Intravenous smart pumps (IVSPs) are widely used in clinical settings to improve medication safety. However, accurate delivery of secondary medications remains highly dependent on correct physical setup, creating a critical yet underrecognized source of dosing error. Proper secondary infusion requires the manufacturer-provided hanger to be fully extended to maintain an adequate head-height differential between primary and secondary fluids. Failure to achieve this configuration can result in unintended mixing of primary and secondary fluids, leading to medication under-delivery that may go undetected by clinicians and contribute to subtherapeutic dosing and reduced treatment efficacy. 

This study investigates how hanger configuration and programmed flow rate influence secondary medication delivery accuracy using spectrophotometry. A controlled laboratory protocol was developed to simulate clinically relevant infusion conditions using a linear peristaltic IVSP, with Patent Blue VF dye serving as a model secondary medication. Three hanger configurations were evaluated: fully extended (FH), half hanger (HH), and zero hanger (ZH), across multiple programmed flow rates. Delivered medication concentration was quantified at discrete infusion volumes using absorbance measurements and Beer-Lambert analysis. 

Results demonstrated that hanger configuration significantly affected delivered concentration, with inadequate head-height differential (ZH) producing substantial under-delivery and unintended mixing with primary fluid. FH and HH configurations maintained acceptable delivery accuracy at lower flow rates, although reduced accuracy was observed at higher flow rates in HH conditions. 

By directly quantifying infusion errors, this study addresses a critical gap in prior observational research and provides evidence to inform safer clinical practice, device design, and patient safety guidelines.