A colleague who works with the Hong Kong Red Cross Blood Transfusion Service asks how frequently a 450 mL unit of donated blood should be mixed while it is being collecting, if an electronic mixer is not used.  The inquiring colleague comments that some individuals recommend they mix the blood every 30 seconds while it is being collected. However, she cannot find evidence to support this recommendation.  Can anybody enlighten her?

The above question was previewed by an American physician who has had many years of experience with the American Red Cross blood collection system. He reports that 21CFR606.100(b(5) only requires that there be a procedure for blood collection. He did not find a specific answer to the above question addressed in AABB Standards. He did find three comments in the 14th edition of the AABB Technical Manual that seem to be germane to the question from Hong Kong: Page 97: "During collection the blood should be mixed with the anticoagulant." Page 163: "Although the target collection time is usually 4 to 10 minutes, one study has shown ... [it] to be satisfactory after collection times of up to 15 minutes. There should be frequent, gentle mixing of the blood with the anticoagulant." Page 736: "Mix blood and anticoagulant gently and frequently throughout the donation process." He reports that the national ARCBS procedure says to "frequently mix the blood and anticoagulant in the primary container", and that the American Red Cross trains their staff to mix 4-5 times during the process if the blood is flowing freely, and if a slow flow to mix more frequently (not quantified). Combining information in the AABB Technical Manual with that in ARCBS training, and doing the math, he concludes that mixing four to five times during a four to ten minute period gives a range of from once every 48 seconds to once every 150 seconds. He summarizes saying that the intent is for the anticoagulant in the collection set to come in contact with all the collected blood entering the set before clots form. However, while the frequency of collected blood containing clots is very low, anecdotally, in the experience of the American physician, he is aware that blood collected using an automated mixer can contain clots, and blood collected without being mixed at all during collection might not contain any clots.

The following comments have been received.

ADDENDA Apr. 21, 2006

1. A colleague who works with a mobile blood collection team at an academic center in Los Angeles reports that during busy blood drives (for example at high schools), they rely on manual mixing collected blood, but are 'lucky to be able to mix 4 times for most donors with good veins (and good flows)'. However, their bag manufacturer recommends that they mix the blood every 45 seconds as it is being collected. He acknowledges that it is problematic for them to mix the collected blood as often as recommended during busy drives. He shares his opinion that using mechanical mixers is the best option for getting the blood mixed consistently. Such equipment has the added benefit that it can be programmed to draw for a maximum time (such as 15 minutes), which can stop unacceptably slow draws.

2. A colleague who helps to oversee 'Procedure Development and Training' for a multi-state blood collection organization in the US (not the American Red Cross) reports that in the "Guide to the preparation, use and quality assurance of blood components" 12th edition issued by the Council of Europe Chapter 2, point 5(b), it states "when manual mixing is used, the blood bag must be inverted every 30-45 seconds. When an automated mixing is used, an appropriately validated system is required. It is also important to review bag manufacturer’s inserts as well as the equipment manual of the collection device."  In addition, he comments that at least one US blood bag manufacturer states “Mix blood and anticoagulant frequently during collection for example, once every 45 seconds, and immediately after collection”.

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator