How to Monitor Heparin During Surgery

Heparin is an anticoagulant used to prevent or treat excessive clotting within the body's blood vessels. The partial thromboplastin time (PTT) test, also called a "bleeding time" in the clinical lab, is a test used to monitor heparin therapy to make sure that not too much of it is being used. When people on heparin therapy undergo surgery, or if the surgery requires heparin (as is the case when a heart-lung machine is used), PTT tests are done throughout the surgery to make sure the patient will have the ability to clot and heal after surgery.

Things You'll Need

• Blood collection kit
• Light blue (sodium citrate) test tube
• Coagulation time analyzer
• Personal protection equipment

Instructions

Blood Collection

1. Collect a blood sample by using a blood collection kit, usually consisting of a syringe, needle assembly, cotton swab, and alcohol or iodine cleaning swab. If you are using a tube ("butterfly") needle assembly, empty about 1 milliliter of blood into a discard tube before filling the light blue top tube.

2. Make sure the light blue top tube is properly filled. For accurate blood coagulation time studies, a correct ratio of blood to sodium citrate must be in the tubes.

3. Apply pressure for an extended period of time to the site of the blood draw, if it was done through a venous phlebotomy. This is to make sure a clot forms and the site does not continue to bleed after the sample is taken. If a port or IV line was used, then no pressure is necessary.

Perfom the PTT Test

1. Calibrate and run quality control on the blood coagulation analyzer according to the analyzer's manufacturer instructions. Only then may you continue to the next step.

2. Insert the patient sample into the analyzer for testing. Make sure to follow procedures since any deviation may alter the results. Always use caution when opening the tube for testing (if necessary) and when operating the analyzer.

3. Report the results to the surgical staff immediately. It is of the essence that the surgical team be aware of the PTT results since the results dictate how heparin and other medications are used during the surgery. Any critically abnormal results should be reported immediately per your institution's standard operating procedure.

Tips & Warnings

• Aim for the turn-around time from the moment the test is ordered to when you deliver results to be under 15 minutes. This guarantees that the result is relevant to the surgery since a result reflecting a moment in time longer than that may not be in the best interest to the patient's surgery. Also, always collect what is called a "rainbow" of blood tubes while you are collecting a stat or any other sample for immediate analysis. This will often come handy since some of the results you report may dictate a different test to be done as well. For example, a high PTT result, indicating poor clotting ability, may require a platelet count or a crossmatch for blood or blood components.

• Always use personal protective equipment and standard precautions when handling blood and other laboratory samples. Make sure you are immunized against Hepatitis B if you work with these samples to minimize the chance of being infected with the virus if you are accidentally exposed. Never report results if the calibration and quality control of any analyzer fails.

References

• Partial Thromboplastin Time
• Anticoagulant Therapy Monitoring