Obstetric Anesthesia - Anesthetic Implications of Obstetric Complications

Lecturer: Laurie Barton

Key Points:

• Obstetric Complications: Preterm labor, multiple gestation, malpresentation, cord prolapse, embolic disorders.
• Preterm Labor: Increase in preterm births, definitions based on birth weight, importance of delaying labor with tocolytics for 48 hours to administer corticosteroids for fetal lung maturity.

Preterm Labor and Delivery

• Statistics: 12.8% of US births preterm in 2006.
  • Preterm defined as births before 34 weeks gestation.
  • Multiple gestation pregnancies contribute significantly to preterm births.
• Definitions:
  • Low Birth Weight: <2500 grams
  • Very Low Birth Weight: <1500 grams
  • Extremely Low Birth Weight: <1000 grams
• Management: Goal to delay labor for steroid administration (Betamethasone or Dexamethasone) and transfer to specialized facilities.
• Tocolytics: Used to delay labor for steroid efficacy. Magnesium sulfate is a common choice.

Anesthetic Considerations in Preterm Labor

• Magnesium Sulfate:
  • Lowers blood pressure without decreasing uterine blood flow.
  • Interactions with neuromuscular blockers; reduced maintenance dose advised.
  • Therapeutic window: 5-7 mg/dl; tight monitoring required.
• Beta-Adrenergic Receptor Agonists (Terbutaline):
  • Administered IV, sub-Q, or orally.
  • Side effects: Maternal tachycardia, pulmonary edema; fetal tachycardia, hypotension.
  • Use of phenylephrine to manage hypotension.
• Calcium Channel Blockers:
  • Side effects: Maternal hypotension, tachycardia; reduced efficacy of postpartum hemorrhage agents.
• Cyclooxygenase Inhibitors: Effective for preterm labor before 32 weeks; potential maternal/fetal side effects.

Multiple Gestation Pregnancies

• Placental Configurations: Monochorionic, Dichorionic; impacts risk and management.
• Hemorrhage Risks: Increased in both antepartum and postpartum periods; high rates of cesarean sections.
• Anesthetic Management: Early neuraxial anesthesia recommended; higher spread of anesthetic possible due to increased abdominal pressure.

Malpresentation

• Types: Frank breech, complete breech, footling breech, kneeling breech.
• Management:
  • Cesarean delivery common; risk of umbilical cord prolapse and fetal head entrapment.
  • External Cephalic Version (ECV): Higher success with neuraxial anesthesia but potential risks.

Embolic Complications

• Pulmonary Thromboembolism:
  • Diagnosis: Clinical signs, D-dimer, VQ scan, spiral CT.
  • Management: Anticoagulation with heparin, transition to warfarin postpartum.
• Venous Air Embolism:
  • Common in deliveries, managed by communication with surgical team and supportive measures.
• Amniotic Fluid Embolism:
  • Rare but high mortality; biphasic response (initial right heart failure, followed by left ventricular failure).
  • Management: Immediate CPR, emergency cesarean section, treat coagulopathy.

Final Notes

• Contact Information: Reach out to Laurie Barton for questions or clarifications.

Conclusion: Understanding anesthetic implications of obstetric complications is vital for the management and safety of both mother and child during complicated pregnancies and deliveries.