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Boards: Pregnancy, Neonatology > C Sections > Flashcards

C Sections Flashcards

1
Q

Anticholinergics

A

Decrease salivation, inhibit excessive vagal efferent activity from traction on uterus
o Benefits vary with species – greatest with dogs, cats
o Glyco increases gastric pH –> may decrease severity of chemical pneumonitis
o Glyco may be more appropriate, does not cross BBB/BPB

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2
Q

ACP

A

Long DOA: no indications for routine use, restrict to markedly excited animals only

ACP: significant maternal, fetal depression at low dozes

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3
Q

BDZ

A

Benzodiazepines: midaz, diazepam – induce neonatal depression immediately following birth
 Lower doses: reduce risk
 Antagonism: flumazenil

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4
Q

a2s

A

presynaptic a2A R in LC – inhibition of NE release, reduce post-synaptic membrane excitability
 Inhibits cortical arousal response = conscious sedation effect
 Neonates rousable with physiologic stimulus  cry after birth, respond to sensory input

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5
Q

Xylazine

A

rapidly crosses placenta, fetal/material depressant effects – resp, CV
 Caution or avoid in ruminants – spontaneous abortion
 +ketamine: life-threatening CP changes in dogs, decreased tissue perfusion – do not use in SA

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6
Q

Detomidine

A

appears well tolerated by pregnant mares, drug of choice in ruminants

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7
Q

Opioids

A

o Rapidly cross placenta, cause neonatal respiratory/CNS depression
o Fetal elimination may require 2–6 days
o Agonist–antagonist or partial agonist (butorphanol and buprenorphine) reportedly induce less respiratory depression
o Opioids can be antagonized

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8
Q

Thiopental

A

 Rapidly crosses placenta, rapidly cleared from neonatal circulation
* Fetal metabolism may contribute to its rapid clearance in utero
 Neonatal respiratory depression, sleepiness, decreased activity
 Suckling activity decreased, reported depressed for 4d, less with lower doses <4mg/kg

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9
Q

Propofol

A

 Rapidly crosses placenta, rapidly cleared from neonatal circulation
 Longer term CRI may result in fetal depression

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10
Q

Etomidate

A

–Fetal tissue perfusion well maintained
–Rapid initiation of neonatal spontaneous breathing, greater fetal vitality at delivery than with thiopental
–Plasma esterase metabolism
* LJ Chp 16: severe neonatal depression

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11
Q

Saffan

A

 Two progesterone‐like steroids (alfaxalone 9mg/mL; alfadolone 3mg/mL)
 Induction = smooth, rapid
 CV depression proportionate to dose, similar to TP or methohexital
 Less respiratory depression than barbiturates
 Use in dogs not recommended: solubilizing agent (cremaphore) causes severe histamine release unless pretreated with antihistamines

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12
Q

Alfaxan CD

A

 Cyclodextran carrier devoid of histamine‐releasing properties
 Short‐acting, minimal CV depression, few AEs
 Improved Apgar scores vs propofol

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13
Q

Dissociatives

A

Increased uterine contraction

Low doses may be used for induction

Retrospective study: ketamine use associated with respiratory depression, apnea, decreased vocalization, increased mortality

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14
Q

Inhalants

A

Readily cross the placenta with rapid equilibration
 Isoflurane, sevoflurane, desflurane preferred: induction, recovery more rapid

Deep levels of anesthesia: maternal hypotension, decreased UBF, fetal acidosis
o N2O can potentiate effect, <60%: fetal depression minimal, diffusion hypoxia does not occur upon delivery

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15
Q

NMBA

A

Cross placenta to a limited extent, little effect on neonates at clinical doses
o Succinylcholine: traditional choice when combined with an ultrashort‐acting barbiturate or propofol for induction

–Avoid panc, dox - DT long DOA
–Can consider mivacurium (15-20’), atra, vec

Reverse non-depolarizing, use PPV

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16
Q

Guaifenesin: horses, cattle, small ruminants:

A

transplacental transfer minimal based on vigor of newborn

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17
Q

LAs

A

Ester (procaine or tetracaine)
 Metabolized by maternal, fetal pseudocholinesterase; little accumulation

Amide
–Metabolized by hepatic microsomal enzymes
–Potentially increased metabolism of lidocaine DT increased hepatic BF
–Neonatal plasma concentrations greater then 3mcg/mL lido/mep = neonatal depression, rarely occur after epidural
* Mepivacaine: not metabolized well by fetus/neonates

Sympathetic blockade: decreases uteroplacental perfusion

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18
Q

NSAIDS

A

Exposure during the first trimester = higher rate of miscarriage in women

Exposure during second trimester = altered organogenesis of brain, kidneys, lungs, bones, GIT, CV system

Exposure in late 3rd trimester = premature closure of DA

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19
Q

C Sections in Dogs, Cats

A

Fetal death rises rapidly with prolonged stage II labor
 Fetal death with 1-4.5hr of labor = 5.4%
 Fetal death with 5-24hr of labor = 13.7%
 Are fetuses in distress?

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20
Q

Recognition of Fetal Distress in SA

A

Fetal HR slows with hypoxia
* <180bpm: fetal distress
* <160bpm: EMERGENCY

21
Q

Foals

A

Foals must be delivered within 20-30’ of chorioallantoic membrane rupture
 >40’: EMERGENCY

22
Q

Advantages of GA for C section

A

Speed, easy of induction
Reliability, control with optimum operating conditions
Route for maternal O2 administration
Intubation: protection of airway

23
Q

Disadvantages of GA for C Section

A

Greater neonatal depression
Inadequate ax plane = maternal catecholamine release
Aspiration

24
Q

When would GA be more appropriate than locoregional anesthesia for a c section?

A

 Hypovolemia
 Prolonged dystocia
 Stressed Fetus
 Maternal cardiac failure
 Morbid obesity
 Upper airway resistance (Brachycephalic)

25
What are the three parturition stages of horses?
 Stage I: positioning of fetus, several hours  Stage II: rupture of chorioallantois, 10-20’ – MUST BE <30’  Stage III: passage of placenta, <3hr
26
Horses and C Sections
o Induction of parturition not recommended DT problems with surfactant production, skeletal m maturation o Dystocia: profound effects on the survival of foals o Normally delivered within 20-30 mins after chorioallantoic membrane rupture  Few survive after 40mins, almost none at 90 mins
27
Most important feature of an equine c section?
RAPID SPEED - GET THE FOAL OUT
28
Recoveries following equine c sections
- Mares may be exhausted - prone to difficult recovery, consider H/T ropes
29
Oxygen Support
o Supplemental oxygen can increase fetal oxygen content, viability o Fetal blood has lower 2,3-DPG – more O2 content with lower O2 tension  Higher HGB saturation at lower O2 tension  Umbilical vein PO = 30mmHg
30
What is the effect of hypoventilation on uterine BF?
decreases uterine blood flow
31
What are some challenges associated with c sections in ruminants?
not fasted, predisposed to regurgitation, aspiration, bloat/ruminal tympany Normal ruminant things PLUS gravid uterus - very predisposed to VQ mismatch, hypoventilation, hypoxemia - consider performing under locoregional/standing
32
Effect of pregnancy on LA requirements?
**PREGNANCY WILL DECREASE LA DOSE REQUIRED**
33
Absolute contraindications to epidural anesthesia?
coagulopathies, septicemia, infection in area of needle insertion, uncorrected hypotension, lumbosacral pathology
34
Relative contraindications to epidural anesthesia?
bacteremia, neurologic disease aggravated by epidural drug administration
35
Changes to Epidural Space with Pregnancy
o Pregnancy associated with increased blood volume, increased shunting of abdominal blood to epidural tissues, increased epidural fat stores  **Increases volume of epidural blood vessels, fat --> decreases potential volume of epidural space**  Volume of epidural injected in pregnant animal at term **migrates more rostrally** than same volume injected in non-pregnant animal of similar size **Dose, vol of LA for epidural or spinal anesthesia reduced by ~1/3**
36
Advantages of Locoregional Techniques with C Sections
 Simplicity  Minimal exposure of fetus to drugs  Less intraoperative bleeding  Less risk of aspiration while awake  Excellent muscle relaxation/analgesia
37
Disadvantages of Locoregional Techniques with C sections
sympathetic blockade, treat with IVF or ephedrine
38
Spinal Cord Ends
Spinal cord terminates at L6 for dogs, L7/mid sacrum for cats * Terminates mid sacrum in swine, ruminants
39
Epidurals in SR, Pigs
* Epidurals well established, not difficult - L6/S1 * If not under GA/intubated: caution with extension of head, neck --> soft palate may occlude airway
40
Epidurals in Pigs
*Pigs: 10mL/100kg, 15mL for 200kg, up to 20mL in large pigs o Alternatively: one 1mL lido injected for first 40cm of distance from base of tail to occipital protuberance plus 1.5mL for each additional 10cm of back length
41
Rastabi et al VAA 2020 - duration of motor/sensory blockade with saline vs phentolamine
epidural administration of 5mL normal saline after epidural injection of lidocaine-epinephrine reduced duration of sensory but not motor block in sheep o Epidural administration of phentolamine diluted to final volume of 5mL diminished both duration of sensory, motor block in sheep administered epidural lidocaine + epinephrine
42
Elane et al JAVMA 2022 - intrathecal lidocaine for goat c sections
intrathecal lidocaine at 1mg/kg at LS space provided adequate analgesia for C sections in goats o Minimal complications, quicker return to hind limb motor function post operatively than historically reported for epidurals o Bupivacaine traditionally reported to interfere with motor for 11hr, lidocaine for 3hr – goats stood at ~3+/-1hr
43
Epidurals in Cattle
Sacrococcygeal space usually ossified in adult Coccygeal epidural will facilitate vaginal delivery, decreases Ferguson's reflux
44
Proximal Paravertebral Block
o Proximal: proximity to spine  Nerves blocked: T13, L1, L2, +/- L3  Landmarks: L1-L3, +/- L4 Blocked adjacent to verbebrate, parallel (needles pointed ventral)
45
Distal Paravertebral Block
distance from spine  Dorsal, ventral br T13, L1-L3 Needle pointing medial, toward midline
46
Inverted L/7 block
o Inject LA along caudal border of last rib, along lumbar transverse processes o +: easy to perform, out of the surgical field o -: large amount of local anesthetic required, peritoneum not blocked
47
Infiltration Block
o Inject anesthetic along surgical margins o +: easy to perform o -: large amount of local required, distorts anatomy, bleeding at surgical site, could cause fetal depression
48
When give NSAIDS during a c section?
AFTER fetus separated from placenta- reduces fetal prostaglandin concentration, premature DA closure

Boards: Pregnancy, Neonatology (5 decks)

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