Lecture 1 - Obstetric Anesthesia

Question 1

What physiological changes occur during pregnancy?

Answer 1

• Neurological
• Respiratory
• Cardiac
• Hematological
• Renal
• Gastrointestinal

Question 2

What are the neurological changes in pregnancy?

Answer 2

• MAC is decreased
• Epidural space becomes smaller
• Cerebrospinal fluid volumes are decreased
• Epidural veins are engorged
• Increase to sensitivity to local anesthetics

Question 3

What are the respiratory increases during pregnancy?

Answer 3

• Tidal volume increased ~40% at term
• RR increases ~15%
• Minute ventilation increased ~ 50 %

Question 4

T/F: During pregnancy compensatory metabolic acidosis takes place by excretion of bicarbonate.

Answer 4

TRUE (This is due to the respiratory alkalosis that occurs from pregnancy)

Question 5

PaCO2 decreased to ________ mmHg secondary to hyperventilation creating respiratory _______..

Answer 5

28-32

alkalosis

Question 6

How does the body correct for respiratory alkalosis?

Answer 6

Excretion of bicarbonate maintains normal pH.

Question 7

What What are the respiratory changes that decrease during pregnancy?

Answer 7

• FRC decreases by ~ 20%
• Expanding uterus displaces diaphragm cephalad
• Decrease dead space
• Slight decrease in airway resistance

Question 8

Decreased FRC, coupled with increased maternal oxygen _________, can rapidly lead to materna ______ during indction of general anesthesia

Answer 8

• consumption

- hypoxia

Question 9

T/F: Preoxygenation is NOT mandatory prior to anesthesia induction.

Answer 9

FALSE

Question 10

P50 of hemoglobin increases from 27 to __ mmHG.

Answer 10

30

Question 11

Why does P50 change during pregnancy?

Answer 11

Aids in oxygen delivery to fetus

Question 12

What will hyperventilation do during pregnancy?

Answer 12

• Decrease PaCO2
• Uterine vasoconstriction
• decrease placental blood flow
• Oxygenhemoglobin curve will shift to the left

Question 13

Why would you use a small ETT and avoid nasal intubation of instrumentation of an OB patient?

Answer 13

Mucosal venous engorgement/edema

Question 14

The pregnant patient has an increased plasma and red cell mass by how much?

Answer 14

~ 45 % plasma

~ 20% RBC

Question 15

How much does the cardiac output increase?

Answer 15

40%

Question 16

How much does heart rate increase?

Answer 16

15-30 %

Question 17

How much does stroke volume increase?

Answer 17

30 %

Question 18

Progesterone _______ venous smooth muscle causing a decrease in the __________ vascular resistance of __%.

Answer 18

• increases
• peripheral
• 15

Question 19

Cardiac output changes during labor. Name the phase and the elevation of CO in percentage.

Answer 19

Latent phase - 15%
Active Phase - 30%
Second Stage - 45%
Postpartum - 80%

Question 20

T/F: The OB patient’s response to adrenergic drugs is blunted.

Answer 20

TRUE

Question 21

T/F: Cardiac atrophy can be seen on CXR in the OB patient.

Answer 21

FASLE (Cardiac HYPERTROPY …..)

Question 22

T/F: There is a increase in plasma colloid osmotic pressure.

Answer 22

FALSE (DECLINE in plasma colloid….)

Question 23

Give the description of Supine Hypotension Syndrome. (aortocaval compression)

Answer 23

~ 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

Question 24

What are the hematological changes in the OB patient.

Answer 24

• Depressed cell mediated immunity
• Hypercoagulable state (Increased risk for pulmonary embolism)
• PT decreases 20 %
• PTT decrease 20 %

Question 25

What coag factors increase in the OB patient?

Answer 25

``` I VII VIII IX X XII ```

Question 26

What coagulation factors decrease in the OB patient?

Answer 26

XI | XIII

Question 27

What coagulation factors are unchanged in the OB patient?

Answer 27

II | V

Question 28

What renal changes are seen in OB patients?

Answer 28

- Increase in renal blood flow - Serum BUN and creatinine are MILD decreased - MILD glycosuria and proteinuria are common

Question 29

Renal blood flow and glomerularfiltration increased by about ____ % by __th week and remain elevated until delivery.

Answer 29

50 | 16

Question 30

T/F: Competence of gastroesophageal sphincter is reduced during pregnancy.

Answer 30

TRUE

Question 31

What decreases gastroesophageal sphincter tone?

Answer 31

Progesterone

Question 32

Placental gastrin secretion ______ acid scretion.

Answer 32

increases

Question 33

There is a 20% _________ in pseudocholinesterase levels but the ________ in volume of distribution counters any clinically significant __________ of NMB with succinylcholine.

Answer 33

Decrease Increase Prolongation

Question 34

What are the different methods of agents transferring across the placenta?

Answer 34

- Diffusion - Bulk Flow - Active Transport - Pinocytosis - Breaks

Question 35

Fetal stores are __mL of O2 and consumption is __ mL/min.

Answer 35

42 | 21

Question 36

How long can a full term fetus survive without oxygenation?

Answer 36

10 minutes

Question 37

Describe the partial pressure of placental blood flow and how does fetus and mother circumvent this.

Answer 37

- 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

Question 38

T/F: Transfer of CO2 occurs by active transport of across the plecenta.

Answer 38

FALSE (....CO2 occurs by simple diffusion...)

Question 39

How much CO is directed toward the uterus in the parturient?

Answer 39

10% (about 600-700cc)

Question 40

How much CO is directed toward the uterus in a non pregnant woman?

Answer 40

50 CC

Question 41

Of uterine blood flow how much goes to the placenta and how much to the myometrium?

Answer 41

80% placenta | 20 % myometrium

Question 42

What are three factors that influence uterine blood flow?

Answer 42

- Systemic blood pressure - Uterine vasoconstriction - Uterine contraction

Question 43

T/F: Propofol and thiopental mildly reduce UBF via maternal hypotension.

Answer 43

True

Question 44

T/F: Ketamine has no net effect at doses < 1.5 mg/kg on the UBF.

Answer 44

TRUE

Question 45

T/F: Volatile agents increase UBF secondary to hypotension but at < 1 MAC the effect is minor.

Answer 45

FALSE (Volatile agents DECREASE UBF...)

Question 46

T/F: Nitrous oxide has negligible effects on UBF.

Answer 46

TRUE

Question 47

T/F: Opioids have major effect of UBF causing vasoconstriction.

Answer 47

FALSE (Opioids have little effect on UBF)

Question 48

T/F: Low serum local anesthetic levels can result in uterine vasoconstriction.

Answer 48

FALSE (HIGH serum local.....)

Question 49

Uterine blood flow may ______ With neuraxial analgesia as a ______ in maternal catechol levels _____ vasoconstriction, as long as _______ blood pressure is maintained.

Answer 49

Improve reduction reduces normal

Question 50

T/F: Increased oxygen tension closes the DUCTUS.

Answer 50

TRUE

Question 51

What two factors will cause a R to L shunt through the ductus.

Answer 51

- Hypoxia | - Acidosis

Question 52

What occurs during 1st stage of labor?

Answer 52

Onset of true labor until complete cervical dilatation.

Question 53

What occurs during latent phase of labor?

Answer 53

minor dilation 2-4 cm | infrequent contraction

Question 54

What occurs during active phase of labor?

Answer 54

``` progressive dilation to 10 cm a regular contraction (3 - 5 min) ```

Question 55

What occurs during 2nd stage of labor?

Answer 55

Time from complete dilation until infant delivered.

Question 56

What occurs during 3rd stage of labor?

Answer 56

Time from delivery of infant until placenta delivered.