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NCT Number: NCT06964997

Anisocoria in the Intensive Care Unit (AICU Study)

This retrospective single-center cohort study aims to determine the prevalence of acute "new onset" pupillary abnormalities in adult intensive care unit patients, assess their clinical impact, identify the contexts leading to treatment changes, and evaluate their prognostic implications.

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Key information

Conditions

Anisocoria Eye Diseases Nervous System Diseases Neurologic Manifestations Pathological Conditions, Signs and Symptoms Pupil Disorders Signs and Symptoms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

University Hospital Basel, Clinic for Intensive Care Medicine

Basel, Canton of Basel-City, 4031, Switzerland

About this study

Assessment of the pupil symmetry and reactivity to light are important parts of the neurological evaluation of critically ill patients in intensive care units (ICUs). Anisocoria, a condition where the pupils are unequal in size, can be found in up to 60% of patients with acute neurologic injuries. It may indicate serious underlying issues like traumatic brain injury, cerebrovascular accidents, brain tumors or viral encephalitis. However, anisocoria or impaired pupillary reactivity can also be caused from less severe conditions, such as drug effects (e.g., ipratropium bromide),Horner's syndrome after central venous cannulation, or intoxications with substances like anticholinergics, opioids, and cannabinoids. Despite these well-known causes, there is limited data on the prevalence and clinical consequences of anisocoria in ICU patients.

New onset of pupillary abnormalities often requires immediate neurological evaluation and neuroimaging (computed tomography (CT) or magnetic resonance imaging (MRI)), but many of these scans may not reveal clinically relevant findings and could expose patients to unnecessary risks. This is particularly concerning as benign causes of pupillary abnormalities are common, while more serious conditions can sometimes be overlooked. Current studies do not fully address when CT or MRI scans are necessary, or when they provide no significant clinical benefit.

This retrospective single-center cohort study has four primary objectives:

  • to determine the prevalence of acute "new onset" pupillary abnormalities (anisocoria and/or impaired light-reactive pupillary response) in adult ICU patients.
  • to assess the clinical impact of these abnormalities, particularly in terms of the frequency of diagnostic tests like CT or MRI scans, and ophthalmologic and neurologic consultations.
  • to identify when pathological findings lead to treatment modifications
  • to evaluate the prognostic implications of these pupillary abnormalities on patient outcomes.

The results of this study may improve the understanding of acute pupillary abnormalities in ICU patients, helping to optimize diagnostic strategies, reduce unnecessary neuroimaging, and enhance patient safety and outcome prediction.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adult patients (i.e., patients ≥18 years of age)
  • Reported incident of pupillary abnormality (either anisocoria or non-normal pupillary reactivity) in the intensive care unit at the University Hospital Basel between 2013-2024.

Exclusion criteria

  • Patients younger than 18 years
  • Patients with documented refusal of data use.

Treatment and study plan

Primary outcomes

  1. Acute prehospital management data

    Time frame: 2013-2024

    Data from acute prehospital management, as documented in emergency medical services (EMS) treatment protocols, is collected. The collected data elements are aggregated to describe the overall EMS response.

  2. Duration of intensive care unit stay

    Time frame: 2013-2024

    The length of intensive care unit (ICU) stay is recorded.

  3. Duration of hospital stay

    Time frame: 2013-2024

    The length of the total hospital stay is recorded.

  4. Discharge destination

    Time frame: 2013-2024

    The destination at discharge is recorded.

  5. Date of incident

    Time frame: 2013-2024

    The date when acute "new onset" pupillary abnormalities were first documented in patient records is recorded.

  6. Characteristics of incident

    Time frame: 2013-2024

    Details on the pupillary abnormality as described in nurses' and physicians' progress notes (e.g. wording) to characterize the condition.

  7. Type of incident

    Time frame: 2013-2024

    The type of pupillary abnormality (anisocoria, areactivity, or altered reaction to light) is recorded.

  8. Additional features of the incident

    Time frame: 2013-2024

    Assessment of additional features related to incident of pupillary abnormality (shift type, time of day (daytime or nighttime), and environment). These features are aggregated to characterize the context in which the assault occurred.

  9. Patient characteristics

    Time frame: 2013-2024

    Information on the patient (e.g., principal diagnosis, comorbidities, medication) is documented.

  10. Consequences of the Incident

    Time frame: 2013-2024

    Evaluation of medical assessments and interventions following the incident, including Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scans, ophthalmologic or neurologic consultations.

  11. Comprehensive assessment of the neurological status based on validated clinical assessment

    Time frame: 2013-2024

    Neurological status during ICU stay is assessed using available data in the patient register from validated neurological assessments. These may include the Richmond Agitation-Sedation Scale (RASS), Sedation-Agitation Scale (SAS), Glasgow Coma Scale (GCS), Intensive Care Delirium Screening Checklist (ICDSC), or Status Epilepticus Severity Score (STESS). The specific tool used, as well as the scale of the score and meaning behind the score, depends on routine clinical practice and available documentation in the register. If multiple scores are available for a patient, they will be aggregated to provide a comprehensive assessment of neurological status. This outcome will be reported as a descriptive summary, synthesizing findings across tools, rather than as a single quantitative score.

  12. Comprehensive assessment of critical illness severity based on standardized scoring systems

    Time frame: 2013-2024

    Disease severity during ICU stay is assessed using standardized scoring systems, including the Acute Physiology and Chronic Health Evaluation II (APACHE II), Simplified Acute Physiology Score II (SAPS II), and Sequential Organ Failure Assessment (SOFA), depending on data availability in the patient register. The specific scoring system applied, as well as the scale and interpretation of the score, varies based on routine clinical practice and available documentation. Where multiple severity scores are available, they will be synthesized to provide a descriptive summary of overall illness severity rather than a single quantitative score.

  13. Charlson Comorbidity Index

    Time frame: 2013-2024

    The Charlson Comorbidity Index (CCI) is calculated based on pre-existing comorbidities and additional diagnoses. The CCI predicts the ten-year mortality for a patient who may have a range of comorbid conditions. It assigns weighted scores (from 0 to maximal 6) to 17 comorbid conditions (e.g., heart disease, diabetes, cancer), resulting in a total score ranging from 0 to 33, if the patient had the most severe form of each of the 17 conditions.

  14. Laboratory parameters

    Time frame: 2013-2024

    Routine laboratory value for e.g. C-Reactive Protein (CRP), albumin, Lactate Dehydrogenase (LDH), Creatine Kinase (CK), procalcitonin, white blood cell levels, creatinine, liver enzymes, blood gas analyses, metabolic data, and toxicologic screenings, is collected. The specific parameters recorded may vary depending on the laboratory assessments documented in the patient register. All values will be reported using their respective units of measurement.These parameters are aggregated to support an overall clinical interpretation rather than a single numerical value. This approach reflects standard clinical practice, where multiple lab values are considered together to assess a patient's condition.

  15. Glasgow Outcome Score

    Time frame: 2013-2024

    The Glasgow Outcome Score (GOS) is calculated based on the assessment of key clinical outcomes such as inhospital mortality, survival, survival with neurofunctional alteration, return to premorbid neurological function, and hospital readmission to determine the patient outcome.

    The GOS ranges from 1 (death) to 5 (good recovery).

  16. Therapeutic intervention

    Time frame: 2013-2024

    The therapeutic intervention is document, including information on duration, dosage and number of treatment medication, number of neuroleptic, sedative and analgesic drugs, use of ipratropium bromide, invasive procedures, such as intubation, mechanical, ventilation, vasopressors, installation of central lines, i.v. thrombolysis, endovascular thrombectomy, surgical hemicraniectomy, insertion of ventricular drains, intracranial pressure monitoring, i.v. administration of mannitol or saline, nutrition, etc.

  17. Vital signs

    Time frame: 2013-2024

    Vital signs are analyzed based on the data available in the patient register. These may include blood pressure, heart rate, respiratory rate, oxygen saturation, body temperature, level of consciousness, intracranial pressure, and drainage rate of cerebrospinal fluid. The specific parameters recorded depend on the clinical documentation available. All values will be reported using their respective units of measurement. These values are aggregated to support an overall clinical assessment rather than a single numerical score. This reflects standard practice, where multiple vital signs are interpreted together to evaluate a patient's condition.

  18. Fluid balance data

    Time frame: 2013-2024

    Fluid balance data, including the administration of fluids such as blood products, crystalloids, and enteral/parenteral nutrition, are documented. These components are aggregated to represent overall fluid input for each patient.

Sponsors and collaborators

Lead sponsor

University Hospital, Basel, Switzerland

Other

Registry information

Official study title

Anisocoria in the ICU (AICU Study): Diagnostic Implications and Clinical Outcomes

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
May 11, 2025
Registry last updated
Jun 17, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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