Why white gums and tongue?

[CharlesColvin]

My baby girl B, was 12 going on 13. She was Boarder collie/ Australian Shepard mix. Monday 7-16-2018 at about 3pm she started panting hard and fast. I felt her and her gums were cold, and light pink. About 2 minutes later she was fine again. I called her vet, only to be told her vet was off, and the other two were with customers. And they would call back. I held B and petted her she seemed fine. We went to the living room, where I laid on the floor next to her. She was quite content. At about 5:00 she got up and went to the door. We normally go for a walk at that time. She went 10 steps and poo’d, not normal for her. My son watched her as I got shoes on. I went out front and he told me her tongue was white. She walked to the end of my truck and set down, I got the mail from the mail box and went and opened the door to my bedroom. She walked 2/3 rd of the way there and looked at me like, I can’t get there from here pa. So I went and held her hind 1/4s up and she walked in to my bedroom... she laid on the floor. I laid next to her, about 1/2 an hour later she started panting hard and again her tongue was white as were her gums. I listened but could not hear any heart beat.(continuesly telling her I loved her) she slowed panting looked me in the eyes and closed hers. She stopped breathing, I listened for her heartbeat but there was non, I tried cpr for 10 minutes with no change. She is gone, and I miss her. She was my life. What did the white gums and tongue mean? On her last check up she was fine, no blood problems, no heart worm problems. She never showed any sign of pain.

[ginger899]

I am so sorry about B's passing and how much you loved her is obvious.

The gums and tongue lose colour when there is internal bleeding.
If this happened sudden;y, and she seemed fine just before this....then my suspicion is she passed away from Hemangiosarcoma.

My own dog had this.

Dogs who have Hemangiosarcoma can suddenly collapse and die -from being quite well, even hours or a day or so before.

Hemangiosarcoma isn't detectable through bloodwork or normal health checks, and only diagnostic methods such as ultrasound can spot bleeding internal tumours. But who sends a perfectly healthy dog for an ultrasound?
You couldn't have known, and in my opinion, the vet wouldn't even have known.

Hemagiosarcoma is called the "silent killer" of dogs because it usually gives no warning of its presence until there is an internal haemorrhage. And that is often fatal.

It is a cancer of the "endothelial cells" (the cells which line blood vessels.) The primary tumour is often on the spleen, but can be on the heart, brain, liver, or within the abdomen too. By the time it is even diagnosed, it has spread all through the body via blood vessels, and does not just remain at the tumour site.

There is no cure. Even chemotherapy can only usually prolong life by a very short margin, and it may not even be worth it for the side effects.

Our own vet told me that it is often not acutely painful as such, but  more "uncomfortable" for them, and of course, their blood pressure drops from all the blood loss internally.
So B would have slowly slipped into a gentle unconsciousness by the sound of it. And she was with you and knew you were by her to comfort her.

Bless her Soul.
I send you my deepest condolences.