Cesarean Section Anesthesia

Question 1

What factors act to speed uptake and increase the effect of inhalant anesthetics during pregnancy?

Answer 1

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%

Question 2

Why should the calculated volume of local anesthetic be decreased 30-50% when performing an epidural block for C-section?

Answer 2

Less volume is needed with epidural injection to reach specific dermatome

Question 3

What is ion trapping?

Answer 3

In acidotic fetuses, weak bases tend to be in ionized form, get trapped, and cause drug accumulation

Question 4

What was the leading cause of maternal mortality in a retrospective study of dogs undergoing caesarean section?

Answer 4

Aspiration pneumonia

Question 5

What general anesthetic protocol was found to have a live pup birth rate similar to the accepted gold standard - epidural anesthesia - during c-section?

Answer 5

Isoflurane and propofol

Question 6

What classes of drugs are associated with worsened pup survival outcome following c-section?

Answer 6

Dissociatives

Question 7

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?

Answer 7

Atropine is ineffective in fetus/neonate ≤ 14 days post birth
It is ineffective because they are neurologically immature

Question 8

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?

Answer 8

Doaxapram is not effective during hypoxemia

Question 9

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?

Answer 9

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.

Question 10

Is oxygen necessary during routine neonatal resuscitation? How might oxygen supplementation make things worse?

Answer 10

Oxygen is not routinely needed. It causes free radical formation, lung damage, and brain damage

Question 11

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?

Answer 11

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

Question 12

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?

Answer 12

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

Question 13

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?

Answer 13

You can use pretty much anything here because you are not delivering the foal. The foal is basically another organ system.

Question 14

What are factors contributing to puppy mortality on the maternal side?

Answer 14

Dehydration
Hypovolemia
Sepsis
Stress
Exhaustion
Hypocalcemia

Question 15

What are factors contributing to puppy mortality on the fetal side?

Answer 15

Hypoxia
Acidosis
Hypercapnea
Distress

Question 16

Under what conditions does puppy survival after c-section improve?

Answer 16

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

Question 17

What is puppy vigor reduced by?

Answer 17

Use of any inhaled anesthetics
Use of ketamine
Use of thiobarbiturates

Question 18

Is short anesthesia/delivery time advantageous?

Answer 18

There is not evidence to support this

Question 19

What decreases the anesthetic requirement in pregnant dogs?

Answer 19

Increased progesterone modulates type A GABA receptors

Hormonal antinociception die to increased estrogen and progesterone

Question 20

What does increased progesterone levels do to the GI tract?

Answer 20

Decreased gastric emptying
Increased gastric volume
Decreased gastroesophageal sphincter tone

Question 21

What can the GI problems caused by increased progesterone levels do to the lungs?

Answer 21

Increase risk of pulmonary aspiration

Question 22

What does the physical size of the uterus do to the GI tract? Lungs?

Answer 22

Displaces pylorus

Decreases lung volume

Question 23

What does increased gastrin levels do to the GI tract? Lungs?

Answer 23

Reduces gastric pH

Increased pulmonary damage following aspiration

Question 24

What are pharmacologic considerations during pregnancy?

Answer 24

All anesthetic drugs cross the placenta

Question 25

What are anesthetic recommendations for c-section?

Answer 25

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

Question 26

What premeds should be avoided?

Answer 26

Alpha-2 agonists

Benzodiazepines

Question 27

What can maternal bradycardia be treated with?

Answer 27

Atropine or glycopyrrolate

Question 28

What induction agents are associated with improved neonatal outcome?

Answer 28

Propofol and isoflurane

Alfaxalone and isoflurane

Question 29

What induction agents are associated with fetal depression?

Answer 29

Dissociatives (ketamine, Telazol)

Question 30

What is considered the gold standard for fetal viability?

Answer 30

Local anesthetic techniques, which has similar results with propofol/iso

Question 31

What is an epidural associated with?

Answer 31

Maternal hypotension and fetal acidosis due to sympathetic blockade

Question 32

What is used for post c-section analgesia?

Answer 32

NSAIDs and opioids

Question 33

Describe neonatal resuscitation

Answer 33

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

Question 34

What may stimulate the respiratory, CV, and sympathetic nervous system?

Answer 34

Acupuncture of governing vessel 26

Question 35

What is fetal sentience in altricial species due to?

Answer 35

Neurological immaturity

Question 36

What is fetal sentience in precocial species due to?

Answer 36

Consciousness occurs within minutes or hours following birth due to the decreasing neuroinhibition and strong neuroactivation asscoiated with the birth process