Lippincott's Anesthesia Review: 1001 Questions and Answers
Chapter 17. Obstetric Anesthesia
1. Beyond midgestation, pregnant women are at increased risk of gastroesophageal reflux and aspiration of gastric contents for all these reasons, except
A. Decreased competence of the lower esophageal sphincter
B. Delayed gastric emptying associated with the onset of labor
C. Delayed gastric emptying due to opioid administration
D. Increased incidence of constipation
2. Changes in the cardiovascular system associated with pregnancy include
A. Increase in central venous pressure
B. Increase in cardiac output
C. Increase in systemic vascular resistance
D. Increase in blood pressure
3. During pregnancy, the disproportionate increase in plasma volume versus erythrocyte volume accounts for
A. Increase in the mean arterial pressure
B. Increase in stroke volume
C. Increase in cardiac output
D. Relative anemia of pregnancy
4. By the third trimester of pregnancy, cardiac output increases to nearly 50% due to which of these alterations?
A. Increase in stroke volume and increase in heart rate
B. Decrease in stroke volume and increase in heart rate
C. Increase in stroke volume and decrease in heart rate
D. Decrease in stroke volume and decrease in heart rate
5. The largest increase in cardiac output is seen during this peripartum period:
A. During induction of anesthesia
B. During the start of labor
C. Immediately after delivery
D. At conception
6. A 20-year-old G1P0 female at 425 weeks of gestation presents to labor and delivery floor with rupture of membranes and onset of early labor. She appears uncomfortable and becomes extremely anxious with peripheral IV placement, and begins to hyperventilate. If allowed to continue hyperventilation, it will cause
A. Increased placental perfusion
B. Decreased maternal arterial pH
C. Increased fetal arterial pH
D. Decreased maternal uterine artery flow
7. In the above patient, labor is nonprogressive with signs of fetal distress on heart rate monitoring. Spinal anesthesia with 2-chloroprocaine 3% (2 mL) is provided for emergent cesarean section. On postpartum day 2, she complains of leg numbness, which quickly progressed to flaccid paralysis. On examination, inability to move her lower extremities with complete loss of pain and temperature sensation below T4 with normal sensation to light touch was noted. The most likely cause of this complication is
A. 2-Chloroprocaine neurotoxicity
B. Inadvertent subdural injection
C. Anterior spinal artery syndrome
D. Brown-Séquard syndrome
Questions 8 to 9
A 23-year-old female, in early labor, was transferred from an outside hospital at 37 weeks’ gestation with a history of a congenital bicuspid aortic valve. The patient reports dyspnea throughout her pregnancy, and had a recent syncopal event. Subsequently, transthoracic echocardiogram revealed a mean aortic valve gradient of 45 mm Hg and an aortic valve area of 1.2 cm2.
8. Two hours later, she endorses abdominal pain (8/10) and is requesting analgesia. The most appropriate option for her pain management during labor and delivery is
A. Spinal anesthetic with bupivacaine
B. Epidural anesthesia with adequate volume preloading
C. Inhaled nitrous oxide
D. Oral analgesics
9. Despite an appropriate increase in her cardiac output and plasma volume, her systemic blood pressure does not increase during the course of her pregnancy because of
A. Decrease in systemic vascular resistance
B. Compression of the vena cava
C. Decrease in venous capacitance
D. Decrease in heart rate
10. Iatrogenic contributions to maternal supine hypotension syndrome can be minimized by
A. Left hip elevation
B. Left-uterine displacement
C. Regional anesthesia
D. General anesthesia
11. The most significant change in maternal lung volume that occurs in the third trimester of pregnancy includes
A. Decrease in vital capacity
B. Increase in residual volume
C. Decrease in functional residual capacity (FRC)
D. Decrease in closing capacity (CC)
12. Which of the following is not associated with oxytocin administration?
A. Myocardial ischemia
B. Respiratory depression
13. During maintenance of a general inhaled anesthetic for an urgent nonobstetric surgery, one would expect this difference in the pregnant patient versus a nonpregnant patient:
A. Slower emergence from anesthesia
B. Minimal changes in depth of anesthesia
C. There is to be no difference
D. Faster induction of anesthesia
14. When providing general anesthesia during pregnancy, minimum alveolar concentration (MAC) is
15. The speed of time to hypoxia following apnea is faster in the late-trimester parturient due to all of the following factors, except
A. Reduced functional residual capacity
B. Increased minute ventilation
D. Increased oxygen consumption
16. The correct respiratory physiologic change associated with pregnancy is
A. Increase in arterial pH
B. Increase in HCO3
C. Increase in PaCO2
D. Increase in tidal volume
17. The P50 for maternal hemoglobin
A. Increases due to elevated levels of 2,3-diphosphoglycerate (DPG)
B. Remains unchanged
C. Increases to maintain pH
D. Decreases to enhance oxygen delivery to tissues
18. At sea level, the most likely arterial blood gas (ABG) sample of a parturient at 35 weeks’ gestation when she rests in the supine position breathing room air is
A. pH = 7.35, PaO2 = 90, PaCO2 = 45, HCO3 = 20
B. pH = 7.40, PaO2 = 100, PaCO2 = 40, HCO3 = 24
C. pH = 7.44, PaO2 = 90, PaCO2 = 30, HCO3 = 20
D. pH = 7.50, PaO2 = 105, PaCO2 = 30, HCO3 = 20
19. A 27-year-old G2P1 at 392 weeks’ gestation is electing to have spinal anesthesia for a repeat cesarean section. Five minutes after bupivacaine spinal injection, the patient becomes hypotensive and is complaining of tingling in her fingers with subjective difficulty breathing. Her oxygen saturation remains 100% and blood pressure is 95/55. The most likely etiology is
A. Engorgement of epidural veins contributed to inadvertent intravascular injection of the local anesthetics
B. Decrease in volume of CSF in the subarachnoid space facilitated higher spread of local anesthetics
C. Severe patient anxiety
D. Increased peripheral nerve sensitization to local anesthetics
20. During pregnancy, hepatic changes contribute to
A. Decreased albumin levels contributing to higher free blood levels of highly protein-bound drugs
B. Decreased liver function tests due to decreased blood flow
C. Decreased concentration levels of coagulation factors leading to easy bruisability
D. Decreased activity of plasma cholinesterase resulting in significantly longer duration of action of succinylcholine
Questions 21 to 23
After 18 hours of laboring and adherence to a strict nonpharmacologic natural birth plan, the patient experiences late decelerations and fetal distress, requiring emergent cesarean section.
21. To minimize the risk of aspiration and resultant pneumonitis,
A. Place patient in left-uterine displacement
B. Give H2-receptor antagonist to decrease the pH of gastric fluid present in the stomach
C. Give metoclopramide to reverse opioid-induced gastric hypomotility
D. Give a nonparticulate antacid to decrease the pH of the gastric fluid
22. The most common cause of late decelerations in fetal heart rate (FHR) (down to 90 bpm) is
A. Fetal vagal reflex
B. Compression of the fetal head
C. Umbilical cord compression
D. Fetal alkalosis
23. After performing a single-shot intrathecal anesthetic consisting of 7.5 mg of preservative-free bupivacaine and 25 μg of fentanyl, the surgical incision is made and systemic hypotension (78/44 mm Hg) ensued. To avoid significant decreases in uterine blood flow, first-line therapy to consider is
A. Provide additional inhaled nitric oxide (NO) to vasodilate the uterine vasculature
B. Increase maternal cardiac output with use of epinephrine
C. Increase intravascular volume with fluids
D. Use reverse Trendelenburg to decrease aortocaval compression
Questions 24 to 25
With increasing concern of variable decelerations, a male fetus is delivered with vacuum assistance. The amniotic fluid was noted to be meconium stained. Initial evaluation reveals a cyanotic limp infant with a heart rate of 80 bpm, poor respiratory efforts, and grimacing in response to suctioning.
24. Patient’s Apgar score would be
25. Appropriate initial steps in the resuscitation efforts would include all of the following, except
A. Tracheal suctioning
B. Provide radiant heat source
C. Positive-pressure ventilation
D. Supplemental oxygen
26. Regarding forceps-assisted delivery
A. High-forceps delivery has the highest success rate
B. Prevents clavicle fracture associated with dystocia
C. Hastens postpartum maternal recovery
D. Is associated with increased incidence of fetal facial nerve trauma
27. True statement regarding fetal circulation includes
A. The ductus venosus shunts blood away from the pulmonary circuit.
B. Deoxygenated blood is carried in the umbilical vein.
C. The foramen ovale shunts blood from right to left ventricles.
D. Intracardiac pressures are equalized across both right and left ventricles.
28. Successful transition from fetal to neonatal circulation is required after birth to support extrauterine life. This depends primarily on these factors, except
A. Removal of the placenta
B. Decreased systemic vascular resistance
C. Decreased pulmonary vascular resistance
D. Closure of the intra- and extracardiac shunts
29. In considering placental exchange and fetal uptake, all statements are true, except
A. Minimizing the maternal blood concentrations of a drug is the most important method of limiting the amount that ultimately reaches the fetus
B. Drugs that readily cross the blood–brain barrier will also cross the placenta
C. Placental exchange of substance occurs principally via ion transport from the maternal circulation to the fetus
D. Ion trapping explains why fetal-to-maternal lidocaine ratios are higher during fetal acidemia than during normal fetal well-being
30. Which of the following best explains why lidocaine has a higher fetal-to-maternal plasma ratio when compared with bupivacaine?
A. Bupivacaine has a smaller molecular weight
B. Lidocaine has higher protein-binding
C. Bupivacaine has a lower dissociation constant (pKa)
D. Lidocaine is less lipid soluble
31. In order to provide analgesia for all stages of labor, one must accommodate the evolving and varied course of labor and delivery. The least accurate statement regarding the anatomy of labor is
A. Pain during labor and delivery is often described in two stages
B. Somatic and visceral innervation of the uterus and cervix enters the spinal cord via T10 to L1
C. Innervation of the perineum is primarily via the pudendal nerve
D. Somatic and visceral afferent sensory fibers from the uterus and cervix travel with greater, lesser, and least splanchnic nerves via the celiac plexus
32. The regional or neuraxial technique that would not be expected to provide appropriate analgesic benefit during the first stage of labor is
A. Lumbar epidural
B. Pudendal nerve block
C. Lumbar sympathetic block
D. Paracervical block
Questions 33 to 37
A 37-year-old G9P4 patient at 38 weeks of gestation presents for management of labor and delivery. She denies any medical history and admits to minimal prenatal care. The patient is moderately hypertensive (160/95) with associated pitting edema at her ankles.
33. The statement about her disorder that is most likely true is
A. Eclampsia is imminent
B. Preeclampsia is a syndrome manifested after the 36th week of gestation
C. HELLP syndrome is the mildest form of eclampsia
D. Definitive treatment of preeclampsia is delivery of the fetus and placenta
34. The patient is started on oxytocin to augment her labor, and the patient is now requesting a labor epidural. Anesthetic considerations include
A. The presence of hypertension and edema requires further workup before proceeding
B. No workup is required prior to performing epidural anesthesia, as this will treat her hypertension
C. Neuraxial anesthesia should be avoided, as there is increased risk of bleeding
D. Avoid systemic opiates, as the risk of respiratory depression is too high
35. After a review of her laboratory results, a lumbar (L3–L4) epidural was placed without incident (including lack of CSF, and negative test dose after administration of 45 mg lidocaine with 1:200,000 epinephrine). Epidural anesthesia is then initiated with a bolus of 15 mg of bupivacaine. Variable decelerations are noted minutes later on fetal heart rate monitoring. If scalp pH reveals fetal acidosis, compared with a normal pH, the anesthetic absorbed by the fetus will be present in
A. Higher concentration, most in ionized form
B. Lower concentration, most in ionized form
C. Higher concentration, most in unionized form
D. Unchanged concentration, equal fraction of ionized and nonionized
36. The patient has now been receiving a dilute infusion (bupivacaine 0.125% with 2 μg/mL fentanyl) for the past 3 hours and reports good pain relief with a bilateral T5 sensory level. Her blood pressure is now 85/45 mm Hg, and her heart rate is 120 bpm. The fetal heart rate pattern begins to show late decelerations. The most appropriate management in this patient includes
A. Immediate bedside cesarean delivery
B. Administration of phenylephrine
C. Administration of ephedrine
D. Discontinuation of the epidural infusion
37. As augmentation of labor continues, patient’s blood pressure slowly climbs again, with waning epidural analgesic benefit. Highest pressure was noted to be 166/112 mm Hg with heart rate sustained over 100 bpm. The most appropriate pharmacologic option for acute treatment of severe hypertension in a preeclamptic patient is
38. Four hours postdelivery, and after the epidural is removed, the patient now requires emergent anesthesia for surgical removal of retained placental products. The appropriate anesthetic management includes all of the following, except
A. Antibiotic administration
B. Total intravenous anesthesia
C. General endotracheal inhaled anesthetic
D. Sodium citrate
39. Forty-eight hours postdelivery, the patient is febrile, complaining of chills with severe occipital and neck pain worsened with sitting and standing, but not improved when lying in bed. The finding you would not expect to find on examination is
A. Urinary retention
B. Low back pain
C. Nausea and vomiting
D. Normal white blood cell (WBC) count
40. Postdural puncture headache (PDPH) occurs more frequently
A. In elderly (>50 year old) vs. young patients
B. In underweight vs. overweight patients
C. With a cutting-point vs. pencil-point spinal needles
D. With larger- vs. smaller-gauge spinal needles
41. Decrease in fasciculations can be seen following induction doses of succinylcholine for emergent cesarean section. The factor that can blunt this response is
A. Increased cardiac output
B. Prior magnesium administration
C. Prior nitrous oxide inhalation
D. Metabolic alkalosis
42. Administration of all the following will provide uterine relaxation, except
B. Nitrous oxide
43. Adverse effects of inhaled β-tocolytic therapy for preterm labor to the mother include all of the following, except
B. Pulmonary edema
D. Ventricular arrhythmias
44. During a general anesthetic for emergent cesarean section, administering of all of the following could contribute to increased operative blood loss, except
B. Ritodrine intravenously
C. 1 MAC Desflurane
45. With regard to sodium thiopental, the following statements are accurate, except
A. Peak concentration in the brain occurs at 1 minute postinjection
B. Rapid redistribution allows for return of consciousness in <10 minutes
C. Infusions maintain appropriate surgical conditions with fast recovery due to ultra-short action
D. Repeating the induction dose results in fetal depression
46. The following statements are true regarding umbilical cord blood, except
A. Provides a picture of the acid–base balance in the infant at the moment of birth
B. Double clamping of the umbilical cord at birth will preserve a segment of cord blood in isolation, which can remain stable for up to 24 hours
C. Cord blood that is still in continuity with the placenta will have shifting acid–base balance due to ongoing placental metabolism and gas exchange
D. Normal paired arterial and venous specimens can provide evidence against an intrapartum hypoxic–ischemic event to the newborn
47. Maternally administered drugs that decrease beat-to-beat variability of fetal heart rate include all of the following, except
48. A 24-year-old G4P2 parturient is undergoing a general anesthetic for emergency cesarean section due to uterine rupture. All these findings would suggest an amniotic fluid embolism (AFE), except
A. Decreased EtCO2
B. Increased maternal pH
C. Bleeding diathesis
D. Upsloping EtCO2 tracing
49. A 42-year-old G1P0 at 294 weeks’ gestation is undergoing intracranial clipping of a large arteriovenous malformation, following sudden onset of a severe headache with associated nausea/vomiting. Patient is intubated in the interventional radiology suite and ventilated with settings of TV = 500 mL, respiratory rate = 14 bpm, PEEP = 5 cm H2O, and FIO2 = 1.0. Arterial blood gas (ABG) 30 minutes later reveals pH = 7.55, PaO2 = 502, PaCO2 = 19, and HCO3 = 21. These findings are associated with all of the following, except
A. Decreased fetal cerebral oxygen delivery
B. Decreased placental transfer of oxygen
C. Rightward shift of the oxygen dissociation curve
D. Decreased umbilical blood flow
50. True statement concerning hyperglycemia during pregnancy is
A. Increases risk of fetal microsomia
B. Fetal oxygen requirements remain decreased
C. May contribute to neonatal hypoglycemia
D. Increases risk of sepsis during cesarean delivery
51. True statement regarding neuraxial opioids for labor and delivery is
A. Opioids should never be used as a sole agent
B. Most common side effect is fetal bradycardia
C. Intrathecal morphine is associated with quick peak in concentration and early onset maternal respiratory depression
D. Systemic absorption is similar to intramuscular (IM) administration
52. All of the following drugs readily cross the placenta, except
A. β-Agonist antagonists
B. Local anesthetics
53. Following a 0.6 mg/kg intravenous dose of rocuronium to facilitate rapid-sequence induction in a parturient requiring surgical delivery, one would expect
A. Minimal placental transfer of rocuronium to the newborn
B. Shorter duration of relaxation with concurrent magnesium administration
C. Unsuitable intubating conditions as recommended doses are 1.5 mg/kg
D. Use of rocuronium has been shown to affect Apgar scores and fetal muscle tone at birth and should be strictly avoided
54. During cesarean section under general endotracheal anesthesia, venous air embolism (VAE)
A. Is associated with high end-tidal CO2
B. Should be treated with nitrous oxide
C. Is associated with expired nitrogen
D. Induces severe hypertension
Questions 55 to 58
A 30-year-old otherwise-healthy G2P0 (167 cm, 68 kg) presents at 341 weeks’ gestation with the rupture of membranes, single footling in breech presentation with fetal bradycardia. The decision for emergent cesarean delivery under general anesthesia is made, and the patient is quickly prepared for a rapid sequence induction. However, patient’s larynx is noted to be very anterior, and is unable to be intubated after multiple direct laryngoscopy attempts.
55. The appropriate next step considering persistent fetal bradycardia (<80 bpm) is
A. Administer 1 mg/kg of rocuronium intravenously
B. Use bag-mask ventilation and allow surgical delivery to proceed
C. Wake the patient up for awake fiberoptic intubation
D. Reposition the patient in Trendelenburg with left-uterine displacement
56. The fetus is quickly delivered (skin-to-skin time of 18 minutes). However, 10 minutes after delivery, her uterus is noted to be boggy and bleeding persists. The appropriate treatment option is
A. Bolus oxytocin (Pitocin) 20 U intravenously
B. Bolus methylergonovine (Methergine) 0.2 mg intravenously
C. Misoprostol (Cytotec) 800 mg intramuscularly
D. 15-Methyl PGF2α (Hemabate) 0.25 mg intramuscularly
57. Two hours later, the patient remains apneic and intubated in the intensive care unit. She is sedated and mechanically ventilated (TV = 450, RR = 12, FIO2 = 0.4) with the arterial blood gas revealing a pH of 7.45, PaO2 of 100 mm Hg, and PaCO2 of 37 mm Hg with a base excess of zero. Her examination reveals absent deep-tendon reflexes throughout. ECG reveals intermittent ventricular bigeminy. This situation could be explained by
B. Severe hypovolemic shock
D. Pituitary necrosis
58. At 3 weeks’ postpartum, the patient has absence of lactation and denies return of her menstrual cycle. Review of systems is positive for intolerance to cold, constipation, hair loss, and 2-pound weight gain. The best explanation for this constellation of symptoms is
A. Amenorrhea–galactorrhea syndrome
B. Sheehan syndrome
D. Meigs syndrome
CHAPTER 17 ANSWERS
1. D. Increasing levels of progesterone along with an enlarging uterus contributes to incompetence of the lower esophageal sphincter placing parturients at increased risk of aspiration. This risk increases further as delayed gastric emptying is associated with both the onset of labor (sympathetic effects) and μ-opioid administration for analgesia. Aspiration precautions must be utilized when providing anesthesia for women beyond midgestation.
2. B. During pregnancy, cardiovascular changes include increase in blood volume, plasma volume, cardiac output, stroke volume, and heart rate. Despite these increases, the systemic blood pressure, during a normal uncomplicated pregnancy, does not increase due to decrease in systemic vascular resistance. Similarly, there is no change in central venous pressures despite the increase in plasma volume due to increase in venous capacitance (Table 17-1).
Table 17-1 Normal Hemodynamic Changes during Pregnancy
Increase of 50%
Increase of 10–15 bpm
Decrease of 10 mm Hg
Increase—1st and 2nd trimester
Increase of 300 mL/contraction
Increase of 30%–50%
Additional increase of 50%
Systemic vascular resistance
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 fetal metabolic demands.
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 levels 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 supply.
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 lesion also contributes.
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 unchanged.
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 in depth of anesthesia.
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 buffer.
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 oxygen delivery to tissues.
18. C. An increased metabolic rate in addition to the pregnancy-induced increase in minute ventilation results in a markedly decrease in PaCO2 from 40 to 30 mm Hg. Such that a PaCO2 of 40 to 45 on ABG would indicate CO2retention. However, 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 for neuraxial procedures.
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-receptor antagonists, unlike 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 neonatal outcome.
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 17-4).
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. The closer the pKa is to the physiologic pH, the more it will be affected by the acid–base status of the fetus.
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 the pudendal nerve (S2–S4).
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 maternal blood pressure.
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 elevated WBC.
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 headache. A postdural component of headache is the sine qua non of PDPH. High-risk patients include those <50 years, postpartum, and puncture with small gauge (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 blunted.
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 concentration is low enough in the brain such that consciousness returns. Thus, a one-time bolus displays first-order kinetics. Larger doses, or infusions, undergo slow 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 high〿risk 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 paired arterial and venous cord blood gas results can usually provide a robust defense against a suggestion that an infant had an intrapartum hypoxic–ischemic event.
47. A. The fetal heart rate varies beat to beat, with a normal heart rate ranging between 110 and 160 bpm. This normal variability is thought to reflect the integrity of the vagal neural pathway from the fetal cerebral cortex to the cardiac conduction system. Fetal well-being is safeguarded when this beat-to-beat variability is present. Conversely, fetal distress is associated with minimal (or absent) variability of the fetal heart rate. Opioids, benzodiazepines, sedative-hypnotics, local anesthetics, phenothiazines, and anticholinergics administered to the mother have been shown to eliminate or reduce this variability, even in the absence of distress. This drug-related effect does not appear to be deleterious, but may cause difficulty in interpreting fetal heart rate monitors.
48. B. Normally, amniotic fluid does not enter the maternal circulation because it is contained safely within the uterus, sealed off by the amniotic sac. An AFE occurs when the barrier between amniotic fluid and maternal circulation is broken, allowing it to abnormally enter the maternal venous system. The devastating consequence of circulating fetal debris (carried by amniotic fluid) occurs only rarely. Newer theories contend that AFE more closely resembles an anaphylactic reaction to fetal debris rather than a true embolic event. Cardinal signs include bronchospasm/wheezing, hypoxemia, shock/maternal acidosis, coagulopathy/disseminated intravascular coagulation, and altered mental status.
49. C. Hyperventilation and hypocapnia have profound effects on cerebral blood flow (CBF), resulting in a 2% decline in CBF for each 1 torr decline in PaCO2. In the same manner, low CO2 concentrations will cause vasoconstriction of the uterine vessels impairing uterine blood flow. In addition, maternal hypocapnia will shift the oxyhemoglobin dissociation curve to the left, further impairing oxygen release and transfer to the fetus. Carbon dioxide tensions in arterial blood plays an important role in determining blood flow and delivery to the pregnant uterus; hypocarbia can lead to poor oxygen and nutrient delivery with a resulting fetal hypoxic distress (Fig 17-5).
50. D. Hyperglycemia during pregnancy contriXbutes to higher birth weights (macrosomia) with cephalopelvic insufficiency and shoulder dystocia requiring surgical delivery via cesarean section. Fetal hyperglycemia induces fetal hyperinsulinemia, resulting in elevated metabolic rates that lead to increased oxygen demand, risking ischemia. This hypoxemia in turn contributes to the development of a metabolic acidosis and may trigger polycythemia with increased production of red blood cells. At birth, however, with separation from the maternal hyperglycemic circulation, neonatal hypoglycemia develops secondary to high levels of neonatal insulin.
51. D. Opioids can be added to local anesthetics or alternatively can be used as a sole agent (epidural or intrathecal) to provide peripartum analgesia. Side effects of neuraxial opioids include pruritus, nausea/vomiting, hypotension, urinary retention, fetal bradycardia, and maternal respiratory depression. Among these, pruritus occurs most commonly. The epidural space contains an extensive vascular plexus with extensive systemic absorption such that absorption of epidural morphine, fentanyl, or sufentanil produces opioid serum concentrations that are similar to an equivalent dose of IM injection.
52. C. Glycopyrrolate, insulin, heparin, and neuromuscular blockers are unable to cross the placenta, whereas opioids, local anesthetics, atropine, ephedrine, and β-blockers readily cross the placenta to enter the neonatal circulation.
53. A. Reversal of neuromuscular blockade may be unsatisfactory in patients receiving magnesium for preeclampsia as magnesium can enhance the neuromuscular blockade. Though doses of 1 mg/kg have been used safely for rapid sequence induction of anesthesia, this dose has not been tested for safety in pregnancy. Therefore, only a dose of 0.6 mg/kg is recommended in this patient population despite the knowledge that rocuronium (similar to all paralytics) does not readily cross the placental barrier, as evidenced by low umbilical-to-venous plasma concentrations.
54. C. VAE has a very high incidence during cesarean sections secondary to entrainment of room air from ruptured or severed veins. The sudden development of hypotension, hypoxia, and a drop in end-tidal CO2 suggests the presence of a VAE. Supportive therapy includes flooding the surgical field with normal saline and placing the patient in Trendelenburg position with a left-lateral tilt. Medical gases such as carbon dioxide, nitrous oxide, and helium will aggravate this condition by expanding the pulmonary vascular bubbles that can create an air lock with mechanical flow obstruction. If central venous catheter or pulmonary artery catheter is in place, the trapped air may be aspirated. Expired nitrogen is the most sensitive VAE-detection method, as the largest component of air is nitrogen.
55. B. General anesthesia is used most commonly in emergency surgical deliveries for fetal distress. Endotracheal intubation following rapid-sequence induction remains the principal approach. Pregnancy-related features (obesity, enlarging breasts, short neck) make intubation challenging such that inability to intubate the trachea is a major cause of morbidity and mortality. Current opinion is that after two failed attempts at direct laryngoscopy, one should proceed with surgery as repeated trauma and edema may prevent ability to ventilate as well. Severe fetal distress requires emergent delivery as opposed to preparing for an awake fiberoptic intubation.
56. D. 15-Methyl PGF2α is a smooth-muscle constrictor with additional sites of action on bronchial smooth muscles, which may promote bronchospasm. Direct intravenous bolus injection of oxytocin (>5 units) has been associated with maternal hypotension and death, thus should only be infused over time in a dilute solution (e.g., 40 units/L). Methylergonovine is a potent vasoconstrictor that can cause vasospasm and severe hypertension if given intravenously, such as usual administration intramuscularly. Misoprostol is a prostaglandin analog that can be given up to 1 mg rectally or sublingually, but is to be used with caution in patients under general anesthesia due to aspiration risk.
57. A. Overdose of magnesium during the peripartum period can lead to arreflexia and cardiac conduction abnormalities, resulting in bradycardia and ectopy. Metabolic acidosis would be seen in cases of severe hypovolemic shock. Examination findings expected with hypocalcemia would include hyperreflexia, as opposed to arreflexia.
58. B. During pregnancy, hypertrophy and hyperplasia of lactotrophs result in enlargement of the anterior pituitary, but without a corresponding increase in blood supply. As such, major hemorrhage or hypotension during labor and delivery can result in anterior pituitary ischemia and necrosis. Sheehan syndrome specifically is hypopituitarism caused by ischemic necrosis during the peripartum period.