Obstetrics II Flashcards
How does pregnancy effect WBC count?
Causes benign leukocytosis, so WBC count isn’t a reliable indicator of infection
Are parturients at higher or lower risk for intraoperative awareness?
Oddly enough, higher. Because RSI for OB patients doesn’t include versed or opiods, for the baby’s sake
How are plasma cholinesterases impacted by pregnancy?
They decrease by 25%, but increased blood volume offsets this decrease and prolonged NMB is uncommon
How does pregnancy impact protein binding levels?
Decreases it, due to lower albumin and alpha glycoprotein concentrations. Results in a larger fraction of unbound, free drug -> increased risk of drug toxicity
Do pregnant women need a higher or lower loading dose of a medication?
Usually has to be higher, because clearance is dramatically increased and the volume of distribution is larger
Most structural abnormalities from teratogens occur when exposure falls between which days?
31-71, during organogenesis
Which infections are teratogenic?
CMV, Herpes, Parvo, Rubella, Syphilis, Toxoplasmosis, VEEV
What is the etiology of most developmental defects?
Genetic transmission and chromosomal abnormality
Airway edema in parturients is made worse by:
Pre-E
Tocolytics
Prolonged Tburg
Why is FRC reduced in pregnancy?
As the rib cage widens and tidal volume increases, the volume at end expiration is much lower
How does a decrease in FRC impact airway closure?
In pregnant women, the FRC is BELOW the closing capacity, which means the airways close off during tidal breathing
How does progesterone impact tidal volume?
It’s a respiratory stimulant
It increases minute ventilation by 50%
What increases more: tidal volume or respiratory rate?
Vt increases by about 40%
RR increases by about 10%
What hormones contribute to vascular engorgement and hyperemia in pregnancy?
Estrogen
Progesterone
Relaxin
What type of laryngoscope handle is useful in pregnant women?
Datta handle (short)
How does progesterone impact vasculature?
It causes nitric oxide release, leading to vasodilation
Does PT/PTT increase or decrease during pregnancy?
Decrease (takes less time to form a clot)
What is the most common cause of thrombocytopenia in pregnancy?
Gestational thrombocytopenia
How is BP effected during pregnancy?
MAP and SBP stay the same. DBP decreases.
What % of CO goes to the uterus?
10%
What is uterine blood flow in ml/min?
700ml/min
Is uterine blood flow autoregulated?
No. Almost entirely dependent on MAP and CO.
Is uterine blood flow reduced by phenylephrine?
No
How efficiently a drug will traverse any given membrane is determined by which principle?
Fick’s Principle
What are drug characteristics that favor maternal transfer?
Molecular Weight < 500
High Lipid Solubility
Non-ionized
Non-polar
Which drugs have no placental transfer?
NMBAs
Heparin
Glycopyrrolate
Insulin
Does phenylephrine cause more or less fetal acidosis than ephedrine?
Less
What afferent pathway innervates the uterus and cervix?
Visceral C fibers from the hypogastric plexus
Which LA reduced the efficacy of spinal morphine?
2-Chloroprocaine
It antagonizes mu and kappa receptors in the spinal cord
How are bupivacaine, ropivacaine, and levobupivacaine related?
Ropivacaine is the R-enantiomer of bupivacaine, which is a racemic mixture of both the R and S enantiomer
Levobupivacaine is just the S enantiomer
Compare ropivacaine to bupivacaine in terms of spinal anesthesia
Decreased risk of CV tox
Decreased potency
Decreased motor block
Why isn’t lidocaine frequently used in labor epidurals?
It causes high degree of muscle blockade (which makes it ideal for C/S)
Also, it crosses the placenta to a greater degree than the alternatives
Can you use lidocaine for a Spinal?
No. Its associated with neurotoxicity in the intrathecal space
Which opioid possesses LA properties?
Meperidine
There are three ways you can get a total spinal:
- Epidural dose in the subarachnoid space
- Epidural dose in the subdural space
- Single shot spinal after a failed epidural
How can you rule out subdural catheter placement during an epidural placement?
You can’t. It’s just bad luck.
How does a subdural epidural catheter placement manifest?
Within 10-25 min the patient will experience symptoms of a total spinal
Why do subdural catheters result in higher sensory blocks?
Because its a very low volume space. An epidural dose will fill the entire space up to the cervical level
What are the symptoms of a total spinal?
Dyspnea, difficulty phonating, hypotension, loss of consciousness from hypotension
What is the initial treatment for a total spinal?
pressors, fluids, leg raise, uterine displacement
What are some differential diagnoses for a total spinal?
Anaphylaxis, eclampsia, AFE
Why is magnesium a smooth muscle relaxant?
It antagonizes calcium, interfering with muscle contraction and hyperpolarizing membranes in excitable tissues
What is the first clinical sign of magnesium toxicity?
Loss of DTRs
How does magnesium impact NMBA?
Potentiates them
What are the initial treatments for hypermagnesemia?
Calcium gluconate
Diuretics (to speed up excretion)
Supportive Measures
What is the second line uterotonic?
Methergine
What is the third line uterotonic?
Hemabate
What is the correct methergine dose?
0.2mg IM
What is the correct dose of hemabate?
250mcg IM
Which uterotonic should be avoided in asthmatics?
Hemabate
A is for Asthma
Which uterotonic causes diarrhea?
Hemabate
What can happen if you give oxytocin too quickly?
CV Collapse
What can happen if you give methergine IV?
Vasoconstriction, hypertension, cerebral hemorrhage
What is another name for Hemabate?
Prostaglandin F2, Carboprost
How does general anesthesia impact maternal mortality?
17x higher!!!!
What are some situations where a general anesthetic is necessary for a C/S?
Hemorrhage
Fetal Distress
Coagulopathy
Refusal of regional
Contraindications to regional
Does general anesthesia result in greater or less hemodynamic stability?
More stability than neuraxial
Triple prophylaxis against aspiration includes which three drugs?
Bicitra (neutralizes gastric acid)
Ranitidine (reduces gastric acid secretion)
Reglan (increases emptying and LES tone)
Does pregnancy increase or decrease the incidence of myalgia from Succinylcholine?
Decreases it. A defasciculating dose usually isn’t needed
Normal amniotic fluid volume is approximately:
700 ml
What is the best gestational age to perform a non-obstetric surgery?
Ideally the 2nd trimester
Less chance of teratogenicity than 1st T
Less chance of PTLD than 3rd T
What is a normal maternal PaCO2?
30
How long after delivery should elective surgery be delayed?
2-6 weeks
Define chronic hypertension
Occurs before 20 wks
At risk of developing Pre-E
Define gHTN
Develops after 20 wks with no s/s of pre-E
When is proteinuria not required for a diagnosis of Pre-E?
Severe features:
RUQ pain
CNS s/s
IUGR
Thrombocytopenia
Elevated Liver Enzymes
What maternal age is most susceptible to pre-E?
<20 and >35
On a molecular level, what is so different about a pre-E placenta vs a normal one?
Normal placentas produce thromboxane and prostacyclin in equal amounts
Pre-E placentas produce 7x more thromboxane than prostacyclins
An increase in thromboxane causes:
Increased Platelet Aggregation
Vasoconstriction
Increased uterine irritability
Decreased placental blood flow
What is the labetalol regimen for severe HTN?
20mg IV initially
Then 40-80 mg q10min
Max dose 220mg
What is the hydralazine regimen for severe HTN?
5mg IV q20 min
Max 20mg
What is the Nifedipine regimen for mild hypertension?
10mg PO q20 min
Max dose 50mg
Patients with severe Pre-E have an exaggerated response to _______ and _______
sympathomimetics
methergine
How does magnesium protect end organs?
Fibrin deposits reduce organ perfusion. Magnesium decreases the rate of deposition
What is Cocaine’s MOA?
It inhibits NE reuptake in the synaptic cleft, increasing SNS tone throughout the body
Cocaine is associated with what blood dyscrasia?
Low platelets
Risks for uterine atony include:
Multiple gestation
Pitocin use
Multiparity
Polyhydramnios
DIC is associated with an increased incidence of:
AFE
Abruption
IUFD
