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Summary

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

The identification of the epidural space, insertion of an epidural catheter and lumbar puncture are advanced technical skills that can be challenging to teach to novice anaesthetists. The M43B Lumbar puncture simulator-II (Limbs & Things Ltd., Sussex Street, Bristol, UK) is a teaching aid designed for epidural and spinal insertion. The aim of this study was to determine if experienced anaesthetists thought this simulator may be a useful tool for training novice anaesthetists in these procedures. Experienced anaesthetists performed an epidural insertion followed by a lumbar puncture procedure on the simulator model. Various aspects of both epidural and lumbar puncture insertions were scored by the anaesthetists for likeness to a real patient using a Likert scale (0 - strongly disagree; 1 - disagree; 2 - neither agree nor disagree; 3 - agree; 4 - strongly agree). The simulator was found to be life-like for most aspects of epidural insertion. Median (IQR [range]) scores were: iliac crests 3.0 (3.0–3.2 [3–4]); spinous processes 3.0 (3.0–3.2 [2–4]); skin puncture 3.0 (3.0–3.0 [1–4]); subcutaneous tissues 3.0 (2.7–3.0 [1–4]); and loss of resistance 3.0 (3.0–4.0 [3–4]). The scores for supraspinous ligament 2.0 (1.0–3.0 [0–3]), interspinous ligament 2.5 (1.7–3.0 [0–3]) and ligamentum flavum 2.0 (1.0–3.0 [0–4]) were borderline for life-likeness. The volunteers found threading of the epidural catheter difficult and rated it unlike a real patient (score 1.0 (0.2–2.0 [0–3])). During lumbar puncture, dural puncture scored 3.0 (3.0–4.0 [2–4]) and intrathecal injection scored 2.5 (1.0–3.0 [1–4]). However, the overall impression was that the simulator could be a useful tool for training of both epidurals (score 3.0 (3.0–4.0 [3–4])) and spinals (score 3.0 (3.0–3.5 [2–4])).

The technical skills of spinal and epidural needle insertion can be challenging to teach to novice anaesthetists, as successful needle placement relies on the feel of tissues, ligaments and loss of resistance, which can be difficult to describe [1]. Simulation before performing a neuraxial procedure on a patient may reduce the stress for a novice, as it provides hands-on training and may also reduce complication rates in patients [2–3]. Many trainee anaesthetists may insert their first epidural catheters on the labour ward, where the mother may be distressed and therefore not co-operative. The Royal College of Anaesthetists recognises that simulators can play a role in basic level obstetric anaesthesia training in the 2010 curriculum [4]. Several homemade models have been tried previously, in an attempt to simulate the feel of epidural and spinal insertion [5–7]. With recent advances in simulation technology, high-fidelity epidural simulators have become available; however, the cost effectiveness of these models (£6250–15 630/€7330–18 330/$10 000–25 000) has been questioned in a recent study [8].

The M43B Lumbar puncture simulator-II (Fig. 1) is marketed in the UK by Limbs & Things Ltd, Bristol, UK and is cheaper (£1670/€1960/$2670) than the high-fidelity model. It is produced by Kyoto Kagaku in partnership with Keio University Medical School, Tokyo, and allows for both epidural and spinal insertion [9]. It consists of a life-like lower torso with removable ‘skin’ over the lower back, that does not show the marks of previous needle punctures. A replaceable ‘puncture block’ (spinal or epidural) is inserted under the skin; it represents the second to fifth lumbar vertebrae, with associated structures and has a life span of thirty needle insertions per intervertebral space.

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Figure 1.  M43B Lumbar puncture simulator-II.

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We are not aware of any study that has evaluated this simulator for neuraxial procedures. The aim of this study was to determine whether experienced anaesthetists thought this simulator may be a useful tool for training novice anaesthetists to perform neuraxial procedures.

Methods

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Local research ethics committee approval was sought and deemed not necessary for this voluntary, manikin-based study. The simulator model was prepared as per manufacturer’s instructions (Fig. 2). Integral to the simulator is a replaceable ‘puncture block’ which is inserted into the torso and the ‘skin’ placed over it. The puncture block inserted can represent a ‘normal’, ‘obese’ or ‘elderly’ patient. For the purpose of this study, we used the ‘normal’ block as it was thought this would be most appropriate for teaching novice trainees. The simulator model was positioned in a sitting position and was supported by a second person. Participating anaesthetists were either consultant obstetric anaesthetists (n = 10), or registrars (n = 8) who had performed a minimum of 85 successful labour epidural insertions. A figure of a minimum of 85 epidural insertions was chosen as a previous study has shown that a novice attains proficiency between 1 and 85 attempts [10].

image

Figure 2.  M43B Lumbar puncture simulator-II (Internal view).

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Before insertion, the experience of the anaesthetist was noted and they were told that they were assessing the simulator model as a possible training tool. The participants were given an option of not to take part in this evaluation study. They were given a choice of using loss of resistance to either saline or air to reflect their usual practice and a standard 10.5-cm, 18-G Tuohy needle (Portex Ltd, Hythe, Kent) was used for epidural insertion. Lumbar puncture was performed using a Sprotte 25G pencil-point spinal needle (Pajunk UK Medical Products Ltd, Tyne & Wear), with the aid of a 20-G introducer needle. The participants selected the level of needle insertion after palpation of the iliac crest and spinous processes on the simulator model, and then performed an epidural insertion followed by a lumbar puncture.

Various aspects of both epidural and lumbar puncture insertions were scored by anaesthetists for likeness to a real patient using a five-point Likert scale (0 - strongly disagree; 1 - disagree; 2 - neither agree nor disagree; 3 - agree; 4 - strongly agree). The Likert scale is a psychometric scale commonly used in questionnaire research and has been used to compare high-fidelity manikins with low-fidelity manikins [11]. It is often used to measure respondents’ attitudes by asking the extent to which they agree or disagree with a particular question or statement. The concept of life-likeness has been used previously to compare manikins with real patients [12]. The volunteers were also asked if the simulator model was more life-like for lumbar puncture or epidural insertion; any other comments, were recorded as free text. Statistical analyses were performed using minitab 15.1 Statistical Software (Minitab Inc., State College, PA, USA).

Results

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Eighteen anaesthetists (10 consultants and 8 registrars) participated in this evaluation study. One of the volunteers attempted only epidural insertion and did not attempt a lumbar puncture due to a call to the labour ward during the study. The median (range) experience of volunteer anaesthetists was 16.5 (4–31) years and the median (range) number of epidural and spinal insertions was > 1000 (> 100 to > 2000). Sixteen anaesthetists used saline and two used air for loss of resistance during an epidural insertion. Results are shown in Table 1. The simulator was thought to be life-like for most aspects of epidural or spinal insertion with the exception of the ‘feel’ of the supraspinous ligament and ligamentum flavum, which were borderline for life-likeness.

Table 1.   Scores given by volunteer anaesthetists for life-likeness (0 - strongly disagree; 1 - disagree; 2 - neither agree nor disagree; 3 - agree; 4 - strongly agree).
 Epidural (n = 18)Spinal (n = 17)
Iliac crest3.0 (3.0–3.2 [3–4])3.0 (3.0–3.5 [3–4])
Spinous process3.0 (3.0–3.2 [2–4])3.0 (3.0–3.5 [2–4])
Skin puncture3.0 (3.0–3.0 [1–4])3.0 (3.0–3.0 [1–4])
Subcutaneous tissue3.0 (2.7–3.0 [1–4])3.0 (3.0–3.0 [2–4])
Supraspinous ligament2.0 (1.0–3.0 [0–3])2.0 (1.0–3.0 [0–3])
Interspinous ligament2.5 (1.7–3.0 [0–3])3.0 (1.5–3.0 [0–3])
Ligamentum flavum2.0 (1.0–3.0 [0–4])2.0 (1.0–3.0 [0–4])
Loss of resistance (epidural)3.0 (3.0–4.0 [3–4]) 
Epidural catheter insertion1.0 (0.2–2.0 [0–3]) 
Dural puncture (spinal) 3.0 (3.0–4.0 [2–4])
Intrathecal injection 2.5 (1.0–3.0 [1–4])
Overall impression3.0 (3.0–3.0 [2–4])3.0 (3.0–3.0 [2–4])
Useful for training3.0 (3.0–4.0 [3–4])3.0 (3.0–3.5 [2–4])
Useful for assessment3.0 (3.0–3.0 [1–4])3.0 (3.0–3.0 [1–4])

One volunteer had an accidental dural puncture during epidural insertion. This was felt to be a realistic representation of accidental dural puncture by the volunteer. Ten anaesthetists felt that the simulator model was more life-like for a lumbar puncture, four felt it was more life-like for epidural insertion and three felt it was equally life-like for both epidural insertion and lumbar puncture.

Discussion

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

This study demonstrates that experienced anaesthetists found the simulator to be life-like for most aspects of epidural or spinal insertion. The ‘feel’ of the supraspinous ligament and ligamentum flavum was felt to be borderline for life-likeness and threading of the epidural catheter was noted to be difficult. However, the overall impression was that the simulator could provide a useful tool for training of epidural and spinal techniques.

Positive free text comments offered about the simulator model included that the skin puncture was very good, with no obvious marks from previous punctures, the ‘loss of resistance’ sensation on entering the epidural space was very life-like and many found it more useful than they had anticipated. Some volunteers remarked that the simulator model represented the easiest possible epidural or spinal insertion, as the spinous processes were easily palpable, and that the model represented a slim patient. This was due to the fact that the puncture block evaluated was the one designed to reflect a slim patient (Fig. 2); the puncture block can be changed to represent an obese or an elderly patient if required, but these were not evaluated. Each puncture block costs £96/€112/$153 and the manufacturer recommends a maximum of thirty needle insertions for each intervertebral space. After continued use the feel of tissues, ligaments and ‘loss of resistance’ became less discriminatory. This may help to explain the accidental dural puncture that occurred towards the end of the life of the puncture block.

One of the most difficult aspects of epidural insertion to teach to a novice anaesthetist is the concept of ‘loss of resistance’. Although most anaesthetists thought the ‘loss of resistance’ was life-like, it was disappointing that the feel of the ligamentum flavum scored poorly. It was noted that the ligamentum flavum felt less ‘dense and gritty’ than expected and was less thick. It was thought that a verbal description of the ligamentum flavum would have to be given to trainees, as this was a poor aspect of the simulator training.

There are potential benefits in using the simulator for teaching beyond neuraxial needle insertion. It may be used to teach patient positioning as the model may be placed in the lateral and sitting position, skin preparation can be discussed and palpation of pelvic landmarks and spinous processes can be practised. It may act as a prompt to discuss other aspects of neuraxial block, including contraindications and complications.

We did not account for deterioration in the puncture block during the course of the study. Therefore, volunteers who performed procedures when the puncture block was new may have scored it higher than those who performed the procedure towards the end of its life. However, we obtained a realistic view of the puncture block over its life-span.

We conclude that this simulator is a promising tool for training of neuraxial procedures, that could be used as part of basic level of training for neuraxial procedures within the Royal College of Anaesthetists curriculum. The clinical impact of the simulator with respect to training and patient outcomes requires further evaluation.

Acknowledgements

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

We thank the West of Scotland Committee for Postgraduate Medical Education in Anaesthesia for funding the purchase of the M43B Lumbar puncture simulator-II and obstetric anaesthesia consultants and trainees at Princess Royal Maternity for their co-operation. No competing interests declared.

References

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References