DETECTION OF INTRAVENOUS FLUID EXTRAVASATION USING RESISTANCE MEASUREMENTS

Resistance to fluid infusion can be derived from measurements of press ure at two or more flow rates. We measured resistance in 31 patients u sing a pressure-monitoring infusion pump (Model 560, IVAC) by recordin g pressure at five flow rates (0, 50, 100, 200, and 300 mL/hr), and co mputing resistance as the slope of the pressure versus flow curve. Res istance was measured subcutaneously (R-tissue) and intravenously (R-ve in) immediately after unsuccessful or successful IV catheter placement . In all patients, R-tissue was always greater than R-vein. The differ ence ranged from 23 resistance units (RU) to 4166 RU, with a mean diff erence of 1147 RU (p < 0.0001, Student's t-test). Unpaired analysis of the data was performed to assess the ability of resistance to indicat e extravasation in the absence of prior R-vein measurement. The median Value for R-vein was 62 RU (range -13.6 to 420 RU), and for R-tissue, 544 RU (range 65.7 to 4170 RU). Receiver operating characteristic (RO C) analysis revealed that a 200-RU threshold detected infiltration wit h 0.90 sensitivity and 0.91 specificity. We conclude that elevated res istance during fluid infusion is an important early and easily measura ble finding in fluid extravasation.