Effect of intravenous infusions on laboratory results in blood specimens drawn proximal to the insertion site of an intravenous canula

Abstract Background: Blood sampling contralateral to the insertion site of an intravenous line is always first choice. When blood must be drawn proximal to an i.v. insertion site, dilution and contamination by the infused substance can occur. To study the effects of obtaining blood specimens proximal to a discontinued intravenous line a clinical trial in a small community hospital was designed. Methods : Ten patients received an intravenous infusion with sodium chloride 0.45%/dextrose 2.5%. Bloodsamples were taken simultaneously from the iv-arm and the control-arm with the infusion running and 1, 3, and 5 min after shutting off the infusion. Results: Between-arm differences are significant for all analytes while the infusion is running, but not after the infusion is discontinued. Wide ranges in differences in terms of percentage exist for many analytes 1 min after shutting off the infusion, and for glucose also 3 min after shutting off the infusion. Conclusions: A three minute interval is recommended when drawing blood proximal to a shut-off infusion. Longer intervals may be advisable for analytes present in the infused substance.