Obstetric Anesthesia Flashcards
Cardiovascular changes begin when during pregnancy?
As early as the fourth week of pregnancy and continue to the postpartum period
Describe HR changes
HR is increased 20%-30% at term. Begins by first trimester and peaks by 32 weeks gestation
Describe CO changes during pregnancy
- 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
What is autotransfusion?
Autotransfusion happens when the contracting uterus contributes to CO increases
What factors contribute to CO increases as much as 80% immediately after delivery?
- Autotransfusion
- Increased venous return from aortocaval decompression
When does CO gradually return to baseline values?
Gradually returns to baseline within 14 days as HR and SV normalize
A pt. with preexisting cardiac anomalies will be at most risk for decompensation in the _____ period
Immediate postpartum
Physical exam of the preganant patient may appear to ellicit what abnormal findings?
- 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
What cardiovascular findings are considered pathological?
Diastolic murmurs and cardiac enlargement
Greater ____ volume vs ____ volume = dilutional anemia
plasma vs rbc
Endocrine factors that produce cardiovascular changes
- 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)
Normal blood loss for vaginal delivery?
<500 ml
Normal blood loss for uncomplicated c-section?
800-1000 ml
Each contraction moves approx. how many mls of blood from the uterus to central circulation?
300-500mls
What factors result in a 20% decrease in SVR by end of term pregnancy?
Decreased resistance in the uteroplacental, pulmonary, renal and cutaneous vascular beds
What is aortocaval compression?
compression of the aorta and vena cava by the gravid uterus
Aortocaval compression results in
- significant reduction in SV, CO, BP
- decreased uterine blood flow = decreased fetal
oxygenation
Normal physiologic response to aortocaval compression
- tachycardia and vasoconstriction of the lower extremities
Compression of the aorta and vena cava can be relieved how?
- left uterine displacement
- rotation of the OR table 15 degrees to the left or 15cm high wedge under right hip
Maternal hemodynamics are preserved in what positions for neuraxial anesthesia
- Lateral
* no differences in healthy fetal blood flow indices among positions
Due to a hypercoagulable state concentration of factors ___-___ and _____ are increased
VII-IX and fibrinogen
One of the leading causes of maternal mortality
thromboembolic events
