It’s not uncommon to hear anaesthesiologists drop verbal markers of universal truths into their clinical utterances: always, every, never. Often it's the most banal practices ("always attach the cannula tegaderm so") that generate our greatest passions.

However there are few, if any, universalisms in anaesthesia. Almost every rule has caveats and exceptions, reflecting the shades-of-grey reality of patient needs and human physiology.

When clinicians decree something is always or never so, they are often confusing truth with convention. Sometimes confusing an absolute with what is instead dogma. A minority reveal the rigidity of their thinking, impeding rather than enhancing the performance of their practice.

Rules are still useful. They are important guardrails, a mental model to keep us on the road of safety unless there is very good reason to cautiously edge onto the gravely shoulder, or even turn down a completely new path. But always with the understanding of the compromise we have intentionally made, reminding us of the cost that may need to be paid.

Universal anaesthesia rules become a problem when we dogmatically extol them without understanding the foundations of why – or use them as a blunt tool to browbeat our colleagues and assistants.

Rules are shortcuts to express the tension between the benefits and risks of different anaesthetic decisions. All difficult airways in specialty exams might require mandatory awake fiberoptic intubation, but in a real world of patient refusals and modern airway toys & techniques, it is a more nuanced decision. In fact, patient refusal might be the closest we get to an absolute rule – but even this is a negotiable area of greys.

As a mental model for normalising risk, rules are an efficient way to communicate our prioritisation of the risk-benefit tension. A tool for education and standard setting, without requiring the immediate overhead of qualifying and rationalising.

The danger comes when we confuse the mental model – the guardrails – for the reality. Misidentifying a tool to guide perception and practice, as something we mistakenly believe reality can be bent to. When we make this error, reality has a nasty habit of reasserting itself with unsentimental brutality.