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Summary Caudal epidural blockade in children is one of the most widely administered techniques of regional anaesthesia. Recent clinical studies have answered major pharmacodynamic and pharmacokinetic questions, thus providing the scientific background for safe and effective blocks in daily clinical practice and demonstrating that patient selection can be expanded to range from extreme preterm births up to 50 kg of body weight. This narrative review discusses the main findings in the current literature with regard to patient selection (sub-umbilical vs mid-abdominal indications, contraindications, low-risk patients with spinal anomalies); anatomical considerations (access problems, age and body positioning, palpation for needle insertion); technical considerations (verification of needle position by ultrasound vs landmarks vs ‘whoosh' or ‘swoosh' testing); training and equipment requirements (learning curve, needle types, risk of tissue spreading); complications and safety (paediatric regional anaesthesia, caudal blocks); local anaesthetics (bupivacaine vs ropivacaine, risk of toxicity in children, management of toxic events); adjuvant drugs (clonidine, dexmedetomidine, opioids, ketamine); volume dosing (dermatomal reach, cranial rebound); caudally accessed lumbar or thoracic anaesthesia (contamination risk, verifying catheter placement); and postoperative pain. Caudal blocks are an efficient way to offer perioperative analgesia for painful sub-umbilical interventions. Performed on sedated children, they enable not only early ambulation, but also periprocedural haemodynamic stability and spontaneous breathing in patient groups at maximum risk of a difficult airway. These are important advantages over general anaesthesia, notably in preterm babies and in children with cardiopulmonary co-morbidities. Compared with other techniques of regional anaesthesia, a case for caudal blocks can still be made.

Catheter-related infections are a serious complication of continuous thoracic epidural analgesia. Tunnelling catheters subcutaneously may reduce infection risk. We thus tested the hypothesis that tunnelling of thoracic epidural catheters is associated with a lower risk of catheter-related infections.Twenty-two thousand, four hundred and eleven surgical patients with continuous thoracic epidural analgesia included in the German Network for Regional Anaesthesia registry between 2007 and 2014 were grouped by whether their catheters were tunnelled (n=12 870) or not (n=9541). Catheter-related infections in each group were compared with Student's unpaired t and χ(2) tests. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated with logistic regression, adjusting for potential confounding factors, including age, ASA physical status score, use of catheter for ≥4 days, multiple skin puncture, hospital, and surgical department.There were fewer catheter-related infections in patients with tunnelled catheters (4.5 vs 5.5%, P0.001). Mild infections were also less common (4.0 vs 4.6%, P=0.009), as were moderate infections (0.4 vs 0.8%, P0.001). After adjustment for potential confounding factors, tunnelling remained an independent prevention for any grade of infection (adjusted OR 0.51, 95% CI 0.42-0.61, P0.001) and for mild infections (adjusted OR 0.54, 95% CI 0.43-0.66, P0.001) and moderate and severe infections (adjusted OR 0.44, 95% CI 0.28-0.70, P=0.001).Tunnelling was associated with a lower risk of thoracic epidural catheter-related infections.

Background Local anaesthetics are commonly delivered to the epidural space by either intermittent bolus or continuous infusion. While these methods have been investigated in terms of analgesia and total dose administered, they have not been compared in terms of their effect on the spread of injectate within the epidural space. This animal study compared the spread of dye delivered to the epidural space in a porcine model by either bolus or infusion. Methods After ethical approval, epidural catheters were placed at three vertebral levels in seven anaesthetized pigs. Aqueous dye (1 ml) was injected into the catheter as a bolus, or as an infusion over 30 min. Animals were euthanized at the end of the study and necropsy performed immediately to quantify the extent of dye spread. Results In seven animals, 20 catheters were successfully placed in the epidural space. The mean (sd) extent of dye spread was 8.9 (2.6) cm in the infusion group compared with 15.2 (2.7) cm in the bolus group (P Conclusion In the porcine epidural model, spread of one ml of epidural dye solution is more extensive after a single bolus compared with short term infusion.

The different methods of cervical epidural injection include the median or paramedian interlaminar (PI) approach and the transforaminal (TF) approach. We hypothesized that the modified PI (mPI) approach could deliver drugs suitably and safely into the anterior epidural space compared with the TF approach.A total of 62 patients were randomized into either the mPI group (n=31) or the TF group (n=31). Contrast to the anterior epidural space (primary outcome, grade 1-3), vascular uptake and discomfort were assessed. Furthermore, pain intensity in the arm and neck [numeric rating scale (NRS)] and the degree of symptoms (5-point Likert scale) before the procedure and 2 weeks, 1 and 3 months following the procedure were compared between two groups. Effectiveness (a secondary outcome) was defined as a ≥50% reduction on the NRS for arm and neck pain and a result of 3 or 4 on the Likert scale at 3 months following the procedure.Contrast to the anterior epidural space in the mPI group was significantly greater than that in the TF group (P=0.036). Vascular uptake and discomfort in the mPI group were significantly lower than those in the TF group (P0.001, respectively). Of the patients in whom the procedure was effective, 24 (77.4%) were from the mPI group and 20 (64.5%) were from the TF group (P=0.263).This result suggests that the mPI approach allows for suitable and safe delivery of drugs into the anterior epidural space.Institutional Review Board of Seoul National University Bundang Hospital (B-1206/159-004) and Clinical Research Information Service (KCT0000626).

Background The primary aim of this study was to objectively assess the different spinal and caudal volumes that are of interest for caudal block volume dosing. Methods Three directly assessed (volume of spinal canal/caudal space, volume of the dural sac and volume of spinal cord) and two derived volumes (volume of the epidural space and cerebrospinal fluid volume) were determined from magnetic resonance images (MRI) in 20 children (zero - three yr of age). The assessed volumes were correlated to age, height and weight. Furthermore, the volumes of the epidural space from caudal canal to three different clinically relevant target levels (L 1, Th 10 and Th 6) and the epidural volume of each individual spinal segment at the caudal, lumbar and thoracic levels were calculated. Results All volumes correlated in a linear manner to length and weight (R2 0.614 – 0.867) whereas a curvilinear correlation was associated with best curve fit for age (R2 0.696 – 0.883). The median volumes of the epidural space from caudal canal to L 1, Th 10 and Th 6 were 1.30 ml kg−1 (95%CI 1.08-1.51), 1.57 ml kg−1 (95%CI 1.29-1.81) and 1.78 ml kg−1 (95%CI 1.52-2.08), respectively. The median volumes of the epidural space per vertebral segment were Thoracic: 0.60 ml (95%CI 0.38-0.75); Lumbar: 1.18 ml (95%CI 0.94-1.43) and Caudal: 0.85 ml (95%CI 0.56-1.18). Conclusions The spinal volumes of interest show a linear correlation to height and weight whereas a curvilinear correlation was found for age. The volume of the epidural space per segment was found to be significantly higher at the lumbar level compared with the caudal and thoracic levels.

Background Despite being increasingly used for pain management, only two studies, with controversial results, have evaluated the epidural use of oxycodone. Methods Twenty-four women, aged 26–64 yr, undergoing elective gynaecological surgery were enrolled in this randomized, double-blinded, parallel group study. The subjects were administered either i.v. oxycodone and epidural placebo (IV group; n=12) or epidural oxycodone and i.v. placebo (EPI group; n=12) after operation. Oxycodone was administered as a single dose of 0.1 mg kg−1. An epidural catheter for drug administration was placed at T12/L1 and a spinal catheter for cerebrospinal fluid (CSF) sampling at L3/4. Plasma and CSF were frequently collected for the analysis of oxycodone and its major metabolites. The primary outcomes were the peak concentration (Cmax), time to peak concentration (Tmax), and the exposure (AUClast) of oxycodone in CSF and plasma. The secondary outcome was the analgesic efficacy, measured as the total dose of rescue fentanyl during the first four postoperative hours. Results In the EPI group, the median oxycodone Cmax and AUClast in the CSF were 320- and 120-fold higher, respectively, compared with the IV group. The total dose of rescue fentanyl was significantly lower in the EPI group (seven subjects needed 16 doses) than in the IV group [12 subjects needed 71 doses (P=0.001)]. No serious or unexpected adverse events were reported. Conclusions Epidural oxycodone provides much higher CSF concentrations and possibly better analgesic efficacy than does i.v. oxycodone. Clinical trial registration EudraCT reference number: 2011-000125-76.

Background Ultrasound guidance allows for the use of much lower volumes of local anaesthetics for nerve blocks, which may be associated with less aberrant spread and fewer complications. This randomized, controlled study used contrast magnetic resonance imaging to view the differential-volume local anaesthetic distribution, and compared analgesic efficacy and respiratory impairment. Methods Thirty patients undergoing shoulder surgery were randomized to receive ultrasound-guided interscalene block by a single, blinded operator with injection of ropivacaine 0.75% (either 20 or 5 ml) plus the contrast dye gadopentetate dimeglumine, followed by magnetic resonance imaging. The primary outcome was epidural spread. Secondary outcomes were central non-epidural spread, contralateral epidural spread, spread to the phrenic nerve, spirometry, ultrasound investigation of the diaphragm, block duration, pain scores during the first 24 h, time to first analgesic consumption, and total analgesic consumption. Results All blocks provided fast onset and adequate intra- and postoperative analgesia, with no significant differences in pain scores at any time point. Epidural spread occurred in two subjects of each group (13.3%); however, spread to the intervertebral foramen and phrenic nerve and extensive i.m. local anaesthetic deposition were significantly more frequent in the 20 ml group. Diaphragmatic paralysis occurred twice as frequently ( n +8 vs 4), and changes from baseline peak respiratory flow rate were larger [Δ+−2.66 (1.99 sd ) vs −1.69 (2.0 sd ) l min −1 ] in the 20 ml group. Conclusions This study demonstrates that interscalene block is associated with epidural spread irrespective of injection volume; however, less central (foraminal) and aberrant spread after low-volume injection may be associated with a more favourable risk profile. Clinical trial registration This study was registered with the European Medicines Agency (Eudra-CT number 2013-004219-36) and with the US National Institutes’ of Health registry and results base, clinicaltrials.gov (identifier NCT02175069).

Background Redistribution and secondary spread after the initial injection of local anaesthetics (LAs) are important factors that contribute to the final spread of caudal block in children. However, to date, these phenomena have yet not been studied in detail. Thus, the aim of this observational study was to define patterns of secondary spread and redistribution of a caudal block by means of real-time ultrasonography scanning and cutaneous testing. Methods Ultrasound assessment of LA spread within the caudal–epidural space and epidural pressure was followed during 15 min after initial injection (1.5 ml kg−1, ropivacaine 0.2%) in 16 infants. At 15 min post-injection, cutaneous testing was also performed to assess the cranial dermatomal level of the block (at end-tidal sevoflurane 2.5%). Results The median ultrasound-assessed cranial spread was Th10 and Th8 at 0 and 15 min, respectively, and the sensory level at 15 min was Th4. The caudal injection was initially found to compress the terminal part of the dural sac, later followed by a partial re-expansion as epidural pressure was returning towards pre-injection values. An intrasegmental redistribution from the dorsal to the ventral compartment of the epidural space was also observed. Conclusions Two separate patterns of secondary spread of caudal block could be observed, being horizontal intrasegmental redistribution and longitudinal cranial spread. The observed bi-directional movement of cerebrospinal fluid (coined ‘the CSF rebound mechanism') does explain a major part of the difference between the initial ultrasound-assessed cranial level and the final level determined by cutaneous testing.

Background. Incorrect placement of epidural catheters causes medical complications. We used linear discriminant analysis (LDA) to develop an intelligent recognition system (i-RS) in order to guide epidural placement and reduce physician error. Methods. We analysed real-time dual-wavelength fibreoptic data recorded from the end of an epidural needle in a live porcine model. Two categories of tissue layers were necessary for correct placement of catheter: epidural space and ligamentum flavum. The data were tested using linear, quadratic and logistic parametric analysis to identify which method could distinguish the two anatomical structures. Results. LDA was the best fit for our model. There was 80% sensitivity and specificity for correct anatomical identification. Error rates based on cross-validation were 17.0% for the epidural space and 18.6% for ligamentum flavum. Error rates were greater with the 532 nm compared with 650 nm wavelength. Conclusions. The sensitivity and specificity of LDA for identifying the correct anatomical structure was similar to a physician who is an expert in epidural placement. Overall performance of an i-RS could be improved by expanding the database for decision-making and adding a category of uncertainty. This would reduce complications caused by incorrect epidural placement.

Background Current methods of locating the epidural space rely on surface anatomical landmarks and loss-of-resistance (LOR). We are not aware of any data describing real-time ultrasound (US)-guided epidural access in adults. Methods We evaluated the feasibility of performing real-time US-guided paramedian epidural access with the epidural needle inserted in the plane of the US beam in 15 adults who were undergoing groin or lower limb surgery under an epidural or combined spinal–epidural anaesthesia. Results The epidural space was successfully identified in 14 of 15 (93.3%) patients in 1 (1–3) attempt using the technique described. There was a failure to locate the epidural space in one elderly man. In 8 of 15 (53.3%) patients, studied neuraxial changes, that is, anterior displacement of the posterior dura and widening of the posterior epidural space, were seen immediately after entry of the Tuohy needle and expulsion of the pressurized saline from the LOR syringe into the epidural space at the level of needle insertion. Compression of the thecal sac was also seen in two of these patients. There were no inadvertent dural punctures or complications directly related to the technique described. Anaesthesia adequate for surgery developed in all patients after the initial spinal or epidural injection and recovery from the epidural or spinal anaesthesia was also uneventful. Conclusions We have demonstrated the successful use of real-time US guidance in combination with LOR to saline for paramedian epidural access with the epidural needle inserted in the plane of the US beam.

Background No data for patients with failed back surgery syndrome (FBSS) based on the location of adhesions separated by epiduroscopic adhesiolysis have been reported. Methods We performed epiduroscopic adhesiolysis on 28 FBSS patients to examine the impact of differences in the locations of the separated regions on the treatment results. We performed fluoroscopic imaging through the sacral hiatus to assess the condition of adhesions in the epidural space during the post-adhesiolysis observation period. Results In patients in whom only the epidural space was separated by adhesiolysis, there was a significant improvement in the Roland–Morris disability questionnaire (RDQ) score until 12 weeks after adhesiolysis, but the score gradually returned to the preoperative value thereafter. Among patients in whom the nerve root responsible for radicular pain was separated, there was a long-term improvement in the RDQ, Oswestry disability index 2.0 (ODI), and Japanese Orthopedic Association Assessment of Treatment (JOA) scores. Among patients in whom both the epidural space and the nerve root responsible for pain were separated, there was a 12 week improvement in the RDQ score and 24 week improvements in the ODI and JOA scores. Conclusions Progressive epidural imaging after adhesiolysis suggested that pain was caused by re-adhesion around the nerve root. Since re-adhesion of the nerve root required some time, the effect of adhesiolysis was maintained for extended periods in these cases. We suggest that epiduroscopic adhesiolysis is an effective therapy for FBSS patients, and that adhesiolysis of the nerve root may exhibit the long-term (24 weeks) efficacy in patients with pain.

Epiduroscopy is a relatively new diagnostic and therapeutic technique used in patients with chronic low back pain with or without radiculopathy. We present our experience with a new interlaminar approach in patients with failed back surgery syndrome (FBSS).Patients with severe symptoms of FBSS who did not respond to other treatments were included. Lumbar epiduroscopy was performed via interlaminar approach through a 14 G epidural needle under fluoroscopy. A flexible, 0.77 mm, endoscope was introduced through a 4F catheter into the epidural space and advanced in a cephalad direction. Flushes of normal saline through the catheter (via a Y-adapter/haemostasis valve) enabled distension of the space. Adhesions were mechanically mobilized under direct vision. A mixture of triamcinolone 60 mg, hyaluronidase 600 IU, and bupivacaine 0.0625% was instilled.Nineteen patients were included. The mean number of operations at lumbar level was 2.26. Major findings included adhesions, inflammation, stenosis, and nerve root hypotrophia. The visual analogue scale (VAS) score was 7.89 at baseline, 5.95 (P0.001) 3 months later, and 6.05 (P0.001) 6 months later. Six patients (31.6%) did not show any improvement, and six other patients showed a very significant improvement (at least three points reduction in the VAS) 3 months later. We had four cases of dural puncture, but only one patient required hospital admission.We have described a new procedure for epiduroscopy with approximately 50% reduced outer diameter of the catheter, which allows interlaminar approach. Its diagnostic efficacy is clear and there were a significant number of patients who had improved outcome.

Background Uncertainty remains over the risk of epidural space infection after neuraxial blockade in the presence of systemic sepsis. For many years, we have provided epidural analgesia to children undergoing thoracotomy for the decortication of parapneumonic empyemas. Following recent publications asserting that epidural analgesia is absolutely contraindicated in this situation, we audited our management. The purpose of this audit was to document the effectiveness and the incidence of complications after epidural insertion in children with active sepsis from empyemas. Methods This is a retrospective single-centre audit over a 10-yr period. Results Forty-six epidurals were performed in children with empyema, and three children were treated with systemic opioids. We found no infective complications of the epidural space or insertion sites. The epidurals provided excellent analgesia. The incidence of moderate–severe pain was 18%, and 2% for severe pain in the first 24 h after surgery. Minor complications of epidural analgesia were uncommon. Two children receiving systemic opioids for pain relief suffered respiratory complications, one of which resulted in a prolonged admission to the intensive care unit. Conclusions Epidural analgesia provides excellent pain relief after thoracotomy in children with empyema, with a low complication rate. Until evidence to the contrary emerges, it remains our technique of choice for thoracotomy, even in the presence of empyema.

Background Thoracic epidural catheters are used for anaesthesia and postoperative analgesia. Usually, epidural catheters are placed without confirmation of their position despite frequent reports of complications as a result of malposition. In this study, we evaluated the threading length of thoracic epidural catheters without coiling and assessed the influence of two different epidural approach angles on the threading length without coiling. Methods Eighty-three patients scheduled for thoracotomy were enrolled and randomly allocated into the acute angle group and the obtuse angle group. In both groups, skin insertion was performed at the T8–9 intervertebra level. Epidural access was performed under fluoroscopy using a paramedian approach at the T7–8 level in the acute angle group and at the T6–7 level in the obtuse angle group, and an end-hole 19-gauge epidural catheter was inserted. Coiling length, defined as the length of the catheter within the epidural space when any part of the catheter just begins to head caudally, was measured in both groups. Results The coiling length was 7.4(4.4) cm (95% CI 6.0–8.7 cm) in the obtuse angle group compared with 4.9(3.3) cm (95% CI 3.8–6.0 cm) in the acute angle group (P = 0.005). Conclusions Approaching the thoracic epidural space with an obtuse approach angle provides longer coiling length. We recommend that an obtuse approach angle should be used to maximize the chance of the catheter reaching the intended level with minimum risk of coiling.

We report a prospective, randomized study to evaluate ultrasound guidance for epidural catheter placement in children 0-6 yr of age.Epidural catheters were placed at lumbar or thoracic cord levels in 64 children undergoing major surgery, using either ultrasonography or loss-of-resistance (LOR) for guidance. Using a 5-10 MHz linear ultrasound probe, the neuraxial structures were identified, the skin-epidural depth and epidural space was measured, the advancing epidural catheter visualized, and the spread of local anaesthetic verifying catheter position was confirmed. Epidural placement procedures were analysed for bone contacts and speed of execution. Children under 6 months were analysed separately.Epidural placement involved bone contacts in 17% of children in the ultrasound group and 71% of children in the LOR group (P0.0001). Epidurals were executed more swiftly in the ultrasound group [162 (75) s vs 234 (138) s; P0.01]. Children under 6 months revealed a 0.9 correlation between skin-epidural depth and body weight.Ultrasonography is a useful aid to verify epidural placement of local anaesthetic agents and epidural catheters in children. Advantages include a reduction in bone contacts, faster epidural placement, direct visualization of neuraxial structures and the spread of local anaesthetic inside the epidural space. Ultrasound guidance requires additional training and good manual skills, and should only be used once experience in ultrasound-guided techniques of regional anaesthesia has been acquired.

Background Lower thoracic epidural anaesthesia and analgesia (EDA) has gained increasing importance in perioperative pain therapy. The loss-of-resistance technique used to identify the epidural space is thought to rely on the penetration of the ligamentum flavum. Investigations at the cervical and lumbar regions have demonstrated that the ligamentum flavum frequently exhibits incomplete fusion at different vertebral levels. Therefore, the aim of this study was to directly investigate the incidence of lower thoracic ligamentum flavum midline gaps in embalmed cadavers. Methods Vertebral column specimens were obtained from 47 human cadavers. Ligamentum flavum midline gaps were recorded between the vertebral levels T6 and L1. Results The incidence of midline gaps/number of viable specimens at the following levels was: T6–7: 2/45 (4.4%), T7–8: 1/47 (2.1%), T8–9: 2/45 (4.4%), T9–10: 7/39 (17.9%), T10–11: 12/34 (35.2%), T11–12: 10/35 (28.5%), T12/L1: 6/38 (15.8%). Conclusions In the present study we have determined the frequency of lower thoracic ligamentum flavum midline gaps. Gaps are less frequent than at cervical levels, but more frequent than at lumbar levels. Peak incidence was found in the region between T10 and T12. Using a strict midline approach, one cannot therefore rely on the ligamentum flavum to impede entering the epidural space in all patients.

Background. Chronic sciatica can be managed by caudal steroid epidural or by targeted steroid placement during spinal endoscopy. Spinal endoscopy is a new unproven procedure. We aimed to compare the two pain management techniques and to investigate whether the site of steroid placement within the epidural space was significant. Methods. We randomized 60 patients with a 6‐18 months history of sciatica to either targeted epidural local anaesthetic and steroid placement with a spinal endoscope or caudal epidural local anaesthetic and steroid treatment. Pre-treatment and 6-week, 3-month, and 6-month SF-MPQ and HAD scores were recorded. Results.Nosignificantdifferenceswere foundbetweenthe groupsforanyofthe measuresatany time. However, there were significant differences within both groups compared with pretreatment values. For the caudal group, significant improvements were found for descriptive pain at 6 months (P=0.031), VAS at 6 weeks (P=0.036), 3 months (P=0.026), and 6 months (P=0.003), present pain intensity (PPI) at 3 months (P=0.013) and 6 months (P=0.01); anxiety at 6 weeks (P=0.008), 3 months (P=0.004), and 6 months (P=0.001) and depression at 6 months only (P=0.037). For the epiduroscopy group there were fewer significant changes. PPI was significantly reduced at 6 weeks (P=0.004) and at 6 months (P=0.02). Anxiety was reduced at 6 months only (P=0.03). Conclusion. The targeted placement of epidural steroid onto the affected nerve root causing sciatica does not significantly reduce pain intensity and anxiety and depression compared with untargeted caudal epidural steroid injection. When analysed individually, both techniques benefited patients.

BACKGROUND The posterior longitudinal ligament (PLL) has been found to be a reliable measure of the acoustic target window for lumbar spinal anaesthesia and a predictive tool for difficult spinals. Currently, there is limited information on the PLL in the thoracic spine and its potential use for optimizing the acoustic target window during thoracic epidural placement. This study examined the effects of changes in body position on the length of the PLL as a measure of the acoustic target window for paramedian thoracic epidural access. METHODS We performed thoracic ultrasonography on 30 adult volunteers to measure the length of the PLL at the T9/10 interspace, in five different positions: P1, neutral; P2, thoracic and lumbar flexion; P3, as in position 2 with dorsal table tilt to 10°; P4, as in position 2 with 45° rightward shoulder rotation; and P5, as in position 2 with 45° leftward shoulder rotation. RESULTS The mean (sd) PLL length increased significantly from 9.9 (3.9) mm in P1 to 11.7 (3.4) mm in P2, 12.9 (3.1) mm in P3, and 13.8 (4.0) mm in P4 (P

Epidural anaesthesia is an important analgesia technique for obstetric delivery. During pregnancy, however, obesity and oedema frequently obscure anatomical landmarks. Using ultrasonography, we investigated the influence of these changes on spinal and epidural anatomy. We examined 53 pregnant women who were to receive epidural block for vaginal delivery or Caesarean section. The first ultrasound imaging was performed immediately before epidural puncture; the follow-up scan was done 9 months later. The ultrasound scan of the spinal column was performed at the L3/4 interspace in transverse and longitudinal planes, using a Sonoace 6000 ultrasonograph (Kretz, Marl, Germany) equipped with a 5.0-MHz curved array probe. We measured two distances from the skin to the epidural space: the minimum (perpendicular) and the maximum (oblique) needle trajectory. The quality of ultrasonic depiction was analysed by a numerical scoring system. An average weight reduction of 12.5 kg had occurred by the follow-up examination. During pregnancy, the optimum puncture site available on the skin for epidural space cannulation was smaller, the soft-tissue channel between the spinal processes was narrower, and the skin-epidural space distance was greater. The epidural space was narrower and deformed by the tissue changes. The visibility of the ligamentum flavum, of the dura mater and of the epidural space decreased significantly during pregnancy. Nevertheless, ultrasonography offered useful pre-puncture information. Thus far, palpation has been the only available technique to facilitate epidural puncture. Ultrasound imaging enabled us to assess the structures to be perforated. We anticipate that this technique will become valuable clinically.

The lumbar epidural region was studied using computerized tomography. This technique allows examination of the region in vivo. It confirmed that the spinal canal is oval in the upper lumbar region, becoming triangular lower down, and that the ligamenta flava form a posterior recess to the vertebral canal. Epidural fat is confined to this region between the ligamenta flava and the intervertebral foramina, and the dura mater lies apposed to the walls of the vertebral canal except where there is epidural fat. The absence of a posterior midline fold of dura mater was noted, and discussed in the light of other studies.

We examined the extradural space using a flexible extraduroscope in 113 patients undergoing extradural anaesthesia. Patients were classified into two groups to receive either thoracic or lumbar extradural anaesthesia as needed for perioperative analgesia. The extraduroscopy showed that the thoracic extradural space becomes widely patent after injecting a given amount of air and that the amount of fatty and fibrous connective tissue is less in the thoracic extradural space compared with the lumbar extradural space. We suggest that differences between the structure of these two vertebral regions may affect the spread of local anaesthetics in the extradural space.

To clarify the anatomy of the extradural space of the thoracic spine, we have compared magnetic resonance (MR) images of the thoracic spine with those of the lumbar spine. In 20 healthy volunteers, T2-weighted axial MR images were obtained at the levels of the C7-T1, T7-8, T11-12 and L2-3 vertebrae. The posterior extradural space seen in the slice through the intervertebral disc varied in shape and size depending on the vertebral level, and the shape of the space converted from triangular to crescent-shaped on moving from the lumbar to the thoracic spine. In particular, the posterior extradural space was almost absent at the C7-T1 level, indicating that the posterior extradural fat was rudimentary or non-existent at the thoracocervical level. At this level, the dura mater seemed to be in direct contact with the ligamentum flavum. Segmentation of the posterior extradural space was commonly observed at the L2-3 and T11-12 levels; however, incomplete segmentation of the posterior extradural space was often present at the T7-8 level.

We have studied, in 37 adult patients, the anatomy of the sacral extradural (caudal) space using magnetic resonance imaging. The sacrococcygeal membrane (SCM) could not be detected in 10.8% of patients. The maximum depth of the caudal space adjacent to the SCM was beneath the upper third of the SCM in more than 90% of patients (mean depth 4.6 mm; range 1.0-8.0 mm). The shortest linear distance from the dura to the upper limit of the SCM varied considerably (60.5 mm; 34-80 mm) as did the volume of the caudal space excluding the foraminae and dural sac (14.4 cm3; 9.5-26.6 cm3). The dimensions of the caudal space and their variability have implications for clinical practice and a knowledge of these dimensions may increase both the reliability and safety of caudal techniques in adult patients.

pharmacokinetic properties of methadone given by i.v. or epidural routeswerecomparedina rat model of thermal nociception. † Although pharmacokinetically similar, epidural methadone was a more effective analgesic than i.v. methadone. Background.Thepropertiesofmethadonesuggestapotentialadvantageforepiduraloveri.v. administration for pain relief, but little supportive evidence exists. Methods. To investigate the pharmacokinetic and the pharmacodynamic properties of epidural and i.v. methadone, four doses of methadone (0.1, 0.25, 0.5, and 0.75 mg kg 21 ) were investigated by each route in a rat model. The tail-flick and hot water tail immersion test were used for thermal nociception. The magnitude of antinociceptive efficacy was expressed as per cent maximal possible effect (%MPE) of tail withdrawal latency, and the area under the %MPE vs time curve indicated the cumulative antinociceptive effect. A pharmacokinetic model describing the disposition and elimination of methadone was established. Results. The pharmacokinetic profiles of methadone were not significantly different after epidural and i.v. administration. A two-compartment model with saturable elimination provided a good fit of the experimental data. At equivalent doses, epidural methadone produced higher cumulative antinociceptive effect in both thermal models. Supraspinal opioid effect, assessed by pinna reflex presence, was significantly lower with epidural methadone at equivalent doses. The duration of antinociceptive effect was longer with epidural administration of 0.5 and 0.75 mg kg 21 doses. Conclusions. Epidural administration of methadone in rats resulted in systemic exposure similar to that after i.v. administration, but improved thermal antinociceptive efficacy, and reduced supraspinal undesired effects. The findings suggest the presence of local effect at the spinal cord level, in addition to the systemic effect produced by epidural methadone.

We have assessed cephalad spread of analgesia in 491 patients undergoing extradural anaesthesia at the L2-3 or L3-4 interspace. Patients were classified into one of three groups based on the number of previous lumbar extradural anaesthesia procedures: none (group I, n = 339), one (group II, n = 82), and two or more (group III, n = 70). Cephalad spread of analgesia was greater in group I than in groups II and III, regardless of the puncture site. In addition, we examined the extradural space using a flexible extraduroscope in 32 patients who were excluded from the analysis of spread. Extraduroscopy showed the extradural space to be patent in patients with no history of prior lumbar extradural anesthesia, but it was not clearly identified in patients who had received extradural anaesthesia one or more times because of aseptic inflammatory changes, including proliferation of connective tissue, adhesions between the dura mater and the ligamentum flavum, granulation and changes in the ligamentum flavum. Extradural anaesthesia may cause aseptic inflammatory changes in the extradural space which may reduce the spread of analgesia.

To clarify pregnancy-induced changes in soft tissue anatomy within the vertebral canal, we have studied magnetic resonance (MR) images of the lumbar spine in three women. In each subject, T2-weighted axial MR images were obtained both before pregnancy and at 32 weeks' gestation, and the paired images were compared. The extradural venous plexus was engorged significantly in supine parturients. In addition, the engorged extradural venous plexus displaced the dura away from the wall of the vertebral canal in a posterior direction, which resulted in a decrease in the volume of the cerebrospinal fluid in the dural sac. These findings confirmed the long-held concept that the engorged extradural venous plexus in supine parturients decreases the effective capacity of the extradural and subarachnoid spaces.

It may be clinically useful to predict the depth of the epidural space.To investigate the accuracy of preoperative abdominal computed tomography (CT) in prediction of the distance for low-thoracic epidural insertion, a single group observational study was conducted in 30 male patients undergoing elective major abdominal surgery requiring epidural analgesia for postoperative pain relief. Using the paramedian approach, low-thoracic epidural insertion at T10-11 interspace was performed with a standardized procedure to obtain an actual insertion length (AIL). According to the principles of trigonometry, an estimated insertion length (EIL) was calculated as 1.26 times the distance from skin to epidural space measured from the preoperative abdominal CT.The mean (SD) EIL and AIL were 5.5 (0.7) and 5.1 (0.6) cm, respectively, with a significant correlation (r=0.899, P0.01). The EIL tended to have a higher value than the AIL (0.4 (0.3) cm). There were significant correlations of both EIL and AIL with weight (P0.01), BMI (P0.01), and body fat percentage (P0.01), but not with height (P0.05).We conclude that the preoperative abdominal CT is helpful in prediction of the distance for low-thoracic epidural insertion using the paramedian approach.

We present an unusual complication of left internal jugular vein catheterization in an 11-week-old infant which we believe has not been described previously. After failed subclavian catheterization, a left internal jugular catheter was placed without apparent difficulty. Confirmatory chest x-ray revealed that the tip of the catheter was in the extradural space.

Background Despite caudal blockade being the most widely used regional anaesthetic procedure for infants and children undergoing subumbilical surgery, the question whether the injection velocity of the local anaesthetic itself affects its spread in the epidural space has not yet been investigated. Thus, the aim of the present study was to measure the cranial spread of caudally administered local anaesthetics in infants and children by means of real-time ultrasonography, with a special focus on comparing the effect of using two different speeds of injection. Methods Fifty ASA I–II infants and children, aged up to 6 yr, weighing up to 25 kg, undergoing subumbilical surgery, were enrolled in this prospective, randomized, observer-blinded study. Caudal blockade was performed under ultrasound observation using ropivacaine 1 ml kg−1 0.2% or 0.35% and an injection given at either 0.25 ml s−1 or 0.5 ml s−1, respectively. Results Ultrasound observation of the local anaesthetic flow and the extent of cranial spread was possible in all patients. All caudal blocks were considered successful, and all surgical procedures could be completed without any indications of insufficient analgesia. No statistically significant difference could be observed between the two injection speeds regarding the cranial spread of the local anaesthetic in the epidural space. Conclusions The main finding of the present study is that the speed of injection of the local anaesthetic does not affect its cranial spread during caudal blockade in infants and children. Therefore, the prediction of the cranial spread of the local anaesthetic, depending on the injection speed, is not possible.

Specially selected soft Macintosh balloon indicators were attached to needles during five extradural and five spinal punctures. When the needle point entered the extradural space, the mean balloon pressure decreased suddenly from 24.9 (range 14-37) to 12.3 (10-16) mm Hg in the five extradural punctures and from 22.3 (17-28) to 13.7 (10-17) mm Hg in the five spinal punctures. In the five spinal punctures, the balloon pressure did not alter when the needle was advanced from the extradural to the subarachnoid space. Contrary to expectation, none of the balloons deflated when the needle point entered the extradural or subarachnoid spaces. The balloon pressure varied rhythmically in synchrony with respiration and cardiac pulsations. The final balloon pressure, extradural space pressure and subarachnoid pressure were equal. The results suggest that the extradural pressure is positive and of the same magnitude as the prevailing lumbar cerebrospinal fluid pressure. Jugular venous compression, ventilation with carbon dioxide and positive end-expiratory pressure (PEEP) produce a rapid increase in cerebrospinal fluid (CSF) pressure. These stimuli also produced a measurable increase in the lumbar extradural pressure. Jugular venous compression increased the mean lumbar extradural pressure by 6.8 (3-10) mm Hg and ventilation with carbon dioxide increased it by 10 (5-12.5) mm Hg. PEEP values of 5, 10, 15 and 20 cm H2O produced an immediate increase in extradural pressure of 1-2 mm Hg for every 5 cm H2O of PEEP. The lumbar extradural pressure increased rapidly with stimuli known to increase CSF pressure. Changes in spinal CSF pressure may be detected by measuring extradural pressure.

Background Despite the large amount of literature on caudal anaesthesia in children, the issue of volume of local anaesthetics and cranial spread is still not settled. Thus, the aim of the present prospective randomized study was to evaluate the cranial spread of caudally administered local anaesthetics in children by means of real-time ultrasound, with a special focus on the effects of using different volumes of local anaesthetics. Methods Seventy-five children, 1 month to 6 yr, undergoing inguinal hernia repair or more distal surgery were randomized to receive a caudal block with 0.7, 1.0, or 1.3 ml kg −1 ropivacaine. The cranial spread of the local anaesthetic within the spinal canal was assessed by real-time ultrasound scanning; the absolute cranial segmental level and the cranial level relative to the conus medullaris were determined. Results All the blocks were judged to be clinically successful. A significant correlation was found between the injected volume and the cranial level reached by the local anaesthetic both with regards to the absolute cranial segmental level and the cranial level relative to the conus medullaris. Conclusions The main finding of the present study was positive, but numerically small correlation between injected volumes of local anaesthetic and the cranial spread of caudally administered local anaesthetics. Therefore, the prediction of the cranial spread of local anaesthetic, depending on the injected volume of the local anaesthetic, was not possible. EudraCT Number: 2008-007627-40

We have studied magnetic resonance images of the lumbar spine of 39 subjects to examine the anatomy of the lumbar extradural region. The segmental nature of the posterior extradural region at each lumbar level may explain reports of easier cranial passage of extradural catheters introduced by the paramedian approach. This approach may thus provide a more reliable route for rapid introduction of an extradural catheter during the needle-through-needle, combined spinal-extradural technique. (Br. J. Anaesth. 1993; 71: 495–498)

We have studied the effects of extradural administration of 2% lignocaine at the L3–4 interspace on somatosensory evoked potentials recorded in the cervical extradural space before corrective surgery for idiopathic adolescent scoliosis. Eight patients in whom the equivalent volume of 0.9% sodium chloride solution was administered into the lumbar extradural space acted as a control group. Lignocaine, 2 % resulted in a decrease in overall amplitude, but its main effect was a significant decrease in the amplitude of the second and third peaks, suggesting an action on the dorsal columns of the spinal cord. A significant increase in latency was found in both the lignocaine and sodium chloride groups. We conclude that the use of extradural 2% lignocaine in patients undergoing scoliosis surgery may interfere with the intraoperative monitoring of somatosensory evoked potentials.

We have studied the effect of extradural compliance and extradural resistance on the spread of extradural analgesia. In 111 patients aged 21-75 yr, compliance and resistance of the extradural space were calculated by a mathematical analysis (using the Windkessel theory) of the extradural pressure-response curve to injection of a given volume of local anaesthetic. The calculated mean extradural compliance was 0.39 (SD 0.13) ml mm Hg-1 and this increased with advancing age (P less than 0.01). The total number of analgesic segments blocked was related to extradural compliance (P less than 0.01). Segmental dose requirement was related inversely to extradural compliance (P less than 0.01). Calculated extradural resistance was 26.8 (14.5) mm Hg s ml-1 and this decreased with advancing age (P less than 0.05). The total number of analgesic segments blocked was related inversely to extradural resistance (P less than 0.05). Segmental dose requirement was related to extradural resistance (P less than 0.05).

Background Local vasoconstriction induced by epinephrine added to epidural local anaesthetics has been shown to improve their quality and duration of action in several clinical reports. There are several assumptions on the mechanisms. This study was designed to evaluate the influence of epinephrine on transmeningeal uptake of epidurally administered ropivacaine and bupivacaine by measuring local anaesthetic concentrations in the epidural and intrathecal spaces and in plasma. Methods Ropivacaine (50 mg) and bupivacaine (30 mg) were administered epidurally in sheep with and without epinephrine (75 µg). A microdialysis technique was used to simultaneously measure epidural and intrathecal drug concentrations. Resulting dialysate and plasma concentrations were used to calculate pharmacokinetic parameters for ropivacaine and bupivacaine. Results Co-administration of epinephrine decreased epidural clearance for ropivacaine [0.6 (sd 0.1) vs 0.4 (0.1) ml min−1] but not significantly for bupivacaine [1.2 (0.4) vs 0.8 (0.3) ml min−1]. The resultant increase in epidural area under the concentration–time curves (31% for ropivacaine and 52% for bupivacaine) was also observed in the intrathecal space (21% increase for ropivacaine and 37% for bupivacaine). There was no significant influence of epinephrine on ropivacaine plasma pharmacokinetics. Plasma Cmax for bupivacaine was decreased. Conclusions These results show that epinephrine decreases the clearance and distribution processes involved in epidural disposition of ropivacaine and bupivacaine, leading to an increased uptake into the intrathecal space with an apparent more pronounced effect for bupivacaine.

Background The technique of epidural volume extension (EVE) involves the injection of saline into the extradural space immediately following the intrathecal injection, as part of a combined spinal-epidural (CSE) anaesthetic. One of the suggested benefits of EVE is a reduction in local anaesthetic required. The aim of this study was to test this hypothesis by comparing the median effective doses (ED50) of hyperbaric bupivacaine with fentanyl 25 µg with and without EVE for Caesarean section. Methods Sixty women were randomized to receive either CSE anaesthesia with EVE (EVE group) or no EVE (NEVE group). Using a double-blinded, up-down sequential technique, varying doses of bupivacaine with fentanyl 25 µg were administered. ED50 was estimated from up-down reversals and probit regression. Results The ED50 for bupivacaine was similar and not significantly different in the two groups (5.1 mg in the EVE and 6.1 mg in the NEVE group; difference 1.0 mg, 95% CI −0.12 to 2.2, P=0.08). Conclusions This study illustrates that whilst low doses of intrathecal bupivacaine can be effectively used for Caesarean section, at such doses EVE does not appear to offer reliable or clinically relevant reductions in dosing with intrathecal bupivacaine.

Background. The physicochemical properties of diamorphine (3,6-diacetylmorphine) enhance its bioavailability compared with more lipid-soluble opioids when administered into the epidural space. However, the influence of concentration, volume or mass on the clinical efficacy of diamorphine is not known. Method. In this double-blind, randomized, prospective study, 62 women in active labour and ≤5 cm cervical dilatation were recruited to determine whether the mode of action of diamorphine in the epidural space is concentration-dependent. After insertion of a lumbar epidural catheter, patients received epidural diamorphine 3 mg either as a high-volume, low-concentration solution (group A) or a low-volume, high-concentration solution (group B). The concentration of diamorphine was determined by the response of the previous patient in the same group using up–down sequential allocation. Pain corresponding to the previous contraction was assessed using a 100-mm visual analogue score and effective analgesia was defined as ≤10 mm within 30 min of epidural injection. Results. There was no significant difference in EC50 for diamorphine between the groups: the difference was 15.0 μg ml−1 (95% CI −40.3 to 10.3). The EC50 for group A was 237.5 μg ml−1 (95% CI 221.2 to 253.8) and the EC50 for group B was 252.5 μg ml−1 (95% CI 232.2 to 272.8). The EC50 ratio was 0.95 (95% CI 0.87 to 1.06). The groups exhibited parallelism (P=0.98). The overall EC50 for all data was 244.2 μg ml−1 (95% CI 230.8 to 257.2). Conclusion. We conclude that diamorphine provides analgesia in labour by a concentration-dependent effect.

Background. Lumbar spinal stenosis causes various forms of back or leg pain, and is recognized with increasing frequency in elderly patients whose physical status is not always suitable for surgery. Epiduroscopy, a new, minimally invasive diagnostic and therapeutic technique, may be useful for pain relief in such patients. We investigated the epiduroscopic findings and immediate and long-term changes in back and leg pain after epiduroscopy in elderly patients with spinal stenosis. Methods. Patients with degenerative lumbar spinal stenosis (n=58, median age 71 yr) were divided into two groups based on presenting symptoms: a monosegmental group (n=34) and a multisegmental group (n=24). Each patient underwent epiduroscopy, and the findings were evaluated using visual analogue scales for low back and leg symptoms. Epiduroscopy included breaking down adhesions in the epidural space by injections of saline, and injection of steroids/local anaesthetic. Results. Epiduroscopy showed that the amount of fatty tissue and the degree of vascularity were greater in the monosegmental group than in the multisegmental group. Relief of low back pain was observed up to 12 months after epiduroscopy in both groups. Relief of leg pain was evident up to 12 months after epiduroscopy in the monosegmental group, and up to 3 months after epiduroscopy in the multisegmental group. None of the patients showed deterioration of motor or sensory deficits during follow-up. One patient was excluded from analysis because of accidental dural puncture during the procedure. Conclusions. The findings of epiduroscopy corresponded to the symptoms. Epiduroscopy may reduce low back and leg pain in elderly patients with degenerative lumbar spinal stenosis, particularly those with radiculopathy.

Morbidity after paediatric epidural anaesthesia is unusual. We report a case of transient nerve root irritation occurring after epidural analgesia for radical nephrectomy in a 6-yr-old boy who received a continuous infusion of bupivacaine 0.1%. The epidural catheter was inserted within the L2-L3 interspace under general anaesthesia. Several possible causes are discussed. Mechanical irritation of nerve roots by the epidural catheter in the epidural space is the most likely cause. Br J Anaesth 2004: 92: 146-8

We have investigated prospectively the incidence of bacterial contamination of 114 spinal and 20 epidural needles collected immediately after lumbar puncture of the subarachnoid or epidural space. Bacteriological examination revealed bacterial contamination of 24 (17.9%) of the needles, mainly coagulase-negative staphylococci (21; 15.7%) followed by yeasts (2; 1.5%), enterococcus (1; 0.8%), pneumococcus (1; 0.8%) and micrococcus (1; 0.8%). Our results suggest that even during aseptic puncture for lumbar anaesthesia, there is a significant rate of needle contamination.

We have compared skin to epidural space distance (SED) and tip to tip distance (TTD), a measure of posterior epidural space depth (PESD), in 40 patients with a 27-gauge Whitacre needle after identification of the epidural space using the hanging drop (HD) or loss of resistance (LOR) to air technique. After the LOR technique, TTD was found to be 2 mm greater than that after the HD technique, whereas SED was the same. We conclude that identification of the epidural space can be performed successfully with both techniques, but with a diminished risk of dural damage after LOR compared with the HD technique.

We report three previously healthy individuals, aged 19-40 yr, with co-existing infected lower limb cutaneous wounds, who developed, in all probability, spinal space infections complicating continuous extradural analgesia. As the number of patients with extradural catheters and large cutaneous wounds represents a small fraction of the total number of patients with extradural catheters, three cases of presumed spinal space infection over a 4-yr period suggests that extradural analgesia with a catheter technique in this clinical situation is unsafe.

Single, end-holed and multi-orifice extradural catheters were compared in terms of efficacy and complications when used for infusion of 0.1% bupivacaine during labour. In this study of 364 patients there was no difference in unilateral block after an initial bolus dose (18 (11.5%) for single, end-holed and 16 (10.9%) for multi-orifice catheters). Unilateral block recurred with seven (4.0%) single, end-holed and with eight (4.8%) multi-orifice catheters. Unilateral blocks, arising for the first time during infusion of local anaesthetic, occurred significantly more frequently when single, end-holed catheters were used (29 (16.4%)) compared with multi-orifice catheters (14 (8.4%)) (P0.05).

We report a case of lumbar extradural abscess that presented 9 days after an elective Caesarean section performed under combined spinal-extradural anaesthesia. This was successfully treated conservatively with full recovery. The clinical course included development, and then resolution, of mild paraparesis. Conservative treatment of an extradural abscess in the obstetric population has not been described previously.

To clarify the effects of the pregnant uterus on the extradural venous plexus in the supine and lateral positions, we studied magnetic resonance (MR) images of the lumbar spine in three parturients. T2-weighted axial MR images were obtained with the parturient in the supine and lateral positions. On each slice level in the same subject, the MR images were compared with the control MR images obtained before pregnancy. When the parturient lay supine, the pregnant uterus compressed the inferior vena cava and almost totally obstructed it; the extradural venous plexus was engorged. On turning the parturient into the lateral position, the inferior vena cava was free from compression, and the engorged extradural venous plexus was found to shrink to the level of the non-pregnant state.

We have examined the extradural space using a flexible extraduroscope in 74 patients undergoing extradural anaesthesia at the L2-3 interspace. Extraduroscopy showed that the extradural space becomes widely patent and the fatty tissue in the extradural space diminishes with increasing age. We postulate that these age-related structural changes may affect the spread of local anaesthetic in the extradural space.

Because of the potential seriousness of unrecognized dural puncture during the performance of extradural analgesia and the widespread use of normal saline for the "loss of resistance" technique, it is important to differentiate between cerebrospinal fluid (CSF) and saline dripping from the extradural needle. During insertion of lumbar drains in 10 neurosurgical patients, we first identified the extradural space using saline for loss of resistance. Temperature (using the back of the gloved hand), pH, glucose and protein (using urine testing sticks) were tested by a blinded observer for ability to distinguish saline aspirated from the extradural space from CSF aspirated on establishing the dural puncture. Temperature, glucose and protein were independently 100% accurate in distinguishing saline from CSF. One saline sample had a pH value greater than 7 compared with nine CSF samples. We conclude that simple bedside testing for temperature, glucose, protein and pH accurately distinguished between CSF and saline used to identify the extradural space.