OB review questions Flashcards
643–Which of the following drugs does NOT pass the placenta easily?
A. Etomidate
B. Ephedrine
C. Atropine
D. Glycopyrrolate
D) glycopyrrolate
The fetal/maternal (F/M) drug ratio is a way to quantitatively describe drug transfer across the placenta. Time is also important when considering how much drug crosses into the fetus. Many anesthetic drugs cross the placenta such as local anesthetics, intravenous induction agents (e.g., propofol [F/M ratio of 0.7- 1.1], etomidate [F/M ratio of 0.5], ketamine [F/M ratio of 0.5]), inhalation agents (e.g., volatile anesthetics and nitrous oxide [F/M ratio of 0.7]), and narcotics (e.g., fentanyl [F/M ratio of 0.4], remifentanil [F/M ratio of 0.9], morphine [F/M ratio of 0.6]) and with time may affect the fetus/newborn. For vasopressors, ephedrine has an F/M ratio of 0.7, whereas phenylephrine has an F/M ratio of 0.2. The ionized neuromuscular blocking agents do not readily cross the placenta (F/M ratios of non-depolarizing drugs are around 0.1-0.2); succinylcholine, a depolarizing muscle relaxant, crosses very poorly as well. The anticholinergic drugs atropine and scopolamine have F/M drug ratios of 1.0 and readily cross the placenta, whereas glycopyrrolate has an F/M drug ratio of 0.1 and poorly crosses the placenta. Because the anticholinesterase agents (neostigmine, pyridostigmine, and edrophonium) cross the placenta to a limited extent but more so than glycopyrrolate, a pregnant patient undergoing nonobstetric surgery in which neuromuscular blocking drugs are being reversed with anticholinesterase agents should have atropine rather than glycopyrrolate used with the anticholinesterase mixture to prevent possible fetal bradycardia (Chestnut: Chestnut’s Obstetric Anesthesia, ed 5, pp 63–69; Suresh: Shnider and Levinson’s Anesthesia for Obstetrics, ed 5, pp 47–51).
- What is the P50 of fetal hemoglobin at term?
A. 12
B. 18
C. 24
D. 30
(B) Newborns have high hemoglobin levels around 15 to 20 g/100 mL. The term P50 denotes the blood oxygen tension (Pao2) that produces 50% saturation of erythrocyte hemoglobin. The P50 value of fetal hemoglobin is 18 mm Hg versus the adult value of 27 mm Hg. Thus, fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin (Chestnut: Chestnut’s Obstetric Anesthesia, ed 5, pp 83–84; Suresh: Shnider and Levinson’s Anesthesia for Obstetrics, ed 5, pp 26–27).
653–Cardiac output increases dramatically during pregnancy and delivery. The cardiac output returns to nonpregnant values by how long postpartum?
A. 12 hours
B.1day
C. 2 weeks
D. 6 months
(C) 2 weeks
The numerous changes that take place in the cardiovascular system during pregnancy provide for the needs of the fetus and prepare the mother for labor and delivery. During the first trimester of pregnancy, cardiac output increases by approximately 30% to 40%. At term, the cardiac output is increased 50% over nonpregnant values. This increase in cardiac output is due to an increase in stroke volume and an increase in heart rate. During labor, the cardiac output increases another 10% to 15% during the latent phase, 25% to 30% during the active phase, and 40% to 45% during the expulsive stage. Each uterine contraction increases the cardiac output by about 10% to 25%. The greatest increase in cardiac output occurs immediately after delivery of the newborn, when the cardiac output can increase to 75% above prelabor values. This final increase in cardiac output is attributed primarily to autotransfusion and increased venous return associated with uterine involution. Cardiac output falls to prelabor values within 2 days after delivery; however, it takes about 2 weeks for the cardiac output to decrease to non- pregnant values (Chestnut: Chestnut’s Obstetric Anesthesia, ed 5, pp 16–18; Suresh: Shnider and Levinson’s Anesthesia for Obstetrics, ed 5, pp 1–2).
655–Uterine blood flow at term pregnancy typically increases to about
A. 100 mL/min
B. 250 mL/min
C. 500 mL/min
D. 750 mL/min
(D) 750
Uterine blood flow increases dramatically from 50 to 100 mL/min before pregnancy to about 700 to 900 mL/min at term (i.e., >1 unit of blood per minute). From 70% to 90% of the uterine blood flow at term goes to the intervillous spaces. Uterine blood flow is related to the perfusion pressure (uterine arterial pressure minus uterine venous pressure) divided by the uterine vascular resistance. Thus, factors that decrease uterine blood flow include systemic hypotension, aortocaval compression, uterine contraction, and vasoconstriction (Chestnut: Chestnut’s Obstetric Anesthesia, ed 5, pp 40–42; Suresh: Shnider and Levinson’s Anesthesia for Obstetrics, ed 5, pp 23–24).
656
657–Which of the following cardiovascular parameters is decreased at term?
A. Central venous pressure
B. Pulmonary capillary wedge pressure
C. Systemic vascular resistance
D. Left ventricular end-systolic volume
(C) There is no change in central venous pressure, pulmonary capillary wedge pressure, pulmonary artery diastolic pressure, or left ventricular end-systolic volume. Left ventricular end-diastolic volume is increased, as is stroke volume, ejection fraction, heart rate, and cardiac output. Systemic vascular resistance is decreased about 20% (Chestnut: Chestnut’s Obstetric Anesthesia, ed 5, pp 16–19; Suresh: Shnider and Levinson’s Anesthesia for Obstetrics, ed 5, pp 1–3).
- Which of the following drugs does NOT pass the placenta easily?
A. Etomidate
B. Ephedrine
C. Atropine
D. Glycopyrrolate
(D)The fetal/maternal (F/M) drug ratio is a way to quantitatively describe drug transfer across the placenta. Time is also important when considering how much drug crosses into the fetus. Many anesthetic drugs cross the placenta, such as local anesthetics, IV induction agents (e.g., propofol [F/M ratio of 0.7-1.1], etomidate [F/M ratio of 0.5], ketamine [F/M ratio of 0.5]), inhalation agents (e.g., volatile anesthetics and nitrous oxide [F/M ratio of 0.7]), and narcotics (e.g., fentanyl [F/M ratio of 0.4], remifentanil [F/M ratio of 0.9], morphine [F/M ratio of 0.6]) and with time may affect the fetus/newborn. For vasopressors, ephedrine has an F/M ratio of 0.7, whereas phenylephrine has an F/M ratio of 0.2. The ionized neuromuscular blocking agents do not readily cross the placenta (F/M ratios of nondepolarizing drugs are around 0.1-0.2); succinylcholine, a depolarizing muscle relaxant, crosses very poorly as well. The anticholinergic drugs atropine and scopolamine have F/M drug ratios of 1.0 and readily cross the placenta, whereas glycopyrrolate has an F/M drug ratio of 0.1 and poorly crosses the placenta. Because the anticholinesterase agents (neostigmine, pyridostigmine, and edrophonium) cross the placenta to a limited extent but more so than glycopyrrolate, a pregnant patient undergoing nonobstetric surgery in which neuromuscular blocking drugs are being reversed with anticholinesterase agents should have atropine rather than glycopyrrolate used with the anticholinesterase mixture to prevent possible fetal bradycardia
- A 38-year-old obese patient is receiving subcutaneous low-molecular-weight heparin (LMWH) for thromboprophylaxis. Her epidural for an elective cesarean delivery was placed 14 hours after the heparin was stopped. She developed Horner syndrome on the left side 30 minutes after placement of the epidural. On physical examination, a T4 anesthetic level is noted, but aside from the Horner syndrome no other findings are revealed. The most appropriate course of action at this time would be to
A. Remove the epidural
B. Consult a neurosurgeon
C. Obtain a computed tomographic scan
D. None of the above
(D)LMWHs are used for both prophylaxis and treatment of arterial and venous thromboembolism. The elimination half-life of LMWH is 3 to 6 hours after subcutaneous injection in patients with normal renal function. With severe renal insufficiency, the half-life of LMWH can be up to 16 hours. At least 12 hours should elapse before performing any neuraxial techniques (e.g., placement or removal of an epidural catheter) to decrease the likelihood of a spinal hematoma forming after low-dose prophylaxis with LMWH (e.g., enoxaparin 30mg BID or 40mg once daily). If high-dose LMWH is used for therapeutic anticoagulation (e.g., enoxaparin 1mg/kg BID or 1.5mg/kg once daily), you should wait at least 24 hours to decrease the likelihood of a spinal hematoma forming. A postprocedure dose of enoxaparin should usually be given no sooner than 4 hours after epidural catheter is removed. In all cases, the benefit-risk of thrombosis and bleeding should be made. If the patient has back pain and unexpected neurologic paralysis, a workup for an epidural hematoma should be performed. This case demonstrates a benign condition in which the sympathetic nerve supply to the eye is blocked (Horner syndrome [triad of miosis, ptosis, and anhidrosis]). This occasionally develops after a lumbar epidural anesthetic, even when the highest dermatome level blocked is below T5. It may be related to the superficial anatomic location of the descending spinal sympathetic fibers that lie just below the spinal pia of the dorsolateral funiculus (which is within diffusion range of subanesthetic concentrations of local anesthetics in the cerebrospinal fluid) as well as increased sensitivity to local anesthetics during pregnancy
- What percentage of all pregnancies is affected by hypertension?
A. 3%-5%
B. 7%-10%
C. 15%
D. 20%
(B)Hypertension is defined as a systolic blood pressure (SBP) ≧140mm Hg or diastolic blood pressure (DBP) ≧90mm Hg on two occasions at least 4 hours apart, while the patient is at bed rest (unless antihypertensive therapy has been started); it occurs in 7% to 10% of all pregnancies worldwide. If the SBP is ≧160mm Hg or the DBP is ≧110mm Hg, the two readings can be done within a few minutes and antihypertensive medications can be started. Hypertension is a leading cause of maternal death worldwide. Hypertension during pregnancy is divided into four groups: preeclampsia-eclampsia, chronic hypertension (of any cause), chronic hypertension with superimposed preeclampsia, and gestational hypertension.
- A 16-year-old, anxious, preeclamptic patient in active labor develops back pain after the placement of an epidural for labor analgesia. The pain is severe, and the patient has more weakness of the legs than expected. The most appropriate course of action at this time would be to
A. Inject a higher concentration of a local anesthetic or add intravenous (IV) narcotics
B. Replace the epidural and use epidural narcotics to decrease the motor weakness
C. Reassure her that she will get better with delivery
D. Consult a neurosurgeon
(D)Epidural hematomas and epidural abscesses are quite rare. Severe back pain and/or leg weakness that is greater than expected (or the recurrence of weakness after partial recovery of a neuraxial block) are presenting symptoms of spinal cord compression. Epidural hematomas can develop within 12 hours of a neuraxial procedure, whereas epidural abscesses usually take days to develop and also present with fever and leukocytosis. These conditions need imaging (e.g., magnetic resonance imaging [MRI]) and neurosurgical consultation. Studies have shown that when spinal cord decompression occurs within 8 hours of the onset of paralysis, neurologic recovery is significantly better than after 8 hours. Although epidural hematoma formation is rare, clotting disorders and perhaps marked difficulty in placing a block could lead to epidural bleeding and hematoma formation. Because the preeclamptic patient may develop a coagulopathy, one should carefully evaluate her coagulation status before initiating a regional block. Most anesthesiologists would evaluate a platelet count in the preeclamptic patient and look for any clinical signs of unexplained bleeding before initiating a regional block. Because an epidural blood patch often is performed with 20mL of blood, the epidural hematoma that causes spinal cord compression is probably significantly greater
- Magnesium sulfate (MgSO4) is used as an anticonvulsant in patients with preeclampsia and for fetal neuroprotection and sometimes for short-term tocolysis. MgSO4 may produce any of the following effects EXCEPT
A. Sedation
B. Respiratory paralysis
C. Inhibition of acetylcholine (ACh) release at the myoneural junction
D. Hypertension when used with nifedipine
(D)The normal serum magnesium level is 1.5 to 2mEq/L, with a therapeutic range of 4 to 8mEq/L. Note: many laboratories report values in mg/dL (1mEq/L = 1.2mg/dL). As magnesium sulfate is administered IV, patients often note a warm feeling in the vein as well as some sedation. With increasing serum levels, loss of deep tendon reflexes occurs at 10mEq/L (12mg/dL), respiratory paralysis occurs at 15mEq/L (18mg/dL), and cardiac arrest at greater than 25mEq/L (>30mg/dL) can occur. Magnesium decreases the release of ACh at the myoneural junction and decreases the sensitivity of the motor endplate to ACh. This can produce marked potentiation of nondepolarizing muscle relaxants. The effect on depolarizing muscle relaxants is less clear, and most clinicians use standard intubating doses of succinylcholine (i.e., 1-1.5mg/kg) followed by a markedly reduced dose of a nondepolarizing relaxant if needed. Because magnesium antagonizes the effects of α-adrenergic agonists, ephedrine is usually preferred over phenylephrine if a vasopressor is needed to restore blood pressure, along with fluids, after a neuraxial blockade. When a calcium channel blocker, such as nifedipine, is administered along with magnesium, greater hypotension has resulted. The antidote for magnesium toxicity is calcium (which, if needed, should be administered slowly)
- Normal fetal heart rate (FHR) is
A. 60 to 100 beats/min
B. 90 to 130 beats/min
C. 110 to 160 beats/min
D. 150 to 200 beats/min
(C)Fetal monitors consist of a two-channel recorder for simultaneous recording of FHR and uterine activity. In looking at the FHR, one assesses the baseline rate, the FHR variability, and the periodic changes (accelerations or decelerations) that occur with uterine contractions. The normal FHR varies between 110 and 160beats/min. See also Answer 703
- Which of the following is the MOST likely cause of pregnancy-related deaths in the United States (2011-2013)?
A. Anesthesia complications
B. Hemorrhage
C. Cardiovascular disease
D. Hypertensive disorders of pregnancy
(C)Worldwide, hemorrhage (H), infection (I), and hypertensive disorders of pregnancy (preeclampsia [P]), or HIP, account for more than half of all maternal deaths. In the developed world, hypertensive disorders, infection, and hemorrhage account for about one third of maternal deaths. The rate of pregnancy-related mortality in the United States has been increasing from 7.2 deaths per 100,000 live births in 1987, to 14.5 deaths per 100,000 live births in 2000, to 17.3 deaths per 100,000 live births in 2013. The reason for the increase in deaths is unclear but may be related to more pregnant women having chronic health conditions such as hypertension, diabetes, obesity, and heart disease. The causes of pregnancy-related deaths in the United States for the years 2011 to 2013 were cardiovascular disease (15.5%), noncardiovascular disease (14.5%), infection or sepsis (12.7%), hemorrhage (11.4%), cardiomyopathy (11%), thrombotic pulmonary embolism (9.2%), hypertensive disorders of pregnancy (7.4%), cerebrovascular accidents (6.6%), amniotic fluid embolus (AFE) (5.5%), anesthesia complications (0.2%), and unknown causes (6.1%)
- Drugs useful in the treatment of uterine atony in an asthmatic patient with severe preeclampsia include
A. Oxytocin (Pitocin) only
B. Ergonovine (Ergotrate) or methylergonovine (Methergine) only
C. 15-Methyl prostaglandin F2α (PGF2α) (Carboprost, Hemabate) only
D. All of the above are safe and can be used alone or in combination with the others
(A)Uterine atony is a common cause of postpartum hemorrhage (2%-5% of all vaginal deliveries). Treatment consists of uterine massage, drugs, and, in some cases, tamponade balloon placement (e.g., Bakri with 300-500mL normal saline), uterine artery embolization, laparotomy with hemostatic sutures, or, in rare cases, hysterectomy. Drugs commonly used include oxytocin, ergot alkaloids (ergonovine, methylergonovine), prostaglandins (PGE2, PGF2α, 15-methyl PGF2α), and misoprostol. Oxytocin (Pitocin) is the first-line drug used for the treatment of uterine atony and may be used in patients with asthma or hypertensive disorders of pregnancy. If oxytocin is given as a large IV bolus, vasodilation and hypotension often result. Oxytocin is often given as 3 units over 30 seconds every 3 minutes for 3 doses or 30 units in 500mL of fluid over 2 hours or 10 units IM. The ergot alkaloids are associated with a high incidence of nausea and vomiting. They cause vasoconstriction, producing elevations in blood pressure, and are contraindicated in patients with hypertension (and in this case preeclampsia). The dose of Methergine is 0.2mg IM every 2 to 4 hours up to 5 doses. Ergot alkaloids have also been associated with bronchospasm (rarely) and may not be appropriate in asthmatic patients. Thus the ergot alkaloids are relatively contraindicated in patients with hypertension (such as preeclampsia), coronary artery disease, and asthma. The prostaglandin 15-methyl PGF2α (Carboprost, Hemabate) is the only prostaglandin currently approved for uterine atony in the United States and may cause significant bronchospasm in susceptible patients and is contraindicated in asthmatic patients. The dose of Hemabate is 0.25mg IM every 15 to 90 minutes up to 2mg. Other smooth muscle contraction-associated side effects of prostaglandin 15-methyl PGF2α include venoconstriction, as well as gastrointestinal (GI) muscle spasm (nausea, vomiting, and diarrhea). The prostaglandin E1 misoprostol (Cytotec) has been given (off label) for postpartum hemorrhage. Misoprostol can be given once rectally (800-1000mcg) or sublingually or orally (600-800mcg) and is used if oxytocin or ergot alkaloids are ineffective. In some cases, tranexamic acid 1000mg IV is given if blood loss is expected to be >500 to 1000mL over anticipated blood loss
- What is the P50 of fetal hemoglobin at term?
A. 12 mm Hg
B. 18 mm Hg
C. 24 mm Hg
D. 30 mm Hg
(B)Newborns have high hemoglobin levels around 15 to 20g/100mL. The term P50 denotes the blood oxygen tension (Pao2) that produces 50% saturation of erythrocyte hemoglobin. The P50 value of fetal hemoglobin is 18mm Hg versus the adult value of 27mm Hg. Thus fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin
- Side effects of terbutaline include all of the following EXCEPT
A. Hypertension
B. Hyperglycemia
C. Pulmonary edema
D. Hypokalemia
(A)Terbutaline is a β-adrenergic agonist with tocolytic properties and can be administered IV and subcutaneously, as well as orally. Side effects are similar to those of other β-adrenergic drugs and include tachycardia, hypotension, myocardial ischemia, pulmonary edema (0.3% incidence), hypoxemia (inhibition of hypoxic pulmonary vasoconstriction), hyperglycemia (30% incidence), metabolic (lactic) acidosis, hypokalemia (39% incidence and due to a shift of potassium from extracellular to intracellular space), anxiety, and nervousness. Electrocardiogram (ECG) changes with ST segment depression and T wave flattening or inversion may occur and typically resolve after stopping the β-adrenergic therapy. Whether these ECG changes reflect myocardial ischemia or hypokalemia is unclear
- Cardiac output increases dramatically during pregnancy and delivery. The cardiac output returns to nonpregnant values by how long postpartum?
A. 12 hours
B. 1 day
C. 2 weeks
D. 6 months
(C)The numerous changes that take place in the cardiovascular system during pregnancy provide for the needs of the fetus and prepare the mother for labor and delivery. During the first trimester of pregnancy, cardiac output increases by approximately 30% to 40%. At term, the cardiac output is increased 50% over nonpregnant values. This increase in cardiac output is due to an increase in stroke volume and an increase in heart rate. During labor, the cardiac output increases another 10% to 15% during the latent phase, 25% to 30% during the active phase, and 40% to 45% during the expulsive stage. Each uterine contraction increases the cardiac output by about 10% to 25%. The greatest increase in cardiac output occurs immediately after delivery of the newborn, when the cardiac output can increase to 75% above prelabor values. This final increase in cardiac output is attributed primarily to autotransfusion and increased venous return associated with uterine involution. Cardiac output falls to prelabor values within 2 days after delivery; however, it takes about 2 weeks for the cardiac output to decrease to nonpregnant values
- A 32-year-old parturient with a history of spinal fusion, severe asthma, and hypertension (blood pressure 180/110) is brought to the operating room wheezing. She needs an emergency cesarean section under general anesthesia for a prolapsed umbilical cord. Which of the following induction agents would be MOST appropriate for her induction?
A. Sevoflurane
B. Midazolam
C. Ketamine
D. Propofol
(D)Asthma occurs in about 4% to 8% of all pregnancies. Although sevoflurane is a good induction agent for asthmatic patients, a rapid-sequence IV induction with endotracheal intubation to secure the airway is preferred. Because midazolam has a slow onset of action, it is not recommended for a rapid-sequence induction. When inducing general anesthesia in an asthmatic patient, it is imperative to establish an adequate depth of anesthesia before placing an endotracheal tube. If the patient is “light,” then severe bronchospasm may occur. In patients with asthma, IV induction will work with ketamine or propofol. Ketamine is considered by many as the induction agent of choice due to its mild bronchodilator properties, but because propofol (also a good induction agent in asthmatic patients) does not stimulate the cardiovascular system as ketamine does, propofol would be preferred in this patient with hypertensive disorders of pregnancy. In patients with mild asthma who do not need the accessory muscles of respiration, regional anesthesia should be strongly considered if time permits because it would eliminate the need for endotracheal intubation. In addition, inhaled β2-adrenergic agonist (e.g., albuterol) and IV steroids may be beneficial
- Uterine blood flow at term pregnancy typically increases to about
A. 100 mL/min
B. 250 mL/min
C. 500 mL/min
D. 750 mL/min
(D)Uterine blood flow increases dramatically from 50 to 100mL/min before pregnancy to about 700 to 900mL/min at term (i.e., >1 unit of blood per minute). From 70% to 90% of the uterine blood flow at term goes to the intervillous spaces. Uterine blood flow is related to the perfusion pressure (uterine arterial pressure minus uterine venous pressure) divided by the uterine vascular resistance. Thus factors that decrease uterine blood flow include systemic hypotension, aortocaval compression, uterine contraction, and vasoconstriction
- Which one of the following statements is TRUE regarding human immunodeficiency virus (HIV) infected parturients?
A. Central neurologic blockade and epidural blood patches increase the chance of neurologic complications
B. Ninety percent of newborns of untreated HIV-seropositive mothers become infected in utero, during vaginal delivery, or with breastfeeding
C. The pharmacologic effects of benzodiazepines and narcotics are prolonged in patients taking protease inhibitors
D. The risk of seroconversion after percutaneous exposure to HIV-infected blood is about 5%
(C)Central neurologic blockade (i.e., epidural, spinal, or combined spinal-epidural), as well as epidural blood patches, appear to be safe for HIV-infected parturients. Vertical transmission from the mother to the newborn can occur in 15% to 40% when the mother is untreated. With antiretroviral therapy and elective cesarean delivery, the rate of transmission is reduced to about 1% to 2%. The risk of developing HIV after a needlestick injury with HIV-infected blood is 0.3%. (Risk of developing hepatitis B from a needlestick injury with hepatitis B infected blood is 30% and hepatitis C from a needlestick injury with hepatitic C infected blood is 2%-4%.) Patients taking protease inhibitors as part of their drug therapy have inhibition of cytochrome P-450, and both benzodiazepines, as well as narcotics, have prolonged effects
- Which of the following cardiovascular parameters is decreased at term?
A. Central venous pressure
B. Pulmonary capillary wedge pressure
C. Systemic vascular resistance
D. Left ventricular end-systolic volume
(C)There is no change in central venous pressure, pulmonary capillary wedge pressure, pulmonary artery diastolic pressure, or left ventricular end-systolic volume. Left ventricular end-diastolic volume is increased, as is stroke volume, ejection fraction, heart rate, and cardiac output. Systemic vascular resistance is decreased about 20%
- Which of the following signs and symptoms is NOT associated with amniotic fluid embolism (AFE)?
A. Chest pain
B. Bleeding (disseminated intravascular coagulation [DIC])
C. Pulmonary vasospasm with severe pulmonary hypertension and right heart failure
D. Left ventricular failure and pulmonary edema
(A)AFE is a very rare but serious complication of labor and delivery that results from the entrance of amniotic fluid and constituents of amniotic fluid into the maternal systemic circulation. About 10% of maternal deaths are caused by AFE, and two thirds of these deaths occur within 5 hours. Of those patients who survive the AFE, about 50% have significant neurologic dysfunction. For AFE to occur, the placental membranes must be ruptured, and abnormal open sinusoids at the uteroplacental site or lacerations of endocervical veins must exist. The classic triad is acute hypoxemia, hemodynamic collapse (i.e., severe hypotension), and coagulopathy without an obvious cause. More than 80% of these women develop cardiopulmonary arrest. Hemodynamic monitoring often shows a biphasic response; initially pulmonary vasospasm with severe pulmonary hypertension and right heart dysfunction is seen, followed by left ventricular failure and pulmonary edema. DIC occurs in about 66% of cases, and seizures occur about 50% of the time. Recently AFE is believed to be a bit different from a pure embolic event, because findings of anaphylaxis and septic shock also are involved. Bronchospasm, however, is rare (<15%) during an AFE, and chest pain is very rare (2% of patients)
- When is the fetus most susceptible to the effects of teratogenic agents?
A. 1 to 2 weeks of gestation
B. 3 to 8 weeks of gestation
C. 9 to 14 weeks of gestation
D. 15 to 20 weeks of gestation
(B)Organogenesis mainly occurs between the 15th and 56th days (3-8 weeks) of gestation in humans and is the time during which the fetus is most susceptible to teratogenic agents. Although all commonly used anesthetic drugs are teratogenic in some animal species, there is no conclusive evidence to implicate any currently used local anesthetics, IV induction agents, or volatile anesthetic agents in the causation of human congenital anomalies
- A 28-week estimated gestational age (EGA), 1000-g male infant is born to a 24-year-old mother who is addicted to heroin. The mother admits taking an extra “hit” of heroin before coming to the hospital because she was nervous. The infant’s respiratory depression would be best managed by
A. 0.1 mg/kg naloxone intramuscularly (IM) in the newborn’s thigh muscle
B. 0.1 mg/kg naloxone down the endotracheal tube
C. 0.4 mg naloxone IM to the mother during the second stage of labor
D. None of the above
(D)Opioid use during pregnancy has escalated dramatically in recent years and parallels the opioid epidemic observed in the general population. Opioid abuse during pregnancy is estimated to occur in about 5% of patients in the United States, most often with the nonprescription use of pain-relieving drugs such as oxycodone. Other opioids include morphine, heroin, methadone, meperidine, and fentanyl. The problems associated with abuse are many and include the drug effect itself and the effects of substances mixed with the narcotics (e.g., talc, cornstarch), as well as infection and malnutrition. Neonatal abstinence syndrome (NAS) or drug withdrawal syndrome has increased from 1.5 cases per 1000 hospital births in 1999 to 6 cases per 1000 hospital births in 2013. NAS is manifested by central nervous system (CNS), GI symptoms of irritability, high-pitched cry, and poor sleep and sucking reflexes that lead to poor feeding. After delivery, respiratory depression as manifested by a low respiratory rate is treated with controlled ventilation but not with naloxone. Naloxone can precipitate an acute withdrawal reaction and should not be administered to patients with chronic narcotic use (mother or newborn). The dose of naloxone to treat narcotic-induced respiratory depression in the nonaddicted newborn was 0.1mg/kg, but more recent data suggest that it may worsen the neurologic damage caused by asphyxia. Animal studies have also raised the question of complications such as pulmonary edema and cardiac arrest, as well as seizures, and current recommendations are to avoid naloxone use in the newborn. Current recommendations are to assist ventilation until the narcotic effects wear off and not to use naloxone (this includes nonaddicted mothers who have just received narcotics during labor)
- Cardiac output is GREATEST
A. During the first trimester of pregnancy
B. During the third trimester of pregnancy
C. During labor
D. Immediately after delivery of the newborn
(D)Immediately after delivery, the cardiac output can increase 75% above prelabor values. This is thought to result from autotransfusion and increased venous return to the heart associated with involution of the uterus, as well as increased blood return as the result of the lithotomy position. See also Answer 653
- A 1000-g, 27-week EGA boy is born with a heart rate of 80 beats/min. He has slow irregular respiratory efforts, grimaces when a suction catheter is inserted into the mouth and nose for suctioning, and flexes his limbs some but is totally cyanotic. The umbilical cord has only two vessels. The 1-minute Apgar score would be
A. 3
B. 4
C. 6
D. 7
(B)The Apgar score is a subjective scoring system used to evaluate the newborn and is commonly performed 1 minute and 5 minutes after delivery. If the score is less than 7, the scoring is also performed at 10, 15, and 20 minutes after delivery. A value of 0, 1, or 2 is given to each of five signs (heart rate, respiratory effort, reflex irritability, muscle tone, and color) and totaled. In this case the child gets 1 point for heart rate, 1 point for respiratory effort, 1 point for reflex irritability, 1 point for muscle tone, and 0 points for color.
- Which of the following respiratory parameters is NOT increased in the parturient?
A. Minute ventilation (MV)
B. Tidal volume (Vt)
C. Arterial Pao2
D. Serum bicarbonate
(D)The respiratory system undergoes many important changes during pregnancy. Oxygen consumption increases about 20% to 60%. To help supply the needed oxygen for the metabolically active mother and fetus, MV increases about 45% to 50%. The increase in MV is primarily due to an increase in Vt of 40% to 45%, with a slight increase in respiratory rate. The increase in MV produces a fall in the Paco2 to approximately 30 to 32mm Hg, and a respiratory alkalosis develops. To help get the pH back to normal, the serum bicarbonate level falls an average of 4mEq/L. The arterial Pao2 increases slightly due to the fall in Paco2
- Which of the following drugs should NOT be used during transvaginal oocyte retrieval (TVOR) for assisted reproductive technology (ART)?
A. Propofol
B. Ketamine
C. Midazolam
D. All are safe and can be used
(D)About 11% of women (age 15-44) have received medical evaluation and treatment for infertility at some time in their lives, with another 6% of married women (age 15-44) unable to get pregnant after 12 months of trying to conceive. In 2015 there were 231,936 ART cycles in the United States (including 4003 cycles using frozen eggs and 45,779 cycles started with the intent of freezing and storing eggs or embryos for potential future use). With fresh nondonor ART cycles, 29% resulted in a pregnancy and 24% resulted in a live birth. The oocytes can be retrieved by laparoscopy or, more commonly now, by the transvaginal oocyte retrieval (TVOR) method. Most anesthetic drugs have been studied and found not to be a problem, including propofol, midazolam, ketamine, alfentanil, fentanyl, remifentanil, and meperidine. When general anesthesia was used (laparoscopic retrieval), isoflurane with and without nitrous oxide was usually used and appeared safe. However, with increased time during general anesthesia, the oocytes retrieved earlier had better fertilization rates than the oocytes obtained near the end of the laparoscopy. It is unclear whether this was due to the anesthetics or to the lowered pH as a result of the carbon dioxide pneumoperitoneum. Etomidate has not been widely used, and patient numbers are too small to recommend its use. When morphine is used in high doses in animal studies, chromosomal abnormalities are very common (25%-33%), and morphine is not recommended for ART procedures. It is recommended to avoid using the dopamine antagonists (e.g., droperidol and metoclopramide) during ART cycles because these drugs induce hyperprolactinemia, which impairs ovarian follicular maturation. A single dose immediately before oocyte retrieval probably is safe. The 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists (e.g., ondansetron, granisetron) are commonly used as antiemetics, but there is insufficient evidence to recommend their use during ART procedures. The phenothiazines and the antihistamine H1-receptor antagonists are thought to be preferred because they have been studied without adverse effects
- Which of the following conditions is associated with increased bleeding during pregnancy?
A. Lupus anticoagulant
B. Factor V Leiden mutation
C. Protein C deficiency
D. None of the above
(D)All of the conditions listed in this question, as well as deficiencies of antithrombin III and protein S (a cofactor for protein C), lead to hypercoagulable states. Unless treated with anticoagulation therapy, these conditions will have an increased frequency of thrombosis. These conditions may also cause placental thrombosis and insufficiency, and can increase the incidence of obstetric conditions, such as intrauterine growth restriction, preeclampsia, placental abruption, and intrauterine death. Lupus anticoagulant, also called lupus antibody, is a prothrombotic agent. It gets its name because the presence of these antibodies causes an increase in the activated partial thromboplastin (aPTT) test, as these antibodies interfere with phospholipids used to induce in vitro coagulation. However, in vivo these antibodies interact with platelet membrane phospholipids, increasing adhesions and the aggregation of platelets. Factor V Leiden mutation allows factor V to persist longer in the circulation (not metabolized as rapidly by activated protein C), leading to a hypercoagulable state. Protein C inhibits activated clotting factors V and VIII; thus, during a deficiency state, factors V and VIII persist longer in the circulation, leading again to a hypercoagulable state. During pregnancy, the incidence of thrombosis with protein C deficiency is about 25% unless anticoagulation therapy is administered
- What is the BEST way to prevent autonomic hyperreflexia in a quadriplegic woman who is to undergo induction of labor? The complete spinal cord lesion occurred 2 years ago.
A. Only IV drugs should be used; spinal and epidural anesthesia are contraindicated
B. Spinal or epidural lumbar local anesthetics such as bupivacaine alone are effective
C. Spinal or epidural narcotics such as fentanyl alone are effective
D. Autonomic hyperreflexia appears only when the complete spinal cord lesion is below T6, so there is no need to worry
(B)Patients with complete spinal cord lesions above T10 do not have pain with labor. However, about 85% of women with complete spinal cord lesions at the T6 and higher level will develop autonomic hyperreflexia (severe headache, hypertension, bradycardia, sweating above the lesion, and facial flushing) during labor and delivery. Autonomic hyperreflexia typically occurs with the contractions and disappears between contractions. An epidural or a spinal with local anesthetics works well to prevent and/or treat autonomic hyperreflexia. Epidural narcotics such as fentanyl alone are not effective (unless the narcotic is meperidine, which has local anesthetic properties in addition to narcotic effects). To check whether the epidural or spinal that is loaded with a local anesthetic is working in a quadriplegic patient, check the reflexes below the expected level of anesthesia (e.g., patellar) before and after the block. If the patellar reflex is present before but not after the block is performed, the block is effective. The local anesthetic concentration needed for labor epidurals (alone without narcotics) typically is 0.25% or higher. If a cesarean section is needed, 2% lidocaine with epinephrine (1:200,000) has been reported to be safe. If a cesarean section is needed with general anesthesia, typical IV anesthetics and inhalation drugs are used except for muscle relaxation, where succinylcholine is contraindicated (hyperkalemic response) and a nondepolarizing muscle relaxant such as rocuronium is preferred
- A 24-year-old gravida 2, para 1 parturient is anesthetized for emergency cesarean section. On emergence from general anesthesia, the endotracheal tube is removed and the patient becomes cyanotic. Oxygen is administered by positive-pressure bag and mask ventilation. High airway pressures are necessary to ventilate the patient, and wheezing is noted over both lung fields, along with hypoxemia. The patient’s blood pressure falls from 120/80 to 90/60 mm Hg, and heart rate increases from 105 to 150 beats/min. The MOST likely cause of these manifestations is
A. Amniotic fluid embolus (AFE)
B. Mucus plug in trachea
C. Tension pneumothorax
D. Aspiration
(D)The signs presented in this case—bronchospasm, high airway pressures, hypoxemia, and wheezing, followed by hypotension and tachycardia—make gastric acid aspiration the most likely cause. It is important to note that aspiration can develop not only on induction but also on extubation, as in this case. That is why it is so important always to empty the patient’s stomach with an orogastric tube after an endotracheal tube is placed in any pregnant patient over 20 weeks’ gestation undergoing general anesthesia, and to extubate the patient when she is fully awake and responsive. Morbidity and mortality occurring after gastric acid aspiration are determined by both the amount and the pH of the aspirated gastric material. Based on an animal study in which 0.4mL/kg with a pH less than 2.5 injected into the right mainstem of one rhesus monkey caused death, many have used that definition (0.4mL/kg with a pH <2.5) to categorize patients who are “at risk” for significant aspiration morbidity and mortality. Using these values, up to 70% of women who fasted before elective cesarean section are “at risk for aspiration.” Recently, it has been noted that the volume needed to cause aspiration in primates should be greater (e.g., 0.8mL/kg) and the pH less than 2.5. Regardless of the definition of the “patient at risk,” when aspiration occurs, it can be lethal. Other signs and symptoms of aspiration include sudden coughing or laryngospasm, dyspnea, tachypnea, the presence of foreign material in the mouth or posterior pharynx, chest wall retraction, cyanosis not relieved by oxygen supplementation, tachycardia, hypotension, and the development of pinky frothy exudates. The onset of these signs and symptoms is usually rapid. Early treatment consists of supplemental oxygen with positive-pressure ventilation, PEEP, or continuous positive airway pressure, and suctioning of the airway can decrease the incidence of mortality from acid aspiration. Mortality seems to be reduced when protective ventilatory strategies are used (i.e., tidal volumes of 6mL/kg with plateau pressures of <30cm H2O are better than if 12mL/kg and plateau pressures of 50cm H2O are used). Conservative compared with liberal fluid management (guided by central venous pressures and/or pulmonary artery wedge pressures) also appears to improve lung function. The use of prophylactic antibiotics and/or steroids has not been helpful. With an AFE, high airway pressures and bronchospasm are not seen, but cardiovascular collapse (including >80% cardiac arrest), DIC (60%), and seizures (>50%) are present. A mucus plug of an endotracheal tube can be associated with high airway pressures and mainly airway issues and would be extremely rare after endotracheal extubation. A tension pneumothorax would be more common during the anesthetic with positive-pressure ventilation and would most likely lead to decreased breath sounds on one side and a deviated trachea; it would not have presenting signs after endotracheal extubation. See Question 658
- A 29-year-old gravida 1, para 0 woman at 8 weeks of gestation is to undergo an emergency appendectomy under general anesthesia with isoflurane, N2O, and oxygen. Which of the following is a proven untoward consequence of general anesthesia in the unborn fetus?
A. Congenital heart disease
B. Cleft palate
C. Behavioral defects
D. None of the above
(D)The primary objectives in the anesthetic management of a pregnant woman undergoing general anesthesia for nonobstetric surgery are as follows: to (1) ensure maternal safety; (2) avoid teratogenic drugs; (3) avoid intrauterine fetal asphyxia; and (4) prevent the induction of preterm labor. Premature onset of labor is the most common complication associated with surgery during the second trimester of pregnancy. Performance of intra-abdominal procedures in which the uterus is manipulated is the most significant factor in causing premature labor in these patients. Neurosurgical, orthopedic, thoracic, or other surgical procedures that do not involve manipulation of the uterus do not cause preterm labor. No anesthetic agent or technique has been found to be significantly associated with a higher or lower incidence of preterm labor. Furthermore, there is no evidence that the risk of developing any of the conditions listed in this question is increased for the offspring of patients who receive general anesthesia during pregnancy
- A lumbar epidural is placed in a 24-year-old gravida 1, para 0 parturient with myasthenia gravis (MG) for labor. Select the TRUE statement regarding neonatal MG.
A. The newborn is almost always affected with myasthenia
B. The newborn is affected by maternal immunoglobulin M (IgM) antibodies
C. The newborn may require anticholinesterase therapy for up to 4 weeks
D. The newborn will need lifelong treatment
(C)MG is an autoimmune neuromuscular disease in which immunoglobulin G (IgG) antibodies are directed against the ACh receptors in skeletal muscle, causing patients to present with general muscle weakness and easy fatigability. Smooth muscle and cardiac muscle are not affected. About 10% to 20% of newborns born to mothers with MG are transiently affected because the IgG antibody is transferred through the placenta. Neonatal MG is characterized by muscle weakness (e.g., hypotonia, respiratory difficulty) and may appear within the first 4 days of life (80% appear within the first 24 hours). Anticholinesterase therapy may be required for several weeks, until the maternal IgG antibodies are metabolized
- A patient having which of the following conditions is LEAST likely to develop DIC?
A. Severe preeclampsia
B. Placental abruption
C. Placenta previa (bleeding)
D. Dead fetus syndrome
(C)Disseminated intravascular coagulation (DIC) is an acquired coagulopathy characterized by excessive fibrin deposition, depression of the normal coagulation inhibition mechanism, and impaired fibrin degradation. The formation of clots causes a depletion of platelets and factors. Laboratory diagnosis of DIC is based on the demonstration of abnormalities in platelet count (i.e., <100,000/mm3), prolonged prothrombin time (i.e., >3 seconds above normal), presence of fibrin degradation products, and fibrinogen level (i.e., ≤1g/L). DIC is associated with the following obstetric conditions: placental abruption, dead fetus syndrome, AFE, gram-negative sepsis, and severe preeclampsia. Placental abruption is the most common cause of DIC in pregnant patients. If one looks at severe placental abruptions (in which the abruption is large enough to cause fetal death), about 30% of patients will develop DIC within 8 hours of the abruption. Nonobstetric causes of DIC include sepsis and malignancy. Patients with placenta previa who are bleeding do not develop DIC because the blood loss does not induce a coagulopathy
- A 28-year-old gravida 1, para 0 parturient with Eisenmenger syndrome (pulmonary hypertension with an intracardiac right-to-left or bidirectional shunt) is to undergo placement of a lumbar epidural for analgesia during labor. It may be wise to avoid a local anesthetic with epinephrine in this patient because it
A. Lowers pulmonary vascular resistance
B. Lowers systemic vascular resistance
C. Increases heart rate
D. Causes excessive increases in systolic blood pressure (SBP)
(B)Eisenmenger syndrome may develop in patients with uncorrected left-to-right intracardiac shunting such as for ventricular septal defect (VSD), atrial septal defect (ASD), or patent ductus arteriosus (PDA). About half of the patients with an unrestricted and unrepaired VSD will ultimately develop Eisenmenger syndrome. In this syndrome, the pulmonary and vascular tone and right ventricular muscle undergo changes in response to the increased blood flow from the left-right shunt, producing severe pulmonary hypertension and eventually a change in the direction of the shunt to a right-to-left or bidirectional type with peripheral cyanosis. The maternal mortality rate is 30% to 50%. When the Eisenmenger syndrome develops, the pulmonary vascular resistance becomes fixed, making this condition not amenable to surgical correction. Survival beyond age 40 years is uncommon. Any event or drug that increases pulmonary vascular resistance (e.g., hypercarbia, acidosis, hypoxia) or decreases systemic vascular resistance will increase the right-to-left shunt, will exacerbate peripheral cyanosis, and may precipitate right ventricular heart failure in these patients. Controversy exists regarding pain management for these patients because pain can elevate pulmonary artery pressures and cause more shunting. Many practitioners prefer a narcotic-based analgesic (spinal or epidural). Because these patients are very dependent on preload and afterload, invasive monitors to monitor intravascular volume (e.g., central venous pressure and arterial catheter) and a pulse oximeter to evaluate the amount of shunting (e.g., a decrease in oxygen saturation may indicate an increase in right-to-left shunting) are helpful to assess the need for aggressive treatment of any fall in preload or peripheral vascular resistance. It should be recalled that centrally administered local anesthetics reduce both preload and afterload. An epidural anesthetic with a slower onset of action may be preferred to a spinal anesthetic with the faster onset of action. Low-dose epinephrine used in an epidural anesthetic can be used to decrease the absorption of local anesthetics but should be used cautiously, if at all, because a further decrease in systemic vascular resistance may result from the β effect of absorbed epinephrine, and an intravascular injection may further elevate pulmonary pressures, exacerbating the right-to-left shunt
