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Comparison of sitting and prone positions for real-time ultrasound-guided thoracic epidural catheter placement: a randomized controlled trial
  1. Sojin Shin1,
  2. Jong-Hyuk Lee2,
  3. Hyun-Jung Kwon2,
  4. Ingon Lee2,
  5. Dongseok Kim3,
  6. Hakmoo Cho3,
  7. Doo-Hwan Kim2 and
  8. Sung-Moon Jeong2
  1. 1Department of Anesthesiology and Pain Medicine, Uijeongbu Eulji University Hospital, Uijeongbu, South Korea
  2. 2Department of Anesthesiology and Pain Medicine, Asan Medical Center, Seoul, South Korea
  3. 3Department of Anesthesiology and Pain Medicine, Veterans Health Service Medical Center, Seoul, South Korea
  1. Correspondence to Professor Doo-Hwan Kim, Department of Anesthesiology and Pain Medicine, Asan Medical Center, Songpa-gu, Seoul, Korea (the Republic of); dh_kim{at}amc.seoul.kr

Abstract

Introduction Real-time ultrasound-guided thoracic epidural catheter placement (US-TECP) has been recently introduced. Patient’s position is associated with the success of spine interventions; however, the effects of position on the outcome of the procedure remain unknown. We aimed to assess the clinical usefulness of patient positioning during real-time US-TECP.

Methods Patients were randomly assigned to the prone position group (group P) and sitting position group (group S). The primary outcome was needling time during the procedure. The secondary outcomes were time to mark space, total number of needle passes, number of skin punctures, first-pass success, final success, crossover success, and visibility of ultrasound (US) views. Global Rating Scale (GRS) score, Patient Comfort Scale score, procedural pain intensity, patient satisfaction, and procedure-related complications were also determined.

Results Sixty-four patients were included in this study. The needling time was significantly shorter in group P than in group S (36.5 (26.5–51.0) vs 59.5 (34.5–152.0) s, p<0.01). The numbers of needle passes and skin punctures were significantly lesser in group P than in group S. First-pass success was higher in group P than in group S. Group P had higher GRS compared with group S. The time to mark space, final success, US visibility score, Patient Comfort Scale score, procedural pain intensity, and patient satisfaction did not differ between the groups. One patient in group S developed a vasovagal reaction.

Discussion This study shows that prone position may be preferred for real-time US-TECP, considering its better clinical usefulness.

Trial registration number KCT0005757.

  • Pain Management
  • Ultrasonography
  • Pain, Postoperative
  • Acute Pain

Data availability statement

Data are available upon reasonable request.

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What is already known on this topic

  • Real-time ultrasound-guided thoracic epidural catheter placement (US-TECP) has been recently introduced. The patient’s position is associated with the successful spine intervention, but the effects of position on the outcome of real-time US-TECP remain unknown.

What this study adds

  • The performance of real-time US-TECP in the prone position results in shorter needling time, lesser number of needle passes and skin puncture, higher first-pass success rate, and higher overall performance score than those in the sitting position. However, the visibility of ultrasound views, Patient Comfort Scale score, procedural pain intensity, and patient satisfaction were not different between the two positions.

How this study might affect research, practice or policy

  • The prone position may be preferred for real-time US-TECP, considering its better clinical usefulness.

Introduction

Thoracic epidural analgesia is recommended for managing acute postoperative pain during esophageal, open thoracic, and abdominal surgery under enhanced recovery after surgery guidelines.1 2 This procedure provides several perioperative advantages, such as alleviation of acute postoperative pain, reduction of perioperative cardiac stress, and improvement of postoperative pulmonary function.3 However, thoracic epidural access (TEA) remains technically challenging, and thoracic epidural catheter placement (TECP) is associated with a high failure rate of up to 40%.4 5

Recently, ultrasound-guided thoracic epidural catheter placement (US-TECP) is an alternative to the landmark palpation-based TECP6; real-time US-TECP showed complete success rate and good performance in the clinical setting, including fewer needle passes and skin punctures.7 8

According to previous studies on US-TECP, patients were placed in the sitting position during the procedure.7 8 However, based on our experience, it can sometimes be difficult to maintain the proper position of the ultrasound (US) probe when the patient is seated, whereas prone position can be helpful in stabilizing the operator’s hand while holding the probe, and the possibility of patient movement can be reduced.9 Therefore, we hypothesized that the prone position would both reduce procedural time and increase success rate when compared with the sitting position during US-TECP.

Methods

Study design and participants

This prospective, randomized, comparative study was conducted at Asan Medical Center in Seoul. This study was prospectively registered at the Clinical Research Information Service (https://cris.nih.go.kr/cris/search/detailSearch.do/20555) on December 21, 2020. All patients were enrolled from March 2, 2021, to September 28, 2021. Patients who required thoracic epidural analgesia were assessed for eligibility in this study. Among them, patients who met the following criteria were included: (1) those scheduled to undergo open upper abdominal surgery or thoracic surgery for TECP at the T6–12 level, (2) adult patients (20–79 years) with an American Society of Anesthesiologists physical status of ≤III, and (3) those who voluntarily consented to participate in this study. By contrast, patients who had allergies to local anesthesia and contrast dye or steroids; had coagulopathy or infection or used anticoagulants or antiplatelet medications, had neurological or psychiatric disorders, were pregnant, had scoliosis, or underwent spine instrumentation or experienced compression fracture near the insertion site were excluded.

Randomization

Web-based randomization software (Random Allocation Software V.1.0; Isfahan University of Medical Sciences, Isfahan, Iran) was used to randomly allocate patients to the two study groups. Randomization was carried out using block sizes of 4 and an allocation ratio of 1:1. When performing thoracic epidural catheterization, the patients were asked to assume either a prone position (group P) or a sitting position (group S) according to a computer-generated randomization schedule. Randomization codes kept in sequentially numbered opaque envelopes, concealed by the first investigator, were provided to the operators. All procedures were conducted by two pain physicians who were not blinded to the patient’s position.

Real-time US-TECP

All patients were monitored using non-invasive blood pressure measurement device, pulse oximetry, and three-lead ECG. In group P, the patients were placed in prone position, and a pillow was placed under the chest and upper abdomen to widen the thoracic interlaminar space. In group S, the patients were placed in a sitting position. Then, they hugged a pillow and flexed their back to widen the thoracic interlaminar space. The method to optimize US views was followed by the protocol of real-time US-TECP in previous our study.8 A 12-MHz high-frequency linear US probe (12 MHz; NextGen LOGIQ e, GE Healthcare, Madison, Wisconsin, USA) was used. After obtaining the paramedian sagittal oblique view by laterally tilting the probe (figure 1A,B), the ligamentum flavum, posterior dura (hyperechoic), intrathecal space (anechoic), and anterior complex (hyperechoic), respectively, could be seen in this view (figure 1C). The posterior complex including the ligamentum flavum and posterior dura could be seen as linear hyperechoic structures between the laminae (figure 1D). Once the target interlaminar space was identified, the skin overlying the center of the interlaminar space, the midline of the thoracic spine, and both cephalad and caudal ends of the probe were marked. Then, aseptic disinfection and draping were performed. After obtaining the best US view and determining the needle entry site, local infiltration with 1% lidocaine was conducted. An 18-gage Tuohy needle (Perifix; B Braun Melsungen AG, Melsungen, Germany) was inserted from the caudal end of the probe and was advanced in-plane view under real-time US guidance until the needle tip reached in front of the ligament flavum or posterior complex on the interlaminar space (online supplemental Video 1). Then, the needle was further advanced until the epidural space was accessed using the loss-of-resistance (LOR) technique to normal saline without US guidance; one operator conducted the procedure independently. After TEA, the epidural catheter was advanced through the needle such that 4 cm of the catheter remained in the epidural space. Finally, 4 mL of 1% lidocaine was administered via the epidural catheter under real-time US monitoring. After 10 min, the dermatomal levels were assessed by performing a cold test. The procedure was carried out by two pain physicians with more than 3 years of experience in performing US-TECP following identical protocols. To reduce bias, all physicians performed the procedure, using both positions, 3 months prior to the initiation of the study.

Figure 1

Location of the US probe for paramedian sagittal oblique view and representative paramedian sagittal oblique views observed during real-time US-guided thoracic epidural catheter placement. (A) Illustration to demonstrate the probe location on the thoracic spine. (B) Location of the US probe for paramedian sagittal oblique view in a volunteer model. On US scans, (C) L, LF, PD, and AC are clearly visualized; (D) PC including ligamentum flavum and PD are shown as linear hyperechoic structures between the L; (E) L, interlaminar space, and PC are identifiable; and (F) L and interlaminar spaces are only seen. AC, anterior complex; L, lamina; LF, ligamentum flavum; PC, posterior complex; PD, posterior dura; US, ultrasound.

Outcome assessments

The primary outcome was needling time for epidural needle to reach the epidural space after skin puncture. The secondary outcomes were as follows: (1) time to mark space: time to determine the best US view and skin puncture site and to mark the skin; (2) total number of needle passes: first needle pass+additional needle passes (if the epidural needle hits the laminae or spinous process, it should be moved backward and readvanced with a changing direction; it is considered as the additional needles pass); (3) number of skin punctures: complete needle withdrawal from the skin and reinsertion of the needle at a new location; (4) first-pass success: the epidural space was reached after a skin puncture without backward movement of the epidural needle; (5) final success: achievement of successful TEA by LOR and confirmation of a positive cold test result within the maximal nine needle passes in the allocated trial; (6) cross-over success: in case the allocated method failed, achievement of successful TEA in another method with one skin insertion and a total of three needle passes; (7) US visibility score10 (0=not visible, 1=poorly visible, and 2=well visible; total score=8): measurement of visibility of the four target structures (lamina, interlaminar space, posterior complex, and anterior complex) on US examination in order to obtain the best US view prior to needle insertion (eg, figure 1C,D, garnered a total score of 8 points; figure 1E, 6 points; and Figure 1F, 3 points); (8) global rating scale (GRS score, total score: 15): the GRS consisted of seven items, each rated on a 5-point rating scale.11 The GRS predominantly assessed more general behaviors and the overall performance of the participants. The seven items included preparation for the procedure, respect for tissue, time and motion, instrument handling, flow of procedure, knowledge of procedure, and overall performance. Among of them, three items (time (from time to US scanning to epidural catheter insertion) and motion, instrument handling, and flow of operation) were used to quantitatively measure the overall performance of real-time US-TECP; (9) Patient Comfort Scale: used to assess the comfort level of the patient according to the position during the procedure (grade 0=help, 2=uncomfortable, 4=mild discomfort, 6=feeling OK, 8=pretty comfortable, and 10=feeling great)12; (10) procedural pain intensity during the procedure: assessment of pain intensity using a single 11-point Numerical Rating Scale, with scores ranging from 0 (no pain) to 10 (worst pain imaginable); (11) patient’s level of satisfaction: assessment performed after the procedure based on the global perceived effects (GPES) using a 7-point scale with some modifications (grade 1=very dissatisfied, 2=somewhat dissatisfied, 3=slightly dissatisfied, 4=neither satisfied nor dissatisfied, 5=slightly satisfied, 6=somewhat satisfied, and 7=very satisfied)13; and (12) procedure-related complications: epidural hematoma, dural penetration, intravascular or intrathecal local anesthetic injection, and pneumothorax.

The second investigator, who was not blinded to the allocation groups, evaluated the procedure-related outcomes in the operating room. The third investigator, who was blinded to the allocation groups, assessed the subjective outcomes such as Patient Comfort Scale score, procedural pain intensity, and patient satisfaction in the postanesthetic care unit.

Statistical analysis

The primary endpoint of this study was needling time. In our previous study, the average needling time during epidural catheter insertion performed in prone position was 62.4 s, with an SD of 25 s.8 The needling time in the sitting position was assumed to be 81.1 s, and a 30% difference was observed between the two groups. Considering an alpha level of 0.05, a power of 80%, and an allocation ratio of 1:1, we found that the required number of participants was 30 in each group. Considering a dropout rate of 5%, a total of 64 patients were included.

Continuous variables were analyzed using independent sample t-tests for normally distributed data or Mann-Whitney U tests for non-normally distributed data. Categorical variables were analyzed using χ2 tests with continuity correction or Fisher’s exact tests. The data are expressed as mean±SD, median (IQR) or number (proportion), as appropriate. Statistical analyses were performed using R software V.3.5 (R foundation for statistical computing, Vienna, Austria) and SPSS V.21.0 software.

Results

Sixty-five patients were eligible, of whom one refused to be enrolled and 64 patients participated in this study (figure 2). No significant differences were observed in the clinical characteristics between the two groups (table 1).

Table 1

Participants’ clinical characteristics

Figure 2

Consolidated Standards of Reporting Trials flow diagram of the present study.

The measurement outcomes during the real-time US-TECP are shown in table 2. The needling time were significantly lower in group P than in group S (36.5 (26.5–51.0) vs 59.5 (34.5–152.0) s, p<0.01). The time to mark space did not differ between the two groups (54.0 (39.5–60.0) vs 58.0 (51.0–68.0) s, p=0.05). The number of needle passes was significantly less in group P than in group S (1.0 (1.0–2.0) vs 2.0 (1.0–3.5), p<0.01). First-pass success was significantly higher in group P compared with that in group S (71.9 vs 40.6%, p=0.02). Final success was not significantly different between the two groups (100 vs 96.9%, p<0.99). Cross-over success occurred in group S; in one patient, the procedure was not successfully performed in a sitting position. Hence, the patient was repositioned to prone; the procedure was repeated; and success was achieved. The procedure in group P resulted in significantly fewer skin puncture than those in group S (1: 100 vs 75%, 2: 2 vs 15.6%, 3≥: 0 vs 9.4%; p=0.01). The mean skin to epidural distance was not significantly different between the two groups (5.7±0.7 cm for group P vs 5.6±0.6 cm for group S, p=0.59). No procedure-related complications occurred in group P; however, one patient in group S developed a vasovagal reaction (mild nausea, sweating, hypotension, and bradycardia) but eventually recovered without sequelae.

Table 2

Procedural outcomes during real-time ultrasound-guided thoracic epidural catheter placement

The median US visibility total scores in group P and group S were not significantly different: 6.0 (5.0–8.0) and 6.0 (4.5–8.0), respectively (p=0.97). The US visibility according to thoracic spine level did not differ between the groups (online supplemental table 1). The total GRS score was significantly higher in group P than that in group S (15 (13.0–15.0) vs 12 (10.0–13.0), p<0.01; online supplemental figure 1). The GRS scores on times and motion, instrument handling, and flow of operation were also significantly higher in group P than those in group S (5 (4.0–5.0) vs 4 (3.0–5.0), p<0.01; 5 (5.0–5.0) vs 4 (3.0–4.0), p<0.001; 5 (4.5–5.0) vs 4 (3.0–5.0), p<0.001).

Supplemental material

Supplemental material

Postoperative measures are shown in table 3. The Patient Comfort Scale score, procedural pain intensity, and patient satisfaction were not different in group P than in group S (Patient Comfort Scale score: 9.0 (8.0–10.0) vs 8.0 (8.0–10.0), p=0.29; Numerical Rating Scale score: 1.8±1.1 vs . 2.3±1.3, p=0.06; GPES: 7.0 (6.0–7.0) vs 6.0 (6.0–7.0), p=0.14).

Table 3

Postoperative measures: Patient Comfort Scale score, procedural pain intensity, and patient satisfaction

Discussion

To our knowledge, this study is the first to evaluate the clinical usefulness of patient position during real-time US-TECP. This study demonstrated successful performance of real-time US-TECP in the prone position with shorter needling time, lesser number of needle passes and skin puncture, higher first-pass success rate, and higher overall performance score than those in the sitting position. However, the visibility of US views, Patient Comfort Scale score, procedural pain intensity, and patient satisfaction were not different between the two positions.

The patient’s positioning can be one of the contributing factors to successful spine interventions.14 A sitting position or lateral decubitus position is preferable for a lumbar epidural procedure, especially epidural analgesia during labor because a flexed back and reduced lumbar lordosis by either positions can widen the interlaminar space.15 16 Despite the significance of positioning in the epidural procedure, studies on the clinical usefulness of different positions are limited,17 especially during US-guided epidural catheter placement in the lumbar and thoracic regions.

When TECP or US-TECP is performed, the patients are generally placed in a sitting position.6 7 15 18 However, our previous study demonstrated that real-time US-TECP could be successfully performed in a prone position.8 This may be explained by the anatomical features of the thoracic vertebrae, which can be flexed within 26°, as the positioning of the ribs and spinous processes greatly limits movement.19–21 These unique anatomical features in the thoracic region may limit the widening of the interlaminar space during thoracic flexion when in a sitting position.9 18 Additionally, the prone position with a pillow under the chest and upper abdomen seems to be effective for widening the target interlaminar space, as fluoroscopic-guided thoracic interlaminar interventions with a nearly complete success rate are frequently conducted in a prone position.22 23 It can be also indirectly supported by the fact that similar US views were obtained in this study during the performance of real-time US-TECP regardless of the position, although only a dearth of evidence was provided.

Furthermore, the prone position may have several practical benefits compared with the sitting position when real-time US-TECP is performed. First, prone position is advantageous for stabilizing and manipulating the US probe.9 It is important for the operator’s hand to hold the probe firmly against the patient’s back and to apply slight pressure downward to minimize probe movement24; these advantages can be achieved by the prone position comfortably, whereas, in the sitting position, it can be relatively difficult to fix the US probe because of being pulled down the cable of the US probe by gravity and being slid the US probe frequently in our experience. Second, the possibility of patient movement during needle manipulation can be reduced in a prone position compared with a sitting position, which can disrupt needle tracking and acquisition of proper US views.9 25 This is supported by the higher reported performance scores in the results. Third, the procedure in prone position can be performed independently, without the need for assistance in supporting the patient.

The difference of 30 s in needling time may not be significant in clinical practice. However, the needling time can be much longer, especially in case of trainees and novices. We believe that the prone position can be more advantageous in reducing the needling time for beginners, who are not experienced in real-time US-TECP. In addition, short needling time can reduce patient discomfort and anxiety related to the procedure.26

The Patient Comfort Scale score, procedural pain intensity, and patient satisfaction were not affected by position. If the patient has severe shoulder discomfort or ascites or is pregnant, the sitting position may be more advantageous; if the patient requires sedation, the prone position may be more advantageous because the risk of falling down is high in the sitting position.17 Therefore, an appropriate position should be selected according to the characteristics of the patient, although prone position may be more clinically useful to those physicians who conduct real-time US-TECP.

Interestingly, according to a recent study of US-assisted TECP, US-assisted thoracic epidural approach provided no significant difference in the number of needle redirections compared with the standard landmarking technique.27 Although the study showed negative outcomes of using the US assistance when performing the TECP, paradoxically, it can verify the importance of real-time US guidance during the TECP. To improve the overall clinical usefulness, determination of the proper needle insertion point is important; however, an adequate trajectory angle (sagittal or axial) of the needle is more crucial; it can be achieved only under real-time US guidance, not offline technique using the US assistance. Nevertheless, several further studies are warranted to verify the clinical benefit of real-time US-TECP.

This study has some limitations. First, although this was a prospective randomized controlled study, the small number of participants limited the generalizability of our study. Second, it was impossible to blind the physicians to the allocated intervention and the second investigators to the procedural outcomes measures; this may have introduced bias into the study results. Third, only a select group of investigators performed the investigating procedure, thereby limiting generalizability. Therefore, external validation is necessary. Fourth, the prone position may provide several advantages to the physicians; however, the clinical benefits for the patients may be limited because final success and patients’ subjective outcomes were not different between the two positions. Fifth, the body mass index of the patients in this study is relatively low. Therefore, an evaluation of the clinical usefulness of the real-time US-TECP in the prone position with obese patients is warranted. Further studies are needed to confirm the success of the prone position in other interventional techniques.

Conclusion

Considering the shorter needling time, lesser number of needle passes and skin puncture, higher first-pass success rate, and higher overall performance score compared with those of the sitting position, the prone position may be recommended for real-time US-TECP. However, the position did not affect the patient’s subjective outcomes and final success rate; hence, it is important to determine the appropriate position depending on the patient’s condition when performing real-time US-TECP.

Data availability statement

Data are available upon reasonable request.

Ethics statements

Patient consent for publication

Ethics approval

This study was approved by the institutional review board of the Asan Medical Center (IRB number 2020-1865, approval date: December 19, 2020) and was registered at Clinical Research Information Service (https://cris.nih.go.kr/cris/search/detailSearch.do/20555), and written informed consent was obtained from all participants.

References

Supplementary materials

Footnotes

  • SS and J-HL are joint first authors.

  • Correction notice This article has been corrected since it published Online First. The first authorship statement has been added.

  • Contributors SJS: conception, design, and conduct of the study; analysis and interpretation of data; reporting; and writing—original draft preparation. J-HL: conception, design, and conduct of the study; interpretation of data; writing—review, and editing of the manuscript. H-JK and IGL: data curation and acquisition. DHK, HMC, and S-MJ: planning, conception, and design of the study; supervision; and project administration. D-HK: planning, conception, design, and conduct of the study; writing—review, and editing of the manuscript; supervision; and project administration. All authors critically revised the manuscript. All authors approved the final version of the manuscript. D-HK (guarantor) accepts full responsibility for the finished work and/or the conduct of the study.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.