Anesthesia & Equipment 1

4. Anesthesia Equipment and Anesthetics

INTRODUCTION

Administration of anesthesia is an essential technique in the operation theater and is required for most surgical patients.

•     The technique selected is related to the surgical procedure and the drugs and equipment available in the OT.

•     It is planned so as to suit each patient’s specific needs.

•     All anesthesia technique used should be safe for all types of patients.

In anesthesia potent drugs are used and they:

•     Produce loss of consciousness

•     Depress circulation

•     Depress respiration

•     Produce sympathetic blockade and muscle paralysis.

Anesthetics drugs or the surgical procedures may result in:

•     Unwanted respiratory or circulatory reflex responses (Side effects)

•     Sometimes, the procedure may demand unphysiologic positioning of the patient producing circulatory or respiratory interferance

•     The procedure may cause massive blood loss.

      These are some of the effects that the anesthetists should anticipate and take care to counteract and provide ‘safe anesthesia’ covering all these factors. To achieve this objective an anesthetist needs to master the knowledge of the effects of relevant drugs and equipments used during the procedure. Various anesthetic procedures are used which includes:

•     General anesthesia.

•     Regional includes epidural spinal and caudal blocks.

•     Local techniques usually administered by surgeon for minor procedures.

•     Monitored anesthesia care (MAC) is a combination of local infiltration with IV analgesia the potential vital signs and analgesia needs are monitored and further medication provided.

•     Conscious sedation analgesia. This is used for short-term surgical and diagnostic procedures like endoscopy.

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ELECTRIC EQUIPMENT 13 Prevention electrocution

PREVENTION OF GROSS ELECTROCUTION
IN THE OPERATING THEATER

1.   Avoid portable distribution boards whenever possible.

2.   Use ceiling-mounted pendant supplies whenever possible, as they are less likely to be damaged than those on the floor and are unlikely to become wet. Keep water and electricity apart.

3.   Avoid the use of long mains supply cables, and avoid damage to cables by knotting, equipment’s wheels, etc.

4.   Notify engineering staff of any visible damage to equipments or cables.

5.   Make sure that regular maintenance records are kept and are available for inspection by the user.

Internet Website

1.   American Society for Laser Medicine and Surgery. http:/www.aslms.org.

2.   Association for Advancement of Medical Instrumentation (AAMI). http:/www.aami.org.

3.   Occupational Safety and Health Administration. http/www.osha.gov.

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ELECTRIC EQUIPMENT 12 Ultrasonic surgical systems

ULTRASONIC EQUIPMENT

The CUSA (Cavitron Ultrasonic Surgical Aspirator) is used in the body to fragment and aspirate relatively soft tumor tissue.

•    Ultrasonic techniques are well established in neurosurgery for rapid, efficient removal of intracranial and spinal cord tumors.

•    Their use is in resection and dissection applications in:

     a.  Liver.

     b.  Kidney.

     c.  Spleen.

     d.  Pancreas and urology, the application is gaining popu­larity.

•    Ultrasonic surgery is carried out with the aid of a special instrument known as the CUSAtm—(Cavitron TM Ultrasonic Surgical Aspirator).

•    This is an acoustic vibrator which consists of three distinct components (Fig.):

     a.  Transducer: A magnetic device which converts electro-magnetic energy into mechanical vibrations. The transducers is composed of a stack of nickel alloy laminations. A magnetic field is produced by a coil placed around the laminations and causes mechanical motion of approximately 300 microns.

     b.  Connecting body: Mechanically couples the motion of the transducer to the surgical tip; it also amplifies the vibration motion of the transducer.

     c.  Surgical tip: Completes the motion amplification and also contacts the tissue. The tip is relatively long compared to its diameter and is constructed to provide adequate motion amplification.

•    The electric coil which is permanently fitted in the hand piece, surrounds the transducer. This coil receives 23,000 cycles per second (hertz) alternating electric current from the console and activates the transducer

•    The hand piece is connected to the console by a cable which includes the tubing for circulating fluid between the cooling water canister in the console and the hand piece

•    Since the electric coil has a current flowing through it and the transducer lamination are moving back and forth 23,000 times per second, heat is generated and absorbed by the water circulating within the hand piece

•    This keeps the hand piece at a comfortable temperature for the surgeon.

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ELECTRIC EQUIPMENT 11 Cryosurgical Systems

CRYOSURGICAL SYSTEMS

Cryotherapy, the application of extreme cold to tissues and is a useful technique for the destruction of tissues. It is characterized by minimal bleeding or pain in the postoperative period. Cryosurgical systems are well established in many surgical specialities including:

•    General surgery,

•    Gynecology,

•    Dermatology,

•    Neurology, and

•    Urology.

     The first practical equipment for the control and maintenance of extreme low temperature in surgery was produced in 1962. The apparatus was not very sophisticated and used liquid nitrogen to achieve low temperature in the region of –196 degree Celsius. This very low temperature was subsequently found to exceed requirements, and Amoils developed a more simple apparatus which used nitrous oxide or carbon dioxide to achieve temperatures in the region of –70 degree Celsius. The design principles established by Amoils (Fig. 2.6) are still used in modern cryosurgical equipment which employs high-pressure, non-syphon cylinders of N2O and CO2.

•    Cryosurgical systems consist of flexible tubing connecting the gas flow control unit to a cryoprobe or working tip which comprises two concentric tubes

•    The inner tube delivers nitrous oxide or carbon dioxide at pressures between 4,000 kPa and 6,000 kPa to a narrow orifice in the end

•    The sudden expansion of this gas through the ‘Joule- Thompson Orifice’, produces a rapid drop in temperature of the probe surface forming an ice ball

•    The expanded gas is then returned at atmospheric pressure along the outer tube

•    Some cooling along the shaft of the probe occurs and can be a disadvantage, for example in neurosurgery

•    To overcome this, Spembley manufacture a probe which employs a reversed gas flow. This design enables the incoming gas to be carried to the probe tip via the outer of the two concentric tubes; it is allowed to expand through an annular orifice, being finally released through the central tube.

•    The incoming gas acts as an insulating barrier and the cooling is confined to the probe tip.

          Cryosurgery has been useful in the treatment of early skin cancer. It is being explored in the treatment of prostate, liver and bone.

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ELECTRIC EQUIPMENT 10 Laser Eye protection

Guidelines to Eye Protection during Laser Surgery

•     Ensure that everyone in the laser room is wearing the appropriate eye protection before activating the laser. The eye wear should have the laser wavelength protection and optical density of the lens material inscribed on it.

•     A special lens cover can be placed over the eyepiece of an endoscope to protect the physician’s eye from laser back­scatter. Remember that the physician’s other eye will be unprotected.

•     Everyone in the laser room should wear eye protection during laser endoscopic procedures.

•     An automatic lens shutter can be connected to a microscope head to provide eye protection for persons viewing the procedure through the microscope.

•     When general anesthesia is used, cover the patient’s closed eye with moistened gauze pads. When the patient is awake, place the appropriate glasses or goggles on the patient. Explain the need for eye protection to the patient.

•     During laser surgery near the eye, a special laser eye shield may be placed directly on the anesthetized eye surface.

•     Ensure that the appropriate protective eyewear is available at all entrances to the laser room for anyone entering the area.

•           When storing protective eyewear, guard against scratches and mishandling. Scratches on the lenses may decrease their effectiveness.

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ELECTRIC EQUIPMENT 9 Lasers

LASERS

Laser light is a part of the light spectrum which has been collimated and made coherent so that the waves travel in the same direction in parallel. This beam now carries laser energy measured in Joules and the energy delivered is proportionate to the exposure measured in seconds. The principle of laser generation has been shown in the figures above. New laser systems have been introduced into use. The five components of a system are:

•     Laser head

•     Excitation source

•     Ancillary components

•     Control panel

•     Delivery system.

      The Table 2.1 summarises the characteristics of those in use in surgery.

•     A laser is an instrument equipped to produce a parallel beam of high intensity light which can be focussed on a very small spot 

•     The development of surgical lasers during the last decade has made a significant contribution to microsurgery

•     Used with an operating microscopes or fiberscopes a wide range of microsurgical procedures have now become possible, for example:

      a.   Sutureless microvascular anastomosis.

      b.   Excision of the posterior capsule of the lens through the transparent cornea.

      c.   Coagulation of bleeding peptic ulcers using a flexible gastroscope.

•     In laser surgery, the light beam heats the target tissue and causes:

      a.   Thermal tissue destruction.

      b.   First with local edema.

      c.   Then denaturation of protein.

      d.   Contraction of tissue due to alteration of fibrous tissue protein.

      e.   And finally boiling of cell water and vaporization.

      f.    Generally, low energy exposure results in coagulation of blood vessel.

      g.   Higher energy exposure produces a precise incision by vaporization of the tissue at the focal point.

            It is important that eye protection be worn during procedures

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ELECTRIC EQUIPMENT 8 Surgical Cautrey

Surgical Cautery

•     Electric cautery is used to destroy superficial skin lesions. The wire tip is raised to red heat by means of an electric current

•     This heated cautery point is then applied to the tissue area to cause tissue death through coagulation

•     The current source may be a low-voltage battery or trans­former connected the mains, although the transformer is preferable, as the output is more constant than that of a battery

•     The transformer has a rheostat knob which may be adjusted to alter the voltage applied to the platinum point

•     The cautery must not be used any hotter than at red heat, as too high a current will cause rapid burning out of the cautery wire and reduce its life span

•     The cautery point are various sizes and shapes (Fig. 2.4) are mounted in a heat-resisting handle to which are connected two wires

•     These wires are then connected to the transformer which must be switched off at the wall socket

•     The cautery must be connected to the cautery terminals

•     After connecting the wires the transformer may then be switched on.

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