Intravenous fluid warming device

[0001] This application claims priority to U.S. Provisional Application No. 60/348,571, filed Jan. 15, 2002.

[0002] The inventions described below relate the field of devices that warm fluids delivered to patients.

[0003] Hypothermia, which comprises a body temperature of 95° F. or below, is a serious condition for which all trauma patients are at risk. Due to the use of anesthetics and the administration of cold intravenous fluids, 65% of all surgical patients experience hypothermia. Hypothermia causes discomfort and can cause potentially life-threatening complications, such as ventricular fibrillation, especially during surgery.

[0004] In an operating room setting, fluid may be provided to a trauma patent at flow rates varying from 20 ml per minute to 1 liter per minute. Fluid to be provided intravenously flows through a plastic tube extending from a fluid reservoir (such an intravenous bag) to a vein within the patient. The intravenous bag is typically stored or held in the operating room, and when administered to the patient, it is administered through a tube which may be 6 to 8 feet long. Operating rooms are usually maintained at about 55° F. to about 65° F. degrees, and, consequently, any fluid in the intravenous bag is often cooled to the ambient temperature which is well below body temperature. Infusing this cold fluid intravenously into the already stressed surgical patient can significantly affect the patient's body temperature and greatly increase the chances that the patient will experience hypothermia and other serious complications.

[0005] Hypothermia and other deleterious effects of cold IV fluids can be avoided by heating the IV fluid. However, even with the current, overwhelming evidence of the clinical benefits of fluid warming (which includes avoidance of hypothermia, discomfort, shivering, and reduced infection rates, faster healing, shortened hospital stays, and reduced risk of serious heart injury), only about 4% of the 45 million U.S. hospital infusions were warmed during the year 2000. Almost none of the 4 million emergency infusions were warmed. Thus, a simple, cost effective device is needed to warm fluids provided intravenously to patients.

[0006] Heating may be accomplished prior to use, but this may be impractical in an emergency settings or field applications. Thus, heating may be advantageously accomplished during the administration of the intravenous fluid, through heat exchange between the intravenous fluid and a heat source placed in the intravenous flow path. Several devices have been proposed for use in warming intravenous fluid. Kistner, Intravenous Warming System, U.S. Pat. No. 6,139,528 (Oct. 31, 200) discloses an electrical heating system, where intravenous fluid passes through a heat exchanger and is heated by electrical heating elements. White, Apparatus and Method for Warming Intravenous Equipment, U.S. Pat. No. 4,934,336 (Jun. 19, 1990) discloses a system in which flexible containers holding crystalizable supercooled aqueous salt solution are packed around an IV bag and the proximal extent of the IV tube.

[0007] The devices and methods described below provide for a means for warming fluids provided intravenously to patients. A warming pouch is disposed around an IV tube, at its distal extent, within several inches of the distal tip of the catheter (that part which is inserted into a vein of the patient) and the percutaneous entry point. Where a drip chamber is used, the warming pouch is disposed on the IV tube between the entry point and the drip chamber.

[0008] In one embodiment, the system is assembled just prior to use by removing the warming pouch from the airtight package, applying a slightly oversized adhesive sheet to one side of the pouch, and then folding the pouch over the IV tube and securing the pouch around the tube with that portion of the adhesive sheet that extends over the margins of the pouch. In another embodiment, the pouch is manufactured with an adhesive surface, and is stored with a peel-away sheet protecting the adhesive. To use the warming pouch of this embodiment, the warming pouch is removed from its airtight package, the protective sheet is peeled away, and the adhesive side of the pouch is folded over the IV tube and folded against itself to secure the pouch onto the IV tube.

[0014] FIG. 1 shows the intravenous warming and infusion system installed on a patient 1. The system comprises an intravenous catheter or IV tube 2 and a heating assembly 3 wrapped around the tube. The fluid is stored in an intravenous bag 4 and the bag is in fluid communication with the tube through a drip chamber 5 and a roller clamp 6 which is used to control the infusion rate. The tube is secured to the patient with tape 7 and the tube is in fluid communication with the vein either directly or through a hollow needle connected to the tube, with the distal tip of the tube or the needle disposed within the vein. A fixation assembly 8 may also be provided to inhibit twisting of the IV tube near the percutaneous entry point.

[0015] The heating assembly comprises an adhesive sheet 9 disposed around a warming pouch or pad 10. In the assembled form, the adhesive sheet forms an outer covering, and the pouch forms an inner covering, for a warming medium. The warming pouch contains an exothermic composition capable of producing an exothermic reaction and thus producing heat. Most conveniently, the warming pouch comprises an air-permeable pouch filled with an “exothermic composition” comprising an aggregate of materials that react with oxygen in the air to produce heat. The common iron powder, cellulose (sawdust), vermiculite, and salt aggregate used in recreational pocket warmers is suitable. When exposed to the air the ingredients combine to induce a rapid oxidation of the iron powder which produces heat. The amount of heat produced, the temperature achieved and the longevity of the warming pouch can be controlled by adjusting the formulation of the aggregate. Typically, pouches may produce significant heat for hours. The warming pouch is stored in an airtight package for storage, and is removed from the airtight package immediately prior to use.

[0016] The heating assembly 3 is folded around the tube 2 and secured in a longitudinal region of the tube which is about 1 to 6 inches proximal to the point where the tube (or a hollow needle in fluid communication with the tube) enters the patient's vein or from the distal end of the IV tube. Thus, only about 1 to 6 inches of IV tube remains exposes distal to the heating assembly.

[0017] FIG. 2 shows the outer covering or adhesive-sheet 9. The adhesive sheet may comprise different flexible materials that are air-permeable and suitable for securing the a warming pouch, such as polypropylene fabric, cotton, and many other fabrics. The adhesive sheet may be provided in different sizes and shapes to accommodate different sizes and shapes of warming pouches. For example, an adhesive sheet of about 3 by 5 inches (7.5 to 12.5 cm) would be suitable for a warming pouch of about 2 by 5 inches (5 by 12.5 cm), as illustrated below. One side of the adhesive sheet is provided with an adhesive 15. The adhesive may be covered with a paper overlay or a release paper 16, which is peeled off at the time of use.

[0018] FIG. 3 shows the warming pouch 10 which serves as an inner container for the exothermic composition for use in the intravenous fluid warming and infusion system shown in FIG. 1. The warming pouch is stored in an airtight package 17. In use, the warming pouch 10 removed from the package and exposed to air. The inner container may measure about 2 by 5 inches (5 by 12.5 cm), may be about ¼ inch (roughly 0.5 cm) thick, for use with the adhesive sheet described above. The inner container may comprise other flexible materials that are ventilated or air-permeable.

[0019] The exothermic composition may comprise iron powder, cellulose, activated carbon, vermiculite and salt, though the exothermic composition may comprise other combinations of chemicals or substances that produce heat when exposed to air. The composition may also comprise a metal powder, a salt and water. The composition may also comprise an alkaline earth metal oxide, water and a salt. The exothermic composition may have different proportions of ingredients to alter the amount of heat produced.

[0020] During manufacturing, the specified ingredients are mixed together and sealed in the inner container. The inner container is then stored in the airtight package, which is sealed to prevent oxygen from reaching the inner container. Just prior to use the airtight package is unsealed and the inner container is exposed to air. The iron dust among the ingredients then oxidizes and generates heat. The amount of heat generated is controlled by the amount of iron powder and other compounds in the exothermic composition, by the permeability of the inner container and by the dimensions of the inner container. The temperature of the warming pouch will be from about 100° F. to about 140° F. during the chemical reaction. When the inner container is wrapped around the tube, the heat will substantially warm the fluid passing through the tube. Warming to a temperature of about 90° F. to 95° F. or higher may be accomplished. The warmer fluid prevents the patient from experiencing hypothermia. The warming device will maintain its maximum temperature for about 3 to about 8 hours, depending on the exothermic composition and the length of the warming device. The shelf life of the exothermic composition within inner container is 3 about years.

[0021] FIG. 4 shows the warming pouch 10 disposed on the adhesive sheet 9. To assemble the heating assembly 3 the warming pouch is removed from the airtight package. The release paper 16 on the adhesive sheet is also removed. The warming pouch is then placed on the adhesive-surface of the adhesive sheet to form the heating assembly 3. The warming pouch may be placed on the adhesive sheet such that a strip of adhesive remains exposed on either side of the warming pouch. In one embodiment a first strip 18 of adhesive is about ½ inch (1.25 cm) wide and a second strip 19 of adhesive is also about ½ inch (1.25 cm) wide. The heating assembly is then-folded around the intravenous tube with the inner container facing the tube. The first adhesive strip 18 may be affixed to the second adhesive strip 19 as the assembly is wrapped around the tube 2, thus securing the assembly around the tube. The heating assembly may be assembled immediately prior to use, or it may be manufactured as shown and provided to end-users in the assembled configuration, with appropriate release paper covering the adhesive borders and appropriate airtight packaging protecting the warming pouch from exposure to air. The heating assembly and IV tube can also be provided to end users in a prefabricated assembly including the IV tube and the warming assembly.

[0022] FIG. 5 shows an embodiment of the intravenous fluid warming and infusion system. In this embodiment the warming pouch is removed from the airtight package and is wrapped around the tube 2 without using a separate adhesive sheet. A portion of the outer surface of the warming pouch 10 is provided with an adhesive surface 15. A release paper, which is removed just prior to use, may be disposed on the adhesive surface. The warming pouch is secured to the tube by affixing the adhesive to the tube and by affixing the inner container to itself while being wrapped around the tube.

[0023] The warming device is employed when a patient is provided with intravenous fluids. The user removes the release paper from the adhesive sheet and also removes the warming pouch from the airtight package. The user places the warming pouch on the air-permeable adhesive sheet such that a strip of adhesive is exposed to either side of the warming pouch. Thus, the assembly is provided with a first strip of adhesive opposite a second strip of adhesive. The assembly is then wrapped around the tube with the warming pouch facing the tube, thereby heating any fluid disposed inside the tube. The assembly is secured to the tube by affixing the first adhesive strip to the second adhesive strip. The heating assembly may be disposed about 1 inch to about 2 inches (2.5 to 5 cm) proximally from the percutaneous point of insertion of the tube or needle to reduce heating losses. However, the assembly may be placed anywhere along the tube, in particular, it may be placed between the drip chamber and the roller clamp. After use, the warming assembly is disposed along with the IV tube.

[0024] In addition to providing comfort and therapeutic advantages, the warming device is small and light weight, being fractions of an ounce, and is thus easily transported. The warming device is readily useable under adverse conditions, such as emergency medical situations, and by emergency medical personnel. Indeed, the warming device can be applied in seconds anywhere an intravenous infusion is administered. The warming device is also compatible with any dialysis tubing used for dialysis or intravenous injections. The cost is nominal, being comparable to large surgical dressings.

[0025] Other types of flexible heating pouches, containers or pads may be used. For example, a warming pouch may hold an exothermic composition that produces a reaction when sufficiently agitated that produces heat. For example, a composition of iron, cupric carbonate, water soluble metal halide salt, citric acid and alkali metal chlorate may be mixed and agitated to produce heat. In use, the pouch is agitated to start the chemical reaction and is then wrapped and secured around the fluid delivery tube. In another embodiment, a warming pouch may hold a super-chilled liquid, such as sodium acetate, that warms to its freezing point when activated or agitated. (Such a pad is re-useable.) In use, the liquid is agitated to initiate a chain reaction of crystal growth that produces heat as the liquid changes to a solid. The pouch is then wrapped around the fluid delivery tube. In yet other embodiments, the warming pouch may hold a substance that retains heat well, such as water, flax seed or other substances. In use, the container is warmed and then wrapped and secured around the tube to warm the fluid in the tube. In any of these embodiments the warming pouch may be provided with one or more adhesive strips so that the pouch may be secured around the fluid delivery tube. Similarly, an adhesive sheet may be provided and the warming pouch disposed on the adhesive sheet to form a heating assembly.

[0026] In addition, multiple heating pouches may be placed along the IV tube, or on the IV bag or other fluid source, to provide extra heat. Thus, while the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the inventions. Other embodiments and configurations may be devised without departing from the spirit of the inventions and the scope of the appended claims.