Resting pupil size is a predictor of hypotension after induction of general anesthesia

Arterial hypotension is a major adverse effect of general anesthesia. Patients with pre-existing autonomic dysfunction are at greater risk of hypotension. This study was performed to examine whether objective measurement of the pupillary light reflex is predictive of intraoperative hypotension.

We studied 79 patients who underwent scheduled surgery under general anesthesia. Patients with severe cardiovascular disease or receiving antihypertensive agents were excluded. The light reflex was measured preoperatively using a portable infrared pupillometer, and the hemodynamic parameters were obtained from the anesthesia records. The patients were divided into two groups according to the development of hypotension: the hypotension and normotension groups. Multivariate logistic regression analysis was performed to determine the pupil parameters predictive of hypotension.

Patients in the hypotension group were older and had a greater pupil size or constriction velocity than those in the normotension group. Logistic regression analysis showed that post-induction hypotension was significantly associated with maximum pupil size or constriction velocity after adjustment for age and other clinical variables. Latency of the light reflex and the percent reduction of pupil size were not associated with hypotension. Age was a relatively strong predictor of hypotension; other confounding factors were not associated with hypotension.

Measurement of maximum pupil size is useful to identify patients at risk for intraoperative hypotension. The influence of age must be considered during measurement of the pupil response.

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