Obstetric Pt Flashcards
explain dilutional anemia w pregnancy 3rd semester normal hgb 11-12g/dL
blood volume increases ~40% plasma volume increases ~50% RBC volume only increases ~20% progesterone and estrogen activate RAAS, which causes water retention.
pregnancy increases which factors?
VII, VIII, IX, and fibrinogen (I). fibrinolysis activity decreases. platelets stay the same. end result is a hypercoagulable pt.
WBC in 3rd trimester
can get up to 30,000mm during labor
airway changes
glottic lumen narrows due to swelling edema makes tissues more prone to bleeding use smaller tube 6.0 ETT use shorter handle to not hit breast tissue
O2 consumption
33% higher just before labor. 100% higher w labor
GI: progesterone causes..
-GI smooth muscle relaxation - delayed gastric emptying -increased risk of gallbladder disease (progesterone inhibits SM, so can’t clear from the gallbladder leading to biliary stasis)
renal
-increased CO leads to increase in GFR and CC -BUN lowers to 8mg/dL -creat lowers to 0.5mg/dL -glucose in urine bc absorption can’t keep up w flow -trace protein in urine for same reason -uterus can compress the ureter and cause urinary obstruction
uterine blood flow at term
800mL/min (10% CO) most ends up in intervillous space
molecular weight to cross
>1000 daltons cross poorly. most anesthetic drugs are <500Da and cross readily.
stages of labor stage 1
cervical dilation in response to REGULAR uterine contractions effacement occurs (softening, shortening, and thinning of cervix)
stages of labor stage 2
full cervical dilation to delivery of fetus
stages of labor stage 3
includes delivery of the the placenta
3 Ps of successful vaginal delivery
powers-uterine contractions
passenger-fetal positioning to get into position
passage-bony pelvis shape, relaxation and soft tissue relaxation
parenteral opioid effects
spinal and supraspinal effects
neuraxial opioid effects
bind in substantia geltinosa (Rexed lamina II) in dorsal horn of spinal cord
normal magnesium level
1.7-2.4
Therapeutic Magnesium level
5-9
Mag level when patellar reflexes are lost
12
mag level when respiratory arrest
15-20
mag level when cardiac arrest
>25
Mag MOA
*competitive antagonist of calcium. Also decreases release of Ach at NMJ and sensitivity of motor endplate to Ach
unwanted fetal effects from indomethacin (3)
premature closure of ductus arteriosus, pulm htn, low amniotic fluid levels
MAC level when uterine atony becomes a concern
MAC >0.5
G T P A L
G-Gravidity T-term births P-preterm births A-abortion (spontaneous/elective) L-living children
distance from skin to epidural space in a thin pt
3cm if thin
distance from skin to epidural space in an adult
4-6cm in adult
distance from skin to epidural space in an obese pt
up to 8 cm
duration of a spinal
<2hours why they are rarely used for labor
levels that epidurals are inserted
L2-3 or L3-4
epidural analgesia dosing
8-12mL/hour up to 15mL/hour
volume for epidural boluses
6-10mL
spinal dose (volume)
1.6mL+/- opioid
neuraxial opioids act where
on the substantia geltinosa in the dorsal horn of the spinal cord (Mu receptors)
uncomplicated C-section blood loss
500-1000mL EBL amniotic fluid is usually 700 counted in the EBL
Why can’t chronic HTN be managed w ACE inhibitors?
they cause renal damage in pregnancy and congenital abnormalities in the fetus.
what is a molar pregnancy
absence of a fetus w placental formation (can still cause preeclampsia)
HELLP syndrome
Hemolysis, Elevated LFTs, Low Platelets, other S/S:epigastric pain, jaundice, N/V. Hepatic rupture is rare and indicates immediate delivery needed
eclampsia
when seizures are present
platelet cut off for neuraxial for preeclamptic pts
80,000
what is the defn. of antepartum hemorrhage?
vaginal bleeding after 24 weeks gestation and into immediate postpartum period
how much bleeding occurs in postpartum hemorrhage?
>500mL vaginal delivery or >1000mL cesarian
what is 80% of post-partum hemorrhage from?
uterine atony
what are atony risks?
multiparity, prolonged oxytocin infusions, polyhydramnios
placenta previa s/s
PAINLESS vaginal bleeding significant blood loss
What is Vasa Previa?
fetal vessels implanted on cervical OS fetal mortality 70% rupture of vessels is emergency rare
placenta accreta
abnormal growth of the placenta ONTO the myometrium most common
placenta increta
abnormal growth of the placenta INTO the myometrium
placenta percreta
abnormal growth of the placenta into other non-uterine structures
LBW
<2500g (5lb, 8 oz)
VLBW
<1500g (3lb, 4oz)
ELBW extremely LBW
<1000g (2lb, 3 oz)
What is a normal fetal heart rate?
110-160 BPM
FHR variability
best indicator of fetal wellbeing nervous system responses to adjust the HR up or down represents a functional nervous system
moderate variabiliity on fetal HR monitoring
5-25bpm
increase/decrease HR CO SV SVR MAP (SBP, DBP)
HR = increase
CO = increase
SV = increase
SVR = decrease
MAP = decrease
SBP = decrease a little
DBP = decrease more
Postpartum CO
-increases because great vessels in abdomen are no longer compressed allowing for increased venous return
Why does CO change?
-increase in HR + SV (larger effect)
increase of decrease of RASS activation?
increase
EKG changes
-left axis deviation (3rd trimester), right axis deviation (1st trimester) -shortened PR and QTc
aortocaval compression
-supine position starting at 20 weeks -treatment is left uterine displacement
increase/decrease Minute Ventilation FRC ERV RV CC dead space
Minute Ventilation = increase due to tidal volume FRC = decrease ERV = decrease RV = decrease CC = same dead space = increase
respiratory blood gas
compensated metabolic alkalosis
nervous system changes
-increased SNS -increased sensitivity to LA and GA
liver
-enzymes increase -albumin level decrease -cholinesterase activity decreases
spiral arteries
-terminal arteries that spill into the intervillous space
do maternal and fetal blood interact (touch)?
-no
differences in fetal circulation
-foramen ovale -ductus arteriosus -ductus venosus (shunt in liver) -umbilical artery(2)/vein
factors affecting placental drug transfer to fetus
-concentration gradient -molecular weight (<1000 Daltons) -lipid solubility -ionization
fetal circulation factors affecting placental drug transfer to fetus
-diluted in intervillous blood -redistributed -fetal first-pass effect -fetal shunt
drugs that don’t cross the placenta
-glycopyrrolate -anticoagulants -muscle relaxants -sugammadex -insulin
progesterone
promotes smooth muscle relaxation
oxytocin
-promotes smooth muscle contraction -prostaglandin production
labor stage 1 - pain
-due to cervical distention, stretching lower uterine segment, myometrial ischemia -T10-L1 -unmyelinated C-fibers -poorly localized visceral pain
labor stage 2 - pain
-due to stretching/distension of pelvic floor, vagina, perineum -pudendal nerves, S2-S4 -myelinated
pregnancy pharmacology risk categories
A: controlled studies demonstrate no risk B: controlled animal studies demonstrate no risk C: studies have revealed adverse effects on fetus D: fetal risk but benefit outweighs risk X: known fetal abnormalities
MAC for pregnant women
-reduced up to 40%
first line treatment for hypotension
phenylephrine
most common sign of hypotension in spinal anesthesia
maternal nausea/vomiting
Uterotonics
-methergine: avoid in HTN, preeclampsia, PVD, ischemic heart disease -prostaglandin E3: avoid in asthma, glaucoma, renal/pulmonary/hepatic disease -prostaglandin E1: given for uterine atony, side effects - malaise -prostaglandin F2a: side effects bronchospasm, increase PVR, PHTN -oxytocin: increases strength + frequency of contractions, side effects - hypotension from preservative, water intoxication
Tocolytics
-calcium channel blockers -magnesium sulfate - competitive antagonist of calcium, increases sensitivity to NMB -nitroglycerin
local anesthetics: amines vs ester
amines: two i’s in name, metabolized by liver ester: one i in name, metabolized by cholinesterase
local anesthetics: bupivacaine
-long, sensory>motor -0.0625%-0.125% -black box = 0.75% -preferentially bind to cardiac receptors leading to refractory cardiac arrest
local anesthetics: ropivacaine
-long, sensory>motor -less cardiotoxic than bupivacaine -0.1%-0.2%
local anesthetics: lidocaine
-transient neurological symptoms -subarachnoid space administration potentially neurotoxic -metabolites that can cause seizures
local anesthetics: 2-chloroprocaine
-rapid onset, short duration (epidural use) -reduces effectiveness of opioids
neural axial opioids: respiratory monitoring
-lipophilic = 2 hours -hydrophilic = 12 hours
neural axial opioids: side effects
-less complete analgesia -perineal tone maintained -pruritus -nausea/vomiting -sedation -respiratory depression
neural axial opioids: morphine
-less lipophilic -may cause HSV reactivation
neural axial opioids: dosing
-epidural bolus = similar to IV dose -intrathecal = 1/10 of epidural dose
local anesthetic test doses
-use to confirm non-vascular, non-sub arachnoid placement -aspiration -3 mL test dose between contractions (1.5% lidocaine, 1:200,000 epinephrine)
neuroaxial complications: most common drugs
bupivacaine > ropivacaine > levobupivacaine > lidocaine > 2-chloroprocaine
neuroaxial complications: treatment
-stop drug, administer O2, support ventilation -20% lipid therapy 1.5 mL/kg over 1 minute than 0.25-0.5 mL/kg/min infusion -anticonvulsants (not cardiac depressing) -avoid vasopressin, BB, CCB, LA
post dural puncture headache: risks
-large bore needle -younger age -bevel orientation -beveled cutting needles -inexperienced operator -air for loss of resistance syringe
post dural puncture headache: treatment
-bed rest -caffeine -oral analgesia -epidural saline -epidural blood patch -sphenopalatine ganglion block
optimal timeframe between induction and delivery of fetus
-3 minutes -patient draped and surgeon ready before induction
MAC level necessary to avoid anesthesia awareness
0.8
c-section: necessary epidural level
T4
c-section: epidural volume
1-2 mL per dermatome level
c-section: blood loss
-500-1000 mL -amniotic fluid is counted in blood loss (300-1500 mL)
pre-eclampsia criteria
-HTN -proteinuria -non-dependent edema (+/-) *must be greater than 20 weeks pregnant
pre-eclampsia treatment
-definitive=delivery -corticosteroids (infant lungs) -magnesium sulfate -labetalol, esmolol
pre-eclampsia anesthesia considerations
-prefer neuraxial -laryngoscopy risk -avoid opioids before delivery -usually remain hypertensive throughout
what is polyhydramnios?
too much amniotic fluid
fetal hgb
maternal hbg
fetal 15
maternal 12
