What causes an ineffective epidural (peridural anesthesia)?

Causes of Ineffective Epidural Anesthesia

Ineffective epidural anesthesia is most commonly caused by incorrect primary placement, secondary migration of the catheter after correct placement, or suboptimal dosing of local anesthetic drugs. 1

Technical Factors Contributing to Epidural Failure

Operator Experience and Timing

• Inexperienced providers have significantly higher rates of epidural failure, with low-volume specialists having 3.77 times greater odds of inadvertent dural puncture compared to high-volume specialists 2
• Epidurals placed during night shifts (19:00-08:00) have a 6.33 times higher relative risk of inadvertent dural puncture, likely due to provider fatigue and less experienced staff working during these hours 2

Placement Technique Issues

• Incorrect identification of the epidural space using loss of resistance technique can lead to catheter misplacement 2
• Catheter migration after initial correct placement is a common cause of epidural failure 1
• Catheter dislodgement at the skin level occurs in approximately 0.53% of cases 2
• Catheter entrapment in other anatomical structures (retroperitoneum, near blood vessels) can occur, especially in obese patients or with lateral positioning 3

Patient Factors

• Greater cervical dilation during labor increases the risk of inadvertent dural puncture 2
• Obesity can increase the risk of catheter misplacement due to difficult anatomy and greater distance from skin to epidural space 3
• Patient positioning during placement can affect success rates, with some evidence suggesting lateral decubitus position may be preferable to sitting 2

Pharmacological Factors

Dosing Issues

• Suboptimal dosing of local anesthetic is a primary determinant of epidural anesthesia quality 1
• With continuous infusion, dose is more important than volume or concentration for successful analgesia 1
• Inadequate spread of local anesthetic within the cerebrospinal fluid can occur with intrathecal catheters, especially with low flow rates 2

Catheter Position Problems

• Intravascular placement can result in rapid systemic absorption of the local anesthetic rather than neural blockade 4
• Subdural placement can lead to unpredictable spread of anesthesia 3
• Subcutaneous placement results in no anesthetic effect 3
• Unintentional subarachnoid (intrathecal) placement can lead to excessively high block or total spinal anesthesia 2

Monitoring and Detection of Epidural Failure

Signs of Ineffective Epidural

• Inadequate sensory blockade for the intended surgical or analgesic purpose 5
• Higher than expected pain scores despite appropriate dosing 5
• Unilateral or patchy block indicating uneven spread of local anesthetic 1
• Need for frequent bolus doses during labor analgesia 2

Testing for Proper Placement

• Catheter aspiration is widely used but not completely reliable - negative aspiration does not entirely preclude misplacement 2
• Multi-orifice catheters are more likely to produce a reliable aspiration test 2
• Test doses with local anesthetic and epinephrine can help identify intravascular placement but are not infallible 2

Prevention Strategies

Technique Optimization

• Using combined spinal-epidural technique may be more reliable than epidural alone, as free flow of CSF through the spinal needle confirms correct midline placement 2
• Proper catheter fixation techniques can reduce migration and dislodgement 1
• Clear labeling of catheters and good communication between healthcare professionals are essential to prevent dosing errors 2

Pharmacological Considerations

• Addition of adjuvants, especially opioids and epinephrine, may substantially increase the success rate of epidural analgesia 1
• Patient-controlled epidural analgesia with background infusion appears to be the best method for postoperative analgesia 1

Management of Specific Complications

High or Total Spinal Block

• Inadvertent high neuraxial block requiring cardiovascular and/or respiratory support occurs in approximately 1 in 4367 cases 6
• Signs include increasing agitation, significant hypotension, bradycardia, upper limb weakness, dyspnea or difficulty speaking 2
• Management includes circulatory support with vasopressors and fluids, supplemental oxygen, and possibly tracheal intubation and ventilation 6
• Block height should be assessed at least once every 5 minutes until no further extension is observed 2

Catheter Failure During Labor or Operative Delivery

• Overall intrathecal catheter failure rate is approximately 5.7%, with higher rates (6.1%) after inadvertent dural puncture 2
• Failure to extend the sensory block for operative delivery via an intrathecal catheter occurs in approximately 3.5-7.1% of cases 2
• Alternative methods of anesthesia should be planned in case extension of the block is not possible 2