Anesthetics and Anesthesia Flashcards
substances which when applied about the nerve
terminals or nerve fibers prevent conduction of both sensory and motor
impulses in axons and dendrites
local anesthetics
first local anesthetic discovered
cocaine
characterized by reversible loss of perception of pain or other motor response to stimuli in a local or regional part of the body and is not accompanied by loss of consciousness
local or regional anesthesia
Types of local anesthesia
- Surface or topical
- Infiltration
- Peripheral
- Spinal
- Epidural
Surface or topical local anesthesia
- Cocaine
- Hexylcaine
- Lidocaine
- Tetracaine
- Cyclomethylcaine
local anesthesia directly into skin or deeper structures
infiltration
area immediately surrounding the nerve or group of nerves
peripheral
Peripheral anesthetics
- Lidocaine
- Mepivacaine
- Bupivacaine
into CSF of the spinal subarachnoid space
spinal (intrathecal)
Spinal anesthetics
- Lidocaine
- Tetracaine
space of the spinal canal posterior to the end of the
spinal canal
epidural
Epidural anesthetics
- Lidocaine
- Mepivacaine
- Bupivacaine
- Etidocaine
- Chloroprocaine
refers to peripheral nerve block, spinal and epidural anesthesia
Regional anesthesia
Chemical structure of most useful anesthetics has 3 parts
- an aromatic ring (lipophilic group)
- an intermediate chain
- amino group
Amino ester agents
- Procaine
- Chloroprocaine
- Tetracaine
- Cocaine
Procraine
low potency, short duration of action
Chloroprocaine
rapid onset of action
Tetracaine
high potency, long duration
Cocaine
surface anesthetic, abused drug
Amino amide agents
- Lidocaine
- Mepivacaine
- Bupivacaine
- Etidocaine
- Prilocaine
- Dibucaine
Agents restricted to opthalmological use
- Benoxinate
- Proparacaine
Dibucaine
very potent, long duration of action
Prilocaine
like lidocaine
Lidocaine
most versatile, high potency, rapid onset, moderate duration of action
mepivacaine
like lidocaine
bupivacaine
slow onset, long duration
etidocaine
long duration, profound muscular relaxation
Agents used to anesthetize less delicate mucous membrane and skin
- Cyclomethycaine
- Dimethysoquin
- Diclolin
- Hexylcaine
- Pramoxine
- Benzocaine
- Butamben
basic functional unit of the nervous system
nerve cells (neuron)
Parts of the neuron
- cell body
- Dedrite tree
- Axon
Steps in interneuron transmission of a nerve impulse
- Action potential propagated in presynaptic nerve
- Transmitter synthesis
- Transmitter storage
- Interneuron transmitter breakdown or inactivation
- Transmitter release
- Transmitter reuptake
- Transmitter synaptic degradation
- Transmitter attachment to postsynaptic receptor
- receptor – induced increase or decrease in ionic conductance or altered
cellular
Neurotransmitters classified into
2 groups
- Small molecule, rapidly acting neurotransmitters
- Slowly acting, neuropeptide transmitters
widely distributed in the CNS, is inactivated by hydrolysis, presynaptic receptors exist at many nerve terminals in the CNS
Ach
hydrolyses Ach
acetylcholinesterase
Monoamines (3)
- Norepinephrine
- Dopamine
- Serotonin
Amino acids
- GABA - gamma-amonobutyric acid
- Glycine
- Glutamate
- Aspartate
Slowly acting, neuropeptide transmitters
- Beta endorphin
- Vasopressin
- Oxytocin
- Growth hormone
- Enkephalin
- Substance P
- Somatostatin
- Cholecystokinin
- Angiotensin II
- Neurotensin
NE has an ______ distribution in the CNS
uneven
NE mechanisms are important in (4)
- Control of sleep and wakefulness
- Control of mood
- Emotional behavior
- temperature
has a role as a precursor in the synthesis of norepinephrine
dopamine
largest concentration of dopamine
- basal ganglia
- limbic system
Dopamine is linked to (3)
- control of movement (CNS)
- disturbances of behavior
- hypothalamic pituitary endocrine system
has a major role in the control of spinal and cerebral reflexes
GABA
major inhibitory transmitter in the CNS and it is involve in the conduction of convulsions and may also be important in anxiety states
GABA
GABA is found in high concentration
- Brain
- Spinal cord
GABA only in trace amounts
peripheral nerve tissue
The actions of glycine seen to be restricted to
- Spinal cord
- Lower brain stem
- Retina
exert powerful stimulatory effects in nearly all regions of the brain
- Glutamate
- Aspartate
Therapeutic benefits of glutamate and aspartate
Inhibition of epilepsy and neurotoxic effects of brain ischemia
USES OF ANESTHETICS IN ANIMALS
- Euthanasia
- Control of convulsions
- Elimination of sensibility to noxious stimuli
- Humane restraint
- Technical efficiency
- Specific biomedical research tool (sleep time)
In the general continuum of general anesthesia, unconsciousness maybe
with or without somatic and visceral response. The series of events are;
- alert wakefulness
- Lethargy
- Drowsiness
- Unconsciousness
- Come
- Death
property known to correlate best with potency of inhalant anesthetic
inhalant anesthetic
Inhalation anesthetics are
hydrophobic
Inhalation anesthetics act in?
cell membrane lipid layer
2 individuals who independently noted that the potency of anesthetics increased directly in proportion to their partition coefficient between olive and water
Overton rule
Primary aims of pre anesthetic medication
- Facilitate handling
- To calm the animal
- Relieve preoperative pain
Secondary aims of pre anesthetic medication
- Minimize undesirable reflex automatic nervous system activity
- Supplement general anesthesia
- Minimize undesirable post anesthetic reactions
- Continue treatment of intercurrent disease
- Prevent infection
Major classes of drugs commonly considered for preanesthetic medication
- Tranquilizers-sedative
- Hypnotic-sedative
- Opioid
- α2 adrenergic agonist
- Dissociative
- Combination
- Parasympatholytic
Tranquilizers-sedative
- Acepromazine
- Diazepam
- Midazolam
- Droperidol
- Azaperone
Hypnotic sedative
- Pentobarbital
- Chloral hydrate
Opoiod
- agonist – morphine
- meperidine
- agonist – antagonist -
butorphanol
α2 adrenergic agonist
- xylazine
- detomidine
- medetomidine
Dissociative
Ketamine
Combination examples
- tiletamine plus zolaepam-telazol
- fentanyl plus droperidol
= innovar
Parasympatholytic
- atropine
- gylcopyrrolate
frequently administered to
produce a calming effect
Tranquilizers (ataractics or neuroleptics)
Subclasses of Tranquilizer-sedatives
- Phenothiazine
- Butyrophenones
- Benzodiazepines
Phenothiazine uses
- Antiarrythmic
- Antihistaminic
- Antiemetic effects
less frequently used but better cardiovascular stability than phenothiazine
Butyrophenones
pain and occasional erratic absorption after IM (e.g
diazepam)
Benzodiazepines
cause a dose dependent
spectrum of CNS depression, sedation, sleep, anesthesia, coma, and death
Hypnotic-sedatives
Common effects of Xylaszine
- Bradycardia
- Mild arterial hypertension followed by more prolonged hypotension
- Hyperglycemia
- Increased urine volume
Important advantages of the use of opioids in preanesthetic period
- Potent analgesia
- Good sedation
- Absence of direct myocardial depression
Disadvantages of opioids as a preanesthetic
- Decrease in intestinal propulsive activity.
- Depression of medullary ventilatory control centers leading to
hypoventilation. - Commonly induce a vagolytic effect so heart rate may also be
decreased. - Opioid - induced emesis-may be wanted or unwanted
Ketamites causes ______ in cats
state of somatic analgesia
Ketamites causes ______ in horse
CNS arousal
Improves the reliability of the sedative properties of either drug used
alone without adding further vital organ depression
Telazol (Tiletamine + zolazepam)
Reliable sedation and potent analgesia with limited vital organ
depression
Innovar
Innovar is countered by
atropine
commonly an unwanted effect of innovar
bradycardia
Innovar is a drug combinations of
fentanyl + droperidol
Common reasons for administering parasympatholytic (anticholinergic ) drugs
- Reduce upper-airway and salivary secretions ( antisialogogue effect)
- Counteract reflex bradycardia occurring with opioid use or certain
surgical manipulations.
Stage I Induction or stage of voluntary excitement
- consciousness still present
- forcible effort to avoid being anesthetized
- breath holding , but may not be observed in all cases
- fear and apprehension leading to increased respiratory rate and
pulse rate - papillary dilatation (mydriasis)
- urination and defecation
Stage II Stage of involuntary excitement
- loss of consciousness
- reflex response stimuli such as exaggerated limb movement
- pronounced vocalization
- unpredictable degree of violence which bears no relationship with the normal temperament of the animal; some may pass quietly
through this stage - irregular respiration; sometimes breath holding
- persistent pharyngeal reflex which progressively becomes
depressed
as a gas anesthetic, it is colorless with unpleasant smell
Nitrous oxide
weak anesthetic used only in combination
with other agents having greater narcotic effect
nitrous oxide
Halothane may cause
hepatic dysfunction
drug of choice for the control of seizures in dogs and cats
Phenobarbital
good choice for control seizures in cats, but not for dogs
diazepam
Anticonvulsants that is toxic to cats
Primidone
substance which temporarily abolishes the
sensation of pain
analgesic agent
substance which produces insensibility from which
simple stimuli produce a temporary arousal
narcotic
narcotic agent used to induce sleep
hypnotic
narcotic agent which is used to calm a nervous, vicious or excited subject
sedative
most sedatives cause
drowsiness
substance which produces sedation without at the same time causing drowsiness
Ataractic or tranquilizer
tranquilizer used in human beings in the treatment of
psychoses
neuroleptic
substance which produces in human beings a feeling of dissociation from surroundings, unconsciousness, catalepsy, vivid dreams and analgesia
dissociative agent
used in animals to produce a state of thought resembling anesthesia in which the animal does not show response to stimuli
dissociative agent
Plane 1
- irregular automatic breathing
- limb movement stops
- side to side movement of the eyeballs
- disappearance of palpebral, conjunctival and corneal reflexes
- brisk pedal reflex
- may be adequate for minor surgery
Plane 2
- laryngeal reflex persists until the middle of plane 2
- eyeballs fixed in the center in the horse, cats sheep, and pigs;
downward in dogs
- pedal reflex becomes sluggish
- progressive muscle relaxation
- adequate for all surgical procedures except abdominal surgery
Plane 3
- breathing still automatic but the respiratory rate increases while the depth decreases
- noticeable pause between inspiration and expiration
Stage IV. Overdose
- complete paralysis of the thoracic muscles; only the diaphragm functions
- jerky diaphragm movement
- respiratory movement gasping in nature
- wide papillary dilatation
Stage I
Induction or stage of voluntary excitement
Stage II
Stage of involuntary excitement
Stage III
Surgical anesthesia
Stage IV
Overdose