Transcript effects - Dr. Roberta Dev Anand

INTRODUCTION TO
ANESTHESIA & PREANESTHETIC AGENTS
CHAPTERS 1 & 3
TERMINOLOGY OF ANESTHESIA
• _______________ may be defined as “loss of sensation”, but this
only describes one of its effects.
• It is used daily in most veterinary practices to provide sedation,
tranquilization, immobility, muscle relaxation, unconsciousness, and pain
control for a diverse range of indications including surgery, dentistry,
grooming, diagnostic imaging, wound care, and capture/transport of wild
animals
TERMINOLOGY OF ANESTHESIA
• __________________ refers to drug-induced CNS depression and
drowsiness that vary in intensity from light to deep.
• Patient can be aroused by noxious stimuli
• _______________________ is a drug-induced state of calm in which
the patient is reluctant to move and is aware of but unconcerned
about its surroundings.
• Often used interchangeable with sedation
TERMINOLOGY OF ANESTHESIA
• ________________ is a sleeplike state from which the patient can be
aroused with sufficient stimulation.
• _____________________ refers to a drug-induced sleep from which
the patient is not easily aroused and that is most often associated
with the administration of narcotics.
TERMINOLOGY OF ANESTHESIA
• __________________________________may be defined as a
reversible state of unconsciousness, immobility, muscle relaxation,
and loss of sensation throughout the entire body produced by
administration of one or more anesthetic agents.
• _______________________________ is a specific stage of general
anesthesia in which there is sufficient degree of analgesia(loss of sensitivity
to pain) and muscle relaxation to allow surgery to be performed without
patient pain or movement.
Fully conscious
Awake
Light sedation
Moderate sedation
Sedation
Deep sedation
Border between
Consciousness and
unconsciousness
Hypnosis
Narcosis
Light surgical anesthesia
Unconscious
Moderate surgical anesthesia
Deep surgical anesthesia
Anesthetic overdose
General
anesthesia
TERMINOLOGY OF ANESTHESIA
 __________________ anesthesia refers to loss of sensation in a small
area of the body produced by administration of a local anesthetic
agent in proximity to the area of interest.
 _________________ anesthesia is the loss of sensation of a localized
area produced by administration of a local anesthetic directly to a
body surface or to a wound.
 _________________ anesthesia refers to a loss of sensation in a
limited area (larger area than with local anesthetics)of the body
produced by administration of local anesthetic agent in proximity to
sensory nerves.
TERMINOLOGY OF ANESTHESIA
• ___________________ anesthesia refers to the practice of
administering multiple drugs concurrently in smaller quantities than
would be required if each were given alone.
• Maximizes benefits of each drug
• Minimizes adverse effects
• Allows anesthetist to produce CNS depression, immobilization, and pain
relief that is appropriate for the patient and the procedure.
PRE-ANESTHETIC AGENTS & ADJUNCTS
• ANESTHETIC AGENT: any drug used to induce a loss of sensation with
or without unconsciousness.
• _________________: a drug that is not a true anesthetic but that is
used during anesthesia to produce other desired effects such as
sedation, muscle relaxation, analgesia, reversal, neuromuscular
blockade, or parasympathetic blockade
• Ex: muscle relaxants, neuromuscular blockers, reversal agents
PRE-ANESTHETIC AGENTS &
ADJUNCTS
• CHOOSING THE APPROPRIATE AGENTS
• ____________________: most clinics will not have the option of choosing
from every drug on the market.
• ____________________: drugs are often chosen based on the veterinarian’s
familiarity
• ____________________: drugs that are appropriate for one procedure may
not be appropriate for another
• Some drugs are short-acting and would not be appropriate for long surgeries
• Some drugs may be appropriate for a spay but not a c-section
PRE-ANESTHETIC AGENTS
• ___________: It is ok to use a cheaper anesthetic as long as it is just as safe
as the more expensive one.
• ______________________________: in emergency situations, fast-acting
drugs may be necessary
• The anesthetic protocol, dose, and route are chosen by the
veterinarian
• Many clinics have a routine protocol, but is important to consider all
aspects of the patient’s minimum database
PRE-ANESTHETIC AGENTS
• Drugs that are administered to an animal prior to general anesthesia
• May be a single drug or combination of drugs
• Do not mix two or more drugs unless you have reliable evidence that it is safe to do so.
• REASONS TO ADMINISTER PRE-ANESTHETIC AGENTS
• _________________________________________
PRE-ANESTHETIC AGENTS
• REASONS TO ADMINISTER PRE-ANESTHETIC AGENTS
• _______________________________________________
• Ex: some anesthetic agents cause hypersalivation, we can use atropine or glycopyrrolate to
counteract this effect.
• ________________________________________________
• If the patient is already sedated, it takes less drug to bring them into the unconscious state.
This is a safer practice than using large amounts of drugs
• Using smaller amount of both pre-anesthetics and anesthetic agents in combination is known
as balanced anesthesia.
PRE-ANESTHETIC AGENTS
• REASONS TO GIVE PRE-ANESTHETIC AGENTS
• _______________________________: some pre-anesthetic agents last long
enough to be effective post-operatively
CLASSES OF PREANESTHETIC AGENTS
 ANTICHOLINERGICS
 TRANQUILIZERS and SEDATIVES
 Phenothiazines
 Benzodiazepines
 Alpha-2 agonists
 OPIOIDS




Agonists
Partial agonists
Agonist-antagonists
antagonists
ANTICHOLINERGICS
aka parasympatholytics
or sympathomimetics
ANESTHETIC & SURGICAL TECHNIQUES MAY
STIMULATE THE VAGUS NERVE
• The ______________ nerve provides parasympathetic innervation to
numerous target organ such as:
•
•
•
•
•
Heart
Lungs
GI tract (viscerovagal reflex)
Secretory glands
Iris(oculovagal reflex)
• The vagus nerve can stimulated by endotracheal intubation, GI
traction, or manipulation of the eye
ANTICHOLINERGICS
• Acetylcholine is the primary neurotransmitter in the PNS responsible
for parasympathetic effects (cholinergic effects)
Ach
Ach
ANTICHOLINERGICS
These drugs are given to counteract the effects caused by vagal
stimulation
EXAMPLES: Atropine, Glycopyrrolate
ANTICHOLINERGICS
Ach
Ach
ANTICHOLINERGICS ONLY AFFECT _________________RECEPTORS
ON THE TARGET ORGANS
WHAT EFFECT DO ANTICHOLINERGICS HAVE
ON THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
WHAT EFFECT DO ANTICHOLINERGICS HAVE
ON THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
WHAT EFFECT DO ANTICHOLINERGICS HAVE
ON THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
WHAT EFFECT DO ANTICHOLINERGICS HAVE
ON THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
WHAT EFFECT DO ANTICHOLINERGICS HAVE
ON THE VARIOUS BODY SYSTEMS?
WHAT EFFECT DO ANTICHOLINERGICS HAVE
ON THE VARIOUS BODY SYSTEMS?
WHAT EFFECT DO ANTICHOLINERGICS
HAVE ON THE VARIOUS BODY SYSTEMS?
ATROPINE vs. GLYCOPYRROLATE:
A COMPARISON
• Both drugs can be given SQ or IM (preanesthetic purposes) or IV
(emergency treatment of bradycardia/cardiac arrest)
• ______________ is generally preferred for emergencies due to the quicker onset of
action
• Onset of Action/Duration of Action
• Atropine IM: 5min, peak @ 10-20min, duration 60-90min
• Atropine IV: 1 min, peak @ 3-4 min, duration several minutes
• Glycopyrrolate IM: similar onset time to atropine, peak @ 30-45min, duration 2-3
hrs
ATROPINE vs GLYCOPYRROLATE:
A COMPARISON
• Glycopyrrolate causes less tachycardia
• ______________ is better at decreasing salivation
• TOXICITY
• With overdoses drowsiness, excitement, dry mouth, ataxia, muscle tremors,
dilated pupils, hyperthermia, and tachycardia may be seen
• REVERSED with PHYSOSTIGMINE
• Reversal is uncommon
• ANTICHOLINERGICS _____________CONTROLLED
TRANQUILIZERS and SEDATIVES
PHENOTHIAZINES
BENZODIAZEPINES
ALPHA-2 AGONISTS
GENERAL INFO ON
TRANQUILIZERS/SEDATIVES
 _________________ reduce anxiety, but may not decrease
awareness
 _________________ reduce mental activity and awareness and
induce sleepiness
These terms are often used interchangeably
 Patients that have received a tranquilizer/sedative may still be easily
aroused and could potentially get aggressive or injure themselves
http://www.youtube.com/watch?v=AkaGW
wTHD5g
PHENOTHIAZINES
ACEPROMAZINE
CHLORPROMAZINE
GENERAL INFO on PHENOTHIAZINES
• These drugs have no _____________ effects
• These drugs are not controlled
• These drugs do not have a ____________ agent
• Examples: Acepromazine, Chlorpromazine
WHAT ARE THE EFFECTS THAT PHENOTHIAZINES
HAVE ON THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
EFFECTS:
ADVERSE EFFECTS:
WHAT ARE THE EFFECTS THAT PHENOTHIAZINES
HAVE ON THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
EFFECTS:
ADVERSE EFFECTS:
OTHER EFFECTS & ADVERSE EFFECTS of
PHENOTHIAZINES:
 ANTIHISTAMINE EFFECT
 PENILE PROLAPSE
 DECREASED PCV
 Onset of action/duration of action
 15min after IM injection, peak@ 30-60 min
 Duration: 4-8 hrs( could be up to 48hrs)
THINGS TO CONSIDER WITH
PHENOTHIAZINES
• Sedative effects can be overridden if patient is stimulated to a sufficient
degree
• Use a max of 3mg in dogs and 1mg in cats
• Boxers and giant breed dogs by have increased sensitivity
• Terriers and cats are more resistant to its effects
• Chlorpromazine is used in veterinary medicine as an antiemetic, but not as
an anesthetic adjunct.
BENZODIAZEPINES
DIAZEPAM
MIDAZOLAM
ZOLAZEPAM
GENERAL INFO ON BENZODIAZEPINES
 Benzodiazepines depress the CNS by increasing activity of
endogenous ____________________________, an inhibitory
neurotransmitter in the brain.
 These drugs are ________________
 These drugs can be reversed
 ______________________ is the benzodiazepine antagonist. It is rarely
used due to the very low incidence of adverse effects and the high cost.
 These drugs provide no ______________
 These drugs have unreliable sedative effects & could induce
dysphoria, excitement, or ataxia in young, healthy animals, esp.
when given alone
 EXAMPLES: DIAZEPAM, MIDAZOLAM, ZOLAZEPAM
WHATEFFECTS DO BENZODIAZEPINES
HAVE ON THE VARIOUS SYSTEMS OF
THE BODY? EFFECTS:
EFFECTS:
ADVERSE EFFECTS:
WHAT EFFECTS DO BENZODIAZEPINES HAVE ON
THE VARIOUS SYSTEMS OF THE BODY?
EFFECTS:
EFFECTS:
THINGS TO CONSIDER ABOUT
BENZODIAZEPINES
• Diazepam is not __________-soluble and cannot be mixed with watersoluble agents except ketamine
• Midazolam and zolazepam are water-soluble and can be mixed with other agents
• Diazepam is painful and poorly absorbed when administered
intramuscularly
• Midazolam is more readily absorbed via IM and SQ routes
• Zolazepam is available only mixed with tiletamine to produce the
combination product ____________.
• Diazepam is very soluble in plastic and over time is absorbed by syringes, IV
bags, and IV tubing
THINGS TO CONSIDER ABOUT
BENZODIAZEPINES
• Diazepam and midazolam are light-sensitive
• Onset of action/duration of action
• Less than or equal to 15 min after IM injection
• Duration: 1-4 hours
ALPHA-2 AGONISTS
XYLAZINE
DEXMEDETOMIDINE
GENERAL INFO ON ALPHA-2 AGONISTS
 These drugs ________controlled
 These drugs ___________reversed
 These drugs do provide _____________ effects
 These drugs act on alpha-2 adrenergic receptors in the
CNS and PNS causing a decrease in the
neurotransmitter norepinephrine
WHAT EFFECTS DO ALPHA-2 AGONISTS HAVE ON
THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
EFFECTS:
ADVERSE EFFECTS:
EFFECTS:
WHAT EFFECTS DO ALPHA-2 AGONISTS HAVE ON
THE VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
EFFECTS:
ADVERSE EFFECTS:
OTHER EFFECTS OF ALPHA-2 AGONISTS
• Hyperglycemia: alpha-2 agonists reduce the secretion of insulin by the
pancreas
• Hypothermia: alpha-2 agonists decrease thermoregulation and shivering
• Premature parturition
• Can be absorbed through the skin and abrasions – as little as 0.1ml of
dexmedetomidine can cause hypotension and sedation in humans.
THINGS TO CONSIDER ABOUT ALPHA-2
AGONISTS
• Xylazine is largely reserved for use in large animals
• Cattle are sensitive and only require 1/10 of the dose used in horses
• ___________________ is largely used in small animals and is _______
potent than xylazine
• Both drugs are commonly mixed with other drugs such as ketamine, and
an opioid such as butorphanol or morphine
• Animals can undergo minor and major surgical procedures with these
combinations
THINGS TO CONSIDER ABOUT ALPHA-2
AGONISTS
• These drugs can be reversed with Yohimbine (reverses xylazine) and
______________ (reverses dexmedetomidine)
• Atipamezole is sold in combination with dexmedetomidine and is given in a
__________ ratio
• It is not recommended to treat bradycardia with anticholinergics, but
rather the appropriate reversal agent
• Reversal takes only 5-10min
OPIOIDS
AGONISTS
PARTIAL AGONISTS
AGONIST-ANTAGONISTS
ANTAGONISTS
GENERAL INFO ON OPIOIDS
 MODE OF ACTION
 3 Primary receptor in the brain and spinal cord
 Mu, kappa, delta
 SEDATION
 ONSET OF ACTION:15min after IM administration
 DURATION: 1-3 hrs for most (buprenorphine 6-8 hrs)
 ANALGESIA
 *excellent somatic and visceral analgesia
WHAT EFFECTS DO OPIOIDS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
EFFECTS:
ADVERSE EFFECTS:
WHAT EFFECT DO OPIOIDS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS:
ADVERSE EFFECTS:
EFFECTS:
ADVERSE EFFECTS:
OTHER EFFECTS OF OPIOIDS
• Allergic reactions: morphine for example may cause facial swelling and
hypotension after rapid Iv administration
• Changes in body temperature: there is a resetting of the
thermoregulatory center in the brain resulting in the dog panting and
possibly lowering the body temperature
• Cats may have an elevated body temperature for unknown reasons.
• Miosis in dogs; mydriasis in cats
GENERAL INFO on OPIOIDS
 These are controlled substances with human abuse potential
 Opioids used in combination with a tranquilizer achieve a state of
profound sedation and analgesia termed ________________________
 These drugs can be reversed with the opioid antagonist
_________________ (works within 2 min IV and 5 min IM)
 Agonist-antagonists such as butorphanol can also be used to reverse the effects
of pure agonists
 These will be discussed further and in more detail in week 5-6