Extravasation detection electrode patch

Abstract

A medical extravasation device has an electrode patch that can attach to the skin for sensing electrical information. Tissue impedance is calculated from the electrode patch signals. The patch has elongate pick-up electrodes inboard of elongate energizing electrodes. The measuring zone determined by the elongate space between the pick-up electrodes enhances sensitivity and specificity. The presence of an extravasation is determined by interpreting the tissue impedance measurement. The method for determining the extravasation includes a first step of determining a pre-injection baseline measurement of the tissue impedance. Then, the tissue impedance is monitored during the procedure itself. A predetermined amount of change in tissue impedance is determined to indicate an extravasation.

1. An electrode patch for use in a non-invasive device for detecting extravasation that may occur when a needle with a tip is inserted into a patient in order to introduce fluid into the vascular system of a patient, comprising:
 a body of the patch adapted to be affixed to the skin of a patient,  
 an outer pair of elongated electrodes and an inner pair of elongate electrodes, the length of each of said electrodes being deployed along the body of said patch,  
 said inner pair of electrodes being spaced from one another on either side of a center line, said inner pair defining a measuring zone, said measuring zone being shaped and dimensioned to encompass a needle tip within said zone, said zone being small enough to optimize sensitivity, said inner pair being long enough to facilitate placement of the patch over a needle tip inserted into a patient,  
 each of said outer pair of electrodes being outward, relative to said center line, of a respective one of said inner electrodes,  
 energization of said outer electrodes, when said patch is affixed to the skin of a patient, providing a field which induces a signal in said inner electrodes that is a function of the impedance of the tissue in said measuring zone.  
 
     
     
       2. The patch of  claim 1  wherein each of said electrodes further includes a first portion which is relatively short as compared to said elongate portion of each electrode, said relatively short first portions of said electrodes define a coupling region which can be connected to a single clip containing electrical contacts. 
     
     
       3. The patch of  claim 1  wherein each of said elongate electrodes are substantially the same length and wherein each of said outer pair of electrodes is adjacent to and spaced from one of said inner pair of electrodes. 
     
     
       4. The patch of  claim 3  wherein each of said elongate electrodes has a total length of about 3 inches, and a width of about {fraction (3/16)}th of an inch, and wherein said inner pair of electrodes is spaced apart by about 0.75 inches and said outer pair of electrodes is spaced apart by about 1.5 inches, and where said inner pair of electrodes is centralized relative to said outer pair of electrodes. 
     
     
       5. The patch of  claim 4  wherein said body is about two inches in width and about three inches in length. 
     
     
       6. The patch of  claim 1  wherein said electrodes are silver/silver chloride strips. 
     
     
       7. A device for use with a non- invasive detection system to detect extravasation when fluid is delivered into a patient's vascular system, comprising:      a )  an outer pair of elongated electrodes and an inner pair of elongated electrodes,        b )  said inner pair of electrodes being spaced from one another on either side of a center line, said inner pair defining a measuring zone, said measuring zone being shaped and dimensioned to encompass within said zone an end of a channel inserted in the patient's vascular system for delivering fluid into the vascular system, said zone being small enough to optimize sensitivity, said inner pair being long enough to facilitate placement of the end of the channel within the measuring zone;        c )  each of said outer pair of electrodes being outward, relative to said center line, of a respective one of said inner electrodes,        d )  energization of said outer electrodes providing a field which induces a signal in said inner electrodes that is a function of the impedance of the tissue in said measuring zone.     
     
     
       8. A device for use with a non- invasive detection system to detect extravasation when fluid is delivered into a patient's vascular system, comprising:      a )  an outer pair of elongated electrodes and an inner pair of elongated electrodes,        b )  said inner pair of electrodes being spaced from one another on either side of a center line, said inner pair defining a measuring zone, said measuring zone being shaped and dimensioned to encompass within said zone an end of a channel inserted in the patient's vascular system for delivering fluid into the vascular system, said zone being sized to detect extravasation in the measuring zone and long enough to facilitate placement of the end of the channel within the measuring zone;        c )  each of said outer pair of electrodes being outward, relative to said center line, of a respective one of said inner electrodes,        d )  energization of said outer electrodes providing a field which induces a signal in said inner electrodes that is a function of the impedance of the tissue in said measuring zone.     
     
     
       9. A device for use with a non- invasive detection system to detect extravasation when fluid is delivered into a patient's vascular system; said device comprising:      a )  first and second electrodes; the electrodes being separated from each other to encompass the end of a channel inserted in the patient's vascular system for delivering fluid into the vascular system;        b )  the first and second electrodes defining a measuring zone; the measuring zone being sized to detect extravasation in the measuring zone; and        c )  third and fourth electrodes to provide an electrical field which induces a voltage signal between the first and second electrodes; said signal being a function of the impedance of the tissue in the measuring zone.     
     
     
       10. The device of claims,  7 ,  8  or  9 , wherein the electrodes are substantially the same length. 
     
     
       11. The device of  claim 10  wherein each electrode is about  3  inches in length, and about {fraction ( 3 / 16 )} th  of an inch wide. 
     
     
       12. The device of claims  7 ,  8 , or  9 , wherein the electrodes are silver/silver chloride strips. 
     
     
       13. The device of claims  7 ,  8 , or  9 , wherein each of the electrodes has a hydrogel material thereon. 
     
     
       14. The device of claims  7 ,  8 , or  9 , wherein the electrodes are substantially parallel relative to each other. 
     
     
       15. The device of claims  7 ,  8 , or  9 , wherein each of the electrodes includes a coupling region capable of being connected to a clip having electrical contacts. 
     
     
       16. The device of  claim 8 , wherein the length of the outer pair of elongated electrodes and the inner pair of elongated electrodes are deployed along a base; said base adapted to be affixed to the patient's skin. 
     
     
       17. The device of  claim 9 , wherein the first and second electrodes are positioned between the third and fourth electrodes. 
     
     
       18. The device of  claim 17 , wherein the third and fourth electrodes are substantially parallel relative to each other. 
     
     
       19. The device of  claim 9 , wherein the length of the first and second electrodes and the third and fourth electrodes are deployed along a base; said base adapted to be affixed to the patient's skin.