Monday, August 04, 2008

Dose of ECT

Electoconvulsive therapy under anaesthesia has just started in our hospital. There is a new aneasthetist who will come daily to our hspital to help giving the anaesthesia. I was confused by the new ECT instrument in this new hospital. It measures the dose by Voltage and not by millicoulombs. All the instruments I worked on before are with a milliCoulombs gauge always fixated on 225, which can be increased to 250 if the seizure doesn't start from the first time. I have only see one or two cases when we needed to increase the dose to 250 milliCoulombs, with one case we used also hyperventilation of pure oxygen prior to the second trial.

This instrument is with Voltages gauge fixated at 70 Volts. I tried at 70, and no fit happened. The nurse assured me that they usually increase the dose to 110 Volts. I remembered that I have visited the ECT unit before few days and asked the working staff about the dose and they told me that it is fixated to 110 volts. I looked at the gauge and noticed that its maximum reaches more that 110 by about three folds. So I decided it is safe to go to 100 Volts. And no siezure happened. I stopped the treatment trial and posponed it to after tomorrow.

I started searching the net about the dose of ECT (by the way, I remember a student in psychiatry, a colleague of mine, have asked a senior psychiatrist about the Dose of ECT, and she responded: Do we measure ECT in DOSES? go read that in your book!!!), and I found the following:

From the Wikipedia:
"Modern ECT machines regulate the current to keep it constant and thus the voltage may vary up to a maximum, typically 450 V, but is usually around half that level in most cases."

From a site (is it an antipsychiatry site?):
"a small electric current is passed through the brain and the voltages used are no higher than 150 volts." and "the smallest current is 0.75 amps, more than enough to kill if applied across the chest"

American Journal of Psychiatry. 134: 9, (September 1977): 1010-1013:
"ECT parameters were conventional. i.e. 130 volts for 0.3 seconds."

The Royal College of Psychiatrists advocate using dose titration to each pateint (individualisation of dose) and not using a fixed dose for everyone. There are some ways of titrating the dose according to age that is not clear to me yet.

A study published in the Psychiatric Bulletin (2000) 24: 184-187 of the British Jouranl of Psychiatry says the following:
"Clinical opinion is currently divided on what is the most appropriate method of determining the stimulus dose for ECT. A survey of ECT practitioners in the USA reported that 12% used fixed-dose strategies, 39% dose titration and 49% formula-based methods "

I know nothing, at time being, about dose titration, nor about formula-based methods. But as I continued searching I started finding some clues.

I read the following abstract of a study:
"Seizure thresholds, as measured by dose titration, varied fourfold among our sample and the average value was 105.5 mC or 16.7 J.". So we can conclude that we should estimate the seizure threshold by dose titration. It seems that dose titration means giving a low dose and see whether a convulsion will occur or not, it not we give a higher dose. Read what they did in this study regarding titrating the dose:
"At the titration session, 27% of patients had seizures after a single stimulation and 37% had seizures after two stimulations. Only one patient required four stimulations to induce a seizure."

So it seems that it is not harmful to give a dose that will not cause seizure? They continue saying :
"No patient had significant adverse events associated with the dose titration procedure. "

The `half-age' method, however, is still a mystery for me.

1 comment:

Butterfly said...

I don't know the does or how they measured it, but ECT saved my life.