
Correct answer: Varying the dialysate sodium concentration during treatment to improve hemodynamic stability and reduce intradialytic symptoms
Sodium profiling gradually decreases dialysate sodium from higher to lower levels during treatment, helping preserve osmolality early and reducing cramping and hypotension.
Question 4: What is the consequence of using dialysate with too low a sodium concentration?
- Hyponatremia, hypotension, muscle cramps, and risk of cerebral edema (Correct answer)
- Hypertension and volume overload
- Hyperkalemia
- Metabolic alkalosis
Correct answer: Hyponatremia, hypotension, muscle cramps, and risk of cerebral edema
Hypotonic dialysate pulls sodium from the blood, causing hyponatremia that leads to osmotic fluid shifts, cramping, hypotension, and potentially dangerous cerebral edema.
Question 5: Acetate was largely replaced by bicarbonate as the dialysate buffer primarily because:
- Acetate metabolism caused hemodynamic instability, vasodilation, and was poorly tolerated by some patients (Correct answer)
- Bicarbonate is cheaper to produce
- Acetate caused hyperkalemia
- Regulatory agencies mandated the switch
Correct answer: Acetate metabolism caused hemodynamic instability, vasodilation, and was poorly tolerated by some patients
Acetate requires hepatic metabolism to generate bicarbonate and its metabolites cause vasodilation, contributing to intradialytic hypotension and fatigue — bicarbonate dialysate is better tolerated.
Question 6: When mixing a bicarbonate concentrate from dry powder, which precaution is essential?
- Use water that meets dialysis water quality standards and mix per manufacturer instructions to ensure sterility and correct concentration (Correct answer)
- Use tap water for cost savings
- Add the powder to hot water to speed dissolution
- Mix 24 hours in advance and refrigerate
Correct answer: Use water that meets dialysis water quality standards and mix per manufacturer instructions to ensure sterility and correct concentration
Bicarbonate solutions support bacterial growth rapidly; they must be prepared with purified water, used promptly (within manufacturer-specified timeframes), and mixed per protocol.
CHBT Dialysate Composition and Chemistry 2
Why must acid and bicarbonate concentrates be kept separate until just before mixing in the proportioning system?