A blood fridge is monitored to a level most people would find excessive: temperature every minute, an alarm at six degrees, and a log of every door opening, because a unit out of range is a unit destroyed. Ours logs an opening at 01:50 with the contact closed.
I am a biomedical scientist in transfusion. Sixteen years.
Why the monitoring is the way it is.
Red cells have to stay between two and six degrees. Above six for more than half an hour and the unit is out of specification and it is destroyed, and a unit is a person's donation and about a hundred and fifty pounds and sometimes the only one of its type in the region.
So the fridge has a probe in a bottle of glycol, which behaves like a bag of blood rather than like the air, logging every minute. It has an alarm that goes to us and to switchboard out of hours. It has an electronic lock with card access, and every access is logged: card, name, time, and which units were taken.
And it has a door contact, which is a magnetic switch that tells the system whether the door is shut, independently of the lock.
That is four separate records of the same cupboard.
At about ten to two in the morning the system logs a door open event.
No card. The lock log has nothing.
The door contact stays closed throughout, which the log also records, because it records the contact state every minute.
So the system believes the door opened and the switch on the door believes it did not.
The temperature is what makes it more than a paperwork problem.
Opening a blood fridge for ten seconds puts a visible notch in the trace. The air in it is at four degrees and the corridor is at twenty two, and you see a small fast rise and then a recovery, and if you keep the door open you get an alarm.
At ten to two the trace shows a notch.
Not a big one. It is consistent with a door open for about eight seconds. It is there most nights, and I have overlaid a hundred of them, and the shape is the shape.
What has been done.
The door contact was replaced in 2021 and again in 2023, and the second time with a different type.
The lock was replaced with the department's refurbishment in 2022. New reader, new card database.
The monitoring system was replaced in 2023. Different manufacturer, new probes, new logger, commissioned by their engineer with me standing there.
All four of those changes, and the event moved with none of them.
The fridge itself was swapped in 2023 when the new system went in, because it made sense to do it together.
The event is in the new fridge.
The units, which is the thing I have to be careful about.
Every unit in that fridge is tracked by barcode. In, out, to a patient or back to stock, with a person's name against each move.
Nothing has ever gone missing. I want that stated plainly because the first thing anybody thinks is theft, and the transfusion laboratory's whole existence is built on the traceability of every unit, and ours reconciles to the unit every single week and has for sixteen years.
Nothing is taken. The door opens and nothing is taken.
What is done about it.
It is recorded in the equipment log as a monitoring anomaly. Our transfusion practitioner knows, our lab manager knows, and it is on the risk register with a green rating and a note that no product has been affected.
It has been through two external audits. On both occasions the traces were reviewed, the reconciliation was checked, and the finding was that the cold chain is well managed.
What I do.
I do the daily checks, the weekly reconciliation, and the monthly review of the traces.
The one thing I have changed is that when I am on nights I do not do the one o'clock stock check in that room.
The stock check is a walk round with a handheld and it takes six minutes, and I used to do it at one because the phone is quiet then.
I do it at midnight now, and the reason is a night in 2023 when I was in there at ten to two by accident, having lost track of the time doing something else.
The fridge is under the bench on the far wall and it has a glass door, and there is a light in it that comes on when the door opens.
At ten to two the light came on.
The door did not move. I had my eyes on it and the seal did not so much as flex, and the light in that fridge, which is wired to the door switch and to nothing else, was on for about eight seconds, and the bags on the middle shelf were lit up from underneath the way they are when somebody is looking for a type.