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Special Population-RCM > Obstetric Anesthesia Part I > Flashcards

Obstetric Anesthesia Part I Flashcards

1
Q

The physiologic changes that occur during pregnancy are the result of:

A
  • Increased metabolic demands
  • Hormonal and anatomic changes
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2
Q

How long do physiologic changes in pregnancy last?

A
  • Begin early in pregnancy
  • Last into the postpartum period
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3
Q

When do cardiovascular changes begin during pregnancy?

A
  • Early as the 4th week
  • Continue to the postpartum period
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4
Q

What happens to maternal heart rate (HR) at term?

A

Increases by 20% to 30% at term.

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5
Q

How much does Cardiac Ouput increases during pregnancy?

A
  • Increases ~ 40% over nonpregnant values.
  • Starts in the fifth week of pregnancy.
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6
Q

What factors contribute to the increase in cardiac output during pregnancy?

A
  • Increase in stroke volume (SV) (20%–50%)
  • To a lesser extent, heart rate (HR).
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7
Q

What percentage of the cardiac output perfuses the gravid uterus at term?

A
  • Approximately 10%
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8
Q

Why does cardiac output increase immediately after delivery?

A
  • Due to autotransfusion of blood from the contracting uterus.
  • Increased venous return from aortocaval decompression.
  • Increases 80% above pre-labor values
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9
Q

How does the position of the heart change during pregnancy?

A
  • During pregnancy, the diaphragm is displaced cephalad, shifting the heart up and to the left.
  • Making the cardiac silhouette appear enlarged on x-ray examination.
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10
Q

What is the percentage % increase of Blood volume during pregnancy?

A
  • 25% to 40% throughout pregnancy.
  • To prepare for normal blood loss associated with delivery.
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11
Q

What are the changes of Plasma volume and RBC volume during pregnancy?

A
  • Plasma volume increases by 40%-50%
  • RBC volume increases by only 20%.
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12
Q

What are the normal blood loss ranges for vaginal delivery and uncomplicated cesarean delivery?

A
  • Normal blood loss for vaginal delivery is less than 500 mL.
  • Uncomplicated cesarean delivery, it is 500 to 1000 mL.
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13
Q

What compensatory mechanisms help tolerate blood losses at delivery?

A
  • Increased total Blood volume.
  • Increased Plasma volume.

These mechanism help tolerate blood loss.

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14
Q

How is the Systemic vascular resistance (SVR) affected during pregnancy?

A
  • Decreases by 21% by the end of a term pregnancy.
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15
Q

SVR reduction during pregnancy is primarily due to reduced resistance in the following:

SVR= Systemic Vascular Resistant

A
  • Uteroplacental vascular beds
  • Pulmonary vascular beds
  • Renal vascular beds
  • Cutaneous vascular beds
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16
Q

How much does Diastolic Blood Pressure (DBP) decreases during pregnancy?

A

Up to 15 mm Hg

Resulting in a decrease in MAP.

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17
Q

Aortocaval compression, and what happens when it occurs?

A
  • Decreases venous return to the heart and arterial flow to the uterus and lower extremities.
  • Occurs when the gravid uterus compresses both the vena cava and the aorta.
  • AKA: Aortocaval compression, or “syndrome of supine hypotension,”
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18
Q

What are the consequences of aortocaval compression?

A
  • Decreased cardiac output
  • Compromise fetal perfusion
  • Cause the mother to loose consciousness.
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19
Q

How can the compressive effect of the uterus on the vena cava and aorta be reduced?

A
  • By elevating the mother’s right torso by 15- 30 degrees.
  • This maneuver is known as the left displacement of the uterus.
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20
Q

When should left displacement of the uterus be used?

A
  • For anyone in their second or third trimester of pregnancy.
  • Alleviate aortocaval compression and its associated risks.
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21
Q

Aortocaval Compression

A
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22
Q

What factors in the coagulation cascade increase during pregnancy?

A
  • Factors I (fibrinogen), VII, VIII, IX, X, & XII increase concentration.
  • Through pregnancy and peak at term.
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23
Q

How does von Willebrand factor (vWF) change during pregnancy?

A
  • vWF increases up to 400% at term.
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24
Q

What happens to factors XI and XIII during pregnancy?

A

Tend to decrease during pregnancy.

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25
Q

How do fibrinogen levels change during pregnancy?

A
  • In the nonpregnant state average from 200 to 400 mg/dL.
  • Late in pregnancy normally at least 400 mg/dL and may reach as high as 650 mg/dL.
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26
Q

What typically happens to the platelet count in the third trimester of pregnancy?

A

Remains stable or may be slightly decreased in the third trimester.

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27
Q

What is the overall trend in white blood cell count during pregnancy?

A
  • WBC tends to rise during pregnancy.
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28
Q

What causes capillary engorgement in the upper airway during pregnancy?

A

Results in a narrowed glottic opening and edema in the:

  • Nasal.
  • Oral pharynx.
  • Larynx.
  • Trachea.
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29
Q

Why should nasal intubation be generally avoided in pregnant individuals?

A
  • Due to the risk of a narrowed glottic opening and upper airway edema.
  • A 6.5-to-7-mm cuffed oral endotracheal tube is recommended when intubation is necessary.
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30
Q

What might be beneficial for obese pregnant patients with enlarged breasts during intubation?

A
  • May benefit from the use of a short-handled laryngoscope during intubation.
  • Data handle laryngoscope
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31
Q

How does oxygen (O2) consumption change during term pregnancy?

A
  • Increases by up to 33% at rest.
  • 100% or more during the second stage of labor in term pregnancy.
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32
Q

What causes the increase in minute ventilation during term pregnancy?

A
  • Primarily due to a 40% increase in tidal volume.
  • At term is increased by 50%,
  • The respiratory rate remains unchanged or increases by only 10%.
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33
Q

What happens to the normal arterial partial pressure of carbon dioxide (Paco2) during pregnancy?

A
  • By 12 weeks of gestation, the normal Paco2 decreases to approximately 30 to 32 mm Hg.
  • Remains in this range throughout pregnancy.
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34
Q

How are functional residual capacity (FRC), expiratory reserve volume, and residual volume affected during pregnancy?

A
  • FRC, expiratory reserve volume, and residual volume decrease.
  • Primarily due to upward pressure on the diaphragm, resembling restrictive lung disease.
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35
Q

Factors contributing to rapid arterial desaturation in the apneic pregnant patient:

A
  • The combination of decreased FRC (20%)
  • Increased oxygen (O2) consumption in pregnancy
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36
Q

Do vital capacity and closing capacity (CC) change during pregnancy?

A

No, vital and closing capacities (CC) do not change during pregnancy.

37
Q

How do increased cardiac output and the shift in the oxyhemoglobin dissociation curve contribute to oxygen delivery during pregnancy?

A
  • Rightward shift help maximize oxygen delivery to both the mother and fetus.
38
Q

What can cause maternal Paco2 to drop below 15 mm Hg during pregnancy?

A
  • Increase in Minute ventilation

Up to 300% during contractions

39
Q

Know this APEX Table

40
Q

Know this APEX table.

41
Q

Summary of Physiologic changes

42
Q

How much does uterine blood flow increase to at term?

A

Up to 700-900 mL/min at term.

43
Q

Does uterine blood flow autoregulate?

A
  • No, uterine blood flow does not autoregulate.
44
Q

What primary factors affect uterine blood flow in a low-resistance system?

A
  • Depends on mean arterial pressure (MAP).
  • Cardiac output.
44
Q

What factors affect/depend on Uterine Blood Flow?

A
  • MAP.
  • CO.
  • Uterine vascular resistance.
45
Q

What does recent evidence suggest about using phenylephrine and ephedrine in maintaining placental perfusion and fetal pH in healthy mothers?

A
  • They are efficacious as ephedrine in maintaining placental perfusion and fetal pH in healthy mothers.
46
Q

What physiochemical drug characteristics favor placental transfer?

A
  • Low molecular weight (< 500 Daltons)
  • High lipid solubility
  • Non-ionized
  • Non-polar
47
Q

Where does pain begin in the first stage of labor, and which nerve roots are involved?

A
  • Pain begins in the lower uterine segment and cervix.
  • Pain signals travel to the T10 - L1 posterior nerve roots.
48
Q

What additional areas contribute to pain in the second stage of labor, and which nerve roots are involved?

A
  • In the second stage of labor, pain impulses also come from the vagina, perineum, and pelvic floor.
  • Pain impulses travel from the perineum to the S2 - S4 posterior nerve roots.
49
Q

How should neuraxial techniques be extended to manage labor pain effectively during both stages?

A
  • Neuraxial techniques providing analgesia to T10-L1 during the first stage must be extended to cover S2 - S4.
  • During the second stage of labor for total coverage from T10 - S4.
50
Q

Pain in Labor and Delivery Chart

51
Q

What are the three stages of labor?

A
  • Stage 1: Beginning of regular contractions to full cervical dilation (10 cm)
  • Stage 2: Full cervical dilation to delivery of the fetus (Pain in the perineum begins during stage two)
  • Stage 3: Delivery of the placenta
52
Q

What does the Friedman curve illustrate?

A

Illustrates the normal progress of labor.

53
Q

What is dysfunctional labor, and how can it be managed?

A
  • Dysfunctional labor occurs when labor does not follow the expected pattern.
  • Oxytocin may be required to help the labor progress in such cases.
54
Q

How can understanding the Friedman curve be helpful in anesthesia practice during labor?

A
  • It can help make informed decisions about anesthetic techniques used during labor’s progression.
55
Q

APEX Stages of Labor Table

56
Q

Intrapartum Fetal Evaluation

57
Q

Why is the fetal heart rate important in intrapartum fetal evaluation, and what does it indicate?

A
  • The fetal heart rate is a surrogate measure of overall fetal well-being.
  • Provides an indirect method to assess fetal hypoxia and acidosis.
58
Q

What factors affect fetal oxygenation, and how does the fetus respond to stress?

A
  • Is influenced by uterine and placental blood flow.
  • The fetus responds to stress with peripheral vasoconstriction, hypertension, and a baroreceptor-mediated reduction in heart rate.
59
Q

What does fetal heart rate variability indicate, and what is the normal range?

A
  • Suggests an intact central nervous system and the healthy functioning of the sympathetic (SNS) and parasympathetic (PNS) nervous systems.
  • The normal range of fetal heart rate variability is 6 - 25 bpm.
60
Q

How is variability categorized, and what do different categories indicate?

A

Variability can be categorized as:

  • Minimal (< 5 bpm)
  • Moderate (6 - 25 bpm)
  • Marked (> 25 bpm)
  • Absent (a worrisome finding)
61
Q

What are some factors that can reduce fetal heart rate variability?

A
  • CNS depressant drugs (opioids, sedatives, anesthetic agents, barbiturates, MgSO4),
  • Hypoxemia
  • Fetal sleep
  • Acidosis
  • Certain congenital conditions like anencephaly and cardiac anomalies.
62
Q

What is an acceleration in fetal heart rate (FHR), and what does it indicate?

A
  • An acceleration is an abrupt increase in the FHR above baseline.
  • Accelerations occur in response to fetal movement and indicate adequate oxygenation.
63
Q

When is the FHR pattern considered reactive, and what does it mean?

A
  • Is considered reactive when two or more accelerations occur in a 20-minute period.
  • It suggests that the fetus responds well to stimuli and is likely healthy.
64
Q

What are the three types of decelerations in FHR, and how are they classified?

A
  • Early
  • variable
  • late
  • Based on their timing concerning the contractions during labor.
65
Q

What causes early decelerations in FHR?

A

Fetal head compression during uterine contractions.

66
Q

How do early decelerations affect the fetal heart rate?

A
  • Heart rate decrease of <20 bpm from baseline.
  • Mirroring uterine contractions.
67
Q

Do early decelerations pose a risk of fetal hypoxemia?

A

No, early decelerations do not pose a significant risk of fetal hypoxemia.

68
Q

Early decelerations have an onset and offset that:

A
  • Parallel uterine contraction
  • They typically lose variability with each deceleration.
69
Q

Late decelerations occur due to:

A
  • Uteroplacental insufficiency
  • Leads to decreased uteroplacental perfusion and fetal compromise.
70
Q

When does FHR fall during Late Deceleration?

A
  • After the peak of contraction.
  • It returns to baseline after the contraction.
71
Q

Late decelerations are associated with:

A
  • Contraction and characterized by a gradual reduction in FHR.
72
Q

Late decelerations are caused by conditions like:

A
  • Maternal hypotension
  • Hypovolemia
  • Acidosis
  • Preeclampsia causes late decelerations.
73
Q

Late Deceleration poses a risk for:

A
  • Fetal hypoxemia
  • Requires urgent assessment of fetal status.
74
Q

Variable decelerations occur due to:

A

Umbilical cord compression.

75
Q

Variable decelerations show:

A

There is no consistent pattern concerning uterine contractions.

76
Q

During Variable decelerations, Umbilical compression leads to:

A

Baroreceptor-mediated reduction in FHR.

77
Q

Variable decelerations are usually:

A

Self-limiting and maintaining variability during deceleration.

78
Q

Variable Decelerations

A
  • Prolonged fetal compromise may extend FHR recovery time.
  • They pose a risk for fetal hypoxemia and require urgent assessment of fetal status.
79
Q

How does ACOG categorize fetal heart rate (FHR) tracings?

A

ACOG categorizes FHR tracings into a three-tiered system.

80
Q

What defines Category I FHR tracings, and what do they predict?

A
  • Category I FHR tracings are normal with a normal baseline HR, moderate variability, absent variable, and late decelerations.
  • They predict normal acid-base balance.
81
Q

What do Category II FHR tracings include, and what do they indicate?

A
  • Category II FHR tracings include those not classified as Category I or III.
  • They do not predict abnormal acid-base status and require continued observation.
82
Q

Describe Category III FHR tracings and what they predict.

A
  • Category III FHR tracings have fetal bradycardia or absent variability with recurrent late or variable decelerations.
  • They predict abnormal acid-base status and necessitate prompt intervention.
83
Q

What caution should be exercised when considering neuraxial analgesia in the presence of nonreassuring FHR tracing?

A

If the FHR tracing suggests hypoxia, caution should be used when deciding to proceed with neuraxial analgesia.

84
Q

What factors should be carefully considered regarding fetal compromise and anesthetic intervention?

A

Consider the severity of fetal compromise and the possibility of worsening it with anesthetic intervention.

85
Q

Under what circumstances might the obstetric team request a neuraxial anesthetic for a patient with nonreassuring FHR tracing?

A

The obstetric team may request a neuraxial anesthetic in anticipation of a possible urgent and unplanned operative vaginal delivery or cesarean delivery.

86
Q

What is intrauterine resuscitation, and what are some interventions involved in it?

A
  • Intrauterine resuscitation includes interventions to improve the condition of a compromised fetus in utero.
87
Q

What are some examples of Intrauterine Interventions?

A
  • Changing maternal position
  • Rapid IV fluid infusion
  • Discontinuing oxytocin
  • IV pressor support for maternal Hypotension
  • Rocolytic agents
  • Maternal oxygen administration to correct maternal hypoxia.

Special Population-RCM (8 decks)

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