Trends in admission prevalence, illness severity and survival of haematological patients treated in Dutch intensive care units.

Purpose: To explore trends over time in admission prevalence and (risk-adjusted) mortality of critically ill haematological patients and compare these trends to those of several subgroups of patients admitted to the medical intensive care unit (medical ICU patients).

Methods: A total of 1,741 haematological and 60,954 non-haematological patients admitted to the medical ICU were analysed. Trends over time and differences between two subgroups of haematological medical ICU patients and four subgroups of non-haematological medical ICU patients were assessed, as well as the influence of leukocytopenia.

Results: The proportion of haematological patients among all medical ICU patients increased over time [odds ratio (OR) 1.06; 95 % confidence interval (CI) 1.03-1.10 per year; p < 0.001]. Risk-adjusted mortality was significantly higher for haematological patients admitted to the ICU with white blood cell (WBC) counts of <1.0 × 10(9)/L (47 %; 95 % CI 41-54 %) and ≥1.0 × 10(9)/L (45 %; 95 % CI 42-49 %), respectively, than for patients admitted with chronic heart failure (27 %; 95 % CI 26-28 %) and with chronic liver cirrhosis (38 %; 95 % CI 35-42 %), but was not significantly different from patients admitted with solid tumours (40 %; 95 % CI 36-45 %). Over the years, the risk-adjusted hospital mortality rate significantly decreased in both the haematological and non-haematological group with an OR of 0.93 (95 % CI 0.92-0.95) per year. After correction for case-mix using the APACHE-II score (with WBC omitted), a WBC <1.0 × 10(9)/L was not a predictor of mortality in haematological patients (OR 0.86; 95 % CI 0.46-1.64; p = 0.65). We found no case-volume effect on mortality for haematological ICU patients.

Conclusions: An increasing number of haematological patients are being admitted to Dutch ICUs. While mortality is significantly higher in this group of medical ICU patients than in subgroups of non-haematological ones, the former show a similar decrease in raw and risk-adjusted mortality rate over time, while leukocytopenia is not a predictor of mortality. These results suggest that haematological ICU patients have benefitted from improved intensive care support during the last decade.