Portable Infrared Pupillometry

Progress in the validation of nociception monitoring in guiding intraoperative analgesic therapy

PURPOSE OF REVIEW

This article summarizes the current level of validation for several nociception monitors using a categorized validation process to facilitate the comparison of performance.

RECENT FINDINGS

Nociception monitors improve the detection of a shift in the nociception and antinociception balance during anesthesia, guiding perioperative analgesic therapy. A clear overview and comparison of the validation process for these monitors is missing.

RESULTS

Within a 2-year time-frame, we identified validation studies for four monitors [analgesia nociception index (ANI), nociception level monitor (NOL), surgical pleth index (SPI), and pupillometry]. We categorized these studies in one out of six mandatory validation steps: developmental studies, clinical validation studies, pharmacological validation studies, clinical utility studies, outcome improvement studies and economical evaluation studies. The current level of validation for most monitors is mainly focused on the first three categories, whereas ANI, NOL, and SPI advanced most in the availability of clinical utility studies and provide confirmation of a clinical outcome improvement. Analysis of economical value for public health effects is not yet publicly available for the studied monitors.

SUMMARY

This review proposes a stepwise structure for validation of new monitoring technology, which facilitates comparison between the level of validation of different devices and identifies the need for future research questions.

Using Pupillometry to Evaluate Balance in Patients Implanted with a Cochleo-Vestibular Implant

Maintaining balance comes naturally to healthy people. In subjects with vestibulopathy, even when compensated, and especially if it is bilateral, maintaining balance requires cognitive effort. Pupillometry is an established method of quantifying cognitive effort. Background/Objectives: We hypothesized that pupillometry would be able to capture the increased effort required to maintain posture in subjects with bilateral vestibulopathy in increasingly difficult conditions. Additionally, we hypothesized that the cognitive workload during balance tasks, indexed by pupil size, would decrease with the activation of the BionicVEST cochleo-vestibular implants. Methods: Subjects with a cochleo-vestibular implant as of March 2023 were recruited, excluding those with ophthalmological issues that precluded pupillometry. Pupillometry was performed using a validated modified videonystagmography system. Computed dynamic posturography and a Modified Clinical Test of Sensory Integration on Balance were performed while the pupil was recorded. Tests were first performed after 24 h of deactivating the vestibular component of the implant. Thereafter, it was reactivated, and after 1 h of rest, the tests were repeated. The pupil recording was processed using custom software and the mean relative pupil diameter (MRPD) was calculated. Results: There was an average of 10.7% to 24.2% reduction in MRPD when the vestibular implant was active, with a greater effect seen in tasks of moderate difficulty, and lesser effect when the task was easy or of great difficulty. Conclusions: Despite technical challenges, pupillometry appears to be a promising method of quantifying the cognitive effort required for maintaining posture in subjects with bilateral vestibulopathy before and after vestibular implantation.

Automated Pupillometry Is Able to Discriminate Patients with Acute Stroke from Healthy Subjects: An Observational, Cross-Sectional Study

BACKGROUND

Automated pupillometry (AP) is a handheld, non-invasive tool that is able to assess pupillary light reflex dynamics and is useful for the detection of intracranial hypertension. Limited evidence is available on acute ischemic stroke (AIS) patients. The primary objective was to evaluate the ability of AP to discriminate AIS patients from healthy subjects (HS). Secondly, we aimed to compute a predictive score for AIS diagnosis based on clinical, demographic, and AP variables.

METHODS

We included 200 consecutive patients admitted to a comprehensive stroke center who underwent AP assessment through NPi-200 (NeurOptics®) within 72 h of stroke onset and 200 HS. The mean values of AP parameters and the absolute differences between the AP parameters of the two eyes were considered in the analyses. Predictors of stroke diagnosis were identified through univariate and multivariate logistic regressions; we then computed a nomogram based on each variable's β coefficient. Finally, we developed a web app capable of displaying the probability of stroke diagnosis based on the predictive algorithm.

RESULTS

A high percentage of pupil constriction (CH, p < 0.001), a low constriction velocity (CV, p = 0.002), and high differences between these two parameters (p = 0.036 and p = 0.004, respectively) were independent predictors of AIS. The highest contribution in the predictive score was provided by CH, the Neurological Pupil Index, CV, and CV absolute difference, disclosing the important role of AP in the discrimination of stroke patients.

CONCLUSIONS

The results of our study suggest that AP parameters, and in particular, those concerning pupillary constriction, may be useful for the early diagnosis of AIS.

Measurements of pupillary unrest using infrared pupillometry fail to detect changes in pain intensity in patients after surgery: a prospective observational study

PURPOSE

The pupil displays chaotic oscillations, also referred to as pupillary unrest in ambient light (PUAL). As pain has previously been shown to increase pupillary unrest, the quantitative assessment of PUAL has been considered a possible tool to identify and quantify pain. Nevertheless, PUAL is affected by various states, such as vigilance, cognitive load, or emotional arousal, independent of pain. Furthermore, systematically applied opioids are known to reduce PUAL, thus potentially limiting its usefulness to detect pain or changes in pain intensity. To test the hypothesis that PUAL can reliably identify changes in pain intensity in a clinical setting, we measured PUAL in patients experiencing substantial pain relief when regional anesthesia interventions were applied after surgery.

METHODS

We conducted an observational study at an academic surgery centre following institutional review board approval. Eighteen patients with unsatisfactory pain control following surgery underwent regional anesthesia procedures to improve pain control. We used infrared pupillometry to assess pupillary unrest before and after the regional block. We then compared the changes in pupillary unrest with the changes in pain scores (numeric rating scale [NRS], range 0-10).

RESULTS

Eighteen patients received epidural anesthesia (n = 14) or peripheral nerve blocks (n = 4), resulting in improvement of mean (standard deviation [SD]) NRS pain scores from 7.2 (1.7) to 1.9 (1.8) (difference in means, -2.2; 95% confidence interval [CI], -6.3 to -4.1; P < 0.001). Nevertheless, pupillary unrest did not change as pain decreased; the mean (SD) PUAL was 0.113 (0.062) before analgesia and 0.112 (0.068) after analgesia (difference in means, -0.001; 95% CI, -0.018 to 0.015; P = 0.88).

CONCLUSION

In this prospective observational study, pupillometric measurements of pupillary unrest did not identify changes in pain intensity in a postoperative, predominantly opioid-exposed patient population. While the sample size was small, the use of measurements of pupillary unrest to detect and quantify pain has to be questioned.

Use of Infrared Thermography and Heart Rate Variability to Evaluate Autonomic Activity in Domestic Animals

Most of the responses present in animals when exposed to stressors are mediated by the autonomic nervous system. The sympathetic nervous system, known as the one responsible for the "fight or flight" reaction, triggers cardiovascular changes such as tachycardia or vasomotor alterations to restore homeostasis. Increase in body temperature in stressed animals also activates peripheral compensatory mechanisms such as cutaneous vasodilation to increase heat exchange. Since changes in skin blood flow influence the amount of heat dissipation, infrared thermography is suggested as a tool that can detect said changes. The present review aims to analyze the application of infrared thermography as a method to assess stress-related autonomic activity, and their association with the cardiovascular and heart rate variability in domestic animals.

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 .

Cortical Zinc Signaling Is Necessary for Changes in Mouse Pupil Diameter That Are Evoked by Background Sounds with Different Contrasts

Luminance-independent changes in pupil diameter (PD) during wakefulness influence and are influenced by neuromodulatory, neuronal, and behavioral responses. However, it is unclear whether changes in neuromodulatory activity in a specific brain area are necessary for the associated changes in PD or whether some different mechanisms cause parallel fluctuations in both PD and neuromodulation. To answer this question, we simultaneously recorded PD and cortical neuronal activity in male and female mice. Namely, we measured PD and neuronal activity during adaptation to sound contrast, which is a well-described adaptation conserved in many species and brain areas. In the primary auditory cortex (A1), increases in the variability of sound level (contrast) induce a decrease in the slope of the neuronal input-output relationship, neuronal gain, which depends on cortical neuromodulatory zinc signaling. We found a previously unknown modulation of PD by changes in background sensory context: high stimulus contrast sounds evoke larger increases in evoked PD compared with low-contrast sounds. To explore whether these changes in evoked PD are controlled by cortical neuromodulatory zinc signaling, we imaged single-cell neural activity in A1, manipulated zinc signaling in the cortex, and assessed PD in the same awake mouse. We found that cortical synaptic zinc signaling is necessary for increases in PD during high-contrast background sounds compared with low-contrast sounds. This finding advances our knowledge about how cortical neuromodulatory activity affects PD changes and thus advances our understanding of the brain states, circuits, and neuromodulatory mechanisms that can be inferred from pupil size fluctuations.

The value of pupillary diameter in evaluating pain perception after awakening in patients undergoing general anesthesia during orthopedic surgery

BACKGROUND

The pupillary response to tetanic electrical stimulation reflects the balance between nociceptive stimulation and analgesia. Although pupillary pain index (PPI) was utilized to predict postoperative pain, it depended on tetanic stimulation and was complex. We aim to describe the potential relationship between PD in the presence of surgical stimulation and pain levels after awakening.

METHODS

According to the Verbal Rating Scale (VRS) score after extubation, the patients were divided into painless group (VRS = 0) and pain group (VRS ≥ 1). Pupillary diameter (PD) and pupillary light reflex velocity (PLRV) were compared between two groups when patients entered the operating room (T1), before incision (T2), 10 s after incision (T3), 30 s after incision (T4), 1 h after incision (T5), at the end of surgery (T6), shortly after extubation (T7), and when patients expressed pain clearly (T8). The magnitude of PD change (ΔPD) compared to the baseline value after anesthesia induction (T2) was calculated. The correlations between pupillary parameters and pain after awakening were calculated.

RESULTS

Patients with VRS ≥ 1 had greater PD than painless patients at T3-7 (P = 0.04, 0.04, 0.003, <0.001, <0.001), and it was positively correlated with VRS score after awakening at T4-7 (r = 0.188, 0.217, 0.684, 0.721). The ability of T6ΔPD to predict VRS ≥ 1 was strong [threshold: 20.53%, area under the curve (AUC): 0.93, 95% confidence interval (CI): 0.89-0.97 ].

CONCLUSION

Our study indicates that PD is a useful index to direct the individualized analgesics used during operation, to better avoid the occurrence of pain during the postoperative emergence period.

TRIAL REGISTRATION

This study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR2000040908, registration date: 15/12/2020).

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.

Interdevice Agreement between a Smartphone and a Commercial Pupillometer

Background

The reliability of dynamic pupillometry parameters varies from one pupillometer to another, making it difficult to standardize the values for any particular device. Hence, further studies are required to evaluate the agreement of various pupillometer devices and explore their utility in routine clinical settings.

Aim

This study sought to evaluate the agreement between smartphone and commercial pupillometer measurements in routine clinical settings.

Methods

The study included pupillary measurements obtained by a single investigator from 100 healthy participants (200 eyes) with each pupillometer. Pupillary measurements taken by a smartphone pupillometry application (reflex pupillary light reflex analyzer by Brightlamp [Indianapolis, IN, USA]) were compared with a commercial pupillometer (neurological pupil index-200, NeurOptics Inc., Irvine, USA).

Results

The comparison of descriptive statistics revealed a statistically significant difference between the smartphone and commercial pupillometers for various parameters, including maximum diameter, minimum diameter, constriction velocity (CV), maximum CV, and dilatation velocity (P < 0.05), except for latency (P = 0.36). The intraclass correlation coefficient revealed poor agreement between the two devices (<0.50).

Conclusion

The measurements by smartphone pupillometry application were found to be unreliable, indicating that they may not be an ideal substitute for commercial pupillometers in their present form in the Indian population. Further studies with larger sample size as well as improvements in the processing and interpretation of the measurements by the software, are needed to determine its utility in routine clinical settings.

Postoperative Nausea and Vomiting following Endoscopic Sinus Surgery under the Guidance of Adequacy of Anesthesia or Pupillometry with Intravenous Propofol/Remifentanil

Postoperative nausea and vomiting (PONV) constitutes an adverse event after endoscopic sinus surgery (ESS) under general anesthesia (GA) with intravenous opioids, such as remifentanil (RMF). Monitoring the nociception/antinociception balance using the surgical pleth index (SPI) or pupillary dilatation reflex (PRD) helps guide intravenous RMF infusion. We aimed to investigate whether their employment could help reduce the incidence of PONV in patients undergoing ESS. The data of 30 patients from the GA group, 31 from the SPI group, and 28 from the PRD group were analyzed. The initial RMF infusion rate of 0.25 µg/kg body weight/minute was increased by 50% when the SPI, PRD, or Boezaart Bleeding Scale (BBS) were elevated by >15, >5%, or >2 points, respectively, until they normalized. PONV was present in 7/89 patients (7.9%): 2/31 patients (6.5%) of the SPI group, 1/30 patients (3.3%) of the GA group, and 4/28 patients (14.3%) of the PRD group. Neither PRD nor SPI guidance for RMF administration reduced the incidence of PONV compared to standard practice. Further studies are required in order to investigate the possibility of PONV eradication in patients undergoing ESS under GA when it is possibly combined with paracetamol/metamizole preventive analgesia, as well as those using antiemetic prophylaxis based on the Apfel Score and premedication with midazolam.

Pupillometry to show stress release during equine sports massage therapy

Anecdotal reports state that wellness treatments for horses, such as massage therapy, relaxes the treated animal. Massage therapists and horse owners typically report an "improvement" without verifying or quantifying the treatment results. This paper shows that the effect of wellness treatment and stress release can be measured with pupillometry. One of the horse's pupils was photographed at the beginning and end of the treatment to determine the changes in the balance between the sympathetic and parasympathetic system activities. The owners assigned horses to two experimental groups: animals receiving a massage (N = 18) and horses standing with a person next to the horse for the time of a massage in the stable lane (N = 10). Six animals in the experimental group were excluded from the analysis because the pupils could not be traced. We opened the images of the pupil with Fiji (ImageJ) and used the elliptical selection tool to measure the pupils' and iris' areas. The ratio between the pupils' aperture and the iris' area was a normalized measure for pupil size. At the end of the experiment, we compared the normalized size of the pupils with a two-tailed paired t-test within groups and a two-tailed t-test between groups. For the experimental group, it was before and after the treatment, and for the control group, before and after the horse was placed in the stable lane. Comparisons between the experimental and control groups were made at the procedure's beginning and end. The treatment significantly decreased the normalized pupil area in the experimental group, on average, by a factor of 0.78 ± 0.15 (P = 0.042). For the horses in the control group, the pupil size increased, on average, by a factor of 1.14 ± 018. Changes were statistically not significant (P = 0.19). The initial pupil size of the horses in the experimental group was 1.88 times larger than that in the control group. After the treatment, the difference was reduced to a factor of 1.25. At the beginning of the experiment, the horses in the experimental group had, on average, larger pupil sizes than the horses in the control group, indicating that the horses in the experimental group were more stressed before the treatment than the control animals. The observed changes in pupil size in the experimental group likely resulted from enhanced parasympathetic and diminished sympathetic activity resulting from the treatment. Observed changes in pupil size agree with the anecdotal horse owner reports and the therapist's treatment notes.

Automated pupillometry and optic nerve sheath diameter ultrasound to define tuberculous meningitis disease severity and prognosis

BACKGROUND

Tuberculous meningitis (TBM) causes high mortality and morbidity, in part due to raised intracranial pressure (ICP). Automated pupillometry (NPi) and optic nerve sheath diameter (ONSD) are both low-cost, easy-to-use and non-invasive techniques that correlate with ICP and neurological status. However, it is uncertain how to apply these techniques in the management of TBM.

METHODS

We conducted a pilot study enrolling 20 adults with TBM in the Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam. Our objective was to investigate the relationships between baseline and serial measurements of NPi and ONSD and disease severity and outcome. Serial NPi and ONSD were performed for 30 days, at discharge, and at 3-months, with measurements correlated with clinical progression and outcomes.

RESULTS

ONSD and NPi measurements had an inverse relationship. Higher ONSD and lower NPi values were associated with lower Glasgow coma score. Baseline NPi was a strong predictor 3-month outcome (median NPi 4.55, interquartile range 4.35-4.65 for good outcomes versus 2.60, IQR 0.65-3.95 for poor outcomes, p = 0.002). Pupil inequality (NPi ≥0.7) was also strongly associated with poor 3-month outcomes (p = 0.006). Individual participants' serial NPi and ONSD were variable during initial treatment and correlated with clinical condition and outcome.

CONCLUSION

Pupillometry and ONSD may be used to predict clinical deterioration and outcome from TBM. Future, larger studies are need explore the optimal timing of measurements and to define how they might be used to optimise treatments and improve outcomes from TBM.

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.

Pupillometry in the follow-up of patients undergoing EVT - prediction of space-occupying hemispheric infarction

BACKGROUND

Despite benefits of endovascular treatment (EVT) for large vessel occlusion (LVO) ischemic stroke, space-occupying brain edema (BE) represents a detrimental complication. In critical-care settings, CT-imaging is needed for monitoring these patients. Yet, bed-side techniques with the potential to predict whether patients develop BE or not would facilitate a time- and cost-efficient patient care. We assessed clinical significance of automated pupillometry in the follow-up of patients undergoing EVT.

METHODS

From 10/2018 to 10/2021, neurocritical-care-unit patients were retrospectively enrolled after EVT of anterior circulation LVO. We monitored parameters of pupillary reactivity [light-reflex-latency (Lat), constriction- and redilation-velocities (CV, DV), percentage-change-of-apertures (per-change); NeurOptics-pupilometer®] up to every hour on day 1-3 of ICU stay. BE was defined as midline shift ≥ 5 mm on follow-up imaging 3-5 days after EVT. We calculated mean values of intra-individual differences between successive pairs of parameters (mean-deltas), determined best discriminative cut-off values for BE development (ROC-analyses), and evaluated prognostic performance of pupillometry for BE development (sensitivity/specificity/positive-/negative-predictive-values).

RESULTS

3241 pupillary assessments of 122 patients [67 women, 73 years (61.0-85.0)] were included. 13/122 patients developed BE. Patients with BE had significantly lower CVs, DVs, and smaller per-changes than patients without BE. On day 1 after EVT mean-deltas of CV, DV, and per-changes were significantly lower in patients with than without BE. Positive-predictive-values of calculated thresholds to discriminate both groups were considerably low, yet, we found high negative-predictive-values for CV, DV, per-changes, and mean-deltas (max.: 98.4%).

CONCLUSION

Our data suggest associations between noninvasively detected changes in pupillary reactivity and BE early after LVO-EVT. Pupillometry may identify patients who are unlikely to develop BE and may not need repetitive follow-up-imaging or rescue-therapy.

Evaluation of Pupillometry for CYP2D6 Phenotyping in Children Treated with Tramadol

Following the contraindication of codeine use in children, increasing use of tramadol has been observed in pain management protocols. However, tramadol's pharmacokinetics (PK) and pharmacodynamics are influenced by cytochrome P450 (CYP)2D6 activity, similarly to codeine. Previous studies in adults have demonstrated a correlation between pupillary response and tramadol PK. Our objective was to evaluate pupillometry as a phenotyping method to assess CYP2D6 activity in children treated with tramadol. We included 41 children (mean age 11 years) receiving a first dose of tramadol (2 mg/kg) in the emergency room (ER) as part of their routine care. CYP2D6 phenotyping and genotyping were performed. The concentrations of tramadol and its active metabolite, M1, were measured, and static and dynamic pupillometry was conducted using a handheld pupillometer at the time of tramadol administration and during the ER stay. Pupillometric measurements were obtained for 37 children. Tramadol affected pupillary parameters, with a decrease in pupil diameter in 83.8% of children (p = 0.002) (mean decrease 14.1 ± 16.7%) and a decrease in reflex amplitude constriction in 78.4% (p = 0.011) (mean decrease 17.7 ± 34.5%) at T150 compared to T0. We were unable to identify a correlation between pupillometry measurements and CYP2D6 activity. Likely confounding factors include light intensity, pain, and stress, making the procedure less feasible in paediatric emergency settings.

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).

The Role of Pupillometry in the Assessment of Pain in Children Under General Anesthesia: A Prospective Single-Blinded Observational Study

Background and objective The management and treatment of nociception remain one of the major challenges in anesthesiology, and hemodynamic variations may occur due to inadequate analgesia, which at times can be injurious. Pupillometry is a new noninvasive tool to assess nociception during anesthesia. The amount of pupillary reflex dilation (PRD) is directly proportional to the intensity of nociceptive stimuli and inversely proportional to the opioid dosage. This study aimed to assess the use of pupillometry as reflex pupillary dilatation in response to surgical stimulus in children under general anesthesia and to guide intraoperative opioid consumption. Materials and methods After obtaining approval from the institutional ethics committee and written consent from parents, children with an American Society of Anesthesiology (ASA) classification of I and II and aged 2-12 years who were undergoing surgery under general anesthesia were enrolled in this prospective randomized observational study. General anesthesia was standardized with propofol, sevoflurane, and O2 and N2O (50:50%), and fentanyl administration was guided by pupil diameter changes. The primary outcome was to measure pupillary dilatation in response to pain and fentanyl administration guided by it. Results A total of 72 patients were included in the study. The mean pupil diameter significantly increased after surgical stimulus from 1.37 ±0.87 to 2.40 ±1.95 mm (p<0.001). The heart rate (116.2 ±12.25 to 118.50 ±8.20 beats/minute, p=0.18) and systolic BP (114.60 ±17.73 to 118.50 ±12.25 mmHg, p=0.12) did not change significantly on stimulus. The mean fentanyl consumption was 2.4 ug/kg and the side effects were not remarkable. Conclusion Based on our findings, pain has a significant influence on the pupil dilatation reflex in anesthetized children, and opioid administration based on pupil diameter can be valuable in clinical settings. We recommend the use of pupillometry as a pain index in children undergoing surgery under general anesthesia, and it can be a beneficial tool for assessing intraoperative pain. Newer techniques and developments are required in this field.

Slaughtering of Water Buffalo (Bubalus bubalis) with and without Stunning: A Focus on the Neurobiology of Pain, Hyperalgesia, and Sensitization

The slaughter process in livestock is considered a stressor where the transport and handling of animals, as well as the selected stunning and bleeding methods, can cause acute pain, distress, and suffering. In water buffaloes, although stunning is known to be performed before bleeding to induce unconsciousness, no emphasis is made on the nociceptive events during this process. Particularly, current mechanical stunning methods applied to cattle are unsuitable for water buffaloes due to anatomical differences in the skull from other large ruminants. Furthermore, although very high-pressure pneumatic (200-220 psi) may be effective in the frontal position for lighter-weight water buffalos, for heavier animals, it is less likely to be effective. The present review aims: (1) to analyze the anatomical particularities of water buffaloes to discuss the importance of selecting a stunning method suitable for buffaloes, and (2) to revise the potential pain-related consequences, such as hyperalgesia and sensitization, and the signs to assess the stun quality and death to comprehend the relevance of a proper technique according to the species.

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.

Assessment of Pain and Inflammation in Domestic Animals Using Infrared Thermography: A Narrative Review

Pain assessment in domestic animals has gained importance in recent years due to the recognition of the physiological, behavioral, and endocrine consequences of acute pain on animal production, welfare, and animal model validity. Current approaches to identifying acute pain mainly rely on behavioral-based scales, quantifying pain-related biomarkers, and the use of devices monitoring sympathetic activity. Infrared thermography is an alternative that could be used to correlate the changes in the superficial temperature with other tools and thus be an additional or alternate acute pain assessment marker. Moreover, its non-invasiveness and the objective nature of its readout make it potentially very valuable. However, at the current time, it is not in widespread use as an assessment strategy. The present review discusses scientific evidence for infrared thermography as a tool to evaluate pain, limiting its use to monitor acute pain in pathological processes and invasive procedures, as well as its use for perioperative monitoring in domestic animals.

Combat Sports as a Model for Measuring the Effects of Repeated Head Impacts on Autonomic Brain Function: A Brief Report of Pilot Data

Automated pupil light reflex (PLR) is a valid indicator of dysfunctional autonomic brain function following traumatic brain injury. PLR's use in identifying disturbed autonomic brain function following repeated head impacts without outwardly visible symptoms has not yet been examined. As a combat sport featuring repeated 'sub-concussive' head impacts, mixed martial arts (MMA) sparring may provide a model to understand such changes. The aim of this pilot study was to explore which, if any, PLR variables are affected by MMA sparring. A cohort of n = 7 MMA athletes (age = 24 ± 3 years; mass = 76.5 ± 9 kg; stature = 176.4 ± 8.5 cm) took part in their regular sparring sessions (eight rounds × 3 min: 1 min recovery). PLR of both eyes was measured immediately pre- and post-sparring using a Neuroptic NPi-200. Bayesian paired samples t-tests (BF₁₀ ≥ 3) revealed decreased maximum pupil size (BF₁₀ = 3), decreased minimum pupil size (BF₁₀ = 4) and reduced PLR latency (BF₁₀ = 3) post-sparring. Anisocoria was present prior to sparring and increased post-sparring, with both eyes having different minimum and maximum pupil sizes (BF₁₀ = 3-4) and constriction velocities post-sparring (BF₁₀ = 3). These pilot data suggest repeated head impacts may cause disturbances to autonomic brain function in the absence of outwardly visible symptoms. These results provide direction for cohort-controlled studies to formally investigate the potential changes observed.

The Influence of Obesity in the Autonomic Nervous System Activity in School-Aged Children in Northern Portugal: A Cross-Sectional Study

INTRODUCTION

Obesity is one of the most prevalent chronic diseases in childhood, being an important public health issue. Excessive weight has been associated with autonomic dysfunction but the evidence in children is scarce. Therefore, the aim of this study was to assess the effect of overweight and obesity on the autonomic nervous system activity, in children.

MATERIAL AND METHODS

Data from a cross-sectional study of 1602 children, aged 7 to 12 years, was used and 858 children were included in the analysis. Body mass index was calculated and classified according to criteria of the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC) and the International Obesity Task Force (IOTF). Body composition was characterized by bioelectrical impedance. Linear regression models were used to determine the association between body mass index, body composition and the autonomic nervous system activity, assessed by pupillometry.

RESULTS

Average dilation velocity was higher among children with obesity, according to the CDC and percentage of body fat criteria (β = 0.053, 95% CI = 0.005 to 0.101 and β = 0.063, 95% CI = 0.016 to 0.109, respectively). The same trend was observed for WHO and IOTF criteria (β = 0.045, 95% CI = -0.001 to 0.091, and β = 0.055, 95% CI = -0.001 to 0.111, respectively). CDC and WHO body mass index z-scores were also positively associated with the values of average dilation velocity (rs = 0.030, p = 0.048; and rs = 0.027, p = 0.042, respectively).

CONCLUSION

Our findings suggest an association between body mass and changes in the autonomic activity, Moreover, this study provides proof of concept for interventions targeting the prevention/treatment of obesity in children that may offer some benefit in re-establishing the balance of the autonomic nervous system, and subsequently preventing the consequences associated with the autonomic nervous system dysfunction.

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.

Pupillary Pain Index Predicts Postoperative Pain but Not the Effect of Peripheral Regional Anaesthesia in Patients Undergoing Total Hip or Total Knee Arthroplasty: An Observational Study

Background and Objectives: The pupillary pain index (PPI) allows the evaluation of intraoperative nociception by measuring pupillary reaction after a localized electrical stimulus. It was the objective of this observational cohort study to investigate the pupillary pain index (PPI) as a method to evaluate the fascia iliaca block (FIB) or adductor canal block (ACB) sensory areas during general anaesthesia in orthopaedic patients with lower-extremity joint replacement surgery. Materials and Methods: Orthopaedic patients undergoing hip or knee arthroplasty were included. After anaesthesia induction, patients received an ultrasound-guided single-shot FIB or ACB with 30 mL and 20 mL of 0.375% ropivacaine, respectively. Anaesthesia was maintained with isoflurane or propofol/remifentanil. The first PPI measurements were performed after anaesthesia induction and before block insertion, the second at the end of surgery. Pupillometry scores were evaluated in the area of the femoral or saphenous nerve (target) and C3 dermatome (control). Primary outcomes were differences between PPIs before and after peripheral block insertion as well as the relationship between PPIs and postoperative pain scores; secondary outcomes were the relationship between PPIs and opioid requirements after surgery. Results: PPI decreased significantly from the first to the second measurement (4.17 ± 2.7 vs. 1.6 ± 1.2, p < 0.001 for target; 4.46 ± 2.7 vs. 2.17 ± 2.1, p < 0.001 for control). Control and target measurements did not show significant differences. A linear regression analysis showed that early postoperative pain scores could be predicted with intraoperative piritramide with improved prediction after adding PPI scores, PCA opioids and surgery type. Forty-eight-hour pain scores at rest and in movement were correlated with intraoperative piritramide and control PPI after the PNB in movement and with second-postoperative-day opioids and target PPI scores before block insertion, respectively. Conclusions: While the effect of an FIB and ACB could not be shown with PPI postoperative pain scores due to a large effect of opioids, perioperative PPI was shown to be associated with postoperative pain. These results suggest that preoperative PPI may be used to predict postoperative pain.

A Video Segmentation Pipeline for Assessing changes in Pupil Response to Light After Cannabis Consumption

Due to long-standing federal restrictions on cannabis-related research, the implications of cannabis legalization on traffic and occupational safety are understudied. Accordingly, there is a need for objective and validated measures of acute cannabis impairment that may be applied in public safety and occupational settings. Pupillary response to light may offer an avenue for detection that outperforms typical sobriety tests and THC concentrations. We developed a video processing and analysis pipeline that extracts pupil sizes during a light stimulus test administered with goggles utilizing infrared videography. The analysis compared pupil size trajectories in response to a light for those with occasional, daily, and no cannabis use before and after smoking. Pupils were segmented using a combination of image pre-processing techniques and segmentation algorithms which were validated using manually segmented data and found to achieve 99% precision and 94% F-score. Features extracted from the pupil size trajectories captured pupil constriction and rebound dilation and were analyzed using generalized estimating equations. We find that acute cannabis use results in less pupil constriction and slower pupil rebound dilation in the light stimulus test.

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.

Non-Invasive Intracranial Pressure Monitoring

(1) Background: Intracranial pressure (ICP) monitoring plays a key role in the treatment of patients in intensive care units, as well as during long-term surgeries and interventions. The gold standard is invasive measurement and monitoring via ventricular drainage or a parenchymal probe. In recent decades, numerous methods for non-invasive measurement have been evaluated but none have become established in routine clinical practice. The aim of this study was to reflect on the current state of research and shed light on relevant techniques for future clinical application. (2) Methods: We performed a PubMed search for “non-invasive AND ICP AND (measurement OR monitoring)” and identified 306 results. On the basis of these search results, we conducted an in-depth source analysis to identify additional methods. Studies were analyzed for design, patient type (e.g., infants, adults, and shunt patients), statistical evaluation (correlation, accuracy, and reliability), number of included measurements, and statistical assessment of accuracy and reliability. (3) Results: MRI-ICP and two-depth Doppler showed the most potential (and were the most complex methods). Tympanic membrane temperature, diffuse correlation spectroscopy, natural resonance frequency, and retinal vein approaches were also promising. (4) Conclusions: To date, no convincing evidence supports the use of a particular method for non-invasive intracranial pressure measurement. However, many new approaches are under development.

Prognosis value of pupillometry in COVID-19 patients admitted in intensive care unit

INTRODUCTION

ICU patients with SARS-CoV-2-related pneumonia are at risk to develop a central dysautonomia which can contribute to mortality and respiratory failure. The pupillary size and its reactivity to light are controlled by the autonomic nervous system. Pupillometry parameters (PP) allow to predict outcomes in various acute brain injuries. We aim at assessing the most predictive PP of in-hospital mortality and the need for invasive mechanical ventilation (IV).

MATERIAL AND METHODS

We led a prospective, two centers, observational study. We recruited adult patients admitted to ICU for a severe SARS-CoV-2 related pneumonia between April and August 2020. The pupillometry was performed at admission including the measurement of baseline pupillary diameter (PD), PD variations (PDV), pupillary constriction velocity (PCV) and latency (PDL).

RESULTS

Fifty patients, 90 % males, aged 66 (60-70) years were included. Seven (14 %) patients died in hospital. The baseline PD (4.1 mm [3.5; 4.8] vs 2.6 mm [2.4; 4.0], P = 0.009), PDV (33 % [27; 39] vs 25 % [15; 36], P = 0.03) and PCV (3.5 mm.s^-1 [2.8; 4.4] vs 2.0 mm.s^-1 [1.9; 3.8], P = 0.02) were significantly lower in patients who will die. A PD value <2.75 mm was the most predictive parameter of in-hospital mortality, with an AUC = 0.81, CI 95 % [0.63; 0.99]. Twenty-four (48 %) patients required IV. PD and PDV were significantly lower in patients who were intubated (3.5 mm [2.8; 4.4] vs 4.2 mm [3.9; 5.2], P = 0.03; 28 % [25; 36 %] vs 35 % [32; 40], P = 0.049, respectively).

CONCLUSIONS

A reduced baseline PD is associated with bad outcomes in COVID-19 patients admitted in ICU. It is likely to reflect a brainstem autonomic dysfunction.

Effect of the using a pupillometer on recovery and early cognitive functions in anesthesia management for endoscopic retrograde cholangiopancreaticography in geriatric patients

Background/Aim: Endoscopic retrograde cholangiopancreatography (ERCP) is an invasive procedure used for the diagnosis and treatment of pancreaticobiliary pathologies. Because it is an invasive procedure that is difficult to tolerate by the patient and takes a long time, it is preferable to use it under deep patient sedation and even under general anesthesia in some cases. This study aimed to evaluate the effects of using a pupillometer versus the Ramsey sedation scale (RSS) during anesthesia management for ERCP on recovery and return of cognitive functions in the geriatric patient population. Methods: A mini-mental test was applied to evaluate the pre-operative cognitive functions of the cases before the intervention. The included patients were divided into groups using the sealed-envelope method. Management of the depth of anesthesia was evaluated by Ramsey sedation scale; in group R and was evaluated by pupillometer in group P. The infusion dose of dexmedetomidine was changed to 0.1 µg/kg/h according to the results of the evaluation. Results: Sixty cases were included in the study. No difference between the groups in terms of age (P=0.246), gender (P=0.797), American Society of Anesthesiologists (ASA) score (P=0.197), comorbidity (P=0.748), anesthesia duration (P=0.397), midazolam doses (P=0.561), propofol doses (P=0.677), and intra-operative hemodynamic values (P=0.668) were found. Intra-operative dexmedetomidine dose was statistically significantly lower (P=0.004), and recovery was faster in group P (P<0.001). While no differences between the groups in the pre-operative mini-mental test scores (P=0.140) were found, the post-operative scores were statistically significantly lower in group R (P=0.025). Conclusion: In this study, it was observed that the pupillometer led to a reduction in the use of dexmedetomidine and cognitive functions were better during the post-operative recovery period. As a result, depth of anesthesia can be monitored with a pupillometer. Although the use of pupillometer in endoscopic interventions in the geriatric patient group does not make a hemodynamic difference when compared with the RSS, the pupillometer leads to accelerated recovery from anesthesia, improvement in the return of cognitive functions, and reduction in drug consumption.

Quantitative pupillometry and radiographic markers of intracranial midline shift: A pilot study

Background

Asymmetric pupil reactivity or size can be early clinical indicators of midbrain compression due to supratentorial ischemic stroke or primary intraparenchymal hemorrhage (IPH). Radiographic midline shift is associated with worse functional outcomes and life-saving interventions. Better understanding of quantitative pupil characteristics would be a non-invasive, safe, and cost-effective way to improve identification of life-threatening mass effect and resource utilization of emergent radiographic imaging. We aimed to better characterize the association between midline shift at various anatomic levels and quantitative pupil characteristics.

Methods

We conducted a multicenter retrospective study of brain CT images within 75 min of a quantitative pupil observation from patients admitted to Neuro-ICUs between 2016 and 2020 with large (>1/3 of the middle cerebral artery territory) acute supratentorial ischemic stroke or primary IPH > 30 mm³. For each image, we measured midline shift at the septum pellucidum (MLS-SP), pineal gland shift (PGS), the ratio of the ipsilateral to contralateral midbrain width (IMW/CMW), and other exploratory markers of radiographic shift/compression. Pupil reactivity was measured using an automated infrared pupillometer (NeurOptics^®, Inc.), specifically the proprietary algorithm for Neurological Pupil Index^® (NPi). We used rank-normalization and linear mixed-effects models, stratified by diagnosis and hemorrhagic conversion, to test associations of radiographic markers of shift and asymmetric pupil reactivity (Diff NPi), adjusting for age, lesion volume, Glasgow Coma Scale, and osmotic medications.

Results

Of 53 patients with 74 CT images, 26 (49.1%) were female, and median age was 67 years. MLS-SP and PGS were greater in patients with IPH, compared to patients with ischemic stroke (6.2 v. 4.0 mm, 5.6 v. 3.4 mm, respectively). We found no significant associations between pupil reactivity and the radiographic markers of shift when adjusting for confounders. However, we found potentially relevant relationships between MLS-SP and Diff NPi in our IPH cohort (β = 0.11, SE 0.04, P = 0.01), and PGS and Diff NPi in the ischemic stroke cohort (β = 0.16, SE 0.09, P = 0.07).

Conclusion

We found the relationship between midline shift and asymmetric pupil reactivity may differ between IPH and ischemic stroke. Our study may serve as necessary preliminary data to guide further prospective investigation into how clinical manifestations of radiographic midline shift differ by diagnosis and proximity to the midbrain.

Pupillometric findings in ATTRv patients and carriers: results from a single-centre experience

INTRODUCTION

Hereditary transthyretin amyloidosis (ATTRv) is a treatable multisystemic disease with great phenotypic heterogeneity. Among extra-neurological features, pupillary abnormalities have been reported, either related to amyloid deposition in the eye or to a progressive autonomic neuropathy.

OBJECTIVE

To evaluate the role of automated pupillometry, a non-invasive and rapid test able to provide objective and reproducible data on pupil size and reactivity, as a marker of disease severity in late-onset ATTRv patients.

PATIENTS AND METHODS

We performed automated pupillometry on a cohort of ATTRv patients and pre-symptomatic TTR mutation carriers and compared results to healthy controls. An exhaustive clinical and instrumental evaluation was performed on all enrolled subjects.

RESULTS

A statistically significant difference in most pupillometry parameters was found in ATTRv patients as compared to both carriers and healthy controls. Moreover, in ATTRv patients, we found a significant correlation between many pupillometry findings and disease duration, as well as widely accepted clinical scales and investigations (NIS, Sudoscan from feet, and Norfolk QoL-DN questionnaire).

CONCLUSIONS

We suggest pupillometry may play a role as a reliable and non-invasive biomarker to evaluate ATTRv disease severity and monitor its progression.

Development of reference intervals for pupillometry in healthy dogs

BACKGROUND

Pupillometry, the measurement of pupil size and reactivity to a stimulus, has various uses in both human and veterinary medicine. These reflect autonomic tone, with the potential to assess nociception and emotion. Infrared pupillometry reduces inaccuracies that may occur when the pupillary light reflex is determined subjectively by the examiner. To our knowledge, there are no published studies outlining normal reference intervals for automated pupillometry in dogs.

OBJECTIVE

The objective of this study was to develop de novo automated pupillometry reference intervals from 126 healthy canine eyes.

METHODS

The pupillary light reflex (PLR) was measured with a handheld pupillometer (NeurOptics™ PLR-200™ Pupillometer). Parameters recorded included maximum pupil diameter (MAX), minimum pupil diameter (MIN), percent constriction (CON), latency (LAT), average constriction velocity (ACV), maximum constriction velocity (MCV), average dilation velocity (ADV) and time to 75% pupil diameter recovery (T75). One measurement was obtained for each eye.

RESULTS

The following reference intervals were developed: MAX (6.05-11.30 mm), MIN (3.76-9.44 mm), CON (-37.89 to -9.64 %), LAT (0.11-0.30 s), ACV (-6.39 to -2.63 mm/ s), MCV (-8.45 to -3.75 mm/s), ADV (-0.21-1.77 mm/s), and T75 (0.49-3.20 s).

CLINICAL SIGNIFICANCE

The reference intervals developed in this study are an essential first step to facilitate future research exploring pupillometry as a pain assessment method in dogs.

Pupillary reflex dilation and pain index evaluation during general anesthesia using sufentanil: a double-blind randomized controlled trial

Aim: In a single-center, double-blind, randomized controlled trial, we evaluated whether pupillometry-controlled use of sufentanil is better than free-choice administration of sufentanil by anesthesiologists. Patients & methods: 61 patients undergoing daycare gynecological or abdominal surgery were enrolled. A pupillometry pain index score chart was introduced for administration guidance of sufentanil. Results: The first objective, patient well-being, did not show a significant difference with painkiller usage and health state index at day 1 postoperatively. Secondly, we experienced difficulty in interpretation of the pupillometry score. Thirdly, opioid usage was higher in the intervention group (20.1 vs 14.8 mcg; p = 0.017). Conclusion: The use of pupillometry and pain index chart for bolus sufentanil with our protocol showed an unwanted higher sufentanil usage without a significant difference in patient wellbeing. (Ethics Committee EC17/28/319 of the University Hospital of Antwerp. Registration at clinicaltrials.gov NCT03248908.).

Pupil maximum constriction velocity predicts post-induction hypotension in patients with lower ASA status: a prospective observational study

Background

Individuals affected by autonomic dysfunction are at a higher risk of developing hypotension following anesthesia induction. Dynamic pupillometry has previously been employed as a means of assessing autonomic function. This prospective observational study was developed to determine whether pupillary light reflex (PLR) parameters can reliably predict post-induction hypotension (PIH).

Methods

This study enrolled patients with lower ASA status (I-II) undergoing elective surgery. PLR recordings for these patients prior to anesthesia induction were made with an infrared pupil camcorder, with a computer being used to assess Average Constriction Velocity (ACV), Maximum Constriction Velocity (MCV), and Constriction Ratio (CR). PIH was defined by a > 30% reduction in mean arterial pressure (MAP) or any MAP recording < 65 mmHg for at least 1 min from the time of induction until 10 minutes following intubation. Patients were stratified into PIH and non-PIH groups based on whether or not they developed hypotension.

Results

This study enrolled 61 total patients, of whom 31 (50.8%) exhibited one or more hypotensive episodes. Patients in the PIH group exhibited significantly smaller ACV (P = 0.003) and MCV values (P < 0.001), as well as a higher CR (P = 0.003). Following adjustment for certain factors (Model 2), MCV was identified as a protective factor for PIH (Odds Ratio: 0.369). Receiver operating characteristic (ROC) analyses revealed that relative to CR (AUC: 0.695, 95% CI: 0.563–0.806; P = 0.004), the reciprocal of MCV (1/MCV) offered greater value as a predictor of PIH (AUC: 0.803,95%CI: 0.681–0.894; P < 0.001).

Conclusion

These results indicate that pupil maximum constriction velocity is a reliable predictor of post-induction hypotension in individuals of ASA I-II status undergoing elective surgery.

Trial registration

This study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR2200057164, registration date: 01/03/2022).

Investigation of behavioral pain scale, critical care pain observation tool, nociceptive flexion reflex and pupillary dilatation reflex as predictors of behavioral reactions to nociceptive procedures in critically ill patients unable to self-report pain

BACKGROUND

Procedural pain is a common burden in critical care treatment and the prediction of nociceptive reactions remains challenging. Thus, we investigated the behavioral pain scale (BPS), the critical pain observational Tool (CPOT), the nociceptive flexion reflex (NFR), the pupillary dilation reflex (PDR), the Richmond agitation-sedation scale (RASS) as predictors of behavioral reactions to nociceptive procedures.

METHODS

In this monocentric, prospective, observational study we analyzed data of 128 critically ill adults unable to self-report pain to investigate the predictability of behavioral reactions to two procedures: endotracheal suctioning and turning. Next to routine clinical data, CPOT, BPS, PDR, NFR, RASS, propofol and sufentanil doses were recorded before the procedures.

RESULTS

For endotracheal suctioning, NFR, BPS, CPOT, RASS showed predictive performances significantly better than chance, but none of them performed significantly better than the sufentanil dose rate. For turning, BPS, CPOT, RASS showed predictive performances significantly better than chance, but only the RASS performed significantly better than the propofol dose rate.

CONCLUSIONS

Behavioral reactions to both investigated clinical procedures can be predicted by observational scales or nociceptive reflexes. For endotracheal suctioning, none of the predictors performed superior to using the sufentanil dose rate as a predictor. As using sufentanil as a predictor requires no extra effort in contrast to the other predictors, none of the here investigated tools seem advisable for predicting behavioral reactions to endotracheal suctioning. For patient turning, the RASS predicts reactions better than any other tool.

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.

Efficacy of Quantitative Pupillary Light Reflex for Predicting Neurological Outcomes in Patients Treated with Targeted Temperature Management after Cardiac Arrest: A Systematic Review and Meta-Analysis

Background and objectives: This study aims to evaluate the usefulness of the quantitative pupillary light reflex as a prognostic tool for neurological outcomes in post-cardiac arrest patients treated with targeted temperature management (TTM). Material and Methods: We systematically searched MEDLINE, EMBASE, and the Cochrane Library (search date: 9 July 2021) for studies on post-cardiac arrest patients treated with TTM that had measured the percent constriction of pupillary light reflex (%PLR) with quantitative pupillometry as well as assessed the neurological outcome. For an assessment of the methodological quality of the included studies, two authors utilized the prognosis study tool independently. Results: A total of 618 patients from four studies were included in this study. Standardized mean differences (SMDs) were calculated to compare patients with good or poor neurological outcomes. A higher %PLR measured at 0–24 h after hospital admission was related to good neurological outcomes at 3 months in post-cardiac arrest patients treated with TTM (SMD 0.87; 95% confidence interval 0.70–1.05; I² = 0%). A higher %PLR amplitude measured at 24–48 h after hospital admission was also associated with a good neurological outcome at 3 months in post-cardiac arrest patients treated with TTM, but with high heterogeneity (standardized mean difference 0.86; 95% confidence interval 0.40–1.32; I² = 70%). The evidence supporting these findings was of poor quality. For poor neurological outcome, the prognosis accuracy of %PLR was 9.19 (pooled diagnostic odds ratio, I² = 0%) and 0.75 (area under the curve). Conclusions: The present meta-analysis could not reveal that change of %PLR was an effective tool in predicting neurological outcomes for post-cardiac arrest patients treated with TTM owing to a paucity of included studies and the poor quality of the evidence.

The melanopsin-mediated pupil response is reduced in idiopathic hypersomnia with long sleep time

Idiopathic hypersomnia (IH), characterized by an excessive day-time sleepiness, a prolonged total sleep time on 24 h and/or a reduced sleep latency, affects 1 in 2000 individuals from the general population. However, IH remains underdiagnosed and inaccurately treated despite colossal social, professional and personal impacts. The pathogenesis of IH is poorly known, but recent works have suggested possible alterations of phototransduction. In this context, to identify biomarkers of IH, we studied the Post-Illumination Pupil Response (PIPR) using a specific pupillometry protocol reflecting the melanopsin-mediated pupil response in IH patients with prolonged total sleep time (TST > 660 min) and in healthy subjects. Twenty-eight patients with IH (women 86%, 25.4 year-old ± 4.9) and 29 controls (women 52%, 27.1 year-old ± 3.9) were included. After correction on baseline pupil diameter, the PIPR was compared between groups and correlated to sociodemographic and sleep parameters. We found that patients with IH had a lower relative PIPR compared to controls (32.6 ± 9.9% vs 38.5 ± 10.2%, p = 0.037) suggesting a reduced melanopsin response. In addition, the PIPR was not correlated to age, chronotype, TST, nor depressive symptoms. The melanopsin-specific PIPR may be an innovative trait marker of IH and the pupillometry might be a promising tool to better characterize hypersomnia.

Comparison of Antinociceptive Properties Between Sevoflurane and Desflurane Using Pupillary Dilation Reflex Under Equivalent Minimum Alveolar Concentration: A Randomized Controlled Trial

BACKGROUND

The pupillary dilation reflex (PDR), the change in pupil size after a nociceptive stimulus, has been used to assess antinociception during anesthesia. The aim of this study was to compare the antinociceptive properties of sevoflurane and desflurane by measuring the PDR amplitude.

METHODS

Seventy patients between 20 and 55 years of age were randomly allocated to receive either sevoflurane or desflurane. The PDR amplitude after an electrical standardized noxious stimulation (SNT) was measured using an infrared pupillometer under 1.0 minimum alveolar concentration (MAC). The pupil diameter was measured from 5 seconds before to 5 minutes after the SNT. The mean arterial pressure (MAP), heart rate (HR), and bispectral index (BIS) were also measured immediately before and after SNT as well as 1 minute and 5 minutes after SNT. The primary outcome was the maximum percent increase from the prestimulation value of the pupil diameter, and the secondary outcomes were the maximum percent increase from the prestimulation value of the MAP, HR, and BIS after SNT.

RESULTS

The maximum percent increase of the pupil diameter after SNT was not different between the 2 groups (median [first quartile to third quartile], 45.1 [29.3-80.3] vs 43.4 [27.0-103.1]; median difference, -0.3 [95% confidence interval, -16.0 to 16.5]; P = .986). Before SNT, the MAP was higher under 1.0 MAC of sevoflurane than desflurane; however, the maximum percent increase of MAP, HR, and BIS was not different between the 2 groups.

CONCLUSIONS

The amount of change in the PDR amplitude, MAP, and HR after SNT was not different between sevoflurane and desflurane anesthesia. This result might suggest that sevoflurane and desflurane may not have different antinociceptive properties at equivalent MAC.

Dexmedetomidine and Other Analgosedatives Alter Pupil Characteristics in Critically Ill Patients

In critically ill patients with neurologic disease, pupil examination abnormalities can signify evolving intracranial pathology. Analgesic and sedative medications (analgosedatives) target pupillary pathways, but it remains unknown how analgosedatives alter pupil findings in the clinical care setting. We assessed dexmedetomidine and other analgosedative associations with pupil reactivity and size in a heterogeneous cohort of critically ill patients with acute intracranial pathology.

DESIGN

Retrospective cohort study.

SETTING

Two neurologic ICUs between 2016 and 2018.

PATIENTS

Critically ill adult patients with pupil measurements within 60 minutes of analgosedative administration. Patients with a history of intrinsic retinal pathology, extracranial injury, inaccessible brain imaging, or no Glasgow Coma Scale (GCS) data were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We used mixed-effects linear regression accounting for intrapatient correlations and adjusting for sex, age, GCS score, radiographic mass effect, medication confounders, and ambient light. We tested the association between an initiation or increased IV infusion of dexmedetomidine and pupil reactivity (Neurologic Pupil Index [NPi]) and resting pupil size (mm) obtained using NeurOptics NPi-200 (NeurOptics, Irvine, CA) pupillometer. Of our 221 patients with 9,897 pupil observations (median age, 60 [interquartile range, 50-68]; 59% male), 37 patients (166 pupil observations) were exposed to dexmedetomidine. Dexmedetomidine was associated with higher average NPi (β = 0.18 per 1 unit increase in rank-normalized NPi ± 0.04; p < 0.001) and smaller pupil size (β = -0.25 ± 0.05; p < 0.001). Exploratory analyses revealed that acetaminophen was associated with higher average NPi (β = 0.04 ± 0.02; p = 0.02) and that most IV infusion analgosedatives including propofol, fentanyl, and midazolam were associated with smaller pupil size.

CONCLUSIONS

Dexmedetomidine is associated with higher pupil reactivity (high NPi) and smaller pupil size in a cohort of critically ill patients with neurologic injury. Familiarity with expected pupil changes following analgosedative administration is important for accurate interpretation of pupil examination findings, facilitating optimal management of patients with acute intracranial pathology.

Neurological Pupil Index for the Early Prediction of Outcome in Severe Acute Brain Injury Patients

In this study, we examined the early value of automated quantitative pupillary examination, using the Neurological Pupil index (NPi), to predict the long-term outcome of acute brain injured (ABI) patients. We performed a single-centre retrospective study (October 2016−March 2019) in ABI patients who underwent NPi measurement during the first 3 days following brain insult. We examined the performance of NPi—alone or in combination with other baseline demographic (age) and radiologic (CT midline shift) predictors—to prognosticate unfavourable 6-month outcome (Glasgow Outcome Scale 1−3). A total of 145 severely brain-injured subjects (65 traumatic brain injury, TBI; 80 non-TBI) were studied. At each time point tested, NPi <3 was highly predictive of unfavourable outcome, with highest specificity (100% (90−100)) at day 3 (sensitivity 24% (15−35), negative predictive value 36% (34−39)). The addition of NPi, from day 1 following ABI to age and cerebral CT scan, provided the best prognostic performance (AUROC curve 0.85 vs. 0.78 without NPi, p = 0.008; DeLong test) for 6-month neurological outcome prediction. NPi, assessed at the early post-injury phase, has a superior ability to predict unfavourable long-term neurological outcomes in severely brain-injured patients. The added prognostic value of NPi was most significant when complemented with baseline demographic and radiologic information.

Assessment of Combination of Automated Pupillometry and Heart Rate Variability to Detect Driving Fatigue

Objectives

Approximately 20~30% of all traffic accidents are caused by fatigue driving. However, limited practicability remains a barrier for the real application of available techniques to detect driving fatigue. Use of pupillary light reflex (PLR) may be potentially effective for driving fatigue detection.

Methods

A 90 min monotonous simulated driving task was utilized to induce driving fatigue. During the task, PLR measurements were performed at baseline and at an interval of 30 min. Subjective rating scales, heart rate variability (HRV) were monitored simultaneously.

Results

Thirty-two healthy volunteers in China participated in our study. Based on the results of subjective evaluation and behavioral performances, driving fatigue was verified to be successfully induced by a simulated driving task. Significant variations of PLR and HRV parameters were observed, which also showed significant relevance with the change in Karolinska Sleepiness Scale at several timepoints (|r| = 0.55 ~ 0.72, P < 0.001). Furthermore, PLR variations had excellent ability to detect driving fatigue with high sensitivity and specificity, of which maximum constriction velocity variations achieved a sensitivity of 85.00% and specificity of 72.34% for driving fatigue detection, vs. 82.50 and 78.72% with a combination of HRV variations, a nonsignificant difference (AUC = 0.835, 0.872, P > 0.05).

Conclusions

Pupillary light reflex variation may be a potential indicator in the detection of driving fatigue, achieving a comparative performance compared with the combination with heart rate variability. Further work may be involved in developing a commercialized driving fatigue detection system based on pupillary parameters.

Pupil response to painful stimuli during inhalation anaesthesia without opioids in children

BACKGROUND

Pupil dilation reflex measured by a pupillometer is known to be a useful parameter for assessing the response to perioperative noxious stimuli. In children, pupillometer can reflect changes after painful stimuli during anaesthesia or guide anaesthesia to reduce opioid consumption. However, to date, there are no data regarding pupil response during inhalation anaesthesia with analgesia by intravenous acetaminophen in children.

METHODS

We planned a prospective, single-armed study of children aged between 3 and 12 years who underwent surgery under general anaesthesia. Anaesthesia was maintained by 1 minimum alveolar concentration (MAC) of sevoflurane, and 15 mg/kg of acetaminophen was administered. Patients' left eye was examined using a pupillometer after induction, before and after skin incision and train-of-four stimulus. Pupil diameter and other pupillometric parameters were recorded. Increase in heart rate by 15% was regarded as insufficient analgesia to skin incision and indicative powers of pupillometric parameters for insufficient analgesia were examined by receiver-operating characteristics.

RESULTS

A total of 33 patients were included. Enlarged pupil, large increase in pupil diameter and low neurological pupil index (NPi) after skin incision were good indicators of insufficient analgesia for skin incision. Children with insufficient analgesia showed abnormal NPi value. However, increase in pupil diameter and decrease in NPi were observed even in patients without increase in the heart rate after the skin incision.

CONCLUSIONS

We suggest dilation of the pupil and decrease in NPi can indicate response to noxious stimuli in children. Regardless of sufficiency of analgesia, pupil dilation and decrease in NPi were observed after skin incision in children under general anaesthesia with 1 MAC of sevoflurane and intravenous acetaminophen.

Relationship Between the Onset of Ménière's Disease and Sympathetic Hyperactivity

Objective

The pathogenesis of Ménière's disease is still largely unknown; however, it is known to be strongly associated with stress. Excessive stress can cause hyperactivity of the sympathetic autonomic nervous system. With the aim of understanding changes in sympathetic hyperactivity before and after Ménière's disease, we compared autonomic nervous function in patients in a stable phase of Ménière's disease and that in healthy adults. We also gathered data over about 10 years on autonomic nervous function immediately before a Ménière's attack.

Study Design

Prospective study.

Patients

Autonomic nervous function was analyzed in 129 patients in a stable phase of Ménière's disease 31 healthy adult volunteers. In nine patients, autonomic nervous function was also measured immediately before and after treatment of a vertigo attack.

Main Outcome Measure

Power spectrum analysis of heart rate variability (HRV) of EEG/ECG and an infrared electronic pupillometer were used. Sympathetic and parasympathetic nervous function was measured.

Results

There were no statistically significant differences in autonomic nervous function determined by HRV and electronic pupillometry between patients in a stable phase of Ménière's disease and healthy adults. Sympathetic function as measured by electronic pupillometry parameters VD and T5 showed no difference between the affected and unaffected sides in the baseline data measured in the stable phase (VD: affected side is 31.02 ± 6.16 mm/sec, unaffected side is 29.25 ± 5.73 mm/sec; T5: affected side is 3.37 ± 0.43 msec, unaffected side is 3.25 ± 0.39 msec). In contrast, all nine patients whose HRV data had been obtained just before an attack showed marked suppression of the parasympathetic nervous system and activation of the sympathetic nervous system. Electronic pupillometry also revealed an overactivation of the sympathetic nervous system on the affected side, just before the attacks. Analysis of sequential changes after the onset of an attack revealed that overactivation on the affected side was reduced after treatment, and no difference between affected and unaffected sides was observed 3 days after treatment.

Conclusion

Detailed analysis of autonomic nervous function showed that immediately before an attack of Ménière's disease, the sympathetic nervous system on the affected side was strongly overactivated.