Surgery – Instruments – Electrical application
Patent
1997-12-01
2000-01-04
Dvorak, Linda C. M.
Surgery
Instruments
Electrical application
606 38, 606 39, A61B 1736
Patent
active
060104996
DESCRIPTION:
BRIEF SUMMARY
The current invention relates to apparatus for use in the electrosurgical field and in particular in relation to the provision of apparatus for cutting body tissue and/or coagulation such as is required in, for example, endoscopic surgery which is increasingly common.
When using apparatus of this type to, for example, cut parenchymal organs the surgeon wishes to obtain efficient heamostasis either as a result of coagulation to a greater or lesser depth as the cut is being made or as a result of partial coagulation of the bleeding vessels once the cut is completed. The efficiency with which the bleeding can be stopped depends upon the intensity of thermal coagulation; and the greater the depth of coagulation inside the tissue, the greater the heamostatic effect. At the same time however it must be ensured that no more tissue suffers thermal damage during cutting and coagulation than is absolutely necessary in order to obtain the desired effect as the damage caused is irreparable. This is an important consideration as increasingly, higher output currents are used to cut. As the higher currents and hence power is provided so the risk of electric current channelling along unseen or obscured body organs adjacent the cutting area is increased and can cause damage to vital anatomical structures and increase the risk of peripheral burns to the patient.
For many years work has been undertaken in an attempt to provide apparatus which allows accurate high powered cutting and coagulation of the body tissue and fluids and which has a minimum risk to the patient upon whom the surgery is performed and also to the surgeon and/or apparatus operator.
In general, when an electrode, which acts as a cutting tool, contacts body tissue an electric arc or spark is created which causes a zone of thermal necrosis to be created beneath and around the area of contact. As the current is applied it passes through individual cell membranes in the patient causing the same to be vapourised and the cut to be created.
One known group of apparatus tape is known as monopolar apparatus which utilises an electrode which forms the cutting and coagulation tool and through which an alternating current of, for example, between 300 kHz and 1 mhz flows. When the electrode is held at a distance from the body no current flows and no cutting action occurs but as the electrode is brought closer to the body tissue a spark will jump across the gap to the tissue if, for example, the voltage is between 1000 to 10000 volts peak to peak.
This apparatus is provided with a separate return electrode which must have a sufficiently large area to minimise the heating effect caused by the current passing through the patient and prevent tissue surface burns. Typically therefore the return electrode is required to be in the form of a plate upon which the patient lies. These plates can be disposable but in any case are relatively expensive. Thus, in this type of apparatus, relatively high powered cutting currents can be obtained but there are inherent risks to the patient who does, in effect, form part of the electrical circuit and is therefore exposed, sometimes dangerously, to burns and tissue damage caused by contact with the plate. In an attempt to minimise the problem the resistance of the return electrode plate is monitored but this tends to be a reactive rather than a proactive monitoring technique which does not monitor the condition of the patient body tissue and therefore does not eliminate the risk to the patient. Thus the monopolar cutting system, although widely used, has many deficiencies which, if they are not to cause damage to the patient, are required to be carefully monitored with additional expensive apparatus.
An alternative group of apparatus is the bipolar cutting apparatus which utilises two electrodes which contact the tissue to be cut and coagulated in close proximity to each other. One electrode operates to supply power to cut and coagulate the tissue and the other acts as a return electrode with the current density on both electrodes being ke
REFERENCES:
patent: 5372596 (1994-12-01), Klicek et al.
Dvorak Linda C. M.
Kearney Rosiland
Nuvotek Ltd.
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