Increase of 300 mL/contraction
Cardiac output Increase of 30%–50% Additional increase of 50%
Systemic vascular resistance Decrease Increase
3. D. Maternal intravascular fluid volume increases in the first trimester, and at
term, the plasma volume is increased by about 45%, while the erythrocyte volume
increases only 20%, accounting for the relative anemia of pregnancy despite the
higher hematocrit. This serves to decrease blood viscosity and improve flow. This
increase in maternal blood volume also allows women to better tolerate the blood
loss associated with delivery.
4. A. Cardiac output in the third trimester is increased by nearly 50% due to an
increase in both the stroke volume and heart rate to meet augmented maternal and
5. C. The largest increase in cardiac output is seen immediately after delivery as
the increase in blood volume persists with an additional increase in intravascular
volume (300–500 mL) from the contracting uterus. This autotransfusion further
increases cardiac output. Patients with fixed stenotic valvular lesions therefore
should continue to be monitored closely after delivery.
6. D. Hyperventilation with oxygen consumption creates significant changes in
acid–base status that can be hazardous to the fetus. Extremely low PaCO2
result in vasoconstriction and global reduction in placental perfusion and blood flow.
The alkalemia also shifts the oxygen–hemoglobin dissociation curve to the left,
impairing the release of oxygen from maternal blood to fetal blood. Both factors will
decrease the availability of oxygen delivery to the fetus (Fig 17-1).
7. C. The anterior spinal cord achieves its blood supply from the anterior spinal
artery, which is single and unpaired. Due to this, injury or thrombosis can lead to a
unique constellation of symptoms consisting of loss of motor function, pain, and
temperature below the level of the injury, bilaterally. The posterior columns, carrying
fine touch and proprioception, are preserved as paired posterior spinal arteries
8. B. The presence of moderate–severe aortic stenosis makes it especially crucial
to minimize sympathetic output and hemodynamic deterioration. Though a regional
anesthetic is capable of attenuating the release of catecholamines during painful
labor, one must be vigilant to prevent hypotension. The abrupt hypotension following
spinal anesthesia with local anesthetics may result in cardiac hypoperfusion and
ischemia. Epidural anesthesia, with its slow onset to effect, is usually well tolerated,
especially with adequate volume loading. Inhaled nitrous oxide and oral analgesics
are unlikely able to provide adequate analgesia to maintain hemodynamic stability in
this patient with a fixed valve lesion.
9. A. Although there is an increase in cardiac output and plasma volume, the
systemic blood pressure in normal maternal physiology does not actually increase
due to decreases in systemic vascular resistance. In fact, the mean arterial pressures
generally decrease by approximately 10 to 15 mm Hg. Certainly, her fixed stenotic
10. B. The mechanism of supine hypotension syndrome is decreased venous return as
a result of aortocaval compression by the gravid uterus when the pregnant woman
assumes the supine position. Removal of the compression with left-uterine
displacement can minimize this incidence, which is particularly important for patients
undergoing regional or general anesthesia because usual compensatory increases in
systemic vascular resistance will be blocked.
11. C. With increasing enlargement of the uterus, the diaphragm is forced cephalad,
which is responsible for decreasing the FRC. While supine, FRC can become less
than CC for many small airways resulting in atelectasis. Expiratory reserve volume
and residual volume are also decreased while both vital capacity and CC remain
12. B. Oxytocin remains a first-line agent in the prevention and management of uterine
atony. Oxytocin has important cardiovascular side effects, including hypotension and
tachycardia, setting the stage for myocardial ischemia. Slow continuous intravenous
administration of oxytocin minimizes maternal hemodynamic instability and also
encourages maintenance of uterine tone.
13. D. Decreased functional residual capacity (FRC) with increased minute ventilation
results in an escalation in rate at which changes of alveolar concentration of inhaled
anesthetics can be achieved, increasing speed of induction, emergence, and changes
14. B. MAC progressively decreases during pregnancy—at term by as much as 40%—
for all volatile anesthetic agents.
15. C. Increased oxygen consumption and decreased reserve due to reduced functional
residual capacity can result in a rapid fall in arterial oxygen tension during apnea.
This occurs despite careful preoxygenation, which importantly provides a time
16. D. Minute ventilation is increased above prepregnant levels primarily by a
significant increase in tidal volume with smaller increases in respiratory rate. Resting
maternal PaCO2 decreases from 40 to about 32 mm Hg, though arterial pH
approaches normal levels with increased renal excretion of bicarbonate ions. At term,
PaO2 generally does not change significantly, though may be slightly decreased,
reflecting airway closure and atelectasis.
17. A. Elevated levels of 2,3-DPG decreases maternal hemoglobin affinity for oxygen,
shifting the P50 curve to the right (increasing it from 27 to 30 mm Hg) to enhance
18. C. An increased metabolic rate in addition to the pregnancy-induced increase in
minute ventilation results in a markedly decrease in PaCO2
Such that a PaCO2 of 40 to 45 on ABG would indicate CO2
respiratory alkalosis is minimized due to metabolic compensation with increased
renal excretion of bicarbonate and thus a lower HCO3 as compared to the
nonparturient. At 35 weeks’ gestation, a normal maternal pH is approximately 7.44.
Lastly, maternal position can affect PaO2
, even in healthy parturients. In the upright
position and breathing room air, PaO2 will be slightly greater than 100 mm Hg, as the
increase in cardiac output is greater than the increase in oxygen consumption.
However, as functional residual capacity decreases during pregnancy and is often
less than closing capacity in the supine position, PaO2 will frequently fall below 100
mm Hg, while supine likely reflecting atelectasis.
19. B. Engorgement of epidural veins occurs with progressive enlargement of the
uterus contribute to decrease in size of the epidural space and can predispose to
intravascular injection with attempted epidural anesthesia. Additionally, CSF volume
is decreased in the subarachnoid space, facilitating the spread of local anesthetics.
Therefore, in pregnancy, there is a decrease in dose requirements of local anesthetics
20. A. Similar to physiologic anemia of pregnancy, dilution of serum albumin will
result in higher free blood levels of highly protein-bound drugs (e.g., fentanyl and
midazolam), resulting in a more robust clinical effect as compared to the nonpregnant
state. Though plasma cholinesterase activity is also decreased, this is unlikely to be
of clinical significance with regard to the duration of action of succinylcholine.
21. D. Cephalad displacement of the pylorus, decreased gastrointestinal motility, and
decreased pH of gastric contents all contribute to significant risk of aspiration and
resultant pneumonitis during labor and delivery. H2
antacids, do not alter the pH of gastric contents already present in the stomach.
Avoidance or particulate antacids can minimize pulmonary damage should aspiration
occurs. Though metoclopramide can increase gastric motility to decrease the gastric
volume, opioid-induced hypomotility is resistant to this treatment.
22. C. Late decelerations are shallow, uniformly shaped decelerations that are
characterized by a gradual decrease from and return to baseline of the fetal heart
rate. The nadir of late decelerations usually is between 5 and 30 bpm below the
baseline. Late decelerations typically begin near the end of a contraction; with return
to baseline, FHR always occurring after the contractions have ended. Uteroplacental
insufficiency (e.g., umbilical cord compression, maternal supine hypotension
syndrome) contributes to late decelerations. Cephalopelvic disproportion and fetal
head compression are associated with early decelerations (Fig 17-2).
23. C. The uterine vasculature is not autoregulated and remains essentially maximally
dilated under normal conditions during pregnancy. Epidural or spinal anesthesia does
not pathologically alter uterine blood flow as long as maternal hypotension is
avoided. Acceptable options include left-uterine displacement to minimize
aortocaval compression, increase IV fluids to improve volume status, Trendelenburg
position to encourage venous return, and α-adrenergic agents to increase maternal
arterial blood pressure. Prompt correction of maternal hypotension will lead to best
24. B. The Apgar is a scoring system for evaluating an infant’s physical condition at
birth. The infant’s heart rate (1 pt), respiration (1 pt), muscle tone (0 pt), response to
stimuli (1 pt), and color (0 pt) are rated at 1 minute and again at 5 minutes after birth.
Each factor is scored 0, 1, or 2; the maximum total score is 10 (Fig 17-3).
25. C. A team that is skilled at reviving newborn infants should be at the delivery if
meconium staining is found in the amniotic fluid. Newborns should be placed under
radiant heat sources to support body temperature, as heat loss can be rapid. If the
baby is active and crying, no treatment is needed. If the baby is not active and crying
right after delivery, the trachea should be suctioned. Avoiding positive-pressure
ventilation before suctioning can minimize further aspiration into the lungs.
26. D. The invention of the forceps has had a profound influence on obstetrics,
providing an alternative modality to surgical delivery during cases of difficult,
nonprogressing, or obstructed labor. High-forceps delivery refers to attempted
delivery prior to head engagement, which carries high risk and is no longer an
accepted practice. Certainly, there is risk to both mother and child. Maternal risks
include increased postpartum recovery time and pain, while in the fetus, forceps
assistance can cause minor injuries such as cuts and bruises, or more serious
damages such as facial nerve injury, clavicle fracture, and intracranial hemorrhage.
27. D. The fetal circulation is markedly different from the adult circulation as gas
exchange does not occur in the lungs but instead occurs in the placenta. The placenta
provides oxygen-rich blood via the umbilical vein to the fetal circulation and
removes deoxygenated blood via umbilical arteries. In addition, the fetal
cardiovascular system is designed in such a way that the most highly oxygenated
blood is delivered preferentially to vital organs (brain and heart) while minimizing
flow to nonvital fetal organs (liver and lungs). The presence of intra- and extracardiac
shunts achieves these circulatory adaptations in the fetus; the ductus venosus shunts
oxygenated blood away from the liver, while the ductus arteriosus shunts blood away
from the fetal pulmonary bed. The foramen ovale effectively shunts blood from the
right to the left atrium, resulting in equalization of right and left sides of the heart (Fig
28. B. Successful transition from fetal to neonatal circulation starts when the umbilical
cord is clamped and cut such that the placenta no longer acts as the “lungs” to
provide oxygen. The ductus venosus closes physiologically as soon as the umbilical
vein is obstructed with the clamping of the cord. With the loss of the placenta, a large
low-resistance bed, systemic vascular resistance rapidly increases. With the first
breath, the lungs inflate with a fall in pulmonary vascular resistance and increase
pulmonary blood flow. The rise in pulmonary venous return results in left-atrial
pressure being slightly higher than right-atrial pressure to close the foramen ovale.
Decrease in circulating prostaglandins and the higher blood oxygen content of blood
result in vasoconstriction of the ductus arteriosus.
29. C. Placental exchange of substances occurs principally by diffusion from the
maternal circulation to the fetus and vice versa, which depends on maternal–fetal
concentration gradients, maternal protein-binding, molecular weight, lipid solubility,
and the degree of ionization of that substance.
30. D. Local anesthetics easily cross the placenta, which is affected by several
independent factors, including maternal–fetal hemodynamics, permeability of the
placenta, concentration of free drug in the maternal plasma, and physiochemical
properties of the drug itself. Lidocaine is less lipid soluble than bupivacaine, which
is reflected in their lipid–water partition coefficients. Protein-binding also plays a
role in the diffusion of drugs across the placenta. The unbound form of the drug is
freely transferred, whereas protein-binding limits diffusion. High protein-binding, as
in the case of bupivacaine, leads to much lower fetal-to-maternal plasma ratio. Local
anesthetics are weak bases and therefore have minimal ionization at physiologic pH.
is to the physiologic pH, the more it will be affected by the acid–
31. D. Somatic and visceral afferents from the uterus and cervix travel with
sympathetic nerve fibers en route to the spinal cord. These fibers pass through the
inferior, middle, and superior hypogastric plexuses to arrive at the sympathetic chain.
The first stage of labor is largely visceral (T10–L1) due to uterine contractions. As
labor progresses, the parturient encounters the second stage of labor with additional
somatic pain complaints as the fetus descends into the pelvis causing distension of
the vagina, perineum, and pelvic floor muscles. This somatic pain is transmitted via
32. B. Lumbar sympathetic blocks and paracervical blocks, though rarely performed
for labor analgesia, are appropriate targets during the first stage of labor. However,
paracervical blocks are rarely used in current practice because of an association with
fetal bradycardia. Epidural and combined spinal–epidural techniques are ideal, in
that they are able to block the visceral afferent fibers responsible for the first stage of
labor and the somatic nerve fibers through which the second stage is transmitted. The
obstetrician can also provide pudendal blocks during delivery to mitigate somatic
pain during the second stage, though cannot mitigate visceral first stage pain.
33. D. Preeclampsia is a syndrome manifested after the 20th week of gestation, which
is characterized by systemic hypertension (>140/90 mm Hg), proteinuria (>0.5
g/day), generalized edema, and complaints of a headache. HELLP syndrome
(hemolysis, elevated liver enzymes, low platelets) is a severe form of preeclampsia.
Eclampsia is present when seizures are superimposed on preeclampsia, and it is
potentially life-threatening. Causes for maternal mortality in women with
preeclampsia include congestive heart failure, myocardial infarction, coagulopathy,
and cerebral hemorrhage. Definitive treatment is the delivery of the fetus and
placenta, after which preeclampsia usually abates within 48 hours.
34. A. The presence of hypertension with associated edema requires further workup
including complete blood count with platelets and prothrombin time/international
normalized ratio to ensure adequate hemostasis can be achieved. Usually, platelets
>100 K/ μL carry little increased risk, and one may safely proceed with epidural
placement. Platelet count <50 K/ μL is generally considered a contraindication to
neuraxial interventions due to high risk of epidural hematoma. Epidural anesthesia is
often viewed as the technique of choice for labor pain as the parturient remains
awake and alert without sedative side effects. However, systemic opiates are
reasonable if epidural is contraindicated for whatever reason, including patient
refusal. A general or regional anesthetic should not be used in attempts to lower
35. A. Transfer of drugs from mother to fetus takes place at the level of the placenta
mainly by diffusion. Thus, keeping maternal blood levels of drugs as low as possible
is a major strategy for decreasing the amount of drug that reaches the fetus. In
addition, since most of the blood in the umbilical vein travels directly to the liver, a
large portion of the drug will be metabolized before reaching vital fetal organs.
Furthermore, drug in the umbilical vein that bypasses the liver via the ductus venosus
to access the inferior vena cava will be diluted with blood from the lower extremities,
and this further reduces concentration of drugs in the fetal blood. Two things work
against these “safety features”: (1) fetal acidosis during times of distress causes
increased perfusion of the heart and brain and thus increases delivery of drug to these
important organs. (2) Fetal pH is lower than maternal pH and results in basic drugs
(such as local anesthetics) becoming more ionized when they reach fetal circulation.
This effectively traps them on the fetal side of the circulation, since ionized
molecules cannot easily cross the placenta. This also maintains a gradient for
diffusion. This is known as “ion trapping” and can be quite a significant effect
especially during times of fetal distress (when pH gets even lower).
36. B. Late decelerations are worrisome as it is a sign of fetal hypoxemia, which
requires prompt treatment. Uteroplacental resuscitation measures should be
implemented immediately in an attempt to improve uteroplacental perfusion and
oxygen delivery to the fetus. Supplemental oxygen should be provided to the mother,
and she should be placed in a lateral position to avoid aortocaval compression.
Maternal hypotension should be treated promptly with an IV fluid bolus and/or
administration of a vasopressor. In this case, phenylephrine may also improve her
tachycardia. Emergent cesarean delivery is indicated only if these utero resuscitative
measures are not successful. Discontinuation of the epidural infusion is
recommended only if the patient has an excessively high sensory level.
37. C. Definitive treatment is delivery of the fetus and placenta. In the interim,
magnesium and antihypertensive drugs may be required. Magnesium is effective by
decreasing the irritability of the CNS to decrease the risk of seizures. Though it
mildly reduces blood pressure due to its vasodilatory effect, it is not an effective
agent for severe hypertension. Antihypertensives are usually required when the
diastolic pressure is >110 mm Hg. Hydralazine and labetalol are the most commonly
administered. Hydralazine has the advantage of being a vasodilator; thus, it can
improve uteroplacental and renal blood flow. Labetalol, with its adrenergic blockade
may improve tachycardia. Keep in mind that labetalol has a much faster onset of
action (5 minutes) vs. hydralazine (30 minutes) as such may be more appropriate for
acute management of severe hypertension.
38. B. All women in the peripartum period should be given a nonparticulate antacid
such as sodium citrate 30 mL to neutralize gastric contents. A rapid-sequence
induction should be performed following adequate preoxygenation. If a woman is in
shock, etomidate is preferable to thiopental or propofol as an induction agent.
Equipotent doses of all the volatile agents depress uterine contractility to an
equivalent, dose-dependent extent. Following retained placenta, there is an increased
incidence of endometritis; however, there is no consensus opinion on whether
antibiotic prophylaxis is routinely indicated.
39. D. Epidural abscesses are associated with headache, fevers/chills, nausea/vomiting,
low back pain, and bowel or bladder dysfunction that can range from retention to
incontinence. Hematologic evaluation would likely reveal an immune response with
40. C. Since the first reported case in 1898, PDPH has been a problem for patients
following dural puncture. Research over the last 30 years has shown that use of
larger-gauge needles, particularly of the pencil-point design, is associated with a
lower risk of PDPH than larger traditional cutting-point (Quincke) needle tips. Keep
in mind that gauge and bore diameter of a needle are inversely related such that a
22G is smaller compared to a 16G. A careful history should rule out other causes of
(large bore diameter) needles.
41. B. Magnesium acts as a physiologic calcium blocker to provide uterine relaxation
in addition to electrical conduction disruption such that levels can be predicted
strength of deep-tendon reflexes. Similarly, postsuccinylcholine fasciculations are
42. B. Nitroglycerin may be used as an alternative to terbutaline sulfate (β2 agonist) or
general endotracheal anesthesia with halogenated agents for uterine relaxation.
Inhaled anesthetics produce dose-dependent uterine vasodilatation with a decrease in
uterine contractility. Uterine relaxation produced by inhalation agents may be helpful
for removal of retained placenta. However, uterine vasodilatation might lead to
increased blood loss during obstetric surgery or delivery. Nitrous oxide does not
change uterine contractility in doses provided during delivery. Initiating treatment
with incremental doses of nitroglycerin may relax the uterus sufficiently while
minimizing potential complications (e.g., hypotension).
43. A. Maternal side effects due to β2
-agonist therapy (e.g., terbutaline, ritodrine) for
tocolysis include cardiopulmonary complications (e.g., arrhythmias, tachycardia,
hypotension, and pulmonary edema) and metabolic hyperglycemia.
44. D. Alkalization of the blood causes vasoconstriction, to provide a semblance of
hemostasis. Inhaled anesthetics, ritodrine, and nitroglycerine are all potent
vasodilators that can contribute to her ongoing blood loss.
45. C. Sodium thiopental is an ultra-short-acting barbiturate commonly used to induce
general anesthesia prior to intubation. Following a low dose, the drug rapidly reaches
the brain and causes unconsciousness within 30 to 45 seconds. At 1 minute, the drug
attains a peak concentration of about 60% of the total dose in the brain. Thereafter,
the drug distributes to the rest of the body, and in about 5 to 10 minutes, the
zero-order elimination kinetics such that thiopental is not used to maintain anesthesia
in surgical procedures (T½ 11.5– 26 hours) due to slow recovery. As such, larger or
repeated doses can depress the baby.
46. B. Umbilical cord blood gas analysis is recommended in all highrisk deliveries.
For most accurate interpretation, paired umbilical arterial and venous samples should
be taken soon after birth from a segment of cord that has been doubly clamped to
isolate it from the placenta. This cord blood will remain stable for up to 1 hour.
Infants with pH <7.0 at birth who are not vigorous are at high risk of adverse
outcome. Analysis of paired arterial and venous specimens can give insights into the
etiology of the acidosis. In combination with other clinical information, normal paire
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