ANESTHESIA PART I

Anesthesia

Types of Concepts Administration & Selection

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

Amnesia

Lack of recall of surgical events Allows for more cooperative

relaxed patient

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

Class 6- Is brain dead/life support is

being provided This is an organ harvest or procurement

(E) Emergency Modifier- an E is added

to the Class # in cases of emergency

surgery

Goal of Anesthesia

Patient safety Optimal results

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

Advantages verses Disadvantages

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

Summary

Anesthesia Types Anesthesia Administration &

Selection