Physiologic Changes During Pregnancy

Question 1

Why does upper airway swelling occur during pregnancy?

Answer 1

Increased progesterone, estrogen and relaxin cause vascular engorgement and hyperemia.

Increased extracellular fluid volume

Question 2

Change in Mallampati score during pregnancy

Answer 2

Increases

Question 3

Risk of difficult/ failed intubation during pregnancy

Answer 3

Increases (up to 8x in full term pts)

Question 4

Change in glottic opening during pregnancy

Answer 4

Narrowed

Question 5

Change in airway equipment for pregnant patients

Answer 5

Short handled laryngoscope (Datta handle)

Downsized ETT (6.0 - 7.0)

Avoid nasal airways

Question 6

How does lung/ diaphragmatic physiology change during pregnancy?

Answer 6

Ribs more horizontal d/t relaxin relaxing the ligaments of the ribcage

AP diameter of chest increases> lungs have more space

As uterus grows, diaphragm moves cephalad

Question 7

How do lung volumes and capacities change during pregnancy?

Answer 7

Decrease in expiratory reserve volume and residual volume = decrease in functional residual capacity

FRC falls below closing capacity= airway closure during tidal breathing

No change in vital capacity and closing capacity

Total lung capacity decreases by 5%

Question 8

How does progesterone affect breathing?

Answer 8

Respiratory stimulant

Question 9

How does OxyHgb dissociation curve change in pregnancy?

Answer 9

Rightward shift (d/t increased P50)

Facilitates transfer to fetus

Question 10

How do ABGs change during pregnancy?

Answer 10

Increased PaO2 (104-108 mmHg) d/t hyperventilation

Decreased PaCO2 (28-32 mmHg)

Decreased HCO3 (20 mmol/L)

No change in pH

Question 11

How does minute ventilation change during pregnancy?

Answer 11

Increased (by 50%)

Vt increases by 40%
RR increases by 10%

Question 12

How does oxygen consumption change in pregnancy?

Answer 12

Increases by 20% at term

Increases by 40% over prelabor value in the first stage of labor

Increases by 75% over prelabor value in the second stage of labor

Question 13

When does cardiac output return to pre-labor values?

Answer 13

24-48 hours

Question 14

When does cardiac output return to pre-pregnancy values?

Answer 14

~ 2 weeks

Question 15

What percentage of cardiac output does the uterus recieve?

Answer 15

10%

Question 16

By what percentage does cardiac output increase during pregnancy?

Answer 16

40%

Question 17

How does SVR change during pregnancy?

Answer 17

Decreased d/t progesterone

Question 18

Why does the MAP not change during pregnancy?

Answer 18

There is an increased blood volume but decreased SVR/ DBP = no net effect on MAP

Question 19

By what mechanism does progesterone decrease SVR and PVR?

Answer 19

Increasing nitric oxide > vasodilation

Decreasing response to angiotensin and norepinephrine

Question 20

How does pregnancy affect filling pressures?

Answer 20

There is no change in filling pressures in pregnancy until uterine contraction occurs > autotransfusion occurs > filling pressures increase

Question 21

How does cardiac axis deviation change during pregnancy?

Answer 21

Diaphragm pushes cephalad > heart is pushed up and to the left > L axis deviation

Question 22

What is the pathophysiology of aortocaval compression syndrome?

Answer 22

The gravid uterus compresses the vena cava and the aorta > decreased blood flow to the heart/ extremities/ uterus > fetal perfusion compromised/ mother loses consciousness

Question 23

How is aortocaval compression prevented in pregnancy?

Answer 23

Elevate the mother’s right torso 15 degrees starting in the second trimester

Question 24

How does intravascular volume change during pregnancy?

Answer 24

Increases by about 35%:

Plasma 45%
Erythrocyte 20%

Question 25

What clotting factors increase during pregnancy?

Answer 25

1, 7, 8, 9, 10, 12

Question 26

How does fibrin break down change during pregnancy?

Answer 26

Increases to compensate for the hypercoagulable state

Mother makes more clots, but breaks them down faster

Question 27

How do PT/ PTT change during pregnancy?

Answer 27

They both decrease by up to 20%

Normal PT at term: 9.6-12.9 s
Normal PTT at term: 24.7- 35 s

Question 28

What are causes of thrombocytopenia in pregnancy?

Answer 28

Gestational thrombocytopenia (hemodilutional and consumption) - most common

Hypertensive disorders

Idiopathic

Question 29

How does MAC change during pregnancy?

Answer 29

Decreases by 30-40% beginning at 8-12 weeks d/t progesterone

Question 30

How does response to local anesthetics change during pregnancy?

Answer 30

Increased sensitivity d/t progesterone

Question 31

How do subarachnoid and epidural space volumes change during pregnancy?

Answer 31

Decrease d/t increase in volume of epidural vein and compression

Question 32

How does gastrin change during pregnancy

Answer 32

Increase

Question 33

How does the change in gastrin affect the pregnant patient?

Answer 33

Increase in gastric volume
Decrease in gastric pH

Question 34

Why does lower esophageal sphincter tone decrease during pregnancy?

Answer 34

Increased progesterone

Increased estrogen

Cephalad displacement of the diaphragm

Question 35

How does renal function change during pregnancy?

Answer 35

Increased cardiac output/ blood volume > GFR/ creatinine clearance/ glucose in urine all increase > creatinine and BUN/ renal absorption decrease

Question 36

What is uterine blood flow in mL/min?

Answer 36

Up to 700-900 mL/min

Question 37

How do changes in serum albumin affect anesthesia for pregnant patients?

Answer 37

Albumin decreases > increase in free fraction of highly protein- bound drugs

Question 38

How does the change in pseudocholinesterase affect anesthesia for pregnant patients?

Answer 38

Pseudocholinesterase decreases in pregnancy, but there is not meaningful change in anesthesia approaches d/t this change