Labor AnalgesiaKaty Kemnetz

Labor analgesia

“Labor causes severe pain for many women. There is no other circumstance where it is considered acceptable for an individual to

experience untreated severe pain, amenable to safe intervention, while under a physician's

care. In the absence of a medical contraindication, maternal request is a

sufficient medical indication for pain relief during labor.... None of the techniques appears

to be associated with an increased risk of cesarean delivery.”

-ACOG committee opinion 339

Patient education

A woman's satisfaction with her labor and delivery are less dependent on the amount of pain and more dependent on her involvement in the decision-making process

Obstetricians should educate their patients early in pregnancy about their options

Stages of labor

First stage– Visceral pain caused

by contractions, stretching of cervix and uterus, ischemia

– Fibers from uterine body and fundus enter spinal cord at T10-L1 with sympathetics

– Fibers from cervix and upper vagina enter cord at S2-S4 with parasympathetics

Second stage

– Add somatic pain from stretching of vaginal, perineum, and pelvic ligaments

– Travels to spinal cord in S2-S4 via pudendal nerve

Distribution/intensity of labor pain

T11/T12 dermatomes

T10/L1 dermatomes Perineum

Lower back and perineum

Adverse consequences of pain

Stress– Release of catecholamines can reduce

placental blood flow Hyperventilation

– Impaired transfer of oxygen to fetus• Impaired maternal hemoglobin

dissociation• Placental vasoconstriction

Psychological– PTSD and postpartum depression

Systemic labor analgesics

• Options– Opioids

• Morphine, fentanyl, meperidine, hydromorphone– Mixed opioid agonist-antagonists

• Nalbuphine, butorphanol• Dose ceiling effect for respiratory depression

– PCA• Cons• Less effective analgesia• Risk of respiratory depression, nausea, vomiting, sedation,

decrease in FHR variability• Pros• Result in shorter duration of labor and less oxytocin

augmentation

Local blocks• Pudendal block

– Somatic pain of stretching of vagina/cervix/perineum

– Ineffective for pain of contractions

• Para cervical block– Blocks some

uterine, cervical sensory fibers

– Somewhat effective for contractions

– ?Effect on fetus

Contraindications to neuraxial analgesia

• Patient refusal• Uncorrected coagulopathy• Infection of the lower back• Uncorrected hypovolemia• Increased intracranial pressure

Epidural analgesia

The epidural space is bounded anteriorly by the posterior longitudinal ligaments, laterally by the pedicles and intervertebral foramina, and posteriorly by the ligamentum flavum. Contents of the epidural space include the nerve roots that traverse it from foramina to peripheral locations, fat, areolar tissue, lymphatics, and blood vessels

Epidural anesthesia A catheter is placed in the

epidural space and left there for the duration of labor

Slower onset of anesthesia (5-10 minutes) but longer duration

Dosing regimens:• Intermittent dosing

• Breakthrough pain• Continuous infusion

• Increased risk of motor blockade

• PCEA• Lower total dose of

analgesics used during labor and lower incidence of motor block

•Usually an epidural includes a combination of opioid (fentanyl/ sufentanyl) and local anesthetic (bupivicaine/ ropivacaine)

•Ephinephrine and opioids reduce concentration of local anesthesia required

•A lower concentration of local anesthetic reduces the motor blockade (“walking epidural”)

Spinal and Combined Spinal-Epidural (CSE)

• Spinal analgesia has quicker onset (within 5 minutes) but shorter duration (90 minutes)– Catheter is not left in intrathecal space– More useful for planned c-section, less useful for

labor• Combined spinal epidural is best for quick onset

and long duration• Greater risk of pruritis, fetal bradycardia,

maternal hypotension with higher doses– Minimized by using lipophilic opioids like fentanyl

in intrathecal space– No change in rate of cesarean section

Second stage of labor

• May have to discontinue epidural if motor block is preventing pushing

Third stage of labor

• If there is a complication with delivery and patient does not have neuraxial analgesia, may have to administer general anesthesia– Shoulder dystocia– Emergent cesarean section

• Considerations for general anesthesia– More difficult intubation– Higher aspiration risk– Shorter lasting preoxygenation– Risk of fetal depression

Adverse effects of labor analgesia

• Systemic toxicity (inadvertent injection into blood vessel)– CNS (tinnitus, seizures) and cardiovascular

• High spinal– Aspiration, dyspnea, hypotension

• Hypotension (w/ decreased placental perfusion)• Failed block• Pruritis, nausea, vomting, backache, urinary retention• Postdural puncture headache (decreased with pencil point

spinal needles)• Respiratory depression, epidural hematoma, infection• Effects on fetus: hypotension; if not, then increased placental

flow, improved fetal acid/base status. Fetal bradycardia 2/2 uterine hypertonus 2/2 opioids

• Association with cesarean delivery and instrumental delivery but no causation