Assessment of sepsis-induced immunosuppression at ICU discharge and 6 months after ICU discharge

Background: Increase in mortality and in recurrent infections in the year following ICU discharge continues in survivors of septic shock, even after total clinical recovery from the initial septic event and its complications. This supports the hypothesis that sepsis could induce persistent long-term immune dysfunctions. To date, there is almost no data on ICU discharge and long-term evolution of sepsis-induced immunosuppression in septic shock survivors. The aim of this study was to assess the persistence of sepsis-induced immunosuppression by measuring expression of human leukocyte antigen DR on monocytes (mHLA-DR), CD4+ T cells, and regulatory T cells (Treg) at ICU discharge and 6 months after ICU discharge in patients admitted to the ICU for septic shock.

Methods: In this prospective observational study, septic shock survivors with no preexisting immune suppression or treatment interfering with the immune system were included. mHLA-DR, CD4+ T cells, and Treg expression were assessed on day 1-2, 3-4, and 6-8 after ICU admission, at ICU discharge, and 6 months after ICU discharge.

Results: A total of 40 patients were enrolled during their ICU stay: 21 males (52.5%) and 19 females, median age 68 years (IQR 58-77), median SOFA score on day 1-2 was 8 (IQR 7-9), and median ICU length of stay was 11 days (IQR 7-24). Among these 40 patients, 33 were studied at ICU discharge and 15 were disposed for blood sampling 6 months after ICU discharge. On day 1-2, mHLA-DR expression was abnormally low for all patients [median 4212 (IQR 2640-6047) AB/C] and remained abnormally low at ICU discharge for 75% of them [median 10,281 (IQR 7719-13,035) AB/C]. On day 3-4, 46% of patients presented CD4+ lymphopenia [median 515 (IQR 343-724) mm^-3] versus 34% at ICU discharge [median 642 (IQR 459-846) mm^-3]. Among patients with a 6-month blood sample, normal values of mHLA-DR were found for all patients [median 32,616 (IQR 24,918-38,738) AB/C] except for one and only another one presented CD4+ lymphopenia.

Conclusions: While immune alterations persist at ICU discharge, there is, at cellular level, no persistent immune alterations among septic shock survivors analyzed 6 months after ICU discharge.