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Anesthesia
Definition: “Lack of Sensation” Describes a process that is used to
alleviate pain and suffering during a surgical procedure
Optimal Anesthesia
Achieved If All Of The Following Are Met:
Hypnosis Anesthesia Amnesia Muscle Relaxation Optimal Positioning of Patient Homeostasis of Vital Functions
Hypnosis
Altered state of consciousness related to how the patient perceives his or her environment (surgical) and procedure (surgical)
Induce sleep Can be light to fully unconscious
Anesthesia
Lack of sensation Allows for “pain-free” surgery Ranges from topical, local, regional
and general (systemic) agents
Muscle Relaxation
Combined with inhalation (gases) agents to produce muscle relaxation to total paralysis
Allows for endotracheal intubation Facilitates exposure of tissues and
organs as muscles are in a relaxed state
Patient Positioning
Allows for surgical site exposure/access
Allows for monitoring of the surgical patient
Allows/provides physiological homeostasis
Homeostasis of Vital Functions
Maintenance of the patient’s physiological status until surgical intervention is complete
Most dangerous part of surgery is anesthesia
Are inducing a state close to death without crossing that line
Methods of Administration Determining the Right Anesthetic Patient’s age, weight, and build Emotional, psychological and physical needs Type of operation and duration of operation Lab and X-ray findings Pre-existing illnesses or diseases Medications on Allergies History of drug or alcohol abuse Time since last ingested food, particularly with
emergencies
American Society of Anesthesiologists (ASA)
Based on the evaluation/assessment done preoperatively, the patient is assigned a Class # 1 through #6. This determines what kind of risk is involved for the patient for the surgical procedure about to be performed.
Class 1- Patient has no previous/current physical or mental medical history
Class 2- Mild to moderate disease present (controlled HTN, asthma,
controlled diabetes, mildly obese, anemic, tobacco use) that does not
interfere with ADLs Age less than 1 year or greater than 70 years old
Class 3- severe disease present (controlled angina, has had a
myocardial infarction, HTN that is not controlled, respiratory disease that is causing difficulties presently, greatly obese) that interfere with ADLs
Class 4- severe disease (s) present that are life-threatening (unstable angina, CHF, respiratory disease that is
debilitating, liver failure, kidney failure,
myocardial infarction in progress or in the last 24 hours)
Class 5- Has little chance of survival, but is operated on as a last ditch effort or at the request of family members
Anesthetic Agents 2 types:1. General Focus on altering state of consciousness, awareness and pain perception2. Nerve Conduction Blockade Focus on preventing sensory nerve
impulse transmission
General Anesthesia
Combined to deliver “Balanced Anesthesia”
Inhalation agents Intravenous agents Less Common: Intramuscular agents Instillation
Components of General Anesthesia
Amnesia Analgesia Anesthesia Muscle Relaxation Together provide “Balanced
Anesthesia”
Stages of General Anesthesia I. Amnesia stage is lightest stage that begins with
administration of agent ends with loss of consciousness Good stage for MAC II. Excitement or Delirium stage from loss of consciousness to
loss of eyelid reflex and regular breathing Patient movements are uninhibited Might see vomiting, laryngospasm, hypertension,
tachycardia Rarely seen except in children due to drugs that are
available now to carry patients straight to stage IIIIII. Surgical anesthesia stage from regular breathing and loss of
eyelid reflex to cessation of breathing Patient unresponsive and hearing is last to go IV. Overdose stage dilated nonreactive pupils, cessation of
breathing, hypotension can quickly lead to circulatory arrest if uncorrected
Autonomic response is totally blocked to all stimuli
Phases of Anesthesia1. Preinduction begins with premed administered
and ends when anesthesia induction begins in OR 2. Induction from consciousness to
unconsciousness3. Maintenance surgery takes place during this
requires maintenance of physiological function by anesthetist
4. Emergence as surgery is completed (start to wake up), restoration of gag reflex, extubation
5. Recovery time during when patient returns to full consciousness begins in OR and carries into stay in PACU and beginning healing stages
General Anesthesia
Inhalation Agents: Nitrous Oxide (N²O) Ethrane (Enflurane) Forane (Isoflurane) Halothane (Fluothane) Sevoflurane (Sevoflurane) Suprane (Desflurane)
General Anesthesia
Intravenous Agents:1. Barbiturates Short acting Anesthesia Not analgesic Pentothal (thiopental) Brevital (Methohexital)
General Anesthesia
2. Benzodiazepines Sedative and amnesiac effects Versed (Midazolam) Valium (Diazepam) Ativan (Lorazepam)
General Anesthesia
3. Individual Agent Propofol (Diprivan) Sedative/Hypnotic Anesthetic Amnesiac No Analgesia No Muscle Relaxation
General Anesthesia
4. Narcotics Maintenance of general anesthesia Anesthetic Sublimaze (Fentanyl) Alfenta (Alfentanil) Sufenta (Sufentanil) Morphine (Morphine Sulfate)
General Anesthesia5. Muscle Relaxants (neuromuscular blocking
agents) To receive endotracheal intubation, patient
must be paralyzed or have relaxed muscles a. Depolarizing Agents: Initiate contractions called fasciculation example: Succinylcholine (Anectine) b. Nondepolarizing Agents: Prevent contractions examples: Curare, Pavulon, Norcuron
Nerve Conduction Blockade
Includes: 1. Topical anesthesia2. Local anesthesia3. Regional anesthesia Spinal (intrathecal) block Epidural block Caudal block Nerve plexus block
Topical Anesthesia Used on mucous membranes: upper
aerodigestive tract, urethra, rectum, and skin
Cryoanesthesia reduces nerve conduction by localized freezing with a probe connected to a cryoprecipitate unit that uses nitrogen
Cryoanesthesia can also be performed with ice
Lidocaine jelly Cocaine (topical only!) Most common use:
sinus surgery
Local Anesthetics Immediate surgical site anesthesia Affects small circumscribed area Can be injected or applied topically Lidocaine (Xylocaine) Bupivicaine (Marcaine, Sensorcaine) Procaine (Novocain) Tetracaine (Pontocaine) Mepivacaine (Carbocaine) Hyaluronidase (Wydase) facilitator/enhancer of above
medications’ effects Epinephrine (Adrenalin) additive to above for
vasoconstrictive properties
Local Anesthesia with MAC
Combination of nerve conduction blockade on topical or local level with supplementation by the anesthesia provider with analgesics, sedative-hypnotics, or amnestics
Regional Anesthetics
Injected along a major nerve tract
Nerve Plexus Block or Field Block Bier Block Spinal Epidural Caudal Block
Nerve Plexus Block
Anesthetic injected into major nerve plexus or the base of a structure
Result is anesthesia of tissue innervated by that plexus
Used in dental and extremities Examples: axillary, wrist, ankle,
cervical plexus (CAE)
Bier Block Anesthetic injected to an extremity into a vein
below the level of a tourniquet For arm/wrist/hand surgery that will last less
than 1 hour Blood exsanguinated from extremity with an
esmark, tourniquet is inflated, anesthetic given Tourniquet prevents anesthetic agent from
circulating above it Tourniquet will be released slowly to allow for
gradual circulation of the agent to prevent cardiovascular or CNS effects
Spinal Block Injected into CSF in the subarachnoid
space between L-3 and L-5 vertebrae For lower body procedures Onset 3-5 minutes Duration 1 ½ hours Tetracaine most common agent used Lidocaine and Procaine others used Epinephrine can prolong effect Never put patient in Trendelenburg
position with spinal anesthesia
Spinal Block
Disadvantages: Hypotension Nausea and vomiting One time dose means cannot
adjust Temporary or permanent paralysis
Spinal Block
Advantages: Conscious patient No respiratory irritation Bowel contraction enhances
abdominal visibility Muscle relaxant effects allow easy
abdominal wall retraction
Epidural Block Injected outside of the dura in the
epidural space that contains the fatty tissue
Injected T-4 vertebral area and down Lower limb & perineal surgeries and
obstetrics Thoracic surgeries will be placed for
post-op pain management Can be single dose or a catheter can be
inserted to allow for redosing
Caudal Block
Type of Epidural being replaced by the Epidural Block
Only difference is placement in the epidural space of the sacral canal
Primarily seen with mothers in labor