Chlorhexidine Allergy

My 13 year old Korat boy recently went to have 2 teeth removed. The surgery went well enough until the vet administered chlorhexidine antiseptic after the removal. My cat suffered a massive allergic response which resulted in his heart stopping. The vet injected atropine and he regained consciousness but after that it was all downhill. He never recovered and died 4 days later. Heart, liver and kidneys were all fine and there were no lung problems (the vet took X rays). The severity of the allergic response leaves me to believe the vet failed to dilute the chlorhexidine before giving it. When he died my boy's gums were badly ulcerated from the antiseptic. Has anyone come across a similar phenomenon, especially with a known diluted chlorhexidine solution? The instructions for chlorhexidine require it to be diluted to avoid allergic responses. 

I'm so very sorry for your loss.