Relationship between arterial and venous activated partial thromboplastin time values in patients after percutaneous transluminal coronary angioplasty.

This quasi-experimental study was conducted to determine whether reliable activated partial thromboplastin time (APTT) values could be obtained from samples taken from indwelling arterial catheter lines. The 30 subjects, who were receiving heparin infusions after a percutaneous transluminal coronary angioplasty (PTCA), had femoral intraarterial lines. With use of a counterbalanced design, APTT values determined in two serial samples of venous and arterial blood were compared for the 30 subjects. The venous blood samples were drawn at the same time as the comparable arterial blood samples. The arterial blood samples were withdrawn after discarding arterial blood equal to four or six times the indwelling catheter volume. A significance level of 0.01 was established to increase statistical control. A histogram was developed from the differences between the arterial and venous blood samples for each of the two groups (four times and six times the discard volume). The histogram indicated that three of the 30 subjects had arterial-venous APTT differences that exceeded 19 seconds when four times the discard volume was used. In the samples where six times the discard volume were used, only one person had an APTT reading greater than 8 seconds. Paired t tests revealed statistically significant differences between the arterial and venous APTT values (t = 2.95, df = 29, p less than 0.01) for discards of four times the catheter dead space volume, whereas no statistically significant difference was found between the arterial and venous APTT values (t = 2.62, df = 28, p greater than 0.01) for discards of six times the dead space volume.(ABSTRACT TRUNCATED AT 250 WORDS)