|Year : 2018 | Volume
| Issue : 3 | Page : 246-251
Comparison of the ultrasonography-guided technique and conventional anatomical landmark technique for localization of epidural space during epidural block
Dinesh K Sahu, Jitendra H Ramteke, Atul Sharma, Reena Parampill, Chandrakant Patel
Department of Anaesthesiology and Pain Management, Jagjivan Ram Railway Hospital, Mumbai, Maharashtra, India
|Date of Submission||30-Dec-2017|
|Date of Acceptance||30-Dec-2017|
|Date of Web Publication||31-Aug-2018|
Jitendra H Ramteke
Department of Anaesthesiology and Pain Management, Jagjivan Ram Railway Hospital, Mumbai 400008, Maharashtra
Source of Support: None, Conflict of Interest: None
Background and aims Anatomical landmarks-based level confirmation and loss of resistance-based space confirmation is a standard method for epidural block but is a blind procedure. Recently, the use of ultrasonography (USG) guidance during central neuraxial blocks to preview the anatomy before needle puncture has started. We carried out a study to find whether USG-guided technique is superior than landmark guided for epidural space localization.
Patients and methods This randomized prospective, open-label study included 76 patients aged 40 to 65 years, American Society of Anesthesiologist physical status I–III undergoing infraumbilical surgeries, divided in two groups. In group 1, anatomical landmark-guided technique and in group 2, preprocedural USG scan was used for puncture site determination. We evaluated the time taken to insert an epidural needle; number of attempts, number of times the cortexes of bone touched by needle, ultrasound visibility score, distance between skin to ligamentum flavum, correlation between actual needle depth and ultrasound-measured depth.
Results Mean time taken for insertion of epidural needle in group 1 was 72.21±45 s and in group 2 was 54.82±40.87 s (P=0.027). Epidural space was located in the first attempt in 71.15% individuals of group 1 and 92.1% individuals of group 2. The Pearson’s correlation coefficient between the USG-measured distance between skin to ligamentum flavum and the actual depth of needle mark was significant.
Conclusion The USG-guided epidural space localization reduces time to insert epidural needle and number of attempts for localization of epidural space. There is a strong correlation between the USG-measured depth and the actual needle depth.
Keywords: attempts, epidural, infraumbilical surgeries, landmark guidance, ultrasonography guidance
|How to cite this article:|
Sahu DK, Ramteke JH, Sharma A, Parampill R, Patel C. Comparison of the ultrasonography-guided technique and conventional anatomical landmark technique for localization of epidural space during epidural block. Res Opin Anesth Intensive Care 2018;5:246-51
|How to cite this URL:|
Sahu DK, Ramteke JH, Sharma A, Parampill R, Patel C. Comparison of the ultrasonography-guided technique and conventional anatomical landmark technique for localization of epidural space during epidural block. Res Opin Anesth Intensive Care [serial online] 2018 [cited 2018 Oct 16];5:246-51. Available from: http://www.roaic.eg.net/text.asp?2018/5/3/246/240263
| Introduction|| |
Anatomical landmarks are useful markers but difficult to palpate in the obese and those with edema in the back, previous spine surgery and frequently (70%) lead to incorrect identification of a given lumbar interspace. The loss of resistance (LOR) technique is the gold standard but a blind technique . Reducing the technical difficulty of neuraxial blockade is desirable because multiple needle insertion attempts may increase the risk of complications, such as postdural puncture headache, paresthesia, and epidural hematoma .
Meta-analysis suggest that use of ultrasonography (USG) improves the precision and efficacy of neuraxial anesthetic techniques ,. Therefore, the need of this study is to find whether the USG-guided technique is superior than landmark-guided technique for epidural space localization. In this study we hypothesized that there is no difference in the preprocedure USG scanning and the conventional anatomical landmark-guided technique in terms of time and number of attempts taken to localize epidural space. Primary objectives of studies were to compare the time taken to localize epidural space; number of attempts taken to localize epidural space with conventional anatomical landmark technique versus the USG-guided technique. Secondary objectives were to measure vertical and oblique distance from skin to ligamentum flavum (LF), number of times the cortex of bone touched by the epidural needle, ultrasound visibility score (UVS) of nine neuraxial structures and to document any direct complications related to the above procedure.
| Patients and methods|| |
After approval by the institutional research and ethical committee of hospital, 76 adult patients posted for elective infraumbilical surgeries receiving epidural block were enrolled in the study. Duration of the study was 1 year (May 2015–April 2016). It was a prospective randomized open-label comparative study. Patients were equally divided into two groups as per randomization table taken from www.randomization.com. They were divided in two groups. In group 1, anatomical landmark-guided technique and in group 2, preprocedural USG scan was used for puncture site determination. Patients fulfilling the inclusion and exclusion criteria were approached. Inclusion criteria were age of 40–65 years either sex, BMI (18–30), American Society of Anesthesiologist physical status I–III. Exclusion criteria were infection at the site of infection, patient refusal, significant coagulopathies, and history of allergy to local anesthetic agents, and previous spine surgery or spine deformity. Patients were included after taking written consent and the process was explained in the local language. Demographic data, BMI were recorded.
In group 1, anatomical landmarks were used for epidural space localization (tuffiers line). The Tuohy needle was inserted in the desired intervertebral space (e.g. L3–L4 or L4–L5) and a standard LOR syringe filled with ∼2 ml of air was attached to the hub of the needle. The needle was then slowly advanced, millimeter by millimeter. As the tip of the needle just entered the epidural space, there was a sudden LOR, and injection was easy. The depth of the needle was marked with sterile marker and recorded later by measuring tape. The reason of measuring the length of needle insertion in the group 1 was to confirm that whether both groups were comparable in terms of epidural space depth.
In group 2, the preview USG scan was performed in preoperative room. A portable USG machine (Titan; SonoSite Inc., Bothell, Washington, USA) with a curvilinear probe (2–5 MHz frequency) was used for the procedure.
The patient was placed in a sitting position. The probe was placed in paramedian sagittal approach at the lower back to identify the sacrum and then the desired level of the spine. We oriented the probe toward midline to achieve ‘saw-tooth’ appearance indicating lamina and interlaminar space  ([Figure 1]). The transducer was finally positioned over the desirable interlaminar space. Measurements were taken on the still image after freezing the scan. The distance between skin to LF was measured using built-in calipers on the USG machine in parasagittal view (oblique distance between skin and LF).
|Figure 1 Paramedian sagittal view showing sacrum with classic ‘saw-tooth’ appearance representing lamina and interlaminar space.|
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We rotated the probe by 90° at a desired intervertebral space (e.g. L3–L4 space). Transverse view at spinous process shows ‘tower’ sign indicating the spinous process  ([Figure 2]). We marked the spinous process of respective vertebrae then moved transducer upwards and downwards to mark spinous process of respective vertebrae. By joining these points we got a longitudinal line representing midline of the spine ([Figure 3]a).
|Figure 3 Transverse interspinous view showing bat sign. Posterior complex (PC) is represented by ligamentum flavum (LF) and Posterior dura (PD). Lamina, Transverse process (TP), Anterior complex (anterior dura, anterior epidural space, posterior longitudinal ligament, and the posterior aspect of the vertebral body) are also visualized.|
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When the probe was placed on the desired intervertebral space(e.g. L3–L4), ‘tower’ sign get disappeared and ‘flying bat’ sign then emerged  ([Figure 4]). We initially held at 90° to the skin and angled the probe in cephalad direction in small increments until the best view of interlaminar space has been found. This angle could not be measured but we kept in mind this angle while needle insertion. We marked on both sides of probe in transverse view using surgical marker  ([Figure 3]b). We joined these marks to draw a transverse line. The measurements were taken on the still image after freezing the scan. The distance from skin to LF was measured using built-in calipers on the USG machine in transverse view (vertical distance between skin to LF).
Puncture site was determined by the intersection of these two lines, that is, longitudinal line and transverse line ([Figure 3]c).
The Tuohy needle was advanced through puncture site to the epidural space. Needle was stopped 2–3 mm before the distance between skin to LF determined by ultrasound study. Epidural space was confirmed by testing for LOR to injection of air through the Tuohy needle using the standard LOR syringe. The distance at which we got epidural space, is indicated by sudden LOR with standard LOR syringe, the needle was marked with sterile marker and recorded with a measuring tape (actual epidural space depth).
Patients were monitored for the time taken for localization of epidural space, that is, time taken for skin puncture by Tuohy needle to localization of epidural space with standard LOR syringe, numbers of attempt for localization of epidural space (the number of attempts was defined as the number of skin puncture points by a single provider), number of times the cortex of bone touched by the needle and if any complication like dural puncture, intravascular injection were looked for.
Additionally, we measured the vertical (by freezing the scan in transverse view) and oblique distances (by freezing the scan in paramedian view) from the skin to LF, respectively, and the UVS of nine neuraxial structures  (lamina, LF, interlaminar space, epidural space, posterior dura, intrathecal space, cauda equine, pulsations of the cauda equine, and anterior dura-posterior longitudinal ligament complex) were noted in scale of 0–3 (0, not visible; 1, hardly visible; 2, well visible; 3, very well visible, maximum score possible=27) and the total UVS was determined for every patient.
The sample size was calculated based on mean and SD of earlier studies . By taking means of both groups, 80% power and 95% confidence interval, sample size was found to be 38 per group. After data collection, data entry was done in Excel. Data analysis was done with the help of SPSS software (IBM, Mumbai, India), version 15, and Sigma Plot (Systat, Mumbai, India), version 12. Quantitative data variables were presented with the help of mean, SD, median, and interquartile range. Comparison among study group was done with the help of unpaired t test or Mann–Whitney test as per results of normality tests. P value less than 0.05 was taken as the significant level.
| Results|| |
Both groups were comparable with respect to demographic characteristics, that is, age, sex, BMI, and intervertebral space selected ([Table 1]). Mean time taken for insertion of epidural needle in group 1 was 72.21±45.64 s. Mean time taken for insertion of epidural needle in group 2 was 54.82±40.87 s. The difference between the two was statistically significant (P=0.027) ([Table 1]). The mean number of attempts in the USG-guided group was 1.11±0.39, whereas in landmark-guided group it was 1.32±0.53. The difference was significant (P=0.02) ([Table 1]). In our study the epidural space was located in first attempt in 27 (71.1%) individuals of group 1 and 35 (92.1%) individuals of group 2 ([Figure 5]). The mean number of times the needle touched the bone in group 1 was 0.97±1.17 and in group 2 was 0.66±0.85. It was not significant (P=0.317). The Pearson’s correlation coefficient between the USG-measured-vertical distance between skin to LF and actual epidural space depth by needle mark in the USG-guided group was 0.965 (P=0.0001) and between USG-measured-oblique distance between skin and LF and actual epidural space depth by needle mark in the USG-guided group was 0.960 (P=0.0001). The difference is significant ([Table 2] and [Table 3]). Mean UVS was 20±2.42 in group 2 with no visibility of pulsations of the cauda equine in any case probably due to adult patients in the study. In our study we had two dural punctures in group 1 and one dural puncture in group 2. No other complications like bloody taps, dry taps, or any other complications were found in our study.
|Table 3 Showing correlation between the ultrasonography-measured distances with actual distances in group 2|
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| Discussion|| |
The scope of ultrasound imaging guidance for regional anesthesia is growing rapidly. Data suggest that ultrasound can improve block success rate and decrease complications. Several factors can cause procedural difficulty during spinal or epidural technique including obesity, spinal deformity, and previous spinal surgery. USG can be useful to identify midline, to predict the depth of epidural space and to direct the insertion needle.
In our study, with respect to demographic variables and BMI, both the groups were comparable. We observed that, mean time taken for localization of epidural space by epidural needle in the USG-guided group was less than landmark-guided group. First attempt localization of epidural space was more in the USG-guided group individuals than landmark-guided one. The mean number of attempts in the USG-guided group was less. The Pearson’s correlation coefficient between the USG-measured distance between skin to LF and the actual epidural depth by needle mark in the USG-guided group was significant. Thus a preview of USG scan can be used to accurately predict the depth of insertion of epidural needle. No significant complications were found in both the study groups.
For neuraxial USG we need of large curvilinear transducers to achieve adequate depth and field of view. The size of these transducers make them cumbersome to use in real-time procedures and is difficult to maintain in one position on the back of a sitting patient . Real-time techniques are possible in a paramedian approach only. Thus in this study, we used USG for marking only the entry point of the needle during the epidural block and to estimate the depth of the needle and not for real-time visualization.
Systemic review, meta-analysis , and also various other studies ,,, have found that ultrasound imaging can reduce the risk of failed or traumatic lumbar punctures and epidural catheterizations, as well as minimize the number of needle insertions. The rate of successful puncture at the first puncture site was significantly higher in the ultrasound group than the landmark group. There is an excellent correlation between ultrasound-measured depth and needle-insertion depth to the epidural or intrathecal space. These advantages led the National Institute of Clinical Excellence (NICE) in the United Kingdom to recommend the routine use of ultrasound for epidural blocks .
One limitation of our study was that the angle of insertion of epidural needle was neither determined nor measured. The variable angle of insertion used in this study could contribute to the difference between ultrasound-measured depth and the actual epidural space depth measured by the needle.
Identification of the landmarks by ultrasound can be learned in short period through practical experience. We believe that most of the significant change in this area will be in the development of specialized novel equipment, such as the electromagnetic-based needle-guided system, 3D/4D ultrasound systems, echogenic Tuohy needle, or ultrasound transducers embedded within the needle . Adequate training in neuraxial ultrasound is needed especially in postgraduate institutes. Ultrasound is the future of safe regional anesthesia.
| Conclusion|| |
We concluded that the USG-guided epidural space localization reduced the time taken to insert the epidural needle and it also attempted for the localization of epidural space. With the use of USG, the depth of epidural space can be measured more accurately.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]