Association between the neurological pupil index and the cause of altered level of consciousness in the emergency department: a cross-sectional observational study

Altered level of consciousness (ALC) is a common chief complaint during emergency department (ED) visits, with a broad spectrum of disease causes. The neurological pupil index (NPI) is an objective method for assessing the pupillary light reflex (PLR) by measuring pupil-related indices in patients with ALC. This study hypothesized that NPI values would differ according to the cause of ALC and aimed to determine the association between NPI values and the cause of ALC in patients admitted to the ED. Patients with a chief complaint of ALC or those who presented with signs of ALC as perceived by healthcare providers in the ED were enrolled. The main exposure was the NPI value measured in the ED at either the arrival time or when ALC was first detected and 1 hour after the initial NPI check. The primary outcome was ALC etiology, which included non-brain and brain causes. Multivariable logistic regression analysis was performed to test the association between the NPI value and cause of ALC. A total of 607 patients were analyzed. The proportions of non-brain vs. brain causes in the initial NPI <3 and initial NPI ≥3 groups were 52.4% vs. 36.1% and 66.4% vs. 17.2%, respectively. The proportions of non-brain vs. brain causes in the 1-hour NPI <3 and 1-hour NPI ≥3 groups were 46.2% vs. 41.8% and 68.4% vs. 15.6%, respectively. In the multivariable logistic regression analysis, the adjusted odds ratio (AOR) of initial NPI ≥3 was 2.28 and 0.27 for non-brain and brain causes. The AORs of 1-hour NPI ≥3 for non-brain and brain causes were 2.75 and 0.21, respectively. If the initial and 1-hour NPIs are <3, the ALC is likely caused by brain-related issues. Conversely, if the initial and 1-hour NPIs are ≥3, the ALC is likely caused by non-brain-related issues.

Neurological pupil index; Consciousness; Etiology; Emergency department

[1] Smith A, Han J. Altered Mental Status in the Emergency Department. Seminars in Neurology. 2019; 39: 5–19.

[2] Salani D, Valdes B, De Oliveira GC, King B. Psychiatric emergencies: emergency department management of altered mental status. Journal of Psychosocial Nursing and Mental Health Services. 2021; 59: 16–25.

[3] Kalish VB, Gillham JE, Unwin BK. Delirium in older persons: evaluation and management. American Family Physician. 2014; 90: 150–158.

[4] Khan UH, Mantoo S, Dhar A, Shabir A, Shah A, Mehfooz N, et al. Vitamin D toxicity presenting as altered mental status in elderly patients. Cureus. 2022; 14: e32654.

[5] Villafane J, Miller JR, Glickstein J, Johnson JN, Wagner J, Snyder CS, et al. Loss of consciousness in the young child. Pediatric Cardiology. 2021; 42: 234–254.

[6] Choi DH, Hong KJ, Do Shin S, Kim S, Chung M, Kim KH, et al. Measurement of level of consciousness by AVPU scale assessment system based on automated video and speech recognition technology. The American Journal of Emergency Medicine. 2023; 74: 112–118.

[7] Kim KT, Jeon JC, Jung CG, Park JA, Seo JG, Kwon DH. Etiologies of altered level of consciousness in the emergency room. Scientific Reports. 2022; 12: 4972.

[8] Adan Ali H, Farah Yusuf Mohamud M. Epidemiology, risk factors and etiology of altered level of consciousness among patients attending the emergency department at a tertiary hospital in Mogadishu, Somalia. International Journal of General Medicine. 2022; 15: 5297–5306.

[9] Moussa BS, Abd Elatiff ZM, Kamal Eldin Elhadary GM. Survey study of the etiology of non-traumatic altered consciousness in the Emergency Department at Suez Canal University Hospital in Egypt. World Journal of Clinical Cases. 2023; 11: 1310–1317.

[10] Aguilar-Fuentes V, Orozco-Puga P, Jiménez-Ruiz A. The Glasgow Coma Scale: 50-year anniversary. Neurological Sciences. 2024; 45: 2899–2901.

[11] Brunker C, Harris R. How accurate is the AVPU scale in detecting neurological impairment when used by general ward nurses? an evaluation study using simulation and a questionnaire. Intensive and Critical Care Nursing. 2015; 31: 69–75.

[12] Fava GA, Tomba E, Sonino N. Clinimetrics: the science of clinical measurements. International Journal of Clinical Practice. 2012; 66: 11–15.

[13] Kim DW, Jo YH, Park SM, Lee DK, Jang DH. Neurological pupil index during cardiopulmonary resuscitation is associated with admission to ICU in non-traumatic out-of-hospital cardiac arrest patients. Signa Vitae. 2023; 19; 48–54.

[14] Stutzman S, Iype P, Marshall J, Speir K, Schneider N, Tran C, et al. Inter-device reliability of the NPi-200 and NPi-300 pupillometers. Journal of Clinical Neuroscience. 2022; 100: 180–183.

[15] Kim TJ, Park SH, Jeong HB, Ha EJ, Cho WS, Kang HS, et al. Neurological pupil index as an indicator of neurological worsening in large hemispheric strokes. Neurocritical Care. 2020; 33: 575–581.

[16] Ghauri MS, Ueno A, Mohammed S, Miulli DE, Siddiqi J. Evaluating the reliability of neurological pupillary index as a prognostic measurement of neurological function in critical care patients. Cureus. 2022; 14: e28901.

[17] Oddo M, Taccone FS, Petrosino M, Badenes R, Blandino-Ortiz A, Bouzat P, et al. The neurological pupil index for outcome prognostication in people with acute brain injury (ORANGE): a prospective, observational, multicentre cohort study. The Lancet Neurology. 2023; 22: 925–933.

[18] Privitera CM, Neerukonda SV, Aiyagari V, Yokobori S, Puccio AM, Schneider NJ, et al. A differential of the left eye and right eye neurological pupil index is associated with discharge modified Rankin scores in neurologically injured patients. BMC Neurology. 2022; 22: 273.

[19] Hall CA, Chilcott RP. Eyeing up the future of the pupillary light reflex in neurodiagnostics. Diagnostics. 2018; 8: 19.

[20] McKay RE, Larson MD. Detection of opioid effect with pupillometry. Autonomic Neuroscience. 2021; 235: 102869.

[21] Kongsgaard UE, Hoiseth G. Dynamic assessment of the pupillary reflex in patients on high-dose opioids. Scandinavian Journal of Pain. 2019; 19: 465–471.

[22] Feske SK. Ischemic stroke. The American Journal of Medicine. 2021; 134: 1457–1464.

[23] Marcolini E, Stretz C, DeWitt KM. Intracranial hemorrhage and intracranial hypertension. Emergency Medicine Clinics of North America. 2019; 37: 529–544.