We mix 20U Pitocin in 1L LR/NS and titrate to bleeding and also to fluid tolerance in the patient....always remembering some have had LITERS Of fluid in labor due to epidural placements or other reason for fluid boluses.
There is where I and O are so important. Sometimes, in cases where bleeding is anticipated (multiple pregnancy or distension due to hydramnios, pt history, etc), we will mix 30 or even 40 units in the sam 1 liter bag of LR.
Interestingly, one place where I work, if a patient is hemorrhaging, we use CYTOTEC, rectally, 4 pills....I know, sounds horrible. But it WORKS! Ute clamps down tight, fast. This is the drug of choice for pp hemorrhage at this place, placing methergine 2nd and we don't even STOCK Hemabate anymore (expensive and in short supply). In every case so far, I have seen PR Cytotec work like a champ.
More than you asked for, Mark, but you know verbose me. That is what I do both places I work, regarding PP Pitocin mixing.