Medical electrodes

1. A medical electrode comprising:

a substrate; and

a conductive composition on at least a portion of a surface of the substrate, the conductive composition comprising at least one hydrogel, at least one component capable of providing a patient with a sensation selected from the group consisting of warming and cooling upon contact with tissue of a patient, and an additive selected from the group consisting of centella asiatica, echinacea, ginkgo biloba , ginseng, hyssop, and combinations thereof,

wherein the warming component is selected from the group consisting of nonivamide, cinnamaldehyde, and combinations thereof, and

wherein the cooling component is selected from the group consisting of icilin, methyl lactate, and combinations thereof.

2. The medical electrode of claim 1 , wherein the hydrogel comprises a component selected from the group consisting of gelatin, polysaccharides, crosslinked acrylamide polymers, hydroxyethylmethacrylate polymers, crosslinked polyhydroxyethylacrylate, polymerized, crosslinked 2-acrylamido-2-methylpropane sulfonic acid polymers, crosslinked polyvinylpyrrolidone, polyacrylic acid, copolymers of the foregoing, one or more salts thereof, and combinations thereof.

3. The medical electrode of claim 1 , wherein the hydrogel comprises a copolymer comprising a first monomer comprising a mixture of acrylic acid and a salt thereof, present in an amount of from about 8 weight % to about 85 weight % of the hydrogel, and a second monomer of the formula CH 2 ═CHC(O)XR, in which X is O or NH and R is an unsubstituted or substituted alkyl group of from about 1 to about 5 carbon atoms present in an amount of from about 15 weight % to about 92 weight % of the hydrogel.

4. The medical electrode of claim 1 , wherein the hydrogel comprises a homogeneous mixture of water and at least one crosslinked polymer present at a concentration of from about 7 percent by weight to about 35 percent by weight of said mixture, said crosslinked polymer having a weight average molecular weight of from about 200 kD to about 5,000 kD.

5. The medical electrode of claim 4 , wherein said crosslinked polymer is present at a concentration of from about 10 percent by weight to about 25 percent by weight of the mixture.

6. The medical electrode of claim 4 , wherein said crosslinked polymer comprises poly(ethylene oxide).

7. The medical electrode of claim 4 , wherein said crosslinked polymer comprises poly(vinyl pyrrolidone) and a viscosity-enhancing hydrophilic polymer having a weight average molecular weight in excess of about 100 kD.

8. The medical electrode of claim 7 , wherein said viscosity-enhancing hydrophilic polymer is selected from the group consisting of polyacrylamide, poly(vinyl alcohol), polacrylate, poly(ethylene oxide), poly(ethylene imine), carboxymethylcellulose, methylcellulose, polyacrylamide sulfonic acid, polyacrylonitrile, agar, dextran, dextrin, carageenan, xanthan, guar, derivatives, mixtures, blends, and copolymers thereof.

9. The medical electrode of claim 8 , wherein said viscosity-enhancing hydrophilic polymer comprises poly(ethylene oxide).

10. The medical electrode of claim 8 , wherein said viscosity-enhancing hydrophilic polymer comprises a cellulose derivative.

11. The medical electrode of claim 8 , wherein said viscosity-enhancing hydrophilic polymer is present at a concentration of from about 1 to about 2 percent by weight of said mixture.

12. The medical electrode of claim 1 , wherein the hydrogel is formed of materials selected from the group consisting of gum karaya, gum acacia, locust bean gum, guar, celluloses, cellulose derivatives, and combinations thereof.

13. The medical electrode of claim 12 , wherein the hydrogel has a solids content of from about 2% to about 50% by weight of the hydrogel.

14. The medical electrode of claim 1 , wherein the warming component is present in an amount of from about 0.01% by weight to about 1% by weight of the hydrogel.

15. The medical electrode of claim 1 , wherein the cooling component is present in an amount of from about 0.01% by weight to about 20% by weight of the hydrogel.

16. The medical electrode of claim 1 , wherein the hydrogel further comprises an electrolyte present in an amount of from about 0.1% by weight to about 15% by weight of the hydrogel.

17. The medical electrode of claim 1 , wherein the hydrogel further comprises a neutralizer selected from the group consisting of ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, and combinations thereof.

18. The medical electrode of claim 1 , wherein the hydrogel further comprises a cross linking agent selected from the group consisting of N-N′-methylene bis-acrylamide, diethylene glycol diacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and combinations thereof.

19. The medical electrode of claim 1 , wherein the hydrogel further comprises a polymerization initiator selected from the group consisting of 2,2-azobisisobutyronitrile, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-l-phenylpropan-1-one, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propan-l-one, 2,2-dimethoxy-2-phenylacetophenone, benzophenone, and combinations thereof.

20. The medical electrode of claim 1 , wherein the additive is present in an amount from about 0.1% by weight to about 10% by weight of the hydrogel.