Leukopenia (WCC<4) Rather than Leukocytosis (WCC>14) Within 48 Hours of Admission Has a Greater Impact on Mortality Following Trauma; An Analysis of 2,467 Patients

Abstract

Background: Both leukopenia (White Cell Count (WCC) <4,000 cells/mm3) and leukocytosis (WCC>12 cells/mm3) are components of the Systemic Inflammatory Response Syndrome (SIRS). The degree of SIRS correlates with the degree of physiologic and immunologic derangements, which may occur following trauma and critical illness. Considerable volumes of data have focused on the significance of an elevated WCC as a marker of the degree of SIRS and inflammation. However, there is almost no data addressing the impact of a leukopenia, WCC below 4, compared to patients who mount a leukocytosis. We wished to assess the impact of leukopenia (WCC<4) compared with leukocytosis (WCC>12) within the first 48 hours following admission in trauma patients. Materials and Methods: This was a retrospective analysis of all trauma patients admitted to a level 1 trauma center over the 5-year period of January 2003 to January 2008. All White Cell Counts (WCC) for the first 48 hours after admission were retrieved. Patients were considered leukopenic if their WCC was under 4,000/mm3 at any time during the first 48 hours following admission, irrespective of the rest of their WCCs during that 48 hour period. Patients had leukocytosis if the WCC was greater than 12,000/mm3 but never less than 4,000/mm3 during the first 48 hours following admission. Charts were reviewed for age, gender mechanism, hospital and ICU length of stay, ventilator days, Injury Severity Scores (ISS), rates of head injury and mortality. Chi-Squared, Fisher's exact and Mann-Whitney U were used for statistical analysis. Results: 2,467 patients met criteria, or whom 72 had a WCC<4, and 2395 patients had a WCC>12, but never less than 4,000/mm3 within the first 48 hours. The groups (leukopenic vs leukocytosis) did not differ with respect to age (44.6 years vs. 46.3 years; p=0.6), gender (67% vs. 63% Male; p=0.6143), or ISS (21 vs. 18, p=0.062), or presence of head injury (31% vs 41%; p=0.09). Leukopenic patients had slightly less rates of blunt mechanism (73% vs 84%; p=0.01). However Leukopenia was significantly associated with increased hospital (15.6 vs 10.1 days; p=0.03), and ICU length of stay (8.4 vs. 2.7 days; p=0.0001), prolonged ventilator requirement (5.7 vs. 1.8 days; p=0.0001). Leukopenic patients had a significantly higher mortality rate (17% vs. 9%; p=0.03). Young patients (18 to 35 years old) suffered the greatest impact on mortality from leukopenia vs leukocytosis (14% vs 3%; p=0.002). Conclusions: Understanding the consequences of alterations in WCC, especially a leukopenia following trauma and critical illness is extremely important to our understanding of SIRS. Whilst a considerable body of literature has built up regarding the impact of leukocytosis as part of SIRS, there is a dearth of information pertaining to the other side of the WCC story. We clearly demonstrate that there is a greater impact on outcomes such as hospital and ICU length of stay, and ultimately mortality, especially in the young, from leukopenia (WCC<4,000/mm3 rather than leukocytosis (>12,000/mm3) following hospitalization for traumatic injuries.