ANESTHESIA

ANESTHESIAMong Lam, CRNA

History Basic concepts Types of anesthesia Anesthesia machine

Objectives

CRNA: we never miss a beat!

Horace Wells and nitrous oxide William Thomas Green Morton and ether Ether Dome

History

Certified Registered Nurse Anesthetist (CRNA)

Anesthesiologist (MD) Anesthesia model or practice setting

History

Types of anesthesia Concepts Administration & Selection

Anesthesia

Definition: “Lack of Sensation” Describes a process that is used to alleviate

pain and suffering during a surgical procedure

Anesthesia

Achieved If All Of The Following Are Met: Hypnosis Anesthesia Amnesia Muscle Relaxation Optimal Positioning of Patient Homeostasis of Vital Functions

Optimal Anesthesia

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

Hypnosis

Lack of sensation Allows for “pain-free” surgery Ranges from topical, local, regional and

general (systemic) agents

Anesthesia

Lack of recall of surgical events Allows for more cooperative relaxed patient

Amnesia

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

Muscle Relaxation

Muscle Relaxation

Allows for surgical site exposure/access Allows for monitoring of the surgical patient Allows/provides physiological homeostasis

Patient Positioning

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

Homeostasis of Vital Functions

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

Methods of Administration

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.

American Society of Anesthesiologists (ASA)

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) with no functional

limitations

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) with functional limitations

Class 4- severe disease (s) present that are life-threatening (unstable angina, CHF, respiratory disease that is

debilitating, liver failure, kidney failure, myocardial infarction)

Class 5- Moribound patient who is not expected to survive with or without surgery

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

Patient safety Optimal results

Goal of Anesthesia

3 types:1. General Focus on altering state of consciousness, awareness and pain perception2. Nerve Conduction Blockade Focus on preventing sensory nerve

impulse transmission3. MAC (monitored anesthesia care)

Anesthetic Agents

Combined to deliver “Balanced Anesthesia” Inhalation agents Intravenous agents Less Common: Intramuscular agents Instillation

General Anesthesia

Amnesia Analgesia Anesthesia Muscle Relaxation Together provide “Balanced Anesthesia”

Components 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

Stages of General Anesthesia

1. Preinduction begins with premed administered and ends when anesthesia induction begins in OR

2. Induction from consciousness to unconsciousness

3. 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

Phases of Anesthesia

GA vs MAC GA vs block Types of surgery and length Age and mental status

Advantages verses Disadvantages

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 Anesthesia

5. 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

General Anesthesia

Includes: 1. Topical anesthesia2. Local anesthesia3. Regional anesthesia Spinal (intrathecal) block Epidural block Caudal block Nerve plexus block

Nerve Conduction Blockade

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

Topical Anesthesia

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 Anesthetics

Combination of nerve conduction blockade on topical or local level with supplementation by the anesthesia provider with analgesics, sedative-hypnotics, or amnestics

Local Anesthesia with MAC

Injected along a major nerve tract Nerve Plexus Block or Field Block Bier Block Spinal Epidural Caudal Block

Regional Anesthetics

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)

Nerve Plexus 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

Bier Block

Bier 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

Spinal Block

Spinal 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

Epidural Block

Epidural 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

Caudal Block

Drager and Datex Ohmeda Purpose Basic components: breathing circuit,

ventilator, vaporizer, CO2 absorber, scavenging system

Anesthesia Machine

Anesthesia Machine

Anesthesia Machine

Malignant hyperthermia Recall CNS depression Long term effects? Many more

Complications

History Concepts Methods Machine

Summary

Questions?