What is the recommended starting infusion rate, concentration, and patient‑controlled epidural analgesia (PCEA) settings for a healthy adult woman in active labour with an epidural catheter?

Labour Epidural Infusion Rate and PCEA Settings

For a healthy adult woman in active labour, initiate epidural analgesia with bupivacaine 0.0625-0.125% combined with fentanyl 2-2.5 µg/mL at a continuous infusion rate of 10-12 mL/hour, and strongly consider adding PCEA with bolus doses of 5 mL every 10-15 minutes as needed, as this approach provides superior analgesia with less motor blockade and fewer anesthetic interventions compared to continuous infusion alone. 1, 2, 3

Initial Loading Dose

Before starting the maintenance infusion, establish analgesia with an initial epidural bolus:

• Administer bupivacaine 0.125-0.25% (20-30 mL total volume, equivalent to 25-75 mg) combined with fentanyl ≤15 µg to achieve rapid onset of analgesia while minimizing side effects 2, 3, 4
• Limit fentanyl to ≤15 µg in the initial bolus to reduce pruritus, nausea, and respiratory depression without compromising analgesia 2
• Account for 0.5-1 mL catheter dead space which can dilute the first dose; if inadequate analgesia occurs within 15-20 minutes, give a supplemental 2.5 mg bupivacaine bolus 2

Maintenance Infusion Parameters

Concentration and Composition

Use the lowest effective concentration to minimize motor block while maintaining adequate analgesia:

• Bupivacaine 0.0625-0.125% (0.625-1.25 mg/mL) combined with fentanyl 2-2.5 µg/mL is the recommended concentration range 1, 2, 3
• Bupivacaine 0.125% with fentanyl 1 µg/mL represents a commonly used middle-ground formulation 3, 4
• Avoid concentrations below 0.0625% bupivacaine as they provide inadequate analgesia, particularly in the first 4 hours 5

The evidence strongly supports adding opioids to reduce local anesthetic concentration requirements. Research demonstrates that epidural fentanyl infusions are more than three times as potent when given epidurally versus intravenously (minimum local analgesic concentration 0.019% vs 0.063%), confirming a predominantly spinal mechanism of action. 4

Infusion Rate

• Start at 10-12 mL/hour for continuous infusion 3, 4
• Alternative range: 8-15 mL/hour depending on patient response and analgesic requirements 2, 6

Patient-Controlled Epidural Analgesia (PCEA) Settings

PCEA is preferable to continuous infusion alone because it provides fewer anesthetic interventions, reduced local anesthetic dosages, and less motor blockade. 1

PCEA Configuration Options

Option 1: PCEA with Background Infusion (Recommended)

• Background infusion: 8-10 mL/hour of bupivacaine 0.0625-0.1% with fentanyl 2 µg/mL 2
• PCEA bolus: 5 mL 2
• Lockout interval: 10-15 minutes 2
• Maximum hourly limit: Consider setting at 15-20 mL/hour total (background plus PCEA boluses)

Option 2: PCEA Without Background Infusion

• PCEA bolus: 5-8 mL of the same concentration 1
• Lockout interval: 10-15 minutes
• This approach may be used but typically requires more frequent patient-initiated boluses

The ASA guidelines explicitly state that PCEA may be used with or without a background infusion, giving flexibility based on institutional protocols and patient needs. 1

Monitoring Requirements

• Check blood pressure every 5 minutes for at least 15 minutes after any bolus dose 7
• Maintain continuous fetal heart rate monitoring for 30 minutes after the initial dose 2
• An anesthetist should remain present for at least 10 minutes after initial bolus 7
• No additional cardiovascular or respiratory monitoring beyond routine epidural practice is typically required for standard epidural infusions 2

Management of Breakthrough Pain

If analgesia becomes inadequate during labour:

• Administer 1-2 mL clinician bolus of the maintenance solution (not a more concentrated solution) 2
• If inadequate after additional bolus, consider removing and re-siting the catheter or using alternative analgesia 7
• For PCEA patients, first assess if they are using their PCEA appropriately before intervening with clinician boluses

Critical Concentration Considerations

The evidence demonstrates important dose-volume relationships:

• Bupivacaine 0.125% requires 50% more volume than 0.25% (13.6 mL vs 9.2 mL) but uses 25% less total drug (17.0 mg vs 23.1 mg) to achieve equivalent analgesia 6
• This volume-dose trade-off favors dilute concentrations (0.0625-0.125%) because any reduction in total bupivacaine dose reduces toxicity risk while the larger volume improves epidural spread 6
• Concentrations below 0.031% provide inadequate analgesia and should be avoided 5

Common Pitfalls to Avoid

• Do not use bupivacaine concentrations >0.125% for maintenance as this increases motor block without improving analgesia and may impair maternal pushing effectiveness 1, 7
• Do not exceed 15 µg fentanyl in the initial loading dose to minimize side effects 2
• Do not forget to account for catheter dead space when troubleshooting inadequate initial analgesia 2
• Do not use fixed-rate continuous infusion alone when PCEA is available, as PCEA provides superior outcomes 1