Why do thoracic epidurals fail? A literature review on thoracic epidural failure and catheter confirmation

Table 1 Causes and factors contributing to thoracic epidural failure

Causes of epidural failure	Factors contributing to failure
Incorrect catheter placement	Misplacement into paravertebral space, pleural space, or intravascularly
	Catheters placed at the wrong level
Equipment failure	Debris in the catheter
	Disconnections, air locks, or knotting and kinking of the catheter
Epidural space characteristics and complexities	Midline fat pedicles and adhesions impeding adequate spread of local anesthetics

Table 2 Studies discussing thoracic epidural failure

Ref.	Factors contributing to epidural failure
Porteous et al[5]	Equipment failure, such as debris in the catheter, incorrect catheter placement, epidural space characteristics and complexities
Motamed et al[8]	Anatomical variances, coiling and kinking of the catheter
Hamilton et al[9]	Changes in the position of epidural catheters associated with patient movement
Tran et al[11]	Primary failure of thoracic epidural analgesia in training centers
Yeager et al[14]	Malposition of epidural catheters
Tsui et al[15]	Incorrect catheter placement
Balki et al[16]	Incorrect catheter placement
Ghia et al[17]	Incorrect catheter placement
Lennox et al[18]	Incorrect catheter placement
Sánchez et al[20]	Incorrect catheter placement
Johnson et al[21]	Incorrect catheter placement

Table 3 Techniques for confirming thoracic epidural catheter position

Technique	Description	Advantages	Disadvantages
Electrophysiological stimulation	Connecting nerve stimulator to catheter	High sensitivity and effectiveness in confirming position	Requires specialized adaptor
	Applying current and assessing motor response	Correlation with adequate postoperative analgesia	Discomfort to awake patient
	Bilateral stimulation indicates proximity to nerve root		Does not give information on local spread
	Limb or truncal response indicates epidural space
Epidural catheter waveform	Connecting catheter to pressure transducer	Simple technique using readily available equipment	Does not provide information about catheter level or injectate spread
	Confirming epidural space when pulsatile waveform is obtained
Contrast epidurography	Taking X-ray after injection of radio-opaque contrast	Confirms epidural position and assesses catheter level and spread pattern	Involves X-ray, may not be suitable for all patients
	Assessing contrast spread and catheter placement	Identifies anatomical variances and coiling/kinking	Time-consuming. Required training for epiduralgram interpretation
	Evaluating bilateral spread and vertebral levels		Risk of transiently raising spinal cord pressure with large volumes

Table 4 Studies done on confirming thoracic epidural catheter position

Ref.	Techniques for confirming catheter position
Teoh et al[10]	Surface anatomy as a guide to vertebral level for thoracic epidural placement
Yokoyama et al[13]	Evaluation of contrast medium distribution and blockade extent during epidural anesthesia
Yeager et al[14]	Fluoroscopy-assisted epidural catheter placement
Tsui et al[15]	Confirmation of catheter placement using nerve stimulation
Balki et al[16]	Epidural electrical stimulation test
Ghia et al[17]	Confirmation of catheter position using epidural pressure waveform and computed tomography catheter gram
Lennox et al[18]	Use of pulsatile pressure waveform as a marker for confirming the location of the thoracic epidural space
Sánchez et al[20]	Radiological visualization of catheters placed in the epidural space