Whole blood clotting time, also known as coagulation time (CT) or Lee-White coagulation time, is the oldest but least accurate of the coagulation tests. It measures the time it takes blood to clot in a test tube. Because the sensitivity of the test is low, coagulation problems of mild to moderate severity are not apparent. Heparin prolongs clotting time; therefore, the test was once used to monitor heparin therapy. PTT or aPTT is currently used to evaluate such therapy.

• 4 to 8 minutes
  Because this test is relatively insensitive and difficult to standardize, a normal result does not rule out a coagulation defect.

• Heparin prolongs the whole blood clotting time.
• Traumatic venipuncture may lead to erroneous results.

• Evaluation of response to heparin therapy
  • Adequate anticoagulation is indicated by a clotting time of about 20 minutes.
• Signs of abnormal bleeding such as epistaxis, easy bruising, bleeding gums, hematuria, and menorrhagia
• Suspected congenital coagulation defect that involves the intrinsic coagulation pathway (e.g., deficiencies of factors VIII, IX, XI, and XII)

Nursing Care Before the Procedure

In general, client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• If the individual is receiving heparin anticoagulant therapy, the time and the amount of the last dose should be noted.

A venipuncture is performed and 3 mL of blood collected in a syringe and then discarded. A new syringe, glass or plastic, is attached to the venipuncture needle, and an additional 3 mL of blood is withdrawn. Traumatic venipunctures and excessive movement of the needle in the vein must be avoided if accurate results are to be obtained.

As the second sample is withdrawn, timing is begun with a stopwatch. The sample is immediately and gently transferred into three glass tubes (1 mL in each). The test tubes are placed in a water bath at 98.6°F (37°C) and are tilted gently every 30 seconds until a firm clot has formed in each tube.

Timing is completed when all tubes contain firm clots, and the interval is recorded as the clotting time.

Nursing Care After the Procedure

Care and assessment after the procedure are essentially the same as for any study involving the collection of a peripheral blood sample. Because the client may have a coagulation deficiency, maintain digital pressure directly on the puncture site for 3 to 5 minutes after the needle is withdrawn. Also, inspect the site for excessive bleeding after the procedure.

• Bleeding tendency: If anticoagulant therapy is administered, note and report bleeding from any area (skin, nose, mucous membranes; blood in urine, feces; excessive menses). Note results of the coagulation factor screen for deficiencies. Protect the skin, mucous membranes, and other organs from trauma. Test for occult blood in body secretions and excretions.