Date on Master's Thesis/Doctoral Dissertation

5-2008

Document Type

Master's Thesis

Degree Name

M.S.

Department

Mechanical Engineering

Committee Chair

Sharp, Michael Keith

Subject

Hemolysis and hemolysins; Hypodermic needles

Abstract

Hemolysis, the major cause for specimen rejection in clinical laboratories is defined as the rupture of red blood cell membranes, resulting in the release of hemoglobin into the plasma. Blood flow in needles causes hemolysis resulting in complications such as incorrect assay results [13,14], repeated painful blood draws [4,9,13] and also the release of hemoglobin into the plasma, which is toxic to the kidneys [18]. Hemolysis mainly occurs due to high fluid stresses that act on the red blood cells in blood flow through the needle [22]. Highest stresses during blood draws act near the downstream edge of the needle entrance. In this project, the needle has been modified with a more rounded entrance to reduce the effect of the stresses acting near the tip. Experiments were also performed with needles of beveled entrance to reduce the hemolysis. This thesis discusses in detail, experiments conducted with 16G and 20G standard and modified needles in both reverse and normal orientations at three different pressures. Blood was drawn into a syringe, then the needle is attached to it and the assembly is placed in a fixture. The fixture was designed to hold the syringe in place and apply desired pressure on the syringe. The blood flowing out of the syringe was collected in a test tube and this process was repeated for all the combinations of pressures and needle orientations viz. normal and reverse. The collected test tubes were then centrifuged and the plasma was removed and analyzed in a spectrophotometer. Results were tabulated and graphs were plotted to compare the hemolysis in the test and control needles. ANOVA p-values clearly indicated that the rounded entrance significantly reduced hemolysis compared to the standard needles for the 20G size in the reverse orientation at all three pressures (p-values at 20psi, 35psi and 50psi were 0.053, 4.60E-08 and 1.00E-08, respectively). There was also a significant relation between the 16G with rounded entrance and the standard needles in the reverse orientation (p-values were 0.017, 0.004 and 0.001 at l5psi, 30psi and 45psi, respectively), but no significant relation for the 16G needles with beveled entrance.

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