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5th Quarter > OB Exam #2 > Flashcards

OB Exam #2 Flashcards

1
Q

Characteristics of IV Analgesia for Parturient.

A
  • Can be used when neuraxial not an option, refused, or contraindicated…though less effective
  • Relief is often inadequate: both fetal and maternal resp depression, N&V, and decreased lower esophageal sphincter tone may result
  • Opioids are LIPID soluble and small (
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2
Q

Which group has higher patient satisfaction and pain ratings: neuraxial or IV analgesia during labor?

A

-Neuraxial MUCH better control

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3
Q

Characteristics of Meperidine:

A
  • Crosses placenta easily
  • Recovered from fetus within 2 min. of IV admin
  • NORMEPERIDINE: an active metabolite with an elimination 1/2 life of 30 hours; remains in neonate for days after delivery
  • Effective in reducing shivering during neuraxial anesthesia
  • drug to delivery interval of 2-3 hrs results in greatest neonatal depression (GIVE EARLY: 4 hrs before delivery)
  • Unique: has both narcotic AND local anesthetic properties
  • Because of differences in pH and protein binding, the level of meperidine in the fetus is likely to be HIGHER than the maternal blood level
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4
Q

Which opioid causes LEAST amount of neonatal respiratory depression: methadone, meperidine, or morphine?

A

-Meperidine

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5
Q

What can be used to reverse (or antagonize) meperidine and normeperidine?

A

-Naloxone

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6
Q

Characteristics of Fentanyl(PCA bolus dose, lockout, 4 hour limit):

A
  • Highly potent
  • Highly lipid soluble
  • Detected in fetal circulation after 1 min of IV admin
  • Depressant effects, including a reduction in beat-to-beat variability, can be seen
  • Dosages: 25-100 mcg in hourly increments
  • PCA bolus: 25-50 mcg
  • PCA lockout interval: 3-6 min
  • PCA 4 hour limit: 1-1.5 mg
  • Maternal respiratory depression outlasts analgesia
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7
Q

Characteristics of Morphine:

A

Morphine. NO LONGER widely accepted in L&D:

  • maternal sedation
  • neonatal depression
  • undesirable prolonged duration

**easily crosses the placenta and fetal BBB more readily than in adults (animal studies)

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8
Q

Characteristics of Butorphanol (Stadol):

A
  • Opioid agonist-antagonist
  • Dose: 1-2 mg IV or IM
  • 5 x more potent than morphine with a 1/2 life of 3 hrs
  • Effective for pain with NO cumulative respiratory depression “ceiling effect”
  • NO active metabolites
  • Caution in opioid-dependent (because this compound possesses significant antagonist properties)
  • Unlike morphine, it increases pulmonary artery pressure and myocardial work
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9
Q

Characteristics of Nalbuphine (Nubain):

A
  • Opioid agonist-antagonist
  • Dose: 5-10 mg IV, IM, or SC
  • Equivalent to 10 mg morphine
  • Effective for pain with NO respiratory depression “ceiling effect”
  • Caution in opioid dependent (because this compound possesses significant antagonist properties)
  • Results in greater reduction in FHR variability compared to meperidine
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10
Q

Characteristics of Remifentanil:(PCA bolus dose, lockout, 4 hour limit and basal rate?)

A
  • Ultra-short-acting opioid receptor agonist
  • Hydrolyzed by plama esterases to INactive metabolite
  • 1/2 life: 3.2 min (regardless of admin times)
  • Labor relief = mild to moderate
  • PCA bolus: 0.25 mcg/kg
  • PCA lockout: 2 min
  • PCA 4 hr limit: 3 mg
  • PCA/basal rate: 0.025-0.05 mcg/kg/min
  • Crosses placenta readily, though it is similarly rapidly redistributed and metabolized by the fetus
  • Greatest reduction of pain control by laboring parturients (of all opioids), though substandard to neuraxial anesthesia
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11
Q

Characteristics of Ketamine:

A
  • Derivative of phencyclidine and produces dissociative anesthetic effects
  • High lipid soluble, crosses placenta easily, no fetal issues if dose 1mg/kg) doses have been associated with uterine hypertonus, neonatal resp. depression, muscular hypertonicity, and lower Apgar scores…this dose may be desirable for emergent c/s where mother is hypovolemic
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12
Q

Characteristics of Benzodiazepines:

A
  • Strong potential to cause neonatal depression
  • Amnestic
  • Many possible risks to fetus when given to pregnant women
  • Onset of teratogenic effects may be immediate or delayed
  • Possible effects include abortion, malformation, intrauterine growth retardation, functional deficits, carcinogenesis, and mutagenesis
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13
Q

Can NSAIDS be used in the maternal patient?

A
  • NOT recommended due to suppression of uterine contractions
  • Promotes premature closure of fetal ductus arteriosus
  • Ketorolac (toradol)
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14
Q

Neuraxial Analgesia for Labor and Vaginal Delivery

A

Common neuraxial anesthetics include:

  • Epidural
  • Combined spinal-epidural (CSE)
  • Spinal
  • *Currently the best method of pain relief for L&D**
  • Complete relief from labor pain with minimal depression of parturient or fetus
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15
Q

Absolute Contraindications to Neuraxial Anesthesia.

A
  • Pt. refuses
  • Uncorrected severe hypovolemia
  • Uncorrected Coagulopathy
  • Increased intracranial pressure
  • Infection at insertion site
  • Untreated bacteremia
  • Severe stenotic valvular heart lesions
  • Documented allergy to local anesthetic
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16
Q

Relative Contraindications to Neuraxial Anesthesia.

A
  • Stable pre-existing neurologic disease: multiple sclerosis, peripheral neuropathy
  • Chronic severe headaches (cephalgias)
  • Chronic back pain
  • Previous major spinal surgery (harrington rods)
  • Poorly controlled chronic HTN

**these pts should undergo careful preanesthetic evaluation and consultation that takes into consideration the risk:benefit of the proposed procedure!

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17
Q

What is the platelet count at which a neuraxial anesthetic could be safely administered?

A
  • Above 80-100K
  • Perform thorough history:
  • S&S of coagulopathy
  • herbal supplements
  • plt. trends
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18
Q

Conditions that require Anticoagulation in the obstetric population.

A
  • Deep vein thrombosis
  • Antiphospholipid antibody syndrome
  • Factor V Leiden Mutations
  • Protein S deficiencies
  • Protein C deficiencies
  • *Potentially catastrophic complication of epidural hematoma:
  • results from uncontrolled bleeding in the non-distendable epidural space
  • if untreated: can cause ischemic injury to the cord resulting in persistent neurologic dysfunction
  • epidural hematoma: rare… 1 out of 150,000 epidural and 1 in 220,000 spinal anesthetics
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19
Q

Procedural Preop

A

H&P:

  • obtain early
  • any issues with pregnancy, previous pregnancies, deliveries, or anesthetics
  • document maternal VS and fetal condition: dilation, effacement, station, FHR, membrane status, and variability, gestational age and gravidity/parity

Obtain informed consent:

  • minor/emancipated?
  • minors who are free of parental care, control, or custody
  • minor is married
  • member of the military
  • high school graduate
  • know STATE LAWS!

Epidural Cart:

  • ER equip and drugs/20% intralipid/defib
  • O2, suction, emergency drugs (atropine, succs, ephedrine, epinephrine, calcium chloride to treat mag overdose, sodium bicarb…)
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20
Q

Local Anesthetics: Bupivicaine.

A

***Most commonly used local anesthetic in OB anesthesia!

  • Amino-amide
  • Relatively long duration of action
  • Ability to produce a differential block whereby sensory fibers are blocked more readily than motor fibers
  • Sensory > motor
  • Less tachyphylaxis c/t Lidocaine
  • In lower doses, it has limited placental transfer as well as minimal neonatal effects
  • Refractory cardiac arrest with inadvertent IV bolus
  • 0.75% Marcaine is no longer approved by FDA for EPIDURAL use despite a vial’s suggestion

Clinical technique to reduce incidence of cardiac toxicity:
-fractional dosing (

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21
Q

Local Anesthetics: Lidocaine.

A
  • Amino-amide
  • Rapid onset and intermediate duration of action
  • Dense motor block in epidural space when combined with epi
  • Great for C/S
  • Not great for laboring vaginal deliveries d/t motor block
  • In subarachnoid space: potentially neurotoxic with use of continuous small-bore catheters
  • NO lido in subarachnoid space
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22
Q

Local Anesthetics: Chloroprocaine.

A
  • Plasma 1/2 life: 21 sec in maternal blood and 43 sec in fetal blood
  • Amino-ester
  • Rapid onset and brief duration of action
  • Used primarily in OB to rapidly produce a surgical block in the presence of a preexisting epidural in the case of an emergency C/S
  • Metabolized by ester hydrolysis (pseudocholinesterase)
  • Low potential to produce cardiac and CNS toxicity after inadvertent IV admin
  • Crosses the placenta the LEAST
  • Epidurally administered: Has been shown to reduce effectiveness of subsequently administered epidural morphine, possibly by antagonism at the opioid receptors
  • Neurotoxicity has been reported after inadvertent spinal admin of large doses intended for epidural space, but was likely a result of the low pH and/or preservatives
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23
Q

Local Anesthetics: Ropivacaine

A
  • Amino-amide
  • Pure levorotatory enantiomer
  • Propyl group attached to the pipechol ring as opposed to bupivacaine which has a butyl group attached to the ring
  • 60-75% as potent as Bupivacaine
  • Reduced motor block compared to other LA
  • Developed largely to address the cardiac toxicity associated with Bupivacaine
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24
Q

What is Minimum local anesthetic concentration (MLAC)?

A
  • Concentration that produces an effective response in 50% of subjects
  • ropivacaine: 60-75% less potent as bupivacaine
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25
Q

Epidural Placement.

A
  • Aseptic Technique: chlorhexadine (best choice!), betadine
  • NIBP (check q 2 min for 15 min, q 5min for 15 min, enabling early detection and treatment of neuraxial anesthesia-induced hypotension) and Pulse ox
  • Stick around initially
  • Sitting vs. Lateral
  • Practice BOTH positions: fetal head entrapment, prolapsed umbilical cord, footling breech
  • U/S useful for depth midline, and interspace
  • Multiple catheter types
  • Volume loading??
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26
Q

T or F: Failure rate of epidural anesthetics is greater in the obese patient.

A
  • True
  • However, neuraxial anesthetics are desirable in obese pts. bc of the increased C/S rates and concern for potentially difficult airway
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27
Q

T or F: The type of epidural catheter used influences the anesthetic.

A
  • True
  • Spiral wire-embedded flexible polyurethane catheters with a soft tip have been shown to result in fewer paresthesias and IV placements when compared with nylon catheters
  • Advantage favoring multiple-orifice catheters
  • Multiple-orifice closed-end catheters are less prone to obstruction and likely result in better spread of local anesthetic in the epidural space
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28
Q

Epidural Test Doses

A

Why??:

  • Essential to aspirate for Blood or CSF after placement of epidural cath and before each subsequent manually administered dose
  • Negative aspiration does not, however, conclusively indicate that the catheter is not in the subarachnoid or IV space
  • Test dose designed to reveal inadvertent subarachnoid or IV injection of LA without producing systemic toxicity or widespread subarachnoid block
  • Key: test dose as the minimum amount of drug required to produce a modestly detectable effect either intrathecally or systemically
  • Overall volume has little to do with effectiveness
  • Test Dose: 3 ml of lidocaine 1.5% with epi 1:200,000
  • This 45 mg dose of lido, if unexpectedly admin in the subarachnoid space, will produce a noticeable but manageable, spinal anesthetic within 3-5 min while having no appreciable effect when given in the epidural space
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29
Q

T or F: Epi remains the most widely used and studied test dose marker, but its reliability is impaired in the face of beta-blockade, anesthesia, advanced age, and active labor.

A

-True

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30
Q

Lidocaine 45 mg with 15 mcg IV Epi admin S&S.

A
  • Modest systemic toxicity
  • Circumoral numbness
  • Lightheadedness
  • Auditory changes
  • Increase HR (lacks sensitivity and specificity…laboring women already have variable HR increases with contractions
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31
Q

Anesthetic Effects on the Progress of Labor.

A
  • Controversy: do neuraxial anesthetics prolong labor OR increase the need for assisted or operative delivery?
  • epidural pts decreased use of instrumented vaginal delivery and C/S with superior pain control
  • Use of epidural does NOT increase risk of C/S OR prolong labor
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32
Q

Epidural Analgesia for Labor.

A
  • Dosing 4 labor NOT C/S
  • Volume vs. Concentration
  • Opioid added
  • Insertion site: L2-L3
  • 1st stage labor dermatomes: T10-L1
  • Must extend block to S2-S4 for 2nd stage
  • Balance analgesia vs. motor block
  • Use of Epi is controversial (the more lipid soluble the LA, the less effect epi has)
  • Stick around for 20 min
  • Aortocaval syndrome
  • Communicate: OB nurses make or break you
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33
Q

How do you produce a segmental epidural block of varying density that can be adapted to the pt’s requirements?

A
  • By changing the volume and concentration of local anesthetic administered
  • Dosing with dilute concentrations: results in labor analgesia without producing significant motor block
  • Dosing with larger volume of a more concentrated LA: can convert to a surgical anesthetic
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34
Q

What is the effect combining a lipid-soluble opioid to the local anesthetic?

A
  • Decreases the concentration of LA without compromising analgesia
  • Preserves motor function
  • Decreases the dose of both drugs
  • Minimizes the potential complications and side effects of each
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35
Q

Maintaining Epidural Analgesia for Labor and Delivery.

A
  • Incremental boluses vs. Continous infusions
  • Infusions: less intervention, periods of pain, hypotension, use of LA and workload, more effective analgesia, no need for concern regarding risks of incremental boluses
  • Ideal block: effective analgesia for uterine contractions, dense analgesia of perineum for delivery, and little motor block
  • Shivering: occurs in 10% of all deliveries…20-70% of those parturients who receive neuraxial analgesia
  • Treatment: adding opioids to LA during dosing, IV meperidine, and warming of IV fluids
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36
Q

What are standard doses of LA’s that can be given during stage 2 of labor to supplement epidural infusion?

A

Injecting a relatively large 6-10 ml volume of:

  • Bupivacaine 0.25%
  • Lidocaine 1-2%
  • Chloroprocaine 2%

Fentanyl 50-100 mcg can be added to further enhance analgesia

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37
Q

Epidural Infusions for L&D.

A
  • Bupivacaine (0.025-0.125 %)
  • Ropivacaine (0.1-0.2%)
  • Fentanyl (1-3 mcg/ml)
  • Sufentanil (0.3-0.5 mcg/ml)
  • Rate: 8-15 ml/hr
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38
Q

Patient-Controlled Epidural Analgesia (PCEA)

A
  • Compared to continuous infusions, PCEA further reduces interventions, total drug dose, and lower extremity motor block without sacrificing analgesia
  • Increased maternal satisfaction due to enhanced control
  • Background infusions 2-10 ml/hr, bolus of 5-8 ml
  • Possibly reduces risk of infection
39
Q

Combined Spinal-Epidural (CSE).

A
  • Spinal has rapid onset
  • Epidural cath allows for prolongation of analgesia
  • Most utilize the “needle through the needle” technique
  • Spinal portion may be dosed with opioid alone or mixture:
  • Fentanyl: 15-25 mcg
  • Sufentanil: 10 mcg
  • Duration: 2 hrs NO motor blockade

-Initiate epidural infusion before spinal component resolves

40
Q

Characteristics of Spinal Analgesia

A
  • Single-shot spinal rarely suitable for labor due to its finite duration
  • Multiparous patients in advanced 2nd stage of labor
  • Those exhibiting poor control who can later have epidural
  • Those who have labored without anesthesia who now require an instrumental vaginal delivery
  • Those who have delivered without anesthesia who now require an extensive repair
  • Those in whom epidural space has been obliterated (surgically)
  • Rare cases: multiple single-shot spinal, placed q2-3 hrs
  • Option for high-risk parturients (macro-bore epidural catheter):
  • Morbidly obese
  • previous spinal surgery or deformity
  • Inadvertent dura puncture with epidural needle
  • After epidural attempts have failed
41
Q

Continous Spinal Anesthesia (CSA) dosing

A
  • Isobaric bupivacaine 0.25% in 0.5-1 ml increments for labor analgesia
  • Not a 1st line technique due to high risk of PDPH (risk may decrease after catheter is left in situ > 12 hours
  • All caregivers must be notified in order to prevent OD
  • Micro-Bore catheters associated with Cauda Equina Syndrome
  • Lidocaine associated with Transient Neurologic Syndrome (TNS)
42
Q

Regional Opioids for Labor Analgesia.

A
  • Combo of dilute LA with low-dose opioids:
  • reduces dose of both drugs
  • decreases motor block while preserving analgesia
  • minimizes side effects of both drugs
  • Intrathecal opioids are NOT effective for relieving pain during 2nd stage of labor
  • “Ceiling effect”
  • Side effects: respiratory depression, pruritis (MOST Common), urinary retention, N&V, constipation
  • IV antagonist (naloxone) or agonist-antagonist (nalbuphine) are effective at eliminating S/E while preserving analgesia
  • Neuraxial opioids are effective in reducing shivering associated with RA
43
Q

T or F: Local anesthetics work at the nerve axon while neuraxial opioids bind to receptors in the substantia gelatinosa within the dorsal horn of the spinal cord.

A
  • True
  • These receptors are stimulated by the admin of opioids via the subarachnoid or epidural routes
  • Epidurally admin. opioids are believed to be absorbed into the CSF and ultimately the spinal cord, to exert their action on spinal opioid receptors
44
Q

Neuraxial Opioids: Fentanyl

A

When used in combo with LA:

  • Epidural dose: 50-100 mcg
  • Intrathecal dose: 10-25 mcg
  • Excellent analgesia within 5-10 min
  • Duration of action: 60-140 min
  • If repeated q 90 min, does not affect APGAR scores
  • Compared to morphine, fentanyl has decreased cephalad migration
  • Fentanyl dose of 100 mcg is not detected in breast milk
  • Fentanyl much more lipid soluble than morphine, absorbed in neural tissue faster, faster onset/shorter duration than morphine
  • Fentanyl associated with lower incidence of CNS S/E
  • Resp. depression RARE
45
Q

Neuraxial Opioids: Sufentanil

A
  • Highly lipid soluble
  • Enhances receptor affinity: increased potency
  • Epidural injection: results in 98% of drug absorbed by epidural fat or into epidural veins…little reaches CSF
  • When injected into CSF: plasma levels are much lower
  • Shorter plasma 1/2 life than Fentanyl: less risk of accumulation
  • Intrathecal dose: 2.5-5 mcg
  • Epidural dose: 25-50 mcg
46
Q

Neuraxial Opioids: Morphine (Duramorph, Astramorph)

A
  • Compared to fentanyl and sufentanil, LIPID INSOLUBLE
  • Onset for epidural/spinal: 30-60 min
  • When used alone: high maternal dissatisfaction
  • POOR CHOICE for labor pain 2* to delayed onset
  • Well suited for post-op pain control 2* to C/S
  • Intrathecal dose: 0.1-0.25 mg
  • Epidural dose: 3-5 mg
  • Increased incidence of recurrent herpes simplex labials infection
47
Q

C-Section Facts.

A
  • Birth by C/S: > 30% of all deliveries
  • Risk of mom death: 16.7 x greater with GA when compared with regional anesthesia
  • Fetuses delivered of mom with left uterine displacement (LUD) have lower incidence of CNS depression and acidosis than those delivered of mothers in supine position
  • Blood loss normal C/S: 500-1000 ml
  • Normal amniotic fluid volume: 700 ml (300-1400 ml range)
48
Q

Neuraxial Anesthesia for C/S Facts.

A
  • T4 dermatomal level for adequate anesthesia
  • Hypotension: left untreated = fetal compromise
  • Minimize hypotension: LUD, IV fluids, vasopressors

Preop to prevent N&V and aspiration pneumonitis:

  • non-particulate antacid (30 ml BICITRA)
  • H2-receptor antagonist (Famotidine 20 mg)
  • GI motility adjunct (metoclopramide 10 mg)

-Antibiotics pre-incision: decrease surgical infection site infection from 6.4-2.5%

***Do not give anxiolytics: minimize fetal depression

-BP q 1 min for first 20 min

49
Q

Spinal Anesthesia for C/S.

A
  • Single shot spinal: most common technique
  • Simple
  • Rapid onset
  • Highly reliable block
  • Use of smaller volumes: yields less likelihood of administering toxic doses

***Drawbacks: fixed duration and rapid onset of sympathectomy with resultant hypotension

  • Hyperbaric Bupivacaine 0.75%: 13 mg is effective in 95% of patients (ED95)
  • Curvature of spine in supine position limits upward spread of hyperbaric solutions
  • Decreasing Bupivacaine dose: less hypotension but more pain, shorter duration, slower onset
  • Production of T4 block: hypotension 80% of time despite LUD
  • Crystalloid preload?? (studies show not effective, but coloading, giving at same time as neuraxial block, can be effective)
  • Hydroxyethylstarch 6%:
  • derivative of amylopectin
  • increase serum amylase~pancreatitis
  • Routine fluid loading NOT advocated for C/S in preeclampsia
  • Phenylephrine and Ephedrine: vasopressors of choice for maternal hypotension (hypotension after spinal is major risk for N&V)
50
Q

Hypotension treatment during neuraxial anesthesia for C/S: Ephedrine Sulfate

A
  • Synthetic
  • Nonselective, non-catecholamine, sympathomimetic drug
  • Causes direct beta and indirect alpha stimulation through the release of endogenous norepi
  • Dose: 5-10 mg IV bolus, MR q 5 min
  • May cross placenta and depress fetal acid-base status
51
Q

Hypotension treatment during neuraxial anesthesia for C/S: Phenylephrine

A
  • 1st line treatment of maternal hypotension
  • Direct acting alpha-1 adrenergic agonist
  • Vasoconstriction and increase PVR
  • Reflex bradycardia with subsequent decreased CO
  • Dose: 80-100 mcg boluses
52
Q

Addition of Opioids to Hyperbaric Neuraxial Anesthetics for C/S.

A
  • Intraoperative block quality can be significantly improved with addition of fentanyl (10-20 mcg) or sufentanil (2.5-5 mcg)
  • Onset: 5-10 min
  • Duration: 60-90 min
  • Preservative-Free Morphine (duramorph) 150 mcg
  • Used for longer-acting post C/S
  • Onset 60-90 min
  • Duration: 12-18 hrs
53
Q

After Delivery of Placenta during C/S.

A
  • Oxytocin given per obstetrician
  • Naturally occurring hormone
  • Synthesized in the supraoptic and paraventricular nuclei of the hypothalamus
  • Endogenous release occurs with stimulation of cervix, vagina, and breasts
  • Pitocin:
  • synthetic form of oxytocin
  • Dose: 20-40 IU dependint on amount of fluid remaining in IV bag
  • 1/2 life: 4-17 min
  • May cause water intoxication or uterine atony with prolonged infusions
  • 5 to 10 IU BOLUS of Pitocin:
  • 50% decrease in TPR and 30% decrease in MAP
  • 30% increase in HR and 30% increase in CO
54
Q

If Pitocin does not adequately stimulate uterine contractions, what is the 2nd line drug used?

A
  • Ergot Alkaloids
  • Methergine
  • Dose: 0.2 mg IM (thigh)
  • Potent vascular effects, do not give IV!! only IM
  • Increases BP, CVP, and PCWP
  • Absolute C/I in Preeclampsia!!!!
  • 1/2 life: 2 hours (uterine effects last much longer)

IV admin S/S:

  • arterial/venous constriction
  • coronary artery constriction
  • severe HTN
  • cerebral bleeding
  • H/A
  • N&V
55
Q

What is the 3rd line drug if pitocin and methergine do not work to stimulate uterine contractions?

A
  • Prostaglandin F2a
  • Carboprost or Hemabate
  • Dose: 250 mcg IM or directly into uterine muscle
  • Common S/E:
  • N&V
  • vomiting
  • diarrhea
  • bronchospasm
  • V/Q mismatch
  • fever

***Caution in asthmatics!!

56
Q

Summary: Spinal Anesthesia Technique for C/S.

A
  • Nonparticulate oral antacid no more than 1 hr prior to surgery
  • Admin and IV preload (colloid) or coload (crystalloid or colloid)
  • Apply standard monitors and record preprocedure vs
  • Record preprocedure FHT
  • Consider O2 admin
  • Perform lumbar puncture at L3-L4
  • sitting or lateral
  • small gauge (24 or 25) non-cutting needle (sprottle, Whitacre, Pencan)
  • Hyperbaric bupivacaine 15 mg in 8.25% dextrose (7.5-15 mg)…add fentanyl 20 mcg for intraop analgesia…add preservative-free morphine 150 mcg for postop analgesia
  • Supine position with LUD
  • Monitor BP q 1min at least until birth
  • Confirm block level (T4) prior to surgical start
  • Treat hypotension with phenylephrine; if maternal HR decreases below baseline or BP is not increased, use ephedrine
  • Admin. oxytocin as directed at delivery
57
Q

Epidural Anesthesia for C/S.

A
  • Not usually performed intraoperatively: due to time of onset
  • Usually converted to a C/S anesthetic from an epidural used for labor analgesia
  • Slower onset sympathectomy: easier to treat hypotension
  • After a negative test dose and careful aspiration for blood and CSF: inject 2% lido with epi 1:200,000 in 3-5 ml increments for total volume of 20-25 ml for T4 block
  • Duration: 90-120 min
  • NaHCO3 1 mEq/10 ml can be added to hasten onset
  • NaHCO3 should not be added to bupivacaine bc it precipitates when pH increases
  • Chloroprocaine:
  • another option with rapid onset
  • Duration: 45 min
  • Morphine?? (effects diminished after giving chloroprocaine)
  • Fentanyl: 100 mcg
  • Beware of the epidural catheter requiring multiple redoses!!!
  • Bc larger volumes of more concentrated LA are required to produce surgical anesthesia and unrecognized epidural cath movement into either the intrathecal or IV space is always possibile
58
Q

T or F: Commercially prepared Lidocaine with epi has a low pH in order to preserve the epinephrine.

A
  • True
  • The addition of NaHCO3 immediately prior to use increases the biologically active non-ionized fraction of drug
  • Combination results: 90-120 min of surgical anesthesia
59
Q

How much volume is required to raise the block level of a well-functioning labor analgesic epidural from T10 to the T4 surgical requirement?

A

-Give about 10-15 ml

60
Q

Epidural Anesthesia for C/S: Thoughts to Ponder.

A
  • High epidural: total sympathectomy
  • Beware of Horner’s Syndrome
  • Usually occurs after initial dose for C/S or “top-up” dose before vaginal delivery
  • Triad: miosis, ptosis, and enophthalmosis
  • Commonly: facial flushing, anhydrosis, and nasal stuffiness
61
Q

Combined Spinal-Epidural for C/S.

A
  • Lower spinal dose with less risk of hypotension
  • If procedure gets lengthy, epidural catheter allows for augmentation
  • Spinal injected first
  • If catheter insertion proves difficult, adequate block height may not be achieved
62
Q

Summary: Converting an Epidural in Use for Labor Analgesia to a C/S Anesthetic.

A
  • Admin nonparticulate oral antacid no more than 1 hour prior to surgery
  • D/C cont. epidural infusion
  • Admin and IV coload (crystalloid)
  • Apply standard monitors and record preprocedure vs and FHT
  • Consider O2 admin
  • Place in supine position with LUD
  • Carefully aspirate epidural cath for blood and CSF
  • Admin lidocaine 2% with epi 1:200,000 and NaHCO3 1 mEq/10 ml LA (total dose: 10-15 ml)
  • Admin 3 ml and observe maternal HR for 60 sec and level of block for 3-5 min
  • If no sign of subarachnoid or IV injection, admin 3-5 ml and observe for 3-5 min
  • Treat hypotension with phenylephrine; if maternal HR decreases below baseline or BP is not increased, use ephedrine
  • Confirm block level (T4) prior to surgical start
  • Admin 3-4 mg preservative-free morphine (0.5 mg/ml 6-8 ml) via epidural cath after cord is clamped for postop analgesia
  • Admin oxytocin as directed at delivery
63
Q

GA for C/S.

A
  • Allows better control of airway
  • Improved hemodynamic control
  • Urgent delivery without neuraxial anesthetic
  • Patient refusal
  • Coagulopathy
  • Prevention: early neuraxial placement and replacing suboptimal labor epidural catheters
64
Q

Difficult Airway.

A
  • Failure to intubate rate in OB patient: 1 in 250…8 x > than general population)
  • Leading cause of OB mortality
  • Soft-tissue edema in hypopharynx
  • Airway changes during labor
  • Breast enlargement with cephalic displacement of thorax sometimes require use of short-handled laryngoscope
  • Blind nasal intubation?? (increase bleeding)
  • If after 2 unsuccessful attempts and purely elective, WAKE UP THE PATIENT!!
65
Q

Induction for C/S.

A
  • RSI with cricoid pressure after denitrogenation and preoxygenation x 3 min
  • Healthy parturient: propofol 2-2.5 mg/kg
  • Severe airway disease: ketamine 1mg/kg
  • Hemodynamically unstable: etomidate 0.3 mg/kg
  • Induction should be delayed until ALL preparation for surgery is complete, and surgical staff indicates tehy are ready
  • Incision is delayed until ETT placement is confirmed
  • Minimize fetal exposure to depressant drugs
  • Sux 1-1.5 mg/kg
  • If sux contraindicated, may use Rocuronium 0.5-1 mg/kg
  • Reduces fasciculations
66
Q

Maintenance of Anesthesia for C/S

A
  • Volatile anesthetic + N2O: Goal of 0.8 MAC
  • UBF unchanged 0.5-1.5 MAC
  • At term MAC decreased 40%
  • Avoid Hyperventilation
  • Maintain maternal PaCO2 betw. 30-32 mmHg
  • PaCO2 3 min = increase fetal acidosis
67
Q

What is the most common side-effect of regional anesthesia

A

Hypotension

68
Q

Hypotension.

A
  • Most common S/E

- Defined: 20% drop from baseline or a SBP

69
Q

Treatment of Hypotension.

A
  • Prevention of aortocaval compression
  • LUD
  • IVF pre/coloading
  • Vasopressors
  • Apply O2
  • Monitor FHR continuously
70
Q

N&V

A
  • NOT uncommon during labor
  • Multifactorial causes:
  • delayed gastric emptying
  • opioid admin (IV not neuraxial)
  • exteriorization of uterus
  • motion during transport
  • unopposed GI vagal stimulation
71
Q

Treatment for N&V

A
  • Multimodal approaches combining antiemetics with different MOA: more effective than single mode treatment
  • Metoclopramide (prokinetic): 10 mg
  • Alcohol swab inhalation
  • Ondansetron (5HT3 antagonist): 4 mg
  • Scopolamine (anticholinergic): 1.5 mg transdermal patch
  • onset: 2-4 hrs
  • S/E: dry mouth, mydriasis, dizziness, potential amnesia
72
Q

Postdural Puncture Headache (PDPH).

A
  • CSF loss > CSF production
  • Decreased ICP with compensatory vasodilation
  • D/T loss of CSF from subarachnoid space
  • Total volume in subarachnoid space: 150 ml
  • 75 ml above foramen magnum
  • 75 ml below FM
  • Production is 0.35 ml/min or 500 ml/day
73
Q

PDPH Prevention.

A

-Use smaller diameter needle
-17 g Tuohy ~ 70% PDPH
-

74
Q

PDPH Conservative treatment.

A
  • Patients should be given options ranging from most conservative to most aggressive
  • Conservative: appropriate for mild H/A
  • BR
  • Hydration
  • Oral analgesics
  • Serotonin type 1 agonist (cerebral vasoconstriction): sumatriptan (25-100 mg PO)
  • Caffeine sodium benzoate (cerebral vasoconstrictor): 500mg-1 gm/liter of IVF
  • Epidural saline injection (50-100 ml)
75
Q

PDPH Aggressive treatment.

A
  • Pts unresponsive to conservative therapy for 24 hrs should receive Epidural Blood Patch
  • Aim for initial interspace or one level below
  • Ideal volume: 15-20 ml
  • MOA is 2-fold:
  • epidural defect is covered with fibrin clot
  • blood increases relative CSF volume
  • 1st EBP: >90% success rate
  • 2nd EBP: ~95% success rate
  • Prophylactic EBP not recommended
76
Q

Cause of PDPH.

A
  • CSF loss occurs through a hole in the dura made during the performance of a subarachnoid block or accidentally during the attempted performance of an epidural block
  • Bc the needle used to place an epidural cath has larger diameter (17-18 g) relative to spinal needles

**loss of CSF is not the only cause of headaches post-partem: tension/migraine/preeclampsia/eclampsia

77
Q

Seizures related to Local Anesthetics

A
  • During epidural anesthesia, seizures are due to:
  • inadvertent direct vascular injection into an epidural vein
  • accumulation from repeated dosing

-Seizures are not necessarily lethal, but the resultant anoxia and acidosis are

  • Prevention:
  • aspirate for blood prior to injection
  • use test dose
  • fraction dosing
  • vigilance for S/S of TOX!!
  • Position: supine > lateral
  • Catheter orifice: multiport > 1
  • Nylon > wire-embedded
  • Limiting catheter insertion depth to
78
Q

Systemic effect of lidocaine.

A

**Symptoms of LA toxicity are directly related to the serum concentration

  • Therapeutic: 0-3
  • Lightheadedness/tinnitus/circumoral and tongue numbness: 5
  • Visual disturbances: 5-10
  • Muscular twitching: 10-13
  • Convulsions: 13-15
  • Unconsciousness: 15-18
  • Coma: 18-22
  • CVS depression/Resp. arrest: 22 and above
79
Q

Seizures related to LA Toxicity.

A
  • Call for HELP!!
  • Bring crash cart with 20% intralipid emulsion
  • Hypoxemia and acidosis develop rapidly during convulsions
  • STOP convulsions: benzo, barb, and/or sux
  • 100% O2 (mask vs. ETT)
  • Monitor maternal vs. FHR
  • Supportive care/ACLS
  • Prevent maternal reps and metabolic acidosis
  • Delivery of fetus??
80
Q

Total Spinal Block

A

Causes:

  • Inadvertent injection of an epidural dose into the subarachnoid or subdural space
  • Migration of a previously placed epidural catheter into the subarachnoid or subdural space
  • Inadvertent overdose during a single-shot subarachnoid block
  • Single-shot subarachnoid block in hopes of rescuing a failed epidural
81
Q

S/S of Total Spinal Block

A
  • Rapid in onset and preceded by complaints of:
  • dyspnea
  • difficult phonation
  • hypotension
  • Followed by:
  • apnea
  • unconsciousness
82
Q

Clinical features of Epidural block.

A
  • Onset: Slow
  • Spread: As expected
  • Nature of Block: Segmental
  • Motor Block: minimal
  • Hypotension: less than spinal and depends on extent of block
83
Q

Clinical features of Subdural Block

A
  • Onset: Intermediate
  • Spread: Higher than expect, may extend intracranially but sacral sparing common
  • Nature of block: Patchy
  • Motor block: Minimal
  • Hypotension: Intermediate betw. spinal and epidural; depends on extent
84
Q

Clinical features of Subarachnoid Block.

A
  • Onset: Rapid
  • Spread: Higher than expect, may extend intracranially, sacral block present
  • Nature of block: Dense
  • Motor Block: Dense
  • Hypotension: Likely
85
Q

Accidental Subdural Injection.

A
  • Accidental catheter placement in subdural space
  • Betw. dura and arachnoid membranes
  • After negative test dose for IV and subarachnoid injection, LA is admin. through the supposed epidural cat in the normal fashion
  • After 10-25 min, a sudden excessive spread of the block is noted, primarily cephalad
  • Magnitude of the spread is significantly greater than would be anticipated if cath were in the epidural space, very similar to subarachnoid space
  • Hypotension caused by extensive sympathetic block: primary problem (treat with vasopressor, ephedrine)
  • Uncommon!!
86
Q

Management of Total Spinal Anesthesia.

A
  • High spinal may occur several minutes after an epidural dose
  • Communicate with patient: agitation, dyspnea, difficulty speaking may herald onset of TSA
  • Avoid aortocaval compression
  • Admin 100% O2
  • Provide PPV preferably through an ETT
  • Monitor maternal BP, EKG, and FHR continuously
  • Support maternal circulation with IVF, vasopressors
  • DO NOT HESITATE to give EPINEPHRINE
87
Q

CPR of the Parturient.

A
  • Problematic in near-term parturient
  • Mother has high O2 demand and a small O2 reservoir (residual volume)
  • Near-term uterus obstructs central venous return in the supine parturient
  • LUD increases success
  • When near-term parturient does not respond to resuscitative efforts within 5 min, STAT C/S is indicated!!
88
Q

Neurologic Injuries in OB Anesthesia.

A
  • Exceedingly Rare
  • Permanent: 1 in 240,000
  • Transient (
89
Q

What is the Most Common intrinsic obstetric palsy?

A
  • Lateral femoral neuropathy

- Palsies of the femoral, obturator, sciatic, common peroneal nerves and lumbosacral plexus have also been reported

90
Q

Meralgia Paresthetica

A
  • Commonly caused by a focal entrapment of lateral femoral cutaneous nerve while it passes the inguinal ligament
  • Common S/S:
  • Numbness of UPPER LATERAL THIGH AREA
  • Paresthesias

-Pregnancy, tight clothes, obesity, position of surgery and tumor in retroperitoneal space could be causes

91
Q

Obturator Nerve Palsy.

A
  • Compression of obturator nerve
  • Susceptible to compressive injury as it crosses the brim of the pelvis or within the obturator canal
  • Mother may complain of pain when the damage occurs, followed by weakness of hip adduction and internal rotation
  • Sensory disturbance over the UPPER INNER THIGH
92
Q

Femoral Nerve Palsy.

A
  • More commonly diagnosed
  • 1/3 postpartum palsies
  • Femoral nerve is vulnerable to stretch injury as it passes beneath the inguinal ligament
  • Damage may result from:
  • prolonged flexion
  • abduction
  • external rotation of the hips during 2nd stage labor
  • following procedures conducted in an excessive lithotomy position

**Hips should never remain continuously flexed during the 2nd stage labor

  • In a true femoral neuropathy, nerve supply to the iliopsoas muscle is spared
  • Some hip flexion is still possible
  • The patient may walk ok on a level surface, but may be unable to climb stairs
  • Patellar reflex is diminished or absent
93
Q

Peroneal Nerve Palsy.

A
  • Vulnerable to compression as it passes around the head of the fibula below the knee
  • Also, as it leaves the pelvis
  • Peroneal nerve palsy may be caused by:
  • prolonged squatting (popular in natural childbirth)
  • excessive knee flexion for any reason
  • compression of the lateral side of knee against any hard object
  • prolonged use of the lithotomy position
  • When damaged at the knee, there is sensory impairment on the anterolateral calf and dorsum of the foot
  • Footdrop may be profound
  • Steppage gait and weak ankle eversion

(plantar flexion and inversion at ankle are preserved)

5th Quarter (11 decks)

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