A comparison of hemolysis rates using intravenous catheters versus venipuncture tubes for obtaining blood samples

The primary purpose of this study was to compare the rate of hemolysis in blood samples obtained by an i.v. catheter versus the rate in samples obtained by venipuncture (Vacutainer tubes and needles; Becton Dickinson Vacutainer Systems, Franklin Lakes, N.J.). Subsequently, variance in i.v. catheter diameter was reviewed to determine its influence on hemolysis rate of i.v. catheter aspirate.

A randomized, prospective study was used to evaluate hemolysis differences between the two blood sampling methods. A descriptive, retrospective review of study data was used to evaluate the importance of the variable i.v. catheter diameter.

The study group consisted of patients who came to the emergency department and required both an i.v. infusion and blood sampling for determination of electrolyte levels and complete blood cell count. Pediatric patients (younger than 16 years) were excluded. The ED patients who qualified for the study were randomly assigned to either group A or B. The blood samples for patients in the A group were obtained through the i.v. catheter at the time of insertion. The i.v. catheters ranged in size from 24 gauge to 14 gauge. Patients in the B group also had insertion of an i.v. line, but their blood samples were obtained by Vacutainer venipuncture at a separate site. The Vacutainer needle was standardized at 21 gauge. All blood samples were collected by one of seven experienced ED nurses. The nurse who collected the blood sample for an study patient was responsible for result follow-up.

A total of 165 patients participated in the study; 87 patients were assigned to the A (i.v.) group, and 78 patients participated in the B (venipuncture) group. In group A a total of 12 of 87 (13.7%) blood samples hemolyzed. Hemolysis occurred in 3 of 78 (3.8%) of group B samples. These findings were statistically significant (p < 0.05). When we examined the variable i.v. catheter diameter, we noted a lower incidence of hemolysis with larger catheter diameters: 24 gauge (100%), 22 gauge (25%), 20 gauge (15%), 18 gauge (10%), 16 gauge (0%), 14 gauge (0%). This findings was statistically significant (p < 0.05).

Hemolysis of blood samples obtained by an i.v. catheter was significantly higher than when blood was obtained through Vacutainer venipuncture. There is an inverse correlation between i.v. catheter diameter and the rate of hemolysis.