Obstetric Pharmacology Flashcards
How is MAC affected by pregnancy?
By 8-12 weeks of pregnancy, the MAC for volatile anesthetics is
decreased and appears to parallel the rising progesterone
levels.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1147.
You have administered large doses of meperidine to
a laboring parturient and now fear respiratory
depression in the neonate. Can you give naloxone
to the mother before delivery to prevent respiratory
depression in the infant?
Yes, theoretically you can do this, but it is not recommended.
Administering naloxone to the mother at this point would
reverse her analgesia at a time she needs it most. Doing so
has resulted in pulmonary edema and even cardiac arrest in the
mother. It is recommended to administer naloxone directly to
the neonate at a dose of 0.1 mg/kg IM.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1150.
What is the preferred drug for seizure prophylaxis in
obstetric patients with preeclampsia?
Magnesium is the drug of choice for seizure prophylaxis in
preeclamptic patients. It works at the NMDA receptor and is
associated with a decrease in systemic vascular resistance and
an increase in the cardiac index.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 564.
Can ketamine be used to provide analgesia during
labor?
Yes, but large doses can produce unacceptable levels of
amnesia and neonatal depression. Ketamine 0.2-0.4 mg/kg can
provide supplemental analgesia for an inadequate regional
anesthetic without producing neonatal depression.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1150.
How long after intravenous or intramuscular
administration would you expect to see the maximal
maternal and neonatal respiratory depressant effects
of meperidine?
Maximal maternal and fetal respiratory depression is seen in 10-
20 minutes following IV administration of meperidine and 1-3
hours following IM injection.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 847.
What is the recommended dose of nalbuphine in a
laboring parturient?
The recommended dose of nalbuphine is 10 mg IV or IM.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1150.
What is the recommended IV or IM dose of
butorphanol in a laboring patient?
The recommended dose of butorphanol is 1-2 mg IV or IM.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1150.
What are the advantages of the use of butorphanol
and nalbuphine in laboring patients?
Both of these drugs have lower incidences of nausea, vomiting,
and dysphoria. They also have a ceiling effect on the degree of
respiratory depression they produce. Also, their metabolites are
inactive.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1150.
What is the elimination half-life of meperidine in the
neonate?
62 hours
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1150.
How does the maternal administration of meperidine
affect fetal heart rate?
It can produce decreased beat-to-beat variability and fetal
tachycardia.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1150.
What are the major side effects of meperidine
administration to parturients?
It has a high incidence of nausea and vomiting, maternal
sedation, orthostatic hypotension, and can produce neonatal
depression.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1149-1150.
How quickly will intravenous meperidine produce
analgesia in a laboring parturient?
Meperidine produces analgesia in about 5-10 minutes.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1149.
What muscle relaxant drugs cross the placenta?
None of the neuromuscular relaxants cross the placenta.
Chestnut DH, Polley LS, Tsen LC, Wong CA. Chestnut’s
Obstetric Anesthesia. Philadelphia, PA: Mosby Elsevier; 2009:
63.
Does heparin cross the placenta?
No.
Chestnut DH, Polley LS, Tsen LC, Wong CA. Chestnut’s
Obstetric Anesthesia. Philadelphia, PA: Mosby Elsevier; 2009:
63
What antihypertensive agents cross the placenta?
Beta-blockers, nitroprusside, and nitroglycerin all cross the
placenta.
Chestnut DH, Polley LS, Tsen LC, Wong CA. Chestnut’s
Obstetric Anesthesia. Philadelphia, PA: Mosby Elsevier; 2009:
63.
Does ephedrine cross the placenta?
Yes. Ephedrine causes similar increases in blood pressure,
heart rate, cardiac contractility, and cardiac output, but because
it is a noncatecholamine, ephedrine has a longer duration of
action than epinephrine. It is also less potent. Ephedrine does
not decrease uterine blood flow, however, which makes it the
preferred vasopressor for obstetric cases.
Chestnut DH, Polley LS, Tsen LC, Wong CA. Chestnut’s
Obstetric Anesthesia. Philadelphia, PA: Mosby Elsevier; 2009:
63.
Do intravenous and inhaled induction medications
cross the placenta?
Yes. This includes propofol, thiopental, local anesthetics,
inhalational anesthetics, nitrous oxide, benzodiazepines, and
opioids.
Chestnut DH, Polley LS, Tsen LC, Wong CA. Chestnut’s
Obstetric Anesthesia. Philadelphia, PA: Mosby Elsevier; 2009:
63.
What anticholinergic drugs cross the placenta?
Scopolamine and atropine cross the placenta, but
glycopyrrolate does not.
Chestnut DH, Polley LS, Tsen LC, Wong CA. Chestnut’s
Obstetric Anesthesia. Philadelphia, PA: Mosby Elsevier; 2009:
63.
How does pregnancy affect the height of neuraxial
anesthetics?
Believed to be due to a decrease in the epidural space due to
venous congestion and/or progesterone-induced sensitivity to
local anesthetics, pregnant patients require a lower total dose of
local anesthetic to achieve an equivalent level of blockade.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1147.
What anesthetic drugs are most appropriate for
producing uterine relaxation for breech delivery or
removal of a retained placenta?
Although general anesthesia with 1.5-2.0 MAC of an inhalation
agent will produce uterine relaxation for maneuvers such as
second twin delivery, breech presentation or postpartum
removal of a retained placenta, the administration of
nitroglycerin 50-500 mcg IV has generally replaced the need for
general anesthesia to relax the uterus.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1152.
How does pregnancy affect the protein binding of
lidocaine? What effect could this have?
The protein binding of lidocaine decreases during pregnancy.
As protein binding decreases, the free fraction of the drug is
increased and the risk for toxicity increases.
Chestnut DH, Polley LS, Tsen LC, Wong, CA. Chestnut’s
Obstetric Anesthesia: Principles and Practice. 4th ed.
Philadelphia, PA: Mosby Elsevier, 2009: 30.
How does pregnancy affect the protein binding of
bupivacaine?
Although the two proteins to which bupivacaine binds, albumin
and alpha-1 acid glycoprotein, are both decreased during
pregnancy, the total amount of protein binding is unchanged. It
is believed that alpha-1 acid glycoprotein is not saturated at the
concentrations at which bupivacaine is normally administered,
leaving a ‘reserve’ of alpha-1 acid glycoprotein to which it can
bind.
Chestnut DH, Polley LS, Tsen LC, Wong, CA. Chestnut’s
Obstetric Anesthesia: Principles and Practice. 4th ed.
Philadelphia, PA: Mosby Elsevier, 2009: 30.
Does pregnancy affect the rate of absorption of
bupivacaine from the epidural space?
No. During pregnancy, the rate of absorption of bupivacaine
from the epidural space is unchanged.
Chestnut DH, Polley LS, Tsen LC, Wong, CA. Chestnut’s
Obstetric Anesthesia: Principles and Practice. 4th ed.
Philadelphia, PA: Mosby Elsevier, 2009: 30.
Is ketorolac an acceptable analgesic in a laboring
parturient?
NSAIDs such as ketorolac are generally avoided in laboring
parturients because they inhibit uterine contractions and
promote closure of the fetal ductus arteriosus.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 847.
