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Airway Parameter Changes
Chest wall excursion
FEV1, FEV1/FVC, Flow volume loop, closing capacity
- Decreased by 50%
- No change
Does FRC increase or decrease?
FRC decreases starting about the 5th month b/c relaxed diaphragm. The FRC is decreased by as much as 70% in the supine position when compared to upright in the pregnant patient.
Describe the shifting of the heart during pregnancy
The heart shifts anteriorly and to the left.
Apical impulse moves cephalad to 4th intercostal space and laterally to the MCL
Grade 1-2 murmur normal
Cardiac hypertrophy is normal
What is the total blood volume of a patriurient patient?
Cardiac output increases by ____ during the latent phase
CO increases by ____ during the active phase
CO increases by _______ during the expulsive stage of labor
What lab values are seen in maternal anemia?
A high Hgb (> 14) may indicate a low-volume state
Describe the anticipated normal BP in pregnant women
BP normally not increased even though CO is, due to decreased SVR and PVR and increased aortic compliance. The decreased SVR is partially due to the low resistance uterine vascular bed
What can the venodilation seen in pregnancy affect in terms of regional pain management?
increase incidence of accidental epidural vein puncture
How much blood loss can a healthy patruient endure?
Up to 1500 ml
Name three events that may cause a low volume state
- inappropriate diuretic use
What should we strive to maintain the systolic BP at?
Symptoms of aortocaval compression (6)
- 1. hypotension
- 2. pallor
- 3. sweating
- 4. nausea
- 5. vomiting
- 6. changes in mentation
- Occurs when in supine position
Treatment of aortocaval compression
- FIRST: left uterine displacement
- Then, fluids, oxygen, ephedrine.
What position should you avoid if aortocaval compression in suspected?
Why could neosynephrine be a good choice for use in a pregnant hypotensive episode?
Neo is a direct alpha agonist, and causes less fetal acidosis
Hypotension following spinal anesthesia for C-section is a result of
- sympathetic blockade
- which leads to decreased SVR, VR, and CO
Why does ephedrine have an increased incidence of fetal acidosis?
It crosses the placenta
When should phenylephrine be avoided?
Maternal bradycardia because of the reflexive bradycardia it can cause
Side effects of oxytocin
- Cardiovascular: hypotension, tachycardia, arrhythmias, MI, coronary vasoconstriction
- Water retention
- Seizures and coma
Describe the etiology of oxytocin
- Synthesized in hypothalamus, stored in the posterior pituitary
- Oxytocin receptors on: uterus, ovary, breast, kidney, CNS, endothelial cells, heart.
Onset and half-life of pitocin
- onset: 1-2 minutes
- half life: 3-10 minutes
How is thrombocytopenia during pregnancy defined?
Platelet count < 150,000
At what platelet count should a provider not preform a spinal or epidural anesthetic?
Less than 75,000
In the thrombocytopenic patient, what is the preferred method of regional anesthesia and why?
Spinal, because the smaller needle presents less risk of bleeding.
Name 2 absolute contraindications for neuraxial block
- Clinical signs of bleeding
- progressively decreasing platelet counts
How does estrogen affect the RAA system?
Estrogen enhances renin production which increases blood volume in the end of the cycle.
Albumin levels fall from __ in the 1st trimester to ____ at term
Plasma cholinesterase falls by --- % at term
This is significant when considering sux. as the NMB for RSI (longer duration)
Which clotting factors increase in pregnancy?
1, 7,8,9,10, 12
Which clotting factors decrease in pregnancy?
11, 13, PT, PTT, antithrombin 3, PLT count
Which clotting factors remain unchanged during pregnancy?
Factors 2 & 5
Is the parturient hypercoagulable or hypocoagulable?
Hugh's syndrome is AKA and is what?
- Antiphospholipid syndrome
- Prothrombotic disorder resulting in venous and arterial thrombosis
Causes platelet adhesion
Lupus anticoagulant and anticardiolipin antibodies present
What is the apparent mechanism of mortality for fetus's in antiphospholipid syndrome?
pH < 2.5, GRV > 30ml.
Increased progesterone reduces tone of GE sphincter, gravid uterus changes angle of GE junction
This syndrome is a chemical pneumonitis caused by aspiration during anesthesia, especially during pregnancy
At what point is a parturient considered a full stomach?
What can be expected with BUN and CRT levels?
Compression of the ureters by the uterus may result in
urinary stasis= frequent UTIs
What causes insulin resistance seen in pregnancy?
hormones secreted by the placenta, mainly placental lactogen
How should you adjust the MAC for pregnant patients?
Decrease by up to 40%
Indications for C-section:
- failure to progress,
- non-reassuring fetal status,
- cephalopelvic disproportion,
- previous uterine surgery
Hyperbaric LAs sink or rise in the spinal column?
Sink. The addition of dextrose accomplishes this
Which LA is most commonly used for spinal anesthesia in the parturient patient?
A ___ MAC will result in vasodilaton that causes increased blood loss during c-section
- 2-cholorprocaine 3%
- lidocaine 2%
- bupivacaine 0.5%
How are nitroglycerin and terbutaline used in L&D?
relax the uterine muscles to allow for external cephalic version
Name 4 factors that complicate post-op recovery and decrease maternal satisfaction:
- post-op shivering
What vessel carries oxygenated blood back to the fetus from the placenta?
Is the only fetal vessel that carries fully oxygenated blood at a sat of 80%. After mixing with fetal shunts, the delivered blood has a sat of 67%
How many arteries and veins are in the umbilical cord?
2 arteries and 1 vein. Arteries carry oxygen poor blood back to the placenta, and the vein carries oxygen rich blood to the fetus from the placenta.
attachment point for umbilical vein to the fetal inferior vena cava
shunt opening between the right and left atrium
fetal septum between right and left atrium. Is a valve that prevents blood from moving in reverse direction (left to right)
With first breath, the _____ _____ and ________ ______ close.
foramen ovale and ductus arteriosus
Factors which optimize fetal oxygenation:
- 1. uniform perfusion of the placenta
- 2. production of a fetal Hgb with a greater oxygen affinity than maternal Hgb.
- 3. High fetal cardiac activity
- 4. increased fetal tissue perfusion
Three microscopic tissue layers found in placental membrane:
- 1. Fetal trophoblasts
- (cytotrophoblast, syncytiotrophoblast)
- 2. Fetal connective tissue
- 3. endothelium of the fetal capillaries
Placental vasculature normally exists in a _________ state.
Uterine blood flow equation
Uterine blood flow is 10% of maternal cardiac output at term, which is approximately:
Uterine blood flow is proportional to the mean perfusion pressure
it is not autoregulated
Factors that decrease UBF:
- systemic hypotension
- increased uterine venous pressure
- vena cava compression
- uterine contractions
- valsava maneuver with pushing
- drug induced uterine hypotonus
- increased uterine vascular resistance
- vasopressin increases uvr
Name the maternal arteries that supply the placenta
Two layers of the placenta
myometrium and endometrium
basal and spiral arteries supply the endometrium in the basal plate
Where does exchange take place with fetal and maternal blood?
intervillous space in the basal plate
Fick principle relies on 5 factors:
- Molecular weight
- Concentration gradient
- Surface area
- Membrane thickness
What is the most important factor that affects diffusion?
What two substances were identified as those who utilize facilitated diffusion for transport?
lactic acid and glucose
Which crosses the placenta more easily:
Drugs that bind to albumin or a-alpha glycoprotein?
Albumin, b/c a-alpha glycoprotein binds drugs more tightly
What is transported via active transport?
- Amino acids, large ions, vitamins.
- Uses ATP, is fast
How are mother's antibodies transferred to the fetus?
What are the 5 mechanisms of placental exchange?
- 1. diffusion
- 2. bulk flow (facilitated diffusion)
- 3. active transport
- 4. pinocytosis
- 5. breaks
what causes a right shift in the oxyhemoglobin curve?
acidosis, hyperthermia, increased 2,3 DPG
what causes a left shift in the oxyhemoglobin dissociation curve?
alkalosis, hypothermia, decreased 2,3 DPG, carbon monoxide
IV epidural test dose can decrease uterine blood flow by
40% during the 3 minutes of duration
Normally, the fetus's oxyhemoglobin curve is shifted to the ___ of mothers'
The Hgb of fetal blood is about
15 g/100ml blood
mothers' is about 12
when the curve is ----- shifted, Hgb binds more tightly
Even though the fetus is more acidotic to than the mother, the Hgb curve is shifted to the left because
increased Hgb affinity for oxygen
How do inhalational agents affect the uterus?
Potent uterine relaxant properties
effects seen in dose dependent manner
Is warfarin OK for pregnant patients?
- It crosses the placenta and is associated with fetal demise and congenital defects.
Heparin and lovenox are OK to give
What do local anesthetics do to uterine blood flow?
exert a vasoconstrictor property. Normal concentrations used should be OK. Bupivicaine exerts a greater effect than cholorprocaine or lidocaine
Which LA is safe from fetal trapping and why?
Cholroprocaine. Because it is metabolized so quickly there is no opportunity for the drug to accumulate in significant amounts.
Name some anesthetic drugs that cross the placenta
- Beta agonists
- induction agents
- inhalational agents
- local anesthetics
Name some anesthetic drugs that do not cross the placenta
- NMBs (DMBs in normal doses not > 300 mg)
too little amniotic fluid
Fetal hydantoin syndrome
- craniofacial abnormalities
- caused by Dilantin use in pregnancy
Ace inhibitors during pregnancy
fetal renal dysplasia and oligohydramnios
benzodiazepines birth defects
antidepressants birth defects
Prozac the only one associated with defects
- exposure in 3rd trimester= greater incidence of preterm delivery
- lower birth weight
Coumadin birth defects
x-linked chrondrodysplasia punctata (CDPX)
which steroid is preferred for maternal illness?
which steroid is preferred to speed fetal lung development?
betamethasone and dexamethasone
Which antibiotics are safe for partriurients?
PCN, cephalosporin, erythromycin
Should try and avoid use, but these are preferred if must be used.
sulfonamides in 3rd trimester increase the risk of hyperbilirubiemia
thinning of the cervix
production of relaxation by pharmacologic agent
uterine contractions are monitored with
tocodynamometer and intrauterine pressure catheter
relation of the baby in relation to the pelvis
- positive station= below the pelvis
- negative station= above the pelvis
First stage of labor
onset of labor until dilation complete
during stage one
before active labor, starts a few weeks before birth
during stage one
pain initially at 1 T11-12, then progresses to T 10-12 and L1
second stage of labor
from complete cervical dilation until delivery of neonate
- onset of perineal pain is the signal of fetal descent
- involves T10-S4 dermatomes
Marcaine labor epidural concentration
C-section epidural concentration
0.125% or 0.0625%
0.25% to 0.5%
Spinal 0.75% (7.5 mg in 2 ml)
Three P's of labor and delivery
Passageway (bony pelvis and soft tissues)
nullipara prolonged second stage of labor
> 2 hours without regional
> 3 hours with regional
multipara prolonged second stage of labor
> 1 hour without regional
> 2 hours with regional
3rd stage of labor
from birth of the baby to the delivery of the placenta
4th stage of labor
the hour after the delivery of the placenta. Most common time for uterine atony and uncontrolled bleeding.
Boggy uterus requires fundal massage
Test dose for epidural
3-5 ml 1.5% lidocaine (45-75mg) with 1:200,000 epi (15-25 mg)
Lidocaine spinal dosage limit
- concentration not to exceed 2%
the portion of the fetus felt thru the cervix on vaginal examination
The best presentation is
Left occiput anterior
Frank - 60% of time
complete- 10% of time
incomplete- 30% of time
Risks of breech delivery
- cervical laceration
- perineal injury
- shock from hemorrhage
- retained placenta
- fetal intracranial bleed
retraction of the head back toward the vagina at delivery
dose: 0.25mg IM q 15-90 minutes to a max of 2 mg
Side effects: tachycardia, N/V, diarrhea
dose: 0.2 mg IM single dose
- Side effects: severe maternal htn
- severe and prolonged uterine contractions
- Dose: 10-40 units to 1 liter bag LR
- Half life 3-5 minutes
Side effects: hypotension, tachycardia, arrhythmias, MI, coronary vasoconstriction, N/V, Flushing, water retention, hyponatremia, seizures and coma