Extrathoracic multiple trauma dysregulates neutrophil function and exacerbates pneumonia-induced lung injury.

BACKGROUND: Forty percent of critically ill trauma patients will develop an infectious complication. Pneumonia is the most common cause of death of trauma patients surviving their initial insult. We previously demonstrated that polytrauma (PT), defined as two or more severe injuries in at least two areas of the body, induces emergency hematopoiesis characterized by accelerated myelopoiesis in the bone marrow and increased myeloid cell frequency in the peripheral tissues. We hypothesized that PT alone induces priming of neutrophils, resulting in hyperactivation upon secondary exposure to bacteria and causing acute lung injury and increased susceptibility to secondary exposure to Pseudomonas aeruginosa pneumonia. METHODS: C57BL/6 mice were subjected to PT consisting of a lower extremity pseudofracture, liver crush injury, and 15% blood-volume hemorrhage. Pneumonia was induced by intratracheal injection of 5 × 106 CFU live P. aeruginosa or 1 × 107 of heat-killed P. aeruginosa (HKPA). For reactive oxygen species (ROS), studies polymorphonuclear neutrophils (PMNs) were isolated by immunomagnetic bead negative selection and stimulated ex-vivo with HKPA. Reactive oxygen species production was measured by immunofluorescence. For histology, lung sections were stained by hematoxylin-eosin and analyzed by a blinded grader. RESULTS: Polytrauma induced persistent changes in immune function at baseline and to secondary infection. Pneumonia after injury resulted in increased mortality (60% vs. 5% p < 0.01). Blood neutrophils from PT mice had higher resting (unstimulated) ROS production than in naive animals (p < 0.02) demonstrating priming of the neutrophils following PT. After intratracheal HKPA injection, bronchoalveolar lavage PMNs from injured mice had higher ROS production compared with naive mice (p < 0.01), demonstrating an overexuberant immunopathologic response of neutrophils following PT. CONCLUSION: Polytrauma primes neutrophils and causes immunopathologic PMN ROS production, increased lung injury and susceptibility to secondary bacterial pneumonia. These results suggest that trauma-induced immune dysfunction can cause immunopathologic response to secondary infection and suggests neutrophil-mediated pulmonary damage as a therapeutic target for posttrauma pneumonia.

Acute Acalculous Cholecystitis-Associated Bacteremia Has Worse Outcome.

Background: Acute acalculous cholecystitis (AAC) is an inflammation of the gallbladder without gallstones in the setting of critical illness. It represents 2%-15% of acute cholecystitis (AC) cases. Bacteremia is associated with increased morbidity and mortality rates in patients in the intensive care unit (ICU). The incidence of bacteremia in acute calculous cholecystitis (ACC) has been described; however, the incidence of bacteremia in AAC has not been reported. We hypothesized that patients with AAC have higher bacteremia rates, leading to worse outcomes than in those with ACC. Methods: A prospectively collected acute care surgery (ACS) institutional database of patients treated from 2008 through 2018 was queried for patients having ACC using International Classification of Diseases (ICD) 9 and 10 codes. Demographics, microbiology findings, and outcomes were extracted. Only patients with positive blood cultures were included in the study. We defined two cohorts: AAC with bacteremia and ACC with bacteremia. The Student t-test was used for continuous variables and the χ2 and Fisher exact tests for categorical variables. Multivariable regression was applied, and statistical significance was set at p < 0.05. Results: Of 323 patients with AC, 57 (17.6%) had AAC and 266 (82.4%) had ACC. Of the 19 patients who had a blood culture, 11 (57.8%) were positive. Patients with positive blood cultures had a mean age of 56.7 ± 15.3 years and a mean Body Mass Index (BMI) of 26.7 ± 4.9. The incidence of bacteremia was significantly higher in AAC (n = 6; 10.5% versus n = 5; 1.9 %; p = 0.005), although the time between admission and diagnosis of bacteremia was similar in the two groups (1.2 ± 1.1 versus 0.2 ± 0.5 days; p = 0.128). The patients with AAC and bacteremia were younger (53.8 ± 19.2 versus 60.2 ± 8 years; p = 0.021) and had a longer ICU length of stay (LOS) (12.6 ± 7.2 versus 1.3 ± 2.1 days; p = 0.030). However, there was no difference in the mortality rate in the groups (n = 2; 33.3% versus 1; 20.0%; p = 1.000). After adjusting for age, gender, BMI, and Charlson Comorbidity Index, bacteremia in AAC patients was found to be an independent variable for longer ICU LOS (odds ratio 8.8; 95% confidence interval 1.7-15.9; p = 0.024). Conclusions: The incidence of bacteremia in patients with AAC is five-fold higher and the ICU stay eight days longer than in patients with ACC.

Temporary Abdominal Closure Is Associated with Increased Risk for Fungal Intra-Abdominal Infections in Trauma Patients.

Background: Fungal infections are associated with increased morbidity and death. Few studies have examined risk factors associated with post-operative fungal intra-abdominal infections (FIAIs) in trauma patients after exploratory laparotomy. In this study, we evaluated potential risk factors for acquiring post-operative FIAIs and their impact on clinical outcomes. Methods: This was a retrospective analysis of trauma patients admitted from 2005 to 2018 who underwent exploratory laparotomy and subsequently had development of intra-abdominal infection (IAI). Demographics, comorbidities, culture data, antimicrobial usage, Injury Severity Scores (ISS), and clinical outcomes were abstracted. All post-operative IAIs were evaluated and stratified as either bacterial, fungal, combined, and with or without colonization. All groups were compared. Risk factors for the development of post-operative IAI and clinical outcomes were analyzed by Student t test and chi-square test. Multi-variable logistic regression was used to determine independent predictors of post-operative FIAIs. Results: There were 1675 patients identified as having undergone exploratory laparotomy in the setting of traumatic injury, 161 of whom were suspected of having IAI. A total of 105 (6.2%) patients had a diagnosis of IAI. Of these patients, 40 (38%) received a diagnosis of FIAI. The most common fungal pathogens were unspeciated yeast (48.3%), followed by Candida albicans (42.7%), C. glabrata (4.5%), C. dubliniensis (2.25%), and C. tropicalis (2.25%). There were no significant differences in demographics, comorbidities, and percentage of gastric perforations between FIAI and bacterial IAI (BIAI) groups. Patients with FIAIs, however, had a 75% temporary abdominal closure (TAC) rate compared with 51% in BIAIs (p = 0.01). The FIAI group had higher ISS (27 vs. 22, p = 0.03), longer hospital days (34 vs. 25, p = 0.02), and longer intensive care unit (ICU) days (17 vs. 9, p = 0.006) when compared with BIAI. The FIAI group also had a five-fold greater mortality rate. Logistic regression identified TAC as an independent risk factor for the development of post-operative FIAIs (odds ratio [OR] 6.16, confidence interval [CI] 1.14-28.0, p = 0.02). Conclusions: An FIAI after exploratory laparotomy was associated with greater morbidity and death. A TAC was associated independently with increased risk of FIAI after exploratory laparotomy in the setting of traumatic injury. Clinicians should suspect fungal infections in trauma patients in whom post-operative IAI develops after undergoing exploratory laparotomy using TAC techniques.