Ratio of neutrophil to lymphocyte counts--rapid and simple parameter of systemic inflammation and stress in critically ill

Abstract

Background: For many years, the intensivists are searching for an easily measurable and available parameter which might reflect the intensity of stress and/or systemic inflammation in critically ill patients following shock, multiple trauma, major surgery or sepsis. Recently, some authors have described the onset of significant lymphocytopenia after polytrauma, major surgery, endotoxaemia and sepsis. We investigate whether serial examination of white blood cell counts may reflect and clarify the immune response to stressful events in critically ill patients.

Goal: We have designed a prospective longitudinal observational study to investigate serial changes in circulating neutrophil and lymphocyte counts following major surgery, unscheduled surgery and sepsis.

Methods: We have investigated the differential white blood cell counts and the clinical course in 90 oncological ICU patients. We compared three groups: group A consisting of 62 patients who underwent scheduled colorectal surgery, group B consisting of 18 patients who underwent unscheduled surgery for abdominal sepsis, group C consisting of 10 medical ICU patients who were treated for severe sepsis and septic shock. The severity of clinical course was expressed by means of SOFA score (group A 0.3-1-1.3 point, group B 2.2-2.9-2.6 point, group C 7.4-8.3-7.7 point) and APACHE II score (group A 3.7-7.6-8.1 point, group B 8.6-11.1-10.5 point, group C 16.3-15.2-14.3 point). Differential white blood cell counts were investigated on blood cell counter SYSMEX SF 3000 in 4 consecutive periods: 1 day one before surgery, 0 the day of surgery or ICU admittance, 1 day one after surgery (or the 1st ICU day), 2nd day following surgery (or the 2nd ICU day). The measured values of neutrophils and lymphocytes were expressed as relative counts (%) of the whole all white blood cell population.

Results: The physiologic response of circulating leukocytes to surgical stress in group A is characterized by the onset of marked neutrophilia (62.5% before surgery up to 84.4% after surgery) and significant lymphocytopenia (28.1% before surgery to 10.3% following surgery). We observed a slow decline in neutrophil counts and an increase in lymphocyte counts since the 1st postoperative day. The patients with abdominal infection (group B) had elevated counts of neutrophils already before surgery (83.2%) and low values of lymphocyte counts (9.5%). A further increase in neutrophil counts (89.9%) and marked lymphopenia (7%) were recorded during the post-surgical period in group B. Critically ill patients with severe sepsis or septic shock (group C) had significantly highest values of neutrophil relative counts (94%-93.1%-92.5%, p < 0.05 against group A) and marked lowest values of lymphocyte counts (3.8%-4%-3.7%, p < 0.05 against group A). The severity of clinical course (according SOFA and APACHE II score) correlated with the divergence of neutrophil and lymphocyte counts in the white blood picture (marked neutrophilia and lymphocytopenia).

Conclusion: In the population of 90 ICU oncological patients, we observed rapid serial changes in white blood cell populations, as a response of the immune system to surgical stress, systemic inflammation or sepsis. Preliminary results show the correlation between the severity of clinical course and the grade of neutrophilia and lymphocytopenia. The ratio of neutrophil and lymphocyte counts (in absolute and/or relative % values) is an easily measurable parameter which may express the severity of affliction. We suggest the term: neutrophil-lymphocyte stress factor, as a ratio of neutrophil to lymphocyte counts, which can be routinely used in clinical ICU practice in intervals of 6-12 and 24 hours. The prognostic value of neutrophil-lymphocyte stress factor should be evaluated in further studies. (Tab. 6, Fig. 5, Ref. 12.)