Keep vein open method and injector with keep vein open function

Abstract

The present invention embodies a method and an injector adapted to incorporate this method, for keeping a patient's vein open during an intravenous contrast injector procedure without injecting a saline solution from a separate syringe. The injector includes a controller having a programmable software module to allow an operator to configure the injector to push some contrast media fluid through an injection site and then retract a plunger drive ram. A syringe is adapted to allow a patient's blood pressure to move the syringe plunger back towards its starting position, thus enabling a patient's blood to pass through the injection site. Alternatively, the syringe is adapted with an elastic plunger which as it enlarges and contracts facilitating fluid communication through the injection site. Additionally, the plunger drive ram can be adapted to gradually pull as well as push the plunger, thereby causing fluid to flow across the injection site.

1 . A method of using a syringe having a plunger with an elastic head located within a barrel of the syringe, the method comprising:
 elastically expanding the head of the plunger without sliding the head within and relative to the barrel of the syringe; and   elastically contracting the head of the plunger without sliding the head within and relative to the barrel of the syringe.   
   
   
       2 . The method of  claim 1  further comprising connecting a catheter to the syringe and to a patient at an injection site. 
   
   
       3 . The method of  claim 2  wherein between about 0.1 to about 1 milliliter of fluid is pushed through the injection site. 
   
   
       4 . The method of  claim 3  wherein between about 0.1 to about 1 milliliter of fluid is allowed to flow back through the injection site during the elastically contracting. 
   
   
       5 . The method of  claim 4  wherein fluid is moved at a pressure of about 1 to 4 psi from the end of the injection site that is distal to the plunger to the end of the injection site that is proximal to the plunger. 
   
   
       6 . The method of  claim 5  wherein during the elastically expanding a seal, attached to the head of the plunger, has a frictional force against an inner wall of the syringe that is greater than a force that elastically expands the head of the plunger. 
   
   
       7 . The method of  claim 6  futher comprising elastically expanding the head of the plunger with a stretcher rod. 
   
   
       8 . A method for injecting a fluid into a patient at an injection site comprising:
 controlling a drive motor to advance and retract a plunger drive ram to;   moving the drive ram toward a plunger of a syringe;   contacting the plunger with the drive ram;   depressing the plunger with the drive ram;   transferring fluid from the syringe through the injection site in a direction that flows from the end of the injection site that is proximal to the plunger toward the end of the injection site that is distal to the plunger;   moving the drive ram away from the plunger;   separating the drive ram from contact with the plunger; and   allowing fluid to travel from the end of the injection site that is distal to the plunger to the end of the injection site that is proximal to the plunger.   
   
   
       9 . The method of  claim 8  further providing comprising connecting a catheter to the syringe and to the patient at the injection site. 
   
   
       10 . The method of  claim 9  wherein between about 0.1 to about 1 milliliter of fluid is pushed through the injection site. 
   
   
       11 . The method of  claim 10  wherein between about 0.1 to about 1 milliliter of fluid is allowed to flow back through the injection site when the drive ram moves away from the plunger. 
   
   
       12 . The method of  claim 11  wherein fluid is moved at a pressure of about 1 to 4 psi from the end of the injection site that is distal to the plunger to the end of the injection site that is proximal to the plunger. 
   
   
       13 . The method of  claim 12  further comprising controlling the advancement and retraction of the plunger drive ram with a programmable software module. 
   
   
       14 . The method of  claim 13  further comprising configuring the software module to cause the syringe to move fluid through the injection site in a direction away from the plunger and allow fluid to flow back through the injection site toward the plunger. 
   
   
       15 . A method for injecting a fluid into a patient at an injection site during an auxiliary injection cycle comprising:
 controlling a drive motor to repeatedly and cyclically move a drive ram of the injector toward the injection site and away from the injection site during an auxiliary injection cycle;   contacting a plunger positioned within a syringe with the drive ram;   moving the plunger towards the injection site with the drive ram;   pushing with the plunger between about 0.1 to about 1 milliliter of a contrast agent fluid through the injection site during the auxiliary injection cycle; and   allowing between about 0.1 to about 1 milliliter of the contrast agent and blood fluid to flow back through the injection site when the drive ram moves away from the injection site during the auxiliary injection cycle.   
   
   
       16 . The method of  claim 15  further comprising connecting a catheter to the syringe and to the patient at the injection site. 
   
   
       17 . The method of  claim 16  further comprising moving fluid at a pressure of about 1 to 4 psi from the end of the injection site that is distal to the plunger to the end of the injection site that is proximal to the plunger. 
   
   
       18 . The method of  claim 17  further comprising controlling the advancement and retraction of the plunger drive ram with a programmable software module. 
   
   
       19 . The method of  claim 18  further comprising configuring the software module to cause the syringe to move the contrast agent fluid through the injection site in a direction away from the plunger and allow the contrast agent and blood fluid to flow back through the injection site toward the plunger. 
   
   
       20 . The method of  claim 19  further comprising allowing the contrast agent and blood fluid to flow back through the injection site in a direction away from the plunger.