Pupillary Unrest: Is It a Generalizable Finding?

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We enjoyed the recent article by Neice et al,1 who measured pupillary unrest under ambient light (PUAL) before and after opioid administration in ambulatory surgical patients recovering from anesthesia. The authors found the magnitude of PUAL before opioid administration, in the postanesthesia care unit, to be predictive of analgesic response to opioid therapy postoperatively. This is interesting and potentially quite clinically useful.
According to the Centers for Disease Control and Prevention, 12.3% of Americans 20 years of age or older have diabetes, and 25.9% of Americans older than 65 years have diabetes. If present trends continue, as many as 1 in 3 American adults will have diabetes by the year 2050. Diabetic autonomic neuropathy is a serious and common complication of diabetes.2 Hreidarsson and Gundersen3 found that pupillary unrest was decreased by 35% with prolonged illumination and by 37% with brief illumination in patients with insulin-dependent diabetes compared to controls.
Although there is no mention of the number of patients with diabetes in the article by Neice et al,1 the mean age of patients studied was relatively young (36 ± 11 years at site C and 49 ± 18 years at site O). The only limitations mentioned were the exclusion of patients on chronic opioids and the fact that the 2 sites had slightly different protocols. We would argue that another important limitation is the fact that the predictive value of PUAL might be limited in an older population and patients with diabetes, both of whom are known to be at risk for autonomic dysfunction.
We applaud the authors for this interesting study, but further work may be needed before applying these findings to an older patient population with more comorbidities, which might be the group most likely to benefit from such technologies.
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