With all hemodialysis patients using an AV fistula, it’s good to know the condition of your ‘lifeline’ and that it is not at risk of clotting.
The fistula flow should be periodically checked, and this can be done by ultrasound techniques, which can be time consuming and more expensive to deliver, and by Blood Temperature Monitoring (BTM).
As I dialyse on the NxStage, there is no facility on the machine to check using BTM, so approximately annually, I go to the local dialysis unit to dialyse for one session, as they have Fresenius 4008 machines, some of which are fitted with a BTM function.
The process involves getting on dialysis in the normal way, and then soon after settling, placing the arterial and venous lines in the BTM unit on the front of the Fresenius machine, and setting it to measure. The measure takes about 5 minutes to register, and is repeated to give two values, from which a mean value can be extracted. Then, the venous and arterial line connections are reversed temporarily, so you are extracting your blood from the venous line, and returning it to you via the arterial. 2 further BTM measures are taken, after which you can connect up normally again and carry on with the rest of your dialysis session. The blood pump speed is set at a constant for the test at 300ml/min.
From the measures taken the normal flow of blood through your fistula can be obtained, and standards will vary from centre to centre, but in this case, so long as the flow is 500ml/min or more then that is considered to be ok. Generally, there is a greater risk of clotting at 300ml/min or less. Additionally, the results compared with past tests will give some indication to the blood flow health of the fistula. I have just had mine measured at 1300ml/min, compared to 1100ml/min last time. Having had my fistula now for 22 years I am keen to ensure it is looked after and continues to work for me, so I am pleased with the results.
So, if you have not had your fistula checked in the past year or more, consult with your local unit no matter whether you are an outpatient at your local dialysis unit, or you dialyse at home. It’s your lifeline, care for it, and make sure it is checked over.
