Failed Epidural: Causes and Management
In conclusion, failure of epidural anaesthesia and analgesia occurs in up to 30% in clinical practice. Some technical factors can help to increase the primary and secondary success rate. Epidural catheters may be incorrectly placed, or may migrate after initial correct placement due to body movement and oscillations in CSF. Catheters may deviate from the midline during insertion. The optimal depth of insertion in adults is ~5 cm. The most widely used method with the least side-effects for localizing the epidural space is LoR to saline. None of the additional technical tools available has sufficient accuracy and predictability to justify routine use, but there is a growing evidence-base for ultrasound in obese patients and infants. The optimal test dose should combine lidocaine and epinephrine, to detect intrathecal and intravascular placement, respectively. The choice of long-acting local anaesthetic agent seems to be less important clinically. Dose is the primary determinant of continuous epidural anaesthesia, with volume and concentration playing a subordinate role. Addition of opioids may substantially increase the effectiveness of epidural analgesia. Epinephrine augments analgesia by delaying resorption of local anaesthetic from the epidural space, and by direct antinociceptive action at the spinal cord. The use of patient-controlled epidural analgesia with background infusion appears to be the best method for postoperative analgesia.
Conclusion
In conclusion, failure of epidural anaesthesia and analgesia occurs in up to 30% in clinical practice. Some technical factors can help to increase the primary and secondary success rate. Epidural catheters may be incorrectly placed, or may migrate after initial correct placement due to body movement and oscillations in CSF. Catheters may deviate from the midline during insertion. The optimal depth of insertion in adults is ~5 cm. The most widely used method with the least side-effects for localizing the epidural space is LoR to saline. None of the additional technical tools available has sufficient accuracy and predictability to justify routine use, but there is a growing evidence-base for ultrasound in obese patients and infants. The optimal test dose should combine lidocaine and epinephrine, to detect intrathecal and intravascular placement, respectively. The choice of long-acting local anaesthetic agent seems to be less important clinically. Dose is the primary determinant of continuous epidural anaesthesia, with volume and concentration playing a subordinate role. Addition of opioids may substantially increase the effectiveness of epidural analgesia. Epinephrine augments analgesia by delaying resorption of local anaesthetic from the epidural space, and by direct antinociceptive action at the spinal cord. The use of patient-controlled epidural analgesia with background infusion appears to be the best method for postoperative analgesia.