Automated Pupillometry for Prediction of Electroencephalographic Reactivity in Critically Ill Patients: A Prospective Cohort Study

Abstract

BackgroundElectroencephalography (EEG) is widely used to monitor critically ill patients. However, EEG interpretation requires the presence of an experienced neurophysiologist and is time-consuming. Aim of this study was to evaluate whether parameters derived from an automated pupillometer (AP) might help to assess the degree of cerebral dysfunction in critically ill patients.MethodsProspective study conducted in the Department of Intensive Care of Erasme University Hospital in Brussels, Belgium. Pupillary assessments were performed using the AP in three subgroups of patients, concomitantly monitored with continuous EEG: “anoxic brain injury”, “Non-anoxic brain injury” and “other diseases”. An independent neurologist blinded to patient's history and AP results scored the degree of encephalopathy and reactivity on EEG using a standardized scale. The mean value of Neurologic Pupil Index (NPi), pupillary size, constriction rate, constriction and dilation velocity (CV and DV) and latency for both eyes, obtained using the NPi®-200 (Neuroptics, Laguna Hills, CA, USA), were reported.ResultsWe included 214 patients (mean age 60 years, 55% male). EEG tracings were categorized as: mild (n = 111, 52%), moderate (n = 65, 30%) or severe (n = 16, 8%) encephalopathy; burst-suppression (n = 19, 9%) or suppression background (n = 3, 1%); a total of 38 (18%) EEG were classified as “unreactive”. We found a significant difference in all pupillometry variables among different EEG categories. Moreover, an unreactive EEG was associated with lower NPi, pupil size, pupillary reactivity, CV and DV and a higher latency than reactive recordings. Low DV (Odds ratio 0.020 [95% confidence intervals 0.002–0.163]; p < 0.01) was independently associated with an unreactive EEG, together with the use of analgesic/sedative drugs and high lactate concentrations. In particular, DV values had an area under the curve (AUC) of 0.86 [0.79–0.92; p < 0.01] to predict the presence of unreactive EEG. In subgroups analyses, AUC of DV to predict unreactive EEG was lower (0.72 [0.56–0.87]; p < 0.01) in anoxic brain injury than Non-anoxic brain injury (0.92 [0.85–1.00]; p < 0.01) and other diseases (0.96 [0.90–1.00]; p < 0.01).ConclusionsThis study suggests that low DV measured by the AP might effectively identify an unreactive EEG background, in particular in critically ill patients without anoxic brain injury.

Automated Pupillometry as an Assessment Tool for Intracranial Hemodynamics in Septic Patients

“…In a cohort of 100 mixed medical-surgical patients on mechanical ventilation, reduced PLR and constriction velocity at day 3 were independently associated with the occurrence of delirium [ 45 ]. A large study on 214 critically ill patients, including 21% diagnosed with sepsis, confirmed the high accuracy of low DV in detecting an unreactive electroencephalography in non-anoxic critically ill patients [ 46 ]. Contrary to this, a previous study of 92 septic and non-septic patients did not show any correlations between NPi and CA [ 24 ].…”

Application of Pupillometry in Neurocritical Patients

“…Another study also conducted by Godau revealed the potential of the NPi to assess treatment responses of NCSE [45]. In addition to the NPi, decreased dilation velocity (DV) was also discovered to have association with unreactive electroencephalography (EEG) signals, which is a possible utility in patients with seizure or critical illness [77].…”

Quantitative assessments of pupillary light reflexes in neurocritically ill patients

“…Moreover, lower %CH and CV in the early stages of intensive care unit (ICU) care were associated with the development of delirium irrespective of the baseline severity, analgesia, and sedation dose in sedated, mechanically ventilated ICU patients without brain injuries [35]. A prospective observational study based on ICU patients reported that a lower DV was independently related to unreactive EEG findings, indicating no EEG change in response to external stimuli in patients with brain injuries, such as stroke, traumatic brain injury, infection, and other medical diseases [41].…”