Pupillary Reflex; Roadside to Resus

We assess the pupils in almost every significantly unwell or injured patient - but how much are they really telling us? It is easy to document 'pupils equal and reactive' and move on, yet a changing pupil may be one of the earliest outward signs of a developing intracranial catastrophe. Equally, anisocoria in a completely well patient may be longstanding and entirely benign.

In this Roadside to Resus episode, we work through the anatomy and physiology of the pupillary light reflex before applying it to three important clinical situations: the blown pupil following a significant head injury, unequal or irregular pupils in a patient with a GCS of 15, and bilaterally fixed and dilated pupils in and following cardiac arrest, along with a deep dive into the evidence base.

We discuss how to decide which pupil is abnormal, the warning signs of third nerve palsy and Horner's syndrome, ocular and drug-related causes, and why serial change matters more than an isolated measurement. We also explore automated pupillometry, what the NPi can add, and why fixed pupils should never be used alone to determine futility or neurological prognosis.

Once again we'd love to hear any thoughts or feedback either on the website or via X @TheResusRoom!

Simon. Rob & James