Iatrogenic blood loss due to daily laboratory testing and the risk of subsequent anaemia in intensive care unit patients: case series

Abstract

Introduction: Anaemia is associated with a wide range of negative outcomes. Diagnostic blood loss (DBL) may contribute to its occurrence. We aimed to evaluate DBL and its impact on haemoglobin (HGB) concentration and developing anaemia in the intensive care unit (ICU) patients. Methods: A study group comprised of 36 adult ICU patients. DBL during 7 consecutive, post-admission days was calculated. Anaemia occurrence was assessed using the WHO thresholds. Data on HGB and haematocrit (HCT) was subjected to analysis. Results: Upon admission, 24 (67%) patients were diagnosed with anaemia, on the eighth day 29 (80%) subjects (with 6 new cases). The median volume of blood collected was 143.15 mL (IQR 121.4–161.65) per week. No differences in DBL were found between the subjects with newly developed anaemia and their counterparts (p=0.4). The median drop of HGB (HbΔ) was 18 gL–1 (IQR 5–28) and the median drop of haematocrit (HtΔ) was 4.55% (IQR 1.1–7.95). There was no correlation between neither HbΔ and DBL (p=0.8) nor HtΔ and DBL (p=0.7). There were also no differences in HbΔ/HtΔ when age, gender or the primary critical illness were taken into account for the analysis (p>0.05 for all). The 7-day fluid balance was associated with haemoglobin drop (R=0.45; p=0.006). Conclusions: Anaemia is frequent in ICU patients. Diagnostic blood loss in our institution is acceptable and seems to protect patients against significant iatrogenic blood loss and subsequent anaemia. Dilutional anaemia may interfere with the results so before-after interventional research is needed to explore this interesting topic.