Transcript Basic Principles of Anesthesiology

Department of Anesthesiology and Pain Control
Basic Principles of
Anesthesiology
Before the Advent of Anesthesia
Patients
felt
like
condemned
criminals
awaiting
execution,
and if they
survived the
experience,
the memory
of it haunted
them for the
rest of their
lives

Dire emergencies
Repairing wounds, setting compound
fractures, amputating limbs
Mortality 30-50%
Shock from pain, bleeding, infection
Surgeons had the lowest prestige
of all medical practitioners
Before the Advent of Anesthesia
“Suffering
so great
as I underwent
cannot be expressed
in words… The
particular pangs are
now forgotten; but
the blank whirlwind
of emotion, the
horror of great
darkness and the
sense of desertion by
God and man… I
can never forget,
however gladly I
would do so.”
Before the Advent of Anesthesia
“I attended on two
occasions the
operating theatre
and saw two very
bad operations,
one on a child,
but I rushed away
before they were
completed. Nor
did I ever attend
again, for hardly
any inducement
would have been
strong enough to
make me do so.”
Charles Darwin
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Speed was the most valued clinical skill
Dexterity, next
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Little opportunity for careful dissection or
improvements in technique
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Showmanship
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Amputation and lithotomy were done within 3
mins
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Hypnosis
Opium
Alcohol
Exposure to cold
Compression of peripheral nerves
Constriction of carotid arteries
Blow to the jaw
Milestones

March 30, 1842
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Crawford Long
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Ether for
excision of neck
tumor
Milestones
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1844
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Horace Wells
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Nitrous oxide for
dental procedure
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Massachusetts
General Hospital
Turning Point
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October 16, 1846
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William Morton
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Ether for excision
of vascular neck
mass
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Massachusetts
General Hospital
Father of Anesthesiology
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John Snow
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Devised a scholarly, scientific method to
investigate the clinical properties and
pharmacology of ether, chloroform, and other
anesthetic agents
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Improved apparatus for administering ether,
mastered clinical techniques of anesthetizing
patients
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Brought anesthesia into public awareness
First Anesthesiologists, UK
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John Snow, Joseph Clover, Sir Frederick
Hewitt
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A physician dedicated specifically to the
administration of anesthesia was appropriate
and necessary
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Created a standard of excellence, fostered
professionalism, formed anesthesia societies, and
published papers on anesthesia
First Anesthesiologists, US

Arthur Guedel, John
Lundy, Ralph Waters
– Anesthesiology training
program
– Long Island Society of
Anesthetists, 1905
– New York Society of
Anesthetists, 1911
– American Society of
Anesthetists, 1935
– American Society of
Anesthesiologists, 1945
Overview
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Preoperative Evaluation
Principles of General Anesthesia
Complications of General Anesthesia
Principles of Regional Anesthesia
(separate lecture: preceptorial
session)
Recovery from Anesthesia
Preoperative
Evaluation
Goals
1.
2.
3.
4.
Obtain medical information to plan
the anesthesia care
Assess risk factors
Obtain informed consent
Provide preoperative education to
patient and family (NPO and
medication instructions)
5.
6.
7.
Acquaint patient on the available
anesthetic techniques; right to
choose
Provide px with clear expectations
for anesthetic care and
postoperative course
Discuss pain control plans
Review of Medical History
Age, conceptual age in premature
babies
2. Medications including herbal
supplements
3. Allergies and their specific reaction
4. Cigarette, alcohol, and drug history
1.
Past surgeries, anesthetic techniques,
and complications encountered
6. History of surgical/ anesthetic
complications in other family members
7. Birth and developmental hx in pediatric
px
8. OB hx, LMP (reproductive age)
5.
9. Medical problems and degree of
control
10. Exercise tolerance
11. Hx of airway problems: stridor,
snoring, loose teeth, TMJ
disease,
previous hx of difficult
airway
Co-morbidities
Ischemic Heart Disease: severity,
progression, functional limitations,
medications
1.
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MI death in px w/o IHD = 1%
MI death in px w/ IHD = 3%
MI death for peripheral vascular surgery =
29%
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Other risk factors: hypercholesterolemia,
hyperlipidemia, smoking, DM, HPN, age, obesity,
sedentary lifestyle
Stress: during induction (intubation), intraop
hemodynamic lability, extubation, postop
pain
Pulmonary disease: exacerbation of
symptoms, medications
2.
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Higher morbidity: upper abdominal and
thoracic surgeries
Other considerations:
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Intubation - irritation of the airway; increased
airway resistance
Supine position - hypoxia
High regional anesthesia - inadequate
ventilation
Hydration
Renal disease
3.
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Acute tubular necrosis: most common
cause of acute renal failure periop
Exacerbation of pre-existing renal
disease:
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Decreased cardiac output
Altered autonomic nervous system activity
Neuroendocrine changes
Positive pressure ventilation
 Hyperventilation = shift of oxyhemoglobin curve
 Hypoventilation = acidosis = dangerous inc serum
K
Hepatobiliary disease
4.
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Important: maintenance of adequate
hepatic blood flow, choice of anesthetic
drugs, adequate intravascular volume
Metabolic and endocrine disease
5.
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Thorough understanding of the
pathophysiology of the endocrine
problem
Tailor the anesthetic technique and
anesthetic drugs to minimize
complications
Readiness to manage each complication
CNS disease
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Understanding of ICP, CBF, CMRO2
interrelationship
Effects of anesthetic drugs, fluids,
maneuvers, positioning with cerebral
dynamics
Control hemodynamics, smooth induction
and emergence, pain control
Review of Systems
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Systematic ROS to pick up signs or
symptoms of other problems
Physical Examination
Verify:
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height & weight, BMI
vital signs
heart & lungs
skin condition (turgor, jaundice, pallor)
landmarks for regional technique
neurologic function
vascular access
extremities
airway evaluation
Airway Evaluation
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Mallampati classification (ability to view
posterior pharynx)
Thyro-mental distance
Mouth opening
Patency of both nares
Dentition
Mask fit (facial anatomy, beard)
Range of motion of the neck (BellhouseDore)
Obesity
Mallampati Classification
The px is asked to open the mouth and
protrude tongue maximally while in the
sitting position
Class 1
Faucial pillars, soft
palate, uvula seen
Class 2
Uvula masked by
tongue base
Only soft palate
visualized
Class 3
Class 4
Only hard palate
Thyromental distance
Bellhouse Dore
maximal flexion and extension of the neck will identify
limitations that might prevent optimal alignment of the
OPL axes.
*** Normal atlanto-occipital joint: 35 degrees of
extension
Other Methods of Airway
Evaluation
Combining the different
airway evaluation
increases the
specificity and sensitivity
of their predictive value
1.
2.
3.
5.
Body habitus
Mouth opening
(interdental
distance):>3 cm
State of dentition,
prominence of upper
incisors, ability to
protrude lower jaw
beyond upper incisors
Mandibular length: >9
cm normal
ASA Classification & Mortality Rates
Class 1: normal healthy patient
Class 2: mild to moderate systemic disease
Class 3: severe systemic that limits activity but
not incapacitating
Class 4: constant threat to life
Class 5: moribund px not expected to survive
24 h with or without surgery
Class 6: A brain dead patient whose organs are
being harvested
“E” refers to emergency situation; risks are doubled
0.06 %-0.1 %
0.27 %-0.4 %
1.8%-4.3%
7.8%-23%
9.4%-51%
Informed Consent

Include:
 Primary anesthetic plan
 Back up anesthetic plan
 Advantages and possible
complications
 Death
Preoperative Instructions
1. Fasting
No solid food 8 h before scheduled surgery
Adults & Children (>3 mos) clear liquids 3 h
Infants (< 3mos) clear liquids 2 h
**gastric emptying may vary in obese, pregnant,
post-trauma or obstructed patients, or those
with hiatal hernia, DM
2. Current medications
may be continued up to the day of surgery
3. Preoperative medications
Goals:
a. allay anxiety: benzodiazepines
b. reduce gastric acidity & residual volume:
Acid pump inhibitor, H2 blocker,
Metoclopramide
c. antisialogogue:
Atropine, Glycopyrrolate,
Scopolamine
d. minimize nausea & vomiting
e. amnesia, sedation, analgesia
f. reduce anesthetic requirement
g. reduce vagal activity
h. decrease histamine activity
Anesthetic Techniques
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General Anesthesia
Monitored anesthesia care
Regional Anesthesia
 Centralneuraxis anethesia
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Spinal anesthesia
Epidural Anesthesia
Combined Epidural and Spinal Anesthesia
 Major peripheral nerve blocks
 Local infiltration blocks
Principles of
General
Anesthesia
Goals of GA
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Unconsciousness and amnesia
Analgesia
Muscle relaxation
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controlled state of depressed
consciousness or
unconsciousness produced by a
pharmacologic method or nonpharmacologic method
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accompanied by:
partial or complete loss of protective reflexes
inability to maintain an airway
inability respond to physical or verbal stimulus
Indications
1.
2.
3.
4.
Head and neck operations
Thoracic operations
Abdominal operations
Limb operations where regional
techniques are contraindicated
Advantages of GA
1.
2.
3.
4.
5.
Easily titratable
Rapid onset
Controlled duration of action
Rapid recovery
Secure airway
Complications
Drug-related cardiovascular
depression
1.
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Hypotension
Bradycardia
Decreased organ perfusion
Myocardial depression
Cardiac arrythmias
Cardiac arrest
Drug-related respiratory depression
2.
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Loss of protective reflexes
Central depression of the respiratory center
Respiratory muscle relaxation/ paralysis
Drug-related gastrointestinal and urinary
depression
3.
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Ileus
Loss of sphincteric tones
Decrease sphlancnic blood supply if BP is
low
Drug-related neurologic
depression
3.
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Inhalational anesthetics: decreased
CMRO2, vasodilatation of cerebral
blood vessels = +/- increase in ICP
Intravenous drugs:  CMRO2 and
CBF
4.
Complications associated with the
technique:
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aspiration
trauma during intubation
laryngospasm
difficult airway
airway obstruction
corneal abrasion
nerve palsies
Intravenous Agents
Unconsciousness and Amnesia
1.
Barbiturates (Thiopental, Thiamylal,
Methohexital)
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2.
Rapid onset, short action
Inhibit excitatory synaptic transmission thru GABA
receptor effects
Anticonvulsants, cerebral protectant
Propofol
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GABA receptor effects
Rapid recovery
Benzodiazepines
3.
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Anxiolytic, amnestic
Diazepam, Lorazepam, Midazolam
Inhibit synaptic transmission at the GABA
receptor
Etomidate
4.
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Imidazole derivative
Acts on the GABA receptor
Produce the least cardiovascular depression
Ketamine
5.
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Produce analgesia and amnesia
Acts on the NMDA receptor; no action on GABA
Dissociative anesthesia
Delirium and hallucinations
Analgesia Drugs
1.
Opioid analgesics
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Morphine, Codeine, Meperidine, Fentanyl
Act on - recetors in the brain and SC
Side-effects: euphoria, sedation,
constipation, respiratory depression
Naloxone, Naltrexone: antagonists
Non-opioid analgesics
2.
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NSAIDs
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COX 1 & COX 2 non-selective
Selective COX 2 inhibitors
Neuromuscular Blocking Drugs
 Produce skeletal muscle paralysis thru
blockade of the neuromuscular junction
 Ensure patient immobility intraop
 Should not be used alone (aware, in
pain, unable to move)
– Depolarizing muscle relaxants: bind to 2
alpha sub units of acetylcholine receptors
causing depolarization then relaxation
– Non-depolarizing muscle relaxants: bind to
1 alpha subunit of the receptor blocking
Ach from binding
Agent
Duration
Depolarizing NMB
Succinylcholine
5-8 min
Non-depolarizing
Mivacurium
Atracurium
Vecuronium
Rocuronium
Pancurium
< 1h(15-20m)
< 1h(20-30m)
<1h(30-40m)
<1h
> 1h
Metabolism
Pseudocholinesterase
Plasma cholinesterase
Hoffmann elimination
Liver & kidneys
Unchanged
Kidneys
Side-effects
serum K,
fasciculation aches,
IOP & intragastric
pressure
Histamine
release
Intermediate onset
Tachycardia large
doses
Tachycardia; long
duration
Inhalational Agents
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Provide unconsciousness &
amnesia, analgesia, muscle
relaxation
– dose dependent which may likely
cause unacceptable side-effects
– use of adjuncts: opioids, NMB
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MAC: concentration of an inhaled
anesthetic that prevents movement
to a painful stimulus in 50% of
patients
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Potency and speed of induction ≈ lipid
solubility of the gas
Agent
MAC %
Advantages
Disadvantages
N2O
105
Analgesia
Expansion of air in
closed space
Halothane
0.75
Inexpensive; pleasant
smell
Arrhythmia;
Hepatitis
Enflurane
1.68
Muscle relaxation
Odor; seizures
Isoflurane
1.15
Same as enflurane
Odor
Desflurane
6
Rapid induction &
recovery
Expensive; Odor
Sevoflurane
1.71
Mask induction; rapid
onset & recovery
Expensive
Intraoperative Management
Induction
1.
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Preoxygenation
IV drugs/ gas are administered = unconsciousness
Mask ventilation
Muscle relaxants = facilitate intubation
Mask ventilation
Rapid sequence induction: high risk for aspiration
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Same sequence except for mask ventilation in between
Sellick’s maneuver: application of downward pressure on
the cricoid cartilage to occlude the esophagus
2.
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Airway management
Taken up during preceptorial
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
LMA / ILMA
3.
Fluid therapy
1) Crystalloids:
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Electrolyte containing with or without dextrose
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Normal saline 0.9% NaCl or D5 NSS
PLR or D5 LR
D5 0.3% NaCl
D5 NM
2) Colloids:
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Contain dextrose or protein suspended in electrolyte
solution
High molecular weights
 HES
 Gelatin
 Albumin
3) Blood
Recovery from
Anesthesia
PACU
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Continued intensive monitoring of px
until they can safely be discharged
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Early recognition of complications
that may necessitate re-operation
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Prompt recognition and management
of medical disturbances
Pain as the 5th Vital Sign
“We need to train doctors and nurses to treat
pain as a vital sign. Quality care means that
pain is measured and treated”
James Campbell, MD
Presidential Address, American Pain Society
November 11, 1996
….as condition of licensure … include pain as an
item to be assessed at the same time as vital
signs are taken. … pain assessment shall be
noted in the patient’s chart (Pain Assessment
Bill)
Pain as the 5th Vital Sign
Modalities of Pain control
1.
Round-the-clock parenteral drugs
 Opioids: Nalbuphine, Meperidine, Fentanyl,
Morphine
 Tramadol
 NSAIDS
2. Patient controlled analgesia; continuous IV
infusion
3. Continuous epidural analgesia
4. Regional blocks
5. Oral analgesics, rectal analgesics
Visual Analogue Scale (VAS):
0
No pain
10
Worst imaginable
pain
Numeric Rating Scale
0 1 2
No pain
3
4
5
6
7
8 9 10
Worst pain
The Whaley & Wong Faces Rating Scale
Malignant Hyperthermia (MH)
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Life-threatening, genetic predisposition
that develops during or after general
anesthesia with exposure to trigger agents
Triggering agents
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All volatile gas
Succinylcholine
Clinical presentation:
 hypermetabolic state (high temperature, tachycardia,
high EtCO2, acidosis)
 muscle rigidity
 rhabdomyolysis, arrythmias, hyperkalemia, cardiac
arrest
Management of MH
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Supportive
Dantrolene
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