OB Exam #2 Flashcards
(93 cards)
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 (
2
Q
Which group has higher patient satisfaction and pain ratings: neuraxial or IV analgesia during labor?
A
-Neuraxial MUCH better control
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
4
Q
Which opioid causes LEAST amount of neonatal respiratory depression: methadone, meperidine, or morphine?
A
-Meperidine
5
Q
What can be used to reverse (or antagonize) meperidine and normeperidine?
A
-Naloxone
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
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)
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
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
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
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
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
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)
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
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
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!
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
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
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…)
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 (
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
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
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
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
25
Epidural Placement.
- 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??
26
T or F: Failure rate of epidural anesthetics is greater in the obese patient.
- True
- However, neuraxial anesthetics are desirable in obese pts. bc of the increased C/S rates and concern for potentially difficult airway
27
T or F: The type of epidural catheter used influences the anesthetic.
- 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
28
Epidural Test Doses
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
29
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.
-True
30
Lidocaine 45 mg with 15 mcg IV Epi admin S&S.
- Modest systemic toxicity
- Circumoral numbness
- Lightheadedness
- Auditory changes
- Increase HR (lacks sensitivity and specificity...laboring women already have variable HR increases with contractions
31
Anesthetic Effects on the Progress of Labor.
- 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
32
Epidural Analgesia for Labor.
- 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
33
How do you produce a segmental epidural block of varying density that can be adapted to the pt's requirements?
- 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
34
What is the effect combining a lipid-soluble opioid to the local anesthetic?
- 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
35
Maintaining Epidural Analgesia for Labor and Delivery.
- 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
36
What are standard doses of LA's that can be given during stage 2 of labor to supplement epidural infusion?
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
37
Epidural Infusions for L&D.
- 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
38
Patient-Controlled Epidural Analgesia (PCEA)
- 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
Combined Spinal-Epidural (CSE).
- 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
Characteristics of Spinal Analgesia
- 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
Continous Spinal Anesthesia (CSA) dosing
- 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
Regional Opioids for Labor Analgesia.
- 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
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.
- 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
Neuraxial Opioids: Fentanyl
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
Neuraxial Opioids: Sufentanil
- 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
Neuraxial Opioids: Morphine (Duramorph, Astramorph)
- 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
C-Section Facts.
- 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
Neuraxial Anesthesia for C/S Facts.
- 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
Spinal Anesthesia for C/S.
- 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
Hypotension treatment during neuraxial anesthesia for C/S: Ephedrine Sulfate
- 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
Hypotension treatment during neuraxial anesthesia for C/S: Phenylephrine
- 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
Addition of Opioids to Hyperbaric Neuraxial Anesthetics for C/S.
- 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
After Delivery of Placenta during C/S.
- 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
If Pitocin does not adequately stimulate uterine contractions, what is the 2nd line drug used?
- 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
What is the 3rd line drug if pitocin and methergine do not work to stimulate uterine contractions?
- 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
Summary: Spinal Anesthesia Technique for C/S.
- 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
Epidural Anesthesia for C/S.
- 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
T or F: Commercially prepared Lidocaine with epi has a low pH in order to preserve the epinephrine.
- 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
How much volume is required to raise the block level of a well-functioning labor analgesic epidural from T10 to the T4 surgical requirement?
-Give about 10-15 ml
60
Epidural Anesthesia for C/S: Thoughts to Ponder.
- 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
Combined Spinal-Epidural for C/S.
- 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
Summary: Converting an Epidural in Use for Labor Analgesia to a C/S Anesthetic.
- 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
GA for C/S.
- 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
Difficult Airway.
- 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
Induction for C/S.
- 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
Maintenance of Anesthesia for C/S
- 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
What is the most common side-effect of regional anesthesia
Hypotension
68
Hypotension.
- Most common S/E
| - Defined: 20% drop from baseline or a SBP
69
Treatment of Hypotension.
- Prevention of aortocaval compression
- LUD
- IVF pre/coloading
- Vasopressors
- Apply O2
- Monitor FHR continuously
70
N&V
- NOT uncommon during labor
- Multifactorial causes:
* delayed gastric emptying
* opioid admin (IV not neuraxial)
* exteriorization of uterus
* motion during transport
* unopposed GI vagal stimulation
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Treatment for N&V
- 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
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Postdural Puncture Headache (PDPH).
- 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
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PDPH Prevention.
-Use smaller diameter needle
-17 g Tuohy ~ 70% PDPH
-
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PDPH Conservative treatment.
- 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)
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PDPH Aggressive treatment.
- 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
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Cause of PDPH.
- 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
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Seizures related to Local Anesthetics
- 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
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Systemic effect of lidocaine.
**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
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Seizures related to LA Toxicity.
- 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??
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Total Spinal Block
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
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S/S of Total Spinal Block
- Rapid in onset and preceded by complaints of:
* dyspnea
* difficult phonation
* hypotension
- Followed by:
* apnea
* unconsciousness
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Clinical features of Epidural block.
- Onset: Slow
- Spread: As expected
- Nature of Block: Segmental
- Motor Block: minimal
- Hypotension: less than spinal and depends on extent of block
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Clinical features of Subdural Block
- 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
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Clinical features of Subarachnoid Block.
- Onset: Rapid
- Spread: Higher than expect, may extend intracranially, sacral block present
- Nature of block: Dense
- Motor Block: Dense
- Hypotension: Likely
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Accidental Subdural Injection.
- 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!!
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Management of Total Spinal Anesthesia.
- 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
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CPR of the Parturient.
- 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!!
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Neurologic Injuries in OB Anesthesia.
- Exceedingly Rare
- Permanent: 1 in 240,000
- Transient (
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What is the Most Common intrinsic obstetric palsy?
- Lateral femoral neuropathy
| - Palsies of the femoral, obturator, sciatic, common peroneal nerves and lumbosacral plexus have also been reported
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Meralgia Paresthetica
- 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
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Obturator Nerve Palsy.
- 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
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Femoral Nerve Palsy.
- 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
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Peroneal Nerve Palsy.
- 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)
