causing my dog pain...do you think they understand?

I do think animals can understand that people cause them pain sometimes in an effort to help. I've seen thrashing horses caught in barbed wire stand statue-still when someone with a pair of wire cutters came by, even though cutting the wire out of the leg must have hurt almost as much as getting it stuck in the first place.

I think animals can generally "sense" a person's intentions (body language, pheromones, past experiences, "energy," what have you) and learn that while they might not understand a particular situation, they're trusting you to do what's best... even if it's not particularly fun at that moment.

We had to have that exact same thing done to our Anna once. She caught a dew claw on a doggie door flap and partially ripped it out, so they said the best thing was to take it off. I remember that scream you're talking about. And you're right, the vet and tech seemed to feel as awful as I did! But she was immediately okay with it, licking and wagging. Another great thing about dogs, forgiveness!

I know beyond a shadow of doubt they do.
 
My cocker Billy has IMHA (immune-mediated hemolytic anemia) -- and it's was a rough year last year.  He had SIX transfusions in a month, and has had blood drawn at least once a week since last May.  Trust me -- getting stuck that many times is no picnic, but he understands -- not just with one vet but with MANY, and many vet techs (not all of whom are 'good' at drawing blood).  But he is incredibly patient -- not by nature either, but this seems to be a RESULT of this time ... he seems to truly understand and have a grasp that he almost died, and that he was deathly ill for a LONG time, and yet all these people have tried SO hard to help him get better.
 
Every vet who touches him remarks on how easy he is to work on -- and this is the dog who, when we got him 2 1/2 years ago nearly took off the vet's hand for looking in his ears!!
 
Yes-- they do know.  He KNOWS how painful that nail was *before* it was removed.  He also knows and smells how upset YOU were during the process, so he knows you didn't do it lightly.  He knew that everyone in that room was upset, and not 'enjoying' hurting him.  Remember dogs have this incredible sense of smell so they sense 'fear', 'sadness' and other emotions on a scent level ... not just 'emotional'.  The dog probably felt guilty in a way for getting everyone upset!!
 
You all handled it well -- sedation is risky, and when you can avoid it for a brief moment of pain it is the better way to go.  Cudos to your vet!!

Thanks for the responses.  You're probably right...dogs are pretty remarkable animals, and I'm sure that Chase realized that none of us enjoyed hurting him.
 
Now to see what his reaction is this evening when we take him in to have the bandage removed...

I've often wondered at those times when I clonk my dogs by accident (step on toe or tail, run into them--big dogs, small house, it happens quite a bit) if they understand by my concilliatory tone that I didn't actually mean to do it. They don't seem to be taking up arms against me yet, so I guess they do.