More Safety Procedures Don't Necessarily Mean a Safer Workplace

November 1, 2026

What a wrong-site nerve block reveals about procedure overload and false assurance.

A 69-year-old man was booked for elective right ankle surgery at an NHS orthopaedic centre. Before the operation, he had a popliteal nerve block while awake, with the full “Stop Before You Block” (SBYB) check completed. He was then turned onto his back and given a general anaesthetic.

His oxygen saturation dropped. While the team worked to reposition his airway, the consultant administered a second nerve block — without repeating the SBYB check. It went into his left leg. The operating department practitioner caught the mistake only after the local anaesthetic had already been injected.

A box ticked for something that hadn't happened

The WHO Surgical Safety Checklist had been completed at sign-in, before the operation began. The Trust had gone further than the national version required, adding its own question asking whether the nerve-block site had been marked.

It had not been. The box was ticked anyway. As the operating department practitioner later explained to investigators, it was marked “when the question was asked of the consultant” — not because the marking actually existed. The checklist recorded an answer. It didn't record a fact.

This is the distinction the investigation keeps returning to: the difference between what a procedure says should happen, what people actually do, and what gets written down afterwards. Human factors researchers describe this as “work as imagined” (the mental model of how a task should go), “work as prescribed” (the written guidance), “work as done” (what actually happens), and “work as disclosed” (how people describe having done it). A completed checklist often tells us what someone has recorded or reported doing. It doesn't necessarily tell us what actually happened. Here, the gap between the procedure, the work as performed and the work as disclosed became critically important.

More guidance, same gap

Neither the national SBYB guidance nor the Trust's own local policy set out what to do when a patient needed more than one nerve block. Investigators found real variation in practice across the Trust on whether the check needed repeating before each one. The Trust had added a step beyond the national standard — and still hadn't covered the exact situation this patient needed.

The investigation found no effective evaluation of how SBYB was being performed in practice, or whether consultants were following the Trust's additional requirements. The extra steps had been introduced, but their effectiveness had not been established.

There was a human layer to this too. The practitioner and registrar in the room didn't challenge the consultant when the marking step was skipped. One described it as “taken as a given” that if a consultant departed from policy, nobody else would insist on it. The practitioner didn't see enforcing the marking as her role without the consultant's agreement. Adding a step to a checklist doesn't remove the need for someone to feel able to stop the person in charge — it just gives them one more thing to not act on.

HSSIB's own conclusion was direct: policies do not, on their own, form a robust safety barrier.

Five things to check tomorrow

Is a sign-off checked against physical reality, or just asked out loud? A box ticked because a question was posed is not the same as a box ticked because something was verified.
Does your guidance cover the situation that actually happens, or only the standard case? This Trust's gap was multiple blocks on one patient — check what your own procedures quietly assume won't happen twice.
Has anyone tested whether an added step actually works? A requirement introduced after a past incident deserves the same scrutiny as any other control — not just a place on the form.
What survives a distraction? The check that got skipped here was the one competing with an urgent airway problem. Decide in advance what happens to your checks under real pressure, not assumed calm.
Can the person doing the check challenge the person in charge? A procedure is only as strong as the least senior person's confidence to stop it.

The parallels sit close to home for industrial sites: a permit-to-work signed off without the isolation being physically confirmed, a safety-critical interlock bypass recorded as authorised without anyone independently verifying the actual plant condition, a pre-start inspection completed from memory in the cab, a maintenance sign-off for equipment nobody actually walked up to.

A procedure can tell someone what to do. A checklist can record that they did it. Neither guarantees it actually happened.

The next time a box gets ticked on your site, who's checking it means what it says?