Obstetric Anesthesia Flashcards
T or F: beyond the 5th month of pregnancy, the FRC is decreased by 80% and oxygen consumption increases by 30-40%.
True
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.
True-
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?
uterine atony
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?
uterine atony
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.
True
T or F: nearly all sedatives and opioids cross the placenta and affect the fetus.
True
During the first stage of labor, at what level should epidural blockade be to provide adequate pain relief?
T12/L1
During the second stage of labor, at what level should epidural blockade be to provide adequate pain relief?
T10-S4
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.
True
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.
True
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.