Reliability of standard pupillometry practice in neurocritical care: an observational, double-blinded study

Abstract

BackgroundIn critical care units, pupil examination is an important clinical parameter for patient monitoring. Current practice is to use a penlight to observe the pupillary light reflex. The result seems to be a subjective measurement, with low precision and reproducibility. Several quantitative pupillometer devices are now available, although their use is primarily restricted to the research setting. To assess whether adoption of these technologies would benefit the clinic, we compared automated quantitative pupillometry with the standard clinical pupillary examination currently used for brain-injured patients.MethodsIn order to determine inter-observer agreement of the device, we performed repetitive measurements in 200 healthy volunteers ranging in age from 21 to 58 years, providing a total of 400 paired (alternative right eye, left eye) measurements under a wide variety of ambient light condition with NeuroLight Algiscan pupillometer. During another period, we conducted a prospective, observational, double-blinded study in two neurocritical care units. Patients admitted to these units after an acute brain injury were included. Initially, nursing staff measured pupil size, anisocoria and pupillary light reflex. A blinded physician subsequently performed measurement using an automated pupillometer.ResultsIn 200 healthy volunteers, intra-class correlation coefficient for maximum resting pupil size was 0.95 (IC: 0.93-0.97) and for minimum pupil size after light stimulation 0.87 (0.83–0.89). We found only 3-pupil asymmetry (≥1 mm) in these volunteers (1.5 % of the population) with a clear pupil asymmetry during clinical inspection. The mean pupil light reactivity was 40 ± 7 %. In 59 patients, 406 pupillary measurements were prospectively performed. Concordance between measurements for pupil size collected using the pupillometer, versus subjective assessment, was poor (Spearmen's rho = 0.75, IC: 0.70-0.79; P < 0.001). Nursing staff failed to diagnose half of the cases (15/30) of anisocoria detected using the pupillometer device. A global rate of discordance of 18 % (72/406) was found between the two techniques when assessing the pupillary light reflex. For measurements with small pupils (diameters <2 mm) the error rate was 39 % (24/61).ConclusionStandard practice in pupillary monitoring yields inaccurate data. Automated quantitative pupillometry is a more reliable method with which to collect pupillary measurements at the bedside.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1239-z) contains supplementary material, which is available to authorized users.

Early prediction of coma recovery after cardiac arrest with blinded pupillometry

“…8 Even more importantly, recent reviews identified a number of limitations of all prognostication studies, particularly the lack of blinding, which may have led to some degree of self-fulfilling prophecy and to an overestimation of the specificity of outcome prognosticators. [10][11][12] Preliminary studies in comatose CA patients found that quantitative PLR performed better than standard clinical evaluation in predicting outcome. [10][11][12] Preliminary studies in comatose CA patients found that quantitative PLR performed better than standard clinical evaluation in predicting outcome.…”

“…4,9 Automated infrared pupillometry provides a quantitative measure of pupil size, pupillary light reflex (PLR), and constriction velocity, and is emerging as a novel modality to evaluate brainstem function at the bedside in critically ill patients. [10][11][12] Preliminary studies in comatose CA patients found that quantitative PLR performed better than standard clinical evaluation in predicting outcome. [13][14][15] Here, we examined, using a blinded approach, the accuracy of quantitative PLR in predicting 1-year neurological recovery of comatose CA patients.…”

Pupillary abnormalities in non-selected critically ill patients: an observational study

“…This scenario might be very frequent in ICUs, notably because of the routine use of morphine derivatives, which promote the occurrence of miosis (15). Indeed, several reports indicate that opioids given at anesthetic doses likely result in a decreased pupillary light constriction below the threshold of 0.3 mm (12,16,17). Therefore, we cannot rule out the fact that some of areflexia were false positives in our study.…”

“…Therefore, we cannot rule out the fact that some of areflexia were false positives in our study. Some PAs could also have been missed because of inadequate examinations or monitoring intervals (12,13,17). To date, the best way to limit misdiagnosis of PAs is probably to objectively measure the size and reactivity of pupils by using a handheld automated pupillometer (11,12,15 17).…”

Pain assessment by pupil dilation reflex in response to noxious stimulation in anaesthetized adults

“…Given the development of pupilometers with an integrated automated pupil tracking system,10 PDR can be used during surgical procedures in the operation room for nociceptive state evaluation 11, 12, 13…”