Postpartum hemorrhage is one of the most common emergencies faced by obstetricians. Not only is it a leading cause of maternal morbidity, but it remains one of the top three causes of maternal mortality throughout the world.1,2 In order to manage postpartum hemorrhage effectively, the obstetrician must have a thorough understanding of normal delivery-related blood loss, physiologic responses to hemorrhage, the most common etiologies of postpartum hemorrhage, and appropriate therapeutic interventions.
Normal delivery-related blood loss depends on delivery mode. The average blood loss for a vaginal delivery, cesarean delivery, and cesarean hysterectomy has been estimated at 500, 1000, and 1500 mL, respectively.3,4, 5 These values are often underestimated and unappreciated clinically due to the significant blood volume expansion that accompanies pregnancy.
Postpartum hemorrhage has been defined in published literature.4,5, 6 Definitions have included subjective assessments greater than the standard norms, a 10% decline in hematocrit, and need for blood transfusion. Because of these varied definitions, the exact incidence of postpartum hemorrhage is difficult to determine; however, rough estimates suggest that postpartum hemorrhage complicates 1% to 5% of all deliveries.7 For practical purposes, postpartum hemorrhage is best defined as excessive bleeding that causes the patient to be hemodynamically symptomatic.
PHYSIOLOGIC RESPONSE TO HEMORRHAGE
The pregnant patient is able to adapt to hemorrhage more effectively than her nonpregnant counterpart due to hemodynamic changes that accompany pregnancy. These changes include increased red cell mass, increased plasma volume, and increased cardiac output. In the early phases of hemorrhage, the body compensates by raising systemic vascular resistance in order to maintain blood pressure and perfusion to vital organs. However, as bleeding continues, further vasoconstriction is impossible resulting in drops in blood pressure, cardiac output, and end-organ perfusion.3,8 Table 3-1 classifies the physiologic responses that occur with various stages of hemorrhage. It is important for the obstetrician to recognize these responses since the quantity of blood loss that occurs during a postpartum hemorrhage is often underestimated as stated previously.
TABLE 3-1.Hemorrhage Classification and Physiologic Response ||Download (.pdf) TABLE 3-1. Hemorrhage Classification and Physiologic Response
|Hemorrhage class ||Acute blood loss ||% Lost ||Physiologic response |
|1 ||1000 mL ||15 ||Dizziness, palpitations, minimal blood pressure change |
|2 ||1500 mL ||20-25 ||Tachycardia, tachypnea, sweating, weakness, narrowed pulse pressure |
|3 ||2000 mL ||30-35 ||Significant tachycardia and tachypnea, restlessness, pallor, cool extremities, hypotension |
|4 ||≥2500 mL ||40 ||Cardiogenic shock, air hunger, oliguria or anuria |
ETIOLOGIES OF POSTPARTUM HEMORRHAGE
The etiologies of postpartum hemorrhage can be categorized as primary—those occurring within 24 hours of delivery—and secondary—those occurring from 24 hours until 6 weeks after delivery.9 Table 3-2 lists the ...