Excessive dose requirements of local anaesthetic for epidural analgesia

Abstract

SummaryOn tw'o separate occasions, a 78-year-old obese man suffering ,from congestive cardiac ,failure and peripheral vascular disease, required epidural anaesthesia for surgery to his leg. The dosage requirement on the,first occasion was large and much greater than on the second occasion. Reasons.for the difference in dosage are discussed. We suggest an epidural catheter should be inserted 3 cm into the epidural space.

Appropriate length of epidural catheter in the epidural space for postoperative analgesia: evaluation by epidurography

“…Clinical trials have shown that even if the epidural catheter was left 2-5 cm in the epidural space, this was found to provide satisfactory analgesia. However, one trial has shown that if more than 3 cm of the epidural catheter is left in the epidural space, this increases the risk of transforaminal escape [4].…”

“…The gold standard for identification of the epidural space is the loss-of-resistance technique [4,5]. At the time of this study, we considered the best method to confirm the catheter position in the epidural space.…”

“…Clinical trials have shown that even if the epidural catheter was left 2-5 cm in the epidural space, this was found to provide satisfactory analgesia. However, one trial has shown that if more than 3 cm of the epidural catheter is left in the epidural space, this increases the risk of transforaminal escape [4].The length of the epidural catheter that should be left in the epidural space has not been standardised. The main aim of this study was to determine the most appropriate length of epidural catheter that should be inserted into the epidural space for postoperative analgesia.…”

Insertion length and resistance during advancing of epidural catheter

“…It is suggested to thread in a length of at least 4 cm inside the epidural space to prevent inadequate block that might occur due to the movement of the catheter out of the epidural space during traction applied by fi xation to the skin [8]. Conversely, if a greater length of the catheter is threaded in, there is uncertainty regarding the position of the catheter and the possibility of extrusion of the catheter through the intervertebral foramen [16][17][18]; probably this is the reason why a higher incidence of unsatisfactory analgesia was seen with 8-cm insertion in our study (13.3% in the 8-cm group and 6.7% in the 4-cm group). Radiological evidence reported by Bridenbaugh et al [15] also suggested that only 12% of all epidural catheters directed in a cephalad direction actually threaded to the "hoped for" anatomic levels, while 21% of the catheters had a terminal loop, 48% coiled at the insertion site, and 5% went in a caudal direction or migrated out through an intervertebral foramen.…”

Tensile Strength Decreases and Perfusion Pressure of 3-Holed Polyamide Epidural Catheters Increases in Long-Term Epidural Infusion

“…Histopathologic reactions 7 and blockage of the holes at the catheter tip may lead to decreasing flow rates of the local anesthetic solution, impair distribution of the anesthetic, and thus decrease the analgesic effect. 7,8 Hence, a blockade of 1 or more holes at the catheter tip may increase the perfusion pressure with less anesthetic solution delivered to the epidural space. 7,8 A decrease of the tensile strength may facilitate epidural catheter breakage on withdrawal.…”