Community-Wide Assessment of Intensive Care Outcomes Using a Physiologically Based Prognostic Measure: Results

10 Aug
2014

The mean age of study patients was 63 years and 52% were men (Table 1). Forty-one percent of patients were admitted through the emergency department; 37% of patients (n = 42,416) were postoperative (ie, admitted to the ICU after undergoing a surgical procedure), and 63% of patients (n = 73,924) were nonoperative. The 10 most common ICU admission diagnoses accounted for nearly 50% of admissions and included the following: angina (n = 10,046); congestive heart failure (n = 8,007); trauma to the head, spine, chest, abdomen, or extremities that was managed surgically or nonsurgi-cally (n = 5,913); GI hemorrhage (n = 5,446); carotid endarterectomy (n = 4,912); stroke or CNS hemorrhage (n = 4,902); lower extremity bypass graft (n = 3,950); acute myocardial infarction (n = 3,778); COPD or asthma (n = 3,588); and cardiac arrhythmias (n = 3,454).
The median APS was 41 and ranged from 29 to 51 in the 28 hospitals. The overall observed in-hospital mortality rate was 11.3%. APSs were strongly related (p < 0.001) to in-hospital mortality rates, which ranged from 0.1% in patients with scores of < 10 to 95% in patients with scores > 150 (Fig 1). The ROC curve area of risk predictions based on the previously validated APACHE III national normative risk-ad-justment model was 0.901, indicating excellent discrimination. However, the national model consistently overestimated the risk of death across all deciles of predicted risk (Fig 2, top). Thus, the overall mean predicted risk of death, based on the APACHE III national model, of 12.5% was roughly 1.2% higher than the observed death rate of the current population, and the Hosmer-Lemeshow statistic, a sensitive measure of differences between predicted and observed outcomes in large data sets, indicated miscalibration (x2 = 2407.6, 8 df, p < 0.001). purchase antibiotics online

As would be expected, risk predictions based on the locally derived model exhibited much better calibration (Fig 2, bottom). The mean predicted risk of death of 11.3% was identical to the observed death rate and the Hosmer-Lemeshow statistic was not significant (x2 = 13.5, 8 df, p = 0.10), indicating that the model was well calibrated across all ranges of risk. The ROC curve area of the model was 0.907.

Table 1—Characteristics of 116,340 Study Patients

CharacteristicValue
Age (y), mean (SD)62.9 (20.0)
APACHE III APS (SD)
Mean (SD)46.9 (27.6)
Median (interquartile range)41.0 (28.0-59.0)
Predicted risk of death (APACHE
III national model)
Mean (SD)0.125 (0.201)
Median (interquartile range)0.040 (0.015-0.126)
Predicted risk of death (local model)
Mean (SD)0.113(0.195)
Median (interquartile range)0.028 (0.008-0.113)
ICU LOS, d
Mean (SD)3.9 (4.8)
Median (interquartile range)3 (2-4)
Hospital LOS, d
Mean (SD)12.0(12.7)
Median (interquartile range)8 (5-14)
% of Patients (No.)
Gender, male51.9 (60,417)
Admission source
Operating room16.5 (19,225)
Recovery room20.7 (24,073)
Emergency department40.9 (47,636)
Hospital ward11.3 (13,152)
Other ICU3.2 (3,683)
Other acute care hospital2.7 (3,180)
Direct admission4.5 (5,289)
Non-ICU holding area 0.1 (100)
ICU mortality rate6.3 (7,285)
In-hospital mortality rate11.3(13,166)
Comorbid conditions
AIDS0.2 (193)
Cirrhosis2.0 (2,309)
End-stage renal disease*2.9 (3,349)
Hepatic failure0.6 (641)
Immunosuppressive therapy3.2 (3,736)
Lymphoma0.7 (831)
Leukemia/multiple myeloma0.6 (681)
Solid tumor with metastasis3.7 (4,278)

 

Figure 1. In-hospital mortality rates according to APACHE III acute physiology scores. Mortality rates ranged from 0.1% in patients with scores of < 10 to 95.2% in patients with scores of > 150.

Figure 1. In-hospital mortality rates according to APACHE III acute physiology scores. Mortality rates ranged from 0.1% in patients with scores of < 10 to 95.2% in patients with scores of > 150.

Figure 2. Differences in observed and predicted death rates across deciles of increasing risk, based on risk predictions from (top, A) the APACHE III national normative model and (bottom, B) the locally derived model (see “Materials and Methods” section). Top, A: observed and predicted death rates differed (p < 0.05) in all deciles except for deciles 8 and 9. Bottom, B: observed and predicted death rates were similar (p > 0.05) in all deciles.

Figure 2. Differences in observed and predicted death rates across deciles of increasing risk, based on risk predictions from (top, A) the APACHE III national normative model and (bottom, B) the locally derived model (see “Materials and Methods” section). Top, A: observed and predicted death rates differed (p < 0.05) in all deciles except for deciles 8 and 9. Bottom, B: observed and predicted death rates were similar (p > 0.05) in all deciles.

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