Bleeding in Pregnancy

The uterus gets a lot of blood, up to 700mL/min. The average blood volume of an adult is around 5L so this represents 15% of cardiac output. So when the uterus bleeds, it bleeds a lot very quickly. In a normal vaginal delivery, blood loss can be up to 500mL, and up to a liter in a C-section. Compare this to most surgeries where we estimate blood loss to be a tenth of that. Since most women in pregnancy are healthy, they recover and do fine.

But it also explains why anesthesiologists are so concerned when bleeding exceeds the expected. If a patient is losing 700mL/min, we have 8 minutes before she bleeds to death. In those 8 minutes, we have to maintain vital signs, pour in fluid, get additional IV access, administer drugs that can slow the bleeding (oxytocin, methylergonovine, carboprost, and misoprostol), call blood bank and begin transfusions, consider arterial or central access, consider intubation, maintain normothermia, maintain normal coagulation, prevent hypocalcemia, discuss the utility of other surgeons or interventional radiology, and plan for the ultimate disposition of the patient to the ICU. On my rotation, we saw several patients with known high risk for postpartum hemorrhage, and we planned accordingly. But I also had a case of unanticipated maternal hemorrhage, and as you can imagine, keeping up with all those tasks while maintaining a level head is challenging. This is a central issue to obstetric anesthesiology because maternal mortality from hemorrhage should be avoidable, and constant vigilance, practice with simulation, and active teamwork are key to keeping our patients safe.