IMPLEMENTING A RESTRICTIVE BLOOD SAMPLING STRATEGY IN A LARGE TERTIARY CARDIAC ICU
Angus Butchart1, Vasileios Zochios2, Andy Klein1, Nicola Jones1
1. Papworth Hospital NHS Foundation Trust, Cambridge, UK 2. University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
Anaemia and the requirement for blood transfusion after cardiac surgery have been shown to negatively impact on morbidity and mortality . Cumulative diagnostic blood sampling can be a significant cause of haemoglobin attrition, particularly in patients in intensive care. We sought to determine whether implementation of a low volume restrictive blood sampling strategy in a large cardiothoracic intensive care unit (CICU) reduced the burden of sampling loss and whether this was associated with higher haemoglobin on discharge from CICU or reduced need for red blood cell (RBC) transfusion.
In March 2014 standard adult 3ml arterial blood gas (ABG) syringes were replaced with 1ml paediatric ABG syringes in CICU. We then retrospectively evaluated ABG sample volume, discharge haemoglobin and RBC transfusion in 8887 patients admitted to CICU before and after the intervention. Patients were categorised by length of stay (LOS) as short (<72h), medium (3-7days), long (7-30days) or prolonged (>30days), and timing of transfusion as early (<72h), mid (3-7days) and late (>7days ).
Overall daily blood loss due to ABG sampling was reduced from (mean ± SD) 67±3.7ml in 2013 to 40±9.7ml and 39±8.8ml in 2014 and 2015 respectively (p<0.0001). This effect was observed with equivalent significance in all LOS categories (fig. 1). In long-stay patients this equated to a mean reduction in ABG-related blood loss of 280ml, and 1160ml for those with LOS >30days . There was a reduction in total RBC transfusion during the study period, 4637units in 2013 to 3222units and 3296units in 2014 and 2015 (p<0.0003). The greatest number and greatest reduction in RBC transfusions were within 72hrs of critical care admission (p<0.0001). Differences in mid and late transfusion did not reach statistical significance (fig.2). Reduced ABG sampling did not correlate with reduced transfusion (p=0.3) or with haemoglobin concentration at ICU discharge in any LOS group (p=0.24 ).
Implementation of a low volume restrictive sampling strategy was associated with a significant reduction in ABG sample volume but not in discharge haemoglobin or need for RBC transfusion in patients admitted to CICU. Reasons for this may include changes in transfusion trigger following publication of the TITRe2 study in 2015  and continued blood sampling for other diagnostic tests. We plan to re-evaluate after introduction of further measures to reduce burden of diagnostic sampling. Maximal benefits may be seen when strategies to reduce blood sampling volume are used in as part of a multimodal program of patient blood management.
REFERENCES: 1. Hajjar LA et al. JAMA. 2010 Oct 13; 304 (14): 1559-67. 2. Murphy GJ et al. N Engl J Med. 2015 Mar 12; 372 (11): 997-1008