#209 Obstetric Analgesia and Anesthesia Flashcards
Where do women feel first stage of labor pain?
Diffuse. Lower abdominal pain is nearly universal, significant % will experience lower back pain. May be referred to iliac crests, buttocks, or thighs.
As fetus descends in the first stage or second stage of labor, distention of the vagina, pelvic floor, and perineum elicit stimuli through what nerve(s)?
Pudendal nerve and the anterior primary divisions of sacral nerves S2 through S4
Which opioid used for labor analgesia has the shortest duration of action?
Remifentanil, 3-4 minutes
Which opioid used for labor analgesia has the most rapid onset of action?
Remifentanil, 20-90 seconds
next is nalbuphine 2-3min or fentanyl 2-4 min
Which opioid used for labor analgesia has the longest duration?
Butorphanol 4-6hrs
In general, how is the pain relief with parenteral opioids for labor analgesia?
Some pain relief, but poor, and associated with significant adverse events, mostly nausea, vomiting, drowsiness
True or false, opioids do not cross the placenta
False
How does opioid use affect fetus/neonate?
Loss of variability in FHR, reduction in FHR baseline, neonatal respiratory depression, or neurobehavioral changes
True or false, opioid drug elimination takes the same time in newborns as adults?
False, longer in newborns, particularly in administered near the time of delivery
Why is meperidine generally not recommended for peripartum analgesia?
Active metabolite (normeperidine) has a prolonged half life in adults and half life up to 72hrs in neonate; the effect cannot be antagonized by naloxone
What opioids during labor are associated with less respiratory depression (compared to other opioids)?
Mixed agonist-antagonists such as nalbuphine and butorphanol. Remifentanil due to easy titration.
What is a common risk of remifentanil PCA for labor analgesia?
Maternal apneic episodes (occur in 26% of women with PCA). Respiratory arrest has occurred.
What % of women in the US having a singleton birth in the US select epidural or spinal analgesia?
More then 60%
What level of education is associated with higher epidural use during labor? Race? Early or late presentation to prenatal care?
Higher education levels, white race, early presentation for prenatal care
Does neuraxial analgesia increase the cesarean delivery rate?
No
What medication(s) is placed through an epidural catheter?
Mix of local anesthetic and opioid medication; plus or minus epinephrine; plus or minus bicarb
What effect does a local anesthetic have in epidural space?
Motor blockade, labor pain relief
What are the commonly used local anesthetics for epidural anesthesia?
Bupivacaine and ropivacaine
What opioids are common used for epidural anesthesia?
fentanyl and sufentanil
What does addition of epinephrine to epidural block do?
prolong duration, increase reliability and intensity of block.
What does the addition of sodium bicarb to epidural block do?
Speed up onset of epidural blockade, intensify the effect, or both, especially in sacral dermatomes
What are methods of maintaining epidural anesthesia?
Intermittent boluses, continuous infusion or continuous infusion with patient-administered boluses
How does intermittent bolus technique for epidural compare to continuous infusion?
No difference in total duration of labor. Significantly shorter second stage, less total anesthetic drug, higher maternal satisfaction
Is epidural or opioids better for controlling labor pains?
Epidural
What medication(s) is put into spinal block?
Mix of local anesthetic and opioid
What anesthetics are used for spinal block?
Lidocaine, bupivacaines, ropivacaine
What opioid(s) is used for spinal block?
Fentanyl, sufentanil, or morphine
What is the concern about continuous spinal analgesia for labor?
Concerns about postdural puncture headache.
Caution with labeling, use, dosage, and sterility on intrathecal catheter
What is a downside of combined spinal-epidural anesthesia?
Epidural catheter placement cannot truly be verified until the spinal component has “worn-off”
How does intrathecal opioids lead to fetal bradycardia?
Independent of maternal hypotension. Hypothesized that fast pain relief, lowers maternal plasma epinephrine and beta-endophines, leaving oxytocin and norepinephrine unopposed, which leads to uterine hypertonus and reduction in ureteroplacental blood flow
What is the landmark for pudendal block?
Ischial spine
When is a pudendal block useful?
Second stage of labor or after delivery to facilitate repair of perineal lacerations
What is maximum recommended bupivacaine dosing w/ and w/o epi?
3mg/kg for both
What is the maximum recommended lidocaine w/ and w/o epi?
7mg/kg w/.
5mg/kg w/o.
What is recommended maximum dose of ropivacaine w/ and w/o epi?
2mg/kg for both
What is the recommended maximum dose of 2-chloroprocaine w/ and w/o epi?
14mg/kg w/.
11 mg/kg w/o.
What are possible symptoms of local anesthetic toxicity (eg from injecting into blood stream)?
Neurologic symptoms (eg, seizures, coma) or cardiac symptoms (eg, arrhythmias, myocardial depression)
Do CNS or cardiac manifestations of local anesthetic toxicity typically manifest first?
CNS symptoms
What is the interaction between hypoxemia and acidosis with local anesthetic systemic toxicity? What should you do?
Hypoxemia and acidosis potentiate local anesthetic systemic toxicity. Treat with IV lipid emulsion
What logistics need to be in place to give nitrous oxide during labor?
Need supply with apparatus that must use a demand valve. Must have scavenging equipment.
How does analgesia from nitrous oxide compare to epidural?
Not as good as epidural in regards to pain scores
What are maternal adverse effects of nitrous oxide use?
Nausea, vomiting, dizziness, and drowsiness
When nitrous oxide is used for labor analgesia, is it cleared quickly or slowly from the neonate?
Eliminated rapidly by the neonate after he or she begins to breathe
Can nitrous oxide be used safely with other forms of analgesia for labor pain?
Yes
What is the role of general anesthesia in labor and delivery?
Typically limited to emergency cesarean deliveries or scenarios in which neuraxial anesthesia cannot be performed or has already failed
Do anesthestic needs change before and after delivery of the newborn during general anesthesia?
Yes
What anesthetics used for general anesthesia can cause decreased uterine tone?
Inhaled volatile agents, eg sevoflurane or isoflurane. Typically these will need to be maintained with low concentrations.
What is the rate of failed intubations among pregnant patients compared to nonpregnant surgical patients?
Pregnant: 1 in 224 to 1 in 390
Nonpregnant: 1 in 2230
What is the failure rate of neuraxial anesthesia for cesarean delivery?
1.7%
The Serious Complication Repository Project was created to estimate the frequency of severe adverse outcomes associated with obstetric anesthesia. How many out of 300,000 recorded cases had events?
- 2 cardiac arrests, 2 myocardial infarctions, 4 epidural abscess or meningitis (<1:60,000), 1 epidural hematoma (1:250,000), 10 failued intubations, 58 high neuraxial blocks. 7 neurologic injuries. 16 respiratory arrests.
Are epidural or spinal blocks at higher risk for high neuraxial blocks?
Nearly equally distributed
What puts a patient at risk for a high neuraxial block?
Unrecognized spinal catheter. Attributed to 24% of cases high neuraxial blocks
What is the rate of postdural puncture headache after spinal or combined spinal-epidural anesthesia?
0.7%
What is the standard therapeutic intervention for a postdural puncture headache?
Epidural blood patch
Are epidural or intrathecal opioids more likely to lead to pruritis?
Intrathecal
What are minor maternal adverse effects associated with neuraxial blocks?
Maternal hypotension, pruritis, nausea/vomiting. Temperature elevation or fever (epidural related), shivering, urinary retention, and reactivation of oral herpes, respiratory distress.
What are treatment options for opioid-induced pruritis (centrally induced)?
Small doses of naloxone or nalbuphine (but these can reverse some of the analgesic effect). Antihistamines, but these have little to no effect on centrally-induced pruritis, but may increase drowsiness, leading to improvement in symptoms
What % of women will develop hypotension from low-dose neuraxial labor analgesia?
About 10%
What can be done to help prevent maternal hypotension with neuraxial anesthesia?
Preloading or coloading with crystalloid or by administering small doses of vasopressors (ephedrine or phenylephrine)
Is the risk of spinal or epidural hematoma higher with spinal or epidural?
Epidural
What is the risk of spinal-epidural hematoma in patient with platelets between 70k-100k?
0-0.6%
Can epidural/spinal anesthesia be used in patients with platelets <70k?
It may be acceptable in some circumstances. There is insufficient data to assess risk in patients with platelets <70k
What is the risk of serious morbidity from general anesthesia during a cesarean delivery?
6.5%
Is use of low-dose aspirin a contraindication for neuraxial techniques?
No
Is the presence of a space-occupying brain lesion a contraindication to epidural anesthesia?
Not necessarily. If it does not result in increased ICP (no mass effect, hydrocephalus), risk of herniation is minimal and epidural anesthesia can be considered
What % of women will experience an increase in maternal temperature (>99.5oF) with neuraxial analgesia?
30%
What makes a woman more likely to have an increased temperature with epidural anesthesia?
Nulliparity. Prolonged use of epidural.
Does giving prophylactic antibiotics prior to epidural placement reduce the risk of developing fever?
No
How does intrathecal opioids vs systemic opioids affect the length of the first stage of labor?
90 minutes shorter in women with intrathecal opioids
How does epidural, compared to no epidural, affect length of second stage of labor?
Epidural prolongs the second stage of labor by a mean difference of 7.66 minutes without negative effects to fetus and neonate
Does initiation of epidural anesthesia at any stage of labor increase the risk of cesarean delivery?
No
Does HELLP syndrome affect platelet number or quality?
Both. Consumption of platelets coupled with impaired platelet function
Can women breast feed after general anesthesia?
Yes, as soon as they are awake, stable, and alert
How does maternal opioid use affect infants?
Can cause neonatal depression or drowsiness and can interfere with suckling
What is the dermatone level goal for a cesarean section?
T4
What anesthesia options are available if a woman needs an emergent cesarean section?
If epidural in place can titrate this in ~10mins.
Place spinal (~8 min).
General anesthesia (~2 min)
Local anesthetic
If patient is feeling pain during cesarean section, what can you do as a surgeon to improve tolerability?
Gentle tissue handling.
Do not exteriorize the uterus (requires higher sensory level than in situ repair)
What are the pros and cons of preservative-free morphine used in spinal or epidural anesthesia for cesarean section?
Provides 12-24hrs of post op analgesia.
Risks of pruritus, nausea, respiratory depression
Does wound infiltration with local anesthetic at the time of cesarean delivery decrease post op opioid consumption?
Yes, during first 12-24hrs
How does transversus abdominis plane blocks affect post op opioid use after cesarean section?
Decrease post op morphine requirements by more than 70%. However, do not improve pain relief when intrathecal morphine is given.
What particular opioid is not recommended for breastfeeding mothers?
Codeine
Oxycodone greater than how many miligrams per day is not recommended for breastfeeding women?
30mg/day
How long after SQH 5000u BID injection can neuraxial catheter be placed or removed?
More than 4-6 hours since last dose
How long after intermediate-dose unfractionated heparin (7.5-10k u) can neuraxial catheter be placed or removed?
More than 12 hours
How long after high-dose unfractionated heparin (>20k u/day) can neuraxial catheter be placed or removed?
More than 24 hours with aptt in normal range or anti-factor Xa level undetectable
After how many days of heparin use, should a platelet count be checked prior to placement or removal of neuraxial catheter to check for possible heparin-induced thrombocytopenia?
If taking for more than 4 days
How soon after neuraxial catheter removal can you resume unfractionated heparin?
Resumed more than 1 hour after catheter removal
How long after prophylactic LMW heparin administration should you wait for neuraxial needle or catheter placement or removal?
Delay by at least 12 hours after last dose
How long after therapeutic LMW heparin administration should you wait for neuraxial needle or catheter placement or removal?
24 hour delay
How long after neuraxial catheter removal can you resume thrombopropylaxis with LMW heparin?
Resume more than 4 hours after catheter removal
Does neuraxial analgesia increase the cesarean delivery rate?
No
