Module 2 Flashcards
what is monopoly energy?
complete circuit
- consists of electrosurgical unit (converts low frequency current from wall to high frequency current or electrode) –> tissue current passes thru –> dispersive electrode connected to generator
how does coagulation occur?
temp >60C —> protein denaturation –> tissue cools and bonds reform haphazardly –> tissue coagulation
How does tissue desiccation occur?
tissue temp rises –> water evaporates and produces desiccation –> as desiccation increases the tissue impedance increases until complete dessication occurs –> current stops flowing due to the very high resistance
at 100C internal water molecules vaporize and the cell explodes
what is the reason for hemostasis in desiccation?
due to fibrous binding between denatured/dehydrated cells of vessel endothelium
tissue heating = ?
(current density)^2
current density = amount of current throughout cross sectional area of tissue
current density = ?
current (amps)/area (cm^2)
- smaller contact area = greater current density and faster heating (tip of electrode)
- larger area of contact for dispersive electrode so less heating
where should you not place electrode Matt?
hairy skin, bony prominences, or scars –> decreases contact area and increased risk of burn
Three modes of monopoly
cut, coag, blend
Cut
heat tissue quickly so cell water is converted to steam –> cell explosion
- minimal lateral thermal tissue damage
- poor thermal coagulation
- low voltage, unmodulated wave form (100% ON)
- to achieve vaporization, electrode should not contact tissue itself
Coag
rapid surface heating and surface eschar formation and shallow depth of necrosis (fulguration)
- intermittent wave form as high voltage
- heat more widely disperses so no significant cutting
- non-contact mode (relies on sparking between electrode and tissue)
blend
mixes cutting and coag wave forms
current diversion
current passes thru unintentional pathways while following path of least resistance
precaution: inspect insulation, use lowest possible power and voltage, brief activation, be in proximity of target tissues, avoid metal (so avoid hybrid ports that are metal and plastic)
monopolar
capacitive coupling
transfer of current from active electrode through insulation to passive electrode (capacitor)
- charge in active electrode is stored in the passive one, the passive one can cause burn in local tissue
ex: monopolar instrument comes in contact with another instrument that is not touching any tissue and stores energy –> it can release that energy when it does touch other tissue
direct coupling
active electode comes in contact with another metal instrument –> thermal injury or injury to tissue out of field of view
narrow return circuit
current passes thru ligated tissue –> increases local current density and unintended excess tissue heating may occur
