Can a low‑dose remifentanil infusion (target effect‑site concentration 0.5 ng/mL) be combined with propofol for general anesthesia in an otherwise healthy adult pregnant woman undergoing a cesarean delivery?

Remifentanil with Propofol for Cesarean Section: Safety and Recommendations

Yes, low-dose remifentanil (0.5 ng/mL effect-site concentration) can be safely combined with propofol for general anesthesia during cesarean delivery, as remifentanil is the preferred opioid in pregnancy due to its ultra-short context-sensitive half-life and minimal placental transfer. 1

Evidence-Based Rationale for Use

Remifentanil is specifically recommended as the preferred opioid analgesic when opioid analgesia is necessary during pregnancy because of its pharmacokinetic advantages 1. The American College of Obstetricians and Gynecologists endorses this approach based on remifentanil's rapid metabolism by nonspecific plasma and tissue esterases, which limits fetal exposure 1.

Key Pharmacologic Advantages

• Propofol is fully compatible with obstetric anesthesia, with minimal transfer to breast milk (0.025%) and no required waiting period before resuming breastfeeding 2
• The combination demonstrates synergistic interaction for maintaining adequate anesthetic depth, allowing lower doses of each agent 3
• Remifentanil's ultra-short half-life ensures rapid maternal and neonatal recovery compared to longer-acting opioids 1, 4

Critical Safety Considerations and Dosing

Hemodynamic Management

The primary concern with remifentanil-propofol combinations is significant hypotension, not dose-dependent across the remifentanil range studied 5. In healthy women receiving propofol 1.8 mg/kg with remifentanil doses ranging from 0.75-3.0 μg/kg, systolic blood pressure decreased by 30-32% regardless of remifentanil dose 5.

• Prepare vasopressors before induction (phenylephrine or ephedrine) as hypotension occurs predictably 5
• Your proposed 0.5 ng/mL target is at the lower end of the clinical range, which should minimize hemodynamic effects while providing adequate analgesia 2, 6

Respiratory Depression Risk

Adding even small doses of propofol to remifentanil significantly increases respiratory events including bradypnea, desaturation <90%, and apnea requiring intervention 6. This is acceptable in the controlled environment of cesarean delivery where:

• Immediate airway control is planned
• Continuous monitoring is standard
• Trained personnel manage respiratory events 6

Administration Protocol

Administer remifentanil and propofol in separate syringes via separate infusion lines 7. When mixed in the same syringe, remifentanil solution separates from propofol emulsion within minutes, with remifentanil rising to the top, making delivered concentrations unreliable 7.

Neonatal Considerations

Remifentanil crosses the placenta but is rapidly metabolized by the neonate 1. The 0.5 ng/mL maternal effect-site concentration represents minimal fetal exposure compared to longer-acting opioids that accumulate in fetal tissues.

• Neonatal resuscitation equipment must be immediately available as with any general anesthetic for cesarean delivery
• Naloxone should be prepared for potential neonatal opioid reversal, though rarely needed at this low dose 4

Postoperative Analgesia Planning

Critical pitfall: Remifentanil provides NO postoperative analgesia due to its ultra-short duration 4. You must administer a longer-acting opioid (morphine, hydromorphone, or fentanyl) before emergence to prevent an analgesic gap 4.

• Administer morphine 0.1-0.15 mg/kg IV or intrathecal morphine 100-200 mcg before discontinuing remifentanil 2
• Multimodal analgesia with paracetamol and NSAIDs is compatible with breastfeeding and should be initiated 2

Breastfeeding Compatibility

Both propofol and remifentanil are compatible with breastfeeding 2, 8. Breastfeeding may resume as soon as the mother has recovered sufficiently from general anesthesia 2.

• Remifentanil has low oral bioavailability, limiting infant absorption through breast milk 8
• No waiting period is required after single-dose or short-duration infusion 2

Common Pitfalls to Avoid

• Never assume remifentanil provides postoperative pain control—always transition to longer-acting analgesics before discontinuation 4
• Do not mix remifentanil and propofol in the same syringe—they separate and deliver unreliable concentrations 7
• Avoid ketamine as an alternative—it crosses the placenta and may cause neuronal apoptosis in the developing fetal brain 1
• Do not use high-dose remifentanil (>2 μg/kg bolus)—this causes prolonged apnea (up to 12.8 minutes) and severe hypotension without improving intubation conditions 2