Physiology

Question 1

MAC during pregnancy

Answer 1

decreases by 40%, returns to normal by 3-4 day postpartum

Question 2

Sensitivity to local anesthesitcs?

Answer 2

Increased sensitivity to local anesthetics during pregnancy (30%)

Question 3

epidural blood volume?

Answer 3

Obstructing IVC –> enlarges epidural venous plexus –> increases epidural blood volume –> more uptake of epidural anesthetics

Question 4

CSF volume?

Answer 4

lower CSF due to increased girth in abdomen –> pushes CSF cephalad as well as epidural fluid –> more spread with injection

Question 5

Oxygen consumption?

Answer 5

increased oxygen consumption in pregnancy –> 20% of CO goes to uterus and fetus that are very metabolically active

Question 6

Minute ventilation

Answer 6

Large increase in minute ventilation –> respiratory alkalosis during pregnancy

Question 7

Respiratory mechanics during pregnancy

Answer 7

Elevated diaphragm, increased AP chest diameter, Vt and RR increased

Question 8

Rapid desaturation?

Answer 8

Decreased FRC + increased O2 consumption

Question 9

Inhalational induction during pregnancy?

Answer 9

Accelerated due to increased MV and lower MAC

Question 10

Airway during pregnancy

Answer 10

Treat all as difficult and full stomach!

• rapid desaturation
• edema from fluid retention
• friable tissue due to capillary engorgement
• full-stomach (RSI)

Question 11

Hgb-O2 dissociation curve

Answer 11

• Alkalosis shifts to left

- 2,3-DPG shifts back right

Question 12

Anemia during pregnancy?

Answer 12

dilutional anemia due to increased plasma circulating volume (55%)
- reduced blood viscosity as well

Question 13

Estimated blood volume

Answer 13

in pregnancy it increased 90 cc/kg

Question 14

DO2 during pregnancy?

Answer 14

reduction in Hgb is offset by the increase in CO

Question 15

BP in pregnancy?

Answer 15

reduced SVR so normotensive

Question 16

increased CO?

Answer 16

due to HR and SV increases

• greatest increase is immediately after delivery (autotransfusion)
• CO should return to normal in 2 weeks postpartum

Question 17

Aortocaval compression?

Answer 17

supine hypotension syndrome

• can also see bradycardia
• enlarged uterus compresses IVC and aorta –> SOB and edema

Question 18

Heart changes due to increased blood volume

Answer 18

• Stretching of ventricles –> common regurgitant lesions
• S3 heart sound
• accentuated S2 heart sound
• systolic ejection murmur
• slight cardiomegaly

Question 19

GFR in pregnancy?

Answer 19

GFR increases thus making BUN and Cr lower!

- a Cr of 1 is abnormal in pregnancy!

Question 20

Full stomach precautions?

Answer 20

cephalad displacement of stomach due to uterus = promotes LES incompetence
- progesterone contributes!

Question 21

Hepatic changes

Answer 21

liver flow unchanged, slight elevation in ALK

- decreased pseudocholinesterase

Question 22

Coagulation state

Answer 22

pregnancy is HYPERcoagulable state

Question 23

Increased coagulant factors

Answer 23

• Factors VII, VIII, IX, X, XII

- Fibrinogen

Question 24

Decreased coagulant factors

Answer 24

• Factor XI

- Platelets

Question 25

Metabolic state

Answer 25

- diabetogenic state = high FFA, ketones, TGA | - hPL creates insulin resistance

Question 26

CO immediately postpartum

Answer 26

Drastic increases in CO immediately postpartum --> venous constriction due to sympathetic surge and contraction of the uterus (venous reservoir)

Question 27

when does aortocaval compression start?

Answer 27

around 20th week gestation

Question 28

Difficult airway in pregnancy?

Answer 28

``` 10x more common to have a failed intubation - can have changes in mallampati class during course ```

Question 29

ACid base during pregnancy

Answer 29

Increased RR --> resp alkalosis | - renal compensation by HCO3 excretion

Question 30

Succinylcholine metabolism

Answer 30

plasma cholinesterase activity decreased by 25% --> back to normal 2-6 week postpartum *not clinically relevant*

Question 31

Gastric emptying during pregnancy

Answer 31

gastric emptying doesn't change --> but decreases during active labor