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A303
October 17, 2009 3:00 PM - 4:30 PM Room Room 357 |
| Safety Implications of Medication Delivery by “Wide Open” Gravity Driven Microdrip Infusion |
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Eric T. Pierce, M.D., Ph.D., Vikram Kumar, M.D., Robert A. Peterfreund, M.D., Ph.D. Anesthesia and Critical Care, Massachusetts General Hospital, Boston, Massachusetts |
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Introduction: Gravity driven microdrip infusion sets are available to continuously deliver IV medications. A roller clamp allows adjustments of the medication drip rate and dose delivery can be reliably estimated by counting drops in a time interval. With the clamp fully open, flow in the drip chamber can be a continuous fluid column rather than discrete, countable, drops. We hypothesized that in this “wide open” state, drug delivery becomes unpredictably dependent on factors extrinsic to the microdrip set. To test this hypothesis we conducted a series of experiments to characterize drug delivery under various clinically relevant conditions of “wide open” flow in a laboratory model.
Methods: A microdrip infusion with a high flow stopcock at the distal end was plugged into a bag of normal saline. IV catheters tested (gauges 22 -14) were connected to the stopcock. The fluid meniscus height in the bag was fixed (60, 80, 100, 120 cms) above the outflow point at the tip of the intravenous catheter. Fluid volume delivered in one minute was measured with a graduated cylinder or by weighing with a balance. The roller clamp on the infusion set was in fully open position for all experiments resulting in a continuous column of fluid in the drip chamber. The stopcock was used to start and stop fluid flow. Gravity driven delivery by microdrip infusion sets from 3 manufacturers was compared. To model possible resistive effects from a carrier flow, a volumetric infusion pump was used to deliver various flow rates of normal saline to the side port of the stopcock. Data is reported as the mean + SD of 4 trials for each condition. Results: The volume of fluid delivered by gravity infusion under “wide open” conditions, increased 1.6 fold going from 22 to 14 guage and 1.6 fold going from 60 to 120 cm of the fluid column height. There was a 2.9 fold delivery difference between minimum (22 g catheter, 60 cm height) and maximum (14 g catheter, 120 cm height) conditions. Delivery characteristics of the microdrip infusion sets from 3 different manufacturers were similar. Model drug delivery decreased up to 28% as the carrier flow increased. Conclusion: Under laboratory conditions designed to resemble clinical situations, gravity driven delivery of an experimental drug infusion varied with the height of the fluid path, the gauge of the outflow catheter, and the carrier flow rate. Safe medication administration depends on precise control of the dose received by the patient. Clinicians must be aware that under “wide open” flow conditions drug delivery becomes dependent on extrinsic factors and can be widely variable. References: Igarashi H, et al. Syringe pump displacement alters line internal pressure and flow. Can J Anaesth 2005 Aug-Sep; 52(7):685-691 Donald AI, et al. Effect of changes in syringe driver height on flow: a small quantitative study. Crit Care Resusc 2007 Jun; 9(2): 143-147. From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists. |