In our retrospective single-center cohort study involving 200 septic shock patients, we identified GM-CSF treatment as a protective factor associated with 28-day mortality in our multivariable regression model. In addition, we also identified several predictors of the treatment outcomes, including higher LAC, lower RBC and lower PLT.
As a pro-inflammatory cytokine, GM-CSF plays a crucial role in stimulating the bone marrow to produce granulocytes and macrophages, thereby counteracting immune suppression in septic shock patients(14). Various studies have explored the impact of GM-CSF on sepsis-induced immunosuppression(15, 16), yet their findings are inconclusive due to methodological differences. For instance, in a randomized controlled trial, C.-H. Vacheron found that using GM-CSF could not decrease the 28-day mortality and ICU-acquired infection (15). Contrary to the research, some retrospective analyses of G-CSF or GM-CSF demonstrated a positive effect on sepsis(17). However, these studies were conducted on adults, leaving the effect of GM-CSF on 28-day mortality in pediatric septic shock patients unknown.
In the beginning, we observed a higher 28-day mortality rate, in-hospital mortality, and a greater proportion of DIC complications among individuals treated with GM-CSF therapy. However, we observed differences in the baseline characteristics of patients between the two groups, suggesting the above results may have been influenced by confounding factors. Therefore, we employed multivariable logistic regression analysis in an attempt to mitigate the impact of these confounding factors on the results. Due to the characteristics of septic shock progression, we incorporate patients' baseline conditions, infection status, and hematologic indicators into our regression model. Finally, the OR for GM-CSF is 0.472 (95% CI: 0.153-1.457), indicating that it is a protective factor although not statistically significant. This finding contrasts with our initial observation. To explore this distinction, we then focused on significant predictors associated with outcomes in our model, including HSCT, high LAC, HASS, low RBC, and low PLT, which may influence the association between GM-CSF and 28-day mortality.
The first set of predictors associated to the outcome of GM-CSF treatment includes patients' baseline conditions, chiefly involving HSCT and elevated lactate levels. In our study, patients with a history of tumor chemotherapy or HSCT constituted the two main groups significantly associated with GM-CSF usage in septic shock cases. Although the overall objective of using GM-CSF as adjunctive therapy in these two patient groups is consistent – namely, to enhance the immune function in neutropenic patients(18-20) – only HSCT emerged as a significant predictor associating with the effect of GM-CSF treatment. Patients with HSCT generally have poorer baseline conditions and are susceptible to various risk factors for mortality because of graft-versus-host disease and infections(21). Elevated lactate levels is another crucial predictor, indicating tissue hypoxia and exacerbating the suppressive effects on immune cells, ultimately compromising the body's immune response capabilities(22). A retrospective cohort study of 1,060 patients diagnosed with septic shock revealed a significant correlation between lactate levels at 6 hours and mortality rates (OR with 95% CI, 1.27 [1.21-1.34]). Therefore, it makes sense that high lactate level is associated with adverse outcomes. Next, we focus on the infection-related factors, with Hospital-acquired septic shock (HASS) emerging as the most significant. Previous research has consistently highlighted a higher 28-day mortality among HASS patients compared to those with community-acquired septic shock (CASS)(12, 23), underscoring the importance of considering HASS as a predictor of outcomes.
Notably, the hematologic status including RBC, and PLT was also an important predictor of patients’ outcomes in our study. RBCs not only have the function of transporting and exchanging oxygen and carbon dioxide but also play an essential role in cellular blood immunity such as chemokine regulation, complement binding, and pathogen immobilization(24, 25). In the context of sepsis, decreased RBC counts can stem from various mechanisms, including functional iron deficiency, infection, inflammation, and the onset of multiple organ dysfunction(26). Although studies have shown that RBC count alone may not serve as a diagnostic or prognostic indicator in sepsis, it can serve as a valuable marker reflecting the disease's severity(27). In our retrospective study, the majority of patients had underlying diseases, and those who experienced septic shock with low red RBC levels tended to have worse clinical outcomes. Platelets, on the other hand, are pivotal in hemostasis and exert significant modulatory effects on inflammatory responses(28). Thrombocytopenia, commonly observed in sepsis and septic shock, often results from decreased production and increased consumption(29). Notably, lower platelet counts have been consistently linked to heightened mortality among patients admitted to the ICU(30, 31). For instance, a prospective study involving 931 septic shock patients revealed that individuals with low and intermediate-low platelet counts exhibited a heightened risk of 30-day mortality compared to those with normal platelet levels (hazard ratios with 95% CI, 2.00 [1.32-3.05] and 1.72 [1.22-2.44], respectively(32).
Despite these insights, our study faced several limitations. Firstly, this study is an observational study. Although it is a retrospective cohort study, factors of the efficacy of GM-CSF treatment in pediatric septic shock need to be tested by RCTs. Secondly, our study is a single-center study, which may limit the generalizability of our findings. Finally, we still need to increase the days of follow-up to examine the long term clinical outcome.