Blood Transfusion in Obstetrics

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The major blood transfusion considerations in obstetrics are shown in Table 24.1. As physiologic preparation for blood loss at the time of delivery, the blood volume of a gravid woman is 60% more than that of a nonpregnant woman resulting in a dilutional anemia. It should be emphasized that patients can tolerate moderate anemia (hematocrit 18-25%, hemoglobin 6-8 g/dl) if normovolemia is maintained. Blood transfusion is an uncommon event in obstetrics. Only 1% of vaginal deliveries require transfusion. However, as many as 18% of patients undergoing cesarean section may require transfusion. Overall obstetrical patients account for 2-4% of all red blood cells transfused in the U.S. (Fig. 4.1).

Early in the prenatal period, a pregnant woman should be evaluated for a family history of bleeding disorders or a history of blood transfusion. Routine laboratory tests should include the hemoglobin/hematocrit, ABO and D type, and antibody screen and screening for hemoglobinopathies in high risk populations.

Immunization to the D antigen in Rh negative mothers is the primary cause of hemolytic disease of the newborn (HDN). Prevention is critical and best performed, using anti-D (RhIg). The clinical indications are shown in Table 24.2. The approach is as follows:

1) Abortion, ectopic pregnancy or abdominal trauma. The Rh antigen is demonstrated as early as 38 days in fetal red blood cells. Treatment is a dose of 50 |ig if the event occurs before 12 weeks, and 300 |ig when it occurs later in pregnancy.

2) Amniocentesis. Amniocentesis performed prior to 20 weeks of gestation can produce fetomaternal bleeding of between 0.5-10 ml. The optimal treatment is the administration of 300 |ig prophylactically when the father is Rh positive, without relying on the Kleihauer-Betke acid elution technique. This dose is adequate until 28 weeks gestation when a subsequent antenatal dose is administered.

3) Hydatidiform mole. The role of anti-D prophylaxis is not established; however using the above guidelines would seem prudent.

4) Late pregnancy. Pregnancy manipulation such as abdominal version and amniocentesis enhances the risk of transplacental hemorrhage. If delivery is to be accomplished within 48 hours of the amniocentesis, the administration of Rh immunoglobulin can be deferred and given only if the infant is found to be Rh D positive.

Otherwise, routine management is as follows:

1) Obtain ABO blood group and Rh (D) type and screen in the first antenatal visit.

2) For Rh (D) negative women at 28 weeks gestation, obtain an indirect Coomb's test (antibody screen); if no Rh antibodies are detected,

Table 24.1. Blood rransfusion considerations in obstetrics

1. Maternal circulation exhibits a dilutional anemia, which is a normal adaptive change. Threshold hemoglobin/Hct for transfusion may be different (Chapter 26).

2. Blood typing (ABO, D) and antibody screening should be performed early in pregnancy.

3. Prophylaxis with Anti-D, if relevant (Chapter 25) for any invasive procedure, abortion or delivery.

4. Severe acute hemorrhage generally occurs in late pregnancy or at delivery. Few patients may actually need transfusion. CMV low risk red cells are essential if transfused in early pregnancy.

5. Predeposit autologous red cells are rarely effective since predictability of bleeding (and hence, transfusion) is difficult in individual patients.

6. Thrombocytopenia may be common (5-7%) and is often mild (80-120 x 109/L). Platelet transfusions are rarely, if ever, indicated.

7. Transfusion of plasma/cryoprecipitate is rare only occurring in the context of acute massive bleeding with dilution or in obstetric-associated disseminated intravascular coagulation.

Table 24.2. Clinical indications for RhIg prophylaxis

Early Pregnancy Late Pregnancy Postpartum

Abortion Fetomaternal hemorrhage Pre- or term deliveries

Ectopic pregnancy Amniocentesis

Hydatidiform molar pregnancy

Amniocentesis

Chorionic villus sampling administer 300 |ig (one dose) of Rh immunoglobulin. This should provide protection for 12 weeks.

3) At delivery: Rh type and direct Coomb's test is performed on the cord blood. If the baby is Rh positive, 300 |ig of Rh immunoglobulin is administered to the mother within 72 hours postpartum. If a large transplacental hemorrhage is suspected, a Kleihauer-Betke stain is done to quantitate the total bleed and 10 |ig of Rh immunoglobulin given for each ml of fetal RBCs. Anti-D preparations are available for intramuscular (Rhogam, Win-Rho) or intravenous use (Win-Rho).

The main indication for elective red cell transfusion is the inherited hemoglo-binopathies, i.e., sickle cell disease, Hb C disease, Hb S/C disease, Hb S/p° thalassemia. Treatment of these disorders with red cell transfusion is to avoid complications such as infection, to control pregnancy-induced hypertension, and to prevent and treat vascular occlusive episodes. The role of transfusion is controversial, and it has been suggested that it should be reserved for obstetric emergencies only. If transfusion is performed, the red cells should be sickle cell negative. Ideally, hemoglobin A is maintained between 20-40%, with a hematocrit in excess of 25.

Leukocyte-reduced RBCs should be transfused, to avoid reactions and prevent CMV transmission (Chapter 36).

Acute blood loss can be a sudden event in obstetrics. The causes are shown in Table 24.3. Depending on the severity (Table 24.4), transfusion may be required. In massive transfusion, (arbitrarily after 10 more units of blood have been transfused), the entire blood volume of the pregnant woman has been replaced. In such rare cases, the patient should be followed by serial assessments of clotting times and platelet counts and replacement with plasma or platelets may be necessary (Chapter 14).

Predeposit autologous blood is sometimes collected from pregnant females. This practice is rarely of benefit to the obstetrical patient since the ability to predict the rare patient needing allogeneic transfusion is difficult (Chapter 3).

Table 24.3. Common causes of obstetrical hemorrhage

In Late Pregnancy Delivery & Postpartum

Abruptio placenta Cesarean delivery

Placenta previa Obstetric laceration

Toxemia associated Uterine atony

Retained placenta Uterine inversion Placenta acreta

Table 24.4. Classification of acute blood loss in obstetrics

Grade

Approximate

Approximate

Signs, Symptoms

Volume of

Percentage Loss

& Treatment

Acute blood loss

of Blood Volume

1

600-1200 ml

10-20

Minimal tachycardia. Saline replacement adequate.

2

1200-1800

20-25

Increased pulse rate, elevated respiratory rate, orthostatic blood pressure change, narrowing of pulse pressure. May require blood transfusion but can be stabilized with crystalloids.

3

1800-2400

30-40

Reduction in systolic blood pressure, significant tachycardia and tachypnea. Blood transfusion is usually needed.

4

> 2400

> 40

Profound shock with no discernable blood pressure. The patient has oliguria or anuria. Blood transfusion is mandatory.

Thrombocytopenia in pregnancy is not uncommon. The causes are shown in Table 24.5. Platelet transfusions are rarely given—the only exception being severe DIC associated with amniotic fluid embolism, fetal death, or abruptio placentae. If Rhesus positive platelets are given to a Rhesus negative female, anti-D (RhIg) should be administered (50-300 pig). The platelets should be leukoreduced, preferably prestorage (Chapter 36) to avoid reactions and prevent CMV transmission.

The only common hereditary bleeding disorder in females is von Willebrand's disease. However, because of changes in coagulation factors and von Willebrand factor in pregnancy, both pregnancy and delivery are rarely complicated by bleeding. Where concern exists, DDAVP may be used, after presentation of the shoulder or the baby has been delivered by cesarean section (Chapter 21), unless con-traindicated by an uncommon subtype of von Willebrand's disease, such as type 2b.

Table24.5. Causes of Thrombocytopenia

1. Incidental Thrombocytopenia:

5-7% of all pregnancies; mild thrombocytopenia in the range of 80-120 x 109/L No known increase in maternal or fetal morbidity or mortality. Does not change obstetrical management.

2. Hypertension Associated: Remits with early delivery.

3. Immune Thrombocytopenic Purpura: Uncommon. Thrombocytopenia, may be <20 x 109/L. Best treated with IVGG, if necessary.

4. Miscellaneous (rare):

HELLP - Hemolytic anemia with elevated liver enzymes in pregnancy. TTP - Thrombotic thrombocytopenia purpura. DIC - Disseminated intravascular coagulation.

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  • saara
    Who guidelines of blood transfusion in obstretics?
    4 years ago

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