Severity of illness and risk of death associated with pulmonary artery catheter use

Objective: To examine the association between the use of the pulmonary artery catheter and mortality rate in critically ill patients with a higher vs. a lower severity of illness. Design: Observational cohort study. Setting: A tertiary care university teaching hospital from March 1988 to March 1998. Patients. A total of 7,310 critically ill adult patients. Interventions: None. Measurements and Main Results: The main outcome measure was hospital mortality rate, controlled by multivariable logistic regression within four patient groups based on severity of illness. Cutoffs for severity of illness were chosen based on Acute Physiology and Chronic Health Evaluation (APACHE) II score 25th percentiles. Logistic regression analysis demonstrated no increased risk of death associated with exposure to the pulmonary artery catheter in the population as a whole. The associated odds ratio of hospital death for the entire cohort was 1.05 (95% confidence interval, 0.92-1.21). Subgroup analysis of severity of illness revealed the highest risk of death to be associated with the lowest APACHE II score quartile vs. a decreased associated mortality rate with the highest APACHE II score quartile after adjustment with multivariable logistic regression (APACHE II <18: odds ratio, 2.47, 95% confidence interval, 1.27-4.81; APACHE II 18-24: odds ratio, 1.64, 95% confidence interval, 1.24-2.17; APACHE II 25-31: odds ratio, 1.00, 95% confidence interval, 0.80-1.24; APACHE II >31: odds ratio, 0.80, 95% confidence interval, 0.64-1.00). Conclusions: The use of the pulmonary artery catheter may decrease mortality rate in the most severely ill while increasing it in a population with a lower severity of illness. These findings underscore the necessity of examining the effect of severity of illness in future randomized controlled trials.