Maternal and fetal physiology Flashcards
MAC is ___ (increased/decreased) in pregnancy
Decreased
Pregnancy causes ___ (increased/decreased) sensitivity to local anesthetics
Increased
Ventilation in pregnancy is ___ (increased/decreased)
Increased
Tidal volume is increased ___% at term
40%
Respiratory rate ___ (increases/decreases) during pregnancy
Increases—15%
Mean maternal wt increases by:
17% or approx 12kg
how much does the uterus weigh?
1 kg
how much does amniotic fluid weigh?
1 kg
how much does the fetus and placenta weigh?
4 kg
how much do blood volume and interstitial fluid weigh?
2 kg
How much does the deposition of new fat and protein weigh?
4 kg
Minute ventilation is ___ (increased/decreased) during pregnancy
Increased—50% d/t progesterone
PaCO2 ___ (increases/decreases) during pregnancy to ___-___ mm Hg
Decreases to 28-32 mm Hg
PaCO2 decreases during pregnancy d/t ___ventilation, respiratory ___osis,
Hyperventilation, respiratory alkalosis
Body compensates to respiratory alkalosis during pregnancy by excreting ___ ions to maintain a normal pH…this leads to ___ (what acid-base balance?)
Bicarbonate ions; leads to metabolic acidosis
Pregnancy is a state of partially compensated respiratory alkalosis
Expanding uterus pushes the diaphragm __
Cephalad (up towards head)
FRC decreases by ___% in pregnancy
20%
There are no changes in vital capacity or total lung capacity during pregnancy—T/F?
True
Maternal oxygen consumption ___ (increases/decreases) during pregnancy
increases
Heart size increased d/t:
increased blood volume and increased stretch and force of contraction
Heart rate steadily increases _____ (%) above baseline during 1st and 2nd trimester
15-20%
PR interval and uncorrected QT are:
SHORTENED
What causes an increase in stroke volume?
Increased estrogen levels
At term, skin blood flow is _____ higher than during non-pregnancy
3-4 x
SVR is increased or decreased during pregnancy at term?
DECREASED (20%)
What is compressed during aortocaval compression?
aorta and inferior vena cava – depending on positioning and gestational age
Blood returns from lower extremities through ____, _____, _____, and _____ veins
intraosseous
verterbral
paravertebral,
epidural
Collateral return is not as great, resulting in decreased
right atrial pressure
SV and CO decreased by _____% when in supine position at term
10-20%
Symptoms of supine hypotension syndrome (aka overt caval compression)
HoTN
Bradycardia
Sweating
Pallor
N/V
How to prevent supine hypotension syndrome:
Place a rigid wedge under right hip and/or tilt table w left side down–> displace uterus to left
Postpartum increase in CO is d/t:
relief of vena cava compression
decreased lower extremity venous pressure
sustained myocardial contraction
loss of low-resistance placental circulation
Hypoxic ventilatory response is ____ (increased/decreased) during pregnancy to ____ normal level
increased
2x normal levels
What secondarily contributes to the increased hypoxic ventilatory response?
Elevations in estrogen and progesterone
Diaphragm excursion ____ (increased/decreases) by___ cm
increases
2cm
chest wall excursion is ____ (increases/decreases)
decreases
_____ causes relaxation of the ligamentous attachments to the lower ribs
Relaxin (ribs in more horizontal position)
Capillary engorgement of the ____, ____, and ____ mucosa begins early in 1st trimester and increases through pregnancy
Larynx
Nasal
oropharynx
_____ on the nasal mucosa may cause rhinitis and epitaxis d/t vasodilation
Estrogen
Dyspnea is a common complaint in the first and 2nd trimesters, due to:
Increased resp drive
Decreases PaCo2
Increased O2 consumption
Increased pulmonary blood volume
anemia
nasal congestion
Exercise has ____ effect on ventilation or alveolar gas exchange
No
What makes the mother prone to hypoxia during pregnancy?
↓FRC & ↑O2 Consumption
Preoxygenate & RSI w/ Cricoid Pressure
What Respiratory changes helps delivery of oxygen to fetus?
Increase of P50 Hemoglobin from 27 to 30 mmHg
What are the Neuro Changes of Pregnancy?
Decreased MAC, Epidural Space, and CSF
Engorged Epidural Veins
Increased LA Sensitivity
What are the Respiratory Changes of Pregnancy?
↑TV (40%)
↑RR (15%)
↑Minute Ventilation (50%)
↓PaCO2
Which of the following is decreased during Pregnancy? (Select 3)
A. Vital Capacity
B. Total Lung Capacity
C. Functional Residual Capacity
D. Dead Space
E. Airway Resistance
↓FRC (20%)
↓Dead Space
↓Airway Resistance
Why should Hyperventilation be avoided in Pregnancy during Anesthesia?
Low PaCO2 causes uterine vasoconstriction decreasing placental blood flow & left HgbO2 shift
What Intubation equipment should be available for Pregnant Patients?
Smaller ETT
Shorter Handle
Avoid Nasal Intubation
How is Oxygen Delivery optimized during Pregnancy?
↑Cardiac Output
Right HgbO2 Shift
↓PVR d/t Increased Progesterone
How is Plasma Volume affected by Pregnancy?
Increased Plasma Volume d/t Increased Renin
in excess of red cell mass (RBC vol inc ~20%), i.e. relative hypervolemia.
Inc. renin –> inc. aldosterone –>sodium/H20 retention
What are the different phases of changes in Cardiac Output during Labor?
Latent Phase: ↑15%
Active Phase: ↑30%
Second Stage: ↑45%
Postpartum: ↑80%
What are the CV changes during Pregnancy?
Blunted response to Adrenergic drugs
Cardiac Hypertrophy
Heart Murmurs
↓Plasma Colloid Osmotic Pressure
How does the blood change in a pregnant patient?
Depressed Cell-Mediated Immunity
Hypercoagulation
PT/PTT decreases by 20%
PT normal range: 9.6-12.9 seconds
PTT normal range: 24.7-35 seconds
Which Coagulation Factors are Increased during Pregnancy?
1, 7, 8, 9, 10, 12
Which Coagulation Factors are Decreased during Pregnancy?
11 & 13
Which Coagulation Factors are unaffected by Pregnancy?
2 & 5
What are the Renal Changes during Pregnancy?
↑Blood Flow & Filtration
↓BUN & Creat
Mild Glycosuria & Proteinuria
How does pregnancy affect the Gastroesophageal Sphincter?
Reduced Competence & Tone
What are the GI Changes during Pregnancy might increase Aspiration Risk?
Increased Acid Secretion & Gastric Fluid
How is the Gallbladder affected by Pregnancy?
Sluggish & Gallstones d/t decreased CCK
How is the Liver affected by Pregnancy?
20% Decrease in Pseudocholinesterase
A simultaneous increase in volume of distribution counters any clinically significant prolongation of NMB with succinylcholine.
(succs can still be used w no problem)
How does Pregnancy affect Blood Glucose?
Insulin Resistance = ↑Blood Glucose transfer to Fetus
What are the methods of transfer across the Placenta?
Diffusion
Bulk Flow
Active Transport
Pinocytosis
Breaks
How long can the Fetus live without Oxygen?
10 mins
What is the transfer of Oxygen to the Fetus dependent on?
Maternal Uterine Blood Flow vs. Fetal Umbilical Blood Flow
Pregnant women should not lay supine after ___ wks
20
Maternal vascular capacitance is _____ at the time of delivery.
reduced
How much Oxygen is stored and consumed by the Fetus?
Stored O2: 42 mL
Consumed O2: 21 mL/min
How does the Fetus compensate for the Placental PaO2 of 40 mmHg?
Mom: Right HgbO2 Shift
Fetus: Left HgbO2 Shift & More Hgb
How is CO2 transferred across the Placenta?
Simple Diffusion
Fetal Hgb has lower CO2 affinity than Mom
Normal Uterine blood flow is 50 mL/min. How much is that increased during Pregnancy?
600-700 mL/min (10% of Cardiac Output)
80% of that goes to Placenta; the rest to Myometrium
The placenta must provide ____ml O2/min/kg for fetal body weight for fetal growth and development while adults require ____ml O2/min/kg at rest
8
3-4
What factors affect Uterine Blood Flow (UBF)?
systemic BP
Uterine Vasoconstriction
Uterine Contractions
What anesthetic agents and drugs can decrease Uterine Blood flow?
Thiopental
Propofol
Gases > 1 MAC
(d/t HoTN)
How does Ketamine, Opioids, and N2O affect Uterine Blood Flow?
Little to No Effect
How does high serum Local Anesthetics affect the Uterus?
Uterine Vasoconstriction, but Neuraxial Analgesia can reduce Vasoconstriction
Increased uterine blood flow is a result of:
Pain relief
Decreased sympathetic activity
Decreased maternal hyperventilation
Decreased uterine blood flow is a result of:
HoTN
IV injection of LAs/Epi
Absorbed locals
decreased uterine arterial pressure
increased uterine venous pressure
increased uterine vascular resistance
What happens to infant’s heart & lungs at birth?
Oxygen filling lungs ↓Pulm. Vascular Resistance
↑LAP closes Foramen Ovale
↑Oxygen Tension closes Ductus
What can happen if the Ductus remains open w/ Hypoxia or Acidosis?
Downward Spiral of Hypoxia & Acidosis d/t increase R-to-L Shunt
When does normal Labor begin?
40 +/- 2 weeks after LMP
What happens in the 1st Stage of Labor?
Latent Phase: Minor Dilation 2-4cm & Infrequent Contractions
Active Phase: Progressive Dilation to 10cm & Regular Contractions q3-5 min
When is the 2nd Stage of Labor?
From Complete Dilation to Delivery
What is the 3rd Stage of Labor?
From Infant Delivery to Placenta Delivery
Airway resistance in pregnancy is ___ (increased/decreased)
Decreased
Why does PVR drop in pregnancy?
Increased progesterone relaxes venous smooth muscle
What factors modulate the maintenance and regulation of uteroplacental blood flow?
altered responses to vasoconstrictors, increases in endothelium-derived vasodilators, and the effects of steroid hormones and shear stress
_____is the method most commonly used clinically to assess uteroplacental blood flow in humans.
Doppler ultrasonography
Fetal blood flow is characterized by three anatomic communications between the left and right circulations:
the ductus venosus
the foramen ovale
the ductus arteriosus
uterine blood flow during non pregnant state:
100mL/min
Uterine blood flow does NOT autoregulate, therefore it is dependent on:
MAP
CO
Uterine vascular resistance
uterine blood flow equation:
uterine artery pressure-uterine venous pressure/uterine vascular resistance
Is ephedrine or phenylephrine better to use in pregnancy
phenylephrine= less fetal acidosis
Drug characteristics that favor placental transfer
Low molecular wt <600 daltons (most anesthetic drugs)
High lipid solubility
Non-ionized
Non-polar
Drugs w no placental transfer:
NMB
glycopyrrolate
Heparin
Insulin
Drugs w significant placental transfer
Local anesthetics (except chloroprocaine d/t rapid metabolism
Volatile anesthetics
opioids
benzodiazpines
atropine
beta-blockers
Magnesium (non lipophilic bit it’s small)
FRC=
RV + ERV
The parturient is at a higher risk of difficult:
mask ventilation
laryngoscopy
intubation
Factors that make airway management more complicated include:
increased Mallampati score
upper airway vascular engorgement
narrowing of glottic opening (use smaller ETT -6.0-7.0)
Functional residual capacity falls below ____ ____
Closing capacity which causes airway closure during tidal breathing
_____ increased MV up to 50%
progesterone (respiratory stimulant)
airway edema is made worse by:
preeclampsia
tocolytics
prolonged trendelenburg
What hormones contribute to vascular engorgement and hyperemia in pregnancy
Progesterone
Estrogen
Relaxin
What type of laryngoscope handle is recommended for large-breasted women?
a short-handed laryngoscope (datta handle)
While MAP and SBP remain stable throughout pregnancy ____, ___ and ___ decrease
DBP
SVR
PVR
Plasma volume expansion outpaces new RBC production leading to:
dilution anemia
CO returns to pre-labor values in:
24-28hrs
CO returns to pre-pregnancy values in:
2 wks
twins cause CO to increase ____% above a single fetus
20%
Cardiac axis:
left deviation
gradid uterus pushed diaphragm cephalad = heart pushed up and left
Progesterone:
increases RAAS activity
vascular muscle relaxation
Increased MV
Renal increases
GFR
Creatinine clearance
Glucose in urine
creatinine and BUN
decreased
uterine blood flow is: (select all that apply)
20% of CO
700mL/min
not autoregulated
reduced by phenylephrine
700mL/min
not autoregulated
what stage of labor begins w the onset of perineal pain?
latent phase
active stage
first stage
second stage
second stage
a laboring mother is always considered:
a FULL STOMACH
According to the ASA practice guidelines, the laboring mother who is healthy may:
drink a moderate amount of clear liquids throughout labor
eat solid food up to the point a neuraxial block is placed
which of the following parameters normally decreases during pregnancy (select 4)
platelet count
oxygen consumption
GFR
HR
Peripheral vascular resistance
Hemoglobin content in g/dL
Blood volume
Functional residual capacity
Platelet count
Peripheral vascular resistance
Hemoglobin content in g/dL
Functional residual capacity
Which characteristic will increase the likelihood that a maternally-administered drug will cross the placenta?
A.) a molecular wt greater than 1000 daltons
B.) increased drug ionization
C.) increased drug polarity
D.) increased lipid solubility
increased lipid solubility
Which of the following lab values tends to be decreased in full-term parturients?
serum albumin
lactate dehydrogenase
alkaline phosphatase
alanine aminotransferase
serum albumin
Select two physiologic characteristics that you would expect to be increased in an obstetric patient at term
Minute ventilation
Functional residual capacity
Oxygen consumption
Minimum alveolar concentration
Minute ventialtion
Oxygen consumption
Which of the following statements concerning placental perfusion is correct?
A. Placental perfusion is autoregulated
B. Placental perfusion is directly related to maternal blood pressure
C. The intervillous space receives blood from the quadratic arteries
D. The placenta receives 50% of the maternal cardiac output
B. Placental perfusion is directly related to maternal blood pressure
What is the suggested block height for patients undergoing cesarean section?
A. L1
B. T10
C. T6
D. T4
D. T4
Which of the following drugs would most likely exhibit an appreciable increase in its circulating free fraction in a full-term parturient?
A. a highly protein-bound drug
B. a drug metabolized by cholinesterases
C. a highly water-soluble drug
D. chiral drugs
A. a highly protein-bound drug
Which of the following parameters increases with pregnancy?
A. PaO2
B. PaCO2
C. HCO3
D. Total lung capacity
A. PaO2
Which of the following statements is true of a full-term parturient?
A. Basal oxygen consumption is increased by 33 percent
B. The partial pressure of arterial carbon dioxide is increased
C. The partial pressure of arterial oxygen is decreased
D. Plasma bicarbonate increases 10 percent
A. Basal oxygen consumption is increased by 33 percent
During the third trimester of pregnancy, the cardiac output
A. increases primarily due to an increase in stroke volume
B. increases primarily due to an increase in heart rate
C. decreases primarily due to a decrease in stroke volume
D. decreases primarily due to a decrease in heart rate
A. increases primarily due to an increase in stroke volume
Rapid sequence induction, cricoid pressure, and a cuffed endotracheal tube are recommended for pregnant women receiving general anesthesia from ____ weeks on even if no symptoms of reflux are present.
A. 12 B. 15 C. 18 D. 20
D. 20
Which of the following statements regarding the hematology studies of a full-term parturient is correct?
A. The total blood volume decreases
B. The average platelet count is about 50,000
C. A relative polycythemia is present during pregnancy
D. The red blood cell mass increases
D. The red blood cell mass increases
Which of the following decreases with pregnancy? (select two)
A. renal blood flow B. alkaline phosphatase levels C. serum creatinine D. plasma cholinesterase activity
C. serum creatinine
D. plasma cholinesterase activity
Which of the following parameters decreases during pregnancy?
A. Systemic vascular resistance B. Total blood volume C. Heart rate D. Stroke volume
A. Systemic vascular resistance
Pregnancy typically produces
A. an increase in the glomerular filtration rate
B. an increase in the serum creatinine level
C. an increase in the blood urea nitrogen level
D. a decrease in renal blood flow
A. an increase in the glomerular filtration rate
The second stage of labor occurs when
A. regular uterine contractions begin
B. the cervix begins to dilate
C. the cervix is fully dilated
D. the fetus crowns
C. the cervix is fully dilated
How long after delivery does the cardiac output of the mother remain elevated?
A. 12 hours B. 2 days C. 7 days D. 14 days
D. 14 days ( 2 weeks)
Which of the following drugs does NOT pass the placenta easily?
A.) etomidate
B.) ephedrine
C.) Atropine
D.) glycopyrrolate
D.) glycopyrrolate
What is the P50 of fetal hemoglobin at term?
A.) 12
B.) 18
C.) 24
D.) 30
B.) 18
Cardiac output increases dramatically during pregnancy and delivery. The cardiac output returns to nonpregnant values by how long postpartum?
A.) 12 hrs
B.) 1 day
C.) 2 weeks
D.) 6 months
C.) 2 weeks
Uterine blood flow at term pregnancy typically increases to about
A.) 100mL/min
B.) 250 mL/min
C.) 500 mL/min
D.) 750 mL/min
D.) 750 mL/min
Which of the following cardiovascular parameters is decreased at term?
A.) CVP
B.) PCWP
C.) SVR
D.) LVESV
C.) SVR
Cardiac output is the GREATEST
A.) during first trimester
B.) during the 3rd trimester
C.) during labor
D.) immediately after delivery of the newborn
D.) immediately after delivery of the newborn
Which of the following respiratory parameters is NOT increased in the parturient?
A.) Minute ventilation
B.) Tidal volume
C.) Arterial PaO2
D.) serum bicarbonate
D.) serum bicarbonate
Which of the following lung volumes or capacities change the LEAST during pregnancy?
A.) Tidal volume
B.) Functional residual capacity (FRC)
C.) Expiratory reserve volume (ERV)
D.) Vital Capacity
D.) Vital Capacity
Which of the following properties of epidurally administered local anesthetics determines the extent to which epi will prolong the duration of blockade?
A.) Molecular weight
B.) Lipid solubility
C.) pKa
D.) concentration
B.) Lipid solubility
Which of the following is NOT increased during pregnancy?
A.) Renal plasma flow
B.) creatinine clearance
C.) Blood urea nitrogen (BUN)
D.) glucose excretion
C.) Blood urea nitrogen (BUN)
Passive diffusion of substances across the placenta is enhanced by all of the following EXCEPT
A.) Low molecular wt of the substance
B.) High water solubility of the substance
C.) Low degree of ionization of the substance
D.) Large concentration gradient of the drug
B.) High water solubility of the substance
Which of the following statements is CORRECT in describing differences between fetal and maternal blood during labor?
A.) Fetal blood has a lower hemoglobin concentration than does maternal blood
B.) Fetal placental blood flow is twice maternal placental blood flow
C.) Fetal hemoglobin has a greater affinity for O2 than does maternal hemoglobin
D.) The fetal oxyhemoglobin dissociation cure is shifted to the right of the maternal oxyhemoglobin dissociation curve
C.) Fetal hemoglobin has a greater affinity for O2 than does maternal hemoglobin
Aortocaval compression starts to become significant in a normal pregnancy at how many weeks EGA?
A.) 10 weeks
B.) 15 weeks
C.) 20 weeks
D.) 25 weeks
C.) 20 weeks
Adverse effects (on the mother) associated with aorto-caval compression by the gravid uterus include
A.) nausea and vomiting
B.) changes in cerebration
C.) fetal distress
D.) all of the above
D.) all of the above