This study is no longer recruiting participants.


Cardiac arrest is often categorised by location, out-of-hospital or in-hospital (IHCA), as there are important differences in population characteristics and aetiology. The National Cardiac Arrest Audit (NCAA) was established to audit resuscitation teams in response to IHCA, and collects information about patient characteristics, resuscitation processes, and patient outcomes. However, it does not audit IHCAs that are not attended by the resuscitation team.

Critically ill patients managed in ICUs are experiencing failure of one or more organs and therefore more intensive and invasive therapies are needed to support these failing organs. As a result, ICUs have higher nursing and medical staffing ratios, and monitoring is usually continuous. Moreover, the skill mix of the multidisciplinary team is geared to advanced life support. Thus, the risk of cardiac arrest occurring, the involvement (or not) of the resuscitation team, and the probability of return of spontaneous circulation are all likely to be different to other IHCAs.

Accurate data on cardiac arrests in ICU are lacking and we do not know how many IHCA occur in ICU in the UK, nor do we know the impact of an IHCA in ICU on outcome. In addition, we do not know if these IHCAs in ICUs represent an unavoidable consequence of critical illness or, more importantly, whether they can be predicted and/or prevented.


The CIRCA study aims to determine, in a prospective, multi-centre observational cohort study, the incidence and outcomes of IHCA in UK ICUs and explore associated risk factors with ICU and hospital survival and quality of survival following hospital discharge. The study is nested in the Case Mix Programme and NCAA national clinical audits and data will be collected from 100 adult, general, critical care units over a 12 month period. 

Data collection for this study was run from January 2020 to June 2021.

Key information

Chief investigator(s)

Dr Matt Thomas, North Bristol NHS Trust


Intensive Care National Audit & Research Centre (ICNARC)

Trial registration(s) NCT04219384

NIHR Central Portfolio Management System: 43238

Contact information

Trial Manager: Robert Darnell


Phone: 020 7269 9277

Trial protocol
Statistical analysis plan
Resuscitation council UK