Low Conductivity Alarm on More Than One Machine
You are 45 minutes into a 4-hour treatment on Ms. K when her machine alarms "Low Conductivity," goes into bypass, and stops the blood pump. The display reads 12.6 mS/cm against a prescribed 14.0 mS/cm. You reset the alarm; it recurs within 3 minutes with the same reading. Ms. K feels fine and her vital signs are unchanged. Looking around the six-station bay, you see that the machine next to hers is also in bypass with a similar alarm, while the other four are running normally. The RO unit's own conductivity display reads normal, and the water treatment log shows a normal chlorine result from two hours ago. The acid concentrate jug on Ms. K's machine is about one-quarter full and the bicarbonate jug is full.
1. What are your first actions, and why is repeatedly resetting the alarm the wrong move?
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First actions.
- Leave the machine in bypass - that is what protects the patient. No dialysate is reaching the dialyzer, so the blood is safe but is getting no clearance.
- Do not keep resetting. A recurring alarm means the proportioning system is genuinely delivering out-of-range dialysate; resetting only clears the message, not the cause.
- Check the obvious consumables: acid jug not empty or kinked, bicarbonate fully dissolved and connected, concentrate connectors seated, no air in the lines.
- Note that two adjacent machines alarm while four do not. That pattern points away from a single machine's proportioning pump and toward a shared input - the same lot of acid concentrate, a shared delivery line, or a water problem. Check whether the affected machines share a concentrate source.
- Notify the RN and the technical/water lead immediately, and verify the dialysate with an independent conductivity meter rather than trusting the display.
Why resetting is wrong. Conductivity is a proxy for sodium concentration. A machine that is proportioning incorrectly can be reset into a normal-looking display while still delivering bad dialysate, and the patient absorbs the consequence.
2. Explain the physiologic risk of dialyzing against 12.6 mS/cm and what the machine's bypass is doing for the patient right now.
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The risk. Conductivity reflects the total ionic concentration, dominated by sodium. A reading of 12.6 against a prescribed 14.0 is roughly 10% low, and typical machine alarm limits are about ±5%.
- Low conductivity (hypotonic dialysate) creates an osmotic gradient that draws water into red cells. The result is hemolysis: back or chest pain, dyspnea, a falling hematocrit, and blood in the venous line that looks abnormally dark or port-wine colored. This can be catastrophic and is a medical emergency.
- High conductivity (hypertonic dialysate) causes hypernatremia - intense thirst, hypertension, restlessness, and eventually neurologic symptoms.
What bypass does. In bypass, dialysate is diverted away from the dialyzer. The patient's blood still circulates through the extracorporeal circuit but is not being dialyzed or ultrafiltered. That is the correct default: no dialysis is safer than wrong dialysis. It also means treatment time is being lost and must be accounted for.
3. The cause is found - an empty acid concentrate on the shared rack - and conductivity returns to 13.9 mS/cm. How do you decide whether to continue, and what do you document?
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Decide in this order.
- Confirm the reading is stable in range for several minutes and verify it with an independent meter - not just the machine's own sensor.
- Confirm the machine is out of bypass and that the other affected machine has been corrected and rechecked.
- Look at the patient: any back pain, dyspnea, change in the color of the venous blood, or vital sign change means stop and escalate, regardless of the display.
- Calculate the lost time. If the session will be materially short, the RN must obtain an order to extend the run or add a session - a technician cannot simply declare the treatment equivalent.
- If the cause cannot be identified and verified, do not resume.
Document. Time of onset, the alarm value and the prescribed value, time spent in bypass, troubleshooting steps, who was notified, the corrective action, the independent verification reading, the recalculated treatment time, and the patient's assessment throughout. The next shift and the quality program both need the timeline, not just "alarm resolved."