Anesthesia Intro Flashcards
what is the ASA physical status scale used for?
determining the risk of putting a specific patient under anesthesia
ASA I
minimal risk
normal, healthy animal with no underlying disease
ASA II
slight risk, minor disease present
slight-mild systemic disturbance, animal able to compensate, neonate, geriatrics, obese animals
ASA III
moderate risk, obvious disease present
moderate systemic disease/disturbances, mild CS, anemia, moderate dehydration, fever, low-grade heart murmur/cardiac disease
ASA IV
high risk, significantly compromised by disease
animals with preexisting systemic disease/disturbances of severe nature
severe dehydration, shock, uremia, toxemia, high fever, uncompensated heart disease, uncompensated diabetes, pulmonary disease, emaciation
ASA V
extreme risk, moribund
surgery performed in desperation on animal with life threatening systemic disease
advanced cases of heart, kidney, liver, or endocrine disease, profound shock, severe trauma, pulmonary embolus, terminal malignancy
anesthesia
loss of sensation
common halogenated anesthetics: Isoflurane, Sevoflurane, Desflurane
older anesthetics: Methoxyflurane, Halothane, Enflurane
analgesia
absence of pain
opioid type: agonists, partial agonist, agonist antagonist, antagonist
preemptive analgesia is essential
sedation
CNS depression and unawareness of surroundings caused by administration of a drug
good for simple procedures
tranquilizer
CNS depression and awareness of surroundings caused by drug administration
good for anxious patients
neuroleptanalgesia
state of profound sedation and analgesia produced by the administration of an opioid and a tranquilizer
ex: Hydromorphone and acepromazine, Fentanyl and midazolam
opioids
derived from opium
synthetic or natural forms
used for analgesia or as an adjunct for induction
may be used as CRI +/- with other drugs
great MAC reducer
versatile opioid classes
agonists, partial agonists, agonist-antagonists, antagonists
opioid mode of action
opioid receptors found on neurons throughout the body, brain, spine
produce effects of sedation and analgesia
what are the 3 major opioid receptors?
mu, kappa, delta
each receptor produces a different effect
which classes of opioids bind to which receptors?
full agonists bind to mu and kappa receptors, best analgesics
partial agonists bind partially stimulate mu receptors
mixed agents only bind to kappa receptors
antagonists bind to but don’t stimulate mu and kappa receptors
which class of opioids is best for dogs?
agonists produce maximal effects on dogs
which class of opioids is best for cats, horses, and ruminants?
partial agonists work best in cats, horses, and ruminants
full agonist opioids
morphine, hydromorphine, oxymorphone, fentanyl, meperidine, and methadone
cause histamine release
C-II controlled
IV, IM, SQ, ID, epidural
partial mu agonist opioids
they have a ceiling effect = at some point increasing dosages won’t increase analgesia
ex: Buprenorphine (Buprenex)
Buprenorphine (Buprenex)
C-III controlled
delayed onset action: 45-60 minutes
duration: 4-6 hours
IV, IM, epidural, TM (cats)
kappa-receptor antagonist and partial mu agonist
AE: respiratory depression, pain on injection site
Simadol
long acting Buprenorphine injectable for cats
Butorphanol
mixed agonist-antagonist opioid
C-IV controlled
antitussive effects too
partially reverses opioid agonists
less respiratory depression and potential for abuse
has ceiling effect
half life: 20-50 minutes
duration: 2-6 hours
opioid antagonists
have a higher affinity for opioid receptor sites than narcotics do so they displace bound molecules and prevent binding of new opioid molecules to their receptors
used to treat the respiratory and CNS depression caused by opioids
Naloxone
full mu opioid antagonist
IV, IM, SQ
administration for neonates after C-section: sublingual or injected into umbilical vein
ER drug, reverses opioids
IV and sublingual onset: 1-2 minutes
IM onset: 10-20 minutes
doesn’t revere Buprenorphine
Tramadol
atypical opioid
centrally acting
mostly mu receptor activity
SNRI (serotonin and norepinephrine reuptake inhibitors)
C-IV controlled
oral, IV
Gabapentin
atypical opioid
oral add-on anticonvulsant
inhibits calcium channels resulting in decreased excitatory neurotransmission
excreted by kidneys
capsules and oral solution
NSAIDs
nonsteroidal anti-inflammatory drugs: decrease inflammation by blocking action of the enzyme cyclooxygenase (COX)
steroidal anti-inflammatory drugs: contraindicated for surgery, delays healing
not immunosuppressive
have antipyretic effects (fever reducing)
types of cyclooxygenase enzyme (COX)
COX-1 and COX-2
COX-1 performs activities that maintain health
COX-2 is involved in production of prostaglandins that promote inflammation
what two drugs shouldn’t be administered concurrently?
NSAIDs and glucocorticoids
salicylates
oldest anti-inflammatory agents
aspirin: analgesic, antipyretic, anti-inflammatory, decreases platelet aggregation
non-selective inhibitor so blocks COX-1 and COX-2, not FDA approved
propionic acid deriatives
ibufropen (humans), ketoprofen (horses), carprofen (dogs), naproxen (horses)
-fen drugs
ibuprofen not animal approved
analgesic, antipyretic, anti-inflammatory
selective COX-2 inhibitors (drug names)
Deracoxib, Firocoxib, Robencoxib
Deracoxib
selective COX-2 inhibitor
dogs > 4lbs, pain and inflammation, give after meal, blood chem before use
Firocoxib
dogs and horses
treats fever pain and inflammation, chewable tablet for dogs, oral paste for horses
caution with renal, hepatic, or cardiao dysfunction patients
Robenacoxib
dogs and cats, > 5.5 lbs and > 4 months old
injectable and tablets
give without food
Oxicam
Meloxicam: preferentially inhibits COX-2
approved for: dog (injectable, oral, or transmucosal), cat (injectable, oral, extra-label), large animal (extra-label)
don’t use with liver, cardiac, kidney, or GI patients
local anesthetics
lidocaine, bupivicane, mepivacaine, procaine
ophthalmic anesthetics: tetracaine and proparacaine
blockade of sodium channels if deposited in proximity to the neuron
infiltration, topical, intraarticular, nerve plexus, vein, or epidural
Lidocaine
injectable, topical, patch
rapid onset
short duration
mix with epinephrine for longer duration
Bupivacaine
narrow therapeutic index
never give IV!!
longer onset and duration
Nocita
bupivacaine liposome injectable suspension
5.3 mg/kg
half life: 72 hours
used for infiltrative surgical incision anesthetic
isotonic crystalloids
used to maintain hydration and to compensate for vasodilation, decrease in CO, or fluid loss
surgical rate: 1st hour 10 mL/kg, then 5 mL/kg
shock rate: dog 90 mL/kg, cat 60 mL/kg
bolus: 1/4 shock rate over 15-20 minutes
colloids
aka plasma expanders
support expansion of blood volume or BP
synthetic rates: bolus 5 mL/kg over 20-30 minutes, CRI dog 10-20 mL/kg/day, cat 5-10 mL/kg/day
natural: used for anemia, hypoproteinemia, coagulation disorders, thrombocytopenia
hypertonic saline
3%, 5%, 7%, 23.5%
used to treat hypovolemic, traumatic, or endotoxic shock and increase ICP
rapidly but temporarily draws water into the IVF space and increases BP
rapidly diffuses to the ISF space
usually given with colloid or crystalloids
3-4 mL/kg slow over 5-10 minutes
if given too fast can cause decreased BP, bradycardia, shallow tachypnea, bronchoconstriction
