Intravenous catheter aspiration for obtaining basic analytes during intravenous infusion.

The aspiration of blood through a functioning IV line to obtain samples for laboratory analysis was evaluated. Thirty-eight emergency department patients were studied. Each had an 18-gauge IV catheter placed and then received a 100-mL bolus of either normal saline, lactated Ringer's, or 5% dextrose in water. Two samples of blood ("first aspirate" and "second aspirate") were then aspirated from the IV catheter while one sample was obtained by venipuncture from the opposite arm (control). All three samples were then analyzed for CBC, electrolytes, BUN, creatinine, and glucose. Catheter aspiration succeeded in 30 of 38 attempts (79%). Three samples were hemolyzed, and five samples were unable to be fully aspirated. Results of paired t testing showed only occasional statistical significance and except for bicarbonate were not of clinical significance. This study suggests that catheter aspiration is a useful method of obtaining blood for certain laboratory tests in patients receiving IV infusions.