Detecting Secondary Medication Infusion Errors via Spectrophotometry

Although intravenous (IV) smart pumps (IVSPs) are widely used to reduce medication errors, many IVSPs continue to depend on passive methods, such as an adequate hydrostatic head height differential (HHD), for the delivery of secondary medications. An adequate HHD ensures that the fluid level inside the secondary bag is sufficiently higher than the fluid level inside the primary bag, which is accomplished by lowering the primary bag with a supplied hanger to ensure the secondary medication is delivered preferentially. Poor clinical adherence to this requirement is common, conferring risk of medication dilution and subtherapeutic dosing. As prior observational studies have not quantified this risk, the current work sought to develop a laboratory protocol to measure delivered secondary medication concentration across three hanger configurations (full, half, and zero hanger) over a range of flow rates. Both hanger configuration (P < 0.0001) and programmed flow rate (P < 0.0001) significantly affected the delivered concentration. The zero hanger configuration, characterized by an HHD of zero, caused severe and statistically significant underdelivery of the secondary fluid, often delivering less than one-half of the intended concentration due to unintended dilution. The full and half hanger configurations maintained acceptable accuracy (±5% deviation) up to 250 mL/h, though concentration delivery accuracy decreased for the half hanger configuration at 400 mL/h. This study validated a method for directly measuring secondary medication delivery, providing evidence to inform safer clinical practice and device development.