Direct current therapy is a form of electrotherapy used especially for circulatory disorders, neuralgia, and cancer treatment. In this therapy, excitations of muscle and nerve cells are attenuated or increased, depending on how it is performed. However, necrosis can occur as side effects if the current at the electrodes is too strong.
What is direct current therapy?
Direct current therapy is electrotherapy that uses direct current. In addition to direct current therapy, there are also various forms of therapy using alternating current. Low-, medium-, or high-frequency alternating currents are applied. The prerequisite for direct current therapy is the presence of two electrodes between which a current flows. The electrodes are each a cathode and an anode. The cathode is negatively charged. Via ion and electron transfer, electrons travel from there to the positively charged anode. A special chemical milieu is formed at each electrode, which changes the membrane potential at the nerve cells. Thus, hyperpolarization occurs at the anode and depolarization of the membrane potential occurs at the cathode.
Function, action, and targets
Direct current therapy is used, on the one hand, for analgesia (pain relief) in various diseases such as arthrosis, arthralgia, back pain, fibromyalgia, or neuralgia and, on the other hand, for the treatment of circulatory disorders. The circulatory disorders treated in this way can be both functional and organic. These include arterial occlusive disease, hematomas or ditorsions. The mechanism of action of direct current therapy is based on the different polarization at the membrane potentials of the cells. As already mentioned, hyperpolarization occurs at the anode and depolarization at the cathode. Each cell has a resting potential. During a depolarization, this potential is reduced by the influx of sodium ions into the cell interior. In contrast, hyperpolarization is characterized by an increase in the resting potential. While depolarization increases the excitability of nerve and muscle cells, hyperpolarization dampens excitability. The attenuation of excitability at the anode evokes the analgesic effect of direct current therapy. Furthermore, hyperemia (strengthening of blood flow) also takes place, which is caused by the irritation of vasomotor nerves, the release of vasoactive substances and the change in PH. The skin and skeletal muscles are affected. This process takes place at the cathode. The direct current can also transport substances. Overall, the direct current strengthens the metabolic and nutritional state, growth and regeneration of cells. The circuit of the electrodes has a great influence on the effect. Therefore, before the therapy, there must be clarity about what effect should be achieved. For this purpose, there are various methods of direct current therapy. For example, in patients with polyneuropathy or cardiac diseases, four-cell or two-cell baths are used. If functional or vegetative dysfunctions are present, the Stanger bath is used. This method is used to treat, among other things, anxiety, pain, and especially painful conditions associated with bone cancer metastases. The Stanger bath is a full bath in which the patient lies in the bathtub. The electrodes are placed outside and provide the galvanic direct current into the bathtub. Depending on the polarity, the stangerbath has a calming or stimulating effect. However, excitation is not usually transmitted to the muscles. Another application method of direct current therapy is iontophoresis. In this method, continuous or pulsed direct current is passed through defined areas of the skin. The pulsed direct current is particularly suitable for sensitive people because there are hardly any side effects. However, the continuous direct current is more effective. The mode of action of iontophoresis has not yet been fully elucidated. However, good results are achieved in hyperhidrosis (increased perspiration), foot and hand eczema triggered by hydrosis, or a tendency to Gram-negative foot infections. Overall, direct current therapy has the advantage that it can be performed very well on an outpatient basis. In the case of cancer, the formation of metastases is prevented.Besides pain relief and blood circulation promotion, wound healing also improves under this procedure.
Risks, side effects and dangers
However, there are also disadvantages of direct current therapy. It should not be used on pacemakers, sensitivity disorders, thrombosis, skin lesions, open wounds, metal implants, inflammation, and febrile processes. The use of this therapy should also be avoided in cases of pulmonary hypertension or decompensated heart failure. This is especially true for the use of a Stanger bath. Due to the influence of current, dangerous complications can occur in these pre-existing conditions. Otherwise, treatment with direct current usually has no side effects if it is performed correctly. Only in the case of treatments in the chest area, in the face or in the neck can there be slight and harmless side effects. Symptoms such as a metallic taste or eye flickering may then occur during head treatments. Sometimes colored flashes appear instead of eye flickering. Only if the colored flashes persist should the ophthalmologist be consulted to rule out possible retinal detachment. However, necrosis may occur if direct current therapy is used improperly. So-called coagulation necrosis occurs at the anode and colliquative necrosis occurs at the anode if the current intensity is too high. In coagulation necrosis, cytoplasmic proteins are denatured. In this process, the affected tissue dies. Colliquative necrosis occurring at the cathode is characterized by liquefaction of the tissue. Tissues with a high fat and low collagen content, such as the brain or pancreas, are particularly at risk of this. The different forms of necrosis are due to the different development of pH at the corresponding electrodes.
