Contamination levels in blood samples drawn from the injection intravenous line.

Purpose: Securing two intravenous lines, one for injection and one for blood sampling, can be nearly impossible in compromised patients, therefore, a need exists to quantify the potential error when simplified techniques are employed.
Method: Two venous catheters were placed. 2-deoxy-2-[18F]fluoro-glucose (FDG) was infused through one of the catheters. Venous blood samples were drawn from each line. Triplicate aliquots of plasma were analyzed in duplicate.
Results: Concentrations from the infusion line were 2.0% higher than the concentrations from the noninfusion line. The average error was 3.3%, 2.0%, and 0.7% higher for the first, second, and third samples, respectively.
Conclusions: Blood sampling through the infusion catheter is a viable alternative to the placement of separate venous catheters. Sampling from the injection catheter, even with tubing flush and replacement, will potentially incur small (generally < 10%) over-estimations in concentration in initial samples. Subsequent sampling reduces the error to essentially zero by the third sample.