THERAPEUTIC DIRECT CURRENT

Description refers to a current that passes for more than 1sec continuously in one direction (unidirectional current) also called: constant current or galvanism or galvanic current available units: medium frequency DC type current with pulse type duration of 125 microsec and intervals of 5 microsec giving a duty cycle of 96%

Transmission current is transmitted to the site of stimulation through a metal electrode (conductor) that has a wet pad at the end the effect is a chemical change at the electrode-tissue junction (changes of electrolysis) the nature of the change depends on the available electrolytes at this junction in general, acids form at the (+) electrode (anode), while bases form at the negative electrode (cathode) follows Ohm’s law: current in any circuit is directly proportional to the Voltage and inversely to the resistance; thus, the intensity to be used also depends on the resistance encountered resistance here is from the epidermis----- the larger the cross- sectional area the lesser the resistance

Others chemical burns are more likely to occur at the cathode the extent of the chemical change depends on the

1. current intensity per unit area (mA/cm2) or current density

2. duration of time that the current is flowing

Iontophoresis

-The transfer of the ions of drugs into the body through the skin by the use of constant DC-A drug in ionic form is applied at the end of electrode which will move to either the cathode or anode depending on whether it is an acid or base; the drug can therefore be introduced into the tissue- the amount of drug introduced depends on the current density and duration of treatment

thus, dosage is expressed in terms of total current in mA multiplied by time in minutesCurrent density is limited by the skin resistance

Prescriptioncurrent density = 0.1 to 0.5 mA/cm2, others recommend 0.1 -0.3

mA/cm2duration = 10 -30 minrecommended concentrations of the ions in the solution used is 1 –

2%

Physiological Effects / Therapeutic Uses

1.Direct Current

1.1 Sensory changesmild tingling or prickling sensation which may merge into a

mild irritation or itching sensationlocalized erythema (with prolonged stimulation); more marked

in cathode1.2 Capillary Hyperemia ( not arteriolar dilatation)1.3 Electronus – depolarization at cathode and hyperpolarization at anode1.4 relief of pain 1.5 Acceleration of healing1.6 Tissue destruction – at higher current densities

2.Iontophoresis

2.1 local anesthesia 2.2 relief of idiopathic hyperhydrosis (most common)2.3 application of drugs such as antibiotic and anti-inflammatory drugs; use of vinca alkaloids has been used to relieve neurogenic pain

Condition Ion used Physiological Effect Dosage

Athlete’s foot

Cu (+) fungicide 1% copper sulfate solution10 mA for 15 mins 2x a wk

Rhinitis Zinc (+) Coagulation of mucus membrane

2% of zinc sulfate jelly3mA x 3mins to 8mA to 8mins

Decubitus Ulcer

Zinc (+) bactericidal 1-2% zinc sulfate sol or 2% gel25-100mA/min wkly for 2-3wks

Post-traumatic edema

Hyaluronase

Breaks down hyaluronic acid

150 units of hyaluronidase in 250ml of a buffer solution of1.Na acetate 3H2O: 11.42g2.Glacial acetic acid: 0.923ml3.Distilled h2O,quantum satis (qs) 1000ml

Plantar warts

Salicylate (-)

Removal and relief of pain

2% aquaeous solution10mA-mins once a wk for 2-3 treatments

Trigger points

Novocaine or lidocaine

Local anesthesia 1% solution in 60-80% alcohol w/ 1:20,000 adrenalin20-30mA for 20-30mins up to 3x/day

Condition Ion used Physiological effect

dosage

Acute RA Cvitrate (-) Prevents allergic response

1% potassium citrate in distilled water7.5-10mA for 20mis daily to 3x/week

Acute and subacute inflammation

Dexamethasone (+) with lidocaine HCL

Anti-inflamm 4mg dexa Na phospahate in mL sterile water with 2m of 4% lidocaine Hydrochloride4-5mA for 15-20mins

Peripheral circulatory deficit

histamine vasodilator 1-10,000 hitsamine diphosphate3-12 mA for 5-20 mins (60mA-min) 2-3x/week

Gout Lithium (+) Competes with Na information of urate, lithium urate is soluble

2% lithium Cl 5 mA for 20mins once a week for 4 weeks

Contraindications for Ion transfer

1.Anesthetic skin in area to be treated2.Recent scars in treatment site3.Metal embedded close to skin4.Acute injury if active bleeding is still present5.Patients with pace makers

Indications for DC and Iontophoresis

Relief of painCathodal Galvanism – for chronic pain caused by adhesions,

swelling or pressure on nerves- counter irritant effect – on the large sensory fibers and inhibit

the pain at spinal level through the presynaptic inhibitory mechanism. Useful for pain caused by ischemia such as in vascular or sympathetic d/o eg., painful amputation stumps, SH syndromes and Sudek’s atrophy. A maximum dosage must be given to achieve desired effect

Cathodal Galvanism – relieves Pain by removing the increased concentration of H+ and K+ ions w/c accumulates in ischemia and inflammation

- H+ ions are repelled by (+) pole of the anode- low dosage for a maximum length of time is given

Adhesions – use of renotin triple response of histamine – inc heat, marked vasodilation,

and a wheal

Chronic congestion of mucous membrane – transfer of zinc sulfate into congested nasal membranes

Calcium deposits – acetic acid transfer reduces the size of Ca depositIdiopathic hyperhidrosis - glycopyronium bromide