Obstetrical Anesthesia - Pain Management in Labour:

Stage of Labour

Etiology

Nerve supply

1

Contractions of lower segment of uterus and cervical dilatation

T10-L1

2

Vagina and perineum

S2-4


Non-Pharmacological Methods

Non-pharmacological methods include childbirth preparation (ex prenatal classes), emotional support, massage and touch therapy, therapeutic use of heat and cold, hydrotherapy, hypnosis, acupuncture, aromatherapy, and transcutaneous electrical nerve stimulation.

Pharmacological Interventions

Method: Inhalational analgesia

Examples: Nitrous oxide

  • Relatively contraindicated in pulmonary disease

Benefits: Quick to administer

Risks: Lack of scavenging system results in pollution

Method: Systemic analgesia

Examples: Opioids such as morphine, fentanyl IV PCA, remifentanil IV PCA

Benefits:

  • Provides analgesia and anxiolysis
  • Easy to administer
  • High therapeutic ratio
  • Relatively inexpensive
  • Antidote available (Naloxone)

Risks:

  • May cause maternal sedation and respiratory depression
  • GI upset
  • May cause hypotension
  • Reduces fetal heart rate variability
  • May cause neonatal respiratory depression and sedation

Method: Local Anesthesia

Examples:

  • Infiltration of the perineum
  • Paracervical block
  • Pudendal nerve block

Benefits: Can provide excellent pain relief

Risks:

  • Requires skilled personnel
  • Paracervical block covers pain from contractions only; pudendal block covers pain from perineum only

Method: Regional Analgesia

Examples:

  • Epidural
  • Combined spinal-epidural (CSE)

Benefits:

  • Awake patient
  • Avoids airway manipulation
  • Post-operative pain control

Risks: Discussed in further detail in sections below


Epidural Analgesia

Epidurals can be for analgesia in labor or anesthesia for C-Section. Epidural analgesia seeks to provide pain relief and minimize motor side effects. The dosages are unlikely to approach toxic levels as the concentrations are very dilute.

Indications include maternal request in active labour.

Contraindications include lack of patient consent, lack of proper equipment (including resuscitative equipment), lack of experienced personnel, infection at the site of puncture, septic shock, severe hypovolemia, severe coagulopathy or anticoagulation, supratentorial space occupying lesion.

Relative contraindications include mild coagulopathies, hemodynamic instability, stenotic valvular lesions, raised ICP, progressive neurologic deterioration of unknown etiology, spina bifida, severe scoliosis or previous back surgery, false labour.

Complications include infection (at skin or epidural abscess), bleeding (epidural hematoma), post-dural puncture headache, nerve damage, and failure (inadequate analgesia). Serious complications are rare. Epidural abscesses and hematomas may require surgical treatment. Nerve damage is usually managed expectantly with observation. In the event of hypotension or fetal bradycardia after initiating medications through the epidural catheter, the mother should be resuscitated with left uterine tilt, fluids, and a decrease in or discontinuation of epidural medications.

An epidural is typically “loaded” with local anesthetic (bupivacaine or ropivicaine usually) and then maintained with a continuous infusion of dilute local anesthetics, with patient-controlled epidural analgesia bolus, or a combination of both.

Epiriral Anesthesia

From WikiCommons


Combined Spinal Epidural (CSE)

The epidural space is identified in the standard fashion, a small gauge (25 or 27) non-cutting spinal needle is then passed through the epidural needle into the subarachnoid space with a small dose of bupivacaine 1-2mg +/- lipophilic opioid. The spinal needle is removed and an epidural catheter is placed for maintenance of analgesia. CSE allow for rapid onset of analgesia with little motor block. The disadvantage is the theoretical risk of 1) piercing the dura and possibly increasing the risk of infection or nerve damage and 2) a somewhat higher incidence of fetal heart rate abnormalities




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