MT115
MT TERM
SUM
LECTURE \ CESAR
UNIT 10: ANESTHESIA
I
GENERAL ANESTHETICS: INTRAVENOUS
OUTLINE
Anesthesia
A
General Anesthesia
B
Local Anesthesia
Barbiturates
Benzodiazepines
Dexmedetomidine
Etomidate
Ketamine
Opioids
Propofol
OBJECTIVES
At the end of the unit, the student is able to:
•
Identify accurately the drug and the adverse effects and
toxicities of commonly used medications.
Anesthesia à is a medical treatment that prevents
patients from feeling pain during surgery (National
Institute of General Medical Sciences, 2020).
Local anesthesia à is an anesthetic agent given to
temporarily stop the sense of pain in a particular area of
the body.
Regional anesthesia à is used to numb only the portion
of the body that will undergo the surgery.
General anesthesia à is an anesthetic used to induce
unconsciousness during surgery (John Hopkins
Medicine, 2020).
In other books, local and regional anesthesia are grouped
into local anesthetic agents.
•
•
•
•
•
STAGES OF ANESTHESIA
1
2
3
Inhaled gases are primarily used for maintenance of
anesthesia after administration of an IV agent.
Volatile anesthetics delivered to the patient are absorbed via
the lungs into the systemic circulation causing dosedependent CNS depression.
Induction
Maintenance
Recovery
•
INDUCTION
•
DIPRIVAN
INHALED GENERAL ANESTHESIA
•
ANESTHESIA
PRECEDEX
AMIDATE
KETALAR
Induction is the time from administration of a potent
anesthetic to development of effective anesthesia.
•
No specific receptor has been identified as the locus of
general anesthetic action.
The fact that chemically unrelated compounds produce
anesthesia argues against the existence of a single
receptor.
HALOTHANE
•
•
MAINTENANCE
•
•
•
After administering the anesthetic, vital signs and
response to stimuli are monitored continuously to balance
the amount of drug inhaled and/or infused with the depth
of anesthesia.
Maintenance provides sustained anesthesia.
We need to continuously infuse or let the patient inhale
the anesthetic agent so that he/she will not wake up in the
middle of the procedure or feel pain.
•
ISOFLURANE
•
Postoperatively, the anesthetic admixture is withdrawn,
and the patient is monitored for return of consciousness.
Recovery à is essentially the reverse of induction and
depends on how fast the anesthetic diffuses from the
brain. It is the final stage.
•
•
•
GENERAL ANESTHETICS: INHALED
•
SUPRANE
FLUOTHANE
FORANE
NITROUS OXIDE
ULTANE
Desflurane provides very rapid onset and recovery due
to low blood solubility.
This makes it a popular anesthetic for outpatient
procedures.
SEVOFLURANE
GENERAL ANESTHESIA
Desflurane
Halothane
Isoflurane
Nitrous oxide
Sevoflurane
This agent undergoes little metabolism and is, therefore,
not toxic to the liver or kidney.
DESFLURANE
RECOVERY
•
•
Halothane à is the prototype to which newer inhalation
anesthetics are compared.
When halothane was introduced, its rapid induction and
quick recovery made it an anesthetic of choice.
Due to adverse effects and the availability of other
anesthetics with fewer complications, halothane has
been replaced in most countries.
Sevoflurane has low pungency, allowing rapid induction
without irritating the airways.
This makes it suitable for inhalation induction in pediatric
patients.
NITROUS OXIDE
•
Nitrous oxide (“laughing gas”) is a non-irritating potent
analgesic (removes pain) but a weak general anesthetic.
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TRANS: Anesthesia
•
It is commonly known as laughing gas due to the
exhilarating effects of inhaling it.
OPIOID
•
•
•
INTRAVENOUS GENERAL ANESTHESIA
•
•
•
IV anesthetics cause rapid induction.
Anesthesia may then be maintained with an inhalation
agent.
IV anesthetics may be used as sole agents for short
procedures or administered as infusions to help maintain
anesthesia during longer cases.
PROPOFOL
•
Propofol à is an IV sedative/hypnotic used for induction
and/or maintenance of anesthesia.
Because of their analgesic property, opioids are
commonly combined with other anesthetics.
The most commonly used opioids are fentanyl, sufentanil,
and remifentanil, because they induce analgesia more
rapidly than morphine.
Morphine à usually given PO (post-operative)
ETOMIDATE
•
Etomidate à is a hypnotic agent used to induce
anesthesia, but it lacks analgesic activity.
KETAMINE
•
•
Ketamine, a short-acting, nonbarbiturate anesthetic,
induces a dissociated state in which the patient is
unconscious (but may appear to be awake) and does not
feel pain.
This dissociative anesthesia provides sedation, amnesia,
and immobility.
DEXMEDETOMIDINE
•
Dexmedetomidine à is a sedative used in intensive
care settings and surgery.
•
Local anesthetics block nerve conduction of sensory
impulses and, in higher concentration, motor impulses
from the periphery to the CNS.
Unlike general anesthetics, local anesthetics have
specific receptors.
Na+ ions channels are blocked to prevent the transient
increase in permeability of the nerve membrane to Na+
that is required for an action potential.
o Remember that human action potential happens
when sodium rushes into the nerve.
When propagation of action potentials is prevented,
sensation cannot be transmitted from the source of
stimulation to the brain.
BARBITURATES
•
•
It is a potent anesthetic but a weak analgesic.
Barbiturates
require
supplementary
analgesic
administration during anesthesia.
Amobarbital
Pentobarbital
Phenobarbital
Secobarbital
Thiopental
BARBITURATES
AMYTAL
NEMBUTAL
LUMINAL SODIUM
SECONAL
PENTOTHAL
The benzodiazepines are used in conjunction with
anesthetics for sedation (so that the patient will be asleep
or unconscious during the procedure).
Alprazolam
Chlordiazepoxide
Clonazepam
Clorazepate
Diazepam
Estazolam
Flurazepam
Lorazepam
Midazolam
Oxazepam
Quazepam
Temazepam
Triazolam
•
•
•
BENZODIAZEPINES
•
LOCAL ANESTHESIA
BENZODIAZEPINES
XANAX
LIBRIUM
KLONOPIN
TRANXENE
VALIUM, DIASTAT
DALMANE
ATIVAN
VERSED
DORAL
RESTORIL
HALCION
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TRANS: Anesthesia
SUMMARY: DRUGS USED FOR LOCAL ANESTHESIA
SUBCLASS,
DRUG
AMIDES
•
Lidocaine
•
Bupivacaine
MECHANISM OF
ACTION
•
•
Blockade
of
sodium channels
Same
lidocaine
as
CLINICAL
APPLICATIONS
EFFECTS
•
•
Slows,
then
blocks, action
potential
propagation
Same
lidocaine
as
•
•
•
PHARMACOKINETICS,
TOXICITIES
Short-duration
procedures
topical
(mucosal),
intravenous,
infiltration,
spinal,
epidural, minor and
major
peripheral
blocks
•
Longer-duration
procedures (but not
used
topically
or
intravenously)
•
•
•
•
Prilocaine, mepivacaine: Like lidocaine (but also risk of methemoglobinemia with prilocaine)
Articaine: popular dental anesthetic
Ropivacaine, levobupivacaine: Like bupivacaine
ESTERS
•
Chloroprocaine •
Like lidocaine
•
Like lidocaine
•
Very short procedures
(not generally used
topically
or
intravenously)
•
•
•
Parenteral
(eg,
peripheral block, but
varies
significantly
based on specific site)
Duration 1-2 h
2-4 h with epinephrine
Toxicity:
Central
nervous system (CNS)
excitation (high-volume
blocks)
and
local
neurotoxicity
Parenteral
Duration 3-6 h
Toxicity: CNS excitation
Cardiovascular
collapse (high-volume
blocks)
•
•
•
•
Cocaine
•
•
Same as above
Also
has
sympathomimetic
effects
•
Same as above
•
Procedures requiring
high surface activity
and vasoconstriction
•
•
•
•
•
•
•
Parenteral
Duration 30-60 min
60-90
min
with
epinephrine
Toxicity: Like lidocaine
Topical or parenteral
Duration 1-2 h
Toxicity:
CNS
excitation, convulsions,
cardiac
arrhythmias,
hypertension, stroke
Procaine: Like chloroprocaine (but not used epidurally)
Tetracaine: Used primarily for spinal anesthesia; duration 2-3 h
Benzocaine: used exclusively for topical anesthesia
Note: Read the Subclass, Mechanism of Action and Clinical Applications only
•
•
•
REFERENCE
Lecture and PPT of Jan Harmony A. Cesar, MSPh, MATh,
Assistant Professor IV, OIC Dean
Whallen, K. (2015). Lippincott Illustrated review:
Pharmacology (6th ed.). Philadelphia: Wolters Kluwer.
Katzung B.G. (2018). Basic & Clinical Pharmacology (14th
ed.). New York: McGraw-Hill Education.
Michigan Pain Consultants. (2020). Nociceptive vs
neuropathic
pain.
Retrieved
from:
https://michiganpain.com/nociceptive-vs-neuropathicpain/.
National Institute of General Medical Sciences. (2020).
Anesthesia.
Retrieved
from:
https://www.nigms.nih.gov/education/factsheets/Pages/anesthesia.aspx.
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