Case mix, outcomes and comparison of risk prediction models for admissions to adult, general and specialist critical care units for head injury: a secondary analysis of the ICNARC Case Mix Programme Database

Jonathan A Hyam,David A Harrison,Catherine A Welch,David K Menon

doi:10.1186/cc5066

Abstract

IntroductionThis report describes the case mix and outcome (mortality, intensive care unit (ICU) and hospital length of stay) for admissions to ICU for head injury and evaluates the predictive ability of five risk adjustment models.MethodsA secondary analysis was conducted of data from the Intensive Care National Audit and Research Centre (ICNARC) Case Mix Programme, a high quality clinical database, of 374,594 admissions to 171 adult critical care units across England, Wales and Northern Ireland from 1995 to 2005. The discrimination and calibration of five risk prediction models, SAPS II, MPM II, APACHE II and III and the ICNARC model plus raw Glasgow Coma Score (GCS) were compared.ResultsThere were 11,021 admissions following traumatic brain injury identified (3% of all database admissions). Mortality in ICU was 23.5% and in-hospital was 33.5%. Median ICU and hospital lengths of stay were 3.2 and 24 days, respectively, for survivors and 1.6 and 3 days, respectively, for non-survivors. The ICNARC model, SAPS II and MPM II discriminated best between survivors and non-survivors and were better calibrated than raw GCS, APACHE II and III in 5,393 patients eligible for all models.ConclusionTraumatic brain injury requiring intensive care has a high mortality rate. Non-survivors have a short length of ICU and hospital stay. APACHE II and III have poorer calibration and discrimination than SAPS II, MPM II and the ICNARC model in traumatic brain injury; however, no model had perfect calibration.

Highlights

This report describes the case mix and outcome (mortality, intensive care unit (ICU) and hospital length of stay) for admissions to intensive care units (ICUs) for head injury and evaluates the predictive ability of five risk adjustment models
We see that the relationship between Glasgow Coma Score (GCS) and mortality is more extreme for GCS measurements from the first 24 hours in ICU than for pre-sedation measurements
This study examines the outcomes of 11,021 head injury patients admitted to UK ICUs since 1995, and the predictive

Summary

Introduction

This report describes the case mix and outcome (mortality, intensive care unit (ICU) and hospital length of stay) for admissions to ICU for head injury and evaluates the predictive ability of five risk adjustment models. Head injury accounted for more than 120,000 admissions in England during 2000 to 2001, utilising over 320,000 bed days [2]. Ninety percent of head injuries seen in UK Accident and Emergency departments are mild, defined by the Royal Society of Rehabilitation Physicians as Glasgow Coma Score (GCS) 13 to 15 [3], 5% are moderate (GCS 9 to 12) and 5% are severe (GCS 3 to 8) [4]. Patients with severe head injury, in whom treatment is not deemed futile, are cared for in general or specialist intensive care units (ICUs). This is for a variety of reasons, most importantly because patients with a GCS below 9 need endotracheal intubation to protect their airway patency.

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