Thoracic caudal epidural catheter localization using ultrasound guidance

Caudal epidural catheters provide exceptional analgesia while avoiding or minimizing opioids. Historically, the catheter tip location (dermatomal level) was estimated or verified via epidurogram. According to the Pediatric Regional Anesthesia Database, the majority of caudal‐to‐thoracic epidural catheters are placed without imaging guidance or verification of the position of the catheter tip. Ponde et al demonstrated that catheter insertion depth was longer when using ultrasound guidance than when estimated by external measurement. We report a simple yet novel ultrasound approach for catheter localization.     

Thoracic epidural catheters placed by the caudal route in infants: the importance of radiographic confirmation

BACKGROUND: Cephalad advancement of epidural catheters to the thoracic region via the caudal route has been shown to be feasible in neonates and small infants. This has allowed many young infants to receive thoracic level epidural analgesia with dilute local anaesthetic solutions using the simpler caudal approach. Since radiographic confirmation of the catheter tip is routine at this institution, we wished to determine how often radiographic studies led to adjustment or replacement of the epidural catheter. METHODS: After institutional review board approval, we retrospectively reviewed the medical records of neonates and infants less than 6 months of age who had thoracic or lumbar epidural analgesia via the caudal route between August 1995 and January 2000. Demographic data were recorded, including age, weight and type of surgery. The epidural catheter type, tip location by radiograph and any manipulation of the catheter after the radiograph were also noted. RESULTS: During the study period, a total of 115 infants were identified as having received caudal placement of a thoracic catheter. Radiographic studies were available for 86 of these infants. The position of 28 (32%) of the epidural catheters was considered to be inadequate after review of the confirmatory radiograph. Ten of these catheters were determined to be in the high thoracic or cervical region and were pulled back to the desired level. Seventeen of these catheters were coiled in the lumbosacral area and 15 of these were replaced at an adequate level. One catheter was found to be outside the epidural space in the presacral area. No correlation could be found between age, weight, type of catheter or type of surgery and the need for catheter manipulation. CONCLUSIONS: Even in young infants, radiographic determination of the catheter tip appears warranted when thoracic catheters are placed via the caudal route.     

The dose of caudal epidural analgesia and duration of postoperative analgesia

BACKGROUND: Single dose caudal epidural is commonly utilized for postoperative analgesia in children. Previous studies have determined the optimal concentration of local anaesthetic, and the minimal volume to produce a desired dermatomal distribution. However, none has sought the optimal volume to administer. The specific aim of this study was to determine whether the volume of caudal epidural local anaesthetic influenced the duration of postoperative analgesia. METHODS: Fifty-four children aged 1-6 years and ASAPS I-II scheduled for elective inguinal herniorraphy were enrolled in this randomized and blinded clinical trial. They received a standardized general anaesthetic with one of three possible doses of caudal epidural analgesic: 0.7, 1.0, or 1.3 ml.kg-1 of 0.175% bupivacaine with 1 : 200 000 epinephrine. The patients were assessed by blinded observers during in-hospital recovery and by parents at home. RESULTS: The principal outcome measure of time until first postoperative analgesic requirement was similar between the groups (4.2, 3.6, and 4.8 h respectively). Other effects which might be altered by epidural analgesia, including time until first void, ambulation, and discharge readiness did not differ between groups. CONCLUSIONS: Increasing local anaesthetic dose and volume do not increase the duration of postoperative analgesia of caudal epidural in children undergoing inguinal herniorraphy.     

Spread of radioopaque dye in the epidural space in infants

BACKGROUND: This prospective study aimed to assess the extent of spread of dye in the epidural space and whether it would vary in direct proportion to the volume when injecting two volumes of dye. METHODS: Ten infants, aged 2-36 days (mean +/- SD, 13.30 +/- 13.68 days) and weighing 1.8-4.5 kg (mean +/- SD, 2.60 +/- 0.97 days), who were undergoing major thoracoabdominal surgery under epidural and general anaesthesia, were studied. At the end of surgery, two volumes of radioopaque dye (omnipaque) 0.5 ml.kg(-1) and 1 ml.kg(-1) were injected into the epidural space at a rate of 1 ml.2 min(-1). The spread was studied by taking X-rays after both injections in the left lateral position. RESULTS: There were 10 different patterns of spread in the 10 cases. Uniformly circumferential and cylindrical spread was seen only in one infant. In the others, there were segregated patches of anterior and posterior spread with or without interspersed patches of circumferential spread. There was variation in the extent, location and the density of spread, filling defects and skipped segments with both volumes. Back leak of dye along the needle track was seen in three cases. Statistically, segments were 9.30 +/- 3.68 for 0.5 ml.kg(-1), for 1 ml.kg(-1) 11.50 +/- 3.03, 3.03, S, P=0.014; circumferential spread for 0.5 ml.kg(-1) 2.70 +/- 2.16, for 1 ml.kg(-1) 5.90 +/- 3.14 3.59, P=0.006; anterior spread for 0.5 ml.kg(-1) 3.60 +/- 1.58, for 1 ml kg(-1) 7.90 +/- 2.33 5.88, P=0.001; posterior spread for 0.5 ml.kg(-1) 8.20 +/- 3.71, for 1 ml.kg(-1) 9.80 +/- 3.68 3.54, P=0.006. Doubling of spread with doubling of the volume occurred in only one patient. There was a variable increase in extent or in the density of spread with reduction of skipped segments with the 1 ml.kg-1. The probable reasons for this variable spread and the mechanism of epidural anaesthesia in the presence of such spread are discussed. CONCLUSIONS: There is a difference in quantitative as well as qualitative spread in different patients and in the same patient with different volumes. There were statistically significant increases in the number of segments, circumferential, anterior and posterior locations in the 1.0 ml group. Both extent and density of spread improve with the higher volume but not in direct proportion to volume. 1 ml.kg(-1) has a better quantitative as well as qualitative spread than 0.5 ml and has a better chance of producing adequate anaesthesia.     

Migration of thoracic epidural catheters

Migration of thoracic epidural catheters was evaluated in 25 patients by three methods either after placement of the catheter or immediately after surgery. The first method was the determination of the depth of the catheter from the skin, the second the determination of the level of sensory blockade which resulted from a test dose of a local anesthetic agent, while the third consisted of radiological visualisation of the catheter tip in the epidural space with radiopaque dye. The evaluations were repeated on the third or fourth day after operation. We observed an inward movement of the catheter in 56% of the patients instead of the expected outward movement. This inward movement was accompanied by a higher level of sensory blockade. No relationship with radiological visualisation was found.     

Lumbar and thoracic epidural anaesthesia in children

Epidural anaesthetic techniques are an established part of paediatric anaesthesia. Their positive effects on general anaesthetic requirements, stay in the recovery unit, efficient perioperative pain relief and blunting of the perioperative stress response promote the routine use of regional anaesthetic techniques in children.With increasing knowledge of the anatomy and physiology of children, refinements in equipment and increased knowledge of the pharmacology of the agents used, continuous epidural catheter techniques are considered to be safe. There is some evidence that an epidural approach via the caudal and trans-sacral route is a low-risk procedure, even if the catheter is advanced to higher levels. Despite its positive effects the direct puncture at thoracic levels will probably never reach the level of routine practice. Because of its potential risks, the use of thoracic epidural anaesthesia (TEA) should be restricted to experienced paediatric anaesthetists and specialized centres.     

Techniques of epidural block

Epidural blocks can be performed at any level from the high cervical spine down to the sacral hiatus. A lumbar epidural can provide surgical anaesthesia and postoperative analgesia for sub-umbilical surgery, whereas a thoracic epidural will provide effective analgesia but not anaesthesia for thoracic and upper abdominal surgery. A single-shot bolus has a duration of 2-4 hours, using a long-acting local anaesthetic, but in the majority of cases prolonged postoperative analgesia is achieved by inserting an epidural catheter and infusing a dilute local anaesthetic and opioid drug combination. Although a useful regional anaesthetic technique with significant patient benefits, an epidural is an invasive procedure, can be technically difficult, and has the potential to cause serious adverse events (direct needle trauma to the spinal cord or the spinal nerve roots, vertebral canal haematoma and meningitis or epidural abscess) if not done to a high standard and managed appropriately. Epidural and caudal blockade have a number of synonyms, which can be confusing. The terms ‘epidural’ (extradural, peridural) and ‘caudal’ (sacral epidural) are used throughout this article.     

Techniques of epidural block

Epidural blocks are used for relief of chronic pain, labour pain and postoperative pain as well as for surgical anaesthesia. Effect can be targeted at the insertion level which can be from cervical spine level all the way to the sacral hiatus in the case of a caudal epidural block. Catheter insertion means doses can be repeated and the effect maintained. This contrasts with the typical single-shot spinal/subarachnoid injection primarily used for surgical anaesthesia. Specifically avoiding dural puncture also contrasts with the spinal's simple endpoint of detecting CSF. Accurate epidural needle insertion is therefore technically more difficult. The variety of methods available to identify if the needle tip is in the epidural space highlights this much less certain endpoint. With epidural injections, drug solutions need to physically spread to access each intended nerve root. This makes epidurals less reliable than spinals, where simply depositing the solution in the CSF rapidly enables it to bathe all the nerve roots encountered. Serious risks such as direct damage to nerve tissue, infection and epidural haematoma are shared with spinal anaesthesia but may be more likely with epidural techniques. Epidural needles are wider bore and more likely to damage tissue and vessels. They are sometimes directed close to the spinal cord itself. In-dwelling catheters can move and traumatize vessels and act as a focus for infection. Despite these potential drawbacks, careful selection, skilled placement and management mean patients can safely derive the intended benefits and epidurals and caudal blocks continue to be popular.     

Techniques of epidural block

Epidural blocks are used for relief of chronic pain, labour pain and postoperative pain as well as for surgical anaesthesia. The effect can be targeted at the insertion level which can be from cervical spine level all the way to the sacral hiatus in the case of a caudal epidural block. Catheter insertion means doses can be repeated and the effect maintained. This contrasts with the typical single-shot spinal/subarachnoid injection primarily used for surgical anaesthesia. Specifically avoiding dural puncture also contrasts with the spinal’s simple endpoint of detecting CSF. Accurate epidural needle insertion is therefore technically more difficult. The variety of methods available to identify if the needle tip is in the epidural space highlights this much less certain endpoint. With epidural injections, drug solutions need to physically spread to access each intended nerve root. This makes epidurals less reliable than spinals, where simply depositing the solution in the CSF rapidly enables it to bathe all the nerve roots encountered. Serious risks such as direct damage to nerve tissue, infection and epidural haematoma are shared with spinal anaesthesia but may be more likely with epidural techniques. Epidural needles are wider bore and more likely to damage tissue and vessels. They are sometimes directed close to the spinal cord itself. In-dwelling catheters can move and traumatize vessels and act as a focus for infection. Despite these potential drawbacks, careful selection, skilled placement and management mean patients can safely derive the intended benefits and epidurals and caudal blocks continue to be popular.     

Force exerted by epidural catheters

In a study of epidural catheters, it was found that catheter material and catheter diameter both influenced in force exerted. Catheters made of nylon exert less force than those made of polyethylene. Diameter is proportional to the logarithm of force exerted.     

The severance of epidural catheters

Four groups of Portex Minipack epidural sets were tested to measure the force required to sever the catheter on the needle bevel. The 18-gauge radio-opaque catheter was found to sever at a significantly lower applied force and to stretch significantly less before breaking than the 18-gauge clear catheter or either of the 16-gauge catheters. The other catheters tested had breaking strains of between 10-20 Newtons (1-2 kg force) and stretched by more than 30% of their lengths before breaking. It is suggested that these other catheters may therefore be a preferable alternative to the 18-gauge radio-opaque.     

Evaluation of thoracic epidural catheter position and migration using radio-opaque catheters

Migration of thoracic epidural radio-opaque catheters was evaluated in 25 patients scheduled for thoracic surgery in the supine position (n = 5) or in the lateral position with lateral extension of the thoracic spine ( n  =20). Chest radiography was performed daily for 3 days after operation. Eighty-nine per cent of catheter tips were visualised in the epidural space. The catheter tip position was unchanged in all patients operated upon in the supine position. In the group operated upon in the lateral position, the catheter tip retracted from day 1 to day 2 by an average of 0.69 cm (SD 1.08; p <0.05); from day 2 to day 3 the average retraction was 0.35 cm (SD 0.67; p <0.05).     

Differential flow from multihole epidural catheters

The pressures used in vivo to administer epidural doses of local anaesthetic were recorded for 16- and 18-gauge multihole catheters. Observations were made on 10 patients in labour for each catheter gauge. The pressure range for the 16-gauge catheters was 39.9-266 kPa, with a mean of 167.2 kPa, and for 18-gauge, a range of 53.2-266 kPa, mean, 159 kPa. Similar pressures were then applied in vitro to 10 catheters of each gauge, and the flow of fluid observed from the three holes. For each size of catheter, with increasing pressure, flow appeared at the proximal, then the middle, and finally the distal hole. This emphasises that the effect of epidural doses can vary depending on the pressure of injection, especially if the catheter had been passed partially through the dura.     

Thoracic epidural catheters via the caudal and lumbar approaches using styletted multiple port catheters in pediatric patients: a report of three cases

Advancing catheters from the lumbar and caudal epidural spaces to the thoracic level has been reported to be an alternative to the direct thoracic approach. However, as children grow, the threading of catheters in the epidural space becomes increasingly difficult. This report describes three cases of thoracic epidural placement using a multiport catheter threaded from the caudal and lumbar spaces using electrical stimulation guidance. In the first case, a multiport catheter was threaded 22 cm from the lumbar space to T8 following a failed attempt with a single-port catheter in a 9-year-old boy scheduled to undergo a right nephrectomy. In the second case, a multiport catheter was threaded 26 cm from the caudal space to T9 in a 3-year-old girl undergoing fundoplication. In the last case, a multiport catheter was inserted at the completion of a fundoplication in a 2-year-old girl after it had been confirmed that the single-port catheter inserted prior to surgery had not advanced to the desired thoracic level. The multiport catheter was threaded 17 cm without resistance from the caudal space to T9. In all cases, electrical stimulation was used to confirm the location of the catheter tip at the time of insertion. The position of the catheters was later confirmed by X-ray. The multiport catheter incorporates a stylet, which extends to a closed distal tip, within a catheter body that ejects fluid from three lateral holes in a direction perpendicular to the advancing catheter. These properties may facilitate the reliable advancement of catheters in the epidural space.     

Epidural abscess complicating insertion of epidural catheters

We present three cases of epidural abscess, all in patientsin whom an epidural catheter had been inserted for postoperativepain management. In all three cases the infecting organism wasStaphylococcus aureus and two patients had diabetes. The diagnosiswas made within 3 days of epidural catheter removal in two cases,but in one the abscess did not present until after the patienthad been discharged from hospital. We have retrospectively calculatedthe incidence of epidural abscess in our hospital over the 5-yrperiod 1993–98 to be 1 in 800 (0.12%). We emphasize theimportance of using techniques that minimize the risk of bacterialcontamination during both catheter placement and the managementof infusion, and seek to raise awareness of this relativelyrare but significant condition. Br J Anaesth 2002; 89: 778–82     

A study of epidural pressures in infants

BACKGROUND: The pressures exerted on fragile structures in the infant during epidural injections have never been studied previously. METHODS: We measured the pressure changes in the epidural space of 20 infants during injection of local anaesthetic solutions. The pressures developed during passage of the epidural needle through the ligaments of spine and in the epidural space during the injection of 1 ml at two rates of injection, over 1 and 2 min and the residual pressure 1 and 2 min after each injection were studied. RESULTS: The mean pressure while the needle was being advanced through the ligamentum flavum was 69.14 +/- 36.95 mmHg. The epidural pressure after needle had just penetrated the ligament without eliciting the loss of resistance was 1 +/- 9.759 mmHg. A distinct pulsatile waveform identical to the pulse waveform was observed as soon as the epidural space was entered. The pressure rise varied according to the rate of injection. The pressures were 27.79 mmHg when the rate of injection was 1 ml.min(-1), with a residual pressure after 1 min of 12 +/- 5.53 mmHg and 10.14 +/- 5.53 mmHg after 2 min of injection. When the rate of injection was 1 ml.2 min(-1), the pressures were 15.66 +/- 9.48 mmHg with a residual pressure after 1 min of 14.79 +/- 5.15 mmHg and 12.93 +/- 5.46 mmHg after 2 min of injection. CONCLUSIONS: The residual pressures seem to vary more with the volume injected than the rate of injection or the pressures developed during the injection. The relationship between the rate of injection and pressures is significant when compared with adults where the pressures have been measured after an injection rate of 1 ml.s(-1) and 1 ml.5 s(-1). This is a very fast rate compared with our rates of injection of 1 ml over 1 and 2 min. Based on the findings of this study, we recommend a rate of 1 ml.2 min(-1) in infants. In neonates, a slower rate of injection would be preferable.