Stop Before You Block

Resources (you may download the full educational package here):

Full SOP (includes FAQs)

Stop Before You Block - Training Video 2021

Stop Before You Block - Silent Training Video 2021



In 2018 the newly created Healthcare Safety Investigation Branch (HSIB) investigated the causes of wrong side regional anaesthetic block and invited the Safe Anaesthesia Liaison Group (SALG) to formulate a standard, national policy [1]. A specific ask was to review the status of ‘Stop Before You Block’ (SBYB) to assess if any improvements could be made.

The resulting working party had representation from RA-UK, the Faculty of Pain Medicine, the RCoA Simulation Working Group and NHS Improvement.

Evidence was gathered via a survey of RA-UK members, formal 3-month trials of the new process across a number of UK sites (both self-reported and observational) and data from a series of 20,000 blocks at South Tyneside and Sunderland NHS Foundation Trust.

The deconstruction of the SBYB process into three explicit steps: Preparation, a Stop moment followed immediately by performance of the Block (Prep, Stop, Block) is the result of discussions begun in the SALG working party and finalised by the SOP’s authors.

Further background to the project and the methods employed is included in this editorial published in Anaesthesia.

What was the problem with the original SBYB process?

Devised by the Nottingham group in 2010, the original SBYB campaign seemed a successful innovation [2]. With a catchy title, it became widely established across the UK and internationally (endorsed by Australian and New Zealand colleges (ANZCA) and widely adopted in the US). Unfortunately, the incidence of wrong side blocks (WSB) remained doggedly at around 1 in 6250 over the years [3].

One problem was that while the original poster stated that the STOP moment should take place immediately before needle insertion and that the site should be reconciled with the surgical site mark, later research indicated that this was widely misinterpreted. The recommendation that both anaesthetist and assistant should check together was overlooked, and the ‘stop’ moment was too often performed at the WHO ‘sign in’ to the anaesthetic room which was up to 30-45 minutes before block placement.

The original guidance encouraged local variation in how SBYB was interpreted. Thus, some Trusts came to use warning stickers (which may become displaced); some to mark the limb to be blocked, others as a warning not to block that side [4,5]. These local variations can be particularly confusing for rotating clinicians (trainees and locums), and also make difficult mapping an adverse event against a consistent framework [6].

How does the new approach differ?

The new approach is presented as a ‘standard operating policy’ (SOP) to be applied nationally. While the SBYB ‘brand’ is retained, the process of performing a block is deconstructed into three discrete steps: Prep, Stop, Block. Any future wrong-side peripheral nerve blocks (WSBs) can be investigated and mapped against a common framework.

Step 1: ‘Prep; Preparation

The WHO ‘Sign In’ is performed on arrival of the patient in the anaesthesia room. General anaesthesia may or may not be administered first (or not at all). Regardless, the Blocker (the person who performs the block, who may commonly be an anaesthetist) prepares the local anaesthetic solution and places the labelled syringe with a suitable nerve block needle in a dedicated tray/container, which is handed over to the Assistant, out of the Blocker’s immediate reach. The Blocker and Assistant should position the patient and equipment in the final position ready for the block and may perform a preliminary ‘pre-scan’ with ultrasound. The Blocker dons gloves and prepares the site (cleaning, draping) for the block. Where drapes cover the surgical site mark, the Assistant should ensure they can later reveal the mark for the Stop moment. Ideally, the surgical site mark should always be visible.

Step 2: Stop moment

The stop moment is a two-person step that happens only after preparation is complete and thus immediately before needle insertion. When ready, the Blocker formally announces that they have completed all preparation and is ready to block using a consistent form of words: “I’ve completed my prep; let’s Stop Before You Block”. The Assistant similarly should reply: OK, let’s Stop Before You Block”. The Blocker and Blocker’s Assistant together should then check the block side by viewing the surgical site mark and verbally confirming the correct side; the Assistant reconciles this with the consent form. If the patient is awake and unsedated, they may also confirm the side is correct.

Step 3: Block

Only when the correct side is confirmed does the Assistant hand the tray/container to the Blocker. The Blocker immediately performs the block. Any delay between handing back the tray and/or performing the block should require the Blocker and Assistant to re-start the SBYB process at Step 1. This re-start is to re-create a situation in which the block immediately follows the handing of tray from Assistant to Blocker. Re-start might be at the very start of the Preparation stage (e.g., if the site has become contaminated or later; but will always involve first handing the tray back to the Assistant.

Dr Nat Haslam
Consultant Anaesthetist, South Tyneside and Sunderland NHS Foundation Trust. Honorary Secretary RA-UK
[email protected]

Dr Nigel Bedforth
Consultant Anaesthetist, Nottingham University NHS Trust & Hon Associate Professor, University of Nottingham
[email protected]

Professor Jaideep J Pandit
University of Oxford
[email protected]


  1. Healthcare Safety Investigation Branch: Administering a wrong site nerve block. (accessed 2/11/2021)
  1. RA-UK website: Stop Before You Block (accessed 2/11/2021)
  1. Pandit JJ, Matthews, J, Pandit M. Editorial: ‘‘Mock before you block’’: an in-built action-check to prevent wrong-side anaesthetic nerve blocks. Anaesthesia 2017; 72: 150–155.
  1. Chikkabbaiah V, French J, Townsley P, Bedforth N. Further reducing the risk of wrong site block. Anaesthesia 2015; 70: 1453.
  1. Pollard R, Sivasubramaniam S. Stop before you block stickers. Anaesthesia 2017; 72: 1156–7.
  1. Hopping, M., Merry, A,F,. & Pandit, J,J. Exploring performance of, and attitudes to, Stop- and Mock-Before-You-Block in preventing wrong-side blocks. Anaesthesia 2018; 73: 421–7.


Please note that the information on this page is the same as that on the RA-UK website with permission.