The relevance of pupillometry for evaluation of analgesia before noxious procedures in the intensive care unit.

BACKGROUND

Many patients in the intensive care unit are unable to communicate verbally. Accurately predicting whether such patients will exhibit painful behaviors during noxious procedures and assessing the adequacy of analgesia during those procedures is a challenge. In addition to observational pain assessment tools such as the Behavioral Pain Scale, physiologic indicators such as the pupillary response have been proposed. The pupil is innervated by both divisions of the autonomic nervous system and is affected by pain and analgesic medications. We evaluated the pupillary response to a light stimulus before noxious procedures as a method to predict pain during the procedure.

METHODS

We correlated different aspects of the pupillary light reflex with established strategies for pain assessment to evaluate the adequacy of analgesia before surgical dressing changes performed in the intensive care unit in patients with cellulitis associated with mediastinitis or not.

RESULTS

We found that a percentage of variation in pupil size >19% predicted the presence of pain as assessed by a Behavioral Pain Scale score of >3 with a sensitivity of 100% (95% confidence interval, 100%-100%) and a specificity of 77% (95% confidence interval, 54%-100%).

CONCLUSIONS

In patients unable to communicate verbally, pupillometry may potentially guide caregivers to adjust analgesia before noxious procedures.