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The first specific, recognizable hemostatic mechanism is a process known as vasoconstriction. Vascoconstriction is initiated by chemical signals stemming from a damaged area of a blood vessel. Vasoconstriction, or vascular constriction, immediately reduces the quantity of blood flowing through the damaged area. Its action is the physical decrease in the size of the vessel and the redirection of blood flow around, and away from, the damaged area. Vasoconstriction is akin to putting a clamp on a pliable piece of plastic tubing. Vasoconstriction also allows for a closer interaction of the coagulation proteins and platelets with the damaged vessel wall. In addition, the epithelial cells lining the vessel also contract, which allows plasma to leak from the injured area. This is part of our normal inflammatory reponse and is the reason for swelling at the site of an injury. Vasoconstriction is an exceedingly important hemostatic mechanism as it prepares the damaged vessel for subsequent repair activities. These activities will be discussed next.

Julie Smith, a newly certified phlebotomist at Northlake Hospital, entered a patient's room on the third floor for a routine blood draw. The patient was an elderly woman who had very small fragile veins. Julie therefore decided to use a safety butterfly needle attached to a Vacutainer tube in order to draw the blood. When Julie was finished with the venipuncture, she detached the butterfly needle from the Vacutainer, and approached the Biohazard needle disposal box. She noticed that the disposal box was full , but decided to try to fit the butterfly into the box anyway. Holding the butterfly by the tubing, she tried to push the butterfly into the box. The needle suddenly recoiled and stuck Julie's finger. Julie left the patient's room in a panic and headed back to the lab to report the needle stick injury.

Fill blood collection tubes completely (until vacuum is exhausted) to ensure the correct blood to anticoagulant ratio necessary for accurate patient results. Specimens may be rejected by the laboratory if the tube is short-filled or over-filled. To avoid short-filling of tubes, the phlebotomist must ensure that the blood flow stops completely before removing the tube from the needle. When using a winged device (butterfly) to collect blood for coagulation studies (e.g., protime, aPTT), the phlebotomist must draw a light blue top "waste" tube before attaching another light blue top tube for testing. If the air in the tubing of the winged device is not displaced into a waste tube and is drawn into the tube used for testing, the tube used for testing will short-fill. The laboratory may reject the specimen because of invalid blood to anticoagulant ratio.

A light-blue top tube (a blood collection tube containing 3.2% sodium citrate) that will be used for coagulation testing must be filled to completion. Under-filling the tube changes the ratio of blood to anticoagulant. This can affect the accuracy of coagulation tests that are performed using this specimen. If a winged blood collection device (butterfly) is used to collect a light-blue top tube for coagulation studies, a waste tube should be drawn first, if the coagulation tube is the first tube to be collected for patient testing. The waste tube must also be a light-blue top tube or a tube that contains no additives. This waste tube is drawn first to remove the air in the tubing of the winged collection device. Once blood flows through the tubing, the waste tube can be removed and discarded. The waste tube does not need to be completely filled. If the air is not displaced from the tubing into a waste tube, it will be drawn into the tube used for testing and cause a short-fill of the tube. Less volume of blood in the tube alters the required blood to anticoagulant ratio needed for coagulation studies.

If preliminary testing suggests hemolysis or if the results are misleading, additional testing may be required. If human error has been ruled out during the clerical check, repeat ABO/Rh testing should be performed on the unit of blood or its segment and the pre-transfusion sample to detect any sample mix ups and clerical errors. Antibody detection studies should be performed on the pre- and post-transfusion samples to look for any unidentified antibodies. If an antibody is identified, the donor cells should be tested for the corresponding antigen. The crossmatch should be repeated with pre-and post-tranfusion specimens using the indirect antiglobulin test (IAT). An incompatible crossmatch with the pre-transfusion sample indicates an original error, either clerical or technical. Incompatibility with only the post-transfusion sample indicates a possible anamnestic response, as in a delayed hemolytic transfusion reaction (DHTR), or sample misidentification. The patient's first voided urine specimen should be examined for the presence of free hemoglobin. The patient's bilirubin levels may also be evaluated. A change from normal pale yellow serum to a post-transfusion bright or deep yellow serum should prompt an investigation for hemolysis. The maximum concentration of bilirubin following hemolysis is not usually detectable until 3 to 6 hours after transfusion. The hemoglobin and hematocrit can be tested to detect a drop in hemoglobin or failure of the hemoglobin to rise after transfusion. Important information about physical or chemical hemolysis may be gained from examining the returned unit bag. If hemolysis is present in the bag or tubing, a process which affected the blood, such as inappropriate warming or faulty infusion pump, should be suspected. If bacterial contamination is suspected, the unit can be cultured. A positive culture indicates a reaction due to bacterial contamination.