Lecture 1 - Obstetric Anesthesia Flashcards
What physiological changes occur during pregnancy?
- Neurological
- Respiratory
- Cardiac
- Hematological
- Renal
- Gastrointestinal
What are the neurological changes in pregnancy?
- MAC is decreased
- Epidural space becomes smaller
- Cerebrospinal fluid volumes are decreased
- Epidural veins are engorged
- Increase to sensitivity to local anesthetics
What are the respiratory increases during pregnancy?
- Tidal volume increased ~40% at term
- RR increases ~15%
- Minute ventilation increased ~ 50 %
T/F: During pregnancy compensatory metabolic acidosis takes place by excretion of bicarbonate.
TRUE (This is due to the respiratory alkalosis that occurs from pregnancy)
PaCO2 decreased to ________ mmHg secondary to hyperventilation creating respiratory _______..
28-32
alkalosis
How does the body correct for respiratory alkalosis?
Excretion of bicarbonate maintains normal pH.
What What are the respiratory changes that decrease during pregnancy?
- FRC decreases by ~ 20%
- Expanding uterus displaces diaphragm cephalad
- Decrease dead space
- Slight decrease in airway resistance
Decreased FRC, coupled with increased maternal oxygen _________, can rapidly lead to materna ______ during indction of general anesthesia
- consumption
- hypoxia
T/F: Preoxygenation is NOT mandatory prior to anesthesia induction.
FALSE
P50 of hemoglobin increases from 27 to __ mmHG.
30
Why does P50 change during pregnancy?
Aids in oxygen delivery to fetus
What will hyperventilation do during pregnancy?
- Decrease PaCO2
- Uterine vasoconstriction
- decrease placental blood flow
- Oxygenhemoglobin curve will shift to the left
Why would you use a small ETT and avoid nasal intubation of instrumentation of an OB patient?
Mucosal venous engorgement/edema
The pregnant patient has an increased plasma and red cell mass by how much?
~ 45 % plasma
~ 20% RBC
How much does the cardiac output increase?
40%
How much does heart rate increase?
15-30 %
How much does stroke volume increase?
30 %
Progesterone _______ venous smooth muscle causing a decrease in the __________ vascular resistance of __%.
- increases
- peripheral
- 15
Cardiac output changes during labor. Name the phase and the elevation of CO in percentage.
Latent phase - 15%
Active Phase - 30%
Second Stage - 45%
Postpartum - 80%
T/F: The OB patient’s response to adrenergic drugs is blunted.
TRUE
T/F: Cardiac atrophy can be seen on CXR in the OB patient.
FASLE (Cardiac HYPERTROPY …..)
T/F: There is a increase in plasma colloid osmotic pressure.
FALSE (DECLINE in plasma colloid….)
Give the description of Supine Hypotension Syndrome. (aortocaval compression)
~ 20% of term parturient will develop hypotension, pallor nausea and vomiting and diaphoresis when they lie flat
- May be seen as early as 20 weeks gestation
- Lateral uterine tilt position is best used
What are the hematological changes in the OB patient.
- Depressed cell mediated immunity
- Hypercoagulable state (Increased risk for pulmonary embolism)
- PT decreases 20 %
- PTT decrease 20 %
What coag factors increase in the OB patient?
I VII VIII IX X XII
What coagulation factors decrease in the OB patient?
XI
XIII
What coagulation factors are unchanged in the OB patient?
II
V
What renal changes are seen in OB patients?
- Increase in renal blood flow
- Serum BUN and creatinine are MILD decreased
- MILD glycosuria and proteinuria are common
Renal blood flow and glomerularfiltration increased by about ____ % by __th week and remain elevated until delivery.
50
16
T/F: Competence of gastroesophageal sphincter is reduced during pregnancy.
TRUE
What decreases gastroesophageal sphincter tone?
Progesterone
Placental gastrin secretion ______ acid scretion.
increases
There is a 20% _________ in pseudocholinesterase levels but the ________ in volume of distribution counters any clinically significant __________ of NMB with succinylcholine.
Decrease
Increase
Prolongation
What are the different methods of agents transferring across the placenta?
- Diffusion
- Bulk Flow
- Active Transport
- Pinocytosis
- Breaks
Fetal stores are __mL of O2 and consumption is __ mL/min.
42
21
How long can a full term fetus survive without oxygenation?
10 minutes
Describe the partial pressure of placental blood flow and how does fetus and mother circumvent this.
- Placental Blood Flow is 40 mmHg PaO2
- Fetal oxyhemoglobin dissociation curve is left shifted and mother curve is right shifted
- Fetal hemoglobin is higher than mother’s
T/F: Transfer of CO2 occurs by active transport of across the plecenta.
FALSE (….CO2 occurs by simple diffusion…)
How much CO is directed toward the uterus in the parturient?
10% (about 600-700cc)
How much CO is directed toward the uterus in a non pregnant woman?
50 CC
Of uterine blood flow how much goes to the placenta and how much to the myometrium?
80% placenta
20 % myometrium
What are three factors that influence uterine blood flow?
- Systemic blood pressure
- Uterine vasoconstriction
- Uterine contraction
T/F: Propofol and thiopental mildly reduce UBF via maternal hypotension.
True
T/F: Ketamine has no net effect at doses < 1.5 mg/kg on the UBF.
TRUE
T/F: Volatile agents increase UBF secondary to hypotension but at < 1 MAC the effect is minor.
FALSE (Volatile agents DECREASE UBF…)
T/F: Nitrous oxide has negligible effects on UBF.
TRUE
T/F: Opioids have major effect of UBF causing vasoconstriction.
FALSE (Opioids have little effect on UBF)
T/F: Low serum local anesthetic levels can result in uterine vasoconstriction.
FALSE (HIGH serum local…..)
Uterine blood flow may ______ With neuraxial analgesia as a ______ in maternal catechol levels _____ vasoconstriction, as long as _______ blood pressure is maintained.
Improve
reduction
reduces
normal
T/F: Increased oxygen tension closes the DUCTUS.
TRUE
What two factors will cause a R to L shunt through the ductus.
- Hypoxia
- Acidosis
What occurs during 1st stage of labor?
Onset of true labor until complete cervical dilatation.
What occurs during latent phase of labor?
minor dilation 2-4 cm
infrequent contraction
What occurs during active phase of labor?
progressive dilation to 10 cm a regular contraction (3 - 5 min)
What occurs during 2nd stage of labor?
Time from complete dilation until infant delivered.
What occurs during 3rd stage of labor?
Time from delivery of infant until placenta delivered.
