Up to 90% of peripheral intravenous catheters (PIVCs) fail and often result in post-insertion complications (such as thrombosis), causing pain and discomfort for the patient, delayed treatment, and additional health care costs. Current research suggests that the infusion rate/velocity of saline administered through different sized catheters may be capable of causing endothelial damage and platelet activation due to the shear stress/shear rate generated at the catheter tip. Therefore, this thesis sought to investigate whether flushing saline at clinical infusion rates of 1mL/sec through smaller sized PIVC gauges (i.e., 22G) causes greater endothelial injury, platelet activation and coagulation (i.e., thrombotic risk) than larger sized PIVC gauges (i.e., 18G). A total of 12 participants were bilaterally cannulated with an 18G and 22G PIVC. Both catheters were flushed hourly with 10mL of saline (0.9% NaCl) at a fixed infusion rate of 1mL/sec, over a 5hr period. Post saline infusion (i.e., fluid shearing of the cephalic vessel wall and blood), whole blood (WB) was collected at baseline (0hr), 1hr, 3hrs and 5hrs, to measure endothelial injury (tissue factor (TF) release), platelet activation (CD62p and PAC-1), and coagulation (activated partial thromboplastin time (aPTT)/prothrombin time (PT) and serum calcium (Ca2+)). [...]