Blood samples drawn from IV catheters have less hemolysis when 5-mL (vs 10-mL) collection tubes are used.

Introduction: It is common practice for emergency nurses to draw blood for laboratory analyses into vacuum tubes from newly inserted intravenous (IV) catheters, even though this technique has been associated with an increase in sample hemolysis. No clinical nursing studies have documented the effect of collection tube size on hemolysis of samples obtained via IV catheters.

Objective: To determine whether there is a difference in the hemolysis rate of blood samples drawn from IV catheters comparing 5-mL vacuum collection tubes to 10 mL vacuum collection tubes.

Setting: The study was conducted at the Emergency Department, Summa Health System, Akron, Ohio. Method This study used a 4-group, 2-period crossover design randomly assigning the order of the vacuum tube drawn. With the crossover design, each patient served as his own control. Upon receiving orders to start an IV and draw blood, each of 12 study nurses obtained an envelope with 2 vacuum tubes randomly assigned as to which tube should be drawn first and which tube should be drawn second. Samples were analyzed for hemolysis using a Hitachi automated spectrophotometer as well as by visual inspection.

Data Analysis: A linear mixed model was used to test the main hypothesis of vacuum tube type effects on hemolysis.

Results: The 5-mL tubes showed significantly lower hemolysis than the 10 mL tubes ( P <.0001) with a substantial effect size of .6 standard deviation units.

Conclusion: The risk of hemolyzing blood drawn from IV catheters can be significantly reduced by using 5-mL rather than 10-mL collection tubes.