Obstetric Anesthesia

Question 1

Cardiovascular changes begin when during pregnancy?

Answer 1

As early as the fourth week of pregnancy and continue to the postpartum period

Question 2

Describe HR changes

Answer 2

HR is increased 20%-30% at term. Begins by first trimester and peaks by 32 weeks gestation

Question 3

Describe CO changes during pregnancy

Answer 3

• CO is increased by up to 40% non pregnant values
• Begins 5th week and results from an increase in SV
  20%-50%
  -10% will supply the gravid uterus

Question 4

What is autotransfusion?

Answer 4

Autotransfusion happens when the contracting uterus contributes to CO increases

Question 5

What factors contribute to CO increases as much as 80% immediately after delivery?

Answer 5

• Autotransfusion

- Increased venous return from aortocaval decompression

Question 6

When does CO gradually return to baseline values?

Answer 6

Gradually returns to baseline within 14 days as HR and SV normalize

Question 7

A pt. with preexisting cardiac anomalies will be at most risk for decompensation in the _____ period

Answer 7

Immediate postpartum

Question 8

Physical exam of the preganant patient may appear to ellicit what abnormal findings?

Answer 8

• Enlarged cardiac silhouette (diaphragm rises, shifts heart up and to the left)
• Ventricular walls thicken and end-diastolic volume increases
• Benign grade 1 or 2 systolic murmur
• 3rd heart sound
• Exercise intolerance, SOB, edema

Question 9

What cardiovascular findings are considered pathological?

Answer 9

Diastolic murmurs and cardiac enlargement

Question 10

Greater ____ volume vs ____ volume = dilutional anemia

Answer 10

plasma vs rbc

Question 11

Endocrine factors that produce cardiovascular changes

Answer 11

• Circulating levels of progesterone and estrogen result in enhanced RAAS activity = increased plasma volume
• Increased erythropoietin levels = increased RBC volume (happens after 8th week of gestation)

Question 12

Normal blood loss for vaginal delivery?

Answer 12

<500 ml

Question 13

Normal blood loss for uncomplicated c-section?

Answer 13

800-1000 ml

Question 14

Each contraction moves approx. how many mls of blood from the uterus to central circulation?

Answer 14

300-500mls

Question 15

What factors result in a 20% decrease in SVR by end of term pregnancy?

Answer 15

Decreased resistance in the uteroplacental, pulmonary, renal and cutaneous vascular beds

Question 16

What is aortocaval compression?

Answer 16

compression of the aorta and vena cava by the gravid uterus

Question 17

Aortocaval compression results in

Answer 17

• significant reduction in SV, CO, BP
• decreased uterine blood flow = decreased fetal
  oxygenation

Question 18

Normal physiologic response to aortocaval compression

Answer 18

• tachycardia and vasoconstriction of the lower extremities

Question 19

Compression of the aorta and vena cava can be relieved how?

Answer 19

• left uterine displacement

- rotation of the OR table 15 degrees to the left or 15cm high wedge under right hip

Question 20

Maternal hemodynamics are preserved in what positions for neuraxial anesthesia

Answer 20

• Lateral

* no differences in healthy fetal blood flow indices among positions

Question 21

Due to a hypercoagulable state concentration of factors ___-___ and _____ are increased

Answer 21

VII-IX and fibrinogen

Question 22

One of the leading causes of maternal mortality

Answer 22

thromboembolic events