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Outcome of Patients Requiring Medical ICU Admission Following Bone Marrow Transplantation: Discussion

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Outcome of Patients Requiring Medical ICU Admission Following Bone Marrow Transplantation: DiscussionWe conclude that while the mortality rate for patients requiring mechanical ventilation after BMT is more than 96 percent for those patients without significant respiratory failure, there is a reasonable chance of MICU survival. Overall, 16 percent of patients required admission to the MICU after BMT. This figure varied from others reported in the literature; for example, Afessa and colleagues found that 24 percent of patients at their institution required ICU care after BMT. Other series have reported that 30 to 40 percent of patients with BMTs required ICU admission. It is unlikely that the patients studied had a lower premorbid risk to account for this difference. The lower rate of MICU admission at our institution may be due to the impact of the controlled environmental oncology unit, which is an intermediate care unit with laminar air flow; this unit can care for patients with increased levels of acuity. Since most patients with BMTs at our institution are referred locally, it is unlikely that their posttransplant critical care took place at other institutions and was not recorded.
The overall mortality rate for nonsurgical patients with BMTs admitted to the ICU has been reported to be 87 percent to 96 percent. While overall the survival rate was much higher in our study with 33 percent of patients surviving their MICU stay, the outcome for patients requiring mechanical ventilation was similar to that in other series. Denardo and colleagues reported that only one of 40 (2.5 percent) mechanically ventilated patients with BMT with respiratory failure survived hospitalization and that individual died after 10 months. In a second series, the overall survival after mechanical ventilation was 7 percent. Similarly, Crawford and Petersen found that 348 of 1,482 (23 percent) marrow recipients required mechanical ventilation with only four patients (3 percent) surviving for more than 6 months after intubation.
We did not find significant differences in patient characteristics between survivors and nonsurvivors with regard to age, sex, indication for BMT, conditioning regimen, and history of GVHD, as did an earlier report. In addition, there were no differences with regard to conditioning regimen, disease state, type of transplant, and MICU admitting diagnosis. Unlike the study by Crawford and Petersen, we did not identify age or disease state as risk factors for mechanical ventilation.
In contrast to the study by Afessa and colleagues, we did find that there was a significant difference in APACHE II scores between survivors and nonsurvivors at the time of admission. In that report, there were no differences in APACHE II even when surgical patients were not included. While these results support the use of prognostic scoring systems in the ICU setting, it should be noted that mechanical ventilation alone similarly predicted outcome. The only two nonmechanically ventilated patients who died in the MICU had APACHE II scores of 16 and 17, which were similar to the survivors. While both APACHE II score and length of stay were significantly different with respect to survivors and nonsurvivors, there was no significant correlation between these two variables. The lack of a statistical relationship may be due to the population size. Of significance is the finding that the nonsurvivor group had the longest average length of stay in the MICU.