Acute respiratory distress syndrome: an audit of incidence and outcome in Scottish intensive care units.

This prospective audit of incidence and outcome of the acute respiratory distress syndrome was conducted as part of the national audit of intensive care practice in Scotland. All patients with acute respiratory distress syndrome in 23 adult intensive care units were identified using the diagnostic criteria defined by the American-European Consensus Conference. Daily data collection was continued until death or intensive care unit discharge. Three hundred and sixty-nine patients were diagnosed with acute respiratory distress syndrome over the 8-month study period. The frequency of acute respiratory distress syndrome in the intensive care unit population was 8.1%; the incidence in the Scottish population was estimated at 16.0 cases.100,000(-1).year(-1). Intensive care unit mortality for acute respiratory distress syndrome was 53.1%, with a hospital mortality of 60.9%. In our national unselected population of critically ill patients, the overall outcome is comparable with published series (Acute Physiology and Chronic Health Evaluation II standardised mortality ratio = 0.99). However, mortality from acute respiratory distress syndrome in Scotland is substantially higher than in recent other series suggesting an improvement in outcome in this condition.

Outcome of long-stay intensive care patients.

OBJECTIVES: To assess the numbers, characteristics and outcome for patients requiring long-term intensive care. DESIGN AND SETTING: Observational cohort study in 23 Scottish intensive care units over a 3-year period. PATIENTS AND PARTICIPANTS: 323 patients with an ICU stay of 30 days or more. MEASUREMENTS AND RESULTS: Although representing only 1.6% of patients, those with long stays occupied 15.7% of bed-days. Hospital survival among these patients was 59.9%. With the available data it was not possible to discriminate survivors from non-survivors. CONCLUSIONS: Since these patients have a relatively high hospital survival, resources should not be withheld from them on the basis of prolonged ICU stay alone, even in countries with limited ICU provision.

Renal and respiratory failure in Scottish ICUs.

The purpose of this study was to define the outcome of patients receiving both renal replacement therapy and mechanical ventilation in 16 Scottish intensive care units over a 2-year period. Patients were identified from the Scottish Intensive Care Society's database. Survivors developing end-stage renal failure were identified after examination of the Scottish Renal Registry's database. Mortality was 64.2% (392/612) for all patients receiving renal replacement therapy and mechanical ventilation. End-stage renal failure developed in 1.6% (3/188) of the survivors of acute renal failure and in 33% (4/11) of the survivors with pre-existing chronic renal failure. Mortality has not improved when compared with earlier studies. End-stage renal failure rarely develops following acute renal failure in the intensive care unit.

Evaluation of predicted and actual length of stay in 22 Scottish intensive care units using the APACHE III system. Acute Physiology and Chronic Health Evaluation.

The most recent edition of the Acute Physiology and Chronic Health Evaluation provides a prediction of intensive care unit length of stay in addition to the probability of hospital mortality. Intensive care length of stay is an important determinant of intensive care costs and may be an important indicator of quality of care. Data were collected from 22 Scottish intensive care units over a 2-year period to allow comparison of actual intensive care unit length of stay with that predicted by the Acute Physiology and Chronic Health Evaluation III system. Correlation between actual and predicted stay for individual patients was poor. However, performance of the model for patients, grouped either by predicted length of stay or by intensive care unit, indicated that the model stratified patient groups appropriately while demonstrating a consistent bias. Length of stay in Scottish intensive care units was found to be consistently lower than that predicted by a model which is based on intensive care practice in the USA. Variations in severity of illness in intensive care unit populations cannot readily explain differences in intensive care unit length of stay. The availability of a model capable of predicting length of intensive care stay, based on data reflecting practice in the UK, would compliment current methods of assessing effectiveness of intensive care.

Assessment of the performance of five intensive care scoring models within a large Scottish database.

OBJECTIVE: To assess and compare the performance of five severity of illness scoring systems used commonly for intensive care unit (ICU) patients in the United Kingdom. The five models analyzed were versions II and III of the Acute Physiology and Chronic Health Evaluation (APACHE) system, a version of APACHE II using United Kingdom (UK)-derived coefficients (UK APACHE II), version II of the Simplified Acute Physiology Score (SAPS), and version II of the Mortality Probability Model, computed at admission (MPM0) and after 24 hrs in the ICU (MPM24). DESIGN: A 2-yr prospective cohort study of consecutive admissions to intensive care units. SETTING: A total of 22 general ICUs in Scotland PATIENTS: A total of 13,291 admissions to the study, which after prospectively agreed exclusions left a total of 10,393 patients for the analysis. OUTCOME MEASURES: Death or survival at hospital discharge. MEASUREMENTS AND MAIN RESULTS: All the models showed reasonable discrimination using the area under the receiver operating characteristic curve (APACHE III, 0.845; APACHE II, 0.805; UKAPACHE II, 0.809; SAPS II, 0.843; MPM0, 0.785; MPM24, 0.799). The levels of observed mortality were significantly different than that predicted by all models, using the Hosmer-Lemeshow goodness-of-fit C test (p < .001), with the results of the test being confirmed by calibration curves. When excluding patients discharged in the first 24 hrs to allow for comparisons using the same patient group, APACHE III, MPM24, and SAPS II (APACHE III, 0.795; MPM24, 0.791; SAPS II, 0.784) showed significantly better discrimination than APACHE II, UK APACHE II, and MPM0 (APACHE II, 0.763; UK APACHE II, 0.756; MPM0, 0.741). However, calibration changed little for all models with observed mortality still significantly different from that predicted by the scoring systems (p < .001). For equivalent data sets, APACHE II demonstrated superior calibration to all the models using the chi-squared value from the Hosmer-Lemeshow test for both populations (APACHE III, 366; APACHE II, 67; UKAPACHE II, 237; SAPS II, 142; MPM0, 452; MPM24, 101). CONCLUSIONS: SAPS II demonstrated the best overall performance, but the superior calibration of APACHE II makes it the most appropriate model for comparisons of mortality rates in different ICUs. The significance of the Hosmer-Lemeshow C test in all the models suggest that new logistic regression coefficients should be generated and the systems retested before they could be used with confidence in Scottish ICUs.

Should the pre-sedation Glasgow Coma Scale value be used when calculating Acute Physiology and Chronic Health Evaluation scores for sedated patients? Scottish Intensive Care Society Audit Group.

OBJECTIVE: To assess the effect on the performance of Acute Physiology and Chronic Health Evaluation (APACHE) II and APACHE III of two different approaches to scoring the Glasgow Coma Scale (GCS) in sedated patients. The first approach was to assume that the GCS score was normal, and the second was to use the GCS value recorded before the patient was sedated. DESIGN: Prospective cohort study over 2 yrs. SETTING: Twenty-two general adult intensive care units in Scotland. PATIENTS: 13,291 consecutive admissions to the participating intensive care units. MEASUREMENTS AND MAIN RESULTS: After exclusion of patients according to standard, predefined criteria, the Acute Physiology and Chronic Health Evaluation II and III systems were used to calculate the probability of hospital mortality for patients included in the study. In patients whose GCS scores could not be assessed accurately during the first 24 hrs, the APACHE II and III predictions were calculated twice: first, assuming that the GCS score was normal; and second, substituting the GCS score recorded before sedation. This generated two different databases for each system, and the predictions for both were compared with the observed hospital mortality rate. The effect of the two different approaches to the GCS on the performance of both APACHE II and APACHE III was assessed using measures of discrimination (area under the receiver operating characteristic curve) and goodness of fit (calibration curves and the Hosmer-Lemeshow statistic). Analysis was undertaken for both the entire cohort and for the group of patients whose APACHE scores were altered. There was a wide variation in the number of patients who had their scores altered between participating units. There were also differences between diagnostic groups. Overall, however, 50% of the patients were sedated and 22% had their scores altered. Using the presedation GCS score increased the discrimination of both APACHE II and APACHE III. The calibration of APACHE III was also improved but that of APACHE II deteriorated. The calibration improved, however, in those patients with altered scores, suggesting that the overall deterioration is attributable to other limitations in the fit of the model to these data. Although changes had the greatest effect in patients with a neurologic or trauma diagnosis, the changes were important in most diagnostic groups. CONCLUSIONS: The GCS is an important component of both APACHE II and APACHE III. It should be assessed directly whenever possible. When patients are sedated, using the GCS score recorded before sedation is preferable to the assumption of normality. The variations between different units and different diagnostic groups highlight the possible effects of case mix on the performance of prognostic scoring systems.