Case mix outcome and activity for patients with ARF during the first 24 hours of the intensive care unit

We examined outcomes for patients with ARF identified from a national comparative audit of adult general ICUs in England, Wales and Northern Ireland, the Case Mix Programme.

Of 276,731 admissions to 170 ICUs over an 8-year period ARF was present during the first 24 hours of admission in 17,326 (6.3%), 66% were male. Oliguria and non-oliguria were determined by UOP < 400 ml/day or > 400 ml/day. Table 1 presents age, surgical status and mortality of the ARF patients. Mean APACHE II score was 24.8 compared with 16.5 for all ICU admissions, and was significantly higher in oliguric ARF (29.3) versus non-oliguric (17.9). A total of 83.7% of admissions with ARF were non-surgical. Both ICU and hospital mortality were significantly higher for oliguric ARF compared with non-oliguric ARF. Factors predicting increased mortality were: increasing age, male sex, chronic conditions, CPR, IPPV, oliguria, prior hospital stay of 7+ days, extremes of temperature, heart rate and respiratory rate, low MAP, low pH, high A-aDO₂, abnormal sodium, high potassium, low albumin, low WBC and low Glasgow Coma Score. Surgery within 1 week of ICU admission conferred survival benefit.

Table 1

The median ICU length of stay (LOS) was 4.1 days for ARF survivors and 2.0 days for non-survivors, compared with 1.7 and 2.0 days, respectively, for all ICU admissions. Admissions with ARF accounted for 9.3% of all ICU bed days. Median hospital LOS was 31 days for ARF survivors and 8 days for non-survivors, compared with 16 and 9 days, respectively, for all ICU admissions. Oliguria was associated with longer LOS for survivors and shorter LOS for non-survivors.

Although the predominant cause of ICU ARF is now non-surgical the factors influencing survival remain unchanged. ARF occupies ca. 10% of all ICU bed days and doubles both ICU and hospital LOS in survivors.