The Acute Physiology and Chronic Health Evaluation III Outcome Prediction in Patients Admitted to the Intensive Care Unit After Pneumonectomy

Abstract

The Acute Physiology and Chronic Health Evaluation (APACHE) III prognostic system has not been previously validated in patients admitted to the intensive care unit (ICU) after pneumonectomy. The purpose of this study was to determine if the APACHE III predicts hospital mortality after pneumonectomy. A retrospective review of all adult patients admitted to a single thoracic surgical intensive care unit after pneumonectomy between October 1994 and December 2004. Patient demographics, ICU admission day APACHE III score, actual and predicted hospital mortality, and length of hospital and ICU stay data were collected. Data on preoperative pulmonary function tests and smoking habits were also collected. Univariate statistical methods and logistic regression were used. The performance of the APACHE III prognostic system was assessed by the Hosmer-Lemeshow statistic for calibration and area under receiver operating characteristic curve (AUC) for discrimination. There were 417 pneumonectomies performed during the study period, of which 281 patients were admitted to the ICU. The mean age was 61.1 years, and 67.2% were men; 88.2% were smokers with a median of 40.0 (interquartile range, 18-62) pack-years of tobacco use. The mean APACHE III score on the day of ICU admission was 37.7 (+/- standard deviation 17.8), and the mean predicted hospital mortality rate was 6.4% (+/-10.4). The median (and interquartile range) lengths of ICU and hospital stay were 1.7 (0.9-3.1) and 9.0 (7.0-17.0) days, respectively. The observed ICU and hospital mortality rates were 4.6% (13/281 patients) and 8.2% (23/281), respectively. The standardized ICU and hospital mortality ratios with their 95% confidence intervals (CIs) were 1.55 (0.71-2.39) and 1.27 (0.75-1.78), respectively. There were significant differences in the mean APACHE III score (p < 0.001) and the predicted mortality rate (p < .001) between survivors and nonsurvivors. In predicting mortality, the AUC of APACHE III prediction was 0.801 (95% CI, 0.711-0.891), and the Hosmer-Lemeshow statistic was 9.898 with a p value of 0.272. Diffusion capacity of the lung for carbon monoxide (DLCO) and percentage predicted DLCO were higher in survivors, but the addition of either of these variables to a logistic regression model did not improve APACHE III mortality prediction. In patients admitted to the ICU after pneumonectomy, the APACHE III discriminates moderately well between survivors and nonsurvivors. The calibration of the model appears to be good, although the low number of deaths limits the power of the calibration analysis. The use of APACHE III data in outcomes research involving patients who have undergone pneumonectomy is acceptable.