OB review questions Flashcards

Question

661. 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

Answer 1

(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

Answer 2

(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.

Answer 3

(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 32 mm Hg, and a respiratory alkalosis develops. To help get the pH back to normal, the serum bicarbonate level falls an average of 4 mEq/L. The arterial Pao2 increases slightly due to the fall in Paco2

Answer 4

(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

Answer 5

(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

Answer 6

(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

Answer 7

(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 0.4 mL/kg with a pH less than 2.5 injected into the right mainstem of one rhesus monkey caused death, many have used that definition (0.4 mL/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., 0.8 mL/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 6 mL/kg with plateau pressures of < 30 cm H2O are better than if 12 mL/kg and plateau pressures of 50 cm 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

Answer 8

(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

Answer 9

(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

Answer 10

(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., ≤ 1 g/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

Answer 11

(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

Answer 12

(C) The need for a hysterectomy for a planned repeat cesarean delivery is 0.3%, for a successful vaginal birth after cesarean is 0.1%, and for an unsuccessful TOLAC is 0.5%. With multiple gestations, uterine atony is common, and the need for a hysterectomy is sixfold in a normal delivery. However, the patient with placenta previa and a previous scar in the uterus has the highest chance of needing an emergency hysterectomy for uncontrolled bleeding at the time of delivery because of the associated placenta accreta (abnormally adherent placenta). The incidence of placenta accreta in a patient with placenta previa and no previous cesarean section is 3% to 4%, with one previous cesarean section is about 10% to 25%, and with two or more previous cesarean sections is 40% to over 60%. Most patients with placenta accreta will require a cesarean hysterectomy. The average blood loss during an emergency cesarean delivery and needed hysterectomy is 5 to 7 units of blood. Patients with a known placenta accreta should undergo a scheduled preterm cesarean delivery and hysterectomy with the placenta left in situ because any attempt to remove the placenta would likely lead to hemorrhage. Attempts to preserve the uterus with a placenta accreta has been described in select cases when hemodynamic stability is present and there is a very strong desire for a future pregnancy. This may include leaving the placenta in situ for placental involution or for only partial placenta accreta management by curettage and oversewing. With an advanced abdominal pregnancy, a laparotomy with delivery of the fetus is performed. Management of the placenta is controversial: Removal of the placenta can lead to massive hemorrhage, whereas leaving the placenta in situ is associated with an increase in infectious morbidity; however, a hysterectomy is not needed because the fetus is extrauterine

Answer 13

(B) According to the ASA’s Closed Claims Project for Obstetric Anesthesia Claims (640 claims as of December 2010 report), maternal nerve damage (19%), neonatal brain damage (16%), and maternal death (15%) were the three most frequent claims. Other causes include headache (11%), back pain (10%), neonatal death (9%), emotional distress (8%), maternal brain damage (7%), pain during anesthesia (6%), and aspiration pneumonitis (1%)

Answer 14

(C) Chorioamnionitis occurs in about 1% of all pregnancies. It includes the clinical signs and symptoms of infection, temperature higher than 38° C, maternal and fetal tachycardia, uterine tenderness (about 10% of patients), and/or foul-smelling amniotic fluid. Prompt delivery is the cornerstone of therapy. At one time it was thought that antibiotics should be administered only after delivery because antepartum or intrapartum antibiotics may “obscure the results of neonatal blood cultures.” However, early antepartum treatment with antibiotics leads to a decrease in maternal and neonatal morbidity, compared with delaying the antibiotics until after delivery, and is currently recommended. Epidural anesthesia has been shown to be commonly used and safe in these patients, preferably after antibiotics have been started. It seems prudent, however, to always individualize care and to weigh the risks versus the benefits of epidural anesthesia in a patient with suspected bacteremia

Answer 15

(A) Meconium-stained amniotic fluid occurs in about 5% to 15% of all deliveries. Although intrapartum oropharyngeal and nasopharyngeal suction for all newborns born to mothers with meconium staining has been routine care for many years, current evidence shows no real benefit, and it is no longer recommended. In newborns who are vigorous (i.e., strong respiratory efforts, good muscle tone, and heart rate > 100 beats/min), no treatment other than gentle bulb syringe suctioning to clear oral or nasal secretions is needed. Intubation and tracheal suction should be performed only in newborns who are not vigorous, and the decision to intubate and suction does not depend on the consistency of the meconium-stained fluid, as was once recommended. Because meconium is sterile, antibiotics are not needed. Steroids have not been necessary in the treatment of meconium-stained newborns. RDS is a condition that occurs as a result of low levels of pulmonary surfactant in the alveoli. RDS occurs in premature newborns, whereas meconium staining occurs typically in older, often post-term, newborns

Answer 16

(C) Placenta previa occurs when the placenta implants on the lower uterine segment so that all (total) or part of the placenta (partial) covers the internal cervical os. A marginal placenta previa occurs when the placenta lies close to but does not cover the internal cervical os. Placenta previa occurs in about 0.5% of all pregnancies and has a maternal mortality of less than 1% but a fetal mortality approaching 20% (primarily because of prematurity and intrauterine asphyxia). Patients typically present with painless vaginal bleeding that stops spontaneously (first bleed). Delivery is cesarean and is often made a few weeks after the “first” bleed, when the baby’s lungs are more mature (e.g., after 37 weeks EGA). A later bleed can be uncontrolled and may be accompanied by significant hypovolemia and hypotension. Regional anesthesia is contraindicated in severely hypovolemic patients. Blood should be started when available, but replacing blood loss first to correct intravascular volume before induction of anesthesia may not be practical because bleeding may be faster than replacement is possible (i.e., may be > 1 unit/min). A rapid-sequence general anesthetic (assuming acceptable airway) is preferred. Ketamine (0.75-1 mg/kg) as well as etomidate (0.3 mg/kg) supports the cardiovascular system better than propofol. In rare but severe cases of hypovolemic shock, all IV anesthetics may cause the blood pressure to fall further, and succinylcholine alone may be all that is required. In these severe cases, maternal recall should be considered secondary to maternal safety. In cases in which a difficult intubation is likely and the patient is hypovolemic, an infiltration local anesthetic may be best

Answer 17

(D) At term pregnancy, Vt increases about 40% to 45%, and the inspiratory reserve volume (IRV) increases about 5%. A decrease occurs in both the ERV (20%-25%) and the residual volume (RV; 15%-20%). A capacity is defined as two or more lung volumes. Functional residual capacity (FRC = ERV + RV) is decreased about 15% to 20% and is partly responsible for the rapid fall in maternal oxygenation that occurs with apnea during the induction of general anesthesia. Total lung capacity (TLC = Vt + IRV + ERV + RV) decreases about 5%, whereas vital capacity (VC = Vt + IRV + ERV) remains unchanged

Answer 18

(A) Evaluation of the airway should be performed before the induction of any general anesthetic. In cases in which an unrecognized difficult airway exists (unable to perform endotracheal intubation in a reasonable period of time), the patient should be awakened if the procedure is purely elective and if the fetus has minimal or no fetal distress (as in this elective case). A regional anesthetic or awake intubation then can be safely performed. In cases of fetal or maternal distress, other options for securing the airway may be necessary

Answer 19

(B) Labor pain is some of the most intense pain that people can experience. Although there is considerable variability in the amount of intensity of pain during labor, in general primiparous patients have more pain than multiparous patients. Primiparous women who have attended prepared childbirth classes have somewhat less pain than women who have not attended prepared childbirth classes. For women who have experienced labor and delivery, attending prepared childbirth classes does not seem to affect the amount of pain that they experience. Labor pain appears to exceed chronic low back pain, nonterminal cancer pain, phantom limb pain, postherpetic neuralgia, or the pain from a fracture. Patients with causalgia or patients experiencing an amputation of a digit have more pain than the parturient. There appears also to be an association of the increasing amount of pain with increasing cervical dilation.

Answer 20

(C) The prevalence of women smoking during pregnancy was about 16% in the United States in 2010. Cigarettes contain nicotine, carbon monoxide, cyanides, and over 4000 other chemicals. Smoking affects small airway function and mucus secretion, and it impairs ciliary transport in the lungs; smoking also increases atherosclerosis and heart disease. Nicotine increases sympathetic tone (e.g., maternal heart rate, blood pressure, cardiac work). Carbon monoxide can occupy 3% to 15% (or more) of the oxygen-carrying capacity of blood and thus decreases oxygen delivery to tissues. Smoking cessation, even for a short time, may be safer for the fetus. Nonpharmacologic methods are preferred over nicotine patches or nicotine gum to help women stop smoking during pregnancy because studies of nicotine replacement are lacking. Cigarette smoking is associated with an increase in ectopic pregnancies, placental abruption, spontaneous fetal loss, and low-birth-weight babies (with an increased neonatal and infant mortality), as well as SIDS and lower intelligence. Interestingly, the incidence of preeclampsia is 30% to 40% lower among women who are smokers compared with women who are nonsmokers. The reason for this is unclear but may be related to stimulation of nitric oxide release or an inhibition of thromboxane A2 synthesis. Because smoking irritates the airway, if general anesthesia is needed during pregnancy, desflurane is best avoided, whereas volatile anesthetics, such as sevoflurane, which does not irritate the airway, are preferred

Answer 21

(C) In 2012, the U.S. Food and Drug Administration (FDA) approved the use of simple devices for the administration of nitrous oxide as “minimal sedation” for labor analgesia. Inhaled nitrous oxide is used by < 1% of patients for labor analgesia in the United States, but its use is more common in other countries such as Canada (43%) and the United Kingdom (62%). These noninvasive devices have demand valves where the patient must initiate the breathing. When inhalation is completed, there is no free flow of anesthetic into the room. The devices also have a scavenging system to decrease exposure to low levels of nitrous oxide. The gas inhaled is typically 50% nitrous oxide and 50% oxygen. The patient must hold the mask or mouthpiece in place without the assistance of a nurse, family member, or labor support person. Typically it takes about 30 to 60 seconds for analgesia to develop, so the patient should initiate inhalation at the start of the uterine contraction and continue breathing the gas until the end of the contraction. This gives the women in labor another analgesic option. The patients have the freedom to move about and do not require the placement of an IV or urinary catheter. It may prove useful for women with disorders of coagulation, chronic pain or anxiety, and a poor response to opioid medications. The quality of analgesia with inhaled nitrous oxide is variable, but less so than with epidural analgesia. Side effects of nitrous oxide for labor analgesia include nausea and vomiting (13%-33%), dizziness (4%), drowsiness (4%), and paresthesias (which are also related to maternal hyperventilation). The incidence of hypoxia appears to be low. Keep in mind that using narcotics or sedatives with nitrous oxide may depress respirations and increase the amount of nausea. Apgar scores of newborn infants whose mothers have used inhaled nitrous oxide appear to be similar to those of infants whose mothers used other forms or no forms of analgesia. Anesthesia personnel are not involved in their use

Answer 22

(A) When performing an RSI for a cesarean section, the patient is preoxygenated, and after you ascertain that intubation should be easy, you inject your IV general anesthetic (e.g., propofol 2.5 mg/kg, ketamine 1-1.5 mg/kg, or etomidate 0.3 mg/kg) followed by a paralytic drug to facilitate oral endotracheal intubation. Thiopental (4-5 mg/kg) is another IV general anesthetic that can be used if it is available (not available in the United States). Paralysis to optimize tracheal intubation conditions can be obtained with either succinylcholine (1-1.5 mg/kg in 30-45 seconds) or rocuronium (1.2 mg/kg in < 60 seconds). Vecuronium (0.1 mg/kg) can also be used but is less desirable because it has a slower onset of action of 144 seconds. Atracurium is the least desirable of the listed drugs due to the significant histamine release and resultant hypotension and slow onset of action. Although cisatracurium has little histamine release, it has a very slow onset of action and is not recommended for an RSI induction if succinylcholine, rocuronium, or vecuronium is available

Answer 23

(C) Intrathecal opiates (e.g., morphine, fentanyl, sufentanil) are very effective in relieving the visceral pain during the first stage of labor. Intrathecal opiates administered alone (except for meperidine, which has local anesthetic properties) do not provide adequate pain relief for second-stage somatic pain

Answer 24

(A) The most common side effect of intraspinal narcotics is pruritus. The next most common side effects are nausea and vomiting, followed by urinary retention and drowsiness. Respiratory depression and headache may occur but are relatively infrequent

Answer 25

(C) Hypertension during pregnancy is divided into four groups: preeclampsia-eclampsia, chronic hypertension (of any cause), chronic hypertension with superimposed preeclampsia, and gestational hypertension. Preeclampsia-eclampsia is a hypertensive disorder of pregnancy with associated proteinuria (≥ 300 mg protein per 24-hour urine collection). As of recently (November 2013), the presence of proteinuria is no longer needed for the designation of preeclampsia-eclampsia. The reason for the change is that some patients develop proteinuria late and have their diagnosis and needed treatment delayed. Current definition of preeclampsia-eclampsia is the new onset of hypertension along with proteinuria or, in the absence of proteinuria, new onset of hypertension associated with thrombocytopenia (platelet count < 100,000/mL), impaired liver function, new onset of renal insufficiency (serum creatinine > 1.1 mg/dL or doubling of serum creatinine in the absence of any other renal disease), pulmonary edema, or new-onset cerebral or visual disturbances. Gestational hypertension, which is isolated new-onset hypertension (after 20 weeks) that resolves by 12 weeks postpartum, is a retrospective diagnosis. Preeclampsia-eclampsia rarely occurs before the 20th week of pregnancy, except in patients with gestational trophoblastic neoplasms (e.g., molar pregnancy). The incidence of preeclampsia is significantly higher in parturients with a hydatidiform mole, multiple gestations, obesity, polyhydramnios, or diabetes and occurs more commonly with the first pregnancy. Mothers with preeclampsia during their first pregnancy have a 33% chance of having preeclampsia in subsequent pregnancies. Preeclampsia can progress to eclampsia (preeclampsia accompanied by a seizure not related to other conditions). Eighty percent of the seizures occur before or during delivery; 85% of the remaining 20% will have the seizure within the first 24 hours after delivery. Approximately 5% of untreated parturients with preeclampsia will develop eclampsia. HELLP syndrome (Hemolysis, Elevated Liver enzymes, and Low Platelet count) is a variant of preeclampsia. Chronic hypertension is persistent hypertension before, during, and after pregnancy (e.g., > 6 weeks postpartum). Chronic hypertension with superimposed preeclampsia occurs when a patient with chronic hypertension develops preeclampsia. Also see Question 645

Answer 26

(A) AFE is a rare condition (5 per 100,000 live births). It presents in a variety of ways but often in a dramatic way, with acute hypoxemia, cardiovascular collapse, DIC, and, in about 50% of cases, a seizure. Patients with a high spinal or epidural may complain of dyspnea, but they also have marked weakness and would certainly not be able to wrestle or struggle with their health care providers. Patients experiencing an intravascular injection of local anesthetic present with CNS signs of toxicity (light-headedness, visual or auditory disturbances, muscular twitching, convulsion, coma) or, at higher levels, cardiovascular collapse. Magnesium overdosage is also associated with muscle weakness. The typical eclamptic seizure is tonic–clonic. Patients with eclampsia do not complain of dyspnea, although an associated aspiration may produce similar symptoms. See Question 658

Answer 27

(C) Epidural fentanyl (50-100 μg) and epidural sufentanil (10-20 μg) each have a duration of action for about 2 to 4 hours. Epidural meperidine (50-75 mg) has an intermediate duration of action of 4 to 12 hours, whereas epidural morphine (3-4 mg) has the longest duration of action, of 12 to 24 hours

Answer 28

(C) The renal system undergoes dramatic anatomic (increase in kidney size as well as dilation of the ureters) and functional changes in pregnancy. Renal plasma flow increases about 75% to 85%, and glomerular filtration rate (GFR) increases about 50% and is reflected by an increase in clearance of urea, creatinine, and uric acid. Because of the increased clearance, we see a decrease in BUN to 8 to 9 mg/dL, serum creatinine to 0.5 to 0.6 mg/dL, and serum urate to 2.0 to 3.0 mg/dL. Glucosuria is common and is attributed to both the increase in GFR and a reduced renal tubular resorption of glucose

Answer 29

(C) All volatile halogenated anesthetic agents (e.g., halothane, enflurane, isoflurane, desflurane, sevoflurane) cause a dose-related relaxation of uterine smooth muscle. With anesthetic concentrations of 0.2 MAC, the decrease in uterine activity is slight, and these agents have been used for inhalation analgesia during labor. At 0.5 MAC, uterine relaxation is more significant, but the uterine response to oxytocin remains intact. Nitrous oxide does not affect uterine activity

Answer 30

(B) Passive diffusion is the primary means for the placental transfer of drugs. Factors that promote diffusion of drugs across placental membranes include decreased maternal protein binding (although some believe that this is not very important because of rapid diffusion of drugs from protein), low molecular weight (< 500 Da), high lipid solubility (low water solubility), a low degree of ionization, and a large concentration gradient across the membranes. Highly ionized drugs, such as neuromuscular drugs, do not pass the placenta in significant amounts

Answer 31

(D) The average blood loss associated with a vaginal delivery is about 600 mL and after a cesarean delivery is about 1000 mL (Chestnut: Chestnut’s Obstetric Anesthesia, ed 5, pp 24–25).

Answer 32

(C) The fetus has several compensatory mechanisms for dealing with low O2 pressures (umbilical vein Po2 approximately equal to 30 mm Hg when the mother is breathing room air) to which it is exposed. These include a higher hemoglobin concentration (15-20 g/dL) and the presence of fetal hemoglobin, which has a greater affinity for oxygen (the fetal oxyhemoglobin dissociation curve is shifted to the left of the maternal oxyhemoglobin dissociation curve). At term, maternal blood flow through the placenta (700 mL/min) is about double the fetal blood flow through the placenta (300-360 mL/min). Fetal blood has a lower pH than maternal blood, which may be related to the higher Paco2 levels seen in fetal blood

Answer 33

(B) A pregnant woman is considered overweight when her body mass index (BMI) is 25.0 to 29.9 kg/m2 and obese when the BMI is greater than 30 kg/m2. The World Health Organization (WHO) defines three grades of obesity: Class I = BMI 30 to 34.5 kg/m2, Class II as BMI 35 to 39.9 kg/m2, and Class III as BMI ≧ 40 kg/m2. The obese patient is at increased risk for several comorbid diseases, including obstructive sleep apnea (OSA), diabetes, hypertension, gallbladder disease, chronic back pain, and coronary artery disease. During pregnancy, the obese patient has an increased chance of gestational diabetes, hypertensive disorders of pregnancy, preterm delivery, deep vein thrombosis, pulmonary thromboembolism, respiratory depression, wound infections, postpartum hemorrhage, cesarean deliveries, and death (reviews note that about 50% or more of pregnant women who die are overweight or obese). The increased incidence of cesarean deliveries may relate to an increase in abnormal presentations, fetal macrosomia, meconium staining, late decelerations in the FHR, and dysfunctional labor. Anesthetic challenges include increased risk of aspiration, difficulty finding adequate venous access, difficulty with mask ventilation, difficulty with endotracheal intubation, difficulty in performing regional anesthesia, operative positioning, and prolonged surgery. Interestingly, obese and morbidly obese patients appear to have a lower incidence of PDPHs. Etiology for the lower incidence of PDPHs is unclear

Answer 34

(D) Normal healthy term newborns breathing room air take a while for the oxygen saturations to rise to normal 90% to 95% levels. In caring for the newborn who is not breathing, bag and mask ventilation with room air is now recommended, with targeted preductal oxygen saturation (right hand or wrist) increases of about 5% for each minute of the first 5 minutes of life, starting at 1 minute oxygen saturation of 60% to 65% (at 2 minutes 65%-70%, at 3 minutes 70%-75%, at 4 minutes 75%-80%, at 5 minutes 80%-85%). After 5 minutes, oxygen saturation more slowly increases to 85% to 95% by 10 minutes of life. If higher concentrations of oxygen are needed to reach the targeted oxygen saturations (especially in preterm newborns < 32 weeks), a blender for oxygen and air can be used. For this newborn, an oxygen saturation of 83% at 5 minutes is appropriate, and observation only is needed

Answer 35

(B) Second- and third-trimester obstetric hemorrhage is not uncommon in obstetrics. Placenta previa (where the placenta is partially or completely covering the cervical os) is suspected when painless vaginal bleeding occurs during the second or third trimester. This first episode of bleeding is usually not associated with maternal shock or fetal distress and is expectantly managed if the bleeding stops and the fetus is immature. However, with a second or third episode of vaginal bleeding, the bleeding may continue and delivery may be indicated. Placental abruption (separation of the placenta from the uterine wall after 20 weeks’ EGA and before delivery) is more typically associated with abdominal pain and can be associated with fetal distress. Bleeding with placenta abruption may be revealed or concealed behind the placenta. Uterine rupture usually presents with severe abdominal pain and fetal distress. Vasa previa refers to a condition where the fetal blood vessels are unsupported by the umbilical cord or placental tissue and cross over the cervical os. When the fetal membranes rupture, a tear in a fetal blood vessel may develop, leading to fetal exsanguination

Answer 36

(D) The first stage of labor starts with the onset of labor and ends with complete cervical dilation (10 cm). It is visceral pain, associated with uterine contractions and dilation of the cervix, and is transmitted via the autonomic nervous system through the sympathetic fibers that pass through the paracervical region and enter the CNS at T10-L1 segments. The second stage of labor includes these pathways and adds the somatic fibers of the birth canal that are transmitted via the pudendal nerve entering the CNS at S2-S4. Neuraxial block (spinal and/or epidural) with only narcotics can be useful for first-stage pain; however, the somatic pain is not well treated with narcotics alone. A local anesthetic–induced lumbar epidural block with or without narcotics can produce complete anesthesia during both first and second stage of labor pain. If a low spinal or saddle block is performed with local anesthetics (covering only sacral areas), the uterine contraction pain still will be felt. Paracervical blocks block only the first-stage pain. Pudendal blocks block the somatic component during the second stage but not the visceral pain of uterine contractions

Answer 37

(C) Anesthetic considerations for open fetal surgery include administering anesthesia for the mother and the child, giving excellent uterine relaxation, maintaining an adequate maternal blood pressure, providing muscle relaxation to the fetus if needed, and preventing postoperative premature labor. Uterine relaxation is needed to prevent uterine contractions, with possible separation of the placenta from the uterine wall. High-dose volatile anesthetics (e.g., 2 or 3 MAC) can provide excellent maternal anesthesia, as well as uterine relaxation and anesthesia for the fetus. If additional anesthesia is needed or when a lower concentration of volatile anesthetic is administered, maternally administered IV narcotics can be used (e.g., remifentanil infusions at a dose of 0.1 μg/kg/min) or a fetal IM injection of fentanyl (up to 10-20 μg/kg) can be performed. If one chooses to use a lower dose of volatile anesthetics, nitroglycerin infusion may be needed to keep the uterus from contracting. Maternal hypotension (mean blood pressure < 65) is not uncommon and is treated with more left uterine tilt, fluids, and, if needed, phenylephrine or ephedrine. Monitoring the fetal oxygen saturation reveals normal values of 50% to 70%; values less than 50% signal impaired placental perfusion (e.g., maternal hypotension, cord compression). If the obstetrician needs the fetus to be paralyzed, then a neuromuscular blocking drug can be given directly into the fetus because placental transfer of muscle relaxants is poor. The dose of muscle relaxant, however, must be larger when the fetus is in utero compared with the fetus after delivery (newborn of the same weight) because the blood volume of the fetus in utero includes the fetal blood volume as well as the placental blood volume. Typically the IM dose is about four to six times the effective dose in 95% of subjects (ED95) or for vecuronium is 0.2 to 0.3 mg/kg. Magnesium sulfate may be started to decrease the chance of premature labor at the end of the surgery as the volatile anesthetic concentration is decreased or the nitroglycerin infusion is discontinued. One should recall that the magnesium sulfate potentiates neuromuscular blocking drugs significantly. In many cases of fetal surgery, the mother may also receive an epidural for postoperative analgesia

Answer 38

(D) 15-Methyl PGF2α (carboprost, Hemabate) can be used for the treatment of refractory uterine atony (after oxytocin is administered and uterine massage has been performed). It works by increasing contractions of smooth muscle. The dose is 0.25 mg injected IM or directly into the uterine wall, repeated as needed every 15 to 90 minutes with a maximum total dose of 2 mg (8 doses). It has several important side effects, such as bronchospasm, ventilation-to-perfusion mismatch with an increase in intrapulmonary shunting, hypoxemia, and increased blood pressure. It is contraindicated in patients with asthma and relatively contraindicated in patients with pregnancy-induced hypertension. Other side effects include GI spasms (e.g., nausea, vomiting, and diarrhea)

Answer 39

(C) International consensus states that magnesium sulfate (MgSO4) is the anticonvulsant of choice in the preeclamptic patient. In addition to its anticonvulsant effect, MgSO4 has many other actions on skeletal and cardiac muscles. MgSO4 is usually started as an IV bolus of 6 g over 20 minutes followed by an infusion of 2 g/hr (provided that kidney function is normal). Clinical monitoring for toxicity is performed looking at deep tendon reflexes, and blood levels are often performed and reported in either mEq/L or mg/dL (1 mEq/L = 1.22 mg/dL). The therapeutic range for serum MgSO4 is 4 to 8 mEq/L (4.8-9.6 mg/dL). In an unanesthetized patient, a loss of deep tendon reflexes occurs at 10 mEq/L (12 mg/dL), respiratory arrest occurs at 15 mEq/L (18 mg/dL), and cardiac arrest occurs at 25 mEq/L (30 mg/dL). As long as deep tendon reflexes are present, significant toxicity is unlikely. In a patient with an epidural or spinal anesthetic loaded for a cesarean section, the patellar reflex is often depressed by the local anesthetic; estimation of deep tendon reflexes should be done with the biceps tendon (unless a total spinal develops). ECG changes, including PR interval prolongation and QRS complex widening, occur at serum levels of 5 to 10 mEq/L (6-12 mg/dL), sinoatrial and atrioventricular block at 15 mEq/L (18 mg/dL), and cardiac arrest at levels greater than 25 mEq/L (30 mg/dL). The treatment for magnesium toxicity is calcium. The dose of 1 g of calcium gluconate (10 mL of a 10% solution) can be administered slowly over at least 2 minutes to treat high magnesium levels. Rapid administration may take away the anticonvulsant effects, so careful slow titration is recommended. About 60% of eclamptic seizures occur before delivery. Most postpartum seizures develop in the first 24 hours after delivery, but eclamptic seizures may occur as late as 22 days after delivery

Answer 40

(C) Three different aspiration syndromes have been described in the general population: aspiration of particulate matter causing mainly mechanical airway obstruction, aspiration of acid fluid causing aspiration pneumonitis (Mendelson syndrome), and aspiration of gram-positive, gram-negative, and anaerobic bacteria (e.g., bowel obstruction) causing aspiration pneumonia. Symptoms of aspiration pneumonitis include coughing, tachypnea, tachycardia, bronchospasm, and hypoxemia. Treatment is supportive and includes the Heimlich maneuver if a large foreign body is lodged in the trachea (which is unlikely in the fasting laboring patient), endotracheal intubation, suctioning the airway to remove particulate material, administration of increased concentrations of oxygen, and application of PEEP to achieve oxygenation goals as needed. Coughing is due to the airway irritation and is most effectively decreased with muscle paralysis. Intravenous lidocaine is not effective. Use of saline or bicarbonate lavage does not decrease lung damage and can worsen hypoxemia. Glucocorticoids or other anti-inflammatory drugs have not been effective in limiting the inflammation and may increase the risk of secondary bacterial infection

Answer 41

(C) Aortocaval compression typically is not a problem until about 18 to 20 weeks’ gestation, when the uterus is large enough to compress the aorta and vena cava when the patient assumes the supine position. If the uterus is larger than normal (e.g., multiple gestations or polyhydramnios), then aortocaval compression may appear earlier. See also Question 714

Answer 42

(B) Cimetidine and ranitidine are H2-receptor antagonists that will increase gastric pH but take at least 30 minutes to work. Metoclopramide is not an antacid but may be useful by increasing the lower esophageal sphincter tone. Only liquid antacids raise gastric pH quickly. Sodium citrate, a clear nonparticulate antacid (0.3 M sodium citrate), is preferred over particulate antacids (aluminum hydroxide, magnesium trisilicate, magnesium hydroxide) because clear nonparticulate antacids cause less pulmonary damage if aspirated. Sodium citrate 30 mL neutralizes 255 mL of HCl with a pH of 1.0. Neutralization of gastric acid occurs rapidly (i.e., < 5 minutes) and will last up to an hour

Answer 43

(A) Causes of fetal bradycardia (FHR < 110 beats/min) include hypotension, excessive uterine activity, hypoxemia, acidosis, complete heart block, and some drugs. Atropine readily crosses the placenta but at low doses does not seem to cause fetal tachycardia; at high doses, it may produce tachycardia. The combination of neostigmine, which crosses the placenta slightly, and glycopyrrolate, which does not cross the placenta well, has been associated with fetal bradycardia, which is why neostigmine with atropine is preferred when reversing neuromuscular blockers if a fetus is present. Fetal bradycardias are often associated with early decelerations (head compression with vagal stimulation), late decelerations (fetal hypoxemia with vagal stimulation or myocardial failure), and variable decelerations (umbilical cord compressions with vagal stimulation). Causes of fetal tachycardia (FHR > 160 beats/min) include infection, fever, maternal cigarette smoking, fetal paroxysmal supraventricular tachycardia, and some drugs (ritodrine, terbutaline, atropine)

Answer 44

(A) CP is a nonprogressive disorder of the CNS arising from lesions in the brain that occurred during development (in utero 75%, at birth 10%, soon after birth 15%). CP is associated with impairment of motor function. Mental retardation may or may not be present and is not an essential diagnostic criterion. The cause is unknown and most likely multifactorial. Associated conditions include maternal mental retardation (now called intellectual disability), birth weight of less than 2000 g and fetal malformations, breech presentation (but not breech vaginal delivery), severe proteinuria during the second half of pregnancy, third-trimester bleeding, and gestational age less than 32 weeks, but many other factors may play a role. It occurs in about 2 per 1000 live births. At one time, FHR monitoring was thought to be able to prevent CP, but this has not happened. In fact, among patients with new-onset late deceleration patterns, the false-positive rate is 99% if used to predict the development of CP. This is not to say that intrapartum asphyxial insults do not cause damage; they might, and they probably account for some cases of CP. There is also a very weak association of low Apgar scores and CP; in fact, most children who develop CP had a 5-minute Apgar score that was normal

Answer 45

(B) Seven to eight percent of the adult population in the United States has DM. Type 1 DM (about 10% of diabetics) is a T-cell–mediated autoimmune disease where the patients have an absolute deficiency in insulin secretion. Type 2 DM (about 90% of diabetics) occurs primarily in obese individuals and is associated with an inadequate release of insulin or insulin resistance in target tissues. Type 1 DM occurs in 1 of every 700 to 1000 gestations. Gestational diabetes, which occurs only during pregnancy, is currently seen in about 7% of all pregnancies in the United States. Although substantial advances in the obstetric and anesthetic management of diabetic parturients have been made, maternal and fetal mortality is still higher in these patients than in parturients without diabetes. DKA occurs primarily in Type 1 DM patients and has decreased from 9% to currently around 1% to 2% of Type 1 DM pregnancies. One important goal of insulin therapy in diabetic patients is to avoid both hyperglycemia and hypoglycemia. In general, insulin requirements in Type 1 DM patients initially decrease during early pregnancy to their lowest requirement by around 16 to 18 weeks (10%-20% reduction in dose), then increase above prepregnant values around 26 weeks to reach values that are highest at term (50% above prepregnant dose). The dose requirements then rapidly decrease at the time of delivery. Insulin does not readily cross the placenta and therefore does not have any direct effects on glucose metabolism in the fetus. Glucose, however, readily crosses the placenta. Preeclampsia and large-for-gestational-age fetuses occur more frequently in parturient women with diabetes. Because of fetal macrosomia, cesarean section is more common in diabetic than nondiabetic patients

Answer 46

(D) PDPHs are positional headaches (exacerbated by sitting or standing and relieved with recumbency) that usually present within 48 hours of a dural puncture (but could take up to a week to present) and typically resolve in 2 to 14 days. They are bilateral and typically located in the frontal or occipital regions. In one prospective series of nonobstetric patients with PDPH, symptoms included nausea (60%), vomiting (24%), neck stiffness (43%), ocular changes (photophobia, diplopia, difficulty in accommodation) (13%), and auditory changes (hearing loss, hyperacusis, tinnitus) (12%). Although postpartum seizures have been associated with PDPH, other etiologies are more likely. Seizures, lethargy, fever, nuchal rigidity, focal neurologic deficits (other than listed above), and a unilateral location suggest other headache etiologies

Answer 47

(A) There are several periodic FHR patterns. Accelerations in FHR in response to fetal movement signify fetal well-being. Decelerations are a decrease in FHR of at least 15 beats/min that last at least 15 seconds. Early decelerations are decreases in FHR that are usually less than 20 beats/min and occur concomitantly with uterine contractions. Typically they are smooth and are mirror images of the uterine contractions. They are not associated with fetal compromise and are caused by head compression, which produces a vagal slowing of the FHR. Late decelerations are decreases in FHR that occur 10 to 30 seconds after the onset of a contraction and end 10 to 30 seconds after the end of a contraction. They are due to uteroplacental insufficiency and can result whenever uterine blood flow decreases. The delayed onset is due to the time required to sense a low oxygen tension. The decrease in FHR may be a vagal reflex (mild cases) or may be due to direct myocardial depression from hypoxia (severe cases). Typically, in severe cases, beat-to-beat variability is decreased or absent as well. Variable decelerations are abrupt decreases in FHR that vary in shape, depth, and duration from contraction to contraction. They are thought to be due to transient umbilical cord compression. A sinusoidal pattern is a regular smooth wavelike pattern with no short-term variability. It may be caused by severe fetal anemia or may result from the maternal administration of narcotics

Answer 48

(C) Shivering occurs in 15% to 20% of all normal vaginal deliveries. The frequency increases from 20% to 85% of patients receiving epidural or spinal anesthesia for cesarean deliveries. The postulated reason is that neuraxial anesthesia impairs centrally mediated peripheral vasoconstriction and shivering thresholds and allows greater environmental heat loss (core to peripheral heat redistribution). Intrathecal narcotics (e.g., especially fentanyl with morphine) and epidural narcotics (e.g., fentanyl, sufentanil, meperidine, butorphanol), when added to local anesthetics, decrease the incidence of maternal shivering. Intravenous meperidine (25 mg), clonidine (75 μg), ketanserin (10 mg), magnesium sulfate (30 mg/kg), or dexmedetomidine decrease the incidence of shivering. Warming the epidural anesthesia solution to body temperature has no effect on the incidence of shivering; however, adding epinephrine to the local anesthetic appears to increase the frequency of shivering

Answer 49

(D) The values listed in the question are normal umbilical cord values. The chart is modified from values listed in the references

Answer 50

(D) For all obstetric-related admissions, the incidence of transfusion of blood is less than 1%. The most common reason for transfusion was postpartum hemorrhage. Estimates suggest that about one third of transfusions were not appropriate with current guidelines

Answer 51

(C) Resuscitation guidelines continue to evolve. About 10% of newborns require some resuscitation to assist breathing at birth, whereas about 1% will need extensive resuscitation. If the newborn appears to be term, has good muscle tone, and is breathing or crying, the baby can remain with the mother and can have initial care performed on mother’s chest or abdomen. Initial care consists of drying the newborn, providing warmth, and clearing secretions if needed. If the newborn appears depressed, next open the airway, clear out any remaining oral secretions, then stimulate the newborn by rubbing a towel to completely dry the newborn. If after a minute there is an obvious need for more extensive treatment (e.g., the heart rate is less than 100 beats/min or the newborn is gasping or apneic), then positive-pressure ventilation is started and oximetry and ECG monitoring are suggested. In term newborns, resuscitation is started with air rather than with 100% oxygen. However, preterm newborns (< 32 weeks’ gestation) may need air blended with oxygen to reach adequate oxygen saturations (e.g., at 10 minutes after delivery, the oxygen saturation should be 85%-95%). The oximetry probe should be placed preductally (i.e., on the right wrist) to assess oxygenation. If, after the first minute of life, the heart rate is less than 100 beats/min, one should ensure adequate positive-pressure mask ventilation and consider endotracheal intubation (or the use of a laryngeal mask). The ventilation rate should be 40 to 60 breaths per minute. If the heart rate is now less than 60 beats/min after at least 30 seconds of good positive-pressure ventilation, endotracheal intubation should be performed and 100% oxygen should be used. Chest compressions should then begin (with a chest compression-to-ventilation ratio of 3:1). At this point the newborn receives 30 breaths and 90 compressions/min (e.g., one and two and three and breath). If the newborn is known to have a cardiac etiology, then a higher compression-to-ventilation ratio should be considered (e.g., 15:2). If the heart rate is less than 60 beats/min after chest compressions and positive-pressure ventilation have been started for at least 30 seconds, consider administering epinephrine. The correct dose is 0.01 to 0.03 mg/kg IV or intraosseous (IO) and can be given every 3 to 5 minutes if needed. If the newborn is intubated and IV or IO access has not yet been achieved, consider administering a higher dose of epinephrine such as 0.05 to 0.1 mg/kg down the endotracheal tube (the higher dose is used because blood levels are unpredictable after endotracheal instillation). In a newborn with blood loss, volume expansion is needed and can be achieved with normal saline, Ringer lactate, or type O Rh-negative blood. The initial dose is 10 mL/kg. There is little evidence of any benefit with volume expansion in the absence of blood loss. If after 10 minutes there is no detectable heart rate, it may be appropriate to discontinue resuscitation (although many factors can contribute to continuing resuscitation beyond 10 minutes

Answer 52

(D) Although epidural anesthesia often causes a fall in body temperature (due to the vasodilation and redistribution of body heat and loss to the environment), some women develop a rise in body temperature even though there is no evidence of infection. This rise in body temperature of greater than 38° C (100.4° F) usually occurs only when the epidural was used for at least 4 to 5 hours (frequency of 1%-36% of patients). The etiology of this rise in temperature in some women is unclear but includes three main factors (thermoregulatory, effect of systemic opioids, and inflammation). Epidural anesthesia may decrease sweating and the hyperventilation associated with labor, as well as shivering, which may increase body temperature. The use of IV systemic opioids may decrease the incidence of fever. Inflammation may play an important role because maternal temperatures are similar in women with or without epidural anesthesia when histologic examination of the placentas reveals the absence of placental inflammation. It may be that the temperature rise was merely an association with obstetric factors such as nulliparity with prolonged labor, more frequent cervical examinations, prolonged rupture of membranes, or early chorioamnionitis. The prepregnant blood leukocyte count of 6000/mm3 rises during pregnancy to 9000 to 11,000/mm3. During labor the leukocyte count increases to 13,000/mm3, and during the first postpartum day is on average 15,000/mm3

Answer 53

(B) Although the cause of hypertensive disorders of pregnancy is not known, many factors are associated with a higher frequency of hypertensive disorders of pregnancy. Factors include nulliparous woman, age (especially < 20 years and > 40 years), family history of hypertensive disorders of pregnancy or a previous history of hypertensive disorders of pregnancy, some chronic medical conditions (e.g., hypertension, diabetes, obesity, thrombotic vascular disease, systemic lupus erythematosus), some obstetric conditions (e.g., placental abruption, intrauterine growth restriction, fetal death), and conditions in which the uterus is rapidly enlarging (e.g., multiple gestations, polyhydramnios, hydatidiform mole). Although smoking is associated with more adverse pregnancy outcomes (e.g., ectopic pregnancies, placenta previa, placental abruption, FHR abnormalities, low birth weight, respiratory impairment in the newborn, and sudden infant death syndrome (SIDS)), there appears to be a 30% to 40% lower incidence of hypertensive disorders of pregnancy in women who smoke. The protective effect appears to be dose related, with heavy smokers having a lower frequency than those who smoke fewer cigarettes. In addition, women who are more physically active have a lower frequency of hypertensive disorders of pregnancy than sedentary women

Answer 54

(D) Aortocaval compression, as its name suggests, produces both compression of the aorta (increase in afterload) as well as compression of the vena cava (decrease in venous return). The patient’s response is variable. Although some women have no symptoms, up to 15% of pregnant patients at term will, over several minutes in the supine position, develop hypotension and bradycardia (also called the supine hypotension syndrome). Some women will actually show an increase in brachial artery blood pressure due to the increase in afterload. These women may have a condition referred to as concealed hypotension (blood pressure above the compression that is adequate but blood pressure below the compression that is reduced). Because the blood supply to the uterus is distal to the aortic compression and uterine blood flow is decreased, the fetus may develop fetal distress. Other signs and symptoms of aortocaval compression include nausea, vomiting, pallor, sweating, and changes in cerebration. See also Question 701

Answer 55

(B) Cocaine can produce life-threatening complications that are usually related to the accumulation of catecholamines, and patients may present with the classic signs of toxemia (i.e., hypertension and proteinuria) as well as chest pain. The typical half-life of cocaine is 30 to 90 minutes, but the acute effects can last as long as 6 hours. Because some states consider in utero cocaine exposure a form of child abuse that requires physicians to report positive drug tests in pregnant women, many patients who use cocaine have no prenatal care. Urine tests may be positive for 24 to 72 hours after cocaine use (depending on the amount used). Life-threatening events are more common with general than regional anesthesia. The most frequent problem with induction of general anesthesia is severe hypertension. Arrhythmias, myocardial ischemia, and tachycardia may also occur with the induction of general anesthesia. Labetalol and nitroglycerin have been used to treat these conditions. The MAC level is increased in patients who are acutely intoxicated, whereas patients chronically abusing cocaine have a lower MAC (due to the depletion of catecholamines). These patients are at risk for hypotension, which is commonly seen after the induction of regional anesthesia for cesarean section. Ephedrine may not be an effective vasopressor in these catecholamine-depleted patients. Phenylephrine, a direct-acting drug, is a better vasopressor

Answer 56

(C) In cases of emergency cesarean section when general anesthesia is contraindicated (e.g., poor airway when one questions one’s ability to intubate and/or ventilate the patient) and neuraxial anesthesia is contraindicated (e.g., severe hypovolemia or coagulopathy), emergency infiltration anesthesia is acceptable. All of the choices are correct except the choice of a local anesthetic. As the surgeon will be injecting a fair volume of local anesthetic (often 100 mL), and as bupivacaine has a slow onset and potentially dangerous cardiac toxicity with large doses, bupivacaine is a poor choice. A dose of 0.5% lidocaine (plasma half-life of 90 minutes) is often used because it is readily available and relatively safe. Chloroprocaine may be safer because it also has a fast onset and its plasma half-life is extremely short (23 seconds). Both midazolam and ketamine may lead to some amnesia for the patient, which may be advantageous in this emergency situation; however, too much of the IV drugs could obtund the patient and may lead to aspiration of gastric contents. A good coach at the head of the bed may be invaluable for reassuring the patient as to the care

Answer 57

(A) The most common complication after a spinal or epidural anesthetic is placed is systemic hypotension. Because the cardiac output is influenced by four main factors (preload, afterload, contractility, and heart rate and rhythm), treatment is directed at these factors. First, consider more left uterine displacement (which can increase venous return and preload). Next, administer more IV fluids (without dextrose such as lactated Ringer or saline solution) to increase preload if the amount of fluid used to prehydrate the patient before the block is thought to be inadequate. In this case the amount of prehydration with saline is an appropriate amount, but a little more non-dextrose containing fluid may be helpful. Intravenous fluids with dextrose are used only for maintenance fluids and should not be used to prevent or treat hypotension from regional anesthesia because the fluid load with dextrose causes significant maternal and fetal hyperglycemia and hyperinsulinemia. After delivery, the sugar supply for the newborn stops but the insulin response continues, often causing fetal hypoglycemia after delivery. It should be noted that 5% albumin solutions are expensive and are not recommended for routine use to treat hypotension. Vasopressors and/or drugs that increase cardiac contractility are commonly needed to increase afterload. Initial laboratory studies with pregnant ewes suggested that ephedrine was a better choice than phenylephrine or other α-adrenergic agonists when looking at changes in uterine blood flow. In these initial studies, the blood pressure was raised from normal to higher levels, and ephedrine was the drug of choice because phenylephrine decreased uterine blood flow, whereas ephedrine did not. However, raising a normal pressure to higher levels is not the same thing as raising a low blood pressure to normal. In more recent human studies looking at ephedrine and phenylephrine use, no difference was noted in the prophylactic or therapeutic use of these drugs for maternal hypotension. It was also noted that maternal bradycardia was more common with maternal phenylephrine administration, whereas maternal tachycardia was more common with maternal ephedrine administration; also, neonatal arterial pH was slightly higher when phenylephrine was used compared with ephedrine. Why this occurs is unclear but may be related to ephedrine’s ability to cross the placenta, causing β-adrenergic stimulation in the newborn (F/M blood ratio is 0.7 for ephedrine and 0.2 for phenylephrine). In this patient who has left uterine displacement, adequate IV hydration, and a heart rate of 110 beats/min, phenylephrine would be the preferred vasopressor. If the mother has hypotension with bradycardia, ephedrine might be a better choice. Epinephrine is rarely needed but should be available and used when there is severe hypotension that is not responsive to phenylephrine or ephedrine, especially when there is associated fetal bradycardia

Answer 58

(D) A threatened abortion is defined as uterine bleeding without cervical dilation before 20 weeks’ gestation. Bleeding may be accompanied by uterine cramps or backache. Half of these cases will go on to spontaneously abort. An inevitable abortion has cervical dilation and/or rupture of membranes and will spontaneously abort. A complete abortion occurs when there is complete expulsion of the fetus and the placenta, and in these cases there is no need for a dilation and curettage (D&C). If there is only partial expulsion of tissue, as in this case, an incomplete abortion has occurred, and this requires a D&E to remove the remaining fetal or placental tissue. In these cases the cervix has usually dilated some and the patient usually can be managed with some mild sedation, because the most painful part of a D&E is cervical dilation. A paracervical block can be most useful for pain control during the procedure if the cervix needs to be dilated. A fetal death that is unrecognized for several weeks is called a missed abortion, and if this occurs at an advanced gestational age, DIC may occasionally result. A habitual or recurrent abortion refers to the occurrence of three or more consecutive spontaneous abortions

Answer 59

(D) Accidental dural punctures with an epidural needle occur in about 1% of epidural attempts, and about a half of these patients develop a postdural puncture headache. Several techniques have been tried in an attempt to decrease the incidence of PDPHs but without success. Lying horizontally is helpful in relieving PDPHs, but prophylactic bed rest has not decreased the incidence of PDPH. Although avoidance of dehydration is recommended, excessive fluid intake has not been shown to decrease the incidence of PDPH. Epidural blood patches have proven successful in treating PDPH. However, the prophylactic injection of blood into the epidural space after the epidural block has worn off does not appear to significantly decrease the incidence of headaches but may decrease the duration of the headache. Keep in mind that the injection of blood through a contaminated epidural catheter may increase the risk of infection because blood is an excellent culture medium. For treatment, however, epidural blood patches are very successful, with better success rates if performed several hours after delivery compared with immediately after the delivery. Perhaps the leakage of cerebrospinal fluid into the epidural space dilutes the blood, making the patch weaker. Caffeine has been suggested by some studies to decrease the incidence of PDPHs, but other studies show no prophylactic benefit

Answer 60

(B) Earlier diagnosis of complete molar pregnancies has decreased the incidence of medical complications. However, excessive uterine size occurs in up to one half of patients with a complete molar pregnancy and is associated with a high incidence of medical complications. Medical complications when the uterine size is greater than 14 to 16 weeks’ gestational size include ovarian theca-lutein cysts (4%-50%), hyperemesis gravidarum (15%-30%), hypertensive disorders of pregnancy (11%-27%), anemia (hemoglobin < 10 g/dL) (10%-54%), acute cardiopulmonary distress (6%-27%), malignant sequelae (metastasis) (4%-36%), and hyperthyroidism (1%-7%)

Answer 61

(B) Several cases of maternal cardiac arrest have occurred in pregnant women who were administered bupivacaine (Marcaine, Sensorcaine). Typically, the patients received an unintentional IV bolus of 0.75% bupivacaine intended for the epidural space. They had a brief grand mal seizure followed by cardiovascular collapse. Successful treatment was often prolonged and involved basic resuscitation (intubation, ventilation with 100% oxygen, cardiac compression with left uterine tilt, defibrillation, epinephrine, vasopressin, atropine), as well as rapid delivery of the fetus (if possible within 4-5 minutes). Delivery of the fetus makes successful resuscitation of the mother more likely. Incremental small injections of local anesthetic looking for toxicity should decrease the chance for cardiovascular collapse. Bupivacaine 0.75% now is considered contraindicated for use in the epidural space of parturients. Both levobupivacaine (Chirocaine) and ropivacaine (Naropin) were developed to have a long duration of action, like bupivacaine, but with less cardiac toxicity. Although these compounds have less cardiac toxicity than bupivacaine, they are more cardiac toxic than lidocaine (intermediate duration of action) and chloroprocaine (short duration of action)

Answer 62

(D) Treatment of the pregnant patient who develops cardiovascular collapse from LAST consists of positioning the patient with left lateral displacement and preparing for an emergency cesarean delivery. Consider delivery of the infant if the mother cannot be resuscitated within several minutes because delivery of the infant makes it easier to resuscitate the mother. Current (2017) ASRA guidelines for LAST for a patient with cardiovascular collapse include the following: ● Stop injecting the local anesthetic. ● Get help (Call for lipid emulsion, alert nearest cardiopulmonary bypass team because resuscitation may be prolonged). ● Manage airway (Ventilate with 100% oxygen, avoid hyperventilation, and place an advanced airway device if necessary). ● Control seizures (Benzodiazepines are preferred and avoid large doses of propofol, especially in hemodynamically unstable patients). ● Treat hypotension and bradycardia; if pulseless, start CPR. ● Start IV lipid emulsion (Intralipid 20%) therapy (initial bolus of Intralipid is 1.5 mL/kg over 2-3 minutes, or about 100 mL in an adult). The bolus dose is followed by a continuous infusion of 0.25 mL/kg (ideal body weight)/hr. You can repeat the bolus dose one or two times for persistent cardiovascular collapse and then double the rate in a continuous infusion rate if the blood pressure remains low. Continue the infusion for at least 10 minutes after cardiovascular stability is attained. The upper limit of Intralipid (20%) is 10 mL/kg over 30 minutes. ● Continue to monitor the patient for at least 4 to 6 hours after a cardiovascular event and at least 2 hours after a limited CNS event. ● AVOID the use of vasopressin, calcium channel blockers, β-blockers, and other local anesthetics. ● If you need epinephrine, the dose should be reduced to ≦ 1 μg/kg epinephrine. ● Report LAST

Answer 63

(A) TNS, formerly called transient radicular irritation (TRI), occurs most commonly after spinal anesthesia with lidocaine (Xylocaine). Symptoms include back pain that develops after the block resolves and radiates to the buttocks and legs. The pain is not associated with motor or sensory loss or electromyographic changes. It can be severe, requiring hospital admission of outpatients, and typically resolves within 1 to 4 days. It appears to occur more commonly when outpatients are operated on in the lithotomy position and appears to be less likely when patients are pregnant

Answer 64

(D) When dealing with an urgent cesarean section in a patient with a well-functioning labor epidural, raising the level of anesthesia is often chosen. Of the commonly used local anesthetics, 3% 2-chloroprocaine with epinephrine 1:200,000 and 2% lidocaine with epinephrine 1:200,000 have much faster onsets of action than bupivacaine or levobupivacaine, which have relatively slow onsets of action. Because of the slow onset of action of bupivacaine or levobupivacaine, they are not recommended to raise an existing labor analgesic level for an urgent cesarean delivery. Alkalinization of the local anesthetic with bicarbonate shifts more of the local anesthetic molecules to the nonionized and more lipid-soluble form for a faster onset (and a more solid block); however, it does take a little time to mix the solution. Typically, 1 mL of 8.4% sodium bicarbonate (1 mEq/mL) is added to each 10 mL of 3% 2-chloroprocaine with epinephrine 1:200,000 or 2% lidocaine with epinephrine 1:200,000, and those solutions in a dose of 15 to 20 mL can usually raise a labor epidural to cesarean levels in < 5 minutes. If you do not add the bicarbonate to 2% lidocaine with epinephrine 1:200,000, the onset time is twice as long, or about 10 minutes. Fentanyl can be added (75-100 μg) to the local anesthetic solution for a more solid block and for some postoperative analgesia

Answer 65

(B) The blood level of a local anesthetic is based on the absorption of the local anesthetic into the bloodstream and on the local anesthetic’s metabolism. Ester local anesthetics (e.g., procaine, chloroprocaine, and tetracaine) undergo metabolism by pseudocholinesterase and other plasma esterases, whereas amide local anesthetics (e.g., lidocaine, mepivacaine, prilocaine, bupivacaine, levobupivacaine, ropivacaine, and etidocaine) are not metabolized in the bloodstream but require liver metabolism and have much longer half-lives. If chloroprocaine (Nesacaine) is injected directly into plasma, the in vitro half-life is 11 to 21 seconds in maternal plasma and 43 seconds in fetal plasma. After an epidural injection, where there is absorption of local anesthetic from the injection site as well as metabolism, the maternal half-life for chloroprocaine is < 7 minutes, for lidocaine is 110 to 120 minutes, for ropivacaine is 5 to 6 hours, and for bupivacaine is 10 to 12 hours

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