THERAPEUTIC DIRECT CURRENT Description

1. 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

2. 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 minutes • Current density is limited by the skin resistance • Prescription • current density = 0.1 to 0.5 mA/cm2, others recommend 0.1 -0.3 mA/cm2 • duration = 10 -30 min • recommended concentrations of the ions in the solution used is 1 – 2%

3. Physiological Effects / Therapeutic Uses • Direct Current • 1.1 Sensory changes • mild tingling or prickling sensation which may merge into a mild irritation or itching sensation • localized erythema (with prolonged stimulation); more marked in cathode • 1.2 Capillary Hyperemia ( not arteriolar dilatation) • 1.3 Electronus – depolarization at cathode and hyperpolarization at anode • 1.4 relief of pain • 1.5 Acceleration of healing • 1.6 Tissue destruction – at higher current densities • 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

6. Contraindications for Ion transfer • Anesthetic skin in area to be treated • Recent scars in treatment site • Metal embedded close to skin • Acute injury if active bleeding is still present • Patients with pace makers

7. Indications for DC and Iontophoresis Relief of pain Cathodal 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

8. Calcium deposits – acetic acid transfer reduces the size of Ca deposit Idiopathic hyperhidrosis - glycopyronium bromide