1. Capacitance Ground of Patient Plate / Type BF or Body Floating
2. Floating Patient Plate / Type CF or Cardiac Floating
The advantage of BF Type is that the feed line from Patient Plate to the patient is grounded at a high frequency via a capacitor and the risk of burns is reduced in BF type. But there is a small disadvantage of low‐frequency leakage current which may flow through capacitor when the circuit is incomplete i.e., when Patient Plate is connected to machine but not in contact with the patient and cutting /coagulation is attempted, there can be a small presence of HF power at the active handle end. But the power output will be really low and will not be sufficient for any effective cutting / coagulation.
If the Patient Plate is Floating type / CF type (like most US products), the low‐frequency leakage currents can be kept very easily below the limit value but in CF Type the risk of burns is increased since the line from the Patient Plate is about half the frequency voltage of the generator. CF is mainly preferred for Cardiac procedure with Pacemaker / active implants. As per Indian Electrical Standards, we operate on Electrical supply with Ground Referencing which is considered safer. Hence our surgical diathermy units like ARC are all type BF / Body Floating as it is safer for patients in Indian operating conditions. There are two types of patient plates. Our ARC & SPARK surgical diathermy units accept both Split and Single Pad Patient Plates. The internal circuitry will detect the type of patient plate connected and work automatically.
We supply reusable single type patient plates which are much costlier than disposable patient plates so as to keep the running cost of the equipment affordable for the average Indian hospital and eventually pass on the benefit to the patients. This method is safe. However, for obtaining even more higher safety and lower infection control, it’s suggested to use disposable split pad patient plates as it will ensure power output only if there is sufficient contact area with the patient. The biggest disadvantage of disposable split patient plates is that in Indian conditions, there is always a tendency of reusing the disposable patient plate which can directly lead to high frequency burns.
1.The key point in preventing accidents with the use of electrosurgery is the correct positioning of the patient on the operating table. The contact
with metal parts of the patient or the table and monitoring electrodes can concentrate the electric current or cause its leakage and result in injury.
Insulating devices in the table and in the arm/leg rests must be used to prevent current leakage through the metal areas, in addition to dry swabs
placed between the arms, torso or legs to avoid current concentration in areas with fluid accumulation.
2. Removal of metallic ornaments is mandatory, and electrodes should be placed as far as possible from the surgical site.
3.When using the monopolar scalpel in patients with prosthetic conductive joints, every effort to place the prosthesis out of the direct path of the circuit should be made. If the patient has a right hip prosthesis, for example, the return plate should be placed on the left side of the patient.
4.The warning systems should always be working. The device sound indicator volume should be kept in audible level to signal immediately when the electrosurgical unit is inadvertently activated or when it is not working properly.
5.One should also avoid placing the dispersive electrode on tattoos, many of which contain metallic dyes. The active electrode should be placed away from the site when not in use; it avoids unintended activation and injuries.
6.Active electrodes should not be used in the presence of anesthetic gases and flammable agents, such as antiseptics for skin antisepsis. This is particularly important in ENT and head and neck surgeries, due to proximity to anesthetic gases.
7. The electrosurgical unit power should be confirmed prior to activation, which should be the lower and most effective possible, in order to achieve the desired effect for cutting or coagulation. If the surgeon requests continuous increase of power, or if there is unusual response from the patient, or if there is interference with the monitoring signal during its use, it is necessary to investigate the entire circuit for failures.
8. The dispersive plate location is generally dictated by the surgical site, it should be positioned as close as possible to the operative field, preferably in a clean, dry skin, placed in a well vascularized area and with greater muscle mass.
9. Patients with pacemaker should be continuously monitored because, although modern devices are designed to be protected from the current flow, they are still subject to interference and may be damaged beyond repair or have its function altered. Additional precautions should be taken to minimize accidents, such as checking the pacemaker proper function with the cardiologist during the use of electrosurgery, having a pacemaker programming unit available to set it in asynchronous mode, having a defibrillator on hand to immediate use in case of emergencies, keeping all the electrosurgical unit cables and wires away from the pacemaker and its connections and the generator power setting as low as possible. It is also recommended that bipolar electrosurgery should be used whenever possible, but, if necessary, the use of monopolar electrosurgery must ensure that the distance between the active and dispersive electrodes is as short as possible.
This should be got done from the equipment manufacturers to ensure that the HF leakage current, LF leakage current, HF power levels and conditions of accessories are within safe limits.
Getting certificate from free-lance recalibration agencies is a risky practice, since the free lancers do not repair or recalibrate as per IEC 60601-1-2 standards. They only check the HF outputs with an HF power meter. These free lancers do not have the knowledge or necessary expertise to carry out repairs at printed circuit board level. Whereas the equipment manufacturer has all the necessary spares and years of experience in trouble shooting all the problems that are likely to occur on a product manufactured their company
Good quality patient plates supplied by surgical diathermy manufacturers shall be made of high quality flexible electrical grade silicone rubber with electro conductive chemicals impregnated into the rubber pad uniformly across the full pad area. This means that the contact resistance at any square centimeter area anywhere on the pad shall be the same as specified according to international safety standards for electro surgical units (IEC 60601-1-2)
Cheaper brands of silicone rubber patient plate may have the same size as that of the original diathermy manufacturers in appearance but the material used for molding pad may be cheap rubber resulting in non-uniform specific resistance across the pad surface. This can result in pockets of high resistance and comparatively low resistance at alternating points across the whole pad. This in turn can result in HF current tunnelling since current always has a tendency to take the path of least resistance. This in turn results in HF burns on the patient’s body where the pad is applied.
Another situation is when the connection cable of the patient plate supplied by the equipment manufacturers goes broken and is replaced with inferior quality local ones. The patient plate cable carries HF return current. Hence it is very important to use connection cable with a greater number of wire strands of higher wire gauge. Otherwise, normal wires result in higher resistance for the patient plate to the generator. This also can lead to HF burns.
The original silicone rubber patient plate supplied by the equipment manufacturers also loses its flexibility and electrically conductive properties over a period of years. This in turn also could result in higher contact resistance across the patient contact area and consequently forcing the surgeon to use a higher HF power setting for cutting and coagulation. In this case also chances for HF burn cannot be ruled out unless the customer replace the old patient plate and cable with new ones from the equipment manufacturers.
There is a possibility for HF burns occurring at another part of the patient’s body away from the site at which the patient plate is applied. The following situations can lead to such incidents.
1. Patient with metal implants from previous surgeries are prone to such burns. In this case an HF current concentration occurs in the metal implant during surgery anywhere on the patient’s body. Any exposed part of the surgical table, drip stand, leg/arm support stirrup which are metals that are practically grounded to earth accidently happens to touch the patient’s body where the implant is located, then HF burns occur externally near the implant.
The solution to overcome this problem is to properly cover any exposed part of patient with metal implants such that chances for accidental metal contacts are ruled out.
2. Fatty patient getting burns at another part of the body far away from the point at which the patient plate is applied
In a reported instance, the fatty patient was lying flat on the surgical table and the patient plate was fastened to the patient’s thigh. During surgery the surgical/ wash fluids got accumulated below the patient’s body forming a pool wetting the surgical drape. The wet drape touched the metal part of the surgical table establishing ground contact which led to the HF burns. Also, if the rubber mat laid over the table has got cracks, then the fluids find their way to the metal parts of the table and can create HF burns.
As the name itself indicate, these plates are to be used only for a single surgery. Chances for HF burns is there if these plates are reused since the adhesive and electro
Conducting chemical loses its property after a single use
Again, it is very important to source these disposable pads from equipment manufacturers or reputed accessory suppliers like 3M only. Otherwise, cheaper brands using inferior quality electro conductive jelly and adhesive with very thin connection wires could lead to patient contact resistance build up and HF burns.
As per International standards the minimum area required for adult patient plate should be in the range of 170 to 180 sq.cm. All Spark/ Arc brand surgical diathermy units are provided with 490 sq.cm silicone rubber patient plates.
