Reticulocyte counts and their relation to hemoglobin levels in trauma patients

Introduction

In many trauma patients, blood loss is the major cause of anaemia. Subsequent increased production of red blood cells is reflected by increased reticulocyte numbers (R). Measurement of the R might be useful in predicting the recovery of hemoglobin (Hb), especially since current transfusion guidelines accept lower Hb levels. The value of the modern fully automated measurement of R in assessing recovery of Hb after blood loss has not been investigated in this context. We therefore investigated the temporal relation of Hb and R in a cohort of trauma patients.

Methods

Over a 10-month period all patients with trauma admitted to our hospital were analysed. Patients were grouped by comorbidity and reason for admission. When an Hb was routinely measured, a R measurement was also performed in the same sample. Both Hb and R (reference range 8–26 promille) were determined in EDTA-anticoagulated blood in the central laboratory with a Sysmex XE-2100. Before further pooled analysis, values for individual patients were averaged or interpolated to daily values. Red blood cell (RBC) transfusions were administered according to modern restrictive transfusion guidelines, with a Hb threshold of 4.3 mmol/l in otherwise healthy patients. Hb and R were analyzed for a maximum of 30 days post-trauma, and were related with age, sex and the presence of comorbidity.

Results

Two hundred and forty-one patients with a mean ± SD age of 52 ± 21 years were studied. The mean length of stay was 15 days (range 1–110). In 107 patients (44%), important comorbidity was present. In 28 patients (12%), one or more RBC transfusions were administered with a mean of 2.2 RBCs (range 1–4). Hb decreased from a mean level of 7.6 ± 1.5 mmol/l at admission to 6.8 ± 1.3 on day 3. R slowly rose from 16 ± 11 at admission to 38 ± 21 promille on day 13. The highest R value observed was 121 promille. Nadir Hb values and maximum R values were inversely related upon univariate analysis (Pearson R = -0.62, P < 0.001). Multivariate analysis with the variables minimal Hb, maximum R, age, sex, and the presence of comorbidity showed that only minimal Hb was a significant determinant of R (R = 0.63).

Conclusion

There is a strong relationship between minimal Hb and maximum R in trauma patients. The measurement of reticulocytes may be helpful in predicting the recovery in Hb after acute blood loss due to trauma and to assist in deciding whether a patient needs to be transfused.