# Pre-operative fasting

> Pre-operative fasting is the period without food or drink before anaesthesia, intended to reduce the risk of stomach contents entering the lungs. Modern guidance permits clear fluids much closer to surgery than patients often assume. Misunderstood instructions cause avoidable cancellations and unnecessary discomfort, so confirming the patient understood them is part of assessment.

*Source: https://getpathways.ai/glossary/preoperative-fasting*

Also known as: fasting, nil by mouth, NBM, preoperative fasting

- **Purpose**: Reduce the risk of aspirating gastric contents under anaesthesia
- **Modern practice**: Clear fluids permitted considerably closer to surgery than solids
- **Common failure**: Patient fasts from the wrong time, or fasts unnecessarily long
- **Consequence**: Cancellation, or avoidable thirst, hunger and discomfort

## Two failure modes, opposite directions

The obvious one is a patient who has eaten too recently and whose case is
postponed or cancelled. The less visible one is a patient who fasts far longer
than required — often from midnight regardless of an afternoon list — arriving
dehydrated, uncomfortable and, for frail or diabetic patients, physiologically
worse off than necessary.

Contemporary guidance is considerably more permissive about clear fluids than
the "nil by mouth from midnight" instruction many patients still receive and
most expect. Encouraging clear fluids up to the point local guidance allows is
a standard component of enhanced recovery programmes.

## It is a communication failure, not a compliance failure

Patients who get fasting wrong have almost always tried to get it right. The
instruction reached them as a sentence on a letter, weeks before the date,
without a specific time attached, and often contradicted by what a relative
told them about their own operation.

That makes it one of the cheapest cancellation causes to prevent — and one of
the most irritating to lose a theatre slot to, because nothing clinical went
wrong. What is needed is that the instruction is delivered close enough to the
date to be remembered, specific enough to act on, and confirmed rather than
assumed.

Safety and shared decisions is one of the twelve domains the Socrates Pre-Op
interview covers, which is where instructions of this kind are checked as
understood rather than merely sent.