Fluoroscopy-assisted epidural catheter placement: the effect of dye distribution in preoperative epidurograms on postoperative analgesia

Background
Postoperative epidural analgesia provides superior postoperative analgesia at rest and with activity, compared with systemic opioids. However, the impact of postoperative epidural analgesia on postoperative morbidity and/or mortality remains controversial, because of the sub-optimal reliability of epidural catheters that are placed preoperatively and used for postoperative pain control. The present study used the technique of lumbar epidurography. The study aims to better understand the possible correlation between the fluoroscopic characteristics of epidural catheters following injection of contrast medium and the postoperative functional characteristics regarding analgesia. In this single-arm clinical trial, 70 patients, aged 50 to 75 years old, underwent surgical urological procedures, involving incisions up to T dermatome, under combined general and epidural anesthesia. At the L-L level, the epidural space was reached using the loss of resistance technique before general anesthesia was induced. The catheters were threaded upwards for 4–6 cm. Preoperative epidurograms were then done by injecting a 3-ml contrast medium Omnipaque (240 mg I/ml) in the epidural catheters. The epidurograms were investigated for the location of the catheter tip in relation to the vertebral body, the extent of dye spread, laterality of dye spread (midline, right, or left), and the presence or absence of dye spread anterior to the spinal cord on the lateral image. The patients were followed postoperatively while epidural analgesia was infused.
Results
Both the postoperative epidural infusion and postoperative visual analog scale (VAS) scores were lower when catheter tips ended at L than when they ended at L. As the contrast’s vertical spread increases in preoperative epidurograms, the analgesic infusion rate and VAS score decrease, and the number of dermatomes insensitive to cold increases. Epidurographically right-sided catheters showed more dermatomes deficient to cold sensations on the right side, compared with mid-line and left-sided catheters. Restriction of contrast to the posterior epidural space was associated with lower VAS scores and wider anesthesia to cold.
Conclusions
The use of epidurography to study epidural catheters may have the potential advantage of predicting the functionality of catheters and improving the reliability of postoperative epidural analgesia.