Lumbar epidural catheter insertion: the midline vs. the paramedian approach

BACKGROUND AND OBJECTIVE: The purpose of this study was to compare the characteristics of epidural catheter insertion via the midline or the paramedian approach with regard to ease of catheter insertion, incidence of paraesthesias and efficacy of epidural block. In addition to the type of approach, the prognostic value of Patients characteristics variables with regard to the incidence of paraesthesias was assessed. METHODS: Thirty patients scheduled for surgery under epidural anaesthesia were randomly assigned to one of two groups of 15 patients each. Epidural anaesthesia was performed via a midline or paramedian approach using loss of resistance to saline. Variables measured were: time needed to identify the epidural space, time needed for and ease of epidural catheter insertion and the incidence of paraesthesias. After completion of these observations, epidural anaesthesia was established with 150 mg ropivacaine 1%. Efficacy of the epidural block was assessed by the need for intraoperative analgesics and by the patient on a three-point scale (good/fair/poor). RESULTS: Quality of sensory blockade was adequate in both groups. Catheter insertion was significantly faster using the paramedian approach. The difference between the two approaches with regard to the incidence of paraesthesias was not significant, however, there was a trend towards more paraesthesias in the midline group. In the multivariate analysis, type of approach was an independent significant predictor of paraesthesias and we found a trend towards a higher incidence of paraesthesias in female patients. CONCLUSIONS: Catheter insertion was faster in the paramedian group and we found a trend towards a higher incidence of paraesthesias with the midline approach.     

Paramedian lumbar epidural catheter insertion with patients in the sitting position is equally successful in the flexed and unflexed spine

Positioning for placement of an epidural catheter can be quite painful for patients with lower limb injuries. We randomly allocated 50 patients scheduled for surgery after lower limb injuries for placement of a lumbar epidural catheter in the sitting position with the back in the neutral unflexed position by either the midline or paramedian approach. If the approach failed after two attempts, patients were placed in a flexed-spine position, and the procedure was attempted again. Technical difficulties and complications were recorded. In 17 patients in the midline group, and 1 patient in the paramedian group, it was not possible to insert the needle initially, and a flexed-spine position was required (P < 0.05). The incidences of resistance to catheter insertion (eight versus one), paresthesia (seven versus zero), and appearance of blood in the catheter (six versus zero) were significantly more frequent in the midline compared with the paramedian approach. The midline group also experienced more discomfort than the paramedian group. We conclude that, with the patient sitting with an unflexed spine, it is usually possible to insert an epidural catheter with the paramedian approach.     

Technical advantages of the paramedian approach for lumbar epidural puncture and catheter introduction

The lumbar epidural space of 14 autopsy subjects was examined by epiduroscopy. The aim was to compare the midline and paramedian approaches of locating the space, the estimated risk of accidental dural puncture, the course taken by the epidural catheter after introduction and with special attention to the influence of the dorsomedian connective tissue band. The paramedian needle passed a greater distance within the epidural space before contact with the dura mater and demonstrated a low risk of accidental dural puncture. The catheter passed by the paramedian approach did not cause any tenting of the dura and took a straight cephalad direction in all 14 cases. The midline catheter caused tenting of the dura in all 14 cases and the direction of travel was variable. Differences were statistically significant. Influence of the dorsomedian connective tissue band was greatest on the behaviour of the midline needle and catheter.     

Cervical epidural analgesia via a thoracic approach using nerve-stimulation guidance in adult patients undergoing total shoulder replacement surgery

BACKGROUND: Continuous cervical epidural anesthesia can provide excellent peri- and post-operative analgesia, although several factors prevent its widespread use. Advancing catheters from thoracic levels to the cervical region may circumvent these barriers, provided they are accurately positioned. We hypothesize that guiding catheters from thoracic to cervical regions using low-current epidural stimulation will have a high success rate and enable excellent analgesia in adults undergoing total shoulder arthroplasty. METHODS: After Institutional Review Board approval, adult patients were studied consecutively. A 17-G Tuohy needle was inserted into the thoracic epidural space using a right paramedian approach with loss of resistance. A 20-G styletted epidural catheter, with an attached nerve stimulator, was primed with saline and a 1-10 mA current was applied as it advanced in a cephalad direction towards the cervical spine. Muscle twitch responses were observed and post-operative X-ray confirmed final placement. After a test dose, an infusion (2-8 ml/h) of ropivacaine 2 mg/ml and morphine 0.05 mg/ml (or equivalent) was initiated. Verbal analog pain scale scores were collected over 72 h. RESULTS: Cervical epidural anesthesia was performed on 10 patients. Average current required to elicit a motor response was 4.8 +/- 2.0mA. Post-operative X-ray of catheter positions confirmed all catheter tips reached the desired region (C4-7). The technical success rate for catheter placement was 100% and excellent pain control was achieved. Catheters were positioned two to the left, four to the right and four to the midline. CONCLUSION: This epidural technique provided highly effective post-operative analgesia in a patient group that traditionally experiences severe post-operative pain and can benefit from early mobilization.     

Combined spinal-epidural techniques

The combined spinal-epidural technique has been used increasingly over the last decade. Combined spinal-epidural may achieve rapid onset, profound regional blockade with the facility to modify or prolong the block. A variety of techniques and devices have been proposed. The technique cannot be considered simply as an isolated spinal block followed by an isolated epidural block as combining the techniques may alter each block. This review concentrates on technical and procedural aspects of combined spinal-epidural. Needle-through-needle, separate-needle and combined-needle techniques are described and modifications discussed. Failure rates and causes are reviewed. The problems of performing a spinal block before epidural blockade (potential for unrecognised placement of an epidural catheter, inability to detect paraesthesia during epidural placement, difficulty in testing the epidural, delay in positioning the patient) are described and evaluated. Problems of performing spinal block after epidural blockade (risk of catheter or spinal needle damage) are considered. Mechanisms of modification of spinal blockade by subsequent epidural drug administration are discussed. The review considers choice of technique, needle type, patient positioning and paramedian vs. midline approach. Finally, complications associated with combined spinal-epidural are reviewed.     

Accidental pleural puncture by a thoracic epidural catheter

We report the occurrence of an accidental pleural puncture by an epidural catheter that happened during the attempted induction of thoracic epidural anaesthesia using a paramedian approach in an awake patient. The incorrect placement of the catheter was recognised while the patient was undergoing thoracoscopic surgery. The possibility of accidental pleural puncture during attempted thoracic epidural catheter placement by either the paramedian or the midline approach should be borne in mind. A misplaced catheter may injure lung tissue and result in a potentially dangerous intra-operative tension pneumothorax.     

Epidural washout with high volumes of saline to accelerate recovery from epidural anaesthesia

BACKGROUND: Prolonged postoperative blockade can follow neuraxial blocks for short surgical procedures. We investigated whether washout with a high volume of saline through an epidural catheter could provide a faster recovery after epidural anaesthesia. METHODS: Thirty patients were randomly assigned to a control group (no washout), to group 2x (epidural washout with twice the volume of 2% mepivacaine) and group 4x (epidural washout with four times that volume). RESULTS: Recovery times from sensory blockade at L2 were 151+/-24, 122+/-29 and 116+/-24 min for control, 2x and 4x groups respectively. Significant differences were found in both saline groups when compared with control group, but not between group 2x and group 4x. No differences were found concerning motor blockade. One patient in group 4x demonstrated signs of intracranial hypertension. Mepivacaine plasma concentrations were increased by saline washout in group 4x. CONCLUSIONS: Epidural washout with a high volume of saline can not be recommended since no clinically significant reduction in the recovery time can be achieved without risk.     

A comparison between midline and paramedian approaches for combined spinal-epidural anesthesia]

We compared midline approach with paramedian approach for combined spinal-epidural anesthesia (CSEA) by needle through needle technique. Seventy patients undergoing elective gynecological surgery received CSEA with a 27 G Whitacre spinal needle, which protrudes 12 mm beyond the tip of the Tuohy needle. The successful subarachnoid puncture with first attempt was noted in 33 patients (94%) of midline group (M group), in 31 patients (89%) of paramedian group (P group). At the subarachnoid puncture, skin to epidural space distance (43.2 mm vs 53.4 mm) and protrusion length of spinal needle (5.5 mm vs 8 mm) were significantly longer in the P group than in the M group. Abdominal radiography revealed the flexion of epidural catheter in 19 patients (54%) of M group and in 2 patients (6%) of P group. The choice of midline or paramedian approach for CSEA did not affect the success rate of the subarachnoid puncture, but paramedian approach required longer protrusion length of the spinal needle than midline approach. To raise the success rate of subarachnoid puncture by paramedian approach, a long protruded spinal needle is recommended.     

Acute tissue damage following epidural cannulation: a comparison between the midline and paramedian approach in obstetric patients

Forty obstetric patients were randomly allocated to receive either a midline or paramedian approach to the epidural space using loss of resistance to air. Tissue trauma was assessed by blinded observers, clinically by the presence of pain and radiologically using magnetic resonance imaging (MRI). Technical difficulties with imaging reduced those who were scanned to 10 in the paramedian group and 8 in the midline group. Lateralizing signs of tissue oedema were not related to the method of epidural cannulation. There was no significant difference in localized back pain between the two groups, and this was not related to MRI findings. Pain did not persist for more than 4 days.     

低容量罗哌卡因硬膜外麻醉用于椎间盘镜髓核摘除术

目的比较低容量不同浓度的罗哌卡因在腰段硬膜外麻醉行椎间盘镜手术时的临床效果. 方法 150例临床拟行椎间盘镜髓核摘除术病人,随机分为0.8%罗哌卡因(n=50),0.6%(n=61),0.4%(n=39)3组.硬脊膜外穿刺置管后,给2%利多卡因5ml试验量,有麻醉平面后,每组分别一次性注入不同浓度罗哌卡因5ml.以Bromage分级法判断运动神经阻滞分级,比较起效、恢复时间和分离麻醉情况. 结果神经阻滞起效时间感觉神经小于运动神经,而其维持时间大于运动神经.Ⅱ组对感觉、运动神经阻滞分离明显,与Ⅰ、Ⅲ组比较P＜0.01. 结论 0.6%的低容量罗派卡因用于椎间盘镜手术时,对感觉、运动神经阻滞分离效果满意,麻醉的起效时间随药物浓度递增而加快.     

Rapid injection of epidural mepivacaine speeds the onset of nerve blockade

PURPOSE: When used intraoperatively, mepivacaine can produce a satisfactory sensory block. However, insufficient information is available concerning the factors that affect the speed of nerve blockade with epidural analgesia. The optimal rate of injection of mepivacaine has not been determined. We examined whether the speed of epidural infusion of mepivacaine affects the speed of nerve blockade. METHODS: Forty patients, physical status ASA I-II, scheduled for gynecological abdominal surgery, were enrolled in this double blind randomized trial. A catheter was inserted 4 cm in the epidural space in the midline at L1-L2. Three minutes after a test dose of 2 mL plain 1% mepivacaine over four seconds, 8 mL were injected epidurally at a rate of 1 mL.sec(-1) (fast group) or 0.05 mL.sec(-1) (slow group). Sensory and motor blockade, blood pressure, and heart rate were assessed at five, ten, and 15 min after the epidural injection. RESULTS: There was a significant difference in the spread of sensory blockade at five minutes after the epidural injection between the two groups, but not at ten and 15 min. Blood pressure decreased at five and ten minutes, recovered at 15 min in the fast group, and remained stable in the slow group. CONCLUSION: Rapid injection of mepivacaine in the epidural space produced a more rapid onset of epidural block than slow injection, but there was no difference in the final extent of the block.     

Survey of paediatric epidural practice in the UK

Introduction In infants and young children epidural catheterisation is technically more difficult than in older children and adults ( 1 ). Various solutions have been offered to make this difficult task easier 2 - 4 ). One of the suggested remedies is using the paramedian approach to the epidural space ( 5 , 6 ). The paramedian approach not only makes the procedure technically less difficult, but because of the angle of needle entry, the chance of dural puncture is low ( 7 , 8 ). The aims of this questionnaire were to investigate whether paediatric anaesthetists experienced any catheter related difficulties with epidural anaesthesia, what manoeuvres were used to overcome these difficulties and if a paramedian approach was used to place paediatric epidurals. Methods A postal questionnaire was sent to members of the Association of Paediatric Anaesthetists resident in the UK. There were five questions asked with an option of 2–4 replies. The questions pertained to frequency of use of epidural catheters in infants and young children, preferred approach, difficulties encountered, methods to overcome problems and use of paramedian approach. Results 203 questionnaires were sent between November 2000 and December 2000 and 145 replies were received making an overall response rate of 71.45%. From our survey we note that 66 out of 145(45.5%) paediatric anaesthetists regularly use epidural catheters in infants and children less than 15 kg, while 42(28.9%) are occasional users and 9(6.2%) use them infrequently. Thirty out of 145(20.66%) never use this technique in this age group at all. Therefore 115 respondents use the technique. As regards the preferred approach; 107 out of 115(77%) paediatric anaesthetists use the midline approach while only 5 members(4.34%) prefer the paramedian approach and a small percentage(2.6%) use other approaches i.e. caudal catheters. Some members (8/145) in the survey suggested that the reason for infrequent use of the paramedian approach was lack of training. 49/115(42.6%) paediatric anaesthetists occasionally encountered problems with catheter insertion and 69/115(60%) rarely had any problems. Therefore it was felt that, since there were no problems with the midline approach, a change was not warranted. In case of a problem with epidurals only 8 members(6.95%) would consider using the paramedian approach. Nearly 50% (57/115) of epidural users felt that they did not know/could not comment on the paramedian approach, as they never used the technique. Suggested methods to overcome problems with threading the catheter include: using 18 g Tuohy needle with 21 g catheter rather than 23 g catheters; inserting the needle in midline in a slightly cephalad direction in order to ‘open the angle’ for subsequent catheter insertion; using the blue introducer for feeding the catheter; injecting saline/local anaesthetic to ‘dilate’ the epidural space before inserting the catheter, etc. Summary In summary, this survey of epidural practices in young children shows that technical problems with epidural catheter insertion in this age group are not common. The paramedian approach to the epidural space, though theoretically sound, is not very popular with paediatric anaesthetists in the UK.     

The lumbar epidural space in patients examined with epiduroscopy

Percutaneous epiduroscopy was performed in 10 patients with the aim of comparing the lumbar epidural space of the patients with the findings made earlier in autopsy subjects. The patients were scheduled for partial laminectomy for a herniated lumbar disc. A complete examination was possible in eight subjects. The extent of view was very limited. The epidural space opened up only temporarily as air was injected. The dura mater lay very close to the dorsal aspect of the epidural space and was attached to the flaval ligaments by a dorsomedian connective tissue band. The band was identified in all eight subjects and was found to cause a dorsal fold in the dura mater. An epidural catheter was introduced 2-5 cm into the space by midline puncture in four patients and by the paramedian approach in the other four. The catheter was visualized in two patients only when the paramedian approach was used. None of the midline catheters could be seen in the space. In 2 of the 10 subjects a moderate bleeding impaired the view and made complete examination impossible. Smaller bleeding occurred in three other subjects. The partial laminectomy performed one to two interspaces caudad to the level of endoscopy did not reveal any evidence of epidural bleeding in any subject. The postoperative course of all patients was uneventful.     

Intentional lateral epidural catheter placement for anterior cruciate ligament reconstruction

BACKGROUND: Unilateral epidural block might constitute a clinical option in lower limb orthopedic surgery. METHODS: Seventy-five patients undergoing anterior cruciate ligament reconstruction (ACLR) were randomized to either a laterally directed epidural catheter (IUEC, n = 40) or a classic midline catheter (CMEC, n = 35). Paresthesia encountered during catheter insertion was registered. The start dose of the anesthetic mixture clonidine 60 microg (0.4 ml), sufentanil 15 microg (0.3 ml) and ropivacaine 10 mg ml(-1)(10.3 ml) in 11 ml of total volume) was set at 5 ml and was increased by 2 ml if anesthesia was inadequate after assessment for sensory blockade to cold and pin-prick. Data were registered intra- and postoperatively regarding pain scores as well as motor block, hemodynamic parameters, adverse effects and need for supplemental analgesia other than a continuous postoperative epidural infusion. RESULTS: In the IUEC group 80% of patients reported a light paresthesia of the affected side during catheter insertion, whereas 71% of patients in the CMEC group reported no paresthesia at all. The amount of anesthetic used to establish surgical anesthesia was lower in the IUEC group (6.2 +/- 0.8 vs. 8 +/- 1.9 ml, P < 0.001). Motor block (Bromage score) of the unaffected side was significantly lower in the IUEC group (P < 0.001). Pain intensity scores, hemodynamic parameters, and supplemental analgesia given were similar between the two groups except for VAS scores at 12 h postoperatively, which were higher in the CMEC group (P < 0.01). Urinary retention was significantly more frequent in the CMEC group (19/35 vs. 5/40, P < 0.001). CONCLUSION: These results suggest that the IUEC technique is a feasible and efficient method for providing anesthesia and analgesia for ACLR and is associated with a lower consume of anesthetics, less motor block and a reduced incidence of urinary retention.     

Reversal of bupivacaine epidural anesthesia by intermittent epidural injections of crystalloid solutions

This study was designed to determine whether epidural motor blockade could be reversed by postoperative injections of crystalloid solutions via the epidural catheter. Twenty-seven patients (ASA physical status I, nonlaboring) had epidural anesthesia with 0.75% bupivacaine for elective cesarean delivery. Postoperatively, patients were randomized to receive three 15-mL injections (over 30 min) of crystalloid solutions (normal saline or Ringer's lactate) or no treatment (control) via the epidural catheter. Degree of motor and sensory blockade was evaluated with an investigator blinded to treatment group. Rate of resolution of sensory blockade was not different among groups. However, time for resolution of motor blockade was more than twice as long in the control group than in either treatment group (control = 178 +/- 70 min vs Ringer's lactate = 84 +/- 44 min, normal saline = 70 +/- 38 min, P = 0.001). The data suggest that unwanted motor blockade due to epidural anesthesia can be reversed by epidural injections of crystalloid solutions.     

Asymmetric onset of sympathetic blockade in epidural anaesthesia shows no relation to epidural catheter position

A radiological study was performed of the relation between onset of sympathetic blockade in lumbar epidural anaesthesia and the position of the epidural catheter. In 20 patients scheduled for extracorporeal shock wave lithotripsy (ESWL), the onset of sympathetic blockade after epidural anaesthesia (catheter insertion at the presumed level L2-L3, and injection of 20 ml prilocaine 2% with epinephrine 5 micrograms/ml) was objectively evaluated by photoplethysmography. The onset was asymmetrical in 18 patients, and symmetrical in only two. Just before the start of ESWL, the position of the epidural catheter was checked by radiography after injection of 0.5 ml iohexol 300 mg/ml (Omnipaque 300). The radiopaque contrast medium was found median (n = 2), right (n = 7) and left (n = 11) of the midline. In only 9 patients was the earliest onset of sympathetic blockade correlated with the side of the catheter position, and thus no relation between catheter position and onset of sympathetic blockade was found.     

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.     

Factors affecting the distribution of neural blockade by local anesthetics in epidural anesthesia and a comparison of lumbar versus thoracic epidural anesthesia

The spread of sensory blockade after epidural injection of a specific dose of local anesthetic (LA) differs considerably among individuals, and the factors affecting this distribution remain the subject of debate. Based on the results of recent investigations regarding the distribution of epidural neural blockade, specifically for thoracic epidural anesthesia, we noted that the total mass of LA appears to be the most important factor in determining the extent of sensory, sympathetic, and motor neural blockade, whereas the site of epidural needle/catheter placement governs the pattern of distribution of blockade relative to the injection site. Age may be positively correlated with the spread of sensory blockade, and the evidence is somewhat stronger for thoracic than for lumbar epidural anesthesia. Other patient characteristics and technical details, such as patient position, and mode and speed of injection, exert only a small effect on the distribution of sensory blockade, or their effects are equivocal. However, combinations of several patient and technical factors may aid in predicting LA dose requirements. Based on these results, we have also formulated suggested epidural insertion sites that may optimize both analgesia and sympathicolysis for various surgical indications.     

Coiling of lumbar epidural catheters

BACKGROUND: The difficulties in threading an epidural catheter to vertebral levels remote to the puncture level have been well documented. This study was undertaken to determine the length that a single orifice epidural catheter can be threaded into the lumbar space without coiling (coiling length), and whether this is affected by the direction of the epidural needle bevel. METHODS: Forty-five young male patients scheduled for surgery under epidural analgesia were enrolled. The epidural space was identified using a midline approach at the L(2-3) or L(3-4) interspace with the loss of resistance to air technique. A 19-G single-orifice epidural catheter (Flextip Plus, Arrow International, Inc, Reading, PA, USA) was inserted through a Tuohy needle oriented either cephalad (n=20) or caudad (n=25). During insertion, the path and the position of the catheter tip was determined by fluoroscopy using iohexol dye. RESULTS: The median coiling length was 2.8 cm, ranging from 1.0 to 8.0 cm. Only 13% of epidural catheters could be threaded 4 cm beyond the tip of the needle without coiling. No significant difference was found in coiling length between the cephalad group (2.9 cm) and the caudad group (2.5 cm). CONCLUSION: This study demonstrates that coiling length is independent of whether the bevel of the Tuohy needle is directed cephalad or caudad. We recommend that an optimal insertion depth of an end-hole single orifice catheter is 3 cm.     

Anesthésie péridurale pour la chirurgie de la cheville et du pied: influence de la position assise

The effects of the sitting position on the quality of both sensory and motor blockade of segments L5 and S1 and the haemodynamic consequences during epidural anaesthesia were studied on 39 patients undergoing ankle or foot surgery. After insertion of an epidural catheter with the patient in the lateral position, 19 patients were kept sitting for 15 min following the injection of the local anaesthetic and 20 remained supine for the duration of anaesthesia (control group). All patients received a dose of 20 ml of 1.73% carbonated lidocaine with epinephrine 1:200,000. The quality and time of onset of the sensory blockade for segments L1-S2 as well as its cephalad spread were comparable in both groups. Fourteen patients of the sitting group achieved motor blockade of more than three of five myotomes compared with five patients in the supine group (P less than 0.001). The maximum decrease in mean arterial pressure occurred sooner in the sitting group (14 +/- 9 min) than in the control group (21 +/- 10 min; P less than 0.01) and was more severe (-24 +/- 10% vs -16 +/- 10% respectively; P less than 0.05). Our results indicate that placing the patient in the sitting position for 15 min after inducing epidural anaesthesia does not influence caudal sensory blockade but does increase the depth of motor blockade.