Maternal and fetal physiology Flashcards by Kelsey Coventry Buchanan

MAC is ___ (increased/decreased) in pregnancy

Decreased

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Pregnancy causes ___ (increased/decreased) sensitivity to local anesthetics

Increased

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Ventilation in pregnancy is ___ (increased/decreased)

Increased

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Tidal volume is increased ___% at term

40%

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Respiratory rate ___ (increases/decreases) during pregnancy

Increases—15%

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Mean maternal wt increases by:

17% or approx 12kg

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how much does the uterus weigh?

1 kg

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how much does amniotic fluid weigh?

1 kg

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how much does the fetus and placenta weigh?

4 kg

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how much do blood volume and interstitial fluid weigh?

2 kg

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How much does the deposition of new fat and protein weigh?

4 kg

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Minute ventilation is ___ (increased/decreased) during pregnancy

Increased—50% d/t progesterone

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PaCO2 ___ (increases/decreases) during pregnancy to ___-___ mm Hg

Decreases to 28-32 mm Hg

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PaCO2 decreases during pregnancy d/t ___ventilation, respiratory ___osis,

Hyperventilation, respiratory alkalosis

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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

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Expanding uterus pushes the diaphragm __

Cephalad (up towards head)

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FRC decreases by ___% in pregnancy

20%

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There are no changes in vital capacity or total lung capacity during pregnancy—T/F?

True

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Maternal oxygen consumption ___ (increases/decreases) during pregnancy

increases

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Heart size increased d/t:

increased blood volume and increased stretch and force of contraction

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Heart rate steadily increases _____ (%) above baseline during 1st and 2nd trimester

15-20%

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PR interval and uncorrected QT are:

SHORTENED

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What causes an increase in stroke volume?

Increased estrogen levels

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At term, skin blood flow is _____ higher than during non-pregnancy

3-4 x

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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

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

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

Maternal and fetal physiology Flashcards

(148 cards)