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

Acute Ischemic Stroke during Extracorporeal Membrane Oxygenation (ECMO): A Narrative Review of the Literature

Ischemic stroke (IS) is a severe complication and leading cause of mortality in patients under extracorporeal membrane oxygenation (ECMO). The aim of our narrative review is to summarize the existing evidence and provide a deep examination of the diagnosis and treatment of acute ischemic stroke patients undergoing ECMO support. The incidence rate of ISs is estimated to be between 1 and 8%, while the mortality rate ranges from 44 to 76%, depending on several factors, including ECMO type, duration of support and patient characteristics. Several mechanisms leading to ISs during ECMO have been identified, with thromboembolic events and cerebral hypoperfusion being the most common causes. However, considering that most of the ECMO patients are severely ill or under sedation, stroke symptoms are often underdiagnosed. Multimodal monitoring and daily clinical assessment could be useful preventive techniques. Early recognition of neurological deficits is of paramount importance for prompt therapeutic interventions. All ECMO patients with suspected strokes should immediately receive brain computed tomography (CT) and CT angiography (CTA) for the identification of large vessel occlusion (LVO) and assessment of collateral blood flow. CT perfusion (CTP) can further assist in the detection of viable tissue (penumbra), especially in cases of strokes of unknown onset. Catheter angiography is required to confirm LVO detected on CTA. Intravenous thrombolytic therapy is usually contraindicated in ECMO as most patients are on active anticoagulation treatment. Therefore, mechanical thrombectomy is the preferred treatment option in cases where there is evidence of LVO. The choice of the arterial vascular access used to perform mechanical thrombectomy should be discussed between interventional radiologists and an ECMO team. Anticoagulation management during the acute phase of IS should be individualized after the thromboembolic risk has been carefully balanced against hemorrhagic risk. A multidisciplinary approach is essential for the optimal management of ISs in patients treated with ECMO.

Smartphone pupillometry for detection of cerebral vasospasm after aneurysmal subarachnoid hemorrhage

OBJECTIVES

Vasospasm is a complication of aneurysmal subarachnoid hemorrhage (aSAH) that can change the trajectory of recovery and is associated with morbidity and mortality. Earlier detection of vasospasm could improve patient outcomes. Our objective is to evaluate the accuracy of smartphone-based quantitative pupillometry in the detection of radiographic vasospasm and delayed cerebral ischemia (DCI) after aSAH.

MATERIALS AND METHODS

We prospectively collected pupillary light reflex (PLR) parameters from patients with aSAH admitted to a neurocritical care unit at a single hospital twice daily using quantitative smartphone pupillometry recordings. PLR parameters included: Maximum pupil diameter, minimum pupil diameter, percent change in pupil diameter, latency in beginning of pupil constriction to light, mean constriction velocity, maximum constriction velocity, and mean dilation velocity. Two-tailed t-tests for independent samples were performed to determine changes in average concurrent PLR parameter values between the following comparisons: (1) patients with and without radiographic vasospasm (defined by angiography with the need for endovascular intervention) and (2) patients with and without DCI.

RESULTS

49 subjects with aSAH underwent 323 total PLR recordings. For PLR recordings taken with (n=35) and without (n=241) radiographic vasospasm, significant differences were observed in MIN (35.0 ± 7.5 pixels with vasospasm versus 31.6 ± 6.2 pixels without; p=0.002). For PLR recordings taken with (n=43) and without (n=241) DCI, significant differences were observed in MAX (48.9 ± 14.3 pixels with DCI versus 42.5 ± 9.2 pixels without; p<0.001).

CONCLUSIONS

Quantitative smartphone pupillometry has the potential to be used to detect radiographic vasospasm and DCI after aSAH.

Quantitative Pupillometry: Clinical Applications for the Internist

From the time of Galen, examination of the pupillary light reflex has been a standard of care across the continuum of health care. The growing body of evidence overwhelmingly supports the use of quantitative pupillometry over subjective examination with flashlight or penlight. At current time, pupillometers have become standard of care in many hospitals across 6 continents. This review paper provides an overview and rationale for pupillometer use and highlights literature supporting pupillometer-derived measures of the pupillary light reflex in both neurological and non-neurological patients across the health care continuum.

Prediction of neurocritical care intensity through automated infrared pupillometry and transcranial doppler in blunt traumatic brain injury: the NOPE study

PURPOSE

This pilot study aimed to determine the capacity of automated infrared pupillometry (AIP) alone and in combination with transcranial doppler (TCD) on admission to rule out need for intense neuroAQ2 critical care (INCC) in severe traumatic brain injury (TBI).

METHODS

In this observational pilot study clinicians performed AIP and TCD measurements on admission in blunt TBI patients with a Glasgow Coma Score (GCS) < 9 and/or motor score < 6. A Neurological Pupil index (NPi) < 3, Pulsatility Index (PI) > 1,4 or diastolic blood flow velocity (dV) of < 20 cm/s were used to rule out the need for INCC (exceeding the tier 0 Seattle Consensus Conference). The primary outcome was the negative likelihood ratio (nLR) of NPi < 3 alone or in combination with TCD to detect need for INCC.

RESULTS

A total of 69 TBI patients were included from May 2019 to September 2020. Of those, 52/69 (75%) median age was 45 [28-67], median prehospital GCS of 7 [5-8], median Injury Severity Scale of 13.0 [6.5-25.5], median Marshall Score of 4 [3-5], the median Glasgow Outcome Scale at discharge was 3 [1-5]. NPi < 3 was an independent predictor of INCC. NPi demonstrated a nLR of 0,6 (95%CI 0.4-0.9; AUROC, 0.65, 95% CI 0.51-0.79), a combination of NPi and TCD showed a nLR of 0.6 (95% CI 0.4-1.0; AUROC 0.67 95% CI 0.52-0.83) to predict INCC.

CONCLUSION

This pilot study suggests a possible useful contribution of NPi to determine the need for INCC in severe blunt TBI patients on admission.

Non-invasive technology for brain monitoring: definition and meaning of the principal parameters for the International PRactice On TEChnology neuro-moniToring group (I-PROTECT)

Technologies for monitoring organ function are rapidly advancing, aiding physicians in the care of patients in both operating rooms (ORs) and intensive care units (ICUs). Some of these emerging, minimally or non-invasive technologies focus on monitoring brain function and ensuring the integrity of its physiology. Generally, the central nervous system is the least monitored system compared to others, such as the respiratory, cardiovascular, and renal systems, even though it is a primary target in most therapeutic strategies. Frequently, the effects of sedatives, hypnotics, and analgesics are entirely unpredictable, especially in critically ill patients with multiple organ failure. This unpredictability exposes them to the risks of inadequate or excessive sedation/hypnosis, potentially leading to complications and long-term negative outcomes. The International PRactice On TEChnology neuro-moniToring group (I-PROTECT), comprised of experts from various fields of clinical neuromonitoring, presents this document with the aim of reviewing and standardizing the primary non-invasive tools for brain monitoring in anesthesia and intensive care practices. The focus is particularly on standardizing the nomenclature of different parameters generated by these tools. The document addresses processed electroencephalography, continuous/quantitative electroencephalography, brain oxygenation through near-infrared spectroscopy, transcranial Doppler, and automated pupillometry. The clinical utility of the key parameters available in each of these tools is summarized and explained. This comprehensive review was conducted by a panel of experts who deliberated on the included topics until a consensus was reached. Images and tables are utilized to clarify and enhance the understanding of the clinical significance of non-invasive neuromonitoring devices within these medical settings.

Agreement and repeatability of scotopic pupil size measurement with the 2WIN-S portable refractor in Chinese adults

To assess the agreement and repeatability of scotopic pupil size measurement using 2WIN-S (Adaptica, Padova, Italy) portable refractor in Chinese adults. This prospective non-randomized open-label controlled study assessed the scotopic pupil size of 100 right eyes using OPD-Scan III (Optical path difference) (Nidek Technologies, Gamagori, Japan) and 2WIN-S. OPD-Scan III and 2WIN-S measure pupil size using infrared light and detector, while 2WIN-S measures bilateral eyes simultaneously, OPD-Scan III measures unilateral eyes individually. Participants were first measured once using OPD-Scan III and two consecutive measurements were performed using 2WIN-S after 15 min of rest interval. The primary outcome was to evaluate the agreement between 2WIN-S and OPD-Scan III, and the secondary outcome was to evaluate the repeatability of 2WIN-S. Scotopic pupil size of 100 right eyes of 100 adults (28 male and 72 female) aged 18-53 years (mean 36 ± 12 years) was assessed using OPD-Scan III and 2WIN-S, respectively. The mean scotopic pupil size of OPD-Scan III and 2WIN-S was recorded to be 6.24 ± 0.88 mm and 6.27 ± 0.81 mm, respectively. For the mean scotopic pupil size of OPD-Scan III and 2WIN-S the difference was - 0.03 mm (95%CI - 0.10 to 0.04 mm), p = 0.445, the 95% limits of agreement (LOA) was - 0.71 to 0.66 mm. ICC between the two devices was 0.92 (95% CI 0.88-0.94) (ICC > 0.9 indicates excellent consistency). Coefficients of repeatability (CoR) of 2WIN-S was 0.37, which has a high repeatability. For the mean scotopic pupil size of 2WIN-S of the repeated measurements, the difference was -0.04 mm (95%CI - 0.08 to 0.01 mm), p = 0.019, the 95% limits of agreement (LOA) was - 0.41 to 0.32 mm, with a narrow LOA. However, the majority of the variations were less than ± 0.50 mm (98% of scotopic pupil size measurements were below this threshold), within the clinically acceptable range (± 0.50 mm). Our study showed excellent agreement between 2WIN-S and OPD-Scan III (ICC > 0.9) and a good repeatability of 2WIN-S (CoR = 0.37). This study suggests a novel technique for measuring pupillary responses in low light conditions, which can be considered an alternative to OPD-Scan III in clinical settings.

Quantitative Pupillometry Predicts Return to Play and Tracks the Clinical Evolution of Mild Traumatic Brain Injury in US Military Academy Cadets: A Military Traumatic Brain Injury Initiative Study

BACKGROUND AND OBJECTIVES

The objective of this study was to determine the utility of the pupillary light reflex use as a biomarker of mild traumatic brain injury (mTBI).

METHODS

This prospective cohort study was conducted at The US Military Academy at West Point. Cadets underwent a standard battery of tests including Balance Error Scoring System, Sports Concussion Assessment Tool Fifth Edition Symptom Survey, Standard Assessment of Concussion, and measure of pupillary responses. Cadets who sustained an mTBI during training events or sports were evaluated with the same battery of tests and pupillometry within 48 hours of the injury (T1), at the initiation of a graded return to activity protocol (T2), and at unrestricted return to activity (T3).

RESULTS

Pupillary light reflex metrics were obtained in 1300 cadets at baseline. During the study period, 68 cadets sustained mTBIs. At T1 (<48 hours), cadets manifested significant postconcussion symptoms (Sports Concussion Assessment Tool Fifth Edition P < .001), and they had decreased cognitive performance (Standardized Assessment of Concussion P < .001) and higher balance error scores (Balance Error Scoring System P < .001) in comparison with their baseline assessment (T0). The clinical parameters showed normalization at time points T2 and T3. The pupillary responses demonstrated a pattern of significant change that returned to normal for several measures, including the difference between the constricted and initial pupillary diameter (T1 P < .001, T2 P < .05), dilation velocity (T1 P < .01, T2 P < .001), and percent of pupillary constriction (T1 P < .05). In addition, a combination of dilation velocity and maximum constriction velocity demonstrates moderate prediction ability regarding who can return to duty before or after 21 days (area under the curve = 0.71, 95% CI [0.56-0.86]).

CONCLUSION

This study's findings indicate that quantitative pupillometry has the potential to assist with injury identification and prediction of symptom severity and duration.

Update in Pediatric Neurocritical Care: What a Neurologist Caring for Critically Ill Children Needs to Know

Currently nearly one-quarter of admissions to pediatric intensive care units (PICUs) worldwide are for neurocritical care diagnoses that are associated with significant morbidity and mortality. Pediatric neurocritical care is a rapidly evolving field with unique challenges due to not only age-related responses to primary neurologic insults and their treatments but also the rarity of pediatric neurocritical care conditions at any given institution. The structure of pediatric neurocritical care services therefore is most commonly a collaborative model where critical care medicine physicians coordinate care and are supported by a multidisciplinary team of pediatric subspecialists, including neurologists. While pediatric neurocritical care lies at the intersection between critical care and the neurosciences, this narrative review focuses on the most common clinical scenarios encountered by pediatric neurologists as consultants in the PICU and synthesizes the recent evidence, best practices, and ongoing research in these cases. We provide an in-depth review of (1) the evaluation and management of abnormal movements (seizures/status epilepticus and status dystonicus); (2) acute weakness and paralysis (focusing on pediatric stroke and select pediatric neuroimmune conditions); (3) neuromonitoring modalities using a pathophysiology-driven approach; (4) neuroprotective strategies for which there is evidence (e.g., pediatric severe traumatic brain injury, post-cardiac arrest care, and ischemic stroke and hemorrhagic stroke); and (5) best practices for neuroprognostication in pediatric traumatic brain injury, cardiac arrest, and disorders of consciousness, with highlights of the 2023 updates on Brain Death/Death by Neurological Criteria. Our review of the current state of pediatric neurocritical care from the viewpoint of what a pediatric neurologist in the PICU needs to know is intended to improve knowledge for providers at the bedside with the goal of better patient care and outcomes.

The use of quantitative pupillometry in brain death determination: preliminary findings

PURPOSE

Quantitative pupillometry (QP) has been increasingly applied in neurocritical care as an easy-to-use and reliable technique for evaluating the pupillary light reflex (PLR). Here, we report our preliminary findings on using QP for clinical brain death (BD) determination.

MATERIALS

This retrospective study included 17 patients ≥ 18 years (mean age, 57.3 years; standard deviation, 15.8 years) with confirmed BD, as defined by German Guidelines for the determination of BD. The PLR was tested using the NPi®-200 Pupillometer (Neuroptics, Laguna Hill, USA), a handheld infrared device automatically tracking and analyzing pupil dynamics over 3 s. In addition, pupil diameter and neurological pupil index (NPi) were also evaluated.

RESULTS

Intracerebral bleeding, subarachnoid hemorrhage, and hypoxic encephalopathy were the most prevalent causes of BD. In all patients, the NPi was 0 for both eyes, indicating the cessation of mid-brain function. The mean diameter was 4.9 mm (± 1.3) for the right pupil and 5.2 mm (±1.2) for the left pupil.

CONCLUSIONS

QP is a valuable tool for the BD certification process to assess the loss of PLR due to the cessation of brain stem function. Furthermore, implementing QP before the withdrawal of life-sustaining therapy in brain-injured patients may reduce the rate of missed organ donation opportunities. Further studies are warranted to substantiate the feasibility and potential of this technique in treating patients and identify suitable candidates for this technique during the BD certification process.

Machine learning approach for ambient-light-corrected parameters and the Pupil Reactivity (PuRe) score in smartphone-based pupillometry

Introduction

The pupillary light reflex (PLR) is the constriction of the pupil in response to light. The PLR in response to a pulse of light follows a complex waveform that can be characterized by several parameters. It is a sensitive marker of acute neurological deterioration, but is also sensitive to the background illumination in the environment in which it is measured. To detect a pathological change in the PLR, it is therefore necessary to separate the contributions of neuro-ophthalmic factors from ambient illumination. Illumination varies over several orders of magnitude and is difficult to control due to diurnal, seasonal, and location variations.

Methods and results

We assessed the sensitivity of seven PLR parameters to differences in ambient light, using a smartphone-based pupillometer (AI Pupillometer, Solvemed Inc.). Nine subjects underwent 345 measurements in ambient conditions ranging from complete darkness (<5 lx) to bright lighting (≲10,000 lx). Lighting most strongly affected the initial pupil size, constriction amplitude, and velocity. Nonlinear models were fitted to find the correction function that maximally stabilized PLR parameters across different ambient light levels. Next, we demonstrated that the lighting-corrected parameters still discriminated reactive from unreactive pupils. Ten patients underwent PLR testing in an ophthalmology outpatient clinic setting following the administration of tropicamide eye drops, which rendered the pupils unreactive. The parameters corrected for lighting were combined as predictors in a machine learning model to produce a scalar value, the Pupil Reactivity (PuRe) score, which quantifies Pupil Reactivity on a scale 0-5 (0, non-reactive pupil; 0-3, abnormal/"sluggish" response; 3-5, normal/brisk response). The score discriminated unreactive pupils with 100% accuracy and was stable under changes in ambient illumination across four orders of magnitude.

Discussion

This is the first time that a correction method has been proposed to effectively mitigate the confounding influence of ambient light on PLR measurements, which could improve the reliability of pupillometric parameters both in pre-hospital and inpatient care settings. In particular, the PuRe score offers a robust measure of Pupil Reactivity directly applicable to clinical practice. Importantly, the formulae behind the score are openly available for the benefit of the clinical research community.

Video versus ultrasound pupillometry for detecting increased pupillary diameters due to nociceptive stimuli: a prospective observational study

PURPOSE

Ultrasound pupillometry (UP) is a potential alternative to video pupillometry (VP) for assessing changes in patients' pupillary diameter (ΔPD) due to surgical nociception, but the reproducibility of UP and VP has been unclear. We evaluated the reproducibility of nociceptive ΔPD measured with both methods.

SUBJECTS AND METHODS

This prospective observational trial with 15 healthy volunteers aged ≥ 18 years was conducted at a Japanese teaching hospital. The ΔPD due to tetanic stimuli randomly applied at 10-60 mA was measured with VP and UP. The primary outcome was the correlation between the ΔPD measured with VP and that measured with UP. The secondary outcome was the agreement between the methods. We also evaluated ΔPD pattern changes due to the raised pain intensity in each method.

RESULTS

The noxious ΔPD values of UP were weakly but significantly correlated with those of VP (Spearman's ρ = 0.38, p < 0.001). A significant constant error was identified between the two measurements (Bland-Altman: mean of the difference in ΔPD (VP - UP), - 0.4 [95% CI: - 0.52 to - 0.28, p < 0.001], generalized estimating equation: a beta estimator of ΔPD: 0.41, [95% CI: 0.26-0.56, p < 0.001]). The ΔPD pattern changes due to the raised tetanic stimuli were almost the same in the two methods.

CONCLUSION

Due to the significant constant error, we consider the reproducibility of the measured ΔPD between UP and VP moderate. Trial registry number UMIN 000047145. Prior to the subjects' enrollment, the trial was registered with the University Hospital Medical Information Network (Principal investigator: Mao Konno, Date of registration: 3.11.2022). https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000053778 .

Noninvasive Neuromonitoring Modalities in Children Part I: Pupillometry, Near-Infrared Spectroscopy, and Transcranial Doppler Ultrasonography

BACKGROUND

Noninvasive neuromonitoring in critically ill children includes multiple modalities that all intend to improve our understanding of acute and ongoing brain injury.

METHODS

In this article, we review basic methods and devices, applications in clinical care and research, and explore potential future directions for three noninvasive neuromonitoring modalities in the pediatric intensive care unit: automated pupillometry, near-infrared spectroscopy, and transcranial Doppler ultrasonography.

RESULTS

All three technologies are noninvasive, portable, and easily repeatable to allow for serial measurements and trending of data over time. However, a paucity of high-quality data supporting the clinical utility of any of these technologies in critically ill children is currently a major limitation to their widespread application in the pediatric intensive care unit.

CONCLUSIONS

Future prospective multicenter work addressing major knowledge gaps is necessary to advance the field of pediatric noninvasive neuromonitoring.

Neuromonitoring in Children with Traumatic Brain Injury

Traumatic brain injury remains a major cause of mortality and morbidity in children across the world. Current management based on international guidelines focuses on a fixed therapeutic target of less than 20 mm Hg for managing intracranial pressure and 40-50 mm Hg for cerebral perfusion pressure across the pediatric age group. To improve outcome from this complex disease, it is essential to understand the pathophysiological mechanisms responsible for disease evolution by using different monitoring tools. In this narrative review, we discuss the neuromonitoring tools available for use to help guide management of severe traumatic brain injury in children and some of the techniques that can in future help with individualizing treatment targets based on advanced cerebral physiology monitoring.

Recovery and Survival of Patients After Out-of-Hospital Cardiac Arrest: A Literature Review Showcasing the Big Picture of Intensive Care Unit-Related Factors

As an important public health issue, out-of-hospital cardiac arrest (OHCA) requires several stages of high quality medical care, both on-field and after hospital admission. Post-cardiac arrest shock can lead to severe neurological injury, resulting in poor recovery outcome and increased risk of death. These characteristics make this condition one of the most important issues to deal with in post-OHCA patients hospitalized in intensive care units (ICUs). Also, the majority of initial post-resuscitation survivors have underlying coronary diseases making revascularization procedure another crucial step in early management of these patients. Besides keeping myocardial blood flow at a satisfactory level, other tissues must not be neglected as well, and maintaining mean arterial pressure within optimal range is also preferable. All these procedures can be simplified to a certain level along with using targeted temperature management methods in order to decrease metabolic demands in ICU-hospitalized post-OHCA patients. Additionally, withdrawal of life-sustaining therapy as a controversial ethical topic is under constant re-evaluation due to its possible influence on overall mortality rates in patients initially surviving OHCA. Focusing on all of these important points in process of managing ICU patients is an imperative towards better survival and complete recovery rates.

The Role of Automated Infrared Pupillometry in Traumatic Brain Injury: A Narrative Review

Pupillometry, an integral component of neurological examination, serves to evaluate both pupil size and reactivity. The conventional manual assessment exhibits inherent limitations, thereby necessitating the development of portable automated infrared pupillometers (PAIPs). Leveraging infrared technology, these devices provide an objective assessment, proving valuable in the context of brain injury for the detection of neuro-worsening and the facilitation of patient monitoring. In cases of mild brain trauma particularly, traditional methods face constraints. Conversely, in severe brain trauma scenarios, PAIPs contribute to neuro-prognostication and non-invasive neuromonitoring. Parameters derived from PAIPs exhibit correlations with changes in intracranial pressure. It is important to acknowledge, however, that PAIPs cannot replace invasive intracranial pressure monitoring while their widespread adoption awaits robust support from clinical studies. Ongoing research endeavors delve into the role of PAIPs in managing critical neuro-worsening in brain trauma patients, underscoring the non-invasive monitoring advantages while emphasizing the imperative for further clinical validation. Future advancements in this domain encompass sophisticated pupillary assessment tools and the integration of smartphone applications, emblematic of a continually evolving landscape.

Nociception assessment with videopupillometry in deeply sedated intensive care patients: Discriminative and criterion validations

BACKGROUND

Nociceptive assessment in deeply sedated patients is challenging. Validated instruments are lacking for this unresponsive population. Videopupillometry is a promising tool but has not been established in intensive care settings.

AIM/OBJECTIVE

To test the discriminate validity of pupillary dilation reflex (PDR) between non-noxious and noxious procedures for assessing nociception in non-neurological intensive care unit (ICU) patients and to test the criterion validity of pupil dilation using recommended PDR cut-off points to determine nociception.

METHODS

A single-centre prospective observational study was conducted in medical-surgical ICU patients. Two independent investigators performed videopupillometer measurements during a non-noxious and a noxious procedure, once a day (up to 7 days), when the patient remained deeply sedated (Richmond Agitation-Sedation Scale score: -5 or -4). The non-noxious procedures consisted of a gentle touch on each shoulder and the noxious procedures were endotracheal suctioning or turning onto the side. Bivariable and multivariable general linear mixed models were used to account for multiple measurements in same patients. Sensitivity and specificity, and areas under the curve of the receiver operating characteristic curve were calculated.

RESULTS

Sixty patients were included, and 305 sets of 3 measurements (before, during, and after), were performed. PDR was higher during noxious procedures than before (mean difference between noxious and non-noxious procedures = 31.66%). After testing all variables of patient and stimulation characteristics in bivariable models, age and noxious procedures were kept in the multivariable model. Adjusting for age, noxious procedures (coefficient = -15.14 (95% confidence interval = -20.17 to -15.52, p < 0.001) remained the only predictive factor for higher pupil change. Testing recommended cut-offs, a PDR of >12% showed a sensitivity of 65%, and a specificity of 94% for nociception prediction, with an area under the receiver operating curve of 0.828 (95% confidence interval = 0.779-0.877).

CONCLUSIONS

In conclusion, PDR is a potentially appropriate measure to assess nociception in deeply sedated ICU patients, and we suggest considering its utility in daily practices.

REGISTRATION

This study was not preregistered in a clinical registry.

TWEETABLE ABSTRACT

Pupillometry may help clinicians to assess nociception in deeply sedated ICU patients.

Assessing Cognitive Effort in Ménière's Disease: Pupillometry as a Novel Tool for Postural Control

BACKGROUND

This study aimed to investigate the utility of pupillometry as a measure of cognitive effort in individuals with Ménière's disease experiencing chronic postural destabilization. By integrating pupillometry with static posturography, we sought to gain deeper insights into the cognitive demands and arousal levels associated with postural control in this specific patient population.

METHODS

The study included 36 patients who met the diagnostic criteria for Ménière's disease and a control group comprising 36 healthy volunteers. We performed static posturography using a computerized static posturography platform to objectively assess postural imbalance. Additionally, pupillometry was recorded using infrared video-oculoscopy. Pupil dilation was measured before and after participants walked for 7 steps on-site with their vision obscured.

RESULTS

Baseline tonic pupil size showed no significant difference between healthy controls and Ménière's patients. However, after walking stimulation, Ménière's patients exhibited highly significant abnormal walking-induced pupil dilation. This suggests increased arousal in response to the challenging task of walking with closed eyes, linked to static upright stance imbalance as correlated with posturography parameters.

CONCLUSION

Pupillometry holds promise as an objective tool to assess cognitive effort and arousal during postural control in Ménière's disease. Implementing pupillometry in clinical practice could enhance the management of postural instability in these patients. Our findings contribute to the understanding of cognitive aspects in balance control and open new avenues for further investigations in vestibular dysfunction.

A smartphone pupillometry tool for detection of acute large vessel occlusion

OBJECTIVES

Pupillary light reflex (PLR) parameters can be used as quantitative biomarkers of neurological function. Since digital infrared pupillometry is expensive, we sought to examine alterations in PLR parameters using a smartphone quantitative pupillometry platform in subjects with acute ischemic stroke (AIS).

MATERIALS AND METHODS

Patients were enrolled if they presented to the emergency department as a stroke code activation and had evidence of a large vessel occlusion (LVO) on computed tomography angiography. Controls were enrolled from hospital staff. A smartphone pupillometer was used in AIS patients with LVO pre-mechanical thrombectomy, immediately post-thrombectomy, and at 24 h post-thrombectomy. Clinical and demographic data were collected, along with the proprietary Neurological Pupil index (NPi) score from the NPi-200 digital infrared pupillometer. PLR parameters were compared using mean differences. The absolute and non-absolute inter-eye difference in each parameter for each subject were also analyzed by measuring 1 - (R:L) to determine alteration in the equilibrium between subject pupils. The NPi was analyzed for mean differences between cohorts.

RESULTS

Healthy controls (n = 132) and AIS patients (n = 31) were enrolled. Significant differences were observed in PLR parameters for healthy subjects when compared to pre-thrombectomy subjects in both mean and absolute inter-eye differences after post hoc Bonferroni correction. The proprietary NPi score was not significantly different for all groups and comparisons.

CONCLUSIONS

Significant alterations in the PLR were observed in AIS patients with LVO before thrombectomy, indicating the potential use of smartphone pupillometry for detection of LVO.

Neuromonitoring During ECMO Support in Children

Extracorporeal membrane oxygenation is a potentially lifesaving intervention for children with severe cardiac or respiratory failure. It is used with increasing frequency and in increasingly more complex and severe diseases. Neurological injuries are important causes of morbidity and mortality in children treated with extracorporeal membrane oxygenation and include ischemic stroke, intracranial hemorrhage, hypoxic-ischemic injury, and seizures. In this review, we discuss the epidemiology and pathophysiology of neurological injury in patients supported with extracorporeal membrane oxygenation, and we review the current state of knowledge for available modalities of monitoring neurological function in these children. These include structural imaging with computed tomography and ultrasound, cerebral blood flow monitoring with near-infrared spectroscopy and transcranial Doppler ultrasound, and physiological monitoring with electroencephalography and plasma biomarkers. We highlight areas of need and emerging advances that will improve our understanding of neurological injury related to extracorporeal membrane oxygenation and help to reduce the burden of neurological sequelae in these children.

Validation of the MIRACLE2 Score for Prognostication After Out-of-hospital Cardiac Arrest

Background

Out-of-hospital cardiac arrest (OHCA) is associated with very poor clinical outcomes. An optimal pathway of care is yet to be defined, but prognostication is likely to assist in the challenging decision-making required for treatment of this high-risk patient cohort. The MIRACLE2 score provides a simple method of neuro-prognostication but as yet it has not been externally validated. The aim of this study was therefore to retrospectively apply the score to a cohort of OHCA patients to assess the predictive ability and accuracy in the identification of neurological outcome.

Methods

Retrospective data of patients identified by hospital coding, over a period of 18 months, were collected from a large tertiary-level cardiac centre with a mature, multidisciplinary OHCA service. MIRACLE2 score performance was assessed against three existing OHCA prognostication scores.

Results

Patients with all-comer OHCA, of presumed cardiac origin, with and without evidence of ST-elevation MI (43.4% versus 56.6%, respectively) were included. Regardless of presentation, the MIRACLE2 score performed well in neuro-prognostication, with a low MIRACLE2 score (≤2) providing a negative predictive value of 94% for poor neurological outcome at discharge, while a high score (≥5) had a positive predictive value of 95%. A high MIRACLE2 score performed well regardless of presenting ECG, with 91% of patients receiving early coronary angiography having a poor outcome.

Conclusion

The MIRACLE2 score has good prognostic performance and is easily applicable to cardiac-origin OHCA presentation at the hospital front door. Prognostic scoring may assist decision-making regarding early angiographic assessment.

Describing Anisocoria in Neurocritically Ill Patients

BACKGROUND

Anisocoria (unequal pupil size) has been defined using cut points ranging from greater than 0.3 mm to greater than 2.0 mm for absolute difference in pupil size. This study explored different pupil diameter cut points for assessing anisocoria as measured by quantitative pupillometry before and after light stimulus.

METHODS

An exploratory descriptive study of international registry data was performed. The first observations in patients with paired left and right quantitative pupillometry measurements were included. Measurements of pupil size before and after stimulus with a fixed light source were used to calculate anisocoria.

RESULTS

The sample included 5769 patients (mean [SD] age, 57.5 [17.6] years; female sex, 2558 patients [51.5%]; White race, 3669 patients [75.5%]). Anisocoria defined as pupil size difference of greater than 0.5 mm was present in 1624 patients (28.2%) before light stimulus; 645 of these patients (39.7%) also had anisocoria after light stimulus (P < .001). Anisocoria defined as pupil size difference of greater than 2.0 mm was present in 79 patients (1.4%) before light stimulus; 42 of these patients (53.2%) also had anisocoria after light stimulus (P < .001).

DISCUSSION

The finding of anisocoria significantly differed before and after light stimulus and according to the cut point used. At most cut points, fewer than half of the patients who had anisocoria before light stimulus also had anisocoria after light stimulus.

CONCLUSION

The profound difference in the number of patients adjudicated as having anisocoria using different cut points reinforces the need to develop a universal definition for anisocoria.

Pupillary monitoring decreases remifentanil consumption during laparoscopic uterine surgery and improves postoperative recovery

BACKGROUND

The aim of this paper was to explore pupillary monitoring for determining remifentanil consumption during general anesthesia and evaluating postoperative recovery quality.

METHODS

Eighty patients undergoing elective laparoscopic uterine surgery were randomly divided into pupillary monitoring group (Group P) and control group (Group C). In Group P, remifentanil dosage during general anesthesia was determined according to pupil dilation reflex; in Group C, it was adjusted according to hemodynamic changes. Intraoperative remifentanil consumption and endotracheal tube extraction time were recorded. The Numerical Rating Scale (NRS) Score, hemodynamic changes, and opioid-related adverse reactions in the post-anesthesia care unit were also recorded. The parameters of pupil light reflex from extubation to 30 min after extubation were analyzed in Group P, and the responsiveness of these parameters and hemodynamic changes to NRS was determined by ROC curve analyses.

RESULTS

Compared with Group C, in Group P, intraoperative remifentanil consumption, the NRS Score at 20 minutes after extubation, extubation time, and the incidence of nausea, vomiting, and respiratory amnesia were all significantly decreased (all, P<0.05). In Group P, ∆HR and ∆MAP had no value in judging the change of NRS. The ROC values and diagnostic cutoff values of ΔInit, ΔACV, and ΔMCV responding to NRS variation were 0.775 (95% CI: 0.582-0.968), 0.734(95% CI: 0.537-0.930), and 0.822 (95% CI: 0.648-0.997) and 0.21 (sensitivity, 92.3%; specificity, 23.1%), -1.3 (sensitivity, 92.3%; specificity, 18.3%), and -1.0 (sensitivity, 84.6%; specificity, 17.7%), respectively.

CONCLUSIONS

Intraoperative pupil dilation reflex monitoring can reduce remifentanil consumption and improve postoperative recovery quality. Furthermore, postoperative pupil light reflex monitoring can help evaluate pain degree with high sensitivity.

Neurological Pupillary Index (NPi) Measurement Using Pupillometry and Outcomes in Critically Ill Children

Aim/objective Neurological Pupil Index (NPi), measured by automated pupillometry (AP), allows the objective assessment of pupillary light reflex (PLR). NPi ranges from 0 (non-reactive) to 5 (normal). In this study, we aimed to compare neurologic and functional outcomes in children admitted for neurologic injury with normal (≥3) versus abnormal (<3) NPi measured during their pediatric intensive care unit (PICU) stay. Materials and methods We conducted a retrospective chart review of children between one month and 18 years admitted to our PICU with a diagnosis of neurologic injury between January 2019 and June 2022. We collected demographic, clinical, pupillometer, and outcome data, including mortality, Pediatric Cerebral Performance Category (PCPC), Pediatric Overall Performance Category (POPC), and Functional Status Score (FSS) at admission, at discharge, and at the three to six-month follow-up. We defined abnormal pupil response as any NPi <3 at any point during the PICU stay. Using the student's t-test and chi-square test, we compared the short-term and long-term outcomes of children with abnormal NPi (<3) versus those with normal NPi (≥3). Results There were 49 children who met the inclusion criteria and who had pupillometry data available for analysis. The mean (SD) Glasgow Coma Scale (GCS) in the study cohort was 5.6 (4.3), and 61% had low (<3) NPi during ICU stay. Mortality was significantly higher among patients with an abnormal NPi as compared to those with normal NPi. Children with abnormal NPi exhibited significant worsening of neurologic and functional status (ΔPCPC, ΔPOPC, and ΔFSS) from admission to discharge (mean (SD): 3.55(1.5), 3.45(1.43), 16.75(7.85), p<0.001) as compared to those with normal NPi (mean (SD): 1.45(0.93), 1.73(0.90), 3.55(2.07), p>0.05). The significant difference in neurologic and functional status persisted at the three to six-month follow-up between the two groups - children with abnormal NPi (mean (SD): 2.0(1.41), 2.08(1.38), 6.92(6.83), p<0.01) and children with normal NPi (mean (SD): 0.82(1.01), 0.94(1.03), 1.53(1.70), p>0.05). Conclusion In our retrospective cohort study, children admitted to the PICU for a neuro injury and with abnormal NPi (< 3) have higher mortality, and worse short-term and long-term neurologic and functional outcomes as compared to those with normal NPi (≥ 3) measured during the PICU course. AP provides an objective assessment of PLR and has potential applications for neuro-prognostication. More research needs to be done to elucidate the prognostic value of NPi in pediatrics.

Validation of a Smartphone Pupillometry Application in Diagnosing Severe Traumatic Brain Injury

The pupillary light reflex (PLR) is an important biomarker for the detection and management of traumatic brain injury (TBI). We investigated the performance of PupilScreen, a smartphone-based pupillometry app, in classifying healthy control subjects and subjects with severe TBI in comparison to the current gold standard NeurOptics pupillometer (NPi-200 model with proprietary Neurological Pupil Index [NPi] TBI severity score). A total of 230 PLR video recordings taken using both the PupilScreen smartphone pupillometer and NeurOptics handheld device (NPi-200) pupillometer were collected from 33 subjects with severe TBI (sTBI) and 132 subjects who were healthy without self-reported neurological disease. Severe TBI status was determined by Glasgow Coma Scale (GCS) at the time of recording. The proprietary NPi score was collected from the NPi-200 pupillometer for each subject. Seven PLR curve morphological parameters were collected from the PupilScreen app for each subject. A comparison via t-test and via binary classification algorithm performance using NPi scores from the NPi-200 and PLR parameter data from the PupilScreen app was completed. This was used to determine how the frequently used NPi-200 proprietary NPi TBI severity score compares to the PupilScreen app in ability to distinguish between healthy and sTBI subjects. Binary classification models for this task were trained for the diagnosis of healthy or severe TBI using logistic regression, k-nearest neighbors, support vector machine, and random forest machine learning classification models. Overall classification accuracy, sensitivity, specificity, area under the curve, and F1 score values were calculated. Median GCS was 15 for the healthy cohort and 6 (interquartile range 2) for the severe TBI cohort. Smartphone app PLR parameters as well as NPi from the digital infrared pupillometer were significantly different between healthy and severe TBI cohorts; 33% of the study cohort had dark eye colors defined as brown eyes of varying shades. Across all classification models, the top performing PLR parameter combination for classifying subjects as healthy or sTBI for PupilScreen was maximum diameter, constriction velocity, maximum constriction velocity, and dilation velocity with accuracy, sensitivity, specificity, area under the curve (AUC), and F1 score of 87%, 85.9%, 88%, 0.869, and 0.85, respectively, in a random forest model. The proprietary NPi TBI severity score demonstrated greatest AUC value, F1 score, and sensitivity of 0.648, 0.567, and 50.9% respectively using a random forest classifier and greatest overall accuracy and specificity of 67.4% and 92.4% using a logistic regression model in the same classification task on the same dataset. The PupilScreen smartphone pupillometry app demonstrated binary healthy versus severe TBI classification ability greater than that of the NPi-200 proprietary NPi TBI severity score. These results may indicate the potential benefit of future study of this PupilScreen smartphone pupillometry application in comparison to the NPi-200 digital infrared pupillometer across the broader TBI spectrum, as well as in other neurological diseases.

Intraoperative neurological pupil index and postoperative delirium and neurologic adverse events after cardiac surgery: an observational study

Neurological pupil index (NPi) calculated by automated pupillometry predicts clinical outcomes in critically ill patients. However, there are few data on intraoperative NPi and postoperative outcome after cardiac surgery. We evaluated the relationships between intraoperative NPi and clinical outcomes, such as delirium, in cardiac surgery patients. NPi was measured at baseline, after anesthesia induction, at 30 min intervals after initiation of cardiopulmonary bypass or anastomosis of coronary artery bypass graft, and at skin closure. Abnormal NPi was defined as one or more measurements of NPi < 3.0 during surgery. The worst intraoperative NPi was recorded, then multivariate logistic regression analysis was performed to evaluate the relationship between abnormal NPi and postoperative delirium following cardiac surgery. Among 123 included patients, postoperative delirium developed in 19.5% (24/123) of patients. Intraoperative abnormal NPi was significantly associated with postoperative delirium (odds ratio 6.078; 95% confidence interval 1.845-20.025; P = 0.003) after adjustment for Society of Thoracic Surgeons Predicted Risk of Mortality score, coronary artery disease, and use of calcium channel blockers. In conclusion, abnormal intraoperative NPi independently predicted postoperative delirium following cardiac surgery. Intraoperative application of pupillometry may have prognostic value for development of postoperative delirium, thereby enabling close surveillance and early intervention in high-risk patients.Registry number: ClinicalTrials.gov (NCT04136210).

Prognostic predictors in patients with cardiopulmonary arrest: A novel equation for evaluating the 30-day mortality

BACKGROUND

Early prediction of outcomes after cardiopulmonary arrest (CPA) is important for considering the best support. Our purpose was to evaluate predictors of the 30-day mortality in patients with CPA after return of spontaneous circulation (ROSC) and to assess an equation for calculating the 30-day mortality using clinical parameters.

METHODS

We retrospectively analyzed the data of 194 consecutive patients with CPA and ROSC in a derivation study (2015-2022). We compared clinical parameters between the survived (n = 78) and dead (n = 116) patients. We derived an equation for estimated probability of death based on clinical parameters, using multivariate logistic regression analysis. The reliability of the equation was validated in 80 additional patients with CPA.

RESULTS

The 30-day mortality was associated with sex, witnessed cardiac arrest, bystander cardiopulmonary resuscitation (CPR), CPA due to acute myocardial infarction, pupil diameter, Glasgow Coma Scale score (GCS), presence of light reflex, arterial or venous pH, lactate levels, initial ventricular fibrillation (VF), CPA time, and age. The derived logistic regression equation was as follows: Estimated probability of death = 1 / (1 + e-x), x = (0.25 × bystander CPR) + (0.44 × pupil diameter) - (0.14 × GCS) + (0.09 × lactate) - (1.87 × initial VF) + (0.07 × CPA time) + (0.05 × age) - 7.03. The cut-off value for estimated probability of death calculated by this equation was 54.5 %, yielding a sensitivity, specificity, and accuracy of 86.2 %, 80.8 %, and 84.5 %, respectively. In the validation model, these values were 81.8 %, 85.7 %, and 82.5 %, respectively.

CONCLUSIONS

The 30-day mortality may be calculated after ROSC in patients with CPA using simple clinical parameters. This equation may facilitate further best support for patients with CPA.

Prognosis of Cardiac Arrest-Peri-arrest and Post-arrest Considerations

There has been only a small improvement in survival and neurologic outcomes in patients with cardiac arrest in recent decades. Type of arrest, length of total arrest time, and location of arrest alter the trajectory of survival and neurologic outcome. In the post-arrest phase, clinical markers such as blood markers, pupillary light response, corneal reflex, myoclonic jerking, somatosensory evoked potential, and electroencephalography testing can be used to help guide neurological prognostication. Most of the testing should be performed 72 hours post-arrest with special considerations for longer observation periods in patients who underwent TTM or who had prolonged sedation and/or neuromuscular blockade.

Application of Pupillometry in Neurocritical Patients

Pupillary light reflex (PLR) assessment is a crucial examination for evaluating brainstem function, particularly in patients with acute brain injury and neurosurgical conditions. The PLR is controlled by neural pathways modulated by both the sympathetic and parasympathetic nervous systems. Altered PLR is a strong predictor of adverse outcomes after traumatic and ischemic brain injuries. However, the assessment of PLR needs to take many factors into account since it can be modulated by various medications, alcohol consumption, and neurodegenerative diseases. The development of devices capable of measuring pupil size and assessing PLR quantitatively has revolutionized the non-invasive neurological examination. Automated pupillometry, which is more accurate and precise, is widely used in diverse clinical situations. This review presents our current understanding of the anatomical and physiological basis of the PLR and the application of automated pupillometry in managing neurocritical patients. We also discuss new technologies that are being developed, such as smartphone-based pupillometry devices, which are particularly beneficial in low-resource settings.

Detection of Relative Afferent Pupillary Defect and Its Correlation with Structural and Functional Asymmetry in Patients with Glaucoma Using Hitomiru, a Novel Hand-Held Pupillometer

Patients with asymmetric glaucomatous optic neuropathy (GON) present a relative afferent pupillary defect (RAPD) in the eye with more advanced damage. Although useful, pupillometric RAPD quantification is not widely used as it is not portable. Whether asymmetry of the peripapillary capillary perfusion density (CPD) detected using optical coherence tomography angiography correlates with the severity of RAPD remains unknown. This study assessed RAPD in 81 patients with GON using Hitomiru, a novel hand-held infrared binocular pupillometer. The correlation and ability to detect clinical RAPD based on the swinging flash light test of two independent RAPD parameters (the maximum pupil constriction ratio and the constriction maintenance capacity ratio) were assessed. The coefficient of determination (R²) was calculated between each of the two RAPD parameters and asymmetry of the circumpapillary retinal nerve fiber layer thickness (cpRNFLT), ganglion cell layer/inner plexiform layer thickness (GCL/IPLT), and CPD. The two RAPD parameters showed a correlation coefficient of 0.86 and areas under the receiver operating characteristic (ROC) curve of 0.85-0.88, with R² being 0.63-0.67 for the visual field, 0.35-0.45 for cpRNFLT, 0.45-0.49 for GCL/IPLT, and 0.53-0.59 for CPD asymmetry. Hitomiru has high discriminatory performance in detecting RAPD in patients with asymmetric GON. CPD asymmetry may better correlate with RAPD than cpRNFLT and GCL/IPLT asymmetry.

Guidelines for Neuroprognostication in Comatose Adult Survivors of Cardiac Arrest

BACKGROUND

Among cardiac arrest survivors, about half remain comatose 72 h following return of spontaneous circulation (ROSC). Prognostication of poor neurological outcome in this population may result in withdrawal of life-sustaining therapy and death. The objective of this article is to provide recommendations on the reliability of select clinical predictors that serve as the basis of neuroprognostication and provide guidance to clinicians counseling surrogates of comatose cardiac arrest survivors.

METHODS

A narrative systematic review was completed using Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. Candidate predictors, which included clinical variables and prediction models, were selected based on clinical relevance and the presence of an appropriate body of evidence. The Population, Intervention, Comparator, Outcome, Timing, Setting (PICOTS) question was framed as follows: "When counseling surrogates of comatose adult survivors of cardiac arrest, should [predictor, with time of assessment if appropriate] be considered a reliable predictor of poor functional outcome assessed at 3 months or later?" Additional full-text screening criteria were used to exclude small and lower-quality studies. Following construction of the evidence profile and summary of findings, recommendations were based on four GRADE criteria: quality of evidence, balance of desirable and undesirable consequences, values and preferences, and resource use. In addition, good practice recommendations addressed essential principles of neuroprognostication that could not be framed in PICOTS format.

RESULTS

Eleven candidate clinical variables and three prediction models were selected based on clinical relevance and the presence of an appropriate body of literature. A total of 72 articles met our eligibility criteria to guide recommendations. Good practice recommendations include waiting 72 h following ROSC/rewarming prior to neuroprognostication, avoiding sedation or other confounders, the use of multimodal assessment, and an extended period of observation for awakening in patients with an indeterminate prognosis, if consistent with goals of care. The bilateral absence of pupillary light response > 72 h from ROSC and the bilateral absence of N20 response on somatosensory evoked potential testing were identified as reliable predictors. Computed tomography or magnetic resonance imaging of the brain > 48 h from ROSC and electroencephalography > 72 h from ROSC were identified as moderately reliable predictors.

CONCLUSIONS

These guidelines provide recommendations on the reliability of predictors of poor outcome in the context of counseling surrogates of comatose survivors of cardiac arrest and suggest broad principles of neuroprognostication. Few predictors were considered reliable or moderately reliable based on the available body of evidence.

Prognosis of consciousness disorders in the intensive care unit

Assessments of consciousness are a critical part of prognostic algorithms for critically ill patients suffering from severe brain injuries. There have been significant advances in the field of coma science over the past two decades, providing clinicians with more advanced and precise tools for diagnosing and prognosticating disorders of consciousness (DoC). Advanced neuroimaging and electrophysiological techniques have vastly expanded our understanding of the biological mechanisms underlying consciousness, and have helped identify new states of consciousness. One of these, termed cognitive motor dissociation, can predict functional recovery at 1 year post brain injury, and is present in up to 15-20% of patients with DoC. In this chapter, we review several tools that are used to predict DoC, describing their strengths and limitations, from the neurological examination to advanced imaging and electrophysiologic techniques. We also describe multimodal assessment paradigms that can be used to identify covert consciousness and thus help recognize patients with the potential for future recovery and improve our prognostication practices.

Specific thresholds of quantitative pupillometry parameters predict unfavorable outcome in comatose survivors early after cardiac arrest

Aim

Quantitative pupillometry is the guideline-recommended method for assessing pupillary light reflex for multimodal prognostication in comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA). However, threshold values predicting an unfavorable outcome have been inconsistent across studies; therefore, we aimed to identify specific thresholds for all quantitative pupillometry parameters.

Methods

Comatose post-OHCA patients were consecutively admitted to the cardiac arrest center at Copenhagen University Hospital Rigshospitalet from April 2015 to June 2017. The parameters of quantitatively assessed pupillary light reflex (qPLR), Neurological Pupil index (NPi), average/max constriction velocity (CV/MCV), dilation velocity (DV), and latency of constriction (Lat) were recorded on the first three days after admission. We evaluated the prognostic performance and identified thresholds achieving zero percent false positive rate (0% PFR) for an unfavorable outcome of 90-day Cerebral Performance Category (CPC) 3-5. Treating physicians were blinded for pupillometry results.

Results

Of the 135 post-OHCA patients, the primary outcome occurred for 53 (39%) patients.On any day during hospitalization, a qPLR < 4%, NPi < 2.45, CV < 0.1 mm/s, and an MCV < 0.335 mm/s predicted 90-day unfavorable neurological outcome with 0% FPR (95%CI: 0-0%), with sensitivities of 28% (17-40%), 9% (2-19%), 13% (6-23%), and 17% (8-26%), respectively on day 1.

Conclusion

We found that specific thresholds of all quantitative pupillometry parameters, measured at any time following hospital admission until day 3, predicted a 90-day unfavorable outcome with 0% FPR in comatose patients resuscitated from OHCA. However, at 0% FPR, thresholds resulted in low sensitivity. These findings should be further validated in larger multicenter clinical trials.

"The eyes are the windows of the soul": Portable automated pupillometry to monitor autonomic nervous activity in CO2 narcosis: A case report

RATIONALE

Altered autonomic responses can be observed in patients in the intensive care unit (ICU), and these changes in abnormal autonomic responses are known to be associated with patient prognosis. Therefore, it is important to monitor autonomic nervous system activity in these critically ill patients. While the utility of monitoring critically ill patients using heart rate (HR) variability measurements has been reported, portable automated pupillometers are small, lightweight, and easy-to-operate medical devices that may be more easily evaluated for autonomic nervous system function.

PATIENT CONCERNS

An unconscious 80-year-old female patient with chronic obstructive pulmonary disease was brought to the medical emergency department after a call from her caregiver.

DIAGNOSIS

On arrival, the patient's Glasgow coma scale score was 7, her blood pressure was 140/80 mm Hg, her HR was 114 bpm, and her respiratory rate was 27 breaths/minutes with increased breathing effort. Oxygen saturation was 90% on a venturi mask (3 L of supplemental oxygen). The arterial blood gas analysis showed a pH of 7.196, a partial pressure of carbon dioxide (CO2) of 89.6 mm Hg, a partial pressure of oxygen of 87.5 mm Hg, and a bicarbonate level of 29.4 mmol/L. Other than CO2 narcosis, there were no abnormal findings to induce impaired consciousness. The patient did not respond to support with a bag-valve mask and was intubated. One hour after intubation, her impaired consciousness improved. The patient was extubated 20 hours later and discharged on Day 3.

INTERVENTIONS

The patient was admitted to the ICU after being intubated, where vital signs and blood gas analysis were monitored every 2 hours, and consciousness was assessed using the Glasgow coma scale. Using a portable automated pupillometer (NeurOptics NPi™-200, Neuroptics Inc., Irvine, CA), pupillary responses, including pupil size or light reflex, were measured every 2 hours during ICU stay.

OUTCOMES

Changes in respiratory rate and partial pressure of CO2 values correlated with pupil size and constriction velocity, but HR changes were contrary.

LESSONS

Pupillary responses exhibited by automated pupillometers observed in patients with CO2 narcosis may be linked to vital signs and allow for autonomic evaluation.

Automated pupillometry in space neuroscience

Modern pupillometers are automated, thereby providing an objective, accurate, and reliable evaluation of various aspects of the pupillary light reflex at precision levels that were previously unobtainable. There are many gaps in knowledge regarding pupil size and pupillary light reflex in nervous system changes related to space travel given the previous lack of a precise method to quantitatively measure it. Automated pupillometry has not been used previously in space. This novel tool has promising uses in altered gravity environments as a sensitive non-invasive tool to determine alterations due to headward fluid shifts and elevated intracranial pressure. This article discusses the potential use of automated pupillometry in space for monitoring of astronaut health and neurological pathology.

Neuromonitoring in Critically Ill Patients

OBJECTIVES

Critically ill patients are at high risk of acute brain injury. Bedside multimodality neuromonitoring techniques can provide a direct assessment of physiologic interactions between systemic derangements and intracranial processes and offer the potential for early detection of neurologic deterioration before clinically manifest signs occur. Neuromonitoring provides measurable parameters of new or evolving brain injury that can be used as a target for investigating various therapeutic interventions, monitoring treatment responses, and testing clinical paradigms that could reduce secondary brain injury and improve clinical outcomes. Further investigations may also reveal neuromonitoring markers that can assist in neuroprognostication. We provide an up-to-date summary of clinical applications, risks, benefits, and challenges of various invasive and noninvasive neuromonitoring modalities.

DATA SOURCES

English articles were retrieved using pertinent search terms related to invasive and noninvasive neuromonitoring techniques in PubMed and CINAHL.

STUDY SELECTION

Original research, review articles, commentaries, and guidelines.

DATA EXTRACTION

Syntheses of data retrieved from relevant publications are summarized into a narrative review.

DATA SYNTHESIS

A cascade of cerebral and systemic pathophysiological processes can compound neuronal damage in critically ill patients. Numerous neuromonitoring modalities and their clinical applications have been investigated in critically ill patients that monitor a range of neurologic physiologic processes, including clinical neurologic assessments, electrophysiology tests, cerebral blood flow, substrate delivery, substrate utilization, and cellular metabolism. Most studies in neuromonitoring have focused on traumatic brain injury, with a paucity of data on other clinical types of acute brain injury. We provide a concise summary of the most commonly used invasive and noninvasive neuromonitoring techniques, their associated risks, their bedside clinical application, and the implications of common findings to guide evaluation and management of critically ill patients.

CONCLUSIONS

Neuromonitoring techniques provide an essential tool to facilitate early detection and treatment of acute brain injury in critical care. Awareness of the nuances of their use and clinical applications can empower the intensive care team with tools to potentially reduce the burden of neurologic morbidity in critically ill patients.

Use of pupillometry for the evaluation of analgesia in dogs hospitalized in intensive care: A prospective study

A prospective study was performed on hospitalized conscious dogs. The objectives were: 1) to evaluate the feasibility and reliability of portable infrared pupillometry using a measure of photo light reflexes, 2) to identify parameters influencing measures, and 3) to compare parameters before and after the administration of analgesia. Twenty-nine dogs were included. Pupillometry was feasible by a single person. There was an excellent reliability for the evaluation of pupil diameter. There was poor to good reliability for the other parameters. There was an association between weight and mean pupil diameter (estimate = 0.1 mm, CI95 = [0.0; 0.1], P = 0.02), mean diameter variation (estimate = 0.2%, CI95 = [0.0; 0.4], P = 0.01), and mean velocity (estimate = 0.08 ms, CI95 = [0.03; 0.13], P = 0.002). Male dogs had a significantly larger mean pupil diameter than females (estimate = 1.3 mm, CI95 = [0.1; 2.5], P = 0.03). Independently of weight and sex, there was an association between mean pupil diameter and pain score: the higher the pain score, the lower the mean pupil diameter. There was a correlation between mean pupil diameter and morphine dose (ρ = -0.78, P = 0.0004). There was no significant difference in pupil diameter, velocity, and latency before and after analgesic administration. In conclusion, results do not support the use of PLR measurement by pupillometry as a pain assessment technique in hospitalized conscious dogs.

Multimodal Neuromonitoring in Pediatric Neurocritical Care: Current Perspectives

Children with neurological illness in the critical care unit are always at higher risk of developing secondary brain injury (SBI). Brain insult can lead to changes in cerebral autoregulation, intracranial pressure (ICP), cerebral oxygenation, and metabolism. This can cause a raised ICP, cerebral ischemia, hypoxia, excitotoxicity, cellular energy failure, and nonconvulsive status epilepticus. Simultaneous and continuous assessment of these parameters will help to improve patient care and neurological outcomes. Even though clinical examination and neuroimaging can help in the initial diagnosis of the neurological illness, they may not be helpful in continuous monitoring of cerebral pathophysiological changes. The ideal single neuromonitoring device to detect these real-time changes is currently unavailable. However, a range of invasive and noninvasive monitors are available to monitor these cerebral functional parameters. Invasive monitoring techniques include invasive ICP monitoring, cerebral autoregulation monitoring, brain tissue partial oxygen pressure, and cerebral microdialysis. Noninvasive-monitoring techniques include pupillometry, brain and ocular ultrasonography, near-infrared spectroscopy, and electrophysiological monitoring. Multimodal (MM) neuromonitoring involves incorporating these techniques and tools for the early identification and treatment of primary and secondary brain insults. The utility and feasibility of most of these techniques are well described in adult neurocritical care. Even though the evidence on their usage in children is primarily available in pediatric traumatic brain injury, the emerging data help to further expand their utility in pediatric nontraumatic coma. MM neuromonitoring aims to provide clinical and pathophysiological information to the intensivists to improve their understanding of the child's neurological status and to formulate patient-specific treatment approaches.

Associations of an eye-tracking task and pupillary metrics with age and ASA physical status score in a preoperative cohort

Advanced age, American Society of Anesthesiologists physical status (ASA) classification and the presence of cognitive impairment are associated with an elevated risk of postoperative morbidity and mortality. The visual paired comparison (VPC) task, which relies on recognition of novel images, examines declarative memory. VPC scores have demonstrated the ability to detect mild cognitive impairment and track progression of neurodegenerative disease. Quantitative pupillometry may have similar value. We evaluate for associations between these variables of interest and the feasibility of performing these tests in the preoperative clinic. Prospective data from 199 patients seen in the preoperative clinic at a tertiary academic center were analyzed. A 5 min VPC task (Neurotrack Technologies, Inc, Redwood City, CA) was administered during their scheduled preoperative clinic visit. Pupillary light reflexes were measured at the same visit (PLR-3000™, Neuroptics Corp, Irvine, California).Thirty-four percent of patients were categorized as ASA 2 and 58% as ASA 3. Median age was 57 (IQR: 44-69). Associations were demonstrated between age and ASA physical status (Mann-Whitney U Test, p < 0.0001), maximum pupil size (Spearman Rank Correlation, r = - 0.40, p < 0.0001), and maximum constriction velocity (Spearman Rank Correlation, r = - 0.39, p < 0.0001). Our data also revealed an association between VPC score and age (Spearman Rank Correlation, p = 0.0016, r = - 0.21) but not ASA score (Kruskal-Wallis Test, p = 0.14). When compared to a nonsurgical cohort with no history of memory impairment, our population scored worse on the VPC task (Mann-Whitney U Test, p = 0.0002). A preoperative 5 min VPC task and pupillometry are feasible tests in the preoperative setting and may provide a valuable window into an individual's cognition prior to elective surgery.

Quantitative pupillary light reflex assessment for prognosis of carbon monoxide poisoning

Background

A non-reactive pupil in standard pupillary light reflex (sPLR) is regarded as a factor predicting neurological sequelae at 1-month after carbon monoxide (CO) poisoning. An automated pupillometer is used in the intensive care unit to quantitatively assess PLR. Quantitative PLR (qPLR) was superior to sPLR using penlight for prognosis of various neurological diseases. Therefore, this study aimed to analyze whether quantitative pupillary variables (neurological Pupil index [NPi] and qPLR) are superior to sPLR in predicting 1-month neurocognitive sequelae after acute CO poisoning.

Methods

We performed a prospective observational study of consecutive patients with acute CO poisoning admitted to an emergency department (ED) between August 2019 and December 2020 in a single academic medical center. sPLR and pupillometer examinations (qPLR and NPi) were performed by emergency physicians at the ED on hospital days 0-2. The lowest values among those recorded within 24 h and during the total measurement period were considered the 24-h and total lowest values, respectively. Global Deterioration Scale scores were measured at 1 month as an outcome and were dichotomized into favorable (1-4) or poor (5-7) outcomes.

Results

We analyzed the data of 104 adult patients with acute CO poisoning. qPLR was significantly higher in the favorable outcome group than in the poor outcome group 24-h and total lowest values (21.2% vs. 15.0%, p = 0.006 and 21.0% vs. 14.8%, p = 0.006). qPLR <18% had fair predictive power for poor neurocognitive outcomes [area under the curve (AUC), 0.70; 95% confidence interval (0.60-0.78)]. Among the patients with decreased mental status (Glasgow Coma Scale ≤12), the power of NPi and qPLR increased [AUC, 0.72 and AUC, 0.80]. NPi < 1 and qPLR <18% showed sensitivity (9.5% vs. 76.2%) and specificity (98.8% vs. 67.5%) for the prediction of poor outcomes. qPLR was significantly superior to sPLR in predicting poor neurocognitive outcomes at 1 month after CO poisoning (p = 0.007).

Conclusion

qPLR and NPi were superior to sPLR in terms of predicting poor neurocognitive outcomes. qPLR and NPi measured from hospital days 0-2 may be valuable in predicting neurocognitive outcome.

Vision-Based Eye Image Classification for Ophthalmic Measurement Systems

The accuracy and the overall performances of ophthalmic instrumentation, where specific analysis of eye images is involved, can be negatively influenced by invalid or incorrect frames acquired during everyday measurements of unaware or non-collaborative human patients and non-technical operators. Therefore, in this paper, we investigate and compare the adoption of several vision-based classification algorithms belonging to different fields, i.e., Machine Learning, Deep Learning, and Expert Systems, in order to improve the performance of an ophthalmic instrument designed for the Pupillary Light Reflex measurement. To test the implemented solutions, we collected and publicly released PopEYE as one of the first datasets consisting of 15 k eye images belonging to 22 different subjects acquired through the aforementioned specialized ophthalmic device. Finally, we discuss the experimental results in terms of classification accuracy of the eye status, as well as computational load analysis, since the proposed solution is designed to be implemented in embedded boards, which have limited hardware resources in computational power and memory size.

Can Quantitative Pupillometry be used to Screen for Elevated Intracranial Pressure? A Retrospective Cohort Study

BACKGROUND

Elevated intracranial pressure (ICP) is a serious complication in brain injury. Because of the risks involved, ICP is not monitored in all patients at risk. Noninvasive screening tools to identify patients with elevated ICP are needed. Anisocoria, abnormal pupillary size, and abnormal pupillary light reflex are signs of high ICP, but manual pupillometry is arbitrary and subject to interrater variability. We have evaluated quantitative pupillometry as a screening tool for elevated ICP.

METHODS

We performed a retrospective observational study of the association between Neurological Pupil index (NPi), measured with the Neuroptics NPi-200 pupillometer, and ICP in patients routinely monitored with invasive ICP measurement in the intensive care unit. We performed a nonparametric receiver operator curve analysis for ICP ≥ 20 mm Hg with NPi as a classification variable. We performed a Youden analysis for the optimal NPi cutoff value and recorded sensitivity and specificity for this cutoff value. We also performed a logistic regression with elevated ICP as the dependent variable and NPi as the independent variable.

RESULTS

We included 65 patients with invasive ICP monitoring. A total of 2,705 measurements were analyzed. Using NPi as a screening tool for elevated ICP yielded an area under receiver operator curve of 0.72. The optimal mean NPi cutoff value to rule out elevated ICP was ≥ 3.9. The probability of elevated ICP decreased with increasing NPi, with an odds ratio of 0.55 (0.50, 0.61).

CONCLUSIONS

Screening with NPi may inform high stakes clinical decisions by ruling out elevated ICP with a high degree of certainty. It may also aid in estimating probabilities of elevated ICP. This can help to weigh the risks of initiating invasive ICP monitoring against the risks of not doing so. Because of its ease of use and excellent interrater reliability, we suggest further studies of NPi as a screening tool for elevated ICP.

Superior reproducibility and repeatability in automated quantitative pupillometry compared to standard manual assessment, and quantitative pupillary response parameters present high reliability in critically ill cardiac patients

Background

Quantitative pupillometry is part of multimodal neuroprognostication of comatose patients after out-of-hospital cardiac arrest (OHCA). However, the reproducibility, repeatability, and reliability of quantitative pupillometry in this setting have not been investigated.

Methods

In a prospective blinded validation study, we compared manual and quantitative measurements of pupil size. Observer and device variability for all available parameters are expressed as mean difference (bias), limits of agreement (LoA), and reliability expressed as intraclass correlation coefficients (ICC) with a 95% confidence interval.

Results

Fifty-six unique quadrupled sets of measurement derived from 14 sedated and comatose patients (mean age 70±12 years) were included.

For manually measured pupil size, inter-observer bias was -0.14±0.44 mm, LoA of -1.00 to 0.71 mm, and ICC at 0.92 (0.86–0.95). For quantitative pupillometry, we found bias at 0.03±0.17 mm, LoA of -0.31 to 0.36 mm and ICCs at 0.99. Quantitative pupillometry also yielded lower bias and LoA and higher ICC for intra-observer and inter-device measurements.

Correlation between manual and automated pupillometry was better in larger pupils, and quantitative pupillometry had less variability and higher ICC, when assessing small pupils. Further, observers failed to detect 26% of the quantitatively estimated abnormal reactivity with manual assessment.

We found ICC >0.91 for all quantitative pupillary response parameters (except for latency with ICC 0.81–0.91).

Conclusion

Automated quantitative pupillometry has excellent reliability and twice the reproducibility and repeatability than manual pupillometry. This study further presents novel estimates of variability for all quantitative pupillary response parameters with excellent reliability.

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

Impaired cerebral autoregulation (CA) may increase the risk of brain hypoperfusion in septic patients. Sepsis dysregulates the autonomic nervous system (ANS), potentially affecting CA. ANS function can be assessed through the pupillary light reflex (PLR). The aim of this prospective, observational study was to investigate the association between CA and PLR in adult septic patients. Transcranial Doppler was used to assess CA and calculate estimated cerebral perfusion pressure (eCPP) and intracranial pressure (eICP). An automated pupillometer (AP) was used to record Neurological Pupil Index (NPi), constriction (CV) and dilation (DV) velocities. The primary outcome was the relationship between AP-derived variables with CA; the secondary outcome was the association between AP-derived variables with eCPP and/or eICP. Among 40 included patients, 21 (53%) had impaired CA, 22 (55%) had low eCPP (<60 mmHg) and 15 (38%) had high eICP (>16 mmHg). DV was lower in patients with impaired CA compared to others; DV predicted impaired CA with area under the curve, AUROC= 0.78 [95% Confidence Interval, CI 0.63−0.94]; DV < 2.2 mm/s had sensitivity 85% and specificity 69% for impaired CA. Patients with low eCPP or high eICP had lower NPi values than others. NPi was correlated with eCPP (r = 0.77, p < 0.01) and eICP (r = −0.87, p < 0.01). Automated pupillometry may play a role to assess brain hemodynamics in septic patients.

Mobile Smartphone-Based Digital Pupillometry Curves in the Diagnosis of Traumatic Brain Injury

Objective

The pupillary light reflex (PLR) and the pupillary diameter over time (the PLR curve) is an important biomarker of neurological disease, especially in the diagnosis of traumatic brain injury (TBI). We investigated whether PLR curves generated by a novel smartphone pupillometer application could be easily and accurately interpreted to aid in the diagnosis of TBI.

Methods

A total of 120 PLR curves from 42 healthy subjects and six patients with TBI were generated by PupilScreen. Eleven clinician raters, including one group of physicians and one group of neurocritical care nurses, classified 48 randomly selected normal and abnormal PLR curves without prior training or instruction. Rater accuracy, sensitivity, specificity, and interrater reliability were calculated.

Results

Clinician raters demonstrated 93% accuracy, 94% sensitivity, 92% specificity, 92% positive predictive value, and 93% negative predictive value in identifying normal and abnormal PLR curves. There was high within-group reliability (k = 0.85) and high interrater reliability (K = 0.75).

Conclusion

The PupilScreen smartphone application-based pupillometer produced PLR curves for clinical provider interpretation that led to accurate classification of normal and abnormal PLR data. Interrater reliability was greater than previous studies of manual pupillometry. This technology may be a good alternative to the use of subjective manual penlight pupillometry or digital pupillometry.

Pupillometry in neurocritical care

Though pupillometer use is becoming more widespread, there is a lack of evidence on its use by nurses in the neurosurgical ICU. This article explores the use of the pupillometer among neurocritical care nurses to better understand their experience and the device's clinical utility.