The Pathobiome and Immunologic Function Following Blunt Splenic Injury: The Bad and the Good!

Author(s):
Samuel Coster; Kwame Akuamoah-Boateng; Zequan Yang; Aimee Zhang; Saad Shebrain; Robert Sawyer

Background:

The severity of blunt splenic injury dictates management, ranging from a non-operative approach to splenectomy. The spleen has a crucial immunologic function.

Hypothesis:

We hypothesized that blunt splenic injury is associated with changes in infectious organisms (pathobiome) and outcomes in post-splenectomized trauma patients.

Methods:

Cases were extracted from a database prospectively collected between 1997 and 2017 that included all intensive care unit (ICU)-acquired infections in blunt trauma patients treated in a single, Level I trauma center.  Patients were divided into three groups: No splenic injury/minor splenic injury < Grade 3 (group A), splenic injury ≥ Grade 3 without splenectomy (Group B), and injury requiring splenectomy (Group C).  ANOVA and Chi-square tests, followed by post-hoc analysis were performed to compare patient demographic characteristics and outcomes.  Multivariable logistic regression analysis was performed to identify predictors associated with in-hospital mortality.

Results:

1843 infections were analyzed: 1,618 in group A, 88 in group B, and 137 in group C. Post-splenectomy infection was associated with younger age, higher APACHE II score, higher white blood cell count, and fungal etiology.  Splenic injury without splenectomy was associated with the lowest mortality. Factors independently associated with increased in-hospital mortality included higher age, higher APACHE II score, male sex, lower temperature, and splenic injury ≥ Grade 3 without splenectomy [OR = 0.28, CI (0.078-1.00), p = 0.05], with model AUROC C statistic = 0.84 and Hosmer-Lemeshow test = 0.17.

Conclusions:

Microbiologically, splenectomy is associated with increased fungal infections, therefore, empiric anti-fungal therapy should be considered for septic, post-splenectomy trauma patients.  Since the mortality rate was lowest in patients who had high-grade splenic injury but did not undergo splenectomy, activation of the inherent immunologic function of the injured spleen may serve as a protective factor in this patient group.  Potential mechanisms for these findings, for example, those related to ischemia-reperfusion effects, should be explored.