Facebook groups offer a place to ask questions and discuss best practices for some of the more challenging aspects of your work in electroencephalography (EEG).
Recently, we noticed one particular question in the group I’m an EEG tech, not an ECG tech… gain a lot of attention: “How long after dialysis do we wait before we can do EEG?”
Responses varied and pointed to a general lack of clarity around the topic.
- “It’s supposed to be 24 hours. But some places don’t follow that.”
- “Some say at least 4-6 hours.”
- “We used to wait several hours then all of a sudden after many years of doing this we were told it ‘doesn’t matter.’ I’ve actually done EEGs during dialysis!”
So, what is the answer? And why is there so much confusion?
To help answer these questions, we reached out to Petra Davidson, an EEG tech and author of the upcoming paper, The Effect of Chronic Hemodialysis on EEG: A Retrospective Study.
Davidson said the ideal wait time is six hours. There are, however, circumstances such as suspected status epilepticus where medical necessity overrides waiting.
This conclusion is based on an extensive literature review, consulting with specialists, and her own research. Unfortunately, there is no published standard offering this or any other advice, due to a lack of “firm evidence,” Davidson said.
And the evidence that does exist hasn’t been well communicated throughout the field.
“Of all the labs I’ve worked in, I’ve never worked in one where there has been a formal policy written about when to do the EEG in regards to dialysis,” Davidson said.
Instead, best practices are shared anecdotally among techs and are often based on what they learned in school decades ago.
Previous research shows that EEGs following dialysis have led to false epilepsy diagnoses. It was later determined that these false diagnoses had more to do with the composition of the diastylate used in dialysis, rather than abnormal brain activity. Despite this, there has been little research around the proper time to wait after dialysis.
For this reason, Davidson took on the subject with nephrologist Dr. Fawad Qureshi at the Mayo Clinic Health System, in Mankato, Minnesota. In their still-unpublished study, seven of the eight patients observed had abnormal EEGs following dialysis and showed “slowing in one form or another.”
Despite their findings, Davidson said the effect of dialysis on EEG has continued to be largely unstudied.
“We still don’t have very specific findings on what we would see on EEG before, during, or after dialysis, and the time period with which we could do an EEG and not see those epileptiform changes,” Davidson said.
Her advice to techs?
In addition to being cautious and waiting the six hours, EEG techs should confirm if the patient has encephalopathy before proceeding with an EGG.