Pullilometry not effective method to assess pain in the emergency department

Pain management is crucial in Emergency Department(ED) patients. Research over the past several decades has led to significant improvement in the recognition and treatment of pain among all age groups. However, despite significant advances in the understanding of the mechanisms of pain much is yet to be known.

Popularly two dynamic pupillary measures are used in conscious subjects after a surgical procedure that are known to correlate to the magnitude of ongoing pain. However a recent study conducted by Belgian investigators suggests clinicians should not rely on pupil diameter or its response to light to assess pain levels among emergency department (ED) patients, and it is reported in the European Journal of Pain.

Charles Gregoire and team aimed to test the ability of dynamic measures derived from pupillometry to evaluate pain intensity in conscious adult patients admitted to the ED. The study was a prospective, interventional, single-centre study performed between August 2021 and January 2022 (NCT05019898). An assessment of self-reported pain intensity was performed on ED admission by the triage nurse using a numeric rating scale (NRS). This was followed by two dynamic measures derived from pupillometry that were previously correlated with pain perception: the pupillary unrest under ambient light (PUAL) and the pupillary light reflex (PLR).

The key findings of the study are

• Among the 313 analysed patients, the median age was 41 years, and 52% were women.

• Overall, 40.0% of patients rated their pain as absent or mild (numeric rating scale score less than 4), 32.3% as moderate (4 to less than 7), and 27.7% as severe (7 or greater).

• Patients’ scores did not correlate either with the pupillary unrest under ambient light measure (r, 0.007) or with the pupillary light reflex measures of baseline diameter (r, −0.048), decrease (r, 0.024), latency (r, 0.019), or slope (r, −0.051). Findings were similar for men and women individually.

• Similarly, the pupillometry measures could not discriminate patients with moderate to severe pain (defined as NRS ≥4).

Researchers ended Pupillometry does not appear to be an effective tool to evaluate pain in the ED environment. Indeed, too many factors influencing the sympathetic system and thus the dynamic pupillary measures are not controllable in the ED.

Reference: Charles Gregoire, David Charier et al ; Comparison between pupillometry and numeric pain rating scale for pain assessments in communicating adult patients in the emergency department; European journal of pain, 11 June 2023, DOI:https://doi.org/10.1002/ejp.2137