What are the desired levels of analgesia or anesthesia for epidural conversion?

Desired Sensory Levels for Epidural Conversion

For cesarean section via epidural conversion, achieve a T4 sensory level to pinprick testing, while labor analgesia requires only T10 level. 1, 2, 3

Surgical Anesthesia Requirements

Cesarean Section

• Target sensory level: T4 to pinprick 1, 2
• This level ensures adequate anesthesia for peritoneal manipulation and uterine exteriorization 3
• Achieve this through incremental dosing of local anesthetic (typically bupivacaine 0.75% in 2.5 mg increments every 3 minutes) until T4 is reached 1, 4
• Mean total dose required: 15 mg bupivacaine (range 10-25 mg) when converting intrathecal catheters 1, 4

Major Abdominal Surgery

• For upper abdominal surgery: T4-T6 sensory level 1
• Epidural catheters should be inserted between T5 and T8 root levels for upper transverse incisions 1
• For lower abdominal procedures: T8-T10 level is typically sufficient 5, 3

Thoracic Surgery

• Mid-thoracic epidurals (T5-T8 insertion) provide optimal coverage 1
• Sensory block should be tested with cold and pinprick before induction of general anesthesia 1

Labor Analgesia Requirements

Active Labor

• Target sensory level: T10 3
• This provides adequate coverage for first stage labor pain from uterine contractions and cervical dilation 3
• Lower concentrations are used (bupivacaine 0.0417-0.1% or ropivacaine 0.2%) to minimize motor block 2, 6

Operative Vaginal Delivery

• Extend block to T8-T10 level 1
• May require additional boluses of 2.5 mg bupivacaine 1
• Some protocols allow 1 mL increments of bupivacaine 0.25% 1

Critical Monitoring and Safety Protocols

Sensory Level Assessment

• Test sensory block with both cold and pinprick testing before proceeding 1
• Assess sensory level every 5 minutes until no further extension is observed 4
• Check sensory block on a daily (or more frequent) basis during continuous infusions 1

Motor Block Monitoring

• Monitor for straight-leg raising ability as screening for motor block 4
• Alert anesthesiologist if patient cannot perform straight-leg raising at 4 hours from last epidural dose 4
• Excessive motor block is considered a complication in obstetrics as it prolongs second stage labor 3

Common Pitfalls and Caveats

Inadequate Block Height

• Failure rates for cesarean section conversion range from 3.5-7.1% 1
• Most failures occur when sensory level does not reach T4 1
• The insertion level must cover the surgical incision site 1

Hypotension Risk

• Hypotension incidence is significantly higher with intrathecal catheters (25.6%) versus epidural (3.8%) 2
• Have vasopressors (phenylephrine or ephedrine) immediately available 4, 6
• Monitor blood pressure every 5 minutes for at least 15 minutes after initiating infusion 6

Dosing Considerations

• One-third of epidurals may not function satisfactorily 1
• Possible reasons include: catheter not in epidural space, insertion level doesn't cover incision, insufficient dosage, or pump failure 1
• Always use incremental dosing rather than large boluses to minimize risk of high or total spinal 2, 4