Diathermy Flashcards
diathermy current
hertz osscillations per second
400kHz-2.5mHz (10mHz)
standard current is 50-60Hz (hairdryer)
nerves stimulated 100Hz
plate vs electrode surface area
heat generated by high current density due to small surface area
treatment electrodevs patient electrode
high frequency current from generator
how does bipolar work
current down active electrode and back to generator rather than running through patient
cutting vs coag
coag 94% off 6% on
higher amplitude, low er voltage
non continuous
charring over large area
cutting 100% on
low voltage
intense rapid heat 1000C
vapourisation water in cells
where to apply pad
well vascularised muscle area with no hairs
70cm2 surface area
avoiding burns
avoiding pooling alcohol prep diathermy pad away from metal at least 15cm away short term use bipolar patient no touching metal objects burn = current x time / area
risks to implantable devices -2
phantom reprogramming - work in different mode
due to use of high frequency current stimulate the radiofrequency impulse by which pacemakers are reprogrammed
pacemaker inhibition, if dependent on beat may stop, if patient pacemaker depedent heart stops beating
what precautions to take for cardiac devices 4
all information on pacemakers
serial numbers, date implantation, hospital site, indication, result of last check, should have card with this information
cardiac clinic contacted for precise indication
try avoid diathermy
pacemaker check within 6 months
check post procedure
ICDs pre procedure to monitor only
plate elctrode not in path pacemaker avoid inappropirate grounding ECG leads diathermy machine well away from paceamker >1cm heart monitored defib available as well as ex pacemaker short bursts different types of ICD may not need turning off follow hospital SOP for ICD electrophysiology department
types of minimally invasive surgery burns
insulation failure
direct coupling - electrode and camera touching
capcitative coupling - charging of plastic port as an insulator which can discharge electricity to internal organs
how does harmonic work
coaptive coagulation
active blade vibraets 50kHz
compress vessel walls
controls bleeding at 100c lower temperatures
generates protein coagulum behind the point
up to 5mm
ligasure
bipolar diathermy and pressure combines metls collagen and elastin and reforms into seal
feedback loop stops energy once seal complete
up to 7mm
higher heat generation around ligasure
bipolar turp mechanism
size of bipolar loop
current
flow of electrons during a period of time measured in amperes
voltage
force pushing current through the resistance measured in volts
resitance
obstacle to the flow of current measured in ohms
what is electric current
electrons flow from one atom to the orbit of an adjacent atom.
voltage is the force or push that allows electrons to travel from atom to atom
if encounter resistance heat is produced
electrocautery vs electrosurgery
electrocautery only heated element in contact with patient body
direct current, flowing in one direction
in electrosurgery the patient is included in the circuit
uses alternating current
electrosurgery circuit
electrosurgical generator providing flow of electrons and voltage
active electrode
patient (tissue providing impedance)
patient return electrode
normal electrical current alternating frequency
why electrosurgery is higher
when does muscle and nerve stimulation cease
which frequencies safe
60 cycles per second 60Hz
would cause excessive NM stimulation
cease at 100,000 Hz or 100 KHz
so electrosurgery safe at 100Khz and above
the electrosurgical generator takes 60 cycle current and increases freq to 200KHz
bipolar
active and return electrode
both active and return electrode are at site of surgery
two tines of the forceps perform the active and return
only tissue grasped is included in electrical circuit
no patient return electrode needed
bipolar
active and return electrode
both active and return electrode are at site of surgery
two tines of the forceps perform the active and return
only tissue grasped is included in electrical circuit
no patient return electrode needed
monopolar electrosurgery
the active electrode is the surgical site
patient return electrode is somewhere else on body
current passes through patient and completes circuit
cut vs blend vs coag
produce a variety of electrical waveforms which produce different tissue effects
modification of the waveform so that the duty cycle or on time is reduced
high heat produced rapidly causes vaporisation
cut - vaporise or cut tissue
100% on
low voltage
coag 6% on, 94% off
produces less heat
coagulum produced
high voltage
blended - mixture of both from high to low duty cycle
cutting
how it works
intense heat rapidly
using electrical sparks that focus intense heat at surgical site
by sparking to tissue produces maximum current concentration
to create spark hold slightly away from tissue
variables influencing effect on tissue
waveform voltage power setting size electrode time manipulation electrode type tissue
what is current division
current split or divide and follow more than one path to ground
follows easiest most conductive path
any grounded object can complete circuit
resulting in ‘alternate site burns’
what is isolated system
isolated generator technology
completed not by ground byt by the generator
even though grounded objects remain in op room
electrosurgical current from isolated generators will not recognise grounded objects as pathways to complete circuit
recognises patient electrode as preferred path back to generator
what is isolated system
isolated generator technology
completed not by ground byt by the generator
even though grounded objects remain in op room
electrosurgical current from isolated generators will not recognise grounded objects as pathways to complete circuit
recognises patient electrode as preferred path back to generator
return electrode burns
isolated circuits prevent alternate site burns but not return electode burns
return electrodes are not inactive nor passive
only differ from active electrode in their size and relative conductivity
return electrode placement
close to operative site on conductive tissue well vascularised muscle mass avoid vascular insufficiency irregular body contours bony prominences
return electrode monitoring
REM equipped generators must use a patient electrode that is compatible with split appearance
actively monitor the amount of impendance at patient return electroude at the patient/pad interface
vessel sealing techology and enseal
uses biploar
feeback controlled
vessels up to 7mm
can withstand three times normal systolic BP
measures initial impedance of tissue and chooses appropirate settings
delivers pulsed energy with continuous feedback control
senses that tissue response is complete and stops the cycle
safety considerations electrosurgery -3
direct coupling
insulation failure
capcitive coupling
direct coupling
actives electrode whilst near another metal instrucment
second instrument become energised
insultation failure
when using high voltage coag mode
high voltage can spark through compromised insulation or blow holes in weak insultation
breaks in insulation create an alternate route for current which if concentrated can cause injury
capacitive coupling
inadvertant capicitator may be created by surgical instrument
capacitor creates an electrostatic field between the two conductors (condutive active electrode and condutive metal cannula)
as a result one conductor can through an electrostatic field induce a current in second conductor
capacitive coupling
inadvertant capicitator may be created by surgical instrument
capacitor creates an electrostatic field between the two conductors (condutive active electrode and condutive metal cannula)
as a result one conductor can through an electrostatic field induce a current in second conductor
avoiding electrosurgical complications in MIS 7
inspect insulation lower possible power low voltage cut waveform brief intermittent activation not active near other instrument bipolar do not use hybrid cannula system
safety precautions in theatre
not used near flammable alcohol agents
non condutive holster /quiver
cords not wrapped around metal instruments or bundled toegther in case of current leak
safety precautions in theatre
not used near flammable alcohol agents
non condutive holster /quiver
cords not wrapped around metal instruments or bundled toegther in case of current leak
duty cycle
the duty cycle (defi ned as the ratio of the “on” time to the period of a single
“on–off” cycle
frequency bipolar diathermy
250KHz to 1Mhz
frequency bipolar diathermy
250KHz to 1Mhz
Gyrus vs TURIS system bipolar TURP
The Gyrus plasmaKinetic (PK) system™ is a bipolar coaxial system with the
active and return electrodes located in the same axis, separated by a ceramic insulator.
Such an intricate design has raised the cost of each resection loop. In the TURIS
system, (Olympus SurgMaster resectoscope™, with a 26F outer diameter), the
SurgMaster™ generates a high frequency current that passes through the active
electrode (resection loop) and returns via the return electrode (sheath of the resectoscope).
The generator is usually set for cutting, and coagulation at 180 and 100 W
respectively. This is a simpler and less costly bipolar design with potentially similar
clinical benefi ts.
harmonic scalpel
simultaneously cuts and cauterises tissue
PE cyrstal in handpiece
active blader delivers US energy
high grade frictional foce and heat
ultrasonic energy mechanical in nature and works at much lower temperatures
controls bleeding by coaptive coagulation at lower temps
50 to 100C
coaption compression of vessel walls
followed by sealing with coagulation
intrsument blade vibrates at 55,500 Hz ie 55kHz
causes protein in the vessel wall to form a coagulum
but can result in heating of tip to 100C
temperatures used in electorsurgery and lasers
Electrosurgery and lasers coagulate by burning at high temperatures
causing obliterative coagulation at between 150°C and 400°C
Blood and tissue are thereby desiccated and oxidised, forming a charred eschar that covers and
seals the bleeding area. Rebleeding can occur when the forceps used during electrosurgery
are removed, when they may stick to the cauterised tissue and disrupt the
eschar
liagsure
electrothermal bipolar device
delivers bespoke temperature
to seal collagen and elastin
pressure and energy to create vessel fusion
radiofrequency energy to melt the collagen and elastin in vessel walls and reforms it into a permanent plastic like seal
does not rely on proximal thrombus
feedback controlled response system stops energy delivery
mimises thermal spread 2mm
free of sticking or charring
can wtihstand 3 x normal BP
vessels up to 7mm
liagsure
pressure and energy to create vessel fusion
radiofrequency energy to melt the collagen and elastin in vessel walls and reforms it into a permanent plastic like seal
does not rely on proximal thrombus
feedback controlled response system stops energy delivery
mimises thermal spread 2mm
free of sticking or charring
can wtihstand 3 x normal BP
vessels up to 7mm
what frequency of current increases risk current leakage to tissues
> 3MHz
what temp does vapourisation occur
ie. cut is over 200c
coagulation is over 45 degrees
bipolar and creation of plasma
plasma is one of the four fundamental states of matter
created by applying energy to a gas
molecules then ionised turning gas into plasma
plasma is conductive, allows energy to cross at lower energy levels
leads to lower operating temperatures and less thermal spread
tissue vapourised by locally confied denaturation proces
while surrounding tissue effects minor
TURIS system
what is diathermy
passage of high frequency alternating current in the range 400khz to 10 Mhz through body tissue
where the current is concetrated heat up to 1000C is produced to allow cutting or coagulation
why nerves and muscles not stimulated
stimulated at 100khz or below
with such high frequency no time for cell membranes to become depolarised
surface area of diathermy plate
70 to 150 cm squared
power of cutting vs coag
125-250W
coag is 10-75W
how does blend work
only in cutting mode
50% duty cycle on/off
main complications diathermy
flammable explosion patient plate site obsturator kick end artery necrosis pacemakers
