[Analysis of outcome quality control in intensive care medicine using the Simplified Acute Physiology Score II]

Abstract

Aim: the main aim of the study was to assess the applicability of the Simplified Acute Physiology Score II (SAPS II) to the evaluation of outcome quality within the framework of quality assurance in patients in a medical intensive care unit. The outcome parameter employed was hospital mortality, measured as mortality index (hospital mortality actually observed/predicted mortality), the predicted mortality being derived from the individual mortality risk calculated for each patient in accordance with SAPS II.

Method: For the period of one year, the SAPS II score, the individual mortality risk, the mean scores, mortality risk, intensive care and hospital mortality, and the mortality index (99% confidence interval) were calculated with the aid of a specially developed program for all 1,114 patients kept under observation or treated for longer than 4 hours in the intensive care unit. The entries (data) were monitored by random checks for the correctness of the individual entries and overall completeness of patient inclusion. The applicability of the SAPS II for our own patient material was checked with the aid of Receiver Operating Characteristic curves. In compliance with the original SAPS II to include patients of a coronary care unit but not to evaluate them, only the 604 patients with the diseases of medical intensive care were taken into account for quality control. High-risk groups (patients older than 76, critically ill patients with a mortality risk of more than 0,5, patients receiving respiratory support) and individual diagnostic categories were considered separately as subgroups.

Results: In the entire group, the mean mortality risk was 21,1% the observed intensive care mortality 11,2%, the hospital mortality 18,0%, and the mortality index 0,86 (0,75 to 1,00). The mortality actually observed, therefore, corresponded to that predicted on the basis of the SAPS prognostic system. Also in the subgroups of elderly patients, and individual diagnostic categories (cerebral, bronchopulmonary cardiovascular, gastrointestinal diseases), the mortality index did not differ significantly from 1,0. A mortality index significantly less than 1,0 (observed mortality significantly lower than predicted mortality) was found in the sub-groups of the seriously ill, of patients receiving respiratory support, and in the diagnostic category of intoxications. The monthly analysis showed fluctuating mortality indices which, however, never differed significantly from 1,0. The surface under the ROC curve for the entire group was 0,89, and 0.81-0.99 for the various diagnostic categories.

Conclusions: The prognostic system SAPS II can be employed to evaluate the quality of outcome measured by hospital mortality in patients of a medical intensive care unit, provided that the applicability of the score is demonstrated for the patient material involved, the outcome of the overall group and of the high-risk groups is referred to the accuracy and completeness of the entered data is checked, and the scoring systems accepted as quality standard.