Rowan Thomas

St. Vincent’s Hospital Melbourne, Australia

Teaching anaesthetic trainees a new technology in theatre can be a very challenging task, especially when the teacher is also becoming familiar with the new technology (1). The use of ultrasound to perform nerve blocks can be used as an example of an important new use of a technology that requires time and expertise to teach effectively during a busy surgical list. Teaching ultrasound can be used to examine some elements of teaching that can be applied to other new clinical techniques.

The advantages of ultrasound for regional anaesthesia (2,3) are:

1. It allows visualisation of neural structures
2. It allows visualisation of variations in anatomy
3. It minimises dose of local anaesthetic
4. It is a potentially faster onset of block
5. It is a potentially better quality of block
6. Intra-neural injection can be seen.

The disadvantages of ultrasound are:

1. It may add too much technology when first learning a nerve block
2. It is not available in every hospital
3. It may subject nerves to higher concentrations of local anaesthetic
4. Multiple needle passes in the hands of a novice may damage the nerve
5. It adds set up time

A current research project at St. Vincent’s Hospital is the SARA (Sonography and Regional Anaesthesia) trial. We are comparing the quality and performance of axillary blocks of trainees, randomised to two groups: (UNS) ultrasound and nerve stimulator or (NS) nerve stimulator alone. The registrars have not learnt axillary block and use a standardised dose of local anaesthetic. The assessor of the block is blinded. The block supervisors teach in a uniform manner and are equally enthusiastic about ultrasound and nerve stimulator techniques.
The SARA teaching course includes:

1. Written summary of block and technology
2. Directed further study - Online resources, Journal articles and anatomical diagrams
3. Observation and discussion
4. A Multiple choice exam
5. “Pre-scanning practice”
6. Experience with a “phantom”
7. Performance of one block with “active” coaching
8. 15 blocks, assessed with supportive instruction and reflective coaching.

Assessment of the performance of the block is done using a Global Rating Score (4) and rates on a five point scale:

1. Ergonomics
2. Machine settings/Image optimisation
3. Sterile technique
4. Survey scan/Anatomy
5. Needle/Probe manipulation
6. Respect for safety
7. Use of nerve stimulator
8. Time and motion
9. Use of assistants Knowledge of procedure
10. Overall performance
11. The number of needle passes and number of skin punctures.

Assessment of the block is by a blinded observer who grades sensory and motor loss in each nerve distribution to produce a composite score of block success.

Previous research about learning ultrasound techniques in a simulated environment has demonstrated a “hand-eye” learning curve (5) that is maximal between the second and third attempts and also noted a concerning observation that many novices (7 out of 10) advanced the needle without good visualisation.

Common errors when using ultrasound (6) are:

1. Failure to recognise maldistribution of local anaesthetic
2. Failure to recognise an intramuscular location of the needle tip before injection
3. Fatigue
4. Failure to correctly identify the sidedness of the patient with the orientation of the ultrasound probe
5. Poor choice of needle insertion site and angle for optimal visualisation

Educational techniques and milestones to be considered when teaching are:

1. Understanding the ultrasound machine
2. Skills development using a simulation tool eg Phantom
3. Scanning without needling
4. Learning the anatomy
5. Didactic instruction
6. Self directed research and study
7. Review of common errors
8. Doing blocks with direction
9. Doing blocks with narration
10. Review and reflection using the GRS and block assessment tools to initiate discussion.

References:
1. Marhofer P, Chan VW. Ultrasound-guided regional anesthesia: current concepts and future trends. Anesth Analg 2007;104:1265-9
2. Soeding PE, Sha S, Royse CE, Marks P, Hoy G, Royse AG. A randomized trial of ultrasound-guided brachial plexus anaesthesia in upper limb surgery. Anaesth Intensive Care 2005;33:719-25.
3. Chan VW, Perlas A, McCartney CJ, Brull R, Xu D, Abbas S. Ultrasound guidance improves success rate of axillary brachial plexus block: Can J Anaesth 2007;54:176-82.
4. Naik VN, Perlas A, Chandra DB, Chung DY, Chan VW. An assessment tool for brachial plexus regional anesthesia performance: establishing construct validity and reliability. Reg Anesth Pain Med 2007;32:41-5.
5. Sites BD, Gallagher JD, Cravero J, Lundberg J, Blike G. The learning curve associated with a simulated ultrasound-guided interventional task by inexperienced anesthesia residents. Reg Anesth Pain Med 2004;29:544-8.
6. Sites BD, Spence BC, Gallagher JD, Wiley CW, Bertrand ML, Blike GT. Characterizing novice behavior associated with learning ultrasound-guided peripheral regional anesthesia. Reg Anesth Pain Med 2007;32:107-15.