Association Between Neutrophil Density and Survival in Trauma Patients Admitted to the Intensive Care Unit; a Retrospective Cohort Study

Altered immune responses, in particular neutrophil changes, are perceived to play a key role in immuneresponses to trauma. This study aimed to evaluate the association of neutrophil changes with patients’ survival in severetrauma cases.

The current retrospective cohort study was conducted using data from patients admitted in theintensive care unit (ICU) of a trauma center in Shiraz, Iran, between 2016 and 2021. Patients were divided into threegroups (i.e., normal, neutropenia, and neutrophilia) based on neutrophil count at the time of ICU admission, and theassociation of neutrophil count with in-hospital mortality was analyzed.

2176 patients with the mean age of37.90 ± 18.57 years were evaluated (84.04% male). The median trauma severity based on injury severity score (ISS) in thisseries was 9 (4 -17). Patients were divided in to three groups of neutrophilia (n = 1805), normal (n = 357), and neutropenia(n = 14). There were not any significant differences between groups regarding age distribution (p = 0.634), gender (p =0.544), and trauma severity (p = 0.197). The median survival times for the normal, neutropenia, and neutrophilia groupswere 49 (IQR: 33 -47) days, 51 (IQR: 8- 51) days, and 38 (IQR: 26 - 52) days, respectively (p = 0.346). The log-rank testshowed a statistically significant difference between the three groups adjustment for ISS (p≤0.001). For each unitincrease in ISS, the hazard ratio increased by 2%. In ISS 9-17, the hazard ratio increased by 11% compared to ISS<4. Also,in ISS>17, the hazard ratio increased by 76% compared to ISS<4 in ICU-hospitalized patients.

In general,the findings of the present study showed that the survival rate of patients in the normal group after ISS adjustment washigher than the other two groups. Also, the Cox model showed that the mortality risk ratio in the neutropenia group was15 times higher than the normal group.