I am an RN and IBCLC. I have had a TON of training in this area and recertification is in a month so LOTS of recent training.
I can not count the times I heard health care professionals including OB's pediatricians, maternity nurses give incorrect info. If I had a dime every time I heard wrong info id be pretty wealthy. I wouldn't ask your bariatric surgeon or PCP's opinion about breastfeeding, this is most likely a very foreign subject to them, of course mention it so they know you are lactating, but expect to hear the pump and dump myth. Anesthesia has a very short half life, I have consulted on post op gall bladder removals, appendectomy's etc and was able to confer with their surgeon utilizing resources like Dr Hales book or forum located at ibreastfeeding.com so that we could agree on the safety of the breastmilk/resuming lactation.
Contact the hospital IBCLC before surgery, she should be able to hook you up with a hospital grade pump while you are inpatient as well as storage containers and a place to store milk. She should also be able to review your post op orders and see that meds are compatible with lactation. A lot of the same meds given after WLS are given after a c-section, pain killers, anti nausea, benadryl, etc.
More info here:
http://kellymom.com/category/bf/can-i-breastfeed/meds/
Meds approved for lactation by American Academy of Pediatrics (Not all meds have been evaluated yet by AAP, this does not mean they are not compatible, you can look at Dr Hales site and/or book, call local IBCLC or La Leche league, they can not "Approve" a med but can read to you the information word for word so you make your own informed decision:
http://kellymom.com/bf/can-i-breastfeed/meds/aap-approved-me ds/
As far as any scan after surgery, barium swallow etc, this is what breastfeeding expert Dr Jack Newman states in his myths about breastfeeding:
begin quote "
by Jack Newman, MD, FRCPC
1. Nursing mothers cannot breastfeed if they have had X-rays.
Not true! Regular X-rays such as a chest X-ray or dental X-rays do not affect the milk or the baby and the mother may nurse without concern. Mammogramsare harder to read when the mother is lactating, but can be done and the mother should not stop breastfeeding just to get this done. There are other ways of investigating a breast lump. Newer imaging methods such as CT scan and MRI scans are of no concern, even if contrast is used. And special X-rays using contrast media? As long as no radioactive isotope is used there is no concern and the mother should not stop even for one feed. Herein are included studies such as intravenous pyelogram, lymphangiogram, venogram, arteriogram, myelogram etc. What about studies using radioactive nucleotides (bone scans, lung scans, etc.)? The baby will get a little radioactive nucleotide. However, as we often do these very same tests on children, even small babies, and the potential loss of benefits if the mother stops breastfeeding are considerable, the mother should continue breastfeeding. The exception is the thyroid scan. This test must be avoided in breastfeeding mothers. There are many ways of evaluating the thyroid, and only very occasionally does a thyroid scan truly have to be done. Check first before taking the radioactive iodine, the test can wait until you know for sure. In many cases where the scan must be done, it can be put off for several months." end quote
Dr Jack Newman is a renowned breastfeeding expert, you can email him personally here and ask him his opinion on WLS while breasttfeeding http://www.breastfeedinginc.ca/contact.php
My concerns would be your health, you would need to be especially vigilant about nutrition and vitamins, discuss plan with bariatric nutritionist, your body will make milk but if you are lacking it will take from you making you feel run down. Also id ask about ketones from rapid weight loss entering into breastmilk and if they are safe for your baby, I can not find much updated info on that so that's definitely a question for Dr, Newman.