The effects of abnormal blood pressure on arterial sampler filling times.

Background: Sampler filling time begins with the initial flash of blood in the needle hub until the preset sampler volume is obtained. Previous studies have shown statistically significant differences between arterial and venous sampler filling times, but included only a few subjects with abnormal blood pressures.

Objective: To determine whether the time required to fill a vented arterial sampler is an accurate indication of a successful arterial blood sample in adults with abnormal blood pressure. We hypothesized that mean arterial pressure and arterial sampler filling time would have a negative correlation, and that venous sampler filling time would be significantly longer than arterial filling time.

Methods: We studied 40 subjects: 25 arterial subjects, and 15 venous subjects. The arterial subjects included 3 groups: hypertensive, hypotensive, or normal. During the arterial and venipuncture procedures, we measured sampler filling time and recorded blood volume. The PO2 of the samples was measured. Additionally, blood pressure and SpO2 were measured in the arterial group.

Results: The mean sampler filling time was 220.4 s/mL for the venous group, and 18.1 s/mL for all 3 arterial groups combined. There were significant differences between each mean arterial sampler filling rate and mean venous filling rate (P < .001). There were no significant differences in mean sampler filling rate between the arterial subgroups (P > .99). The correlation between mean arterial pressure and filling rates was 0.06 (P = .38).

Conclusions: There is a significant difference between arterial and venous filling rates. There was no relationship between filling time and abnormal mean arterial pressure. Regardless of the arterial pressure, the arterial sampler filling time can be used as an indicator of a successful arterial puncture at the bedside.