Co-morbidity, demographic and social factors as predictors of outcome from intensive care: an observational cohort study

Introduction

Critically ill patients arrive in intensive care with various degrees of impairment in chronic health. These are recognised to have an impact upon survival and the Acute Physiology and Chronic Health Evaluation II (APACHE II) system utilises this when predicting mortality. We wished to look at the impact of many of these factors upon outcome from our intensive care.

Methods

A prospective case-note review of 500 consecutive admissions to Glasgow Royal Infirmary ICU was undertaken over an 18-month period. Details of co-morbidity, social factors, regular medication and exercise tolerance were sought from the patients' case notes by hand using details of current and previous admissions, clinic letters, results of investigations and correspondence from the patient's general practitioner, using agreed criteria. Demographic, APACHE II score and outcome data were retrieved from the Ward Watcher system in the ICU. Data were analysed using a univariate analysis model and chi-square test.

Results

Complete data were available for 500 patients. Population demographics were as follows - 65% male, mean age 53.8 ± 4.1 years, median APACHE II score 18 (IQR 12 to 24), crude ICU mortality 33.6%. The following factors were associated with an increased mortality (odds ratio, P value): age >50 years (OR 3.11, P < 0.001), cigarette smoking (OR 1.57, P = 0.02), NYHA class 3/4 (OR 2.52, P < 0.001), ischaemic heart disease (OR 1.70, P = 0.01), peripheral vascular disease (OR 1.91, P = 0.04), chronic obstructive pulmonary disease (OR 2.56, P < 0.001), alcoholic liver disease (OR 3.86, P < 0.001). The following factors were not significantly associated with increased mortality: male gender, social deprivation, unemployment, alcohol excess, intravenous drug use, polypharmacy, hypertension, diabetes, obesity or concurrent malignancy.

Conclusions

These results suggest significant increased ICU mortality in the following groups: over 50 years old, smokers, patients with poor exercise tolerance, patients with IHD or PV, patients with COPD and patients who drink alcohol to excess or those with ALD. While these results should not be used as a basis upon which to permit or refuse intensive care admission, they should be used to inform staff and patients of likely outcome from intensive care.