Shiu-Ki Rocky Hui
Massive transfusion is defined as:
Traditional definition: Transfusion of ≥10 units of red blood cells (RBCs) within 24 hours.
This is useful for retrospective review and management but not practical for ongoing bleeding.
Practical definition: Transfusion of >4 units of RBC within 1 hour with ongoing need for blood components
Or: Replacement of >50% of total blood volume within 3 hours (1)
However, in obstetric settings, blood loss may be unpredictable, sudden, and severe. A patient can lose a significant portion of her blood volume in a matter of minutes, and symptoms of hypovolemia may not present until 25% of blood volume (1.5 L in term pregnancies) is lost (2). Therefore, the standard definition for massive transfusion may not be adequate in identifying patients at risk for, or in need of, massive transfusion in this setting. Recognition of postpartum hemorrhage, before deterioration in vital signs, is crucial to improve maternal morbidity and mortality (3).
The risk for massive transfusion is, as expected, highest around the time of delivery and is especially prevalent in the postpartum period. In fact, postpartum hemorrhage continues to be a leading cause of maternal mortality in the United States (3).
The various causes of postpartum hemorrhage have been well described in previous chapters but can be briefly categorized as follows:
Abnormalities of contraction: Uterine atony, fibroids, overdistension, and inversion
Trauma: Episiotomy, laceration(s), uterine rupture
Retained placental tissue or placenta accreta spectrum
Coagulopathy: Acquired or congenital
Acquired coagulopathy: Disseminated intravascular coagulation (DIC), preeclampsia, dilutional coagulopathy, anticoagulation, gestational thrombocytopenia, idiopathic thrombocytopenia, antiplatelet therapy
Congenital coagulopathy: von Willebrand disease, hemophilia carrier, congenital platelet function defects
Identified risk factors for massive transfusion include the following:
Maternal risk factors: Age ≥40 years, previous cesarean section
Pregnancy complications: Multiple pregnancy, placenta previa/placenta accreta spectrum, preeclampsia/placental abruption
Delivery complications: Uterine atony, uterine rupture, and cesarean section (4)
Women with abnormal placentation are reported to have the highest risk for massive transfusion (4).
Owing to the increase in blood volume during pregnancy, using hemoglobin or hematocrit as a sole maker to assess acute
obstetric blood loss is likely inadequate; therefore, careful monitoring for clinical signs and symptoms of anemia is essential.
A normal adult can tolerate a 10% to 15% acute loss in blood volume. However, once blood loss is >40%, physiologic changes can be observed and measured. In obstetric settings, acute blood loss can be devastating to fetal well-being. In addition, a pregnant patient’s lungs, kidneys, and anterior pituitary gland are particularly at risk (5).
Tachycardia and increased stroke volume in response to adrenergic stimuli
Hypertension owing to activation of the renin-angiotensin system resulting in vasoconstriction
Tachypnea to compensate for metabolic acidosis
Once these changes are observed, the need for RBC transfusion is imperative to prevent the patient from developing hypovolemic shock. Owing to the acute and severe nature of obstetric bleeding, the volume of RBCs required to improve physiologic changes is often high.
Traditionally, resuscitation for hypovolemia caused by hemorrhage started with the infusion of crystalloids and RBCs. However, evidence suggests that aggressive “hemostatic” resuscitation, using blood products including plasma and platelets, can lead to improved outcomes in the setting of massive hemorrhage (6). High-volume isolated RBC or excessive crystalloid resuscitation can result in dilutional coagulopathy and/or thrombocytopenia in which the patient’s coagulation proteins and platelets become significantly diluted. Particular attention should be paid to fibrinogen, which is a positive predictor for severe postpartum hemorrhage when levels fall below 200 mg/dL (7).
The combination of dilutional coagulopathy and thrombocytopenia creates additional challenges in achieving adequate hemostasis which in turn necessitate more RBC transfusion.
Unrecognized dilutional coagulopathy and thrombocytopenia will ultimately result in uncontrollable bleeding, which increases morbidity and mortality.
Massive transfusion protocol (MTP) is designed to address events where large-volume transfusions are required. The primary goal is the early administration of blood products. MTPs were designed specifically for trauma settings. However, over time, institutions have developed protocols for other settings including obstetrical hemorrhage. In obstetrical patients, special consideration should be given to address the need for fibrinogen early in resuscitation, in addition to choosing the blood components necessary to prevent and/or correct dilutional coagulopathy and thrombocytopenia. MTPs are designed to issue blood components in predetermined ratios until deactivation or transition to goal-directed resuscitation can be performed.
MTP development for obstetrical patients should involve a multidisciplinary team including obstetrics, anesthesia, transfusion medicine/blood bank, nursing, and surgical personnel.
The physical signs and symptoms for hemorrhagic shock mirror those seen in other clinical settings and may include:
Blue lips and fingernails
Low to no urine output
Confusion or loss of consciousness
Although visual estimation of blood loss has been used in the setting of obstetric hemorrhage, this method of hemorrhage assessment is subjective and can be extremely variable. Blood loss in the setting of massive hemorrhage can be underestimated despite the implementation of visual tools designed to assist in blood loss estimates. Whenever possible, quantitative measurements of blood loss should be performed (8).
Successful quantification of blood loss requires both the use of direct measurements and a protocol for collecting and reporting these data.
Several items have been suggested for assisting in quantification, including the following:
Graduated underbuttocks drapes (vaginal delivery)
Measured suction canisters (cesarean delivery)
Dry weights of all items that may become saturated with blood
Weights of all clots and any items that are saturated with blood
Accurate recording of irrigation fluid volumes (cesarean delivery)
Quantification of blood loss should continue until active bleeding has ceased or for as long as the patient remains unstable after >1 L of hemorrhage (8).
Early tracking of blood loss may allow for quicker recognition of the development of massive hemorrhage.
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