Fried-Grant Rapid Solution Administration Set With Integral Heat Exchanger

1. Field of the Invention

The present invention relates to the treatment of human subjects for hypovolemic shock by rapid infusion of physiologic solutions into the human body which have been warmed to normothermic temperature prior to their infusion into the human body.

2. Description of the Prior Art

Treatment of hypovolemic shock requires rapid volume replacement and maintenance of normothermic temperature in vital organs of the human body. In order to resuscitate a victim in hypovolemic shock, secondary to traumatic or intraoperative hemorrhage, physiologic solutions including blood products, synthetic colloids, and crystalloids must be rapidly infused into the body. These physiologic solutions are presently introduced through a multitude of venipunctures cannulated with 18-gauge or larger internal diameter catheters. The rapidly infused physiologic solutions should also be warmed to normothermic temperature in order to maintain normothermic temperature in the vital organs of the body and prevent transfusion-induced hypotermia. Present methods of fluid administration achieve infusion rates which are too slow. Present blood warming methods demonstrate an inherent resistance to infusion flow, which does not allow adequate flow rates for optional hypovolemic shock treatment.

Banked blood is stored in a refrigerated environment at a temperature of 4 degrees Centigrade. For years, banked blood has been transfused into human subjects cold as it came from the storage refrigerator. Patients who receive as little as two units of cold banked blood tend to become hypothermic. The first major organ to be exposed to the stream of cold bank blood is the heart. Heart rate, blood pressure, cardiac output, and coronary blood flow all fall progressively as body temperature drops. The heart tends to fail during cooling either suddenly because of ventricular fibrillation, or gradually because of ischemia. C. P. Boyan, "Cold or Warmed Blood for Massive Transfusions." Annals of Surgery, 160: 282-286 (1964). In a study of 154 hypovolemic shock victims, Dr. Boyan found that there was a 58 percent mortality rate among patients receiving cold infusion of resuscitation fluids. There was a 6 percent mortality rate among patients receiving normothermic massive transfusions. Id. at pp. 284-286. However, the Volume Replacement System used in that study was deficient due to its large priming volume requirement, its lack of controlled warming capability, and its less than optimal infusion delivery rate.

Fluid replacement through peripheral veins has been the standard method of volume resuscitation. Cold bank blood and blood products are infused into the patient through a "Y" type blood solution administration set. The blood solution administration set uses a 200 micron filter and PVC tubing which is 84 inches long and has a 0.06 inch internal diameter. A crystalloid solution administration set is sometimes used. It employs PVC tubing which is 93 inches long and has a 0.06 inch internal diameter. A 16-gauge vein catheter is attached to each blood or crystalloid solution administration set, and is inserted directly into the vein. Fluids are kept in storage bags which are elevated above the solution administration sets. Each solution administration set has a hollow spike connector, which is used to connect it to the storage bag. Gravity induces the fluid to flow from the storage bag through the spike connector into the solution administration sets. The solution administration sets are elevated above the patient, and gravity induces the fluid to flow through the set to the attached vein catheters. Fluid then enters the patient through the catheter into the venous access sites.

Certain disadvantages are inherent in the use of solution administration sets to infuse cold bank blood and blood products for volume resuscitation. First, it is likely that the patient will experience transfusion-induced hypothermia. Rapid body cooling during the treatment of hypovolemic shock is associated with cardiac arrest. Second, the PVC tubing used in prior fluid administration resists flow and delays delivery of fluid to central compartments. Tubing which has a 0.06 inch internal diameter, and which has a long length of 84 inches or more, cannot deliver fluids to a patient at an infusion rate needed for successful resuscitation from hypovolemic shock. The infusion rate must be approximately 1500 milliliters per minute or greater. As a result the infusion rate of replacement fluids to the patient may not approximate the rate of loss. Unless such an infusion rate is achieved, the patient cannot be resuscitated. Also, in a hypotensive, hypovolemic shock victim, peripheral veins are not always easily accessible for mutliple venipunctures. J. Scott Millikan, Thomas L. Cain, and John Hansbrough, "Rapid Volume Replacement for Hypovelomic Shock: A Comparison of Techniques and Equipment." Journal of Trauma, 24: 428- 431 (1984). This procedure requires multiple venous access sites to connect several infusion systems for adequate volume replacement. Initiating such treatment is timeconsuming, and the delay incurred contributes significantly to the mortality rate among hypovolemic shock victims. During the time taken to initiate treatment, physiologic alterations produced by massive hemorrhage progress to an irreversable state, making death inevitable.

A fluid warming coil is used in volume resuscitation. A device of this type is described and illustrated in U.S. Pat. No. 3,472,369 to Samuel J. Schuster. The fluid warming coil described in the Schuster patent consists of PVC tubing which is 34 feet long. It also has a 0.06 inch internal diameter. The device described in the Schuster patent must also be immersed in a tank of warm water for heat transfer. Cold bank blood and blood products are warmed by flowing through the plastic tubing after it has been immersed in warm water.

Certain disadvantages are inherent in the device described in the patent. First, it does not allow measurement of blood temperature. It therefore does not facilitate controlled warming of cold blood and blood products to normothermic temperature. This is critical in the prevention of hypothermia, or of hypertermia which may cause red blood cell hemolysis and platelet denaturation and can thereby cause death. Second, the coil length and internal diameter resists blood flow such that the coil cannot warm blood at maximal infusion rates of 1500 milliliters per minute or greater. Use of the coil where massive hemorrhage has occurred therefore reduces the patient's likelihood of resuscitation from hypovolemic shock.

Consequently, a need exists for improvements in the infusion of normothermic physiologic solutions into human subjects experiencing hypovolemic shock.

The present invention embodies an apparatus for rapid fluid replacement and controlled warming of physiologic solutions. It is an intravenous set which uses 0.25 inch internal diameter PVC tubing to infuse physiologic solutions into the central venous blood pathway through an attached vein catheter. The vein catheter must have an internal diameter of at least 14-gauge. The present invention embodies larger-bore PVC tubing than prior solution administration sets. It embodies a single larger-bore vein catheter than vein catheters used in prior solution administration sets. The present invention can infuse blood into a patient at the maximal rate of 1500 milliliters per minute or greater, which exceeds the flow rate of prior solution administration sets. The length of the present invention is only 70 inches, thereby facilitating the faster flow rate.

The present invention embodies an ancillary macrodrip administration set for the infusion of drugs and physiologic solutions at a rate slower than the infusion of bank blood, blood products, colloids, and crystalloids through the rapid solution administration set. No prior blood or crystalloid administration set incorporates ancillary macrodrip administration.

The present invention also incorporates a rapid fluid warmer of a type described and illustrated in U.S. Pat. No. 4,177,816 to William Torgeson. The device described in the Torgeson patent has not been previously incorporated in an apparatus for treatment of hypovelomic shock. The device described in the Torgeson patent permits rapid, c ontrolled warming of fluids. The present invention permits the measuring of fluid temperature before entering and after exiting the device described in the Torgeson patent. Accordingly, the warming of fluids by the device described in the Torgeson patent can be monitored and adjusted to maintain normothermic temperature, and prevent excessive warming.

The device described in the Torgeson patent is only 20 inches long. Its length and the size of its heating surface area is such that this device can warm blood at a flow rate of 1500 milliliters per minute or greater.

FIG. 1a is a perspective view of the upper section of the present invention.

FIG. 1b is a perspective view of the lower section of the present invention .

The drawings depicted on FIG. 1a and FIG. 1b form in effect a single complete figure. To understand the complete figure of the present invention, arrange the drawings such that the bottom of FIG. 1a is adjacent to the top of FIG. 16.

Referring now to the drawings, and more particularly to FIG. 1a, there is shown the most proximal end of the rapid solution administration set. The fluid connector spike 1 is a rigid, molded plastic spike connecting the desired infusate solution bag to a 6 inch long, 0.25 inch internal diameter PVC tube comprising a non-filtered infusion line 2. The blood transfusion filter 3 is a disposable, interchangeable, free-flow 40 micron pore size screen filter with molded plastic spike. This low priming volume filter performs microaggregate filtration. In connects the desired infusion solution bag to a 3 inch long, 0.25 inch internal diameter PVC tube, and comprises the filtered infusion line 4. Located around the filtered infusion line 2, the non-filtered line 4, and distally around 0.25 inch internal diameter PVC tubing 12 are plastic tube clamps 5. The clamps regulate gravity-induced infusate flow. When closed, the tube clamps 5 occlude the PVC tubing within each clamp and restrict the flow of infusate solution. When opened, the PVC tubing allows free flow of the infusate solution. Each tube clamp 5 functions independently, and provides selective fluid flow for specific physiologic solutions required in rapid volume replacement. When the filtered infusion line 4 and the non-filtered infusion line 2 are connected to infusate solution bags, the tube clamps 5 are closed until infusion is initated.

The filtered and non-filtered infusion lines are joined by a 0.25 inch internal diameter plastic "Y" connector 6 to form a common infusion line. The "Y" connector 6 is 0.25 inch internal diameter rigid plastic connector, which is 3 inches in length. The "Y" connector 6 is connected to a fluid shut-off valve 7. When placed with its axial centerline at or near the vertical position, the fluid shut-off valve 7 will seal and stop the flow of air at its distal outlet. When primed with fluid, the hollow ball 8 within the fluid shut-off valve 7 floats freely. The hollow ball 8 is supported by hydrostatic and hydrodynamic force during fluid flow. If air enters the fluid shut-off valve 7, the ball sinks and occludes the distal outlet, thereby terminating fluid flow. To re-open the fluid shut-off valve 7, fluid must be introduced retrograde into the valve, unseating the hollow ball 8. The present invention embodies the fluid shut-off valve 7 to prevent introduction of an air bolus into the patient.

At the distal outlet of the fluid shut-off valve 7, a 1.5 inch length of 0.25 inch internal diameter PVC tubing 9 connects to a 170 micron pore size filtered drip chamber 10. The 170 micron pore size filtered drip chamber 10 is a pliable plastic reservoir containing a 170 micron mesh filter 11 within. It functions as a gross microaggregate filter, and as a means of facilitating retrograde flow to reprime the fluid shut-off valve 7. After changing the emptied infusate bag and clamping the PVC tubing 12 on the distal outlet of the filtered drip chamber 10, squeeze the filtered drip chamber 10. Fluid will be displaced out of the proximal inlet of the filtered drip chamber 10, causing retrograde filling of the fluid shutoff valve 7.

The proximal inlet cap of the filtered drip chamber 10 is attached to an ancillary macrodrip administration set through a 0.06 inch internal diameter ancillary infusion line 13. It provides a means for drug introduction at slower drip rates into the present invention. The ancillary infusion line 13 is 8 inches long. Attached to the proximal end of the ancillary infusion line 13 is a three-way plastic stopcock 14. The stopcock 14 is attached to a latex connector 15. The present invention embodies a latex connector 15 to allow insertion of more intravenous sets and syringes at that point. The latex material has the ability to seal around inserted needles and exclude the entry of air from insertion points. The proximal inlet of the latex connector 15 is attached by a 0.06 inch internal diameter PVC tube 16, which tube is 12 inches long, to the distal outlet of non-filtered drip chamber 17. Attached to the proximal inlet of the non-filtered drip chamber 17 is a fluid spike connector 18. The fluid spike connector 18 is used to conect an infusate solution bag to the non-filtered drip chamber 17. Located around the 0.06 inch internal diameter PVC tube 16 is a flow control clamp 19. The flow control clamp 19 is used to restrict or allow passage of fluid from the distal outlet of the non-filtered drip chamber 17. When the fluid spike connector 18 is connected to the infusate solution bag, flow control clamp 19 is closed until slow fluid maintenance is initiated.

The 0.25 inch internal diameter PVC tubing 12 is 4 inches long, and is connected to the proximal end of a 0.25 inch internal diameter inlet temperature probe connector 20. The inlet temperature probe connector 20 is constructed of a biocompatible metal tube and plastic infusate inlet and outlet ports. It allows non-invasive pre-warmed temperature measurement of the flowing physiologic solutions within, when coupled with a standard temperature probe and monitor. The distal end of the inlet temperature probe connector 19 is attached to the 0.25 inch internal diameter PVC tubing 21. Said tubing is 4 inches long.

Referring to FIG. 1b, the 0.375 inch internal diameter PVC tubing 21 connects to the proximal infusate inlet of an extracorporeal heat exchanger 22. The extracorporeal heat exchanger 22 is of a type described and illustrated in U.S. Pat. No. 4,177,186 to William Torgeson. It consists of 19 thin-walled, biocompatibly-coated aluminum tubes. Each tube contains biocompatibly coated aluminum rod inserts shaped in a staircase pattern to promote gentle mixing of infusate solution flowing through the rods, and to conduct active heat transfer from separated counter-current water flow about the exterior of the aluminum tubes. The aluminum tubes are encased in a hard plastic shell. Heated water is actively pumped into the plastic shell through the distal connecting port 23, and runs counter-current with the infusate flow. The heated water exits from the proximal water port 24. Water flow cannot exceed 42 degrees Centigrade or 65 pounds per square inch water pressure. The infusate phase pressure limit is 1000 millimeters of mercury. The infusate phase of the heat exchanger unit 22 will initially be primed retrograde in series with the other components of the present invention. The priming solution must be biocompatible.

Attached to the distal infusate outlet of the extracorporeal heat exchanger 22 is the outlet temperature probe connector 25. The outlet temperature probe connector 24 is constructed of a biocompatible metal tube and plastic infusate inlet and outlet ports. It allows non-invasive post-warmed temperature measurement of flowing physiologic solutions exiting the extracorporeal heat exchanger 22, when coupled with a standard temperature probe and monitor.

The distal outlet of the outlet temperature probe connector 25 is attached to a 0.25 inch internal diameter PVC tube 26, which is 6 inches in length. The 0.25 inch internal diameter PVC tube is attached to the proximal inlet of a 170 micron pore size filtered drip chamber 27. The filtered drip chamber 27 is a pliable plastic reservoir containing a 170 micron mesh filter 28 within. It possesses no ancillary infusion line. It functions as a final gross microaggregate filter. The distal outlet of the filtered drip chamber 27 is attached to 0.25 inch internal diameter PVC tubing 29 which tubing is 18 inches in length. The 0.25 inch internal diameter PVC tubing 29 is attached to a rigid plastic male perfusion adaptor tip 30. The male perfusion adaptor tip 30 has a 0.25 inch internal diameter, and attaches to the female recepticle of a vein catheter 31. The vein catheter 31 has an internal diameter of at least 14-gauge. The vein catheter 31 is used to penetrate the venous access site.

Before the vein catheter 31 is connected, a temporary spike connector 32 is attached to the male adaptor tip 30. The temporary spike connector 32 connects the present invention to a priming solution bag. After the temporary spike connector 32 is connected to the priming solution bag, retrograde priming of the present invention is performed by inverting the apparatus using aseptic technique. When retrograde priming is accomplished, the temporary spike connector 32 is disconnected from the male perfusion adaptor tip 30 and discarded. The vein catheter 31 is then connected to the male perfusion adaptor tip 30, and the present invention ready for use. The vein catheter 31 should be inserted into the patient's central venous blood pathway. The tube clamps 5 and the flow control clamp 19 are then selectively opened allowing the flow of physiologic solutions to the patient.