I can't answer the medical questions, but the results will depend a bit on your particular vampire lore.
* If your vampire hypnotizes or otherwise sedates the victim beforehand, and the victim remains sedated, a slower heartrate will give them more time.
* If they're aware and struggling, they'll loose blood faster and might also tear the wound. But they can shout for help which is a massive bonus!
* If vampire bites are usually quick-sealing into pinprick holes, they'll loose less blood.
* Amount of blood drained changes things, too, as does the size and health levels of your victim. I can give 500ml of blood (single needle puncture, wound sealed with a plaster afterwards), which is roughly 11% of my total blood, and be fine to leave almost immediately afterwards.
* If your victim was out drinking before the incident, or at an intense gym class, or running from the off-putting fanged person on their tail, they might be in serious trouble from the dehydration.
* If your victim is female and anemic by nature/by time-of-the-month/by pregnancy, they're in real trouble.
* Things the victim might experience: dizziness if moving quickly, inability to stand for a bit after the incident, thirst, craving sweet things (if low energy) or a burger (if low iron), craving dirt, clay, corn starch, paint chips, cardboard, cleaning supplies or ice (low iron), cracked lips (dehydration/low iron), tiredness, paleness, loss of breath, headaches, feeling like your heart is beating too fast. Cold hands and feet.