What is the standard technique for placing an epidural catheter in adult patients, which local anaesthetics and adjuncts are typically used, and what are the advantages of epidural anaesthesia compared with single‑shot spinal anaesthesia?

Epidural Anaesthesia: Technique, Drugs, and Advantages Over Spinal

Epidural anaesthesia provides superior flexibility for prolonged procedures and postoperative analgesia through catheter-based incremental dosing, though it requires higher local anaesthetic doses and has slower onset compared to single-shot spinal anaesthesia. 1

Standard Epidural Placement Technique

Catheter Positioning by Surgical Site

• For upper abdominal/thoracic procedures (e.g., total hysterectomy): Insert the epidural catheter between T5-T8 vertebral levels, with the catheter tip positioned at T6-T8 to provide adequate analgesia 2
• For major abdominal surgery: Target thoracic epidural at T6-T10 levels, aiming for a sensory block at T4-T6 2
• For lower extremity procedures (hip/knee replacement): Place lumbar epidural at L3/4 as the standard location 2

Catheter Insertion Depth and Technique

• Insert the epidural catheter 3-5 cm into the epidural space to minimize dislodgement risk while avoiding complications 2
• Loss of resistance technique remains the traditional method for identifying the epidural space, though it can lead to incorrect space identification if performed improperly 3
• Paramedian approach with real-time ultrasound guidance achieves 93.3% success rate and allows visualization of neuraxial changes (anterior dural displacement, posterior epidural space widening) upon needle entry 4
• Administering 20 mL of 2% lidocaine through the epidural needle before catheter insertion reduces paresthesia during catheter placement (11% vs 31.6%), decreases intravascular catheterization (2% vs 8.2%), and improves surgical conditions (89.6% vs 72.9% excellent outcomes) 5

Confirmation of Correct Placement

• Test dose composition: Use 3 mL of 1.5% lidocaine (45 mg) with epinephrine 15 µg (1:200,000) to screen for both intravascular and intrathecal misplacement 6
• Maximum safe test dose: Do not exceed 10 mg bupivacaine-equivalent (approximately 30-45 mg lidocaine) to minimize total spinal anaesthesia risk while producing clinically evident effects 6
• Monitoring timeline:
  • At 0-1 minute: Check for heart rate increase ≥10 bpm or systolic BP rise ≥15 mmHg (indicates intravascular placement) 6
  • At 3-5 minutes: Assess motor block by asking patient to raise legs (95-100% sensitivity and 93-100% specificity for intrathecal placement) 6
  • Monitor sensory block extension to T1-T2 dermatomes within 10-15 minutes (confirms intrathecal injection) 6
• Pressure waveform analysis shows 95.9% sensitivity and 98.9% positive predictive value for confirming correct epidural needle placement in labouring women 7

Local Anaesthetics and Adjuncts

Initial Dosing Regimens

• For thoracic epidural in adults: Use 0.2-0.3 mL/kg of 0.25% bupivacaine (maximum 10 mL) as initial dose 2
• For lumbar epidural in adults: Use 0.5 mL/kg of 0.25% bupivacaine (maximum 15 mL) as initial dose 2

Opioid Adjuncts

• Combining local anaesthetic with strong opioids (morphine, fentanyl, sufentanil) significantly reduces supplementary analgesic consumption and increases time to first analgesic request compared to local anaesthetic alone 1
• For labour analgesia via intrathecal catheter: Use dilute solutions of bupivacaine 0.0417-0.1% with fentanyl 2-2.5 µg/mL at 1-3 mL/hour 6
• Spinal morphine demonstrates superiority over nalbuphine and diamorphine for decreasing supplementary analgesic consumption, though pain scores remain similar 1

Continuous Infusion Techniques

• Continuous spinal infusion plus patient-controlled analgesia provides significantly lower postoperative pain scores and uses less total bupivacaine compared to nurse-administered on-demand spinal doses 1
• Patient-controlled epidural analgesia (PCEA) with bupivacaine and sufentanil following combined general and epidural anaesthesia shows better cognitive outcomes (Abbreviated Mental Test scores) on postoperative days 4-5 compared to PCA alone 1

Advantages of Epidural Over Single-Shot Spinal

Flexibility and Duration

• Catheter-based technique allows incremental dosing and prolongation of anaesthesia for extended procedures, which is theoretically preferable to single-shot techniques 1
• Epidural catheters can be extended for caesarean section when initially placed for labour analgesia, though success depends on factors including number of analgesic boluses during labour, urgency category, and provider specialization 1

Postoperative Analgesia

• Epidural analgesia provides superior pain relief and fewer respiratory complications compared to intravenous opioids for major surgery 2
• Femoral nerve catheter plus PCA reduces postoperative delirium rates (25% vs 61%) compared to PCA alone in total knee arthroplasty patients, with 7.02 times lower odds of delirium after controlling for preoperative cognitive function 1
• Fascia iliaca blocks repeated every 24 hours in hip fracture patients reduce delirium incidence (10.78% vs 23.8%), severity, and duration compared to sham blocks 1

Titratability and Safety

• Epidural technique allows gradual titration to desired sensory level, reducing risk of sudden high or total spinal block compared to single-shot spinal 1
• Block height should be monitored every 5 minutes until no further extension is observed, watching for signs of high block (agitation, significant hypotension, bradycardia, upper limb weakness, dyspnea, difficulty speaking) 2, 3

Critical Disadvantages and Limitations

Technical Challenges

• Epidural anaesthesia uses high local anaesthetic doses, is slower, and provides poorer sacral blockade compared to spinal anaesthesia 1
• Inexperienced providers have 3.77 times greater odds of inadvertent dural puncture compared to high-volume specialists 3
• Night shift placement (19:00-08:00) carries 6.33 times higher risk of inadvertent dural puncture due to provider fatigue and less experienced staff 3
• Catheter dislodgement at skin level occurs in approximately 0.53% of cases 3

Failure Rates

• Combined spinal-epidural technique is more reliable than epidural alone as long as the spinal component is successful, with free CSF flow confirming correct midline epidural needle placement 1
• Overall intrathecal catheter failure rate is approximately 5.7%, with higher rates (6.1%) after inadvertent dural puncture 3
• Failure to extend sensory block for operative delivery occurs in 3.5-7.1% of cases with intrathecal catheters 3

Common Pitfalls to Avoid

• Never assume negative aspiration rules out misplacement—direct intrathecal injection after negative aspiration occurs in 1:1,750 to 1:126,000 cases 6
• Multi-orifice catheters provide more reliable aspiration than single-orifice catheters, though negative aspiration does not definitively exclude misplacement 3, 6
• Do not rely solely on subjective symptoms (leg warmth/heaviness) for intrathecal detection, as specificity is only 59-74% 6
• Clear labeling of catheters and good communication between healthcare professionals are essential to prevent dosing errors 3
• Alternative methods of anaesthesia should be planned in case extension of the block is not possible 3