Ob Anesthesia Module B, Part Ii

Front 1

What is the most common non-hemorrhagic emergency in OB?

Back 1

Fetal distress

Front 2

What is the normal fetal heart rate?

Back 2

120-160bpm
<120bpm = fetal bradycardia
>160bpm = fetal tachycardia

Front 3

What is the nomral PaCO2 & PaO2 in the normal fetus?

Back 3

PaCO2 = 48torr (at maternal PaCO2 of 40-45)

PaO2 = 30 torr as leaves placenta

Front 4

What are two signs of fetal hypoxia?

Back 4

Fetal bradycardia
Late decelerations

Front 5

When does fetal acidosis occur?

Back 5

When fetal pH <7.20, 7.20-7.24 is considered pre-acidotic

Front 6

What causes fetal acidosis?

Back 6

fetal hypoxia & the resulting anaerobic metabolism

Front 7

Which local anesthetic crosses the placenta the least?

Back 7

Chloroprocaine b/c it is rapidly hydrolyzed; the amide least likely is bupivacaine d/t it's 95% protein binding

Front 8

What are the advantages of chloroprocaine in OB anesthesia?

Back 8

Low potency, low cardiotoxicity, rapidly metabolized by plasma cholinesterase,

Front 9

Which anesthetic agen is best for an epidural in a parturient with an acidotic fetus?

Back 9

Chloroprocaine

Front 10

Which amide local anesthetic most extensively crosses the placenta?

Back 10

Most-to-least: Mepivacaine, Etidocaine, Lidocaine, Ropivacaine, Bupivacaine

Front 11

Discuss Ion trapping:

Back 11

non-ionized form of LA crosses placenta & once in fetal circulation which is more acidotic in nature (pH 7.03-7.23) becomes "trapped"

Front 12

Will maternal alkalosis faciltiate diffusion of the LA accross the placenta?

Back 12

Yes, alkalosis shifts a greater proportion of the LA to its non-ionized form which can cross the placenta easier; maternal alkalosis from hyperventilation

Front 13

Will fetal acidosis facilitate ion trapping?

Back 13

Yes, leads to increased ionized fraction of the LA & won't be easily passed back to maternal circulation

Front 14

What are 5 complications associated with placement of a fetal scalp electrode?

Back 14

Ecchymoses, lacerations, leakage of CSF, sepsis, scalp abscess-most common

Front 15

What is normal FHR beat to beat variability?

Back 15

3-6bpm variability implies intact oxygenated CNS; atropine causes loss of FHR variability as well as fetal hypoxia & maternal meds

Front 16

What are early decelerations?

Back 16

Early/Type I decelerations are decreases in FHR of 10-40bpm that coincide with uterine contractions; these are benign, start at onset of contraction & are greatest @ height of contraction

Front 17

What are late decelerations?

Back 17

Late/Type II are decreases in FHR that start at peak of contraction and greatest after peak; the decrease may only be 5bpm; these are thought to be d/t fetal compromise/poor placental blood flow

Front 18

What is the significance of late decels with normal beat to beat variability?

Back 18

Pattern is associated with acute insults (i.e. maternal hypotension), with treatment this pattern can be reversed

Front 19

What is the significance of late decels with diminished beat to beat variability?

Back 19

Associated with prolonged fetal asphyxia, needs further testing

Front 20

What is the significance of late decels without beat to beat variability?

Back 20

Signifies SEVERE fetal decompensation, immediate delivery is indicated

Front 21

What are variable decelerations?

Back 21

Type III can occur any time during contraction, onset is abrupt, decel can last for prolonged time & can exceed 30bpm, thought to be d/t uterine induced umbilical cord compression; *Fetal asphyxia assoc with decels that last >60sec or decrease FHR by 70bpm and lasts >30 min = immediate delivery

Front 22

Urgent delivery is indicated by what FHR pattern?

Back 22

Prolonged decelerations without beat to beat variability, or FHR <70bpm

Front 23

What is measured by the fetal scalp monitor?

Back 23

Takes blood specimens to evaluate fetal acidosis; more direct measure of fetal status than FHR, pH<7.2 is abnormal

Front 24

How is the GI tract changed by pregnancy?

Back 24

Increased intragastric pressure, LES tone is decreased, barrier pressure is decreased; Full stomach after 12 weeks gestation=RSI

Front 25

How is the maternal airway changed by pregnancy?

Back 25

Capillary engormgement of resp. tract=edema of nasal & oral pharynx; **Failed intubation is leading cause of maternal death

Front 26

What are the most common causes of maternal mortality r/t pregnancy?

Back 26

Most-to-least: Hemorrhage, embolism, PIH, infection, cardiomyopathy, aneshtesia

Front 27

What is the greatest danger to the neonate delivered at 30 weeks gestation?

Back 27

immature lungs; extrauterine life possible @25 weeks; production surfactant @30 weeks-level sufficient by 34 weeks

Front 28

What is a tocolytic?

Back 28

Tocolytics suppress uterine contractility, Include: Beta2 agonist: ritodrine, terbutaline, Smooth muscle relaxant: magnesium sulfate

Front 29

List 4 side effects of beta agonist tocolytics:

Back 29

Hyperglycemia
Hypokalemia
Tachycardia
Possible Pulmonary edema

Front 30

Should atropine be given to patinets on beta agonist tocolytics?

Back 30

No, increased tachycardia can lead to increased risk of pulmonary edema

Front 31

What is the indication for an emergency c-section?

Back 31

Fetal distress as r/o: maternal hypotension, prolapsed fetal part, compromised fetal circulation, fetal trauma

Front 32

How much time do you have to start a c-section?

Back 32

ACOG says 30min

Front 33

Techniques for intrauterine resuscitation:

Back 33

relieve caval compression, maternal O2, maintain B/P, D/C oxytocin, IV terbutaline for tocolysis, saline amnioinfusion

Front 34

Anesthetic techniques for specific circumstances:

Back 34

Hemorrhage: GA
Uterine tetany: GA
Uterine rupture: GA or CLE
Fetal distress: SAB, CLE, GA
Prolapsed cord: GA, CLE

Front 35

How does chloroprocaine interact with opioids?

Back 35

Competes with opioids at the mu-receptor sites decreasing efficacy of the opioids

Front 36

What are 5 disadvantages of redosing an epidrual catheter with chloroprocaine?

Back 36

>20-25ml assoc with backache
Opioids efficacy decreased
Short acting-35-55min
Tachyphylaxis can develop

Front 37

What dose of ketamine produces excellent analgesia w/o depressing the neonate?

Back 37

0.2-0.5mg/kg IV

Front 38

How does one do a GA for c-section?

Back 38

Bicitra to raise gastric pH, position SLUD, pre-O2, RSI with CP, STP 3-5mg/kg, Anectine 1-1.5mg/kg or Zemuron; 50% N20, 0.5 MAC volatile agent (If patient on Magnesium Sulfate @ increased risk resp. depression so don't give priming dose)

Front 39

Why do parturients desaturate so rapidly during apnea?

Back 39

decreased FRC, increased O2 consumption

Front 40

Why would you use Ketamine instead of STP?

Back 40

Ketamine 1mg/kg induction if patient hypovolemic; >1mg/kg can compromise uterine tone = fetal distress; AVOID Ketamine in HTN/pre-eclamptic

Front 41

Why would a low dose of volatile agent be used during a c-section?

Back 41

ensures amnesia without excessively relaxing uterus; also pregnancy increases sensitivity to volatile agents

Front 42

What are the advantages of low doses volatile agents for the patient undergoing c-section?

Back 42

Decreases awareness, permits higher FIO2, may improve uterine blood flow; DOES NOT increase uterine bleeding or depress neonate

Front 43

How does pregnancy effect MAC?

Back 43

MAC is decreased 40%, increased sensitivity d/t increased progesterone & beta endorphin levels

Front 44

If the surgeon asks for a relaxed uterus what would you do?

Back 44

Increase volatile agent to 1.5-2MAC, NTG SL or IV

Front 45

Intubation fails, but you can ventilate & the fetus is NOT in distress, what do you do?

Back 45

Awaken pt, attempt awake intubation or regional

Front 46

Intubation fails, but you can ventilate, but the fetus is in DISTRESS, what would you do?

Back 46

Mask ventilate with cricoid pressure--NO LMA

Front 47

Intubation fails, the fetus is in distress, you can NOT ventilate-what would you do?

Back 47

Cricothyroidotomy or trach, deliver baby

Front 48

What does the Apgar Score evaluate?

Back 48

HR
Resp effort
Muscle tone
Reflex irritability
Color

Apgar @ 1min reflection of survival, @ 5min neuro status

Front 49

What is the appropriate drug for a neonate with an Apgar of 3 after 5 minutes?

Back 49

Sodium Bicarb, if resuscitation prolonged >5min and no ABG available

Front 50

What should be done for meconium aspiration?

Back 50

Mouth-bulb syringe
Below cords-intuabate & suction if baby NOT vigorous

Front 51

Who is responsible for resuscitation of the neonate?

Back 51

ASA states someone other than anesthetist that is attending to mother

Front 52

Neonatal resuscitation:

Back 52

consider gestational age, open airway, warm patient; evaluate resp, HR-give PPV is apneic or HR <100; HR<60 chest compressions, consider epinephrine or narcan