Medtronic LR-ACT Instrucciones De Uso página 8

ACTCART_CH_EN.FM 6/1/04 9:51 am
UC199600212b ML
7 x 9 inches (177.8 x 228.6 mm)
LIMITATIONS OF THE PROCEDURE
factor deficiencies, sample activation, consumptive coagulopathies, excessive sample dilution, and sample temperature) and
should be taken into account when interpreting the results of activated clotting time tests.
Duplicate channel results should fall within 10% of each other for baseline (unheparinized) samples and within 12% of each
other for extended or heparinized samples.
Sample Calculation:
Ch 1 clotting time = 210 seconds
Ch 2 clotting time = 200 seconds
Mean clotting time = 205 seconds
Difference = 10 seconds
12% of the mean = 25 seconds
The difference of 10 seconds is less than 12% of the mean, 25 seconds. These results are acceptable.
11 LIMITATIONS OF THE PROCEDURE
To obtain accurate and consistent activated clotting times, the following conditions must be observed:
1. Both the instrument heat block and cartridge temperature should be at 37 ° ± 0.5 °C (98.6 ° ± 0.9 °F). (The cartridge
will come to temperature in approximately 3 minutes in the instrument heat block.)
2. Activator must be thoroughly resuspended.
3. Blood must be free of tissue thromboplastin and run as soon as possible after drawing (fresh drawn), or stored in a
non-activating, capped container (citrated whole blood).
4. Patient diagnosis and medications should be noted. Medications can alter clotting times.
unexplained abnormal values should be redrawn and retested. If the results are still abnormal and no cause is
apparent, a sample should be citrated and sent to your clinical lab for special coagulation analysis.
5. To optimize precision, all technique variables should be held constant from test to test.
6. Methodologies used in cardiopulmonary bypass surgery continually change as does the population demographics of
bypass patients. Patient sensitivity to heparin, dilution of clotting factors by the extracorporeal circuit, the use of citrated
blood products, the use of antiplatelet drugs, hypothermia, fluctuating calcium levels, a change in platelet function or
count, unknown coagulopathies, etc., are influenced by these changes.
frequently due to a desire to limit the use of heterologous blood products, can lead to postsurgically hemodiluted
patients. This dilution can be great enough that clotting times, as reflected by the activated clotting time, are extended
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due to the dilution. In severe instances, the dilution may be so great that measurable clotting does not occur. In this
case, the patient may experience postoperative bleeding due to a lack of plasma clotting factors. The adequacy of
plasma clotting factors cannot be determined by the patient's hematocrit. Frequently, washed cells are administered
to the patient without compensating for lost plasma. If the HR-ACT fails to clot following reversal of heparinization and
a protamine titration indicates no heparin is present (Heparin Assay is not affected to the same degree by dilution as
is an activated clotting time), a dilutional coagulopathy is a strong possibility. If a presurgical coagulation panel is
available for the patient, either an activated partial thromboplastin time (aPTT) or a prothrombin time (PT), a
comparison of the pre- and post-surgical values should indicate an extension. The degree of extension is patient-
related and cannot be judged by reference to normal control clotting time ranges. An aPTT which changes from the
low normal range to the high normal range is indicative of a significant change in patient coagulation characteristics.
Warning: Due to the formulation of the HR-ACT cartridge, it should not be used to monitor regional anticoagulation achieved
by infusing citrate.
For instrument precautions and limitations, consult the operator's manual.
12 EXPECTED VALUES
Clotting times using the Medtronic Low Range Activated Clotting Time Cartridge (LR-ACT), the Medtronic Recalcified
Activated Clotting Time Cartridge (RACT) and the Medtronic High Range Activated Clotting Time Cartridge (HR-ACT) were
determined on 3 normal volunteers. Table 3 is a sample of an individual response to heparin using 3 donors. The HR-ACT
and the LR-ACT cartridges were run with fresh drawn whole blood, and the RACT cartridges were run with citrated whole
blood (3.2% sodium citrate). Response to an increased concentration of heparin may vary between individuals. Each
laboratory/facility should establish their own range based on their local demographics.
6 English
231036-00
Medtronic Confidential
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Samples which give
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Excessive blood dilution during bypass,
Instructions for Use
CS009