OB Flashcards
Most likely cause for rapid arterial O2 desaturation during the intubation of a pregnant patient
decreased FRC
FRC = RV + ERV
OB upper airway
- increased risk for difficult mask, difficult laryngoscopy, difficult intubation (failed intubation 8x higher)
- hormones cause vascular engorgement & upper airway swelling
- increased MP score
- narrow glottic opening = 6.0-7.0 ETT
- short handle laryngoscope (Datta handle)
- tissue friable- avoid nasal airway
- edema worse w/ preeclampsia, tocolytics, Tburg
Lung physiology
- relaxin relaxes ribcage, more horizontal
- uterus pushes diaphragm cephalad
- FRC decreases (ERV + RV)
ABG
- progesterone = resp stimulant
- resp alkalosis
- pH normal
- PaCO2 decreases
- HCO3 decreases (to normalize pH)
OxyHgb curve shifts
- right
- facilitates O2 transfer to fetus
Ve, Vt, & RR
all increased d/t increased O2 consumption & CO2 production
Lung volumes
- Decrease = TLC, FRC, ERV, RV
- No change = VC, CC
O2 consumption
- Term = 20 % increase
- 1st stage labor = 45 % increase
- 2nd stable labor = 75% increase
CO
- increases 40%
- during labor:
- 1st stage = 20% increase
- 2nd stage = 50% increase
- 3rd stage = 80% increase
- returns to pre-labor in 24-48 hours
- HR = 15% increase
- SV = 30% increase
BP
- no change MAP or SBP
- DBP decreases
Vascular resistance
- SVR & PVR decrease
CVP & PAOP
no change
cardiac axis deviation
- left deviation
- uterus pushes diaphragm cephalad which pushes heart up & left
aortocaval compression
- “supine hypotension”
- uterus compresses aorta & vena cava
- decreased venous return
- place mother in LUD (2nd/3rd trimester)
IV volume
- increases 35%
- plasma volume increases 45%
- erythrocyte volume increases 20%
dilutional anemia
hematologic changes
- clotting factors 1, 7, 8, 9, 10, 12 = increase
- anticoagulants
- antithrombin = decrease
- protein S = decrease
- fibrin breakdown = increase
- antifibrinolytic = decrease (11 & 13)
- PT/PTT= decrease
- PLT count same or decreases
MAC
30-40% decrease
sensitivity to LA
increase
gastric volume & gastric pH
- gastric volume increases
- gastric pH decreases
LES sphincter tone
decreases
Renal
- increase = GFR, CrCl, glucose in urine
- decrease = creatinine & BUN (d/t inc CrCl)
Uterine blood flow
- increases up to 700-900 ml/min
- 10% of CO
- not autoregulated
UBF = (Uterine a. pressure - Uterine v. pressure) / uterine vascular resistance
Most important variables that increase drugs across placenta
- diffusion coefficient (drug characteristics)
- concentration gradient b/t mom & fetus
Drug characteristics that favor placental tranfer
- LMW < 500 daltons
- lipid soluble
- non-ionized
- non-polar
Drugs that cross placenta
- LA (except chloroprocaine
- IV anesthetics
- VA
- opioids
- benzos
- atropine
- BB
- Mg+
Drugs that do NOT cross placenta
H - Heparin
I - Insulin
G (h)- Glycopyrrolate
Noon- NMBs
Stage 1 of labor
- regular contractions to full dilation (10 cm)
- latent = 2-3 cm
- active = 3-10 cm
- dull/diffuse/cramping pain in lower uterine segment & cervix (T10-L1)
- neuraxial
Stage 2 of labor
- full dilation to delivery of fetus
- sharp/localized perineal pain begins (T10-L2 + S2-S4)
- neuraxial
- pudendal n. block
Stage 3 of labor
- delivery of placenta
NPO guidelines
laboring mothers may drink a moderate amount of clear liquids through labor & eat solid food up to the point a neuraxial block is placed
Timing of epidural placement
ACOG recommend timing of epidural placement should be individualized and patient should not have to wait until she achieves certain dilation
Consequences of uncontrolled pain
- increase catecholamines = HTN, decrease UBF
- hyperventilation = left OxyHgb shift = decrease O2 to fetus
early decelerations
VEAL CHOP
- Early = Head compression
- occur w/ contraction
late decelerations
VEAL CHOP
-Late = placental insufficiency
- FH falls after peak of contraction
- occur w/ each contraction
- Causes = hypotension, hypovolemia, acidosis, preeclampsia
variable decelerations
VEAL CHOP
- Variable = Cord compression
- no pattern b/t FHR & uterine contraction
Prematurity
- < 37 weeks gestation
- tocolytics to suppress contractions
- betamethasone to hasten fetal lung maturity
B2 agonists
- ritodrine, terbutaline
- relax uterus
- SE: hyperglycemia, hypokalemia
Mg+ sulfate
- Ca+ antagonist
- relaxes uterus
- hyperpolarizes membranes in excitable tissue (SZ prophylaxis for preeclampsia)
Mg+ toxicity
- 1st sign = loss of deep tendon reflexes
- diminish at 5-7 , loss of reflexes at 7-12 mg/dL
- other side effects: skeletal muscle weakness (potentiates NMBs), pulmonary edema, reduced response to ephedrine & neo
- Tx: diuretics, IV calcium gluconate 1 gram
Oxytocin
- uterotonic
- administered after delivery of placenta
- SE: water retention, hyponatremia, hypotension, reflex tachycardia, coronary vasoconstriction
- CV collapse if given too quickly
Methergine (Ergot Alkaloid)
- uterotonic
- 0.2 mg IM
- IV admin cause cause HTN & cerebral hemorrhage
Prostaglandin F2 (hemabate, carboprost)
- uterotonic
- 250 mcg IM
- SE: N/V, diarrhea, hypotension, HTN, bronchospasm
Which trimester is best for non-OB surgery?
2nd trimester
When is RSI indicated in the pregnant patient?
- 18-20 weeks
- immediate postpartum period
Safe drugs for non-OB surgery
- opioids
- VA
- NMBs
- thiopental
Why are NSAIDs avoided after the 1st trimester?
potentially close ductus arteriosus
Chronic HTN
- before 20 weeks gestation
- does not return to normal after delivery
Gestational HTN
- occurs after 20 weeks gestation
Preeclampsia
- mild = BP > 140/90
- severe = BP > 160/110
- develops after 20 weeks gestation
- proteinuria usually present
- Also RUQ/epigastric pain HA, FGR, thrombocytopenia, elevated serum liver enzymea
Preeclampsia patho
- abnormal placental implantation creates an environment characterized by elevated vascular resistance & reduction in placental blood flow.
- 7:1 thromboxane : prostacyclin ratio
- thromboxane = vasoconstriction, PLT aggregation
Preeclampsia treatment
- definitive treatment = delivery
- treat BP > 160/110
- labetalol, hydralazine, nifedipine, nicardipine
Eclampsia
preeclamptic patient develops seizures
SZ prophylaxis magnesium
- loading dose = 4 grams over 10 min
- then 1-2 g/hr
HELLP Syndrome
H -Hemolysis
EL- Eelvated Liver enzymes
L- Low
P- Platetes
- 5-10% of preeclamptic patients
- RUQ/epigastric pain
- assess for thrombocytopenia before placing a block
- Tx: delivery
Maternal cocaine abuse
- cocaine = ester LA
- inhibits NE reuptake in presynaptic SNS neuron
- CV = tachycardia, dysrhythmias, coronary vasoconstriction, MI
- CNS = CVA, SZ, ischemia
- Acute intoxication = increased MAC
- Chronic use = decreased MAC
- OB risks = spont abortion, premature labor, placental abruption, low APGAR, thrombocytopenia
- Tx: labetalol, tx hypotension w/ phenylephrine (may not response to ephedrine d/t catecholamine depletion)
Placenta accreta
attaches to surface of myometrium
Placenta increta
invades myometrium
Placenta percreta
extends beyond uterus
Placenta accreta/increta/percreta
- potential for large blood loss
- GA preferred
- associated w/ placenta previa & previous c/s
Placenta previa
- placenta attaches to lower uterine segment & partially/completely covers cervical os
- **PAINLESS vaginal bleeding
- risk factors: hx c/s, multiple births
Placental abruption
- partial or complete separation of placenta from uterine wall
- risk factors: PIH, preeclampsia, HTN, cocaine use, smoking, excessive alcohol use
- **PAINFUL vaginal bleeding
- risk of AFE & DIC
- blood products ready, prep c/s
Most common cause of postpartum hemorrhage
uterine atony
DIC is associated with:
- AFE
- placental abruption
- intrauterine fetal demise
normal APGAR
8-10
moderate distress APGAR
4-7
impending demise APGAR
0-3
APGAR HR
0 = absent
1 = < 100
2 = > 100
APGAR RR
0 = absent
1 = slow, irregular respirations
2 = normal, crying
Muscle tone APGAR
0 = limp
1= some flexion of extremities
2 = active motion
Reflex irritability APGAR
0 = absent
1 = grimace
2 = cough, sneeze, cry
APGAR color
0 = pale, blue
1 = body pink, extremities blue
2 = completely pink
neonatal resuscitation
