Fresh whole blood transfusions are a powerful tool in prehospital care; however, the lack of equipment such as a scale in field situations frequently leads to collections being under- or overfilled, leading to complications for both patient and physician. This study describes two methods for simple, rapid control of collection bag volume: (1) a length of material to constrict the bag, and (2) folding/clamping the bag.
Whole blood collection bags were allowed to fill with saline via gravity. Paracord, zip-tie, beaded cable tie, or tourniquet was placed around the bag at circumferences of 6 to 8.75 inches. A hemostat was used to clamp folds of 1 to 1.5 inches. Several units were drawn during training exercises of the 75th Ranger Regiment with volume controlled by three methods: vision/touch estimation, constriction by paracord, and clamping with hemostat.
Method validation in the Terumo 450-mL bag indicated that paracord, zip-tie, and beaded cable tie lengths of 6.5 inches or clamping 1.25 inches with a hemostat provided accurate filling. The volume variance was significantly lower when using the beaded cable tie. Saline filling time was approximately 2 minutes. With the Fenwal 450-mL bag, the beaded cable tie gave best results; even if incorrectly placed by one/two beads, the volume was still within limits. In training exercises, the use of the cord/clamp greatly reduced the variability; more bags were within limits.
Both constricting and clamping allow for speed and consistency in blood collection. The use of common cord is appealing, but knot tying induces inevitable variability; a zip/cable tie is easier. Clamping was quicker but susceptible to high variance and bag rupturing. With proper methodological training, appropriate volumes can be obtained in any environment with minimal tools.
LEVEL OF EVIDENCE
Therapeutic/care management study, level IV.