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The Development of a Novel Device Based on Loss of Guidewire Resistance to Identify Epidural Space in a Porcine Model

The Development of a Novel Device Based on Loss of Guidewire Resistance to Identify Epidural... Hindawi Journal of Healthcare Engineering Volume 2020, Article ID 8899628, 7 pages https://doi.org/10.1155/2020/8899628 Research Article The Development of a Novel Device Based on Loss of Guidewire Resistance to Identify Epidural Space in a Porcine Model 1 2 1 1 1 Jaeyoung Yang , Rakmin Choi, Kyubum Cho, Seonjin Kim, Bousung Lee, 1 1 1 Kwanghaeng Lee, Dongseok Kim, and Jaedo Lee Department of Anesthesiology and Pain Medicine, Veterans Health Service Medical Center, Seoul, Republic of Korea Department of Anesthesiology and Pain Medicine, Armed Forces Capital Hospital, Seongnam, Republic of Korea Correspondence should be addressed to Jaeyoung Yang; yang303@gmail.com Received 12 June 2020; Accepted 31 July 2020; Published 24 August 2020 Academic Editor: Daniel Espino Copyright © 2020 Jaeyoung Yang et al. $is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. $e application of additive manufacturing (3D printing) has been recently expanded to various medical fields. $e new technique named loss of guide wire resistance (LOGR) was developed via 3D printing for the detection of epidural space using a guide wire instead of air or saline used in the loss of resistance (LOR) technique. Methods. $e prototype model of epidural space finder consists of a polyactic acid (PLA) or a resin. It was manufactured with 3D printing. Biocompatibility test (eluate and sterility tests) was performed in both products. $e advantage of the newly developed device was compared with conventional loss of resistance (LOR) technique in a porcine model. Results. Eluate and sterility tests revealed that the PLA was more biocompatible than the resin. $e LOGR technique facilitated rapid access to epidural space compared with the LOR technique (41.64± 32.18 vs. 92.28± 61.46 seconds, N � 14, p � 0.0102, paired sample t-test), without any differences in success rate (87.5%). Conclusion. We conclude that LOGR technique is comparable to LOR technique to access the epidural space, although the advantage of either technique in terms of complications such as dural puncture or epidural hematoma is unknown. We demonstrated the potential benefit of 3D printer for the development of a new medical device for anesthesia. report the use of 3D printing for the development of epidural 1. Background space finder, made of polyactic acid (PLA) or resin. $e Additive manufacturing, also known as three-dimensional principle is based on the release of guidewire resistance of printing, is a rapid prototyping technology. $ree-dimen- the new epidural space finder when the needle is inserted sional solid objects can be generated from a digital model into the epidural space. A biocompatibility test was con- designed by a computer. It provides a huge opportunity for ducted to determine the biological safety of 3D printing rapid manufacture of medical implants, surgical planning, products. $e usefulness of the newly developed device was and education [1]. In medical field, the most significant compared with conventional loss of resistance technique in a porcine model. $e PLA model was more biocompatible advance in 3D printing application mainly relates to surgery, especially in surgical planning of facial surgery, neurosur- than the resin model. $e newly developed epidural space gery, and cardiothoracic and orthopedic surgeries [2–5]. finder (loss of guidewire resistance technique (LOGR)) $ree-dimensional printing was used for the manufacture of represents a potential alternative to the loss of resistance prostheses in orthopedics [6]. $e 3D printed anatomical (LOR) technique. model based on radiographic images was used to educate surgeons and students [7, 8]. In anesthesiology, 3D printing 2. Methods is used for ultrasound training or planning of tracheal in- tubation [9, 10], We explored the role of 3D printing for the 2.1. 3D Printing. A 3D printable model was created with development of medical devices in anesthesiology. We Fusion360 (Autodesk Inc., San Rafael, CA, USA) software 2 Journal of Healthcare Engineering and saved in a stereolithography file format (STL). $e STL (4) Absorbance: Ultraviolet absorption tests were con- file was converted into a G-code file containing a series of ducted to identify unknown substances with invisible ultraviolet light. $e absorbance of the test solution thin layers with ideaMaker 3.3.0 for fused deposition modeling (FDM) printing and A-series desktopslicer 0.9.1 was analyzed using the blank test solution as a for stereolithography (SLA) printing. In FDM printing, control, and the maximum absorbance at each in- Raise 3DPro2 plus (Raise3D, Irvine, CA, USA) was used to terval of 250–350 nm was recorded. create an epidural space finder model using a 1.75 mm (5) Evaporation residue test: an evaporation residue test polylactic acid (PLA) filament (Raise3D, Irvine, CA, USA). was conducted to determine whether an unknown $e print settings were 0.05 mm of layer height with 0.4 mm substance was eluted in the eluting solvent. A 10 mL nozzle size at a nozzle temperature of 215 C. In SLA printing, of the sample solution was taken and evaporated, and Sindoh A1 + SLA (Sindoh, Seoul, South Korea) was used to the residue was dried at 105 C for 1 hour and the print the 3D model using ABS-like resin (Sindoh, Seoul, difference in weight before and after evaporation was South Korea). $e print settings were 0.1 mm layer height calculated. and 405 nM laser wavelength. (6) Heavy metal tests: Heavy metal tests were conducted to determine whether heavy metals (unknown diva- lent heavy metal ions) were eluted. After taking 10 mL 2.2. Biocompatibility Test (Sterility and Extractable Substance). each of the sample and blank test solutions in a Extractable substance and sterility tests were performed at Nessler tube, 2 mL of lead standard solution (10 ppm) KBIO Health and Medical Device Development Center was added to the blank. $ree drops of sodium sulfide (KBIO Osong Medical Innovation Foundation, Chungbuk, and 2 mL of diluted acetic acid were added to the South Korea). $e two gears of the 3D print models in PLA sample and blank solution, and the solution colors or Resin were sterilized with Ethylene oxide (EO) gas and were compared on a white background. sent to the test facility. $e elution test was performed and analyzed according to the dissolution test and the heavy metal tests developed by 2.2.2. Sterility Test. Sterility tests were conducted according the Korean Pharmaceutical Plastic Container Test Method to ISO 11737-2. An anaerobic strain (Clostridium spor- [11]. ogenes), two fungi (Candida albicans, Aspergillus brasi- For the preparation of the test substance, distilled water liensis), and three aerobic strains (Staphylococcus aureus, was used as extractant, and 4.0 g of the sample was eluted at Bacillus subtilis, and Pseudomonas aeruginosa) were used. 37± 1 C for 72 hours to obtain a sample solution. Anaerobic strains were cultured in fluid thioglycollate medium (FTM), whereas fungal and aerobic strains were grown in tryptic soy broth (TSB). A medium performance 2.2.1. Extractable Substances Test test was conducted before the main test. FTM was inoculated with C. sporogenes, P. aeruginosa, and S. aureus at (1) Appearance: After elution, 5 mL of the sample so- 32.5± 2.5 C. TSB was inoculated with A. brasiliensis, B. lution was placed in a test tube and observed on a subtilis, and C. albicans at 22.5± 2.5 C. $is test was con- white background. ducted by direct method. Samples were inoculated up to 10% (2) pH (acidity and alkalinity): $e test used 20 mL of of the media volume. After inoculation, FTM was cultured at each sample and blank test solution, and 1.0 g of ° ° 32.5± 2.5 C and TSB at 22.5± 2.5 C for at least 14 days. calcium chloride was dissolved in water, to which 1.0 mL of a 1000 mL solution was added. $e pH of the two solutions was measured. 2.3. Anesthesia and Monitoring. Experiments were per- (3) Reducing substance: A potassium permanganate formed at KBIO Health Animal Testing Center of the reduction test was conducted to determine the Medical Device Development Center (Osong Medical In- presence of organic or inorganic substances in the novation Foundation, Osong, Chungbuk, South Korea) elution solvent using potassium permanganate, a following approval of the Institutional Animal Care and Use powerful oxidizing agent. A 10 mL of the sample Committee (KBIO-IACUC-2019-115). Two pigs (Cronex, solution in a stoppered conical flask was mixed Hwaseong-si, Gyeonggi-do, South Korea) were used for the with 1 mL of dilute sulfuric acid, followed by the test (Yorkshire, Male, 38-39 kg). addition of 20.0 mL of 0.002 mol/L potassium Healthy animals were observed and quarantined for 7 permanganate solution. $e mixture was boiled for days. $e experiments were conducted using healthy ani- 3 minutes, cooled, mixed with 0.10 g of potassium mals after 7 days of acclimation. $e animals were fasted a iodide, stirred well, shaken, and left for 10 minutes. day before the test. Atropine sulphate (Cheil Pharmaceu- $e reaction was titrated with 0.01 mol/L sodium tical, Daegu, Korea) 0.06 mg/kg was intramuscularly injected thiosulfate. $e same procedure was repeated on the day of the experiment to prevent bradycardia, a side using 10.0 mL of blank test solution. $e difference effect of anesthesia. in the consumption of 0.002 mol/L potassium Zoletil (Birbackorea, Seoul, South Korea) 6 mg/kg and permanganate solution of the sample and the blank Rompun (Bayer Korea, Ansan, Korea) 2 mg/kg were injected test solutions was calculated. intramuscularly for anesthesia induction. After airway Journal of Healthcare Engineering 3 2.5. Statistical Analysis. Data were analyzed using the Excel intubation, general anesthesia was maintained with 3% isoflurane (Fabius GS premium, Drager, Germany). program (Microsoft Corporation, Seattle, WA, USA) and RexSoft (2018, Rex: Excel-based statistical analysis software. During anesthesia, electrocardiography (ECG), oxygen saturation, and expiratory carbon dioxide concentration URL http://rexsoft.org/). $e tests for normal distribution were measured with a Vista 120 monitoring system (Drager, were performed using Shapiro-Wilk test for small sample Germany). $e animal was laid in the prone position and the sizes. $e means of data were compared with the paired limbs were fixed. Radiography was then performed using an sample t-test. When the p-value is less than 0.05, it is angiography machine (Artis Zee Multi-Purpose, Siemens, considered statistically significant. Germany). After animal experiments, animals were euthanized by 3. Results inducing cardiac arrest through intravenous infusion of large amounts of KCl through a catheter mounted in the vein $e basic concept of operation involving the new epidural of the ear under anesthesia (5% or more of isoflurane). space finder can be explained as follows. While the needle advances into the lumbar epidural space, a turning force is exerted on the dials ((1) in Figure 1) on both sides of the 2.4. Porcine Experiment. $e porcine experiment for epi- instruments to continue pushing the wire into the Tuohy dural space analysis was conducted in two piglets by a single needle ((2) in Figure 1). When the needle entered the anesthesiologist. A PLA model, printed with an FDM 3D epidural space, the resistance of the dials is released, and the printer, was sterilized with EO gas and used in the exper- guidewire moved forward smoothly. iment. $e interlaminar space between L1-2 and L4-5 was Different types of 3D printing materials are available, identified radiographically and marked at each level. $e such as acrylonitrile butadiene styrene (ABS), photopolymer guidewire and 14-gauge Tuohy needle, adapted from the resin, polylactic acid (PLA), polypropylene, high-density spinal cord stimulator trial kit (Medtronic inc, Minneapolis, polyethylene (HDPE), nylon, and polycarbonate (PC) [1]. MN, USA), were used. $e two methods including LOR and $e PLA and photopolymer resins were selected for the LOGR (epidural space finder printed with 3D printer) were production test due to their popularity in 3D printing. $e used randomly and sequentially to access the epidural space epidural space finder consists of two dials and one cage. Each via a paramedian approach at each level. A Touhy needle was printed part was assembled from two sterilized 35 mm M3 located and targeted under fluoroscopic guidance. Imme- bolts and nuts. $e two dials were tightened with a sterilized diately after penetrating the thick skin of the pig, the needle rubber band (Figures 1 and 2). $e epidural space finder trajectory from the skin to epidural space was estimated made of two materials was used for biocompatibility testing under fluoroscopic guidance. Immediately after skin pen- (sterility and extractable substance). etration, the needle was advanced 1 cm. A color change of the eluting solvent was observed in the When LOR technique was used to identify the epidural extractable substance test, which confirmed the plasticizer, space, as the needle was advanced through ligamentum lubricant, stabilizer, and pigment from the eluate in both flavum, a constant pressure was applied on the syringe until PLA and resin products. $e difference in pH between the loss of resistance occurred. $e plunger of the syringe was blank and the test solution was 0.07 in PLA and 0.58 in resin, gently withdrawn to assess the dural puncture. To confirm which is smaller than the test standard indicated in Korean the epidural space entry, the guidewire was advanced a few Pharmacopoeia (pH � 1.5) (Table 1). centimeters into the epidural space. $e difference in the consumption of potassium per- When LOGR (epidural space finder) was used, the manganate solution confirmed the presence of organic or guidewire replaced the air in the LOR technique. While inorganic substances. $e difference between the potassium advancing the needle through ligamentum flavum, adequate permanganate consumption of the blank and the sample force was exerted to ensure constant rotation of dials on both solutions was 0.128 mL in the PLA product but 5.75 mL in sides of the epidural space finder to generate resistance on resin (the test standard< 2 mL) (Table 1). the guidewire of the device. When the needle entered the In the ultraviolet absorption test used to identify the epidural space, the dial lost the resistance and the guidewire unknown substance with the ultraviolet light, the differences moved a few centimeters ahead smoothly into the epidural in absorbance between blank and sample solutions were space. After the procedure was completed, the epidural space 0.0002 AU for the PLA product and 3.927 in the resin finder and guidewire were removed, and a glass syringe was product (test standard< 0.1 AU) (Table 1). connected to a Touhy needle. $e plunger of the syringe was $e results of quantitative evaporation residue test gently withdrawn to determine the dural puncture. showed that 0.2 mg of PLA product and 12.9 mg of resin $e epidural space approach was confirmed by ad- product were eluted (the test standard of<1.0 mg) (Table 1). vancing the guidewire and radiographic image. $e time In order to determine if the heavy metals were eluted taken to advance the needle by 1 cm from the skin to the from the eluate, the color changes in the heavy metal re- epidural space was recorded. $e depth from the skin to action between the standard and the test solutions revealed epidural space was measured using the radiographic image. no differences in both PLA and resin product (Table 1). If more than three attempts were made to identify the $e medium performance test was performed to test the epidural space, it was marked as a failed attempt and the culture media. All the strains were appropriate for FTM and procedure was stopped to minimize the animal damage. TSB. $e color of the medium was changed, which R8.25 4 Journal of Healthcare Engineering (1) (2) (1) 29.5 Figure 1: $e basic concept of operation in the epidural space finder (up) and blueprint for epidural space finder (bottom) (dimensions in mm). (a) (b) (c) Figure 2: 3D printed epidural space finder (PLA product (left), resin product (middle), and assembled epidural space finder (right)). confirmed that all the strains were cultured when inoculated Based on the results of both experiments, the PLA into the selection medium. In this test, after 14 days of product was more biocompatible than the resin product. incubation, both FTM and TSB medium did not turn white We decided to use the porcine model to determine the and were deemed negative in PLA and resin product usefulness of the new LOGR compared with LOR technique (Table 2). to identify epidural space. In order to reduce false-positive R1.5 16.5 16.5 80 Journal of Healthcare Engineering 5 Table 1: Results of extractable substance test ( : test standard value created a new LOGR device (epidural space finder) to of Korean Pharmacopoeia [11]). identify epidural space. Our newly developed device is in direct contact with the PLA-FDM Resin-SLA epidural guidewire but not with the subject body. After Appearance (clear ) Clear Clear consulting with a biocompatibility specialist at KBIO Health, pH (<1.5) 0.07 0.58 we decided to perform extractable substance and sterility test Reducing substance (<2 mL) 0.1282 mL 5.75 mL but not the cytotoxic test. In the biocompatibility test, the UV absorbance (<0.1) 0.002 3.927 resin released a higher number of unknown organic or Residue on evaporation (<1.0 mg) 0.2 mg 12.9 mg Heavy metal (negative) Negative Negative inorganic substances than the PLA. Both materials were not certified biocompatible but were generally found in a regular 3D print store. PLA is a well-known biodegradable and biocompatible Table 2: Results of sterility test. polymer, which can be produced from the fermentation of PLA-FDM Resin-SLA corn or sugarcane. PLA is one of the most successful bio- polymers with a diverse range of biomedical applications, Fluid thioglycollate medium (FTM) No growth No growth Trypticase soy broth (TSB) No growth No growth such as drug delivery, implants, and tissue engineering [14]. Light-activated resin (photopolymer) contains a monomer and an oligomer cross-linked by light and pho- insertion into epidural space and to minimize animal sac- toinitiator, which generate free radicals that interact with the rifice, the needle trajectory into epidural space was estimated monomer to induce the polymerization chain reaction [15]. under fluoroscopic guidance immediately after penetrating Toxicity varies with the nature of the resin substance. For the skin with Touhy needle (Figure 3). example, bisphenol A-glycidyl-methacrylate (BisGMA) is In two pigs, 14 of 16 epidural insertion attempts were more cytotoxic and genotoxic than triethylene glycol successful via both methods (87.5% success rate). $ere was dimethacrylate (TEGDMA) monomers [16]. no significant difference between the number of attempts in It is not clear whether the substances released from the LOGR and LOR groups (1.38± 0.81 vs. 1.25± 0.68, resin products are harmful to humans, because no cytotoxic p � 0.317, N for each group � 14, paired sample sign test). A tests such as MTT (3-[4,5-dimethylthiazole-2-yl]-2,5- significant difference was observed in the average time taken diphenyltetrazolium bromide) assays were conducted. Even for epidural approach between LOGR and LOR groups though biocompatible resins are commercially available, it is (41.64± 32.18 vs. 92.28± 61.46 seconds, N for each certain that PLA is safer than the resin, at least in our group � 14, p � 0.0102 paired sample t-test). $e mean experiment. depth measured from skin to epidural space was not sig- In the porcine model, the LOGR technique was faster nificantly different between LORG and LOR groups than the LOR technique in facilitating access to the epidural (34.14± 7.9 vs. 36.25± 7.29 mm, N for each group � 14, space. However, no difference in success rate was observed. p � 0.1174, paired sample t-test) (Figures 3 and 4). When We could not completely evaluate the procedure related the dural puncture was tested by withdrawing the syringe complications such as dural puncture, because no radi- plunger at every attempt, no cerebrospinal fluid (CSF) reflux opaque contrast dye was injected after the epidural approach was observed. to minimize the porcine sacrifice. We evaluated the CSF reflux after each experiment; however, it is not a reliable method to confirm dural puncture. It is reasonable to 4. Discussion conclude that LOGR and LOR techniques are comparable in Different techniques are used to identify the location of their ability to provide access to the epidural space. However, epidural space during epidural anesthesia or catheter in- it was not clear which technique was associated with fewer sertion such as LOR, optical spectroscopy, ultrasound, and complications such as dural puncture or epidural hema- toma. Further studies are needed to establish the adverse optical coherence tomography [12]. LOR to air or saline technique is the most frequently used method in common effects associated with LOGR technique. Most of the 3D printing applications in anesthesiology to medical practice. Even though LOR technique is simple and easy to perform with a syringe without other complex date focus on rapid production, reduced manufacturing cost, and ability to provide a delicate printing design for anes- devices, it requires substantial training to perform cor- rectly and it is not reliable because of its high false-positive thesia planning or medical training. In addition, we sought to determine the potential of 3D printers in the manufacture rates of up to 30% [13]. In bedside epidural procedures, we frequently use epidural catheter insertion as an adjunct to of products anywhere in the world outside the factories. LOR technique to confirm the true epidural space. When $erefore, we tested PLA and resin, the materials used most loss of resistance is detected, and if epidural catheter often for 3D printing. Using these materials in a hospital, we cannot advance through the epidural needle, the tip of the can print our own devices with an inexpensive 3D printer. In summary, a 3D printer can be used to develop new needle may not be in the epidural space. For a long time, we sought to develop a device that combined the advan- medical devices for anesthesia and can also be used as an effective substitute when the normal supply chain collapses tages of LOR and catheter insertion. After designing several prototypes with 3D printing, we successfully such as in a war, earthquake, or typhoon. 6 Journal of Healthcare Engineering (a) (b) Figure 3: Lateral fluoroscopic image of epidural catheter insertion in porcine experiments: LOR technique (left) and LOGR technique (right). LOR LOGR LOR LOGR (a) (b) Figure 4: Boxplots comparing the duration of epidural approach (left) and the depth of epidural space (right) between LOR and LOGR techniques. Abbreviations Ethical Approval PLA: Polyactic acid Experiments were performed at KBIO Health Animal LOR: Loss of resistance Testing Center of the Medical Device Development Center LOGR: Loss of guide wire resistance (Osong Medical Innovation Foundation, Osong, Chungbuk, FDM: Fused deposition modeling South Korea) following approval of the Institutional Animal SLA: Stereolithography Care and Use Committee (KBIO-IACUC-2019-115). FTM: Fluid thioglycollate medium TSB: Tryptic soy broth Conflicts of Interest ABS: Acrylonitrile butadiene styrene (ABS) $e authors declare that they have no conflicts of interest. PLA: Polylactic acid HDPE: High-density polyethylene PC: Polycarbonate Authors’ Contributions CSF: Cerebrospinal fluid J. Yang contributed to study design, animal experiment, and BisGMA: Bisphenol A-glycidyl-methacrylate writing and confirming the first and final draft of the paper. TEGDMA: Triethylene glycol dimethacrylate. R. Choi contributed to 3D printing of the prototype. K. Cho contributed to data analysis. S. Kim contributed to data Data Availability analysis and graph drawing. B. Lee contributed to 3D $e data used in the study are available on request. printing and animal experiment. K. Lee contributed to Seconds Mm Journal of Healthcare Engineering 7 space,” Asian Journal of Anesthesiology, vol. 55, no. 2, communication with KBIO Health for biocompatibility test. pp. 30–34, 2017. D. Kim contributed to data collection and 3D modeling [13] A. H. White, R. Derby, and G. Wynne, “Epidural injections for software handling. J. Lee contributed to revision of the final the diagnosis and treatment of low-back pain,” Spine, vol. 5, draft of the paper. no. 1, pp. 78–86, 1980. [14] M. S. Singhvi, S. S. Zinjarde, and D. V. Gokhale, “Polylactic acid: Synthesis and biomedical applications,” Journal of Ap- Acknowledgments plied Microbiology, vol. 127, no. 6, pp. 1612–1626, 2019. $e authors thank KBIO Osong Medical Innovation [15] A. B. Scranton, C. N. Bowman, and R. W. Peiffer, American Chemical Society. Division of Polymeric Materials: Science and Foundation (Osong, Chungbuk, South Korea) for assistance Engineering., American Chemical Society. Meeting. Photo- with animal experiments and biocompatibility tests. $e polymerization: fundamentals and applications, American study received VHS Medical Center Research Grant, Re- Chemical Society, Washington, DC, USA, 1997. public of Korea (VHSMC 19034). [16] D. Manojlovic, M. D. Dramicanin, ´ V. Miletic, D. Mitic- ´ ´ ´ ´ Culafic, B. Jovanovic, and B. Nikolic, “Cytotoxicity and genotoxicity of a low-shrinkage monomer and mono- References acylphosphine oxide photoinitiator: comparative analyses of [1] A. Aimar, A. Palermo, and B. 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The Development of a Novel Device Based on Loss of Guidewire Resistance to Identify Epidural Space in a Porcine Model

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Hindawi Publishing Corporation
Copyright
Copyright © 2020 Jaeyoung Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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2040-2295
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2040-2309
DOI
10.1155/2020/8899628
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Abstract

Hindawi Journal of Healthcare Engineering Volume 2020, Article ID 8899628, 7 pages https://doi.org/10.1155/2020/8899628 Research Article The Development of a Novel Device Based on Loss of Guidewire Resistance to Identify Epidural Space in a Porcine Model 1 2 1 1 1 Jaeyoung Yang , Rakmin Choi, Kyubum Cho, Seonjin Kim, Bousung Lee, 1 1 1 Kwanghaeng Lee, Dongseok Kim, and Jaedo Lee Department of Anesthesiology and Pain Medicine, Veterans Health Service Medical Center, Seoul, Republic of Korea Department of Anesthesiology and Pain Medicine, Armed Forces Capital Hospital, Seongnam, Republic of Korea Correspondence should be addressed to Jaeyoung Yang; yang303@gmail.com Received 12 June 2020; Accepted 31 July 2020; Published 24 August 2020 Academic Editor: Daniel Espino Copyright © 2020 Jaeyoung Yang et al. $is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. $e application of additive manufacturing (3D printing) has been recently expanded to various medical fields. $e new technique named loss of guide wire resistance (LOGR) was developed via 3D printing for the detection of epidural space using a guide wire instead of air or saline used in the loss of resistance (LOR) technique. Methods. $e prototype model of epidural space finder consists of a polyactic acid (PLA) or a resin. It was manufactured with 3D printing. Biocompatibility test (eluate and sterility tests) was performed in both products. $e advantage of the newly developed device was compared with conventional loss of resistance (LOR) technique in a porcine model. Results. Eluate and sterility tests revealed that the PLA was more biocompatible than the resin. $e LOGR technique facilitated rapid access to epidural space compared with the LOR technique (41.64± 32.18 vs. 92.28± 61.46 seconds, N � 14, p � 0.0102, paired sample t-test), without any differences in success rate (87.5%). Conclusion. We conclude that LOGR technique is comparable to LOR technique to access the epidural space, although the advantage of either technique in terms of complications such as dural puncture or epidural hematoma is unknown. We demonstrated the potential benefit of 3D printer for the development of a new medical device for anesthesia. report the use of 3D printing for the development of epidural 1. Background space finder, made of polyactic acid (PLA) or resin. $e Additive manufacturing, also known as three-dimensional principle is based on the release of guidewire resistance of printing, is a rapid prototyping technology. $ree-dimen- the new epidural space finder when the needle is inserted sional solid objects can be generated from a digital model into the epidural space. A biocompatibility test was con- designed by a computer. It provides a huge opportunity for ducted to determine the biological safety of 3D printing rapid manufacture of medical implants, surgical planning, products. $e usefulness of the newly developed device was and education [1]. In medical field, the most significant compared with conventional loss of resistance technique in a porcine model. $e PLA model was more biocompatible advance in 3D printing application mainly relates to surgery, especially in surgical planning of facial surgery, neurosur- than the resin model. $e newly developed epidural space gery, and cardiothoracic and orthopedic surgeries [2–5]. finder (loss of guidewire resistance technique (LOGR)) $ree-dimensional printing was used for the manufacture of represents a potential alternative to the loss of resistance prostheses in orthopedics [6]. $e 3D printed anatomical (LOR) technique. model based on radiographic images was used to educate surgeons and students [7, 8]. In anesthesiology, 3D printing 2. Methods is used for ultrasound training or planning of tracheal in- tubation [9, 10], We explored the role of 3D printing for the 2.1. 3D Printing. A 3D printable model was created with development of medical devices in anesthesiology. We Fusion360 (Autodesk Inc., San Rafael, CA, USA) software 2 Journal of Healthcare Engineering and saved in a stereolithography file format (STL). $e STL (4) Absorbance: Ultraviolet absorption tests were con- file was converted into a G-code file containing a series of ducted to identify unknown substances with invisible ultraviolet light. $e absorbance of the test solution thin layers with ideaMaker 3.3.0 for fused deposition modeling (FDM) printing and A-series desktopslicer 0.9.1 was analyzed using the blank test solution as a for stereolithography (SLA) printing. In FDM printing, control, and the maximum absorbance at each in- Raise 3DPro2 plus (Raise3D, Irvine, CA, USA) was used to terval of 250–350 nm was recorded. create an epidural space finder model using a 1.75 mm (5) Evaporation residue test: an evaporation residue test polylactic acid (PLA) filament (Raise3D, Irvine, CA, USA). was conducted to determine whether an unknown $e print settings were 0.05 mm of layer height with 0.4 mm substance was eluted in the eluting solvent. A 10 mL nozzle size at a nozzle temperature of 215 C. In SLA printing, of the sample solution was taken and evaporated, and Sindoh A1 + SLA (Sindoh, Seoul, South Korea) was used to the residue was dried at 105 C for 1 hour and the print the 3D model using ABS-like resin (Sindoh, Seoul, difference in weight before and after evaporation was South Korea). $e print settings were 0.1 mm layer height calculated. and 405 nM laser wavelength. (6) Heavy metal tests: Heavy metal tests were conducted to determine whether heavy metals (unknown diva- lent heavy metal ions) were eluted. After taking 10 mL 2.2. Biocompatibility Test (Sterility and Extractable Substance). each of the sample and blank test solutions in a Extractable substance and sterility tests were performed at Nessler tube, 2 mL of lead standard solution (10 ppm) KBIO Health and Medical Device Development Center was added to the blank. $ree drops of sodium sulfide (KBIO Osong Medical Innovation Foundation, Chungbuk, and 2 mL of diluted acetic acid were added to the South Korea). $e two gears of the 3D print models in PLA sample and blank solution, and the solution colors or Resin were sterilized with Ethylene oxide (EO) gas and were compared on a white background. sent to the test facility. $e elution test was performed and analyzed according to the dissolution test and the heavy metal tests developed by 2.2.2. Sterility Test. Sterility tests were conducted according the Korean Pharmaceutical Plastic Container Test Method to ISO 11737-2. An anaerobic strain (Clostridium spor- [11]. ogenes), two fungi (Candida albicans, Aspergillus brasi- For the preparation of the test substance, distilled water liensis), and three aerobic strains (Staphylococcus aureus, was used as extractant, and 4.0 g of the sample was eluted at Bacillus subtilis, and Pseudomonas aeruginosa) were used. 37± 1 C for 72 hours to obtain a sample solution. Anaerobic strains were cultured in fluid thioglycollate medium (FTM), whereas fungal and aerobic strains were grown in tryptic soy broth (TSB). A medium performance 2.2.1. Extractable Substances Test test was conducted before the main test. FTM was inoculated with C. sporogenes, P. aeruginosa, and S. aureus at (1) Appearance: After elution, 5 mL of the sample so- 32.5± 2.5 C. TSB was inoculated with A. brasiliensis, B. lution was placed in a test tube and observed on a subtilis, and C. albicans at 22.5± 2.5 C. $is test was con- white background. ducted by direct method. Samples were inoculated up to 10% (2) pH (acidity and alkalinity): $e test used 20 mL of of the media volume. After inoculation, FTM was cultured at each sample and blank test solution, and 1.0 g of ° ° 32.5± 2.5 C and TSB at 22.5± 2.5 C for at least 14 days. calcium chloride was dissolved in water, to which 1.0 mL of a 1000 mL solution was added. $e pH of the two solutions was measured. 2.3. Anesthesia and Monitoring. Experiments were per- (3) Reducing substance: A potassium permanganate formed at KBIO Health Animal Testing Center of the reduction test was conducted to determine the Medical Device Development Center (Osong Medical In- presence of organic or inorganic substances in the novation Foundation, Osong, Chungbuk, South Korea) elution solvent using potassium permanganate, a following approval of the Institutional Animal Care and Use powerful oxidizing agent. A 10 mL of the sample Committee (KBIO-IACUC-2019-115). Two pigs (Cronex, solution in a stoppered conical flask was mixed Hwaseong-si, Gyeonggi-do, South Korea) were used for the with 1 mL of dilute sulfuric acid, followed by the test (Yorkshire, Male, 38-39 kg). addition of 20.0 mL of 0.002 mol/L potassium Healthy animals were observed and quarantined for 7 permanganate solution. $e mixture was boiled for days. $e experiments were conducted using healthy ani- 3 minutes, cooled, mixed with 0.10 g of potassium mals after 7 days of acclimation. $e animals were fasted a iodide, stirred well, shaken, and left for 10 minutes. day before the test. Atropine sulphate (Cheil Pharmaceu- $e reaction was titrated with 0.01 mol/L sodium tical, Daegu, Korea) 0.06 mg/kg was intramuscularly injected thiosulfate. $e same procedure was repeated on the day of the experiment to prevent bradycardia, a side using 10.0 mL of blank test solution. $e difference effect of anesthesia. in the consumption of 0.002 mol/L potassium Zoletil (Birbackorea, Seoul, South Korea) 6 mg/kg and permanganate solution of the sample and the blank Rompun (Bayer Korea, Ansan, Korea) 2 mg/kg were injected test solutions was calculated. intramuscularly for anesthesia induction. After airway Journal of Healthcare Engineering 3 2.5. Statistical Analysis. Data were analyzed using the Excel intubation, general anesthesia was maintained with 3% isoflurane (Fabius GS premium, Drager, Germany). program (Microsoft Corporation, Seattle, WA, USA) and RexSoft (2018, Rex: Excel-based statistical analysis software. During anesthesia, electrocardiography (ECG), oxygen saturation, and expiratory carbon dioxide concentration URL http://rexsoft.org/). $e tests for normal distribution were measured with a Vista 120 monitoring system (Drager, were performed using Shapiro-Wilk test for small sample Germany). $e animal was laid in the prone position and the sizes. $e means of data were compared with the paired limbs were fixed. Radiography was then performed using an sample t-test. When the p-value is less than 0.05, it is angiography machine (Artis Zee Multi-Purpose, Siemens, considered statistically significant. Germany). After animal experiments, animals were euthanized by 3. Results inducing cardiac arrest through intravenous infusion of large amounts of KCl through a catheter mounted in the vein $e basic concept of operation involving the new epidural of the ear under anesthesia (5% or more of isoflurane). space finder can be explained as follows. While the needle advances into the lumbar epidural space, a turning force is exerted on the dials ((1) in Figure 1) on both sides of the 2.4. Porcine Experiment. $e porcine experiment for epi- instruments to continue pushing the wire into the Tuohy dural space analysis was conducted in two piglets by a single needle ((2) in Figure 1). When the needle entered the anesthesiologist. A PLA model, printed with an FDM 3D epidural space, the resistance of the dials is released, and the printer, was sterilized with EO gas and used in the exper- guidewire moved forward smoothly. iment. $e interlaminar space between L1-2 and L4-5 was Different types of 3D printing materials are available, identified radiographically and marked at each level. $e such as acrylonitrile butadiene styrene (ABS), photopolymer guidewire and 14-gauge Tuohy needle, adapted from the resin, polylactic acid (PLA), polypropylene, high-density spinal cord stimulator trial kit (Medtronic inc, Minneapolis, polyethylene (HDPE), nylon, and polycarbonate (PC) [1]. MN, USA), were used. $e two methods including LOR and $e PLA and photopolymer resins were selected for the LOGR (epidural space finder printed with 3D printer) were production test due to their popularity in 3D printing. $e used randomly and sequentially to access the epidural space epidural space finder consists of two dials and one cage. Each via a paramedian approach at each level. A Touhy needle was printed part was assembled from two sterilized 35 mm M3 located and targeted under fluoroscopic guidance. Imme- bolts and nuts. $e two dials were tightened with a sterilized diately after penetrating the thick skin of the pig, the needle rubber band (Figures 1 and 2). $e epidural space finder trajectory from the skin to epidural space was estimated made of two materials was used for biocompatibility testing under fluoroscopic guidance. Immediately after skin pen- (sterility and extractable substance). etration, the needle was advanced 1 cm. A color change of the eluting solvent was observed in the When LOR technique was used to identify the epidural extractable substance test, which confirmed the plasticizer, space, as the needle was advanced through ligamentum lubricant, stabilizer, and pigment from the eluate in both flavum, a constant pressure was applied on the syringe until PLA and resin products. $e difference in pH between the loss of resistance occurred. $e plunger of the syringe was blank and the test solution was 0.07 in PLA and 0.58 in resin, gently withdrawn to assess the dural puncture. To confirm which is smaller than the test standard indicated in Korean the epidural space entry, the guidewire was advanced a few Pharmacopoeia (pH � 1.5) (Table 1). centimeters into the epidural space. $e difference in the consumption of potassium per- When LOGR (epidural space finder) was used, the manganate solution confirmed the presence of organic or guidewire replaced the air in the LOR technique. While inorganic substances. $e difference between the potassium advancing the needle through ligamentum flavum, adequate permanganate consumption of the blank and the sample force was exerted to ensure constant rotation of dials on both solutions was 0.128 mL in the PLA product but 5.75 mL in sides of the epidural space finder to generate resistance on resin (the test standard< 2 mL) (Table 1). the guidewire of the device. When the needle entered the In the ultraviolet absorption test used to identify the epidural space, the dial lost the resistance and the guidewire unknown substance with the ultraviolet light, the differences moved a few centimeters ahead smoothly into the epidural in absorbance between blank and sample solutions were space. After the procedure was completed, the epidural space 0.0002 AU for the PLA product and 3.927 in the resin finder and guidewire were removed, and a glass syringe was product (test standard< 0.1 AU) (Table 1). connected to a Touhy needle. $e plunger of the syringe was $e results of quantitative evaporation residue test gently withdrawn to determine the dural puncture. showed that 0.2 mg of PLA product and 12.9 mg of resin $e epidural space approach was confirmed by ad- product were eluted (the test standard of<1.0 mg) (Table 1). vancing the guidewire and radiographic image. $e time In order to determine if the heavy metals were eluted taken to advance the needle by 1 cm from the skin to the from the eluate, the color changes in the heavy metal re- epidural space was recorded. $e depth from the skin to action between the standard and the test solutions revealed epidural space was measured using the radiographic image. no differences in both PLA and resin product (Table 1). If more than three attempts were made to identify the $e medium performance test was performed to test the epidural space, it was marked as a failed attempt and the culture media. All the strains were appropriate for FTM and procedure was stopped to minimize the animal damage. TSB. $e color of the medium was changed, which R8.25 4 Journal of Healthcare Engineering (1) (2) (1) 29.5 Figure 1: $e basic concept of operation in the epidural space finder (up) and blueprint for epidural space finder (bottom) (dimensions in mm). (a) (b) (c) Figure 2: 3D printed epidural space finder (PLA product (left), resin product (middle), and assembled epidural space finder (right)). confirmed that all the strains were cultured when inoculated Based on the results of both experiments, the PLA into the selection medium. In this test, after 14 days of product was more biocompatible than the resin product. incubation, both FTM and TSB medium did not turn white We decided to use the porcine model to determine the and were deemed negative in PLA and resin product usefulness of the new LOGR compared with LOR technique (Table 2). to identify epidural space. In order to reduce false-positive R1.5 16.5 16.5 80 Journal of Healthcare Engineering 5 Table 1: Results of extractable substance test ( : test standard value created a new LOGR device (epidural space finder) to of Korean Pharmacopoeia [11]). identify epidural space. Our newly developed device is in direct contact with the PLA-FDM Resin-SLA epidural guidewire but not with the subject body. After Appearance (clear ) Clear Clear consulting with a biocompatibility specialist at KBIO Health, pH (<1.5) 0.07 0.58 we decided to perform extractable substance and sterility test Reducing substance (<2 mL) 0.1282 mL 5.75 mL but not the cytotoxic test. In the biocompatibility test, the UV absorbance (<0.1) 0.002 3.927 resin released a higher number of unknown organic or Residue on evaporation (<1.0 mg) 0.2 mg 12.9 mg Heavy metal (negative) Negative Negative inorganic substances than the PLA. Both materials were not certified biocompatible but were generally found in a regular 3D print store. PLA is a well-known biodegradable and biocompatible Table 2: Results of sterility test. polymer, which can be produced from the fermentation of PLA-FDM Resin-SLA corn or sugarcane. PLA is one of the most successful bio- polymers with a diverse range of biomedical applications, Fluid thioglycollate medium (FTM) No growth No growth Trypticase soy broth (TSB) No growth No growth such as drug delivery, implants, and tissue engineering [14]. Light-activated resin (photopolymer) contains a monomer and an oligomer cross-linked by light and pho- insertion into epidural space and to minimize animal sac- toinitiator, which generate free radicals that interact with the rifice, the needle trajectory into epidural space was estimated monomer to induce the polymerization chain reaction [15]. under fluoroscopic guidance immediately after penetrating Toxicity varies with the nature of the resin substance. For the skin with Touhy needle (Figure 3). example, bisphenol A-glycidyl-methacrylate (BisGMA) is In two pigs, 14 of 16 epidural insertion attempts were more cytotoxic and genotoxic than triethylene glycol successful via both methods (87.5% success rate). $ere was dimethacrylate (TEGDMA) monomers [16]. no significant difference between the number of attempts in It is not clear whether the substances released from the LOGR and LOR groups (1.38± 0.81 vs. 1.25± 0.68, resin products are harmful to humans, because no cytotoxic p � 0.317, N for each group � 14, paired sample sign test). A tests such as MTT (3-[4,5-dimethylthiazole-2-yl]-2,5- significant difference was observed in the average time taken diphenyltetrazolium bromide) assays were conducted. Even for epidural approach between LOGR and LOR groups though biocompatible resins are commercially available, it is (41.64± 32.18 vs. 92.28± 61.46 seconds, N for each certain that PLA is safer than the resin, at least in our group � 14, p � 0.0102 paired sample t-test). $e mean experiment. depth measured from skin to epidural space was not sig- In the porcine model, the LOGR technique was faster nificantly different between LORG and LOR groups than the LOR technique in facilitating access to the epidural (34.14± 7.9 vs. 36.25± 7.29 mm, N for each group � 14, space. However, no difference in success rate was observed. p � 0.1174, paired sample t-test) (Figures 3 and 4). When We could not completely evaluate the procedure related the dural puncture was tested by withdrawing the syringe complications such as dural puncture, because no radi- plunger at every attempt, no cerebrospinal fluid (CSF) reflux opaque contrast dye was injected after the epidural approach was observed. to minimize the porcine sacrifice. We evaluated the CSF reflux after each experiment; however, it is not a reliable method to confirm dural puncture. It is reasonable to 4. Discussion conclude that LOGR and LOR techniques are comparable in Different techniques are used to identify the location of their ability to provide access to the epidural space. However, epidural space during epidural anesthesia or catheter in- it was not clear which technique was associated with fewer sertion such as LOR, optical spectroscopy, ultrasound, and complications such as dural puncture or epidural hema- toma. Further studies are needed to establish the adverse optical coherence tomography [12]. LOR to air or saline technique is the most frequently used method in common effects associated with LOGR technique. Most of the 3D printing applications in anesthesiology to medical practice. Even though LOR technique is simple and easy to perform with a syringe without other complex date focus on rapid production, reduced manufacturing cost, and ability to provide a delicate printing design for anes- devices, it requires substantial training to perform cor- rectly and it is not reliable because of its high false-positive thesia planning or medical training. In addition, we sought to determine the potential of 3D printers in the manufacture rates of up to 30% [13]. In bedside epidural procedures, we frequently use epidural catheter insertion as an adjunct to of products anywhere in the world outside the factories. LOR technique to confirm the true epidural space. When $erefore, we tested PLA and resin, the materials used most loss of resistance is detected, and if epidural catheter often for 3D printing. Using these materials in a hospital, we cannot advance through the epidural needle, the tip of the can print our own devices with an inexpensive 3D printer. In summary, a 3D printer can be used to develop new needle may not be in the epidural space. For a long time, we sought to develop a device that combined the advan- medical devices for anesthesia and can also be used as an effective substitute when the normal supply chain collapses tages of LOR and catheter insertion. After designing several prototypes with 3D printing, we successfully such as in a war, earthquake, or typhoon. 6 Journal of Healthcare Engineering (a) (b) Figure 3: Lateral fluoroscopic image of epidural catheter insertion in porcine experiments: LOR technique (left) and LOGR technique (right). LOR LOGR LOR LOGR (a) (b) Figure 4: Boxplots comparing the duration of epidural approach (left) and the depth of epidural space (right) between LOR and LOGR techniques. Abbreviations Ethical Approval PLA: Polyactic acid Experiments were performed at KBIO Health Animal LOR: Loss of resistance Testing Center of the Medical Device Development Center LOGR: Loss of guide wire resistance (Osong Medical Innovation Foundation, Osong, Chungbuk, FDM: Fused deposition modeling South Korea) following approval of the Institutional Animal SLA: Stereolithography Care and Use Committee (KBIO-IACUC-2019-115). FTM: Fluid thioglycollate medium TSB: Tryptic soy broth Conflicts of Interest ABS: Acrylonitrile butadiene styrene (ABS) $e authors declare that they have no conflicts of interest. PLA: Polylactic acid HDPE: High-density polyethylene PC: Polycarbonate Authors’ Contributions CSF: Cerebrospinal fluid J. Yang contributed to study design, animal experiment, and BisGMA: Bisphenol A-glycidyl-methacrylate writing and confirming the first and final draft of the paper. TEGDMA: Triethylene glycol dimethacrylate. R. Choi contributed to 3D printing of the prototype. K. Cho contributed to data analysis. S. Kim contributed to data Data Availability analysis and graph drawing. B. Lee contributed to 3D $e data used in the study are available on request. printing and animal experiment. K. Lee contributed to Seconds Mm Journal of Healthcare Engineering 7 space,” Asian Journal of Anesthesiology, vol. 55, no. 2, communication with KBIO Health for biocompatibility test. pp. 30–34, 2017. D. Kim contributed to data collection and 3D modeling [13] A. H. White, R. Derby, and G. Wynne, “Epidural injections for software handling. J. Lee contributed to revision of the final the diagnosis and treatment of low-back pain,” Spine, vol. 5, draft of the paper. no. 1, pp. 78–86, 1980. [14] M. S. Singhvi, S. S. 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Published: Aug 24, 2020

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