Anesthesia For OB Flashcards
What is the ultimate goal
Perfusion of uterus
Obesity in pregnancy
50% are overweight
Obesity increases advers effects and rate of c-sections
Respiratory changes
- Thoracic cage circumference increases 5-7 cm, inc in AP diameter
- Relaxin, relaxation of ligamentous attachments of the ribs
- Elevation of the diaphragm
Lung volumes changes and capacities
- VT increase
- RV decrease: diaphragm pushes up the chest
- ERV decrease
- FRC decrease by 80% due to elevation of the diaphgram (ERV/RV)
- Elevated closing volumes
What happens in supine position
Exaggerates the effects
-FRC 70% of pp volume
Respiratory changes
MV
Alveolar ventilation
MV increase ( inc Vt and CO2 production) Alveolar ventilation increases ( alkalosis )
Heart during pregnancy
Leftward, may appear enlarged on X-ray
Grade I, II systolic murmurs due to inc blood flow across valves
Inc HR, so decrease or no change in BP
Maternal blood flow
- Second trimester: max rate of incr, slower in third
- 35-40% expansion (1L-1.5L) much of this perfuses the gravid uterus
- EBL 500-1000 L
- RBC mass inc but at slower rate than plasma (relative anemia of preg)
Autotransfusion
- around 500 cc
- immediately after delivery
- decrease in vascular space by same volume
Cardiac output in each trimester
1st trimester: 40% inc
2nd trimester: slight incr
Cardiac output during labor
15% latent phase
30% active phase
45% expulsion phase
Each contraction increases CO 10-20%
Blood pressure
- No changes
- Increase renal, uterine and extremity blood flow
- coload vs preload for SAB
Body wt and composition
17% = 12 kg Uterus 1kg Amniotic fluid 1kg Fetus and placenta 4kg Blood volume and interstitial fluid 4kg Fat and protein 4 kg
Aortocaval compression
Hypotension, diaphoresis, palor due to obstructed IVC in the supine position- 20th week
What is the effect of vasodilation drugs on aortocaval compression?
Drugs will increase symptoms
How does blood returns to heart during aortocaval compression
Via the epidural veins and azygos system
What are some effects of aortic compression
Who does it effect
- Partially occluded aorta when supine: HoTn in LE, uterine arteries
- decreases intervillious blood flow by 20%, dec fetal PaO2
What can cause fetal asphyxia, distress
Aortic compression
What is uterine blood flow related to
Perfusion pressure
UPP = UA - UV
What is the quick treatment for decrease uterine blood flow
Manually displace uterus 15 degrees
Turn pt to left side
10% RUD is more effective
What coag factors and when are increased - hemodynamic changes
Factors 7,8,10 fibrinogen, leukocytes
Increased after 3 month
Leads to increase incidence of DVT, PE
Gestational thrombocytopenia
relative anemia of pregnancy
Why
RBC mass increases slower than plasma
Delusional effect
GA prego
- MAC decrease 40%, less anesthetic
- Progesterone level increase 10-20 times
- Beta endorphins increase during labor
Regional anesthesia for prego
- Swollen epidural veins= high risk for IV injection
- Soft LF= lost of resistance best for epidural
- Neuro sensitivity to LA: hormonal and acid/base changes
- 30-50% dose decrease in LA, 1/3 reduction or more
- Lordosis: decr CSF specific gravity may enhance cephalad spread
- higher risk for high spinal, decrease flow to caudal - narrowing
