Exploring Performance of, and Attitudes to, Stop- and Mock- Before- You- Block in Preventing Wrong Side Blocks

Hopping M, Merry AF and Pandit JJ

Anaesthesia 2018, 73, 421- 427

Aim of Study

To identify percentage of anaesthetists that use the Stop-before-you-block or Mock-before-you-block methods and explore their attitudes towards it.

Design and Location

Online survey to all anaesthetists at 9 hospitals across the Midlands.


Email sent to all anaesthetists in 9 hospitals across the Midlands, containing an online questionnaire with 16 questions.

Primary Outcome

Assess practice of Stop-before-you-block for regional anaesthetic blocks, as well as incidence of wrong side blocks during the anaesthetist’s career.

Secondary Outcomes

Assess attitudes towards Stop-before-you-block practice.

Extrapolate data to current incidence of wrong side blocks per year

Assess anaesthetic experience at the time of performing a wrong side block


Minimum sample size of 150 (at least 200), to estimate appropriate Poisson confidence intervals for low or zero response rates to estimates of occurrence of wrong side blocks.


Seniority: 83% of respondents were consultants/ SAS doctors

Number of wrong side blocks reported: 62, by 51 respondents.

Predisposing factors: distraction, positioning, miscommunication.

41% (62) of respondents stop too early before block.

86% of respondents are aware of current Stop-before-you-block guidelines


  • 1 in 4 anaesthetists have performed a wrong sided block
  • There is a reluctance to do a Stop-before-you-block immediately before needle insertion as this causes a disruption, and 41% of respondents ‘stop’ too early.
  • There is an awareness of Mock-before-you-block but it isn’t a popular method.
  • Two centres introduced a ‘stop sticker’, but this resulted in two occasions in a wrong sided block as it was placed in the wrong limb.

Stated Limitations from the Study

  • Estimated number of wrong side blocks per year calculated as 156.

However, the number reported (never events) was 45. Respondents may be over reporting.

  • Although Stop-before-you-block was introduced in 2015, and a reduction in number of wrong side blocks hasn’t seemed to happen, wrong side blocks became a ‘never event’ in 2015. This may produce a higher number of wrong side blocks reported from 2015 onwards.
  • The sample size is only 40% of the total number of anaesthetists in the region.

Discussion from Journal Club Meeting (? Change of Practice)

Stop-before-you-block has already been introduced in our department. Some of us may be stopping too early.

This may be assessed by doing an audit of our current practice in the future.

Summary by Dr M Rojo. Journal Club Meeting 5 July 2018.

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