DETECTION OF INTRAVENOUS FLUID EXTRAVASATION USING RESISTANCE MEASUREMENTS David A. Scott, MB, BS, FFARACS, John A. Fox, MD, Beverly K. Philip, MID, LeonardJ. Lind, MD, Avital'Cnaan, PhD 1, Mary Anne Palleiko, RN, John M. Stelling, MPH, and James H. Philip, MEE, MD Scott DA, Fox JA, Philip BK, Lind LJ, Cnaan A, Palleiko MA, Stelling JM, Philip JH. Detection of intravenous fluid extravasation using resistance measurements. J Clin Monit 1996; 12:325-330 ABSTRACT, Resistance to fluid infusion can be derived from measurements of pressure at two or more flow rates. We measured resistance in 31 patients using a pressure-monitoring infusion pump (Model 560, IVAC) by recording pressure at five flow rates (0, 50, 100, 200, and 300 mL/hr), and computing resistance as the slope of the pressure versus flow curve. Resistance was measured subcutaneously (Rtissue) and intra- venously (Rvein) immediately after unsuccessful or successful IV catheter placement. In all patients, Rtissue was always greater than Rvein. The difference ranged from 23 resistance units (RU) to 4166 ILU, with a mean difference of 1147 RU (p < 0.0001, Student's t-test). Unpaired analysis of the da~a was performed to assess the ability of resistance to indicate extra- vasation in the absence of prior lKvcin measurement. The median value for iKveinwas 62 1LU (range --13.6 to 420 1KU), and for Rti ..... 544 1KU (range 65.7 to 4170 RU). Receiver operating characteristic (ROC) analysis revealed that a 200- 1KU threshold detected infiltration with 0.90 sensitivity and 0.91 specificity. We conclude that elevated resistance during fluid infusion is an important early and easily measurable finding in fluid extravasation. KEYWORDS. Veins, Veins: catheterization, Fluid therapy, Intra- venous infusions, Indwelling catheters. Infiltration, Extravasa- tion of intravenous fluids. INTRODUCTION From the Bioengineering Laboratory, Department of Anesthesia, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, 1Department of Biostatistics, Harvard School of Public Health. Received Sept 1, 1990, and in revised form Mar 3, 1996. Accepted in final form Mar 12, 1996. Address correspondence and reprint requests to Dr. J. Philip, Depart- ment of Anesthesia, Brigham & Women's Hospital, 75 Francis St, Boston, MA 02115, U.S.A. Journal ofClinical Monitoring 12: 325-330, 1996. © 1996 KluwerAcademic Publishers. Printed in the Netherlands. The insertion of intravenous (IV) catheters and infusion of fluid are common and essential procedures in the care of patients. Complications of IV therapy include phlebi- tis, infusion-related septicemia, and extravasation of fluid and drugs [1-3]. Extravasation of antineoplastic agents, phenytoin sodium (Dilantin), and potassium can result in extensive soft tissue injury [4, 5]. Currently, monitor- ing of peripheral IV infusions to avoid these complica- tions is usually limited to intermittent physical examina- tion of the venous access site [2, 3, 5]. Fluid infusion into peripheral veins can be studied with a commercially available infusion pump (Model 560, IVAC). This device measures pressure in the fluid delivery system at flow rates of 0 to 999 mL/hr. Prior work has shown that pressure-flow relationships (PFIL) in normal veins follow a linear model (up to flows of 300 mL/hr), with the slope of the PFtL defined as resistance [6-8]. Preliminary work suggested that resist- ance to flow is different when a catheter is in tissue (P'-ti .... ) compared with in a vein (Rvein) [9]. We now report paired resistance measurements in 31 patients with witnessed catheter infiltration on initial catheter place-