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21 Cards in this Set

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How much does blood volume increase during pregnancy/
Approx 45% increase as a result of increases in plasma volume and RBC mass
Why does a pregnant woman increase blood volume?
Required to fill the increased total intravascular capacity caused by:
-- increased venous diameter
-- uteroplacental vasculature
-- expansion in arterial capacity due to vasorelaxation
How does plasma volume change during pregnancy?
Approx 50% increase
-- about 1200mL at term in normal gestations
-- greater increase if multiple births (1800 if twins, 2300 if triplets)
When does plasma volume increase?
Occurs very early in pregnancy, as opposed to RBC mass, which is delayed until after mid-gestation
Pregnancy and total body water?
Gradual increase in sodium adds a total of 500-900mEq by the end of pregnancy
-- total body water increase ranges from 6-8L
-- 4-6L is extracellular

Fall in vascular resistance and increased venous dilatation occur early
-- resultant fall in pressure may induce water retention
How is K loss prevented if pregnant women retain more sodium?
Progesterone blocks the action of aldosterone on the renal tubule to keep K levels normal in pregnant women
Are serum Na levels higher in pregnant women?
No.

Serum Na levels are unchanged due to obligatory water retention
When does the increase in RBC mass occur? Why? How much does it increase?
Mid-gestation due to increase in erythropoietin levels
-- erythropoietin secretion is dependent on tissue oxygenation which is maintained at normal levels until approx mid-gestation

Increases about 30%
Explain "physiologic hemodilutional anemia" of pregnancy.
Increase in RBC mass is delayed compared to the increase in plasma volume
What causes an increased need for iron in pregnant women?
Increased RBC mass

Iron to fetus (300-400mg), placenta (570mg), and breast milk (100-150mg)
What is the daily iron requirement for a pregnant woman, and why?
Iron saving due to no menstruation
-- 240-280mg

Net iron need: 700-1400mg

Divide net need by duration of pregnancy for daily requirement of about 18mg

Diet provides about 12-14mg

Supplement w/ 4-6mg daily

Women w/ iron deficiency need even greater supplementation
How do coag factors change during pregnancy?
Increase in:
-- VII
-- VIII
-- X
-- plasma fibrinogen (marked increase)

Changes appear to be due primarily to increased hepatic synth under influence of steroids, partic estrogen
Pregnant vs. non-pregnant values of fibrinogen?
Taking into account increased plasma volume, fibrinogen in pregnancy at leas doubles over non-pregnant values
Pregnant vs. non-pregnant coagulation activity?
Increaes in factor VIII, increases the coag activity to twice the non-pregnant level
-- may be parallel increase in factor VIII Ag
Fibrinolysis in pregnancy?
Incresed large fibrin degradation products (FDP) appear to be result of active fibrinolysis in uteroplacental vessles
-- local increase is necessary to remove fibrin deposits created by slower, turbulent flow in the dilated, tortuous uteroplacental vessels

Also an increse in release of the large FDP from the uterus during labor

Despite this, the plasma fibrinolytic activity is SUPPRESSED during normal pregnancy

Increased fibrinogen and coag factors and decrease in plasma fibrinolytic activity offer advantage of hypercoagulability to pregnant women in the event of placenta separation.
Screening and prevention of anemia?
Physiologic hemodilution anemia of pregnancy is maximal at 28-32wks gestation
-- measure Hct at 28wks to give highest sensitivity for anemia dx
-- leaves adequate time for correction of the anemia prior to term

All pregnant women screened early since anemia is common

Supplemental iron routinely prescribed for prevention to help increase RBC mass
Anemia Dx in pregnant women -- RBC count, Hb, Hct, MCV, and MCHC?
RBC count falls from 4.2mil in early pregnancy to 3.8mil in last trimester
-- HCT falls in parallel from 40-41% to 31-34%

Lowest levels occur at 32wks gestation

Reduction is less taking iron supplements

Hb levels less than 11gm/dL and Hct less than 33% are considered indicative of anemia in pregnancy

Changes in MCV are small, and there are no changes in MCHC during pregnancy, so
-- these indices are valid for anemia dx at same levels as in non-pregnant state
Anemia Dx in pregnant women -- Serum Fe, Transferrin, TIBC, and Ferritin?
Serum Fe levels:
-- range from 60-150
-- INCREASED in non-pregnant women w/ iron deficiency
-- falls to 35% below non-pregnant mean in pregnant woman

Transferrin
-- ranges from 120-200
-- rises in pregnancy to 470

TIBC
-- usually 1/3 saturated w/ iron in non-anemic subjects

Serum Fe, even in combo w/ TIBC is NOT a reliable indicator of iron stores in pregnancy

Ferritin
-- 15-300 in the plasma and does not fluctuate
-- RELIABLE, stable measure of iron stores, especially in the lower range in iron deficiency anemia
What contributes to venous stasis in pregnancy?
1. venous smooth muscle dilation due to estrogen

2. growing uterus may compress soft-walled external iliac veins in the pelvis

3. decreased activity during labor and delivery and immediate postpartum period

**DVT and assoc complications of pulmonary embolism seriously increase risks of childbearing
What are the most compelling activators of blood coagulation during pregnancy?
1. increased level fibrinopeptide A (cleaved from fibrinogen by thrombin)

2. increased circulating fibrin monomers
How do we reduce risk of thromboembolism from pregnancy?
1. early postpartum ambulation and avoidance of immobilization

2. heparin prophylaxis used in women w/ predisposition and those w/ past hx of pregnancy-related events
-- higher doses may be needed due to heparin degradation

3. Dx and Tx is similar to in non-pregnant state
-- AVOID warfarin due to risk of teratogenesis