Cesarean Section Anesthesia Flashcards
What factors act to speed uptake and increase the effect of inhalant anesthetics during pregnancy?
Oxygen consumption increases by 20%. Maternal desaturation occurs quickly without supplemental oxygen. Induction with inhalants occurs much faster.
Increased maternal plasma volume (“relative anemia”)
Cardiac output increases by 40% and utero-placental perfusion is pressure dependent.
Anesthetic requirement decreased by 25-40%
Why should the calculated volume of local anesthetic be decreased 30-50% when performing an epidural block for C-section?
Less volume is needed with epidural injection to reach specific dermatome
What is ion trapping?
In acidotic fetuses, weak bases tend to be in ionized form, get trapped, and cause drug accumulation
What was the leading cause of maternal mortality in a retrospective study of dogs undergoing caesarean section?
Aspiration pneumonia
What general anesthetic protocol was found to have a live pup birth rate similar to the accepted gold standard - epidural anesthesia - during c-section?
Isoflurane and propofol
What classes of drugs are associated with worsened pup survival outcome following c-section?
Dissociatives
Atropine, a tertiary amine, crosses the blood-brain barrier as well as the placenta. Will giving atropine to a pregnant animal increase fetal heart rate? What about a neonatal pup or kitten? Why or why not?
Atropine is ineffective in fetus/neonate ≤ 14 days post birth
It is ineffective because they are neurologically immature
Doxapram, an analeptic used to stimulate breathing, is often given to apneic neonates. Would doxapram be expected to have an effect in a hypoxic neonate?
Doaxapram is not effective during hypoxemia
Your sophomore surgery dog is 52 days pregnant. Your plan is to perform an en bloc ligation and resection of the uterine horns containing the fetuses along with the ovaries. Following resection, the puppies within the uterine horns have palpable heartbeats.
a. Are these in utero puppies sentient, conscious, and able to feel pain? Why or why not?
b. Your classmates decide to remove the puppies from the uterine horns to see what they look like. Are these ex utero puppies sentient, conscious, and able to feel pain? Why or why not?
a. No. Maternal hormones that cross the placenta (estrogen and progesterone) help produce neonatal unconsciousness in utero
b. Yes. By removing them from the uterus and exposing them to air, consciousness is now possible and welfare issues arise.
Is oxygen necessary during routine neonatal resuscitation? How might oxygen supplementation make things worse?
Oxygen is not routinely needed. It causes free radical formation, lung damage, and brain damage
Term bulldog bitch presented for dystocia and C-section. Live pups are suspected.
a. What is your choice of premedications? Why?
b. What is your choice of induction agent? Why?
c. What is your choice of maintenance agent?
d. What is your choice of postoperative analgesic?
a. Morphine, Fentanyl, Opioid. The best options for fetal viability
b. Propofol. It is the best for fetal viability
c. Isoflurane, could also give epidural after being induced
d. Carprofen and opioid
Term Angus cow presented for dystocia and C-section. Live calf is suspected.
a. What is your choice of premedications? Why?
b. What is your choice of induction agent? Why?
c. What is your choice of maintenance agent?
d. What is your choice of postoperative analgesic?
a. Xylazine. We can antagonize it if we have to
b. You almost never induce cattle with general anesthesia. Local anesthesia is done standing because you don’t want the animal to go down
c. Epidural will make the cow go down and we don’t want that
d. Banamine. Maybe a little butorphanol
4 mos pregnant Quarter Horse presented for sinus flap and cheek tooth removal. Live foal is suspected.
a. What is your choice of premedications? Why?
b. What is your choice of induction agent? Why?
c. What is your choice of maintenance agent?
d. What is your choice of postoperative analgesic?
You can use pretty much anything here because you are not delivering the foal. The foal is basically another organ system.
What are factors contributing to puppy mortality on the maternal side?
Dehydration Hypovolemia Sepsis Stress Exhaustion Hypocalcemia
What are factors contributing to puppy mortality on the fetal side?
Hypoxia
Acidosis
Hypercapnea
Distress
Under what conditions does puppy survival after c-section improve?
When surgery was not emergent Dam was not brachycephalic < 4 puppies in the litter No natural-delivered or deformed puppies All puppies breathed spontaneously No methoxyflurane or xylazine used
What is puppy vigor reduced by?
Use of any inhaled anesthetics
Use of ketamine
Use of thiobarbiturates
Is short anesthesia/delivery time advantageous?
There is not evidence to support this
What decreases the anesthetic requirement in pregnant dogs?
Increased progesterone modulates type A GABA receptors
Hormonal antinociception die to increased estrogen and progesterone
What does increased progesterone levels do to the GI tract?
Decreased gastric emptying
Increased gastric volume
Decreased gastroesophageal sphincter tone
What can the GI problems caused by increased progesterone levels do to the lungs?
Increase risk of pulmonary aspiration
What does the physical size of the uterus do to the GI tract? Lungs?
Displaces pylorus
Decreases lung volume
What does increased gastrin levels do to the GI tract? Lungs?
Reduces gastric pH
Increased pulmonary damage following aspiration
What are pharmacologic considerations during pregnancy?
All anesthetic drugs cross the placenta
What are anesthetic recommendations for c-section?
Drugs with short duration of action or drugs with specific antagonists available
The lowest possible dose because the parturient has substantially lower anesthetic requirements
Use local anesthetics when possible and appropriate
Monitor BP and prove IV fluid support
Provide supplemental oxygen to mother
Provide endotracheal intubation if general anesthesia is used
What premeds should be avoided?
Alpha-2 agonists
Benzodiazepines
What can maternal bradycardia be treated with?
Atropine or glycopyrrolate
What induction agents are associated with improved neonatal outcome?
Propofol and isoflurane
Alfaxalone and isoflurane
What induction agents are associated with fetal depression?
Dissociatives (ketamine, Telazol)
What is considered the gold standard for fetal viability?
Local anesthetic techniques, which has similar results with propofol/iso
What is an epidural associated with?
Maternal hypotension and fetal acidosis due to sympathetic blockade
What is used for post c-section analgesia?
NSAIDs and opioids
Describe neonatal resuscitation
Place on clean, dry towel, clear fluid from nose and mouth
Rub vigorously
O2 is not routinely needed
Atropine is ineffective < 2 weeks of age
What may stimulate the respiratory, CV, and sympathetic nervous system?
Acupuncture of governing vessel 26
What is fetal sentience in altricial species due to?
Neurological immaturity
What is fetal sentience in precocial species due to?
Consciousness occurs within minutes or hours following birth due to the decreasing neuroinhibition and strong neuroactivation asscoiated with the birth process
