Anesthetic Considerations of the Obstetric Patient Flashcards
How much does heart rate increase by term
20-30%
when does HR peak during pregnancy
32 weeks
how much does CO increase (%)
40%
how much of the CO perfuses the uterus (%)
10%
when does max CO occur and by how much (%)
increases by 80% immediately after delivery
when does CO return to baseline after delivery
14 days
what happens to ventricular walls and EDV during pregnancy
increases
which kind of murmur is not uncommon during pregnancy
systolic murmurs
what are two pathologic results of pregnancy
diastolic murmurs and cardiac enlargement
explain why dilutional anemia occurs during pregnancy
increase in plasma volume > RBC volume
H/H is lower
what is the normal blood loss expected during vaginal delivery
500mL
what is the normal expected blood loss during a c section
800-1000mL
what happens as a result of decreased SVR during pregnancy
venous pooling and decrease in DBP (but VS mostly stay at baseline)
why does supine hypotension occur for parturients
aortocaval compression/compression of aorta and vena cava by gravid uterus. normal perfusion to upper extremities but bad perfusion to lower extremities below compression.
what situations would create more severe aortocaval compression (2)
polyhydraminos and multiple gestation
how long does HoTN and aortocaval compression develop for the parturient (2)
HoTN can occur immediately, but compression takes about ten minutes for sx to develop otherwise
how to relieve aortocaval compression
left uterine displacement (LUD). more than 15 degrees
what factors of the parturient contribute to hypercoagulability
clotting factors VII-IX increased, fibrinogen increased
what is one of the leading causes of maternal mortality
thromboembolic events
what to expect with the parturient and platelet count
slight decrease. >100,000 means spinal and epidural ok per book answer
what to expect with parturient and WBC count
it will rise by term
capillary engorgement during labor results in what implications for the airway
narrowed glottic opening
oral and nasal pharynx edema
laryngeal edema
do you nasally intubate the parturient
avoid nasal intubation
what size tube would you consider for a laboring woman
smaller tube like a 6.0 or 6.5 You aren’t going for long term intubation but securing the airway quick is the most important
how much % increase in oxygen consumption during rest and how much % increase in oxygen consumption during labor do you expect
33%
100%
oxyHGB dissociation curve shifts to the
right as a parturient
when minute ventilation increases in the parturient, what would you expect of Vt and RR
Vt increases more than RR
what would you expect of PaCO2/ABG/HCO3
PaCO2 decreases slightly
ABG compensated
decreases in HCO3
what does the upward pressure of the diaphragm do for the FRC and overall parturient related reserve
decrease in FRC and rapid desaturation of apnea patient (worse than obese patient. consider ramping)
during pregnancy, there is an increased sensitivity to these two anesthetics
gases, local anesthetics
why is there an increased block height during pregnancy and neuraxial anesthesia
engorged epidural veins, increased intra abdominal pressure, decrease in epidural and subarachnoid spaces
why is there an increased risk for regurgitation and aspiration for the parturient? (3)
increased levels of gastrin
upward displacement and mechanical obstruction
labor further reduces gastric emptying
prior to c section, give these three medications to decrease risk of aspiration
non particulate acid (Bicitra)
H2 receptor blocker (Pepcid. push over 5-10m)
Prokinetic (Reglan)
what happens to albumin and what is the theoretical pharmacological result of this during pregnancy
decrease in serum albumin and increase in free fraction of highly protein bound drugs
what happens to GFR and subsequently BUN/creatinine during pregnancy
increased GFR and subsequently decreased BUN/creatinine
what can be expected to be excreted in the parturients urine and why (2)
glucose and protein. related to high GFR and reduced renal absorption
at term, uterine blood flow increases to a maximum of _____ml/min
800mL/min
how does the fetus send oxygen poor blood to the placenta?
via two umbilical arteries and perfusion of capillary networks of the placental villi
what does the placental villi do
exchanges nutrients, respiratory gases, and waste. oxygen and CO2 are perfusion limited.
fetal transfer of nutrients, respiratory gases, and waste dependent on _________, not ________
perfusion, not gases rate of diffusion
most drugs transfer to placenta via
diffusion
what is the placental diffusion dependent upon (5)
concentration gradient molecular weight lipid solubility state ionization protein binding
weight (in daltons) and cross-ability (easy versus poor)
<500 daltons crosses easily
>1000 daltons crosses poorly
if the drug has increased protein binding, what does that mean for placental crossover
decreased placental crossover
do most drugs administered to parturient cross easily
yes
fetal effects of drugs transferred into placenta have minimized effects via
dilution of intervillous blood
redistributed once in the fetus
umbilical blood passes through liver (first pass)
increase in maternal hepatic enzymes decreases serum drug levels
how does one fifth of the fetal cardiac output return to the placenta
shunt flow from foramen ovale and ductus arteriosus
acid base status may affect drug accumulation via
ion trapping
explain stage 1 of labor
effacement and dilation of the cervix. there is a latent and active stage
describe the latent stage of stage 1 labor
onset of labor to point of rapid cervix dilation irregular contractions
describe the active stage of stage 1 labor
cervix dilation 2cm to full dilation (10cm) (regular rapid contractions)
explain stage 2 of labor
cervix 10cm dilation fo delivery of the fetus (active pushing)
explain stage 3 of labor
delivery of the placenta
describe where the pain would be expected during stage 1 labor
non localized aching or cramping. T10-12-L1. initial pain is in lower thoracic and upper lumbar nerves
describe where the pain would be expected during stage 2 labor
cervical dilation complete and presenting part descends into the pelvis. S2-S4
pressure in perineal area
thicker fibers and therefore harder to block. roots are larger and harder to get to here
describe what stages the labor epidural is good for
great for stage 1 and maybe not so much for stage 2
what coverage would you need for c section
T6
what pharmacologic agent works great for this second stage labor
dexmedetomidine. the downfall is this prolongs relaxation
four factors are critical to a woman’s childbirth experience
personal expectations
amount of support from caregivers
quality of parent caregiver relationship
patients involvement in decision making
what is the most readily available method to determine fetal condition
FHR monitor
describe the two types of FHR monitors
external (doppler on maternal abdomen)
internal (electrode on fetal scalp, have to break amniotic sac)
normal FHR
110-160
when is deceleration in relation to contraction ok and what may it mean
decelerations prior to contraction OK and therefore HR110-160 variability ok
may mean head compression (coming through vagina)
describe FHR in relation to uterine contractions during uteroplacental insufficiency
decelerations after contractions mean BF is compromised to baby.
ex) mom mat be Hotensive and need fluid bolus
describe FHR in relation to uterine contractions with umbilical cord compressions
will present as variable decelerations (decelerations are not lined up with contractions- occur randomly)
amniotic sac rupture for internal FHR monitoring- can inject some fluid.
fetal accelerations indicate (2)
fetal movement and adequate oxygenation
changes in heart rate indicates
fetal oxygen reserve. hypoxia (CNS depression) decreases it via interaction in ANS
describe early deceleration considerations
occur in concert with uterine contractions
consistent with each
decrease in FHR approx 20BPM expected
describe variable deceleration considerations
related to baby
ex) fetal movement, lack of fluid
abrupt decrease in FHR irrespective of contractions
baroreflex mediated response to umbilical cord compression
describe late deceleration considerations
r/t mom
lowest point o deceleration occurs after peak contraction
represent uteroplacental insufficiency (not sufficient O2 to baby)
ex) mom HoTN, preexisting condition, NC O2, fluid bolus, last result is pressors
categories for FHR evaluation: category 1
best. normal baseline HR and moderate variability with no variable decels
categories for FHR evaluation: category 2
all tracings no included in I or III
do not indicate acid base imbalance
warrant continued observations
categories for FHR evaluation: category 3
worst
fetal bradycardia and absent variability with variable or late decels
warrants prompt intervention
what is the best technique of pain management during the birthing process
the one that allows a woman to cope with pain
in addition to reducing pain and anxiety, a good analgesic does what (2 things)
limit increases in maternal CO, HTN, and catecholamine release
reduce maternal hyperventilation, which can cause reduced fetal oxygen tension
non pharmacological techniques for labor analgesia
TENS, sterile water blocks
concerns over fetal depression limits the use of systemic medications to
early labor or when regional anesthesia is not available or contraindicated
some systemic medications that should be avoided during labor include
meperidine morphine butorphanol and nalbuphine remifentanil ketamine
the epidural labor analgesic is associated with these three things
may prolong second stage labor
can affect the incidence of forceps delivery
is not associated with increased rates of cesarean section
an indwelling catheter placed during the epidural affords these two things
the ability to produce segmental blockade
the ability to provide additional dosing
what is the goal dermatome level when dosing an epidural
T10-L1 (labor)
how is analgesia most popularly maintained with an epidural in place
intermittent bolus’
describe two methods of CSE
spinal placed first, epidural placed one level above OR
needle through needle technique. (spinal placed through epidural needle)
the spinal technique is reserved for (3)
multiparous patients in advanced second stage
those with poor pain control, to facilitate spinal placement
mother laboring without analgesia requiring an instrumented delivery
under which circumstances would a continuous spinal be placed using a macro bore epidural catheter (3)
morbid obesity
history of previous spinal surgery
inadvertent dural puncture
dosing of continuous spinal
.5-1mL of .25% isobaric bupivicaine
opioids have a ceiling effect. side effects include (4)
respiratory depression
itching (most common)
urinary retention
n/v
if you have a c section patient and want immediate analgesia, which neuraxial opioid is recommended
fentanyl
common indications for c section include (6)
cephalopelvic disproportion non reassuring fetal status (FHR <100, late decels) arrest of dialtion malpresentation prematurity (<36w) previous c section or uterine surgery
VBAC
vaginal birth after ceserean
choice of anesthesia for c section depends on (4)
maternal status
urgency of surgery
fetal condition
patients desires
before neuraxial anesthesia for parturient, what should the patient receive preoperatively (4)
aspiration prophylaxis
antibiotic administration
standard monitoring
nasal oxygen
what dermatome level is required to provide adequate neuraxial anesthesia for a c section
T4-T6
what is the most common neuraxial technique for a c section and why
single shot spinal.
simple to perform, rapid onset, reliable, less toxic
dosage of spinal for c section is
.75% hyperbaric bupivicaine is LA of choice
fentanyl and duramorph for analgesia
when a labor epidural is used to provide surgical anesthesia, what kind of dose would be considered a surgical dose
2% lidocaine with 1:200,000 epinephrine. consider sodium bicarbonate or duramorph
10-15mL required to achieve T4-T6 level
if an in situ (dwelling) epidural catheter is not reliable, these 4 things can ensue
early recognition (chance of surgical anesthesia)
replace (CSE)
single shot spinal
GA
CSE advantages (2) and disadvantages (2)
lower dose spinal can be used, ability to augment with epidural catheter
potential lower block height, can delay the start of surgery
indications for GA include
neuraxial not in place, urgent delivery required
patient refusal of neuraxial
coagulopathy
induction during GA for the parturient sequence of events
should not begin until patient is prepped and draped
sufficient de nitrogenation and pre oxygenation
RSI with cricoid pressure (prop v etomidate v ketamine and succ v roc)
GA maintenance practices for c section include
N2O and O2, avoid hyperventilation, try for a mac less than 1
TAP blocks for the c section patient
can be placed postop in patients who have not received neuraxial anesthesia or intrathecal morphine
targets sensory nerves T5-11
does not provide visceral pain relief, so no uterine coverage
posterior tap block is best
