ASA helps prediction of the death rate in surgical ICU patients

Introduction

Many scoring systems have been designed to predict mortality in surgical patients; however, these systems require the collection of several parameters that may not be available at ICU admission. As a result, these classification systems are not used as a routine part of clinical practice. The aim of this study was to evaluate the prognostic value of ASA classification predicting ICU and hospital mortality.

Methods

We analyzed the records of 11,230 ICU admissions. ASA and elective/nonelective nature of the admission were combined into eight categories. We used the chi-square test and accepted the null hypothesis if P > 0.05. Areas under the ROC curve using ASA and ASA/ admission categories were constructed.

Results

We included 5,998 patients admitted to the ICU immediately after surgery. Forty-one percent were older than 65 years and 51% were female. Length of stay previous to ICU admission was 2.5 ± 6.1 days and duration of ICU stay was 1.9 ± 2.4 days. Elective hospital admission occurred in 65% of the patients. Neurosurgery with 21% of the procedures was followed by abdominal surgery (20%), and orthopedic surgery (15%). The death rate at the hospital was 6.9% (2.8% in ASA I patients and 31% in ASA IV/E). Higher ASA classification was significantly associated with the death rate both in the ICU and at the hospital (P < 0.00001). The nonelective nature of the hospital admission was also associated with higher risk of death at the ICU (P < 0.0001) and in the hospital (P < 0.0001). Gender and hour of admission was not associated with the death rate. The combination of ASA classification with the nonelective nature of the hospital admission produced an eight- category index significantly associated with mortality (P< 0.00001). Analyzing hospital mortality, the area under the ROC curve was 0.77 (95% CI 0.74 to 0.79) for this index and was 0.72 (95% CI 0.69 to 0.75) for ASA. When analyzed for death at the ICU the AUROC was 0.71 (95% CI 0.69 to 0.75, P < 0.0001) for ASA and 0.75 (95% CI 0.71 to 0.78, P < 0.0001) for ASA nonelective admission index.

Conclusion

These results show that the ASA index can be used, preferably in combination with other data from electronic records, to predict mortality for surgical ICU patients.