Pupillometry in Critical Care | Measure Pupil Size - NeurOptics
Frequent pupil evaluation is part of the protocol for care of the critically injured or ill patient. Pupil size and pupillary light reflex (PLR) are prognostic indicators.
pupil evaluation, pupilary evaluation, pupil diameter measurement, measure pupil size, pupil measurement, constriction velocity, critical care, critical care nursing, intraocular pressure, modified rankin scale, neurocritical care, neurologist, neuroscience nursing, neurosurgeon, NIH Stroke Scoring Scale, NIHSS
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Measure Pupil Size and Reactivity in the Critical Care Patient

As standard of care, all critically ill patients require routine neurological examination, including pupillary assessment. Assessment of pupil size and the pupillary light reflex (PLR) are critical components of the neurological exam for patients in acute care settings such as the Emergency Department (ED), Intensive Care Unit (ICU), Operating Room (OR), Post Anesthesia Care Unit (PACU), Progressive Care Units (PCU), and diagnostic areas such as Interventional Radiology (IR).(37, 76, 81) Pupillary changes correlate with neurological worsening and yet are often undetectable using traditional manual assessment methods. Manual pupillary assessment, using a flashlight or penlight, is prone to many sources of inaccuracy and is characterized by subjectivity and low interrater reliability.(2, 18, 37, 61, 72, 74, 85, 90)

Neurological Pupil index (NPi®)

The Neurological Pupil index (NPi®), calculated by the Pupillometer, reflects a comparison of all measured variables in the PLR to known normal observations. On the numeric NPi® scale, an NPi® from 3.0 to 4.9 is considered normal, while an NPi® less than 3.0 is considered abnormal. (9, 14, 19, 43, 46, 48, 60,66)

NeurOptics® NPi® Pupillometer

The NeurOptics® NPi® Pupillometer is a handheld, automated optical scanner that provides accurate, reliable, and objective measurements of pupillary size, symmetry, and reactivity throughout the entire PLR. The Neurological Pupil index (NPi), calculated by the Pupillometer, reflects a comparison of all measured variables in the PLR to a normative model. On the numeric NPi scale, an NPi from 3.0 to 4.9 is considered normal, while an NPi less than 3.0 is considered abnormal.(12, 18, 26, 65, 72, 74, 87, 90)

 

An abundance of scientific evidence supports NPi as the gold standard in pupillary assessment. The following findings have been objectively demonstrated when quantitative pupillometry and NPi are used:

i. Improvement in interrater reliability of pupillary metrics (2, 69,72, 74)
ii. Accuracy of measurement in common critical care scenarios and medication administration (1, 34, 43, 46, 48, 57, 60, 64, 69, 87, 94)

A recent study of inter-device reliability showed a very high level of agreement between the NPi-200 and NPi-300 pupillometer models among healthy controls and critically ill patients.(93) Although most herein referenced studies are based on the NPi-200, the results are translatable to and remain relevant in demonstrating the benefits of pupillometry and NPi in the NPi-300 Pupillometer.

Pupil Examination Is a Standard of Care and Important to Patient Outcome

The clinical neurological exam is an essential component in the assessment and care of patients with a wide variety of illnesses and injuries.(44, 54, 72) For centuries, clinicians have assessed the pupils of patients with impaired consciousness. Today, clinicians routinely evaluate pupils as part of the neurological exam and monitoring of all critically ill patients, including those with primary neurological injury as well as those at risk of secondary neurologic insults.(5, 37, 54 , 63, 72, 73, 76, 81, 96) Pupillary examination involves assessment of the functional status of two cranial nerves (CN) – the optic nerve (CN II) and the oculomotor nerve (CN III). Cranial nerve dysfunction may signal increased ICP and/or an increased risk of brain herniation.(3, 72)

 

Pupillary assessment is relied upon to guide decisions regarding patient triage and clinical intervention. Depending on pupillary status, neurosurgeons triage patients into either conservative therapy or surgical evacuation of mass lesions.(72, 76, 85) Patients who undergo prompt intervention such as surgery or hyperosmolar therapy after a new finding of pupil abnormality have a better chance of recovery.(27)

 

Abnormalities of pupillary response are associated with neurological deterioration and correlate with poor neurological outcomes.(5, 18, 27, 81, 95, 99) Along with other clinical information such as age, mechanism of injury and Glasgow Coma Score (GCS), the PLR is a useful prognostic indicator of survival, functional recovery and long-term outcome.(5, 17, 27, 96)

Manual Pupil Assessment Is Highly Subjective and Inaccurate

Traditionally, pupil assessment has been performed in a subjective manner, using a penlight or flashlight to manually evaluate pupil reactivity and a pupil gauge to estimate pupil size. Common terminology used to describe the PLR and pupil size includes “fixed” or “dilated” as well as “brisk”, “sluggish” or “non-reactive” pupils. These subjective terms are applied without a standardized clinical definition and yield a pronounced level of inter-examiner variability and error.(24, 63, 74)

 

Manual pupillary assessment is subject to compounded sources of inaccuracies and error and can result in as much as 39% inter-examiner variability.(5, 24, 37, 44, 62, 63, 72, 74) A variety of factors affect the reliability of manual assessment and increase inter-examiner disagreement. These factors may include pinpoint pupils, darkly pigmented irises, examiner skill level and visual acuity, and the strength and orientation of the light stimulus with respect to the patient’s eye.(3, 56) A 2016 study revealed that critical care and neurosurgical nurses consistently underestimated pupil size, were unable to identify anisocoria, and incorrectly assessed pupil reactivity.(44, 65)

The NPi® Pupillometer Is Reliable and Eliminates Subjectivity

The NeurOptics NPi Pupillometer (NeurOptics, Inc., Irvine, CA) is a Class 1 device that is 510k Exempt by the US FDA and CE-marked for the European Economic Area for use in both adults and children. This noninvasive, handheld optical scanner provides reliable and objective measurements of pupillary size, symmetry, and reactivity. The device stimulates pupil constriction with a gentle flash of light as the infrared camera captures 90 images in a 3 second period, measuring 8 different parameters that comprise the entire PLR. A disposable SmartGuard®, programmed with a unique patient identifier, records and stores 168 paired pupil assessments for trending and review throughout the patient’s admission. Launched in July 2021, the latest generation NPi-300 Pupillometer System includes wireless charging capabilities, an incorporated 1D/2D barcode scanner for automated patient identification entry, and other upgraded operational features.

 

Quantifying pupil reactivity on a numeric scale from 0 to 4.9, the Neurological Pupil index (NPi) allows rigorous interpretation and classification of the pupil response. The Pupillometer and the NPi Pupil Reactivity Assessment Scale provide objectivity in measurement by comparing the patient’s PLR to normative data in the NPi model. By automatically deriving whether the PLR falls within the normal (“brisk”) range (NPi > 3.0), the abnormal (“sluggish”) range (NPi < 3.0) or is “atypical”, “immeasurable” or “non-reactive” (NPi=0), the NPi Pupillometer provides a reliable and accurate way to quantify and trend pupillary response, offering increased confidence in the neurological assessment. (5, 8, 18, 24, 28, 34, 63, 72, 74)

 

Numerous studies attest to the reliability of the NPi Pupillometer.(52, 63, 69, 74, 95) In a recent study of unconscious and critically ill cardiac patients, researchers found twice the observer reproducibility and repeatability for quantitative measurements of pupil size with better measurements of reliability, for both size and reactivity, compared to the standard manual assessment. (69)

Monitoring, Treatment and Value in Critical Care

Recognized as an important tool in the ICU, automated pupillometry and NPi are being adopted in hospitals worldwide and becoming accepted as a standard of care for pupillary assessment in patients with a variety of critical illnesses.(3, 81, 85, 105) National and international guidelines now recommend NPi Pupillometry as the preferred method of pupillary assessment. (4, 38, 39, 68, 83)

Neurocritical Care

The NPi Pupillometer provides an objective means of assessing and trending pupillary reactivity across a broad spectrum of neurological conditions including traumatic brain injury (TBI), ischemic and hemorrhagic stroke, cerebral edema, herniation syndrome, and post-operative scenarios.(6, 14, 19, 20, 23, 29, 32, 34, 38, 40, 52, 66)

Quality Improvement

Quality measures help quantify healthcare processes, outcomes, patient perceptions, and organizational structure. They support quality goals for health care, which include effective, safe, efficient, patient-centered, equitable, and timely care. Ongoing quality improvement is a cornerstone for all hospitals and automated pupillometry is a natural fit as hospital quality systems continue to evolve.

 

Improved Quality of Neurological Exam

Assessment of pupil size and reactivity is a fundamental aspect of the neurological examination. However, manual pupil assessments (using a penlight or flashlight) are subjective and fraught with a high degree of inter-examiner variability. In a 2015 study, two examiners under identical conditions evaluated the pupils of consented patients. Over 2300 paired assessments were performed, followed by assessment with the pupillometer. The study showed only moderate inter-rater reliability between practitioners for pupil size, shape and reactivity. A major finding was that practitioners agreed less than half the time about non-reactive pupils, and more than 66% of the pupils scored as non-reactive by practitioners were actually reactive when measured by NPi Pupillometry.(74) Disagreement about non-reactive pupils can have significant consequences for the patient. This study and others support the use of automated pupillometry to improve the reliability and objectivity of pupillary assessment.

 

A quality improvement project, published by The University of Pittsburgh Medical Center, looked at adoption of the Pupillometer for routine care in a Neurotrauma ICU. This center reported that the Pupillometer led to increased confidence in the neurological examination, enhanced clinical decision making, and added value to patient care.(5)

 

Automated pupillometry provides completely accurate, reliable, and objective pupil data, independent of examiner, resulting in quality improvement for this important component of the neurological examination.

Adherence to Hospital Protocols/Reduction in Manual Entry Errors
Standard hospital protocols and guidelines for neurologically injured patients call for pupil assessments at regularly scheduled intervals. A typical nursing day with a critically ill patient requires coordination of care, diagnostic testing, frequent assessment and monitoring, medication administration, supporting the patient’s family, and many other complex and time-sensitive tasks. To save time and reduce errors often associated with manual data entry, patient data on the SmartGuard can be uploaded to the electronic medical record (EMR) system through coordination with your information technology (IT) and informatics teams. The pupillometer date and time stamp allow data review and trending from the time of admission throughout the patient’s hospital course, providing additional means to monitor compliance with protocols, guidelines, and quality initiatives.

Staffing: Cost and Time Savings

Automated pupillometry has been shown to decrease nursing workload associated with frequent pupillary assessment. To save valuable nursing time and resources, The University of Texas Southwestern Medical Center has successfully instituted a practice change in the Neuroscience ICU in which patient care technicians (unlicensed assistive personnel) obtain routine pupillometer measurements on designated patients. Results are reported to the assigned RN for interpretation and assessment of patient status.(92) In accordance with the state Board of Nursing and Nursing Practice Act, pupillometry measurements may be delegated to unlicensed assistive personnel with appropriate education.(92)

 

One study, illustrated below, showed that nurses saved on average 19.8 min per patient per day using automated pupillometry with direct data upload to the patient EMR.(102) Time saved by use of automated pupillometry increases with increasing frequency of serial pupillary examinations. This suggests that improvement in workforce efficiency by using automated pupillometers may translate into increased productivity and, ultimately, cost-saving benefits.(81, 92) As nursing leadership looks to improve efficiency in workflow and staffing, NPi Pupillometers at each bedside can assist in that effort.

Time Saving Example
Nursing Time Saved: Automated vs. Manual Pupil Assessment

Manual Pupil Assessment Technique

Manual pupil assessments (penlight) are subjective and fraught with a high degree of inter-examiner variability. It is well documented that automated pupillary assessment solves these problems, but manual pupil assessment can also take more time than automated pupillometry and little has been discussed about this.

A paired assessment with the pupillometer takes a clinician about 15 seconds. Manual pupil assessment can be confounded by several issues: Visual acuity of the examiner, dark eyes or small pupils of the patient, ambient light conditions and the subjectivity and skill/experience level of the examiner. As a result, in some patients, a clinician will often pass the penlight multiple times to try and confirm what he/she sees and a manual assessment can take even more time. In other cases, if the clinician is not sure, or if there is a suspected pupil change, another opinion might be sought. This involves an additional person and several minutes more of time. As a single measurement, these differences might not seem meaningful but given the frequency of pupil exams, these differences are significant over time.

Charting and Inputting Data
Some clinicians will complete the exam and immediately record the pupil measurement data into the terminal, while others will complete the pupil exam, continue with necessary patient care, and then later go to the terminal, log in, input the data and log out. Nurses at a high volume neuro ICU were recently timed and, on average, these charting and data entry steps took about one minute. Automatic data upload will eliminate the need to manually chart and input data.

Annual Cost Savings Example

Building an Effective Pupillometry Program

To achieve the benefits previously identified, successful adoption of pupillometry relies upon collaboration of a multidisciplinary team including nurses, providers, nursing leadership, biomedical engineering, IT, and supply chain management. Additionally, there are three key components to building an effective pupillometry program – eliminating barriers, establishing protocols and education.

 

Eliminating Barriers

Anticipating and eliminating barriers promotes successful adoption of new technology. Ensuring an appropriate number of and easy access to NPi Pupillometers based on unit size/layout is essential for optimizing nursing workflow and routine. Many hospitals dedicate one pupillometer to each patient room or one to every other room. A recent study showed that allocation of one pupillometer per patient room significantly improved compliance with pupillary assessment among nurses in the Neuro ICU.(89) A standardized process for ordering and stocking SmartGuards is equally important to ensure uninterrupted availability for patient care.

 

Another consideration is planning for documentation, including which values will be documented (typically pupil size and NPi) and in what format – paper flowsheet, fields added for manual EMR entry, or automatic upload. Examining their five-year experience with pupillometry and the ability to interface with the EMR, nurses across 6 different patient care units at University of California Irvine Health found that directly uploading pupillometer data to the EMR improved nursing workflow and improved documentation of pupillary findings and changes.(97) More information on EMR integration can be found at https://neuroptics.com/emr-integration/

Establishing Protocols
Much of the care provided to critically ill patients is driven by protocols based on evidence and best-practice guidelines. To standardize use and provide the most benefit to patients and clinicians, it is important to establish unit protocols and guidelines for use of the NPi Pupillometer. Essential components of a comprehensive protocol include 1) clear indications for use, including both primary neurological injuries as well as secondary indications (CA, ARDS, AMS etc); 2) a focus on baseline assessment at the time of admission and trending of values from subsequent exams; 3) procedural steps for use; and 4) guidelines for documentation and reporting abnormal values. Sample protocols are available from your NeurOptics representative for use when developing protocols or guidelines in your institution.

Education

Nursing and provider education are essential to the success of Pupillometer integration into clinical practice. NeurOptics stands ready to support education with local sales representatives and a network of RN Clinical Specialists. Together with clinical educators/managers and key personnel, NeurOptics works to develop a comprehensive day/night/weekend education plan according to institutional requirements. While on-site education is preferred, virtual education in a variety of formats can also be provided.

 

Initial education, at the time of pupillometer installation/rollout, focuses on operation of the NPi Pupillometer and conceptual understanding of its clinical use and benefits. Follow up education, scheduled four to six weeks later and periodically as needed, aims to reinforce operational skills and integration of pupillometry into routine clinical practice. Our education team is also available to support annual skills/competency days, Grand Rounds and other formal presentations.

 

NeurOptics provides and promotes many educational resources on the website (www.NeurOptics.com), including product information, instructional videos, webinar recordings, and clinical publications.

Appendix

Fig. 1 The NPi®-300 Pupillometer System with Wireless Charging Station and Incorporated Barcode Scanner

Please contact your local representative for more information on the features and availability of the NPi®-300 Pupillometer.

Fig. 2 Baseline and Trending with the Neurological Pupil index (NPi) Pupil Reactivity Assessment Scale

Fig. 3 Clinical Reference Texts and Guidelines Including Pupillometry and NPi

3a.

3b.

3c.

3a. American Association of Critical-Care Nurses. AACN Procedure Manual for Progressive and Critical Care. 8th edition. Johnson ed. Elsevier;2023:866-870.(10)

3b. American Association of Neuroscience Nurses. AANN Core Curriculum for Neuroscience Nursing. 7th edition. Littlejohns, McNett, Olson eds. AANN;2022:167-168.(12)

3c. Hickey JV, Strayer A. The Clinical Practice of Neurological and Neurosurgical Nursing. 8th edition. Wolters Kluwer; 2020:168-170.(37)

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