Diathermy in perioperative practice.
Diathermy has revolutionised modern surgery and is an important
tool for efficient and safe surgical practice. It has evolved to become
the modern day scalpel, being used for cutting and coagulating tissues.
This article addresses the functioning and safe use of diathermy in the
perioperative setting. The various precautionary checks before surgery,
which are prerequisite for safe usage, are highlighted along with the
necessary safety drills during and after operation. A specific note is
included about the use of electrical equipment in specialised surgeries
like cardiac and laparoscopic surgery. The issues regarding the
maintenance and repair of equipment are acknowledged and finally, the
anticipation for a future with precise and safer cutting and coagulation
devices is addressed.
KEYWORDS Diathermy / Safety / Electrodes / Laparoscopic surgery
Perioperative care (Management)
Laparoscopic surgery (Methods)
Potty, Anish G.
Tailor, Hitesh D.
|Publication:||Name: Journal of Perioperative Practice Publisher: Association for Perioperative Practice Audience: Academic Format: Magazine/Journal Subject: Health; Health care industry Copyright: COPYRIGHT 2010 Association for Perioperative Practice ISSN: 1750-4589|
|Issue:||Date: Nov, 2010 Source Volume: 20 Source Issue: 11|
|Topic:||Event Code: 200 Management dynamics Computer Subject: Company business management|
|Geographic:||Geographic Scope: United Kingdom Geographic Code: 4EUUK United Kingdom|
Existence of electrodes for medical uses, such as removing skin
lesions, dates back over 100 years (Riviere 1900). Over the century, its
use has evolved and diathermy electrical devices are now a valuable tool
in modern surgery to facilitate the cutting of tissues and to prevent
bleeding from small vessels during operative procedures (Kirk 2010,
Meeker & Rothrock 1999). It is therefore important to understand how
diathermy works, and the principles and precautions involved with its
safe use in the perioperative setting.
Technical concepts of diathermy devices
Diathermy electrosurgical devices work by converting electrical current to a high frequency alternating current (HFAC). The current used is in the range of 200kHz to 3MHz, which is much higher than the frequency that would cause neuromuscular stimulation or electrocution (Covidien 2009). Electrical currents passing through diathermy circuits generate localised heat due to the resistance of the tissues to the flow of current. In addition to other variables, altering the frequency waveform can cause three different effects on tissues resulting from a rise in temperature. It can cut the tissue by generating heat and destroying cells, it can coagulate vessels by contracting the tissues, and it can fulgurate or dehydrate cells (Covidien 2008, Phippen & Wells 1999). There are two different types of diathermy devices which are commonly used depending on how the electrical circuit is completed: monopolar and bipolar.
In monopolar diathermy, HFAC is generated in the electrosurgical device and is emitted via an active electrode controlled by the operator. The active electrode is commonly in the form of a diathermy pen, with various tips, such as balls and spatulas, available for the desired procedure. Forceps may also be used where the surgeon requires grasping in haemostasis. It can be operated using either finger switches at the active electrode site or remotely with two pedals attached to the diathermy machine. The blue finger switch or pedal activates coagulating and the yellow switch or pedal activates cutting.
Monopolar diathermy is often used for haemostasis at the surgical wound site. However, its potential as a dissecting tool is under-appreciated, and is facilitated by the use of the foot control and the round-tipped spatula end (Beasley 2008). The current passes through the patient's body tissues and then returns back to the diathermy machine via a dispersive electrode or patient return pad. Hence, the patient is an important part of the circuit. The large area of the patient return pad results in a lower current density than that of the active electrode (Hay 2007); the significance of this is explained later.
In contrast to monopolar diathermy, forceps are more frequently used in biopolar diathermy. HFAC generated by the diathermy electrosurgical device passes down one tine of the forceps and then through the patient's tissue placed between the tips before returning to the diathermy machine through the second tine (Hay 2007). A common use for bipolar diathermy is to secure haemostasis in peripheral tissues. Cutting is also possible with the use of bipolar scissors and graspers (Jones et al 2006) .
Maintenance and general considerations
Maintenance checks should be done annually by a qualified and experienced engineer. Checks are usually done by the biomedical engineering department who can then mark the equipment as safe for use (AORN 2005). There should be labels on all electrical equipment with clear documentation of safety testing. The date of testing, the due date for the next test, the testing authority seal and tester's signature should be checked before use. All faulty equipment should be taken off the theatre premises and repaired before further use (Wicker & O'Neill 2010). In addition, manufacturers should be updated regarding faults and performance of the equipment.
Only manufacturer recommended and quality assured electrical equipment should be used. Diathermy should only be set up by an experienced and competent practitioner who has had prior training with the equipment and equipment must be used according to the manufacturer's guidelines. All the necessary safety precautions and checks should be carefully followed as advised in the instruction manual. The equipment should be inspected and safety features tested before every use (AfPP 2007) . The volume of the activation sound indicator should be turned on and tested so that any malfunctioning can be heard when the device is switched on. Failure to pass the necessary preoperative safety tests should be taken seriously and reported to the hospital biomedical engineering department immediately for repairs or replacements (Wicker & O'Neill 2010).
If the operator reports any inaccuracies or any malfunctioning during the procedure, unscrubbed theatre staff should check the entire electrosurgical circuit to rectify the problem and, if necessary, reset the unit. If sterility is an issue, the active electrode should be disconnected from the main unit with the lead, and the whole system should be replaced with a new sterile set. Capacitive coupling occurs when alternating current is transferred from an insulated instrument to a non-insulated instrument through a capacitor. Therefore, intraoperatively, care should be taken to keep non-insulated metal objects at a safe distance from an activated electrode to avoid short-circuit. This can cause a spark and result in serious injuries in theatres (Hay 2007). Capacitance in relation to the cables and laparoscopic procedures is discussed later.
Any injury or burns to patient or staff, and any equipment failure with the active or dispersive electrode must be managed according to the recommendations of the Safe Medical Devices Act (FDA 2000). An incident form should be completed and evidence of injury should be documented in the patient's notes. The device identification, maintenance and service information and the adverse event information should be included in the report (AORN 2005).
Components of the diathermy set-up
The typical diathermy set-up consists of the diathermy generator unit, cables and electrodes (Covidien 2008). Each of these components is discussed below.
The unit should be placed on a stand with wheels so that it can be moved easily around the theatre without any problems. It should be kept as far as possible from highly inflammable liquids and gases. Fluids, especially alcoholic preparation, should never be placed on top of the diathermy unit as these units pose a potential fire hazard (Beesley & Taylor 2006).
Power settings should be adjusted in conjunction with the manufacturer's guidelines, type of surgery, patient's weight and body surface area. The diathermy should be set to the lowest effective energy setting for desired cutting and coagulation to reduce the potential of burns and injuries (AORN 2005). Power setting should be confirmed verbally.
Cables and electrodes
All cables and electrodes must be checked prior to use to ensure that insulation is intact. All knots and twists in the electrode cable must be removed before plugging in the electrode. The electrode cable should not be wrapped around metal objects as metal is a conductor of electricity and may cause burns (AfPP 2007, AORN 2005, Covidien 2008). All cables should be completely insulated, of adequate length and without any stress. Active electrodes should be within easy reach of surgeons and secured to drapes with non-metal clips to maintain sterility. When not in use the active electrode should be placed in a clean well-insulated holster to prevent burns to the patients and drapes (AfPP 2007, Wicker & O'Neill 2010). The build up of eschar on the electrode tips is a potential fire hazard (Covidien 2008). Therefore, a scratch card should be used to clean off any eschar to ensure efficiency and safety of the electrode (AORN 2005). Availability of specially-coated tips are said to reduce the build-up of eschar (Covidien 2008). It is the responsibility of the operating surgeon to activate the electrode (AORN 2005). After all the necessary checks and final count, the disposable active electrode tip should be discarded into a sharps bin.
If two or more electrical units are used concurrently during an operation, the manufacturer's instructions for compatibility of differing equipment must be adhered to. If this is not followed, there is a risk of short circuits and burns to the staff and the patient (AORN 2005).
Surgical plume, the large amount of smoke generated when diathermy is used on tissue, should be constantly sucked off to prevent inhalation of toxic chemical byproducts like toluene, formaldehyde, benzene and hydrogen cyanide (Ulmer 2008). These plumes also contain intact cells, cell parts, intact viral DNA, viable bacteria, including mycobacterium tuberculosis (Woodhead & Wicker 2005). Further protection is achieved through the specially designed smoke evacuation systems and surgical filtration masks which are donned for all surgical procedures (AORN 2005, NATN 2004).
An important aspect of effective diathermy functioning is the proper placement and sizing of the dispersive electrode when using the monopolar setup. An appropriate size dispersive electrode must be chosen, based on the patient's weight. After safely positioning the patient on the operating table, the dispersive electrode should be placed on a dry intact skin surface overlying a large, well-perfused muscle tissue to allow optimal dissipation of energy. Ideally, this should be as close to the operative site as possible (AfPP 2007), at the buttock, posterior or anterior thigh, mid or lower back, upper calf or abdomen (Wicker & O'Neill 2010). Dispersive electrodes should not be placed over scar tissue, hairy skin, bony prominences, metal prosthesis and areas distal to a tourniquet. Hair should be shaved if necessary as imperfect bonding of a dispersive electrode to skin caused by moisture or hair can lead to failure of the equipment (Phippen & Wells 1999, Wicker & O'Neill 2010). However, if an electrode does not adhere satisfactorily, a new dispersive plate should be repositioned at a different site. In the cases of existing skin conditions such as epidermolysis bullosa, a bipolar diathermy should be used instead of dispersive electrodes.
The dispersive electrode should never be cut or trimmed as reducing the surface area can cause serious malfunctioning by increasing the impedance of the electrical current, and increasing the risk of burns. This concept can understood by the equation stated by Covidien (2008) where: Burn = Current x Time / Area of electrode Therefore, larger patient return electrodes will minimise the risk of burns.
Dispersive electrodes that have been removed from a patient's skin should be discarded. The surgeon should ensure that the dispersive electrode is removed carefully without denuding the surface of the skin, and any breach in skin or burns identified should be documented. The surgeon should be informed of all injuries and necessary treatment commenced immediately. An incident form should be completed by the practitioner who removed the electrode or the nurse in charge, and accurate documentation and handover to recovery and ward should be done. The surgeon or anaesthetist should finally inform the patient and relatives of any adverse events and the likely management and prognosis. It is also important to evaluate and document the skin quality and integrity in the perioperative care plan before and after the use of diathermy (AfPP 2007).
Special precautions need to be taken in certain circumstances. These include procedures on patients with pacemakers, and cardiac and cochlear implants. There are also special considerations in laparoscopic and arthroscopic surgery and they are outlined below.
Pacemaker and cardiac implants There is an increasing number of patients who are now being fitted with cardiac pacemakers and automatic cardioverter implantable defibrillators (ACID) (Allen 2006). Especially with monopolar diathermy, it is understandable that there is severe risk of malfunctioning of the cardiac device or even fatal arrythmias. Many of these patients will be identified at a presurgical assessment clinic. If identified, it should be clearly documented in the patient's case notes for the attention of the operating surgeon. Precautionary checks should be performed prior to surgery. Knowing when the device should be disabled or reprogrammed requires careful consideration and consultation between the cardiologist, anaesthetist and surgeon.
The Medicines Healthcare products Regulatory Agency (MHRA) have published guidelines (MHRA 2006) on the management of patients with implantable cardiac devices in the presence of surgical diathermy. The guidelines advise against the use of any diathermy device in these patients, but if it is necessary, bipolar diathermy should be used. The ACID will need to be deactivated before diathermy is used. It is important that a cardiac resuscitation team and functioning external defibrillators are available (MHRA 2006). The anaesthetist should ensure continual ECG monitoring is set up and that all cables are kept away from the pacemaker. They should also connect the leads to a defibrillator for any intraoperative emergencies. The overall aim is to obtain an accurate history and to use bipolar diathermy if there is any doubt.
Cochlear implants in ENT surgery
As with implanted cardiac devices, certain precautions should be observed for patients with cochlear implants. Ideally, bipolar diathermy should be used. If monopolar diathermy has to be used, the distance between the active electrode and the dispersive electrode should be kept as short as possible. This is to ensure that the current path between the surgical site and dispersive electrode does not pass through the vicinity of the implant stimulator or leads (Smith & Smith 2001).
Laparoscopic and arthroscopic surgery
Similar risks and precautions that apply to open surgery are also applicable to laparoscopic and arthroscopic surgery. Current can escape from crevices or cuts in the insulation and can result in burns to the exposed areas. For example, there is a risk of unintentional bowel perforation. Therefore, all insulated laparoscopic and arthroscopic equipment must be checked before and after use to ensure that there are no defects (AfPP 2007). A non-conducting trocar used at a low voltage will substantially reduce the risk of capacitive coupling. If using a metal trocar (conducting trocar) the surgeon should ensure a good contact with the abdominal wall (HSE 2002) to further reduce the risk of capacitive coupling.
It is important to be aware of other laparoscopic instruments, especially metal ones, in the vicinity to avoid direct coupling. Laparoscopic active electrodes which are damaged should be disposed of safely, and disposable single use laparoscopic active electrodes should never be re-used or autoclaved (Hay 2007, HSE 2002). Laparoscopic bipolar diathermy instruments should be used to keep the current spatially as minimal as possible (AfPP 2007, Jones et al 2006). In arthroscopic surgery extreme care should be taken whilst irrigating the joint and the saline irrigation should be kept on the opposite side of diathermy machine to prevent spillage of liquid. Diathermy pedals should be well-insulated and waterproof.
Developments in haemostasis
With research and developments in electrical and surgical sciences, highly precise and safer devices are becoming available, but they come at a high financial cost. With evolution of endoscopic and reconstructive surgery there has been a high demand for new technology to achieve precise vascular control. Suture ligation can be time-consuming and cumbersome during laparoscopic dissection. Titanium and plastic clips have been used for haemostasis, but more recently energy sources such as ultrasonic coagulating shears and bipolar thermal energy devices have become popular (Harold et al 2003). Torsional mode ultrasonic coagulating shears have recently been developed for endoscopic and conventional surgery. The torsional mode shears had the extended ability to coagulate larger-sized vessels up to 7.4 mm diameter with good results (Ching & McMahon 2007). The invention of the gamma knife is exploited in neurosurgery to operate on small brain tumours and arteriovenous malformation by stereotactically directing high doses of radiation to destroy or coagulate the target (Siegfried et al 1998). This accuracy and safety will drive newer technological discovery which will be the future of today's diathermy.
Diathermy should be used safely and judiciously. Staff should be adequately trained and supported to set it up. It is important that practitioners are aware of the risks associated with diathermy and take steps to avoid any complications. All necessary equipment safety checks must be performed preoperatively. Any adverse event should be recognised early and dealt with according to local protocol. With constantly emerging new technological advances, the future of diathermy is entering into an exciting era where cutting and coagulation will be achieved with fewer risks and greater precision. Safety will however continue to be one of the most important considerations in its use.
Provenance and Peer review: Commissioned by the editor; Peer reviewed; Accepted for publication August 2010.
What are the different types of diathermy? How would you choose what type to use?
Notional Learning Hours
Knowledge and Skills Dimension
Core: Health, safety and security
Core: Service improvement
It is the responsibility of the whole team to ensure that diathermy is used safely and there are no complications. Reflect on your particular role in this. How do you contribute towards safe diathermy use?
Notional Learning Hours
Knowledge and Skills Dimension
Core: Health, safety and security
Core: Service improvement
A patient with a pacemaker is about to undergo a hip replacement. What is the role of each member of the perioperative team in ensuring there are no diathermy complications? Discuss these with a colleague.
Notional Learning Hours
Knowledge and Skills Dimension
Core: Health, safety and security
Core: Service improvement
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About the authors
Anish G Potty
Speciality Registrar, Trauma and Orthopaedics, Royal
National Orthopaedic Hospital, Stanmore
MBChB, MSc, MRCS, PhD
Academic Clinical Fellow, University College London,
Institute of Orthopaedic and Musculoskeletal
Science, Royal National Orthopaedic Hospital,
Hitesh D Tailor
Medical Student, University College London Medical
No competing interests declared
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Correspondence address: Wasim Khan, Academic Clinical Fellow, University College London, Institute of Orthopaedic and Musculoskeletal Science, Royal National Orthopaedic Hospital, Stanmore, Middlesex, London, HA7 4LP. Email: email@example.com
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