Labor, Vaginal & Cesarean Delivery Flashcards
What are the three stages of labor?
- Beginning of regular contractions to full cervical dilation (10 cm)
subdivided into latent phase (dilation to 2-3cm), and
active phase (up to 10cm) - Full cervical dilation to delivery of the fetus
- Delivery of the placenta
What is a laboring mother always considered?
A full stomach! Always RSI
According to the ASA guidelines, a healthy mother may:
1) drink a moderate amount of clear liquids throughout labor, and, 2) eat solid food up until the point a neuraxial block is placed
*The mother is NPO if surgery and general anesthesia is to be utilized
Does an epidural prolong the first stage of labor?
No
Does an epidural increase the need for a c-section
No
What can be given to help labor progress?
Oxytocin
Oxytocin is released from the posterior pituitary and helps contractions
The perineum is innervated by the ____ nerve
pudendal nerve (s2-s4)
Which block is not appropriate for the first stage of labor?
the pudendal nerve (s2-s4)
What needs to be anesthetized during the second stage of labor (the uterus is still contracting)?
T10-S4
The first stage of labor pain originates from _____ and the second stage of labor originates from _____.
The first stage of labor pain originates from T10 - L1 and the second stage of labor originates from T10 - S4.
What are the analgesic options for the first and second stages of labor?
1st stage: neuraxial blockade, paravertebral lumbar sympathetic block, and paracervical block
2nd stage: neuraxial blockade and a pudendal nerve block
What has made a comeback for a non-invasive alternative for labor anesthesia?
nitrous oxide…self administered 50% nitrous, 50% oxygen
What is the CSE technique, and what does the dual benefit provide?
Combined spinal-epidural technique, and it provides the ability to prolong the duration of anesthesia with an indwelling epidural catheter. It is particularly useful in labor and delivery
Labor pain in stage 1
1st stage: pain begins in the lower uterine segment and the cervix
pain signals to the T10-L1 posterior nerve roots
Labor pain in stage 2
adds in pain (existing pain in the lower uterine segment and cervix) from the vagina, perineum, and pelvic floor
pain impulses travel from the perineum to the s2-s4 posterior nerve roots
neuraxial procedure that covers T10-L1 during the 1st stage must be extended to cover S2-S4 during the 2nd stage of labor (total coverage = T10-S4)
Describe pain in the 1st stage of labor
Visceral C-fibers, hypogastric plexus
T10-L1, dull, diffuse, cramping
neuraxial, paravertebral, paracervical
Describe pain in the 2nd stage of labor
pudendal nerve
S2-S4
Sharp, well localized
neuraxial, pudendal nerve block
What are the consequences of uncontrolled pain?
increased maternal catecholamines (htn and reduced uterine flow)
hyperventilation - left shit of oxyhgb curve (reduced oxygen to fetus)
Why is nitrous oxide so great?
when given alone (not with opioids, it is NOT associated with hypoxia, loss of airway reflexes, or unconsciousness
Also preserves uterine contractility and does not cause neonatal depression
What is the most common approach to the combined CSE approach
the “needle-through” approach
What is the epidural extension technique?
the injection of saline into the epidural space immediately after the local anesthetic is administered into the subarachnoid space
Does hypnosis help labor pain?
15% are easy to hypnotize, 15% are impossible
may be of some benefit in labor but not useful by itself
psycho-prophylaxis (lamaze)
involves breathing and eye focus, commonly combined with other forms of analgesia
acupuncture
opioid peptide release has been demonstrated and maybe the gate control theory. Aims at correcting energy flow imbalances
Parenteral Analgesic Techniques
Problems:
Nearly all opioids cross the placenta and depress the fetus.
Loss of beat-to-beat variability and decreased movement complicate evaluation.
Problems with parenteral analgesic techniques
Routes:
IM and SC are not often used because of delayed onset.
IV offers easier titration and rapid onset and PCA options.
PCA advantages include better satisfaction scores, less neonatal depression, less nausea, and less risk of maternal respiratory depression.
What is the best parenteral analgesic technique?
PCA advantages include better satisfaction scores, less neonatal depression, less nausea, and less risk of maternal respiratory depression.
Which opioid is NOT used parenterally?
Morphine
Immature blood-brain barrier increases the risk of respiratory depression in the neonate.
Not often used for this reason.
Which parenteral analgesic techniques are used?
F-N-B
Fentanyl: Kinetics rapid transfer across the placenta.
Respiratory depression may outlast analgesia.
Nalbuphine (Nubain): Mu opioid antagonist, kappa agonist.
Has a ceiling effect on resp depression but no real large difference in side effects.
Dysphoria is common.
Used to treat opioid-induced pruritis (5-10 mg iv q 6 H prn).
Butorphanol (Stadol):
Some reports suggest a better analgesic profile than fentanyl.
Sedation is common.
Ceiling effect on resp depression.
Respiratory depression may outlast analgesia with ____, Dysphoria is common with _____, and ____ is common with is common with _____.
fentanyl, nalbuphine, sedation with butorphanol
Are volatile anesthetics used anymore in OB?
Rarely used anymore.
Dose limit 0.5 MAC.
Risks of pulmonary aspiration (gasses lower esophageal sphincter tone)
Decreased uterine tone is a side effect.
Nitrous used outside the US commonly.
Often used with supplemental nerve block.
What lumbar level is best to cover for obstetrics?
For obstetrics lumbar level is best to cover T-10 thru S4 dermatomes
In adults the spinal cord ends at the L1 level.
In 5% of patients it ends at L2/3, therefore spinals should be placed as low as possible and below L3.
If patient complains of paresthesia while spinal is being dosed, remove the needle.
Because the spinal cord ends at L2/L3 for 5% of adults, where is the best place to do a spinal?
below L3.
If patient complains of paresthesia while spinal is being dosed, remove the needle.
Where are most puncture sites actually done at?
L2-L3 (58%)
L3-L4 (38%
Where is an injection considered safe?
Where is Tuffier’s line?
Safe: below L2/L3
Tuffier’s line: L4/L5
What are the contraindications to neuraxial blockade?
Patient refusal
Infection at site of injection
Coagulopathy (anticoags, liver, thrombocyt..)
Intracranial mass legion
aortic stenosis
existing spinal/neuro pathology
hemodynamic instability
Epidural space on avg identified ____ cm deep
Epidural space on avg identified 4.75 cm deep
Loss of Resistance Technique can be with ____ or with ___. ______ is safer option 3-5 cm deep
Loss of Resistance Technique can be with saline or with air. Saline is safer option 3-5 cm deep
After space identified thread catheter until ____ of the tip lie in the epidural space
After space identified thread catheter until 5 cm of the tip lie in the epidural space
The difference between epidural and spinal block is one tissue layer (a few millimeters) but drugs delivered via spinal route are ___x more potent and much smaller needles are used
10X
Subarachnoid Blocks for Labor can consist of..
opioid alone or in combination with local anesthetic agent; (sufenta 5-10mcg or 15-20 mcg fentanyl +/- 2 mg bupivacaine.
Good for cases where delivery expected soon and not enough time available to place epidural.
Combination spinal epidural technique also used.
We will typically ask the height of the patient prior to placing the spinal and do 1.4-2ml of bupivacaine RARE to give 2ml.
Subdural block
Subdural space between the dura and arachnoid mater.
Variable presentation – minimal to LOC and apnea.
May involve cervical roots, cranial nerves, see trigeminal nerve block, Horner’s syndrome.
If detected – do NOT deliberately dose.
Replace catheter into epidural space.
Key points
20-30% less local is required for pregnant patients
Using a noncutting (pencil-point) needle for spinal reduces incidence of post-dural puncture headache
Dont care for pregnant women supine
Pregnant women have softer ligamentum flavum, accented lumbar lordosis, decreased spinal canal space
Esters
One “i’
plasma cholinesterase
metabolite PABA is a known allergen
Amides
Two “ii”
No PABA, rare to have allergic issues
metabolized by liver
Lipid solubility influences ____
Potency
Increasing lipid solubility enhances placental diffusion
Protein binding enhances _____
duration
High protein binding decreases placental transfer
AI - acid glycoprotein: high ____, low _____
Albumin: low____, high _____
AI - acid glycoprotein: high affinity, low capacity
Albumin: low capacity, high capacity
The speed of onset is determined by ______
pKa
pKa is the pH where 50% of LA is charged (polar) and 50% is uncharged (nonpolar)
The closer pKa is to physiologic pH, more LA is in nonpolar form and has a _____ onset
Faster
How do you artificially raise pH so you are closer to pKa?
add bicarb
What actually makes the local work once it crosses the membrane?
the polar molecule
Does warm LA reduce onset time?
Yes
Neuronal Morphology
Small and poorly myelinated neurons are more rapidly susceptible to blockade, e.g. type C fibers.
Larger myelinated fibers require higher LA concentration for blockade, e.g. type A fibers.
Typically a ‘differential blockade’ that prevents pain without eliminating awareness (pressure) of labor.
What drugs are commonly used in OB for labor epidurals?
Bupivacaine
Ropivacaine
Lidocaine
What drugs are commonly used in OB for operative epidural anesthesia?
Lidocaine
2-chloroprocaine
What drugs are commonly used in spinal anesthesia?
Tetracaine
Bupivacaine
Lidocaine
short duration (45 minutes)
Also used to activate epidural catheter for C-section (15-20 cc 2% lidocaine with epi)
For labor epidurals not used as a continuous infusion
Useful as a top up and to test function of epidural catheter
Lot of motor block (bad)
2-Chloroprocaine
Do not use in patients with atypical pseudocholinesterase.
The only ester local used in epidural space
Rapid onset, very short duration
Epidural 2-chloroprocaine will interfere with the analgesic effects of subsequently administered epidural fentanyl.
Bupivacaine
Long duration, less motor block than most other agents.
Produces refractory v-tach/v-fib if large IV dose given.
Bupivacaine analogs
Levobupivacaine: L-isomer of bupivacaine
Less cardiotoxic.
Recently put on the market
Ropivacaine
Less cardiotoxicity than even levo in animal studies.
May be about 25% less potent than bupivacaine.
Not approved for spinal (neither is levo).
Bupivacaine analogs
Levobupivacaine: L-isomer of bupivacaine
Less cardiotoxic.
Recently put on the market
Ropivacaine
Less cardiotoxicity than even levo in animal studies.
May be about 25% less potent than bupivacaine.
Not approved for spinal (neither is levo).
Epidural Drug Administration
Every dose is a test dose! Dose incrementally
Accidental IV injection can be detected early
Epinephrine test doses in obstetrics are controversial.
LAST symptoms
Tinnitus
Light-headedness
Metallic taste
Circumoral numbness
Convulsions
Loss of consciousness
Respiratory arrest
Increased PaCO2 and acidosis lower seizure threshold.
Acidosis decreases protein binding _ more free LA.
LAST treatment
20% Intralipid if refractory to standard resuscitation efforts
1.5 mL/kg as an initial bolus, followed by
0.25 mL/kg/min for 30-60 minutes
bolus can be repeated 1-2 times for persistent asystole
infusion rate can be increased if the BP declines
