Clinical results with the acoustic puncture assist device,a new acoustic device to identify the epidural space

Sixty patients scheduled for lumbar epidural anesthesia were included in a study in which we evaluated the efficacy of localizing the epidural space by means of an acoustic signal. A prototype of an acoustic puncture assist device, connected to the epidural needle by an extension tube, generated the pressure needed to perform the epidural puncture and translated this pressure into corresponding acoustic and visible signals. The device frees the anesthesiologist to handle the epidural needle with both hands and to detect the epidural space by means of these signals. In all 60 patients (100%), the epidural space was successfully located by using the acoustic signal. In all cases, this was confirmed by the pressure measurement, which proved to be a reliable indicator for correct identification of the epidural space. We conclude that it is possible to locate the epidural space by means of the acoustic puncture assist device. The method proved to be reliable, safe, and simple in this study. The benefits of this new epidural puncture technique include better needle control, teaching, control of correct catheter placement, and documentation. The last can be an important adjunct to anesthesia practice. IMPLICATIONS: The authors demonstrate that it is possible to identify the epidural space by an acoustic and visible signal. An experimental setup constructed for this purpose makes the epidural puncture procedure audible and visible.     

Does epidural injection of physiological saline facilitate the advancement of catheters?

Seventy patients (ASA I, ASA II), scheduled for a surgical intervention under epidural or combined spinal-epidural anaesthesia, were randomly allocated to one of two groups. The epidural space was identified by loss of resistance using air, followed by injection in Group A (35 patients) of 10 ml of physiological saline directed cephallad and in Group B (35 patients) by no injection. Thereafter an anaesthetist, different to the one who placed the Tuohy in the epidural space, advanced a catheter up to 10 cm into the epidural space. At each cm of advance the resistance was judged. No significant difference in resistance was found between the groups. The authors conclude that the injection of 10 ml of physiological saline into the epidural space does not facilitate the advancement of an epidural catheter.     

Thoracic epidural puncture guided by an acoustic signal: clinical results

BACKGROUND AND OBJECTIVE: In previous studies we have demonstrated that it is possible and safe to identify the lumbar epidural space by an acoustic and visible signal. The use of an experimental set-up constructed for this purpose, the acoustic puncture assist device, the lumbar epidural puncture procedure became both audible and visible. In the present study we have extended the use of the device to localize the thoracic epidural space. We have also evaluated whether the device can be used as a practical tool to confirm correct catheter placement. METHODS: In 100 consecutive patients a prototype of the acoustic puncture assist device was connected to the epidural needle in order to localize the epidural space. The device translates the pressure encountered by the needle tip into a corresponding acoustic and visible signal and enables the anaesthesiologist to detect the epidural space by means of the acoustic signal. After catheter insertion, local anaesthetic was administered. Subsequently the epidural block was tested. In 10 patients the device was also connected to the epidural catheter after its insertion into the epidural space. RESULTS: In all 100 patients included in the study the epidural space was successfully located by means of the acoustic signal. The only recorded complication was intravascular catheter placement in two patients. CONCLUSIONS: It is possible to localize the thoracic epidural space guided by an acoustic signal. The method was shown to be safe, reliable and simple. Potential implications of this technique include better needle control, improved monitoring for training purposes and for clinical documentation of the thoracic epidural puncture as well as identifying correct catheter placement.     

Reliability of pressure waveform analysis to determine correct epidural needle placement in labouring women

Pressure waveform analysis provides a reliable confirmatory adjunct to the loss‐of‐resistance technique to identify the epidural space during thoracic epidural anaesthesia, but its role remains controversial in lumbar epidural analgesia during labour. We performed an observational study in 100 labouring women of the sensitivity and specificity of waveform analysis to determine the correct location of the epidural needle. After obtaining loss‐of‐resistance, the anaesthetist injected 5 ml saline through the epidural needle (accounting for the volume already used in the loss‐of‐resistance). Sterile extension tubing, connected to a pressure transducer, was attached to the needle. An investigator determined the presence or absence of a pulsatile waveform, synchronised with the heart rate, on a monitor screen that was not in the view of the anaesthetist or the parturient. A bolus of 4 ml lidocaine 2% with adrenaline 5 μg.ml^?1 was administered, and the epidural block was assessed after 15 min. Three women displayed no sensory block at 15 min. The results showed: epidural block present, epidural waveform present 93; epidural block absent, epidural waveform absent 2; epidural block present, epidural waveform absent 4; epidural block absent, epidural waveform present 1. Compared with the use of a local anaesthetic bolus to ascertain the epidural space, the sensitivity, specificity, positive and negative predictive values of waveform analysis were 95.9%, 66.7%, 98.9% and 33.3%, respectively. Epidural waveform analysis provides a simple adjunct to loss‐of‐resistance for confirming needle placement during performance of obstetric epidurals, however, further studies are required before its routine implementation in clinical practice.     

The use of a sound-enabled device to measure pressure during insertion of an epidural catheter in women in labour

The insertion of an epidural catheter for labour analgesia may be challenging. This observational study compared pressures during insertion of an epidural catheter in pregnant (n = 35) and non-pregnant (n = 10) women, using an acoustic device for locating the epidural space that also records and stores pressure data during the procedure. In both groups, we compared the maximum pressure just before loss of resistance, the pressure in the epidural space and the pressure in the inserted epidural catheter. Maximum pressure just before loss of resistance in the pregnant women was significantly lower compared with the non-pregnant women. Pressures in the epidural space and with the disposable tubing connected to the inserted epidural catheter were greater in pregnant women than in non-pregnant women. The results support the hypothesis that physiological changes in the third trimester of pregnancy are the reason why epidural catheters are more difficult to insert in women in labour.     

Testing whether the epidural works: too time consuming?

Background: When using epidural anaesthesia (EDA) for pain relief after major surgery, a failure rate of 10% is common. A crucial step in improving the care of patients with EDA is to define the position of the epidural catheter. The aim of this study was to investigate how much time it takes to determine whether the block is sufficient by assessing the extent of loss of cold sensation before induction of anaesthesia. Methods: One hundred patients listed for abdominal surgery were included in the study. After an epidural catheter had been inserted and an intrathecal or an intravenous position had been made unlikely by the use of a test dose, the patient was given a bolus dose of local anaesthetic plus an opioid in the epidural catheter. The epidural block was tested every 2 min, starting at 5 min and ending at 15 min. When at least four segments were blocked bilaterally, the testing was stopped, the time was noted and the patient was anaesthetised. Results: An epidural block was demonstrated after 5–6 min in 37 patients, after 7–8 min in 43 additional patients and after 9–10 min in 15 patients. In one patient, it took 12 min and in three patients, it took 15 min. In two patients, no epidural block could be demonstrated. Conclusion: Testing an epidural anaesthetic before the induction of anaesthesia takes only 5–10 extra minutes. Knowing whether the catheter is correctly placed means better quality of care, giving the anaesthetist better prerequisites for taking care of the patient post‐operatively.     

Patients' assessment of sensory levels during epidural analgesia in labour

Thirty women in established labour and with epidurals in situ were asked to assess the sensory level of the epidural using loss of light touch sensation with their own finger. This dermatomal level was then compared to the sensory level assessed by an anaesthetist using loss of cold sensation with ethyl chloride spray. A total of 88 assessments were made. The mean dermatomal difference was 0.20 and 95% of the differences lay between 3.5 and -3.1 dermatomes. This large variation in dermatomal differences between the two methods of sensory assessment means that patient light touch is not an acceptable method of assessing epidural sensory level when compared to ethyl chloride.     

Direct observation of the epidural space by the superfine fiberscope]

The anatomy of the epidural space was examined in 82 patients 3 to 90 years old who had indications of epidural anesthesia. The superfine fiberscope with an outer diameter of 0.8 mm was utilized for this study. It was advanced through 18 gauge Tuohy needle inserted into the epidural space. All findings were documented by videography. The epidural space was located at the thoracic intervertebral space (52 patients), at the lumbar interspace (27 patients) and at the caudal space (3 patients), using an 18-gauge Tuohy needle with either median or paramedian approach. The epidural space was identified by either hanging drop or loss of resistance method. 65 of 82 cases gave a clear view of epidural space. The epidural space presented as either a space that opened widely or a space that was occupied with large masses of fat. Vessels were encountered on the dura and the flaval ligaments, as well as in the connective tissue. Large amounts of connective tissue were present in all cases. No complications, such as accidental dural puncture, epidural hematoma, infection, nerve injury attributed to this technique were observed.     

Epidural insertion: how far should the epidural needle be inserted before testing for loss of resistance?

The aim of this study was to determine the depth to which an epidural needle can safely be inserted before testing for loss of resistance. This ensures that the epidural needle is advanced far enough to encounter ligament thus avoiding the confusion that can occur when testing for loss of resistance whilst still in subcutaneous tissues. A survey of the distance between the skin and the epidural space in 400 obstetric patients was performed. Three hundred and ten midline epidurals showed a highly significant correlation (P<0.001) between the patient's pregnant weight and the distance to the epidural space. Using these data confidence limits were calculated in order to quantify the distance that the epidural needle could safely be inserted before testing for loss of resistance. Dividing the patient's pregnant weight by 25 will give this distance in centimetres. Seventy six paramedian approaches were performed and a less good correlation was found between the depth of the space and the woman's weight. There was no correlation with height or foot size.     

空气与液体阻力消失法定位硬膜外间隙效果的比较:Meta分析

目的 采用Meta分析法比较气体或液体阻力消失法定位硬膜外间隙的效果.方法 检索Cochrane图书馆、PubMed、EMBASE、中国生物医学文献数据库、中国期刊全文数据库、维普中文科技期刊、万方数字化期刊群等数据库,分别收集空气或液体阻力消失法定位硬膜外间隙的前瞻性临床随机对照研究.采用Cochrane系统评价法评价纳入文献的质量.收集两组患者资料采用RevMan 5.0.1软件进行Meta分析.结果 共纳入7项研究,包括5183例患者.分为空气阻力消失法组(A组)和液体阻力消失法组(L组).与A组比较,L组困难置管发生率、置管误入血管发生率、阻滞不全发生率和术后头痛发生率降低(P＜0.05),一过性异感发生率和穿破硬膜发生率差异无统计学意义(P＞0.05).结论 与空气阻力消失法比较,液体阻力消失法可更准确地定位硬膜外间隙,阻滞效果更好,且并发症较少.     

Epidural infusion pressure in degenerative spinal disease before and after epidural steroid therapy.

The analgesic mechanism of epidural steroids in reducing pain associated with degenerative spinal disease (DSD) is poorly understood. We report increased inline epidural infusion pressure in patients with DSD and assess whether this phenomenon is affected by administration of an epidural steroid injection. We collected data during epidural placement for routine surgery or epidural steroid therapy. Using a 17-gauge Tuohy needle, with patients in the right lateral decubitus position, loss of resistance to 2 mL of saline identified the epidural space. Two minutes later the needle was attached to saline-filled tubing connected to a pressure transducer (Baxter PX 260 pressure monitoring kit with Truwave TM disposable pressure transducer). In the first part of the study, 4 successive boluses of 3 mL of local anesthetic were administered at a rate of 6 mL/min to 15 patients (age 47 +/- 6 yrs) with radicular back pain and magnetic resonance imaging (MRI) or computed tomography (CT) evidence of DSD, and to 8 control patients with no history of back pain (age 44 +/- 5 yr) while inline epidural infusion pressure was measured. In the second part of the study 44 patients with low back pain and MRI or CT evidence of DSD presenting to the pain clinic were infused with 8 mL of 0.125% bupivacaine and 40 mg of methylprednisolone (20 mg/mL) at a rate of 6 mL/min while inline epidural infusion pressure was measure and recorded. This was repeated 3 wk later. Initially, DSD patients had significantly increased infusion pressures over normals, which most likely reflects outflow resistance or obstruction. A significant decrease in inline epidural infusion pressure was observed after epidural steroid treatment. This change in pressure may indicate efficacy from epidural steroid injection. IMPLICATIONS: During injection into the epidural space we observed increased resistance in patients with degenerative spinal disease. This resistance was significantly less when measured 3 wk after an epidural steroid injection. This change in pressure may indicate efficacy from epidural steroid injection.     

Epidural injection of lidocaine reduces the response to dural puncture accompanying spinal needle insertion when performing combined spinal-epidural anesthesia

During placement of needles for combined spinal-epidural anesthesia (CSEA), patients may experience pain, pressure, paresthesia, or discomfort during skin and deeper injection of local anesthetic, needle impingement on periosteum, dural puncture by the spinal needle, and insertion of the epidural catheter. We investigated the incidence of perception of and spontaneous verbal and motor responses to insertion of a spinal needle through the dura mater and pia mater and the effect of injecting lidocaine into the epidural space through the epidural needle before inserting the spinal needle through the meninges. Forty-three patients presenting for elective cesarean delivery under CSEA were studied. After localization of the epidural space using loss of resistance to air using a 17-gauge Tuohy needle, either 3 mL preservative free normal saline or 3 mL lidocaine 2% plus epinephrine 1:200,000 was injected through the Tuohy needle. "Needle through needle" dural puncture was performed 1 min later using a 27-gauge Whitacre pencil-point needle. At the moment of dural puncture, 2 (9%) parturients given lidocaine and 17 (81%) parturients given saline (P < 0.005) responded to dural puncture by spontaneously moving (33%), spontaneously vocalizing (62%), or, in response to direct questioning, by acknowledging (76%) having perceived sensation during thecal penetration. This study reveals that dural puncture by a Whitacre 27-gauge pencil-point needle inserted through a Tuohy epidural needle sited using loss of resistance to air causes involuntary movement, spontaneous vocalization, or is perceived by the majority of patients presenting for cesarean delivery under CSEA and that lidocaine injected into the epidural space before dural puncture largely eliminates these responses and sensations.     

The combined plunger pressure-manometer method. A technique for identifying the peridural space]

The modified combined plunger pressure and manometer method (KSMM = Kombinierte Stempeldruck-Manometer-Methode) has proved to be a satisfactory alternative to the loss of resistance technique of Dogliotti. The method was tested for practicability and successful identification of the epidural space in 200 patients (80 of them pregnant) by physicians at different stages of their training. It makes it easy for young anaesthetists who are still in training and have not had much experience to learn to identify the epidural space. With this method the experienced operator can make an important contribution to the training of young doctors in epidural anaesthesia without fear of risks and failures.     

钢丝加强聚脲胺酯硬膜外导管减少硬膜外出血发生率

目的 比较钢丝加强聚脲胺酯与聚氯乙烯硬膜外导管对硬膜外腔出血发生率的影响. 方法 150例拟行连续硬膜外或蛛网膜下腔-硬膜外联合阻滞患者,按随机数字表法分为聚氯乙烯硬膜外导管组(A组,n=75)和钢丝加强聚脲胺酯硬膜外导管组(B组,n=75),以阻力消失作为判断硬膜外针到达硬膜外腔的标志,记录放置硬膜外导管遇到阻力和同抽出血情况.追踪术后1周有无硬膜外血肿发生. 结果两组间性别、年龄、体重等差异无统计学意义(P>0.05). A组和B组未遇到明显阻力分别为42.7%和78.6%,遇到轻微阻力分别为48.0%和16.0%;遇到阻力较大,放入导管困难分别为9.3%和5.4%,组间比较差异有统计学意义(P<0.01).A组无回血为82.6%,有不连续回血率为10.7%,有连续回血率为6.7%;B组无回血率为100%,组间比较差异有统计学意义(P<0.01).两组术后均无硬膜外血肿压迫症状的并发症.结论 聚氯乙烯硬膜外导管损伤硬膜外血管引起出血为常见并发症,采用钢丝加强聚脲胺酯硬膜外导管可显著减少硬膜外出血发生率.     

The visualisation of dura perforation and blood patches with ultrasound

The postdural puncture headache (PDPH) is a possible complication after spinal or epidural puncture. The therapeutic concept is usually organised step by step, but the epidural blood patch is the most reliable and effective therapy. In earlier studies myelographie, epidurographie and MRT were used, to visualise the localisation of the dural defect and to describe the effects of patching the epidural space. Our working group focused on the utilisation of ultrasound and we decided to use this technique for the visualisation of bloodpatches. With agreement of the local ethics committee we monitored the performance of 4 epidural bloodpatches in pregnant women, who suffered from PDPH. We used a General Electric LQ 400 ultrasonograph with a 7-MHz-probe. To ensure sterile conditions we used sterile ultrasound sleeves and sterile ultrasound gel. In 3 of 4 cases a continuity loss could be represented in the doppel layer signal of the dura. It had the size of the diameter of a Tuohy needle. In one case the defect of the dura was larger than in the preliminary investigations (2,5 - 3 mm). The ultrasonography of the epidural space was performed in the paramedian scan. All patches were placed by using the conventional loss of resistance technique with using online ultrasound support. The epidural puncture and the application of the blood patches were visualised simultaneously in all cases. With the injection of blood a brief expansion of the epidural space was seen. The patients recieved a mean injection volume of 17 ml sterile blood. 10 to 40 seconds after the injection of blood the disconituity of the dura doppel layer signal was no longer provable. Within a short time we could detect the increase of cerebrospinal fluid and the patients headache was treated sucessfully. The clinical use of this diagnostic technique can be found in the simultaneous presentation of the dura leakage and the intervention while performing an epidural bloodpatch. Since these informations are relevant for further clinical practice further investigations are warranted.     

Epidrum<Superscript>®</Superscript>: a new device to identify the epidural space with an epidural Tuohy needle

Epidrum^® is an optimal pressure, loss of resistance device for identifying the epidural space. We investigated the usefulness of Epidrum versus the loss of resistance or hanging drop techniques while performing epidural anesthesia. Eighty adult patients who were scheduled for elective surgery under lumbar epidural anesthesia were randomized into two groups. The first group (Epidrum group) consisted of 40 adult patients who were scheduled for epidural anesthesia using Epidrum. The second group (control group) consisted of 40 adult patients who were scheduled for epidural anesthesia using the loss of resistance or hanging drop technique. We recorded the time required to identify the epidural space and outcomes of epidural catheterization. The attending anesthesiologists were also questioned regarding the ease of control of the Tuohy needle and of epidural space identification with each method. The time required to perform epidural anesthesia was significantly shorter in the Epidrum group than in the control group [28 s (10–76) vs. 90 s (34–185); median (interquartile range)] (p < 0.05). Tuohy needle control was significantly easier in the Epidrum group than in the control group (p < 0.05). Epidrum is useful for performing epidural anesthesia quickly while obtaining good Tuohy needle control.     

Threshold current for an insulated epidural needle in pediatric patients

We designed this study to determine the threshold current for nerve stimulation of an insulated needle in the epidural space. The intended dermatome was identified using the bony landmarks of the spine. An 18-gauge insulated Tuohy needle was inserted perpendicularly to the skin and advanced until "loss of resistance" was felt. A nerve stimulator was then connected to the insulated needle. Twenty patients were studied using an insulated Tuohy needle and one patient was studied using a noninsulated Tuohy needle. Muscle twitch was elicited with a current of 11.1 +/- 3.1 mA (mean +/- sd) in all patients in which an insulated needle was used. Muscle twitches were within 2 myotomes of the intended level (based on bony landmarks). Muscle twitch was not elicited with a noninsulated needle. After catheter threading, positive stimulation tests were elicited via epidural catheters in all patients (4.9 +/- 2.3 mA). Postoperative radiograph confirmed all catheter placements within 2 myotomes of the muscle twitches. Electrical stimulation may be a useful adjuvant tool to loss of resistance for confirming proper thoracic epidural needle placement. The threshold current criteria for an insulated needle (6-17 mA) would be higher than the original Tsui test criteria described for an epidural catheter (1-10 mA) in the epidural space.     

Ultrasound-guided epidural catheter insertion in children

Epidural catheters (EC) are often used in pediatric patients for intraoperative and postoperative pain relief. The small anatomical structures and catheter insertion under general anesthesia make it more difficult to perform EC and to prevent damage. In this study we investigated the use of ultrasound (US) in detecting neuraxial structures during insertion and placement of EC in children. ASA I-II children scheduled for elective surgery under combined general and epidural anesthesia were studied. Patients received balanced anesthesia using sevoflurane, opioids and rocuronium. Before EC insertion US examination in a lateral position was done to visualize and identify neuraxial structures. Quality of visualization and site and depth of structures were recorded. Using a sterile kit to hold the US probe in position and enable the visualization of the neuraxial structures, an epidural cannula was inserted, using the loss of resistance technique, as the EC passed under US control to the desired level. Of 25 children, 23 were evaluated. Epidural space, ligamentum flavum, and dural structures were clearly identified and the depth to skin level estimated in all patients. Loss of resistance was visualized in all patients with a lumbar epidural approach. Correlation of US measured depth and depth of loss of resistance was 0.88. In eight of 23 patients EC could be visualized during insertion and in 11 others it could be visualized with additional US planes. US is an excellent tool to identify neuraxial structures in both infants and children. The size and the incomplete ossification of the vertebra allow exact visualization and localization of the depth of the epidural space, the loss of resistance, and all relevant neuraxial structures. IMPLICATIONS: Epidural catheters in children are mostly inserted under sedation or general anesthesia. This study showed that the use of ultrasound could help visualize all relevant neuraxial structures and their site and depth from the skin.     

A prospective comparative study of two indirect methods for confirming the localization of an epidural catheter for postoperative analgesia

We prospectively evaluated, in randomized order, 2 indirect methods of confirming the localization of an epidural catheter for postoperative analgesia in 218 surgical patients: epidural stimulation test (EST) and epidural pressure waveform analysis (EPWA). The epidural space was localized by using a loss of resistance technique. All catheters were inserted 5 cm into the epidural space and primed with 5 mL of 0.9% normal saline. There were no differences between the methods: the positive predictive value and specificity were high (100% in both groups), but the sensitivity was moderate (80% for EST and 81% for EPWA) and the negative predictive value was low (16% for EST and 17% for EPWA). Combining both methods yielded better sensitivity (97%) and negative predictive value (57%) (P < 0.001). The sensitivity of EST was increased to 87% (P < 0.05) if sensory response was included as well as motor response for stimulation less than 10 mA. We suggest the inclusion of sensory response in the appropriate dermatome at a current <10 mA as a criterion for adequate epidural catheter localization for EST testing. EPWA sensitivity was significantly better with older patients: 94% for patients older than 80 yr compared with 63% for patients younger than 40, 73% for patients 40 to 60, and 85% for patients aged 60 to 80 yr (P = 0.03). We conclude that the two tests are comparable for confirming catheter placement.     

Comparative study of detection methods in epidural anesthesia: Episensor and loss of resistance

The aim of the present study is to evaluate an electronic detector of negative pressure (Episensor, Palex, Spain) designed for the identification of epidural space. Ninety patients were randomly assigned to two groups: group 1 (n = 47) received epidural anesthesia as perioperative analgesic technique with Episensor method and group 2 (n = 43) received epidural anesthesia with the classic method of loss of resistance with gas mandrin. The following parameters were studied: a) demographic features, b) characteristics of epidural anesthesia, and c) complications occurring during space detection. There were no statistical differences in the analysis of demographic variables neither in the quality of the epidural anesthesia achieved in both groups. With respect to complications, group I presented the highest number of complications although only the lack of detection of epidural space achieved statistical significance (8.5%, p less than 0.05); the incidence was lower than that reported in the literature as physiologically possible in the lumbar epidural segment. We conclude that progressive knowledge of Episensor may decrease the initial incidence of complications with a success rate similar to that of classic techniques of identification of epidural space.