What quality assurance indicators are best to use for perioperative blood salvage?
A colleague reports that in the early 1990's, she helped to set up a perioperative blood salvage program. As part of that program's quality control they measured the total protein of the final salvaged products. They also assessed hematocrit of the final product to assess the machine's abilility to concentrate red cells. She is now in a new job situation where the QA entails measuring hematocrit, measuring changes in electrolytes, as well as the color of the contents of the waste line (subjective information). She has reviewed the AABB standards and some literature, and has found no consensus as to the best quality indicators to measure. She is curious to learn know how other institutions approach perioperative blood salvage quality assurance.
The following comments have been received.
ADDENDA Sept. 19, 2004
- A colleague in Virginia reports that they use a cell-saver for which they calculate the percent efficiency of processing using the reservoir volume, albumin and hematocrit against the same parameters for the reinfusion sample. They also check for qualitative plasma hemoglobin, schistocytes in the reinfusion sample; they also culture the flush fluid before the procedure begins, since in her experience the culture of the shed blood usually 'grows something'. She has graciously shared a copy of their QC SOP .
- A transfusion medicine physician in Rochester, Minnesota reports that in her opinion the ultimate goal of performing quality indicators/quality control for the peri-operative blood collection and reinfusion process is to ensure the consistency of products that are "manufactured" by this process and to potentially detect significant failures that are not otherwise evident visually. Given the function of cell salvage instruments, in her opinion there are two important areas to check: the ability to concentrate red blood cells and the ability to remove supernatant materials. Instrument and/or operator variability and failure would affect these abilities. In her experience, hematocrit determinations on the final product are the most accepted means of quality control - this checks the hemoconcentration function and if acceptable, one can make some assumptions about the effectiveness of supernatant removal under routine conditions. The frequency of performing quality control is highly variable depending on the type of equipment, the consistency of the products produced, and the feelings of the individual perioperative program. Processing variables that will alter results include the pump speeds used for fill, wash, and return as well as the amount of wash solution used. All of these need to be considered when determining frequency and acceptable ranges for hematocrit.
She adds that assessing the removal of supernatant materials is more challenging as the concentration in the final product typically depends on the concentration in the blood prior to processing since devices can remove only a certain percentage of what is there. Therefore it is difficult to set an acceptable range of concentration for the final product. An example is free hemoglobin - most devices will remove at least 90% of free hemoglobin during processing. For many cardiac and vascular cases, reaching a free hemoglobin of <200 mg/dL in the final product is achievable. However, in her experience, orthopedic cases are more difficult to achieve this low level of free hemoglobin due to the high concentrations in the pre-processed blood. She reports having seen levels as high as 1500 mg/dL in the reservoir blood. One also has to consider that there is some ongoing low-level hemolysis that also occurs during processing. The same concepts apply to electrolytes, albumin, protein, etc. One parameter that could be measured in the final product would be heparin if it is used for anticoagulation. However, in her experience measuring this drug in processed blood is difficult for the lab depending on the analytical method, due to the lack of plasma. This is an area of QC with no consensus among experts.
For cell salvage, her institution does hematocrit testing on products from 4 random cases per month. After years of experience, they have observed that under routine conditions (pump speeds of 300 mL/min for fill, wash, return and 1.5 L wash), the hematocrit of their processed blood consistently runs in the 48-65% range. She therefore feels comfortable with random monthly testing. They do not QC those cases where they deliberately change pump speeds or wash volume due to the clinical circumstances (such as massive bleeding), as they have experience that these results will be different and they are knowingly changing product quality to meet specific patient needs. They formerly measured heparin levels, looking for values <=0.3 units/mL, but have stopped due to method problems.
They limit measuring albumin and free hemoglobin concentrations to situations where there is a specific question about product quality (reaction or abnormal appearance), instruments are returned from major repairs, or they are evaluating a new device. They consider albumin removal to be the gold standard for supernatant material as it will not be changed by RBC hemolysis.
For every case, they watch the color of the waste line. If the waste line doesn't clear by the end of washing, they will consider increasing the wash volume and think about what else might be causing the problem.
ADDENDA Sept. 30, 2004
- A transfusion medicine physician at an academic medical center in Minneapolis reports that their approach consists of a monthly examination of a single product for the following attributes: potassium (action level >5 mmol/L); plasma hemoglobin (action level > 700 mg/dL); Hb (action level if <13 g/dL); hematocrit (action level if <39%). In the past they also measured plasma heparin and performed a single monthly test for bacteria.
ADDENDA Oct. 6, 2004
- A colleague from HemoCue, Inc. comments that AABB Standards for Perioperative Autologous Blood Collection and Administration mentions the measurement of free hemoglobin as a test to consider, and that as mentioned previously, one of the ways to monitor the efficiency of cell washers during blood salvage is to calculate the percentage of free hemoglobin removed. She reports that a poster was presented at AABB in 2001 describing the evaluation of at least one system for this purpose. (Transfusion 2001;41 (Suppl):100S. pdf file)
ADDENDA Jan. 13, 2009
- A pathologist in Colorado wants to know the current standard to evaluate the quality of blood that is salvaged intra-operatively with regard to free hemoglobin. He points out that this e-Network Forum discussion listed 700 mg/dL as an action value in a posting from 2004 from an academic medical center in Minnesota. The inquiring colleague wonders if 700 mg/dL can still be considered valid. He remains concerned at the high levels of free hemoglobin in salvaged blood. He has only found one article in the literature suggesting that patients receiving multiple units of salvaged blood may have an increase in creatinine suggesting some renal impairment which could be attributable to free hemoglobin. There are some articles suggesting the administration of recombinant haptoglobin to counter this effect. He wonders if anyone has more information on this topic.
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