“Can my mother's sugar levels fluctuate during her bypass surgery?”

The chances are 100% and will be monitored by the anesthesia team during surgery. If you trust your surgeon, trust your anesthesiologist who is also a medical doctor who has done additional post graduate training. No surgical team can function without good anesthesia to keep the patient safe.

Yes, there is a high chance of this.

I will tell you what I tell my patents before surgery. It does not matter who you are or your age surgery is always the last thing that is done for a patent. I tell my patents the truth. If they may not have a good chance to come through the surgery I tell them if it is the only option I tell them. If your mother is able to understand what is being said let her make the choice. it is her life not yours. I know we want our loved ones to stay for ever but God only give us so much time to be here. I ask you not to think about yourself and help Mom make the choice that is best for her and what she wants to do. It sounds like if she does not have the surgery she may not be with you long anyway. What I would do if it was my Mom I would pray and ask God to help everyone to come up with the right answer. I went through something like this with my Mom and she made the choice and I know it was the right thing to do. I am the age of your Mom and I know how my daughter would feel if it was me or my wife. I will be praying for your Mom and your family. Oledochouse

The surgical stress will certainly will make her blood go into an abnormal range. It will be closely followed during the in-patient stay and monitored closely before and after surgery.
You should not worry. She will be well controlled and monitored.

The blood sugar levels are monitored routinely during surgery, so no worries. If it is high, insulin will be continously be administered.

Good question you are asking. Blood sugars vary due to many factors. Stress and Cortisol and Catecholamine release directly affects the sugar. Liver storage of Glycogen is the source for glucose liberation on an empty stomach. Excercise plays a big role. Sugar content of food is critical. Fasting is another critical factor in sugar control. Insulin obviously works by transporting glucose across the cell membrane with an added water molecule. During surgery, the metabolism is lowered significantly and as the temperature also drops on bypass the body and the cells need less glucose and oxygen. But you should not be concerned. The anesthesiologist will be doing blood glucose assessments before, during and after the surgery and she will be receiving drips that contain glucose as well. In addition, she will be on an intravenous regimen of administering insulin, so you need not be concerned.

Extremely likely, I would not be too concerned as her NPH is likely to be discontinued until her normal heating habits are resumed.

Her physician should manage her blood sugar as per protocol.

The blood sugar levels will be closely monitored and managed during bypass surgery.