David, so sorry to hear of you wife's problems. Unfortunately, we are not doctors here so we can't really give you medical advice, just some possibilities to ask your doctor about. You can try posting on the expert forum, they are doctors and may be able to help.
Having said that, she may have developed sepsis, or basically an increased level of toxins in her blood due to infection or some other cause. It is too common especially with surgery on the digestive system.