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165 Cards in this Set
- Front
- Back
How much is uterine blood flow in a gravid uterus versus a normal uterus?
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600-700ml/min (up to 900ml/min at term) versus 50ml/min
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How much of the placenta receives from the uterine blood flow?
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Up to 80-90% goes to placenta and the rest to the myometrium
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What causes the uterine vasculature to be vasodilated?
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1) enhanced release of vasodilators, such as PGI2 and nitric oxide, by the vascular endothelium; (2) high local estrogen concentrations, which lead to the diminished activity of key intracellular enzymes that mediate vasoconstriction; and (3) altered receptor-mediated G-protein coupling.
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What three major factors can cause decreased uterine blood flow during pregnancy?
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1) systemic hypotension 2) uterine vasoconstriction and 3) uterine contraction ** to some degree systemic hypertension, and hypertonic uterine contractions
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Name the top three differentials for hypotension during pregnancy?
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1) sympathetic blockade during regional anesthesia 2) aortocaval compression 3) hypovolemia
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Which drug(s) can be used to treat the hypotension as a result of sympathectomy during regional anesthesia?
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1) Ephedrine - has indirect alpha adrenergic and beta 1 adrenergic activity action causes increased SVR and HR, contractility (therefore increased preload) 2) Neosynephrine - alpha adrenergic agonist increasing afterload or SVR therefore increasing BP
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How much placental surface area is present on average?
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1.8m2
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How is the placenta arrangement contribute to substance exchange?
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The fetal tissue villi lie in maternal vascular spaces or intervillous space that are easily bathe by the uterine blood flow via uterine artery to uterine vein
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Describe the umbilical cord
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Umbilical cord attaches to the fetus. It contains two arteries that pump blood to the placeta. It also has a single vein that brings oxygenated blood back from the placenta to the fetus.
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Describe the placental exchange mechanism?
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1) diffusion - gas and small ions transport via diffusion, if < 1000 molecular wt, can diffiuse 2) bulk flow - water moves via bulk flow 3) active transport 4) pinocytosis 5) breaks
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How long can a fetus survive from oxygen deprivation?
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A fetus can survive up to 10 minutes from oxygen deprivation
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What can cause fetal oxygen deprivation?
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1) Umbilical cord compression 2) umbilical cord collapse 3) placental abruption 4) severe maternal hypoxemia 5) hypotension
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What compensation does a fetal physiology have in order to survive?
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Redistribution of blood flow to the brain, heart, placenta and adrenal gland. Fetus also decreases oxygen consumption; anaerobic metabolism
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How does a fetal hemoglobin differ from maternal hgb?
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fetal hemoglobin is shifted to left so that it has higher oxygen affinity, also fetal hgb is 15g/dl compared to 12g/dl in mother
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How does relative hypocarbia in mother help the fetus?
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High CO2 in fetus diffuses easier to mother's circulation due to lower CO2 concentration, also fetal Hgb has less affinity for CO2`
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How can delivery of medications be reduced to the fetus when administering to mother?
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Route of admin and timing of administration can influence the drug effects on the fetus
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Under general anesthesia, what is the usual concentration of inhaled agents to provide the least fetal depression?
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< 1MAC, combined intravenous, volatile and nonvolatile agents
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Which drug(s) has significant effect on the fetus and how?
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Morphine, remifentanil causes respiratory depression when given IV to the mother
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At what dose is fentanyl considered safe for mother and fetus when given intravenously?
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<1mcg/kg dose are safe and if given immediately before delivery.
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What property does muscle relaxants have the prevent them from crossing the placenta
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They are highly ionized
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Which local anesthetic(s) has the least ability to cross the placenta?
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High protein binding of bupivacaine and ropivacaine prevent them from crossing easily. Chlorprocaine is rapidly broken down by mom's plasma cholinesterases
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Which anesthetic adjuncts cross the placenta?
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Ephedrine, B blockers, vasodilators, phenothiazines, antihistamines, metoclopramide, atropine and scopolomine
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Which anticholinergic cannot easily cross the placenta
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Robinul
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Which intravenous induction agent have mild to moderate effect on uterine blood flow
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Propofol and Thiopental, but can decrease it further
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Which induction agent has the least effect on uterine blood flow
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Ketamine <1.5mg/kg, can have some hypertensive side effects as well that can couteract vasoconstriction, at 2mg/kg can cause hypertonic uterus
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Which drug can produce transient systemic hypotension
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Midazolam when used as an induction agent
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What are the undesirable side effects of inhaled volatile agents in lieu of pregnancy?
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Volatiles cause systemic vasodilation which causes hypotension thereby decreasing uterine blood flow, less than <1MAC usually is acceptable
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How does regional anesthesia affect uterine blood flow?
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If hypotension following sympathectomy is avoided, there is no significant effect of uterine blood flow
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What hormonal receptors increase on the myometrium just prior to labor?
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Oxytocin receptors, but not circulating oxytocin itself
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What are the characteristics of true labor?
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Contractions are more regular in frequency of 15-20 minutes apart, and strength of 25-60mm Hg, ruptured membranes, cervical dilation following effacement and cervical plug displacement
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How many stages of labor
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three stages: 1st - onset of labor and completion of cervical dilation, 2nd - full cervical dilation, descent of fetus, delivery of fetus, 3rd - delivery of baby to delivery of placenta
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What are the phases of the first stage
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Divided into the Latent phase 2-8 hours with 0 to 2cm dilatation, and the Active phase 6 hours with in addition of 4 to 8cm dilatation
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What are the phases of the Active phase
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Acceleration phase (2hrs), phase of maximum slope(2hrs) and deceleration phase(2hrs)
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What happens to minute ventilation when the mother is delivering?
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Minute ventilation increases by 300%, followed by an increase in oxygen consumption by up to 60%
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What happens to maternal PaCO2 during delivery?
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It can decrease to 20mm Hg which can cause decreased uterine blood flow and fetal acidosis
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What is the effect of delivery on the heart?
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Blood moves from the uterus to the circulation by up to 300 - 500mls an autotransfusion effect, giving a boost of 45% cardiac output, better than third trimester values
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What is the effect after delivery on the heart?
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Intense uterine contraction and involution suddenly relieves inferior vena cava compression as much as 80% prelabor values
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Does epidural anesthesia prolong labor and increase the chance of C-section?
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There is evidence that it does, although low dose bupivacaine 0.125% in 5mcg/ml fentanyl suggest that it does not
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What factors can prolong labor?
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Primigravida, prolonged labor history, high requirements for iv pain meds, oxytocin, large babies, small pelvis, fetal malpresentation
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What are some side-effects of regional anesthesia?
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Increased rate of low forceps delivery, loss of urgency to bear down, motor weakness
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Which vasopressor is indicated for low blood pressure and low heart rate during sympathectomy and has little effect on uterine contractions?
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Ephedrine 5-15mg
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Which receptors causes uterine contraction and which receptors causes uterine relaxation?
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Uterine contraction - alpha receptors
Uterine relaxation - beta 2 receptors |
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What is the role of oxytocin?
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Oxytocin can augment uterine contraction, half life of 3-5min, administered 0.5-8mU/min induction.
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What complication is associated with oxytocin?
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Oxytocin causes fetal distress due to hyperstimulation, uterine tetany, and maternal water intoxication
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What cardiovascular effects does oxytocin produce?
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Oxytocin can cause transient systemic hypotension due to vascular smooth muscle relaxation, resulting in a reflex tachycardia
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How is oxytocin administered after delivery of the fetus?
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Oxytocin can be given intramuscularly 10u or in one liter solution 20u up to 40u
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What other medications can augment uterine contractions following delivery?
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Methylergonavine (methergine) causes prolonged uterine contractions to treat uterine atony.
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What is an undesirable side effect of methergine?
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Severe hypertension, therefore it must be given intramuscularly 0.2mg
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What is hemabate?
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Carboprost tromethamine is a synthetic analogue to prostaglandin F2, stimulating uterine contractions, also used to treat uterine atony
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What is the route and dose of hemabate?
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It is given at 0.25mg IM every 15-90 minutes up to 2mg.
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What is the side effect of carboprost?
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Nausea, vomitting, diarrhea
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How is magnesium utilized?
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It is a tocolytic, administered IV bolus of 4gm followed by 2gm/hour to achieve 6-8mg/dl serum levels
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What side effects can Mg produce?
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Hypotension, heart blocks, muscle weakness and sedation
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What are the cardiac shunts in fetal physiology?
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Foramen ovale and ductus arteriosus
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Describe fetal circulation
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placenta->umbilical vein->portal circulation or ductus venosus->IVC->R atrium->foramen ovale or R vetricle->L atrium or Pulmonary Artery->L atrium to L ventricle or Ductus Arteriosus -> Aorta -> system circulation -> iliacs -> umbilical artery -> placenta
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At what week is fetal circulation and fetal respiratory system developed for extrauterine survival
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24-25 weeks
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At what week is surfactant produced?
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30 weeks surfactant, necessary for lung expansion after birth
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How much fluid is present in the lungs of the fetus at term?
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90mls
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How is the fluid in the neonate's lung excreted or removed?
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It is squeezed out during labor through the vagina and the remainder removed by the pulmonary capillaries and lymphatics
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What disadvantage does a C-section delivered baby have in comparison to a vaginal delivered baby?
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Typically they do not have the vaginal squeeze to push out the pulmonary fluids, therefore can suffer from transient tachypnea
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What pulmonary change occurs immediately after delivery?
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Pulmonary vascular resistance decreases, with the increase in oxygen and alveolar tension
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What happens to neonatal cardiac physiology after delivery?
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Increased pulmonary blood flow augments left heart filling, functionally closing the foramen ovale. Arterial oxygen tension causes ductus arteriosus to close
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What can reverse the normal changes of the newborn?
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Hypoxia and acidosis can prevent or reverse the changes
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What can result from neonatal hypoxemia and acidosis?
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Return of pulmonary hypertension, Increased pulmonary vascular resistance, left ventricular failure, right ventricular failure, right to left shunting across persistent ductus arteriosus and foramen ovale
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What considerations should a post-partum mother have to undergo general anesthesia?
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8 hours fasting, >7g/dl Hgb, H2 blocker, sodium citrate, reglan, using a rapid sequence technique, **cricoid pressure**, modest use of succinocholine
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What happens to MAC during pregnancy?
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MAC decreases by as much as 40% during pregnancy but returns after the 3rd day of delivery
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What happens to the mother's hormonal and endogenous opiod levels?
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Endogenous opiod levels and progesterone elevate which may contribute to the decrease in MAC
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How high is progesterone been detected in pregnant females?
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Up to 20 times the normal which may cause sedation
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How much regional anesthetic is required for pregnant moms?
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Generally less than a normal person due to the relaxation of the epidural venus plexus
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What is MLAC and its relation to EC50?
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Minimum Local Analgesic Concentration and median effective local anesthetic concentration or EC50 in a 20ml volume of epidural analgesia in the first stage of labor
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Does pregnancy increase susceptibility to local anesthetic?
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No
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What are the specific changes important for regional anesthesia as a result of an obstructed inferior vena cava?
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Distention of the venous plexus thereby increasing the epidural venous blood volume,
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What is the effect of a distended venous plexus in the epidural space?
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Decreased CSF volume, decreased CSF volume in the epidural space, increased epidural space pressure
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What is the potential complication as a result of decreased CSF volume and CSF volume in the epidural space?
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Enhanced cephalad spread of anesthetic; increased risk of puncture of the dura during an epidural anesthesia; increased risk of epidural vein puncture by catheter and potential intravascular injection
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What respiratory parameter increases during pregnancy?
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O2 consumption (20-50%), minute ventilation (50%), tidal volume (40%), respiratory rate (15%), PaO2 (10%), 2-3 diphosphoglycerate
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What happens to the diaphragm at the third trimester?
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It is elevated but the chest diameter increases anterior and posteriorly, but there is diaphragmatic restriction
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What respiratory parameters are decreased in pregnancy?
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FRC (20%), PaCO2 (15%), HCO3 (15%), airway resistance, physiologic dead space
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What promotes rapid desaturation during periods of apnea?
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Decreased FRC, increased O2 consumption
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What further promotes hypoxemia during pregnancy?
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Closing volume exceed FRC up to 50%, with increased atelectasis when they are supine at term
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What happens to the airway and risk for difficult intubation and hypoxemia in pregnant females?
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Pharyngolaryngeal edema, Weight gain, Increased breast size, Full dentition, rapid onset of hypoxemia during apnea as a result of decreased functional residual capacity, decreased cardiac output secondary to aortocaval compression, and increased oxygen consumption
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How do you overcome a possibility of a difficult intubation?
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1) Use short handle scope
2) Use pediatric scope handle 3) Direct laryngoscope handle laterally toward right shoulder 4) seperate blade from handle when inserting into the mouth? 5) Sniffing position to optimize the occiput and neck alignment |
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What are increased cardiovascular parameters of pregnancy?
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Blood volume (35%), Plasma volume (45%), Cardiac output (40%), Stroke volume (30%), heart rate (20%)
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What effect is the effect of plasma volume in relation to red blood cell mass volume?
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Increased plasma volume in excess of an increase in red cell mass volume produces dilutional anemia, but reduces blood viscosity
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What relationship does a decrease Hgb concentration have to delivery of oxygen to tissues?
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Increased cardiac output and rightward shift of the oxygen dissociation curve of Hgb overcomes the decreased Hgb.
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What are decreased cardiovascular parameters in pregnancy?
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PVR or SVR (afterload) 15%, systolic blood pressure (5%), diastolic blood pressure (15%), pulmonary resistance (30%)
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What happens to the blood volume during pregnancy?
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Increased by 1000-1500ml (90ml/kg), allowing them to tolerate blood loses from cesarean (800-1000ml) as well as SVD (400-500ml)
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How does cardiac output increase?
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Cardiac output = HRxSV, where the HR and SV increases with pregnancy. Both heart chambers increase with myocardial hypertrophy,
Stroke volume - influenced by preload, afterload, contractility (myocardial viability, chamber size, myocardial oxygen consumption), heart rate - SANS, PANS |
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What position can cause a decrease in cardiac output at about 28 weeks of pregancy?
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Supine position can compress the aorta and IVC complete and near complete
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What syndrome is associated with supine position of the gravid uterus?
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20% incidence of supine hypotension syndrome: hypotension, nausea, vomiting, pallor and sweating
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What position relieves the supine hypotension syndrome?
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Left lateral decubitus restores venous return from lower body
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What detrimental effects can an aortocaval compression have during pregnancy?
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Fetal hypoxia and asphyxia due to hypotension due to sympathectomy or general anesthesia; treated by IV volume infusion, left uterine displacement, and adrenergic agonists
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What EKG changes can occur during pregnancy?
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On EKG a left axis deviation due to left and upward displacement of the heart, T wave changes
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What cardiovascular physical exam finding is present?
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Grade I or II systolic ejection flow murmur, splitting of S1 (M-T) closure, with an S3 (wall sound), possible pericardial effusion
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What are some renal effects of pregnancy?
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Increased renin and aldosterone, during 1st trimester increased renal blood flow and GFR, but decreased GFR after 3rd trimester, results with low BUN/Cr (.5-.6 /8-9mg/dL)
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What are some GI effects of pregnancy?
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GERD, esophagitis are common
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What happens to the stomach during pregnancy?
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It is upward/anteriorly displaced, decreased LES tone due to progesterone
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What is the role of gastrin during pregnancy?
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It causes increased gastric acid secretion
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What happens to gastric volume and pH during labor?
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Decreased pH <2.5, increased volume up to 25ml
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How does a laboring mother's GI increase risk for aspiration?
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Labor decreases gastric emptying, administration of opiods and anticholinergics can cause decreased LES tone and gastric emptying with increased nausea and vomiting risk
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How is the hepatic system affected?
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Decreased albumin production, decreased pseudocholinesterase production, progesterone inhibits CCK action on gallbladder emptying
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What coagulation factors are increased during pregancy
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7,8, 9,10,12 increase promoting a hypercoagulable state that can prevent blood loss
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What coagulation factor and blood components is decreased during pregnancy?
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11 and platelets
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What co-factors are consumed quickly by both mom and fetus?
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Iron and folate can cause anemias if supplements are not taken
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What immune response are changed during pregnancy?
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WBCs are increased but cell mediated responses are delayed that can promote viral infections
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What causes insulin resistance during pregnancy?
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HCG, even though there is a relative increase of insulin hypoglycemia exists
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What kind of nutritional status exists during pregnancy?
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Relative starvation due to increased fatty acid metabolism, amino acid metabolism, and high ketone levels
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What hormone promotes increased T3 and T4 levels?
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HCG and estrogens cause hypertrophy of the thyroid gland
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Uterine blood flow is consistently decreased after the administration of which induction agent?
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Thiopental 4mg/kg
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What percentage of pregnancies are affected by pre-eclampsia?
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22%
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Magnesium sulfate is an anticonvulsant in patients with pre-eclampsia and may produce the following:
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1)Sedation (CNS)
2) Hypotension (CV) 3) Respiratory paralysis (Pulm) 4) Tocolysis (GU) |
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Normal FHR
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110-160 bpm
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Leading cause of maternal death or mortality in the US is
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1) Pulmonary Embolism (22%)
2)Pre-eclampsia (20%) 3)Other medical conditions (19%) 4) Infection (14%) 5) Cardiomyopathy (11%) 6)CVA (6%) 7)Hemorrhage (5%) 8)Anesthesia (2-3%) |
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What is the p50 of fetal hemoglobin?
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19-20 mm Hg (pO2)
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What is the period considered to be pre-term labor?
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Before 35 weeks of gestation
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What measures are used to prolong pregnancy and abolish pre-term labor
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Bed-rest, tocolysis, administration of glucocorticoids to mother to encourage lung maturity for 24-48 hours, antibiotics
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What is the most commonly utilized medication for tocolysis?
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B2 agonist, terbutaline or ritrodine
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What are the side effects of ritrodine?
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1) Tachycardia (CV)
2) Hyperglycemia (Endo) 3) Pulmonary Edema (Pulm) 4) Hypokalemia |
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When does cardiac output return to non-pregnant values during the post-partum period?
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Within 2 weeks after delivery
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Which induction agent can cause bronchospasm, laryngospasma and subsequent apnea due to depressed respiratory drive?
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Thiopental
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Which induction agent is appropriate for both asthmatic as well as a hypertensive pregnant patient?
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Propofol
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What are fetal/neonatal side effects of magnesium sulfate?
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Lethargy, hypotonia, respiratory depression
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Which block can be used during the second stage of labor if inadequate pain relief is obtained?
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Pudendal block with lidocaine 1% or chlorprocaine 2% at the sacrospinous ligament 1-1.5cm using an Iowa trumpet or Koback guide
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What are the hallmarks of Amniotic Fluid Embolism?
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1) acute pulmonary embolism 2) DIC 3) uterine atony 4) seizures
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When is the fetus most critically affected by teratogenic agents?
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3 to 8 weeks when organogenesis occurs
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What route is acceptable for giving naloxone for opioid effects on the newborn?
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Naloxone 0.1mg/kg via IV or ETT
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What are the parameters for Apgar scores?
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1) HR =0 = 0, < 100 =1, >100 =2
2) RR =0 =0, slow,irreg=1, crying=2 3) musc=0=0,flexion=1,active=2 4)irritable =0=0, grimace=1,cry=2 5)color blue=0,body pink, extremities blue=1, all pink =2 |
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What is the fetal rate of normal oxygen consumption?
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21ml/min on average with a 42ml oxygen store
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List the symptoms of Amniotic Fluid Embolism?
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1) Acute pulmonary embolism 2) DIC 3) Uterine Atony 4) Seizures 5) Pulmonary Edema 6) Cardiogenic collapse with left ventricular dysfunction
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Describe what may occur to the fetus with mother with known myasthenia gravis
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The neonate may experience placental transfer of maternal antibodies causing myasthenia syndrome
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What are the parameters for pregnancy induced hypertension
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SBP > 140 or DBP > 90, or consistent increase in systolic or diastolic pressure by 30 or 15mm Hg respectively
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PIH is associated with which syndromes
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1) Pre-eclampsia
2) Eclampsia 3) HELLP - Hemolysis Elevated Liver Enzymes, Low platelets |
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The most frequent causes of DIC are
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1) Preeclampsia
2) Placental abruption 3) Sepsis 4) Retained dead fetus syndrome 5) Amniotic fluid embolism |
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Anesthetic management for pregnancy with Eisenmenger syndrome
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1)Maintain adequate SVR.
2)Maintain intravascular volume and venous return. Avoid aortocaval compression. 3)Prevent pain, hypoxemia, hypercarbia, and acidosis, which may cause an increase in pulmonary vascular resistance. 4)Avoid myocardial depression during general anesthesia. |
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What are the causes of uncontrolled bleeding that may require emergency C-section?
|
1) Prolonged third stage of labor
2) Pre-eclampsia 3) Multiple gestations 4) Forceps delivery 5) Uterine Atony 6) Retained placenta 7) Obstetric lacerations 8) Uterine inversion 9) Use of tocolytics |
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What are the most common malpractice claims in obstetric anesthesia?
|
1) Maternal nerve damage (21%)
2) Newborn brain damage (15%) 3) Headache (14%) 4) Maternal death (12%) 5) Back pain (10%) 6) Emotional distress (8%) 7) Pain during surgery (7%) 8) Maternal brain damage (6%) 9) Newborn death (6%) 10)Aspiration Pneumonia (1%) |
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Why is morphine not used alone in epidurals during the first and second stage of labor?
|
It has a slow onset (45-60min) and prolonged (4-6h) at doses 0.25-0.5mg, so it has to be used with fentanyl 12.5-25mcg
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What is the management of meconium staining presence in newborns?
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Intubation with suctioning until the material in the trachea is clear (no more than 3 times), oxygen, suction stomach
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What is the induction agent of choice for emergency c-section with a hypotensive or hypovolemic patients?
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Ketamine at 0.5 to 1mg/kg and succinocholine 1 to 1.5mg/kg
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Which of the respiratory parameters is affected least at term?
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Vital capacity
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Describe the epidural space
|
Epidural space surraounds the dura mater posteriorly, laterally and anteriorly
|
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Which opioid both have anesthetic and narcotic properties
|
Meperidine
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What is the dose of epinephrine for resuscitation of a neonate
|
0.01-0.03mg/kg or 0.1-0.3 ml/kg of 1:10,000.
|
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What is the epidural dose of morphine at the end of surgery?
|
3-5mg lasts for 6-24 hours but can trigger HSV
|
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What is the undesirable side effect of spinal demerol
|
Hypotension
|
|
Define pre-eclampsia
|
Hypertension SBP > 140 DBP > 90, or consistent increase in systolic by 30 and diastolic by 15, proteinuria >500mg/d, edema, occurring at the 20th week of gestation and resolving after delivery
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What is in amniotic fluid that would cause AFE
|
Desquamated fetal tissue, prostaglandin, leukotrienes
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What are the patient's symptoms associated with AFE
|
Cyanosis, tachypnea, shock and generalized bleeding
|
|
What is the dose range for bupivacaine for spinal anesthesia?
|
10-15mg
|
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What is the dose range for preservative free morphine, fentanyl and sulfentanil?
|
0.2-0.3mg morphine
12.5-25 mcg fentanyl 5-10 mcg sulfentanil |
|
What properties of substances allow them to passively go through the placenta to the fetus
|
1) decreased maternal protein binding
2) low molecular wt 3) high lipid solubility |
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What property does muscle relaxants have that prevent them from crossing the placenta
|
Most are highly ionized
|
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Compare maternal pH versus fetal pH
|
Maternal pH is higher, lower pCO2 versus fetal pH lower, higher pCO2
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Features of severe pre-eclampsia
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proteinuria greater than 5g/24hours, visual disturbance, oliguria <400ml/24hr, epigastric pain, hepatic rupture, pulmonary edema, impaired liver, restricted fetal growth, throbocytopenia
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What are some tocolytics effective for pre-term labor?
|
Terbutaline, Magnesium, Nifedipine, Ritrodine
|
|
What are the complications of epidural anesthesia?
|
Hypotension, intrathecal injection, postdural puncture headache, maternal fever, less common hematoma and abscess, arachnoiditis
|
|
What are risks of umbilical cord collapse?
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Long cord, malpresentation, low birth weight, grand parity , multiple gestations, artificial rupture of membranes
|
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What is preterm labor and some risks?
|
occurs between 20 to 37 weeks of gestation risks include advanced maternal age, inadequate care, unusual body, increased activity, infections, prior preterm, multiple gestations, medical illness
|
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Which drugs are antagonized by 2-chlorprocaine if it is administered first in the epidural space?
|
1) Fentanyl 2) Morphine 3) Bupivacaine
|
|
What are the criteria for an epidural anesthesia?
|
1) Pt decision 2) Obstetric decision 3) No fetal distress 4) good regular contractions 3-4 min apart x1minute 5) cervical dilatation 3-4cm 6) engagement of fetal head
|
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What level is required to be blocked during the first stage of labor
|
T10-L1
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What level is required to be blocked during the second stage of labor
|
T10-S4
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What level is generally required for cesarean section?
|
T4
|
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Which local anesthetic is associated with transient neurological symptoms
|
Lidocaine
|
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Which local anesthetic is associated with cardiac arrest following inadvertent intravenous injection?
|
Bupivacaine - high protein binding and lipid solubility, accumulation in the cardiac conduction system
|
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Which local anesthetic is associated with methemoglobinemia?
|
Prilocaine
|