Dystocia - Anesthesia Flashcards
how does pregnancy affect the respiratory system
- increased minute ventilation
- pressure on the diaphragm
- increased O2 demand
how does pregnancy affect the CV system
- increased plasma volume
- increased HR and SV
how does pregnancy affect the GI system
- decreased GIT motility
- increased gastrin levels
how does pregnancy affect the nervous system
- increased progesterone + endorphins
- engorgement of blood vessels in epidural space
respiratory considerations for anesthesia during pregnancy
increased inhalant uptake leading to anesthetic overdose
v/q mismatch leading to hypoventilation and hypoxemia
increased O2 demand leading to hypoxemia
CV considerations for anesthesia during pregnancy
dilutional anemia leading to reduced CO reserve
aortocaval syndrome leading to reduced preload and CO
GI considerations for anesthesia during pregnancy
increased GI transit time leading to increased risk of vomiting, regurge and aspiration
increased gastrin leading to reduced gastric pH –> predisposes to chemical pneumonitis
nervous system considerations for anesthesia during pregnancy
increased progesterone and endorphins causes decreased MAC leading to anesthetic overdose
engorged epidural vessels causes increased cranial spread of epidural drugs
what are the main anesthetic changes that need to be made in pregnant animals
- titrate anesthetic drugs and inhalants; monitor depth closely
- preoxygenate +/- IPPV
- maintain perfusion
- monitor HR and BP
- use prokinetics, PPIs
- rapid induction
- proper ET tube inflation
- have suction available
- decrease epidural volume by 1/3 to 1/4
what considerations need to be made about a fetus under anesthesia
drugs that cross the BBB also cross the placental barrier
- anesthetizing the mother causes fetal anesthesia
- large drug doses to the mother increases the concentration gradient –> pushes drug to fetus
ion trapping - basic drugs will get ion trapped in the acidic environment of the fetus
what premedications should be used in a pregnant animal
opioids ONLY
provides sedation and analgesia with minimal CV depression
why should ace, benzos, a2 agonists be avoided in pregnant animals
ace: profound depression; long duration without reversal
benzos: neurologic reflex depression in neonates
a2 agonists: profound CV depression reducing fetal blood flow
what induction drugs should be used in pregnant animals
propofol
alfaxalone
etomidate
NO benzodiazepines
why should ketamine not be used in pregnant animals
profound neonatal depression
associated with poor spontaneous ventilation at birth and poor neuro reflexes
what maintenance should be used in pregnant animals
inhalants at LOW concentration
(iso > sevo)
want to minimize amount of anesthetic used
loco-regional blocks for pregnant animals
lumbosacral epidurals at 1/3 to 1/4 the normal epidural drug volume
can combine with morphine for prolonged duration of analgesia
considerations for non-obstetric procedures in pregnant animals
- postpone any elective procedures until after weaning
- minimize stress
- minimize changes in maternal physiology to reduce fetal stress
- use short duration or reversible drugs
AVOID procedures in the first trimester due to time of fetal organogenesis (risk of teratogenic effects)
considerations for elective C sections
mother is relatively STABLE - normal monitoring of CV/resp systems and for aspiration
- use antiemetics/antacids
- check hydration, BG, acid-base, electrolytes, PCV, TP, azostix
- minimize time from induction to delivery
options for anesthesia in elective C sections
locoregional anesthesia vs general anesthesia
locoregional: sedation + epidural ONLY
- opioids +/- anticholingergics
GA: opioids, propofol, iso, epidural
considerations for emergent C sections
CV and respiratory systems are under high stress
may not require premedication if depressed/exhausted
what should always be done prior to emergent c sections
preoperative ultrasound check to determine fetal vitality
if fetuses are not viable - do not need to consider drug use
systemic analgesia for C section
morphine + meloxicam
low lipophilicity - minimal secretion in milk
