CCHT Dialysis Equipment Operation 2 — Questions and Answers
Question 1: What does the conductivity monitor on a hemodialysis machine measure, and why is it critical?
- Flow rate of dialysate through the circuit
- Concentration of electrolytes in the dialysate solution (Correct answer)
- Temperature of the blood returning to the patient
- Pressure in the venous blood line
Correct answer: Concentration of electrolytes in the dialysate solution
Conductivity measures the total ionic concentration (electrolyte content) of the dialysate, ensuring the correct concentration for safe treatment.
Conductivity (measured in mS/cm) reflects the total dissolved ionic solutes in dialysate, primarily sodium and bicarbonate. If conductivity is outside the set range (typically 13 to 16 mS/cm), it indicates incorrect dialysate concentration, which could cause dangerous electrolyte shifts in the patient. The machine alarms and bypasses dialysate to drain until corrected.
Question 2: During hemodialysis, the blood pump suddenly stops and the venous pressure alarm activates. What is the most likely cause?
- Air in the blood lines
- Clotting in the venous needle or access (Correct answer)
- Low dialysate temperature
- Inadequate heparin dosing
Correct answer: Clotting in the venous needle or access
A sudden increase in venous pressure with blood pump stoppage typically indicates a clot or obstruction in the venous return pathway.
Venous pressure monitors resistance to blood flow returning to the patient. A sudden pressure spike suggests a clot in the venous needle, access stenosis, or kinked tubing. Low venous pressure may indicate access problems, needle dislodgement, or disconnection. Persistent high venous pressure despite troubleshooting may require needle repositioning or access evaluation.
Question 3: What is the purpose of the deaeration chamber system in a hemodialysis machine?
- Remove bacteria from dialysate
- Remove dissolved gases from dialysate before patient contact (Correct answer)
- Cool the dialysate to proper temperature
- Measure dialysate flow rate
Correct answer: Remove dissolved gases from dialysate before patient contact
The deaeration system removes dissolved gases (primarily CO2 and O2) from dialysate to prevent microbubble formation that could damage the dialyzer membrane.
When concentrate is mixed with treated water to form dialysate, dissolved gases can form microbubbles. These bubbles can reduce dialyzer efficiency by occupying membrane surface area. Deaeration uses vacuum or reduced pressure to remove dissolved gases before the dialysate enters the dialyzer.
Question 4: Which parameter must be verified before connecting a patient to the hemodialysis machine?
- The dialysate color and turbidity
- Blood flow rate, dialysate flow rate, temperature, and conductivity (Correct answer)
- The machine's last service date
- The patient's hemoglobin level
Correct answer: Blood flow rate, dialysate flow rate, temperature, and conductivity
All dialysis prescription parameters must be verified against the patient's prescription before treatment begins.
Before patient connection, the technician must verify: blood pump speed (typically 300 to 500 mL/min), dialysate flow rate (500 to 800 mL/min), temperature (35 to 37 degrees C), conductivity (within range), heparin dose/rate, and UF goal. These settings are prescribed by the nephrologist. Incorrect settings can cause electrolyte imbalances, hemolysis, or inadequate dialysis.
Question 5: What action should a technician take if the air detector alarm activates during hemodialysis?
- Silence the alarm and continue treatment
- Clamp the venous line and stop the blood pump immediately (Correct answer)
- Increase the blood pump speed
- Remove the patient from the circuit gently
Correct answer: Clamp the venous line and stop the blood pump immediately
An air detector alarm requires immediate clamping of the venous blood line and stopping the blood pump to prevent air embolism.
Air embolism is a potentially fatal complication. When the air detector (ultrasonic sensor on the venous drip chamber) detects air or foam, it automatically stops the blood pump and clamps the venous line. The technician must NOT override or silence this alarm. The patient must be assessed, air removed from the circuit, and the cause identified before resuming treatment.
Question 6: How does single-needle dialysis differ from standard two-needle hemodialysis?
- It uses one needle for access and relies on peritoneal membranes for diffusion
- It alternates blood withdrawal and return through a single needle using a dual-lumen approach (Correct answer)
- It requires a higher blood flow rate to compensate for single access
- It is only used for patients with central venous catheters
Correct answer: It alternates blood withdrawal and return through a single needle using a dual-lumen approach
Single-needle dialysis uses one needle or dual-lumen catheter, alternating between drawing blood out and returning it, reducing efficiency compared to standard two-needle access.
In single-needle mode, blood is drawn from the patient during the arterial phase, then returned during the venous phase, alternating rapidly. This is less efficient than two-needle dialysis because recirculation (returning blood being immediately withdrawn) reduces clearance. It may be used when only one needle site is available, though two-needle access is standard for optimal dialysis adequacy.
CCHT Dialysis Equipment Operation 2
What does the conductivity monitor on a hemodialysis machine measure, and why is it critical?