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?