Physiologic Changes of
Pregnancy
Anne McConville M.D.
Question 1
• Which of the following is NOT associated with
pregnancy?
– A) Systolic ejection murmur
– B) Mitral regurgitation
– C) Aortic regurgitation
– D) Pulmonic Regurgitation
– E) Depressed ST segments in the precordial and
limb leads
Answer 1
• C
Cardiac Exam During Pregnancy
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LVH
Accentuated S1, exaggerated S2 splitting
Possible S3 and S4
Leftward displacement of PMI
EKG changes
Question 2
• Which of the following parameters in
decreased at term?
– A) CVP
– B) PCWP
– C) SVR
– D) LVEDV
– E) EF
Answer 2
• C
Hemodynamics During Pregnancy
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SVR decreases
EF increases
PAP/PCWP/CVP no change
LVESV no change
CVP no change
Blood pressure decreases
Question 3
• Cardiac Output is greatest:
– A) During the 1st trimester
– B) During the 2nd trimester
– C) During the 3rd trimester
– D) During Labor
– E) Immediately after delivery
Answer 3
• E
Hemodynamics During Pregnancy
• C.O. in pregnancy
– At end of 1st trimester 35-40% above NP state
– At term, 50% above NP state
– In labor, 75% above NP state
– Immediately after delivery, 150% above NP state
– At 24 hours back to pre-labor values
– Takes 12-24 weeks to return to NP values
Question 4
• Aortocaval compression starts to become
significant at how many weeks EGA?
– A) 5 weeks
– B) 10 weeks
– C) 15 weeks
– D) 20 weeks
– E) 25 weeks
Answer 4
• D
Aortocaval compression
• Depends on position and weeks gestation
– Supine>lateral
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At term, near complete occlusion of IVC
At term, aorta may be compressed as well
LUD important to avoid complications
Supine position associated with 10-20%
decrease in SV and CO
• Supine Hypotension Syndrome
Question 5
• Which of the following lung capacities change
the least during pregnancy?
– A) TV
– B) FRC
– C) ERV
– D) RV
– E) VC
Answer 5
• E
Respiratory Changes of Pregnancy
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MV and AV rise during pregnancy
RR unchanged
TV increased
IRV increased
ERV decreased
RV decreased
FRC and TLC decreased
VC unchanged
Question 6
• Plasma volume and red cell volume increase
by which of the following percentages during
pregnancy?
– A) PV,30%; RCV, 30%
– B) PV, 30%; RCV, 55%
– C) PV, 55%; RCV, 30%
– D) PV, 30%; RCV, 15%
– E) PV, 55%; RCV, 55%
Answer 6
• C
Hematologic Changes of Pregnancy
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Physiologic anemia of pregnancy
TBV 94ml/kg
Term H/H = 11.6/35.5
Plasma proteins decrease
Compensated DIC
Gestation thrombocytopenia
All clotting factors increased EXCEPT:
– II, V unchanged (thromboplastin antecedent)
– XI, XIII decreased (fibrin stabilizing factor)
• PT, PTT shortened, TEG shows hypercoaguable
• BT unchanged
• FDP increased
Question 7
• Which agent is the most useful for raising the
gastric pH just before induction of GA for
emergency cesarean section?
– A) Cimetidine
– B) Metoclopramide
– C) Ranitidine
– D) Sodium Citrate
– E) Magnesium hydroxide and aluminum hydroxide
Answer 7
• D
Gastrointestinal Changes of Pregnancy
• Reduced tone in lower esophageal high-pressure
zone (LEHPZ)
• Gastric emptying is not altered at any time
during pregnancy. Decreased during labor.
• Esophageal and intestinal peristalsis are slowed
• 40% of parturients have constipation
• Gastric volume unchanged. Increased in labor.
• Gastric pH unchanged. Gastric pH increased in
labor.
Question 8
• Which of the following is no increased during
pregnancy?
– A) Kidney Size
– B) Renal Plasma Flow
– C) Creatinine Clearance
– D) BUN
– E) Glucose excretion
Answer 8
• D
Renal Changes of Pregnancy
• Kidneys enlarge by as much as 30%
• GFR and renal plasma flow increase
dramatically
• Creatinine clearance increased to 150200ml/min over the normal 120 ml/min
• BUN and creatinine fall to 8-9 and 0.5-0.6.
• Total protein and albumin excretion are
higher.
• Glucose excretion is increased
Question 9
• Which of the following is true regarding the
parturient?
– A) MAC for inhaled anesthetics is decreased by 75%
– B) Parturients have decreased levels of endorphins,
rendering them more sensitive to pain
– C) Less local anesthetics are required to produce
similar results with neuraxial blockade
– D) Spinal CSF volume is increased
– E) Parturients do not depend on the sympathetic
nervous system for maintenance of hemodynamic
Answer 9
• C
Nervous System Changes of Pregnancy
• MAC decreased 40%
• Pain threshold increased
• Reduced local anesthetic requirements for
neuraxial blockade
• Increased epidural fat, engorgement of
epidural veins, reduced CSF volume
• Positive lumbar epidural pressure
• CSF pressure unchanged, increased during
labor and pushing
• Dependent on SNS
Question 10
• Adverse effects on the mother associated with
aortocaval compression by gravid uterus
include:
– A) N/V
– B) Pallor
– C) Changes in cerebration
– D) Decreased in UBF
– E) all of the above
Answer 10
• E
Anesthetic implications: Positioning
• Importance of LUD/RUD
• Avoid medications that cause venodilation
• Hydration
Question 11
• Failed intubation is how many times greater in
the obstetric population than the general
population?
– A) The same
– B) Double
– C) Four times
– D) Eight times
– E) Twenty times
Answer 11
• D
Implications of GA
• More parturients are Mallampati IV
• Vascular engorgement of airway
– Smaller ETT, avoid nasal intubation
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8X more likely to have failed intubation
Rapid desaturation on induction
MAC decreased by 40%
Reduced pseudocholinesterse activity
Enhanced sensitivity to aminosteroid muscle
relaxants
• Reduced sensitivity to vasopressors
Question 12
• A 24 year old primiparous woman is
undergoing elective C/S for breech position. 5
minutes after the spinal is placed the BP is
80/40 and HR is 100. The best treatment is
– A) Phenylephrine
– B) Ephedrine
– C) Epinephrine
– D) 1000 mL D5LR
– E) 1000 mL hetastarch
Answer 12
• A
Implication of Neuraxial Anesthesia
• Rapid onset and longer duration of spinal
• Pregnancy does not cause increase LA toxicity
• More intervention required to treat
sympathectomy
• Prevention versus treatment of hypotension
• Phenylephrine vs. ephedrine
• Higher doses of vasopressors required
• Impaired coughing mechanism with high
levels