Outcome and prognostic factors in critically ill immunocompromised patients admitted to the ICU

Introduction

Intensive care physicians are facing a growing number of immunocompromised patients. The evidence on how immunosuppression impacts on ICU outcome is poor. We conducted a retrospective cohort study to compare immuno-compromised patients with immunocompetent patients with regard to their ICU outcome and, furthermore, to identify prognostic factors.

Methods

Over a period of 36 months, 656 patients were referred to a medical eight-bed ICU of a university hospital. Of these, 190 were categorized as immunocompromised. Immunosuppression was defined as an absolute neutrophil count < 1000/μl (n = 66) at admission, or the administration of immunosuppressive drugs (IS) prior to admission (n = 124). IS used usually were corticosteroids and cyclosporine, more rarely FK 506, cyclophosphamide and methotrexate. We recorded demographic data, reason for admission, APACHE III score, occurrence of septic shock and the need and duration of mechanical ventilation (MV). The primary endpoint of the study was ICU survival. The groups were compared by Fisher's exact test for categorical variables and by the Mann–Whitney U test for continuous variables (univariate analysis). Using a multivariate logistic regression model, we controlled for several risk factors.

Results

The overall mortality was 33%. Immunocompromised patients had a significantly higher mortality than immunocompetent patients (45% vs 29%, P < 0.001). This difference was even more pronounced if patients required MV (64% vs 34%, P < 0.001). Patients with neutropenia tended to have a higher mortality than patients with IS therapy, but this difference failed to show statistical significance. The presence of septic shock at any time during ICU treatment and the associated mortality from septic shock did not significantly differ between immunocompromised and immunocompetent patients. In multivariate analysis, lower APACHE III scores at admission and admission for postoperative care were independently associated with reduced ICU mortality, whereas immunosuppression and MV were independently associated with unfavourable outcome. Immunosuppression remained to be associated with higher ICU mortality if the statistical model was adjusted for APACHE III score, postoperative care and mechanical ventilation.

Conclusion

Immunosuppression is an independent risk factor of death in the ICU. In order to develop preventive strategies, controlled studies are needed to identify further risk factors in these patients.