Association of prehospital pupillary diameter with return of spontaneous circulation and neurological outcome after out-of-hospital cardiac arrest: A multicenter retrospective analysis

Background

In Japan, emergency medical services (EMS) routinely record pupillary size and pupillary light reflex (PLR) during prehospital care for out-of-hospital cardiac arrest (OHCA). While hospital-based studies have established the prognostic value of pupillary findings, the significance of prehospital pupillary diameter remains uncertain.

Objective

To examine whether pupillary diameter at EMS contact predicts prehospital return of spontaneous circulation (ROSC) and 30-day neurological outcomes.

Methods

This retrospective cohort study analyzed SOS-KANTO 2017, a prospective multicenter OHCA registry. Of 9909 adults, 8494 were eligible after excluding those not in arrest at EMS contact or with missing data. EMS personnel, trained in neurological assessment, documented pupillary diameter using standardized visual charts (0.5-mm increments) but recorded registry values in 1-mm categories (1–8 mm). The primary outcome was prehospital return of spontaneous circulation (ROSC), and the secondary outcome was 30-day favorable neurological status (CPC 1–2). Multivariable logistic regression adjusted for demographics, resuscitation factors, and Utstein variables. Receiver operating characteristic (ROC) analyses, treating failure to achieve ROSC as the positive condition, were performed to assess sensitivity, specificity, and false positive rate (FPR) for futility thresholds.

Results

Larger pupillary diameter was independently associated with reduced odds of favorable 30-day outcome (odds ratio [OR] per 1-mm increase, 0.73; 95 % CI 0.61–0.86; p < 0.001). Pupillary diameter was also inversely associated with achieving ROSC (OR per 1-mm increase, 0.694; 95 % CI 0.644–0.748; p < 0.001). Thresholds of ≥7–8 mm predicted failure to achieve ROSC with high specificity (0.93–0.99) but poor sensitivity.

Conclusions

Prehospital pupillary diameter is independently associated with both ROSC and 30-day neurological outcome. Although extreme dilation (≥7–8 mm) provides a highly specific marker of futility, low sensitivity precludes its use as a stand-alone criterion. Pupillary assessment may nonetheless contribute, in combination with other prehospital indicators, to a multimodal framework for early decision-making.