Flashcards in Obstetric Anesthesia Deck (90):
T or F: beyond the 5th month of pregnancy, the FRC is decreased by 80% and oxygen consumption increases by 30-40%.
T or F: during apnea, pregnant women become hypoxemic rapidly because of limited FRC and increased O2 consumption.
True- effective preoxygenation can be achieved in pregnant women with either 3 minutes of tidal breathing or deep breathing for 1 minute.
T or F: pregnancy is a state of relative hypercoagulability. Pregnant patients needing anticoagulation are often treated with LMWH due to efficacy, maternal safety, ease of administration, and lack of placental transfer to the fetus.
How many hours should pass before neuraxial catheter placement in a patient who has received a) THERAPEUTIC LMWH and b) PROPHYLACTIC LMWH?
ASRA guidelines state that neuraxial placement should occur no sooner than 24 hours following a THERAPEUTIC dose of LMWH. Neuraxial placement should occur no sooner than 12 hours following a PROPHYLACTIC dose of LMWH.
What is a common side effect of intrathecal fentanyl and morphine?
Pruritis (especially of the nose and trunk) and nausea, although pruritis is more common.
Why is it beneficial to administer intrathecal fentanyl to obstetric patients?
Results in profound visceral pain relief. Fentanyl is highly lipophilic and rapidly leaves CSF and penetrates the spinal cord and systemic circulation. In contrast to local anesthetics, fentanyl does NOT contribute to motor block or difficulty pushing. Unlike the more hydrophilic morphine, fentanyl does not have significant rostral spread within the intrathecal space and is therefore unlikely to contribute to maternal depression.
T or F: epidural administration of fentanyl results in significant systemic absorption. It can cross the placenta and result in a transient decrease in fetal heart rate variability, which can make interpretation of fetal heart rate patterns challenging.
True, however, it is NOT thought to contribute to newborn respiratory depression under normal circumstances.
What is the leading cause of postpartum hemorrhage?
What is uterine atony?
Atony results when there is failure of adequate uterus contraction after delivery. Postpartum hemostasis involves the release of endogenous uterotonic factors.
What is the most common indication for a peripartum blood transfusion?
What is tocolytic therapy? When is it administered, and name a few tocolytics.
Tocolytics are administered to halt premature labor. They relax uterine muscle, making it more difficult to contract after delivery. Terbutaline and indomethacin are examples of tocolytics.
What are reasons that uterine atony may occur?
pre-delivery use of oxytocin, over-distension of uterus due to polyhydramnios or multiple gestations, and chorioamnionitis.
What are the most common morbidities encountered in obstetrics?
maternal hemorrhage and severe preeclampsia
T or F: regardless of the time of last meal, all pregnant patients are considered to have a full stomach.
T or F: nearly all sedatives and opioids cross the placenta and affect the fetus.
During the first stage of labor, at what level should epidural blockade be to provide adequate pain relief?
During the second stage of labor, at what level should epidural blockade be to provide adequate pain relief?
Name three causes of maternal hemorrhage.
Causes include placenta previa, abruptio placenta, and uterine rupture.
T or F: When dilute mixtures of local anesthetic and opioid are used, epidural analgesia has little effect on the rate of labor.
Why has the IV use of meperidine for maternal pain relief been halted?
The placental transfer of the active metabolite normeperidine has been implicated in neonatal respiratory depression, as it has a long elimination half life.
What is the most common side effect from neuraxial analgesia?
Hypotension resulting from sympathectomy
T or F: maternal hypocapnia from hyperventilation causes uterine artery vasoconstriction, resulting in decreased blood flow.
True- this happens in the setting of hyperventilation. Hyperventilation and hypocapnia lead to leftward shift of maternal oxygen-hemoglobin dissociation curve, resulting in ↓fetal arterial oxygen tension
Why is effective epidural analgesia important in severe pre-eclamptics?
Effective epidural analgesia can increase uterine blood flow in the parturient with severe preeclampsia by up to 80%
What are risk factors for placenta previa?
prior c-section, uterine surgery, elective abortion, smoking, multiparity, cocaine abuse, multiple gestation
What is a placenta accreta?
an abnormally deep attachment of the placenta to the myometrium.
T or F: 75-80% of maternal hemorrhage is due to uterine atony.
What is uterine atony?
Loss of tone in the uterine musculature. Normally, compression of the uterine muscles compresses the vasculature and reduces flow. This increases the likelihood of coagulation and reduces bleeding.
What is the treatment for uterine atony?
Uterine massage, then oxytocin, then methylergonovine
What is placental abruption?
The placental lining has separated from the uterus of the mother
What is methylergonovine?
A smooth muscle constrictor that mainly acts on the uterus. Commonly used to prevent excessive bleeding following childbirth. CONTRAINDICATED in patients with HTN, preeclampsia, and pulmonary hypertension.
Methergine rhymes with hypertension. More likely to cause HTN when administered IV, so administer IM.
What is carboprost (Hemabate)? In which population of patients should you be cautious of administering this drug?
A prostaglandin analogue that can trigger smooth muscle contractions and abortion in early pregnancy. Reduces postpartum bleeding. Exert caution when giving to patients with asthma, as may trigger bronchospasm.
What is oxytocin?
a hormone used for labor induction, has replaced methylergonovine for the treatment of uterine atony. Can cause maternal water intoxication.
What is misoprostol?
a synthetic prostaglandin used to induce labor and to induce abortion. Causes uterine contractions and thinning of the cervix. Most commonly reported side effect is diarrhea, fever s also common.
What is terbutaline?
A beta-2 adrenergic receptor agonist used as a tocolytic to delay preterm labor.
Side effects include maternal tachycardia, nervousness, tremors, headache, hyperglycemia, hypokalemia, and pulmonary edema. Fetal side effects include tachycardia, neonatal hypoglycemia, and hyperinsulinemia.
What are three indications to give magnesium sulfate in obstetric anesthesia?
Magnesium sulfate has three uses in obstetrics:
1- seizure prophylaxis
2- fetal neuroprotective agent in cases of imminent preterm delivery
3- as a tocolytic agent to terminate preterm contractions, can also delay labor by inhibiting uterine muscle contraction in the case of premature labor, to delay preterm birth.
What are signs and symptoms of hypermagnesemia? What is the treatment? What are risks with giving magnesium in patients with severe preeclampsia?
impaired breathing, decreased respirations, hypocalcemia, arrythmias, asystole.
magnesium acts as a physiologic calcium blocker --> immediate treatment for reversal of hypocalcemia is calcium gluconate, 500 mg IV
severe preeclampisa patients have renal impairment and thus reduced elimination of serum magnesium.
What are the stages of labor?
Latent, active, transition, fetal descent, second stage, neonatal delivery, third stage, placental delivery
Describe the first stage of labor.
The first stage of labor is responsible for getting the cervix to achieve maximal cervical dilation. There are three components to it, the latent portion, active portion, and transition portion.
Describe the latent portion of the first stage of labor.
In the latent portion of the first stage of labor, contractions become more frequent, stronger, and gain regularity, and most of the change of the cervix involves thinning, or effacement. Rupture of membranes may occur here.
Describe the active portion of the first stage of labor.
the phase of the most rapid cervical dilatation. For most women this is from 3 to 4 centimeters of dilatation until 8 to 9 centimeters of dilatation. The active phase is the most predictable, lasting an average of five hours in first-time mothers and two hours in mothers who have birthed before.
Describe the transition portion of the first stage of labor.
The cervical dilation continues, but at a slower pace, until full dilation. This is also a phase of more rapid descent, when the baby is passing lower into the pelvis and deeper into the birth canal. The deceleration phase is also called transition, and, in mothers with no anesthesia, it’s often punctuated by vomiting and uncontrollable shaking. These symptoms can be frightening to watch, but they’re a part of normal birth, and they signal that the first state is almost completed.
Describe stage two of labor.
The second stage is the delivery of the infant. During the second stage, mom actively pushes out the baby. For first time mothers, this can take two to three hours, so it’s important to save your energy and pace yourself. For second babies and beyond, the second stage often lasts less than an hour – and sometimes, only a few minutes.
Describe stage three of labor.
The third stage of labor is the passage of the placenta, which can be immediate, or take up to thirty minutes. The process may be sped up naturally by breastfeeding (which releases oxytocin), or medically by administering a drug called pitocin.
T or F: IV nitroglycerin can be used to relax the cervical os if it has contracted after delivery of the neonate.
True- bolus as 50 micrograms, have phenylephrine ready
preeclampsia develops when a patient develops both hypertension and proteinuria. Typically occurs after the 24th week of pregnancy
How does magnesium sulfate affect neuromuscular blockade and the NMJ?
1- inhibits the release of Ach at the NMJ
2- decreases the sensitivity of the NMJ to Ach
3- depresses the excitability of the muscle fiber membrane
4- increases the potency and duration of nondepolarizers
What are potential complications of the long term use of NSAIDs in pregnant women?
Fetal oligohydramnios, premature in utero closure of the ductus arteriosus, maternal peptic ulcers, maternal renal dysfunction
T or F: capillary engorgment of the mucosa and edema of the oropharynx, larynx, and trachea may result in a difficult intubation.
True- any manipulation of the upper airway such as suctioning, insertion of airways, or laryngoscopy may cause edema, bleeding, and upper airway trauma. Because of the particularly friable mucosa of the nasopharynx, instrumentation of the nose should be avoided if at all possible.
What are causes of late decelerations?
uteroplacental insufficiency, aortocaval compression, and increased uterine tone.
Late decelerations begin 10-30 seconds after the beginning of uterine contractions and end 10-30 seconds after the end of uterine contractions.
What are causes of variable decelerations?
umbilical cord compressions, fetal anemia, maternal use of narcotics
Variable decelerations vary in shape and duration from contraction to contraction.
What is the P50 of fetal hemoglobin?
T or F: smoking is associated with a reduced risk of preeclampsia.
T or F: as the number of c-sections a patient has had in the past increases, so does their risk of having placenta accreta.
T or F: pregnancy is associated with enhanced platelet turnover and consumption, referred to as gestational thrombocytopenia.
True- likely increased platelet production compensates for the greater activation, allowing the platelet count to remain within normal limits.
T or F: Epidural analgesia for labor has been demonstrated in some studies to produce a small increase in maternal core temperature, typically < 1°C.
The rise in maternal core temperature seen with epidural analgesia for labor is typically gradual and occurs over several hours. The use of epidural analgesia for labor has also been associated with intrapartum fever (temperature >38°C). An intrapartum fever developed in 15% of women receiving epidural analgesia for labor, compared to 1% in those not receiving epidural anesthesia.
What are three signs and symptoms of amniotic fluid embolism?
Respiratory distress, coagulopathy, cardiovascular collapse
T or F: The pathophysiology of AFE does not involve a true embolic event, as occurs with PE or venous air embolism, but rather involves significant pulmonary artery vasospasm in association with the introduction of amniotic fluid into the maternal circulation.
True- AFE may be an anaphylactoid reaction resulting from the presence of vasoactive substances in the amniotic fluid. In the early phase of AFE, TEE has documented severe pulmonary artery vasoconstriction and right-sided heart failure.
What clinical symptom can differentiate PE from amniotic fluid embolism?
The rapid development of coagulopathy and DIC, which is not present in a PE.
T or F: pregnant women have decreased total lung capacity, FRC, expiratory reserve volume, and residual volume. Inspiratory reserve volume stays roughly the same.
T or F: both hormonal and anatomic factors are responsible for a decrease in lower esophageal sphincter pressure by the third trimester.
T or F: gastric emptying, volume, and gastric pH are unchanged during pregnancy.
True- may be significantly altered during active labor with gastric emptying and pH decreasing, and gastric volume increasing.
What is the formula for uterine blood flow?
Uterine blood flow = uterine perfusion pressure (uterine artery pressure - uterine venous pressure) / uterine vascular resistance
What can cause a decrease in uterine blood flow?
A decrease in uterine blood flow can result either from a decrease in uterine perfusion pressure or an increase in uterine vascular resistance.
What can cause increases in uterine venous pressure?
Increases in uterine venous pressure can result from:
1- uterine contractions
2- uterine hypertonus (eg, excessive oxytocin, placental abruption)
3- Valsalva maneuver
4- vena cava compression secondary to supine position.
What can cause decreased uterine arterial pressure?
Possible etiologies of maternal hypotension leading to decreased uterine arterial pressure include:
1- aortocaval compression due to supine position
4- sympathetic blockade
5- drugs (anesthetic and nonanesthetic).
What can cause increased uterine vascular resistance?
Causes of increased uterine vascular resistance include:
1- increased endogenous catecholamine levels (caused by pain or stress)
2- exogenous epinephrine administered systemically
3- high concentrations of local anesthetic (eg, paracervical block).
T or F: epidural labor analgesia produces no change or an increase in uteroplacental blood flow.
Epidural labor analgesia produces either no change or an increase in uteroplacental blood flow, provided sympathectomy-induced hypotension does not occur.
The excellent pain relief provided by this technique prevents hypocapnia caused by pain-induced hyperventilation and increases in endogenous catecholamine levels, factors that can decrease uteroplacental perfusion.
T or F: Pregnant women demonstrate an increase in minute ventilation.
True- this increase in minute ventilation is primarily due to a 40% increase in the tidal volume as well as a small increase (~15%) in the respiratory rate during pregnancy. Elevated levels of serum progesterone have been shown to stimulate respiratory drive and minute ventilation.
The thoracic cage increases in size in both the AP and transverse diameters; lung volumes begin to significantly change around the third to fifth month of pregnancy. As the uterus enlarges, the diaphragm is forced cephalad and functional residual capacity (FRC) decreases. In the upright position, FRC can decline by 20%–30% from prepregnancy values by term. This is exacerbated by the supine or Trendelenburg position.
Total lung capacity and vital capacity are maintained (or only slightly decreased) in pregnancy because of compensatory changes in various lung volumes. In addition, closing capacity remains relatively unchanged. However, closing capacity may exceed FRC (especially in the supine position), leading to small airway closure, atelectasis, and V/Q mismatch. Therefore, the combination of reduced FRC, increased oxygen consumption, and possible airway closure during tidal volume breathing causes parturients to desaturate at a much faster rate than non-pregnant women.
What are two anesthesia-related concerns when placing a neuraxial catheter in a pre-eclamptic patient?
(1) the potential for a large drop in blood pressure due to depleted intravascular volume and sympathetic blockade
(2) peridural hematoma in women with severe thrombocytopenia.
What are pregnant patients with Marfan's syndrome at risk for? How should they be worked up?
Pregnancy and the postpartum period is a high-risk time for aortic dissection and rupture in women with Marfan's syndrome. Patients with Marfan's should deliver in a tertiary center with access to a cardiothoracic surgeon should dissection occur.
T or F: Vaginal delivery is preferred for patients with MFS who have an aortic diameter that remains ≤40 mm if there are no obstetrical indications for cesarean delivery. In women with MFS who have an ascending aorta diameter ≥40 mm and ≤45 mm vaginal delivery is suggested, though some prefer cesarean delivery in this setting. Cesarean delivery is preferred in patients with an aortic diameter >45 mm.
T or F: Beta blockers, preferably labetalol or metoprolol, should be used throughout pregnancy in an attempt to minimize aortic dilatation and the risk of aortic dissection in all Marfan's syndrome patients.
True- antihypertensives like nitroprusside, nifedipine, and nitroglycerin have been used successfully in patients with pregnancy-induced hypertension, but all have direct effects on smooth muscle like the uterus and are associated with increased postpartum hemorrhage.
T or F: Plasma albumin concentrations decrease during pregnancy. Free fractions of protein-bound drugs increase with decreasing albumin levels.
What are the most important physiologic changes during labor?
During active labor, cardiac output increases by 40% above prelabor values. Immediately after delivery cardiac output sharply increases, reaching 75% of prelabor values. This is mainly caused by autotransfusion during uterine contractions, particularly after delivery of the placenta.
Why is regional preferred over general anesthesia in the setting of a preeclamptic patient undergoing a c-section?
The major concerns associated with general anesthesia (for cesarean delivery) are a transient spike in blood pressure during intubation (response to noxious stimuli), hypotension (from reduction in cardiac output and systemic vascular resistance), and difficult or failed intubation because of oropharyngeal edema.
T or F: NSAIDs such as ketorolac are contraindicated during pregnancy and have no role in the treatment of labor pain.
True- they can cause closure of the ductus arteriosus in utero, leading to rapid fetal demise.
T or F: The risk of placenta accreta in women with previa increases from 3% in primary cesarean section to 61% in quaternary section.
True- When placenta accreta is suspected or known, delivery is usually scheduled at 36 to 37 weeks’ gestation. Under controlled, elective conditions, complications can be minimized. Placenta accreta is becoming the leading cause of cesarean hysterectomy.
What is the average blood loss in a patient with placenta accreta?
When evaluating a patient for possible post-dural puncture headache, what are things to take into consideration?
Be able to differentiate migraine, tension-type, cluster, and post-dural puncture headache. Both migraine and tension-type headaches are very common post-partum and should be considered before diagnosing a post-dural puncture headache.
Is pseudortumor cerebri a contraindication for neuraxial anesthesia?
No- you can still administer a spinal anesthetic in a patient with idiopathic intracranial hypertension.
T or F: prior to delivery of the infant, high values of nitrous oxide (>50%) should be avoided in order to decrease the risk of diffusion hypoxia.
What percentage of all pregnancies are affected by preeclampsia?
5-9% and third leading cause of death in pregnancy in the US
What is the blood loss associated with cesarean delivery?
Is it safe to administer ACE-inhibitors during the second or third trimesters of pregnancy?
No- ACE inhibitors can cause injury and even death to the developing fetus.
When administering reversal in pregnant patients, which combination do you give?
neostigmine and atropine- glycopyrrolate does not cross the placenta while neostigmine does, possibly leading to fetal bradycardia.
T or F: maternal smoking can contribute to fetal tachycardia?
Failed intubation is how many times more common in the obstetric population as compared to the general population?
8 times more common
T or F: 2-chloroprocaine administered epidurally appears to decrease the quality and duration of subsequently administered fentanyl or morphine.
Neuraxial analgesia is believed to increase which stage of labor?
the second stage of labor