# A Reflection on Current Definitions of Critical Care and Critical Illness—A Narrative Review of the Literature

## TL;DR

This paper reviews current definitions of critical care, critical illness, and chronic critical illness to identify common themes and gaps in understanding.

## Contribution

The study provides a thematic synthesis of recent definitions and highlights the need to incorporate patient and professional experiences.

## Key findings

- Definitions of critical care emphasize population, interventions, timing, and complexity of care.
- Critical illness is often defined by future prevention and underlying pathophysiology.
- Chronic critical illness is characterized by duration, complications, and frailty.

## Abstract

Critical care and critical illness are key concepts that have been defined in various publications. A common understanding of the concepts is of great importance, but an up‐to‐date overview and discussion are lacking in the literature.

The aim of this study was to identify and discuss current definitions of critical care, critical illness and chronic critical illness.

We conducted a narrative review and performed literature searches in Medline, Cochrane Library, CINAHL, Embase, LIVIVO, Google Scholar, OpenGrey, Epistemonikos and Science Open as well as citation searching from July 2024 to September 2025. Reports on definitions were included if they dealt thematically with critical care, critical illness or chronic critical illness, were published within the last 10 years and were available in German or English. Data synthesis followed an inductive approach. We thematically analysed the core concepts of identified definitions, formed thematic clusters and finally approved them in multiple group discussions.

In total, 13 definitions of critical care, eight definitions of critical illness and 12 definitions of chronic critical illness were identified. Key components of critical care are the population, interventions, timing, professionals, aim, location and complexity. Critical illness is mainly characterised by future aspects and prevention, underlying causes and treatment. Chronic critical illness is determined by its duration, several complications and frailty. All three terms share the temporality and severity of a disease. Included definitions have a pronounced pathophysiological focus; they point to highly complex and technologised treatment pathways.

Current definitions show a generally homogeneous understanding of the care for critically ill patients. To ensure a comprehensive representation, definitions need to be adapted and consider the experiences of those involved.

The analysed clusters of the definitions of critical care, critical illness and chronic critical illness help professionals to develop their terminology and reflect on their clinical approaches.

Internationally, there are various definitions of critical care and critical illness.There is now a large body of literature and empirical research on these terms.

Internationally, there are various definitions of critical care and critical illness.

There is now a large body of literature and empirical research on these terms.

The definitions of critical care, critical illness and chronic critical illness are heterogeneous in their extent, application and evidence basis.Existing definitions primarily focus on urgency and timing, humans' pathophysiological deterioration and a complex treatment situation.The experience of patients, relatives and professionals has hardly been considered to date.

The definitions of critical care, critical illness and chronic critical illness are heterogeneous in their extent, application and evidence basis.

Existing definitions primarily focus on urgency and timing, humans' pathophysiological deterioration and a complex treatment situation.

The experience of patients, relatives and professionals has hardly been considered to date.