Brief Answer:
Cardiologist's and Anesthetist pre=op check-up, medications if required.

Detailed Answer:
Hi.
Thanks for your query and an elucidate history.
Read and understood your history about spinal anesthesia couple of years ago for rectal surgery, development of frequent heart beats - arrhythmia after one month of surgery.
Now you need another surgery in rectal region and your Doctor said that he will be putting you to sleep for couple of minutes. And you fear that the narcotics will bring back the arrhythmia.

You have questions pertaining to the following points:
Is there a chance?
> Chances are always there, but is the least with some special medicines that are used now-a-days low potential and very few side effects

What does anesthesia do to the heart and hearts rhythm?
>Most of the medicines used for anesthesia have different effects on the heart and heart rhythm and outside the scope of such discussion here as it is very detailed. I shall assure you soon about this.

Can it cause arrhythmia?
Most of the anesthesia medicines except few are not known to cause arrhythmia.

My thoughts and suggestions:
I can understand the plight and the anxiety you must be going through.
This is why a specific system has been developed in safe-medical practice in all the centers and if you follow this, there will be no problems you are worried about.
- First of all to get a complete cardiac check-up by a Cardiologist by clinical evaluation, examination and investigations. It is the Cardiologist who is going to assess the cardiac status at the moment, give you the medicines if something is anticipated and give you fitness to go ahead for anesthesia and surgery.
- The second step is to take a PAC, that is pre-anesthesia check-up. This is done by the Anesthetist who is going to administer the anesthesia for you, will study the Cardiologist's advise, do a clinical evaluation and examination on his own.
These two factors will give the decision to the Anesthetist which anesthesia to administer for you. This is totally his/her field.
By complying these factors, the anesthesia and surgery becomes safe for you and all.
Anything short of these measures can call for the problems, that no one would like to get into.
So please relax first, follow the strategy, insist for the way I explained and you will be in the safest of the hands.

I hope this answer helps you to have a very safe anesthesia and surgery.
Wishing you all the best.
Please feel free to ask for further relevant queries if you feel that there is a gap of communication between us, I shall be happy to assist you further if need be.

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