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American Society of Anaesthesiologists (ASA) Score?
The ASA score is a subjective assessment of a patient’s overall health that is based on five classes (I to V).
- I - Patient is a completely healthy fit patient.
- II - Patient has mild systemic disease.
- III - Patient has severe systemic disease that is not incapacitating.
- IV - Patient has incapacitating disease that is a constant threat to life.
- V - Moribund patient who is not expected to live 24 hour with or without surgery.
Eagle Preoperative Cardiac Risk Assessment Tool for non cardiac surgery?
Eagle score is a five-point scoring system, used mainly for vascular patients, and allows for an accurate estimate of a patient's risk of dying during non cardiac surgery.
- The Eagle’s criteria includes:
- Age >70 years 1
- Diabetes mellitus 1
- Angina 1
- Q wave in ECG 1
- Ventricular ectopics 1
- <1—low risk. No further tests required
- 1–2—needs noninvasive tests
- >3—needs angiography
(Note - Goldman’s cardiac risk index is a scoring systems for predicting cardiac complications)
Principles of diathermy?
- When an electrical current passes through a conductor, some of its energy appears as heat. The heat produced depends on:
- • the intensity of the current;
- • the wave form of the current;
- • the electrical property of the tissues through which the current passes;
- • the relative sizes of the two electrodes.
- Diathermy can be used for three purposes:
- 1 Coagulation: the sealing of blood vessels.
- 2 Fulguration: the destructive coagulation of tissues with charring.
- 3 Cutting: used to divide tissues during bloodless surgery
Unipolar (or monopolar) device?
- In monopolar diathermy, which is the most commonly used form, an alternating current is produced by a suitable generator and passed to the patient via an active electrode which has a very small surface area. The current then passes through the tissues and returns via a very large surface plate (the indifferent electrode) back to the earth pole of the generator.
- Effectiveness of energy conversion into heat is inversely related to the area of contact. As the surface area of contact of the active electrode is small in comparison to the indifferent electrode, the concentrated powerful current produces heat at the operative site. However, the large surface area electrode of the patient plate spreads the returning current over a wide surface area, so it is less concentrated and produces little heat.
- Unipolar devices can be used to incise tissue when activated with a constant waveform and to coagulate when activated with an intermittent waveform.
- In the cutting mode, much heat is generated relatively quickly over the target, with minimal lateral thermal spread. As a result, the device cuts through tissue without coagulating any underlying vessels.
- In contrast, in the coagulation mode, electrocautery generates less heat on a slower frequency, with the potential for large lateral thermal spread. Such spread results in tissue dehydration and vessel thrombosis.
A large grounding pad must be placed securely on the patient for the unipolar electrosurgical or electrocautery device to function properly and prevent thermal burn injury at the current reentry electrode site.
- In bipolar diathermy, the two active electrodes are usually represented by the limbs of a pair of diathermy forceps. Both forceps ends are therefore active and current flows between them and only the tissue held between the limbs of the forceps heats
- up. The tissue grasped between the tips of the instrument completes the circuit.
- In generating heat that affects only the tissue within the short circuit, it provides precise thermal coagulation.
- Bipolar electrocautery is more effective than the monopolar instrument in coagulating vessels because it adds the mechanical advantage of compression of tissue between the tips of the instrument to the thermal coagulation.
- Bipolar electrocautery is particularly useful when conducting a procedure in which lateral thermal injury or an arcing phenomenon needs to be avoided.
Mechanism of burn in cautery?
- • Faulty application of the indifferent electrode with inadequate contact area.
- • The patient being earthed by touching any metal object, e.g.the Mayo table, the bar of an anaesthetic screen, an exposed metal arm rest or a leg touching the metal stirrups used in maintaining the lithotomy position.
- • Faulty insulation of the diathermy leads, either due to cracked insulation or instruments such as towel clips pinching the cable.
- • Inadvertent activity such as the accidental activation of the foot pedal, or accidental contact of the active electrode withother metal instruments, such as retractors, instruments or towel clips
What is Channelling in electrocautery?
- Heat is produced wherever the current intensity is greatest.Normally, this would be at the tip of the active electrode, but if current passes up a narrow channel or pedicle to the active electrode, enough heat may be generated within this channel or pedicle to coagulate the tissues. This can prove disastrous, for example,
- • coagulation of the penis in a child undergoing circumcision;
- • coagulation of the spermatic cord when the electrode is applied to the testis.
In such situations, diathermy should not be used, or if it is necessary,then bipolar diathermy should be employed.
Complications of diathermy?
- Interfere Pacemakers function
What is ligasure?
- It fuses the vessel walls to create a permanent seal
- It uses a combination of pressure and energy to create vessel fusion which can withstand up to three times the normal systolic pressure.
- New technology of the ligasure system involves advanced monopolar technology that uses the body’s own collagen and elastin to both seal and divide
- Designed to manage the energy delivery in a precise manner and results in an automatic discontinuation of energy once the seal is complete, thus removing any concern that the surgeon has to use guesswork as to when the seal is complete.
- .Lgasure can seal vessels of up to 7 mm diameter, with an average seal time of 2–4 seconds, as well as pedicles, tissue bundles and lymphatics with a consistent controlled and predictable effect on tissue, including less dessication.
- Therefore, it can dissect, seal and divide and was designed to be the only tool that a surgeon would need.
- It is relatively expensive
Mechanism of action of laser?
- LASER is Light Amplification by Stimulated Emission of Radiation.
- Lasers use photons to excite the chromophore molecules with intarget tissue and generate kinetic energy that is released as heat, which causes protein denaturation and coagulation necrosis. This effect occurs without much collateral damage to surrounding tissue.
- The most common lasers in use are the argon, carbon dioxide, and neodymium:yttrium-aluminum-garnet(Nd-YAG) lasers.
High-Frequency Sound Wave Techniques
- Ultrasound has had a strong impact on the practice of modern medicine. It has different functions, depending on the frequency of ultrasound generated by the machine.
- At a low power level, it causes no tissue damage and is mainly used for diagnostic purposes.
- With a high-frequency setting, ultrasound can be used to dissect, cut, and coagulate.
- Several high-frequency ultrasonic devices are available for use in surgical practice
- - Harmonic Scalpel
- - Extracorporeal shock wave lithotripsy
- - Ultrasonic Cavitation Devices
Short note on Harmonic scalpel. [TU 2072,74]
- The harmonic scalpel is an instrument that uses ultrasound technology to dissect tissue in bipolar fashion with only minimal collateral tissue damage.
- The device vibrates at a high frequency, approximately 55,000 times per second, to cut tissue.
- The high frequency vibration of tissue molecules generates stress and friction in the tissue, which generates heat and denaturation of protein.
- It provides cutting precision, even through thickened scar tissue, and visibility is enhanced due to less smoke being created by this system during use compared to routine electrosurgery.
- However, the harmonic scalpel does take longer to cut and coagulate tissues than diathermy,and while diathermy can be used to coagulate a bleeding vessel at any time, the harmonic scalpel can only coagulate as it cuts.
- Patients experience less swelling, bleeding and bruising after the use of the harmonic scalpel than when a conventional scalpel.
- Blood vessels are sealed with a much lower temperature than conventional diathermy and so there is less thermal damage to adjacent tissue, with less charring and dessication.
- Use of the harmonic scalpel reduces operative time and recovery is thus enhanced.
Write short note on Robotic Surgery? [TU 2072/4]
Robotic surgery means computer assisted surgery, and robotically assisted surgery are terms for technological developments that use robotic systems to aid in surgical procedures. Robotically-assisted surgery was developed to overcome the limitations of minimally-invasive surgery and to enhance the capabilities of surgeons performing open surgery.
Types of Robotic surgery system
- 1. Supervisory controlled robotic surgery system :
- Follows specific set of instructions.
- Surgeon should program the robot.
2. Tele surgery system
: Tele surgery, also called remote surgery, is performed by a surgeon at a site removed from the patient. Surgical tasks are directly performed by a robotic system controlled by the surgeon at the remote site.
- 3. Shared control robotic surgery System :
- Surgeons most of the work.
- Surgeons must operate surgical instruments themselves.
- Robot’s does not work unless surgeons give data to robot.
- Applications :
- 1.Cardiac Surgery :Bypass surgery is performed by Da Vinci system.
- 2. Gastrointestinal surgery : Surgery either the ZEUS or Da Vinci system.
- 3. Gynecology : Robotic surgery in gynecology is one of the fastest growing field.
- 4. Neurosurgery: Robotic Surgery is considered as safest surgery for neuron.
- 5. Orthopedics: Surgical robotics has been used in many types of orthopedic surgical.
- 6. Pediatrics : Surgical robotics has been used in many types of pediatric surgical procedures.
- Advantages :
- 1.Telesurgery: The use of computer console to perform operations from a distance.
- 2.Less Pain: The patient would experience less pain, trauma and bleeding, which means a faster recovery.
- 3.Enhanced precision: Surgery with help of robots will help to remove errors and does surgery with high accuracy.
- 4.Decreases the fatigue: It helps to decrease the fatigue of the doctors during surgery hours.
- 1.Question of safety : If any error is coded to robot it may harm the human during surgery.
- 2.Time: Robotic assisted heart surgery can take nearly twice the amount of time that a typical heart surgery takes.
- 3.Cost: At this early stage in the technology, the robotic systems are very expensive