INTRODUCTION TO ANESTHESIA

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INTRODUCTION TO ANESTHESIA PRE-ANESTHETIC AGENTS

• CHAPTERS 1 3

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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

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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

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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.

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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.

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Fully conscious
Awake
Light sedation
Moderate sedation
Sedation
Deep sedation
Border between Consciousness and unconsciousness
Hypnosis
Narcosis
Light surgical anesthesia
Unconscious
Moderate surgical anesthesia
General anesthesia
Deep surgical anesthesia
Anesthetic overdose
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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.

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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.

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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

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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 veterinarians 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

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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
  patients minimum database

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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
• _________________________________________

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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.

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PRE-ANESTHETIC AGENTS

• REASONS TO GIVE PRE-ANESTHETIC AGENTS
• _______________________________ some
  pre-anesthetic agents last long enough to be
  effective post-operatively

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CLASSES OF PREANESTHETIC AGENTS

• ANTICHOLINERGICS
• TRANQUILIZERS and SEDATIVES
• Phenothiazines
• Benzodiazepines
• Alpha-2 agonists
• OPIOIDS
• Agonists
• Partial agonists
• Agonist-antagonists
• antagonists

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ANTICHOLINERGICS

• aka parasympatholytics
• or sympathomimetics

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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

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ANTICHOLINERGICS

• Acetylcholine is the primary neurotransmitter in
  the PNS responsible for parasympathetic effects
  (cholinergic effects)

Ach
Ach
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ANTICHOLINERGICS

• These drugs are given to counteract the effects
  caused by vagal stimulation
• EXAMPLES Atropine, Glycopyrrolate

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ANTICHOLINERGICS
Ach
Ach
ANTICHOLINERGICS ONLY AFFECT _________________RECE
PTORS ON THE TARGET ORGANS
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WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
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WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
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WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
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WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
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WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE
VARIOUS BODY SYSTEMS?
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WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE
VARIOUS BODY SYSTEMS?
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WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE
VARIOUS BODY SYSTEMS?
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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 _at_ 10-20min, duration
  60-90min
• Atropine IV 1 min, peak _at_ 3-4 min, duration
  several minutes
• Glycopyrrolate IM similar onset time to
  atropine, peak _at_ 30-45min, duration 2-3 hrs

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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

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TRANQUILIZERS and SEDATIVES

• PHENOTHIAZINES
• BENZODIAZEPINES
• ALPHA-2 AGONISTS

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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/sedativ
  e may still be easily aroused and could
  potentially get aggressive or injure themselves

http//www.youtube.com/watch?vAkaGWwTHD5g
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PHENOTHIAZINES

• ACEPROMAZINE
• CHLORPROMAZINE

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GENERAL INFO on PHENOTHIAZINES

• These drugs have no _____________ effects
• These drugs are not controlled
• These drugs do not have a ____________ agent
• Examples Acepromazine, Chlorpromazine

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WHAT ARE THE EFFECTS THAT PHENOTHIAZINES HAVE ON
THE VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
EFFECTS
ADVERSE EFFECTS
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WHAT ARE THE EFFECTS THAT PHENOTHIAZINES HAVE ON
THE VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
EFFECTS
ADVERSE EFFECTS
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OTHER EFFECTS ADVERSE EFFECTS of
PHENOTHIAZINES

• ANTIHISTAMINE EFFECT
• PENILE PROLAPSE
• DECREASED PCV
• Onset of action/duration of action
• 15min after IM injection, peak_at_ 30-60 min
• Duration 4-8 hrs( could be up to 48hrs)

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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.

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BENZODIAZEPINES

• DIAZEPAM
• MIDAZOLAM
• ZOLAZEPAM

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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

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WHATEFFECTS DO BENZODIAZEPINES HAVE ON THE
VARIOUS SYSTEMS OF THE BODY?
EFFECTS
EFFECTS
ADVERSE EFFECTS
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WHAT EFFECTS DO BENZODIAZEPINES HAVE ON THE
VARIOUS SYSTEMS OF THE BODY?
EFFECTS
EFFECTS
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THINGS TO CONSIDER ABOUT BENZODIAZEPINES

• Diazepam is not __________-soluble and cannot be
  mixed with water-soluble 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

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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

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ALPHA-2 AGONISTS

• XYLAZINE
• DEXMEDETOMIDINE

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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

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WHAT EFFECTS DO ALPHA-2 AGONISTS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
EFFECTS
ADVERSE EFFECTS
EFFECTS
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WHAT EFFECTS DO ALPHA-2 AGONISTS HAVE ON THE
VARIOUS BODY SYSTEMS?
EFFECTS
ADVERSE EFFECTS
EFFECTS
ADVERSE EFFECTS
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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.

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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

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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

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OPIOIDS

• AGONISTS
• PARTIAL AGONISTS
• AGONIST-ANTAGONISTS
• ANTAGONISTS

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GENERAL INFO ON OPIOIDS

• MODE OF ACTION
• 3 Primary receptor in the brain and spinal cord
• Mu, kappa, delta
• SEDATION
• ONSET OF ACTION15min after IM administration
• DURATION 1-3 hrs for most (buprenorphine 6-8
  hrs)
• ANALGESIA
• excellent somatic and visceral analgesia

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WHAT EFFECTS DO OPIOIDS HAVE ON THE VARIOUS BODY
SYSTEMS?
EFFECTS
ADVERSE EFFECTS
EFFECTS
ADVERSE EFFECTS
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WHAT EFFECT DO OPIOIDS HAVE ON THE VARIOUS BODY
SYSTEMS?
EFFECTS
ADVERSE EFFECTS
EFFECTS
ADVERSE EFFECTS
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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

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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