You want to extract all nutrients from other human. You build some sort of machinery that processes blood, taking most of nutritions - fats, proteins, carbohydrates etc. and some blood, so nutrients to blood ratio is higher than for normal blood. That makes the person you are extracting from malnourished, so their body start to process their muscles and body fat etc. until the person dies. Assuming machine tries to keep the person alive for as long as it is possible, how much "blood food" can you extract from a standard person? Is it even possible? Could someone live eating only this and drinking water? For how long? How long would it take to extract all the nutrients?
Yes - this is what babies do in the womb. A normal human can survive about 7 weeks without eating. Assuming a basal metabolic rate of 1,000 calories/day, that's about 50,000 calories contained in a normal human without replenishing. It's estimated that a fetus takes a little less than 300 calories a day from the mother. Say you are able to extract 1200/day to live off of from the human in addition to their own BMR, that's 2200/day and they'll live for about 3 weeks.
You will get less "nutrients" from what ever you propose than simply butchering the person and then eating all of the meat, organs and blood.
At the end of the day, the person is only going to have so many calories in their body and human bodies do not produce calories from nothing. The end result is that you need to feed the human food to keep him alive.
Not sure why you'd do this with a human, you can just eat human food and get more nutrients than you'd feed the human to keep him alive and then drinking his blood.
While I don't know the numbers like @wackozacko does, I would venture to suggest there are significant amounts of nutrients that will be wasted by not processing them directly from the meat and bones. of your victim.
On the other hand, if you are trying to keep the victim alive for as long as possible - you could definitely use them as a "nutrient farm". With very little sustenance, you could probably keep them alive for significant lengths of time. Not forever but definitely for months or maybe even years.
One of the advantages this has - is that your victims in addition to providing nutrients, are acting as a built of a filter. Their liver and kidneys are what are being stressed to clean up toxins, and you are simply extracting positive nutrients. This assumes that your machinery that performs the extraction is narrowly focused on taking out useful nutrients.