Anesthesia

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Anesthesia
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Anesthesia

• From Greek anaisthesis means not sensation
• Listed in Baileys English Dictionary 1721.
• When the effect of ether was discoveredanesthesia
  used as a name for the new phenomenon.

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Basic Principles of Anesthesia

• Anesthesia defined as the abolition of sensation
• Analgesia defined as the abolition of pain
• Triad of General Anesthesia
• need for unconsciousness
• need for analgesia
• need for muscle relaxation

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History of Anesthesia
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History of Anesthesia

• Ether synthesized in 1540 by Cordus
• Ether used as anesthetic in 1842 by Dr. Crawford
  W. Long
• Ether publicized as anesthetic in 1846 by Dr.
  William Morton
• Chloroform used as anesthetic in 1853 by Dr. John
  Snow

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History of Anesthesia

• Endotracheal tube discovered in 1878
• Local anesthesia with cocaine in 1885
• Thiopental first used in 1934
• Curare first used in 1942 - opened the Age of
  Anesthesia

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• Anesthesiologists care for the surgical patient
  in the preoperative, intraoperative, and
  postoperative period . Important patient care
  decisions reflect the preoperative evaluation,
  creating the anesthesia plan, preparing the
  operating room, and managing the intraoperative
  anesthetic.

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Preoperative Evaluation

• The goals of preoperative evaluation include
  assessing the risk of coexisting diseases,
  modifying risks, addressing patients' concerns,
  and discussing options for anesthesia care.

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• What is the indication for the proposed surgery?
  It is elective or an emergency?
• The indication for surgery may have particular
  anesthetic implications. For example, a patient
  requiring esophageal fundoplication will likely
  have severe gastroesophageal reflux disease,
  which may require modification of the anesthesia
  plan (e.g., preoperative non particulate antacid,
  intraoperative rapid sequence induction of
  anesthesia).

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• What are the inherent risk of this surgery?
• Surgical procedures have different inherent
  risks. For example, a patient undergoing coronary
  artery bypass graft has a significant risk of
  problems such as death, stroke, or myocardial
  infarction.
• A patient undergoing cataract extraction has a
  low risk of major organ damage.

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• Does the patient have coexisting medical
  problems? Does the surgery or anesthesia care
  plan need to be modified because of them?

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• Has the patient had anesthesia before? Were there
• Complication such as difficult airway
  management? Does the patient have risk factor for
  difficult airway management?

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Creating the Anesthesia Plan

• After the preoperative evaluation, the anesthesia
  plan can
• be completed. The plan should list drug choices
  and doses
• in detail, as well as anticipated problems .Many
  variations on a given plan may be acceptable, but
  the trainee and the supervising anesthesiologist
  should agree in advance on the details.

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Preparing the Operating Room

• After determining the anesthesia plan, the
  trainee must prepare the operating room .

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Anesthesia Providers

• Anesthesiologist ( aphysician with 4 or more
  yearsof speciality training in anesthesiology
  after medical school)
• Certified registered nurse anesthetist (CRNA),
  working under the direction and supervision of an
  anesthesiologist or a physician
• CRNA must have 2 years of training in anesthesia

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Patient Safety

• Patient risk and safety are concerns during
  surgery and anesthesia .
• Data from a number of studies of death caused by
  anesthesia indicate a death rate ranging from 1
  per 20,000-35,000.
• A fourfoulded decline over the last 30 years even
  though surgical procedures are undertaken on
  increasingly sicker and much higher risk patients
  than in the past.
• Awareness of potential problems and constant
  vigilance (the process of paying close and
  continuous attention) are crucial to good patient
  care.

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Preoperative preparation patient evaluation

• Anaesthesiologist
• reviews the patients chart,
• evaluate the laboratory data and diagnostic
  studies such as electrocardiogram and chest
  x-ray,
• verify the surgical procedure,
• examins the patient,
• discuss the options for anesthesia and the
  attendant risks and
• ordered premedication if appropriate

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The physical status classification

• Developed by the American Society of
  Anesthesiologist (ASA) to provide uniform
  guidelines for anesthesiologists.
• It is an evaluation of anesthetic morbidity and
  mortality related to the extent of systemic
  diseases, physiological dysfunction, and anatomic
  abnormalities.
• Intraoperative difficulties occur more frequently
  with patients who have a poor physical status
  classification.

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Choice of anesthesia

• The patients understanding and wishes regarding
  the type of anesthesia that could be used
• The type and duration of the surgical procedure
• The patientss physiologic status and stability
• The presence and severity of coexisting disease
• The patients mental and psychologic status
• The postoperative recovery from various kinds of
  anesthesia
• Options for management of postoperative pain
• Any particular requiremets of the surgeon
• There is major and minor surgery but only major
  anesthesia

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Types of anesthesia careGeneral Anesthesia

• Reversible, unconscious state is characterised by
  amnesia (sleep, hypnosis or basal narcosis),
  analgesia (freedom from pain) depression of
  reflexes, muscle relaxation
• Put to sleep

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Types of anesthesia careRegional Anesthesia

• A local anethetic is injected to block or
  ansthetize a nerve or nerve fibers
• Implies a major nerve block administered by an
  anesthesiologist (such as spinal, epidural,
  caudal, or major peripheral block)

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Types of anesthesia caremonitered anesthesia care

• Infiltration of the surgical site with a local
  anesthesia is performed by the surgeon
• The anasthesiologist may supplement the local
  anesthesia with intravenous drugs that provide
  systemic analgesia and sedation and depress the
  response of the patients autonomic nervous system

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Types of anesthesia carelocal anesthesia

• Employed for minor procedures in which the
  surgical site is infiltrated with a local
  anesthetic such as lidocaine or bupivacaine
• A perioperative nurse usually monitors the
  patients vital signs
• May inject intravenous sedatives or analgesic
  drugs

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Premedication

• Purpose to sedate the patient and reduce anxiety
• Classified as sedatives and hypnotics,
  tranquilizers, analgesic or narcotics and
  anticholinergics
• Antiacid or an H2receptor-blockingdrug such as
  cimitidine (tagamet) or ranitidine (Zantac) to
  decrease gastric acid production and make the
  gastric contents less acidic
• If aspiration occur this premedication decreases
  the resultant pulmonary damage
• Given 60-90 minutes before surgery, or may be
  given i.v. After the pat. arrives in the surgical
  suite
• NPO for a minimum of 6 hours before elective
  surgery
• Not given to elderly people or ambulatory
  patients because residual effects of the drugs
  are present long after the pat. have been
  discharged and gone home

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Perioperative monitoring

• Undergeneral anesthesia monitoring
• Inspired oxygen analyzer(FiO2) which calibrated
  to room air and 100 oxygen on a daily basis
• Low pressure disconnect alarm, which senses
  pressure in the expiratory limb of the patient
  circuit
• Inspiratory pressure
• Respirometer (these four devices are an integral
  part of most modern anesthesia machine
• ECG
• BP-automated unit
• Heart rate
• Precordial or esophagel stethoscope
• Temp

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Perioperative monitoring

• Pulse oximeters
• End tidal carbon dioxide (ECO2)
• Peripheral nerve stimulator if muscle relaxants
  are used
• Foly catheter
• For selected patint with a potential risk of
  venous air embolism a doppler probe may placed
  over the right atrium
• Invasive arterial pressure mesurements, central
  venous pressure
• Pulmonary artery catheter and continous mixed
  venous oxygen saturation measured

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Perioperative monitoring

• For special conditions other monitors as
  transesophageal echocardiography
• Electroencephalogram
• Cereral or neurological may be used

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Inhalational Anesthetic Agents

• Inhalational anesthesia refers to the delivery of
  gases or vapors from the respiratory system to
  produce anesthesia
• Pharmacokinetics--uptake, distribution, and
  elimination from the body
• Pharmacodyamics-- MAC value

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Regional Anesthesia

• Defined as a reversible loss of sensation in a
  specific area of the body
• Spinal anesthesia
• Epidural anesthesia
• IV Regional Blocks
• Peripheral Nerve Blocks

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Spinal Anesthesia

• A local anesthetic agent (lidocaine, tetracaine
  or bupivacaine) is injected into the subarachnoid
  space
• Spinal anesthesia is also known as a subarachnoid
  block
• Blocks sensory and motor nerves, producing loss
  of sensation and temporary paralysis

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Possible Complications of Spinal Anesthesia

• Hypotension
• Post-dural puncture headache (Spinal headache)
  caused by leakage of spinal fluid through the
  puncture hole in the dura-can be treated by blood
  patch
• High Spinal- can cause temporary paralysis of
  respiratory muscles. Patient will need ventilator
  support until block wears off

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Epidural Anesthesia

• Local anesthetic agent is injected through an
  intervertebral space into the epidural space.
• May be administered as a one-time dose, or as a
  continuous epidural, with a catheter inserted
  into the epidural space to administer anesthetic
  drug

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Complications of Epidural Anesthesia

• Hypotension
• Inadvertent dural puncture
• Inadvertent injection of anesthetic into the
  subarachnoid space

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IV Regional Blocks

• Also known as a Bier Block
• Used on surgery of the upper extremities
• Patient must have an IV inserted in the operative
  extremity

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IV Regional Block

• After a pneumatic tourniquet is applied to
  extremity, Lidocaine is injected through the IV.
• Anesthesia lasts until the tourniquet is deflated
  at the end of the case.

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IV Regional Blocks

• IMPORTANT- to prevent an overdose of lidocaine it
  is important not to deflate the tourniquet
  quickly at the end of the procedure.

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Peripheral Nerve Blocks

• Injection of local anesthetic around a peripheral
  nerve
• Can be used for anesthesia during surgery or for
  post-op pain relief
• Examples ankle block for foot surgery,
  supraclavicular block for post-op pain control
  after shoulder surgery

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Monitored Anesthesia Care (MAC)

• Generally used for short, minor procedures done
  under local anesthesia
• Anesthesia provider monitors the patient and may
  provide supplemental IV sedation if indicated

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Conscious Sedation

• Used for short, minor procedures
• Used in the OR and outlying areas
• (ER, GI Lab, etc)
• Patient is monitored by a nurse and receives
  sedation sufficient to cause a depressed level of
  consciousness, but not enough to interfere with
  patients ability to maintain their airway

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Inhalation Anesthetics

• Nitrous Oxide- can cause expansion of other
  gases- use of N20 contraindicated in patients
  who have had medical gas instilled in their
  eye(s) during retinal detachment repair surgery

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Inhalation Anesthetics

• Cause cerebrovascular dilation and increased
  cerebral blood flow
• Cause systemic vasodilation and decreased blood
  pressure
• Post-op NV
• All inhalation anesthetics, except N20, can
  trigger malignant hyperthermia in susceptible
  patients

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Intravenous Induction/Maintenance Agents

• Propofol (Diprivan)- pain/burning on injection,
  can cause bizarre dreams
• Pentothal (Sodium Thiopental)- can cause
  laryngospasm

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General Anesthesia

• During induction the room should be as quiet as
  possible
• The circulator should be available to assist
  anesthesia provider during induction emergence
• Never move/reposition an intubated patient
  without coordinating the move with anesthesia
  first

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General Anesthesia

• Laryngospasm may happen in a patient having a
  procedure with general anesthesia
• When laryngospasm occurs, it is usually during
  intubation or emergency
• Assist anesthesia provider as needed- call for
  anesthesia back-up if necessary

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Difficult Airway Cart

• Anesthesia maintains a Difficult Airway Cart
  containing equipment supplies for difficult
  intubations
• This cart is stored in one of the anesthesia
  supply rooms
• Page anesthesia tech if the cart is needed for
  your room

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Cricoid Pressure or Sellick Maneuver

• Used for patients at risk for aspiration during
  induction, due to a full stomach or other
  factors such as a history of reflux
• Pressure on the cricoid cartilage compresses the
  esophagus against the cervical vertebrae and
  prevents reflux

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Sellick Maneuver

• Cricoid pressure is maintained, as directed by
  anesthesia provider, until the ETT cuff is
  inflated

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Regional Anesthesia

• Circulator may need to assist anesthesia provider
  with positioning for spinal or epidural
  anesthesia.
• Patient usually is positioned laterally for
  placement of regional anesthesia, but may be
  positioned sitting upright.

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The Awake Patient

• Patients undergoing surgery with regional or
  local anesthesia, even if sedated, may be aware
  of conversation and activity in room
• Post sign on door to OR, Patient is Awake so
  that staff entering room will be aware that
  patient is conscious

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When Patient is Awake

• Limit any discussion of patients medical
  condition and prognosis
• Avoid discussion of other patients limit
  unnecessary conversation-- a sedated patient can
  easily misinterpret conversation they overhear