Exploring automated pupillometry in comparison to the Withdrawal Assessment Tool-1 for the evaluation of opiate abstinence syndrome in pediatric critical care patients

Abstract

Research Question: In pediatric critical care patients tolerant to opiates, is automated pupillometry more sensitive in detecting opiate abstinence syndrome when compared to the gold standard observational scoring system?

Background: Opiates are often used in the Pediatric Intensive Care Unit to maintain analgesia and sedation. In doing so, pediatric patients quickly develop tolerance to opiates and must be slowly tapered off to avoid inducing opiate abstinence syndrome. Currently, the gold standard to evaluate for opiate abstinence syndrome is the Withdrawal Assessment Tool-1 (WAT-1), which is a 12-point subjective scale monitoring for symptoms of opiate withdrawal. There are currently no objective tools to evaluate for opiate abstinence syndrome in children. This study attempts to evaluate if automated pupillometry is an accurate and reliable tool to objectively evaluate for opiate abstinence syndrome in pediatric patients who are tolerant to opiates and undergoing an opiate taper. Since opiates are parasympathetic agonists, they stimulate pupillary constriction. Further, it has been shown that pupillary constriction develops tolerance similarly to the analgesic and euphoric tolerance. It is not until the opiate dose is manipulated that patients who are tolerant to opiates will show a change in pupil diameter. Therefore, it is reasonable to assume that automated pupillometry could accurately and reliably evaluate for opiate abstinence syndrome by objectively measuring pupillary changes as the patient tapers off opiates.

Materials and Methods: Opiate-tolerant patients in the pediatric intensive care unit were enrolled in this study. Data was collected twice daily. The WAT-1 scale was collected first, and then automated pupillometry was performed. The right eye was utilized to collect data on the pupillary light response, while the left eye was utilized to collect data on pupillary unrest without a light stimulus.

Results: Five patients were enrolled. Ages ranged from infancy to 10 years. Each automated pupillometry variable was correlated to total daily opiate dose, using Spearman’s rho correlation. WAT-1 scores were also correlated to total daily opiate dose and to each automated pupillometry variable using Spearman’s rho correlation. Of the limited data, the only significant findings were correlations between total daily opiate dose and initial pupil diameter (p=0.01) in Subject 2, total daily opiate dose and maximum constriction velocity (p=0.01) in Subject 2, and total daily opiate dose and pupillary unrest in Subject 4 when removing the last two time points (p=0.03). However, when analyzing Subject 4’s total duration on study, pupillary unrest did not significantly correlate to total daily opiate dose (p=0.16). Remaining data did not produce statistically significant correlations when p-value was set to ¿<0.05.

Conclusions: This exploratory study revealed some statistically significant correlations between automated pupillometry and total daily opiate dose, and no statistical significance between automated pupillometry and WAT-1 scores or between WAT-1 scores and total daily opiate dose. Therefore, the current study revealed automated pupillometry may be more sensitive to opiate abstinence syndrome when compared to the gold standard WAT-1 scoring system. However, limitations included small sample size, difficulty of device to capture pupils when surrounded by dark-colored irises, and difficulty of using device on subjects who were agitated while tapering off sedation. Future studies may examine use of ultrasound to measure pupil size.