Date Approved


Graduate Degree Type


Degree Name

Nursing (M.S.N.)

Degree Program

College of Nursing

First Advisor

Patricia Underwood

Second Advisor

Johnine Calahan

Third Advisor

Steven Merrill


Drawing blood from indwelling heparinized arterial catheters is a common procedure in critical care units. The accuracy of coagulation studies drawn from heparinized arterial lines has been a source of controversy and divergent results of research studies. The discarding of blood to provide an uncontaminated specimen is a concern as a source of infection for health care workers. This study evaluates the accuracy of aPTT results drawn from the Lab-Site pressure tubing system which provides a closed system that eliminates blood discard. Blood was obtained from radial artery catheters connected to the Lab-Site system and compared to specimens obtained simultaneously, by venipuncture. The paired t-test indicated no significant difference between the arterial and venous samples. The Pearson product moment correlation of 0.619 indicated good correlation between arterial and venous values. The mean difference between the arterial and venous aPTT results was 1.49 seconds with S.D. of 3.925. The researcher concluded that accurate aPTT results can be obtained from heparinized arterial lines when specific procedures are followed.


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