Sedatives (Analgesia, Anesthesia) Flashcards
tranquilizer (neuroleptic, anxiolytic)
- induces state of behavioral change wherein anxiety is relieved and patient is relaxed although aware of surroundings
- NO ANALGESIA or ANESTHESIA
sedative
induces state characterized by CNS depression and drowsiness, decreased awareness of surroundings
hypnotic
induces sleep
analgesic
- attenuate nociceptive input leading to reduction in pain sensation
- STOP TRANSDUCTION AND TRANSMISSION
antihyperalgesics
- decrease central sensitization to pain
- DO NOT BLOCK TRANSMISSION OF STIMULUS
antinociception
diminished ability to perceive pain
narcotic
induces analgesia and stupor bordering on general anesthesia
neuroleptanalgesia
- ANALGESIA and AMNESIC state produced by administration of a neuroleptic + narcotic
- deep sedation achievable, unconciousness may occur
premedication
drug(s) given before a medical, surgical, or invasive procedure to induce sedation, analgesia, and relieve anxiety
blood-brain barrier
- tight capillary endothelial junctions
- sealed off by glial cells
- active transport mechanism for removal of organic acids or bases (i.e. p-glycoprotein efflux pump)
- constant flow of CSF into venous drainage
excitatory NTs
- glutamate (NMDA receptor)
- acetylcholine
inhibitory NTs
- GABA
- glycine (spinal cord)
what are the main effects of neuroleptics (tranquilizers)?
- sedation and hypnosis
- emotional quietness
- dissociation from surroundings
what class of tranquilizers have analgesic effects?
alpha-2 agonists
what is the most common phenothiazine?
acepromazine
why might you want to be careful in using a phenothiazine with a nursing or late-term pregnant animal?
- phenothiazines increase prolactin release which is normally inhibited by dopamine
- dopamine is necessary for pregnant animals, at normal concentrations there is no milk letdown
what is the chemoreceptor trigger zone (CRTZ)?
= vomiting center
are there reversal agents for phenothiazines?
no because they act in a lot of places, you just have to ride out the clinical effects (2-4 hrs)
what breeds are more sensitive to CNS effects of phenothiazines?
-boxers, brachycephalics, MDR1 mutants, large breed dogs, sighthounds
what would you be care using phenothiazines on patients in need of a splenectomy?
they reduce hematocrit leading to splenomegaly
what can a phenothiazine mask in a patient?
a hypersensitivity reaction
what animals would you practice caution in using acepromazine with?
- boxers, large breed dogs, sighthounds, MDR1 gene mutations (increased CNS effects)
- stallions (w/ possibility of seeing mare, penile prolapse and injury)
- cattle (rumenal regurg, not approved in food)
- aggressive dogs (startle more easily, increased)
- excited patients
what other drug would you take precaution in using with acepromazine?
epinephrine, stimulates a1, a2, b1, and b2 so if a1 is blocked then b2 vasodilation is unopposed
what are phenothiazines typically combine with?
analgesics
what is the number one adverse cardiovascular/respiratory effect of phenothiazines?
hypotension
what drug antagonizes benzodiazepine agonists such as diazepam, midazolam, and alprazolam?
flumazenil
full agonist
full effect triggered when bound
partial agonist
less effect triggered when bound, may be saturable (“ceiling effect”)
antagonist
- binds to a receptor and blocks effects of any agonists
- may reverse the effect of previously given agonist
inverse agonist
- binds to receptor and causes an effect that is opposite of an agonist
- reverse of what is seen w/ the agonist
competitive binding
REVERSIBLE effect
non-competitive binding
IRREVERSIBLE binding
what receptor are benzodiazepine binding sites on and what do benzodiazepines binding there cause?
- GABAa receptors
- cause hyperpolarization of neurons leading to a higher threshold (less likely to fire)
- agonize GABA leads to suppressing the CNS
between diazepam and midazolam which route of administration, IV or IM, would you give which drug?
- diazepam give IV, slowly (hypotension w/ rapid inj)
- midazolam give IM
what can diazepam cause in cats if given orally?
hepatic necrosis
what benzodiazepine works well for thunder storm anxiety?
alprazolam
what is the most reliable sedative for ruminants?
benzodiazepines
what class of drugs can have paradoxical excitation?
benzodiazepines, NOT reliable on its own
what drug is a specific reversal for benzodiazepines?
flumazenil = competitive antagonist
what class of drug is often the MOST reliable as sedatives for very young, very old, or very sick patients?
benzodiazepines
what are some contraindications of diazepam injections?
- IM = painful
- IV given fast shows hypotension
- large IV doses can cause hemolysis
T/F: benzodiazepines can serve as an anticonvulsant
TRUE! great for emergency treatment of seizures (i.e. diazepam given rectally) and status epilepticus
what are the analgesic effects on nociception for a2-agonists?
perception, modulation, transmission
what are the analgesic effects on nociception for benzodiazepines?
perception and modulation
what are the analgesic effects on nociception for phenothiazines?
perception
do benzodiazepines have analgesic effects?
no! benzodiazepines have no analgesia
what group of animals are most sensitive to xylazine?
ruminants, give smaller doses
what animals would you use dexmedetomidine used for?
dogs, cats, exotics
what animals would you use xylazine for?
horses, deer, elk (increased morbidity in dogs/cats)
what are two alpha-2 antagonists?
atipamezole and yohimbine
what is the specific competitive antagonist of dexmedetomidine?
atipamezole (antisedan)
what is the specific competitive antagonist of xylazine?
yohimbine
what are two major alpha-2 agonists?
dexmedetomidine and xylazine
what alpha-2 agonist is the most alpha-2selective? least?
dexmedetomidine = most xylazine = least
what is the emetic of choice for cats?
xylazine
why are alpha-2 agonists useful as an emetic?
because they stimulate the alpha-2 receptors in the emetic center and CRTZ
what are the two phases of the “bi-phasic effect” in the CVS that occurs with alpha-2 agonists?
phase 1 (peripheral phase)
- mediated by alpha-1 receptors
- peripheral vasoconstriction which leads to reflex bradycardia
phase 2 (central phase)
- mediated by alpha-2 receptors
- decreased sympathetic tone (decreased NE) so heart rate stays low
- leads to hypotension and bradycardia
how much can CO decrease with alpha-2 agonists?
30-50%!
what would happen if you gave anticholinergics when a patient is in phase 1 and shows reflex bradycardia?
CONTRAINDICATED, you will increase the myocardial work load and oxygen demand which can exacerbate pre-existing heart disease and make arrhythmias worse
can bradyarrhythmias occur when alpha-2 agonists are given?
yes, incomplete AV blocks (secondary most common)
would you treat cardiovascular effects for patients given alpha-2 agonists?
no! you can reverse all CVS effects
what might you worry about with giving alpha-2 agonists to sheep and goats and how it effects their respiratory system?
increase respiratory rate, increase CO2, hypoxemia, pulmonary edema
why might you take care in giving alpha-2 agonists to hyperglycemic (diabetic) patients?
transient hyperglycemia can be an effect due to decrease in the release of insulin
what animal is the most sensitive to sedative and analgesic effects? least?
goats are most sensitive
pigs are the lease sensitive
what could occur if you gave an intra-arterial injection of alpha-2 agonist to a horse?
excitement! potential for seizure
why is it contraindicated to give alpha-2 agonists to critically ill & patients with shock syndrome?
because of all the vasoconstriction to vital organs that can occur
what drugs do you NOT use concurrently w/ alpha-2 agonists?
epinephrine and atropine, can result in hypertension and increased afterload which makes the heart angry
what alpha-2 antagonist is most selective for alpha-2 receptors? least?
atipamezole = most tolazoline = least
what alpha-2 antagonist is used as a reversal for horses?
tolazoline
why is it recommended to give an alpha-2 antagonist (reversal) IM?
because the reversal would go to the periphery first (phase 1!) and selects for vasodilation first while the heart rate lags behind which could lead to CV collapse
a dog eats an amitraz tick collar, what would you see and how do you treat it?
alpha-2 CNS effects, use an alpha-2 antagonist
general anesthesia
drug-induced CNS depression resulting in unconciousness in which patient can’t be aroused by painful stimuli and sensory, motory and autonomic reflex functions are attenuated
dissociative anesthesia
drug-induced dissociation of the thalamocortical and limbic systems resulting in a catatonic state, sensory input is dissociated from perception
what are the stages of anesthesia?
- analgesia (voluntary motor excitement and analgesia)
- excitement phase (involuntary excitation or delirium)
- surgical anesthesia (4 planes of anesthetic depth)
- medullary paralysis (paralysis of vital centers in medulla)
- death (respiratory failure and/or CV collapse)
what are the analgesic effects on nociception of dissociative anesthetics?
modulation
what species has more renal excretion than others?
cats
is consciousness completely lost with dissociative anesthetics?
no! only induces stages I & II anesthesia, don’t disturb the animal, may flex or open eyes
what are the overall CV effects of dissociative anesthetics?
-INCREASED CO, CVP, HR, ICP, IOP
what sort of patients would you NOT want to use dissociative anesthetics for?
patients undergoing procedures that are contraindicated due to dissociative anesthetics causing increased ICP & IOP (i.e. craniotomy, ocular surgeries and/or brain injury or ocular trauma)
what drug has been known to have excitatory side effects at anesthetic doses? (hint: causes hallucinations in people)
ketamine
can you use ketamine as a sole analgesic?
NOT RECOMMENDED
what class of drugs do you use with ketamine at subanesthetic doses in acute pain setttings?
opioids (shown to reduce tolerance)
whats a good dissociative anesthetic to use with wildlife?
tiletamine/zolazepam (telazol)
is telitamine/zolazepam reversible?
ONLY zolazepam, recovery for combo drug is LONG
what is the only induction agent with analgesic properties/
dissociative anesthetics
kitty magic =
ketamine + dexmedetomidine + buprenorphine
what situations might you use “kitty magic” for?
- high-volume spay/neuter clinics
- fractious cats
- looking under a cat’s tongue for string
triple drip =
guaifenesin + xylazine + ketamine
- used for large animals
- form of total intravenous anesthesia (TIVA)
FLK =
fentanyl + lidocaine + ketamine
-combination used as CRI for analgesia
MLK =
morphine + lidocaine + ketamine
-combination use for CRI for analgesia
T/F: anesthetic drugs that potentiate GABA will create a dose-dependent CNS depression
TRUE! sedation> hypnosis> anesthesia> coma> death
T/F: propofol’s binding site is on GABAa receptors
FALSE, not 100% sure where receptor is
T/F: the end result of chloride entry into the cell is hypopolarization
FALSE, hyperpolarization
what is the best route of administration for barbiturates?
IV and orally, IM and SQ can cause tissue damage
how does the rate of distribution of barbiturates vary for thin animals?
slower, rate of distribution depends on lipid solubility
what are the three main effects for barbiturates?
sedation, hypnosis, and anesthesia
T/F: barbiturates act as anticonvulsants
true! they increase seizure threshold
how do barbiturates affect the brain?
- decrease intracranial pressure
- decrease brain metabolism
- neuroprotective
what can occur with accidental intra-arterial injections of thiobarbiturates?
vasoconstriction and gangrene
what animal is more sensitive to respiratory depression with the use of barbiturates?
cats
why does propoflo need to be discarded w/in 12-24 hrs?
contains eggs and soybean oil, perfect environment for bacterial growth
T/F: propoflo 28 is used in cats
FALSE, can interfere w/ RBCs coming out of bone marrow
what can cause heinz body anemia in cats if used for more than 5 days?
propofol (non-barbiturate)
how does etomidate depress the CNS?
enhances GABA!! best to use for cardiac patients
where is etomidate excreted?
metabolites are excreted in the kidney and bile
what non-barbiturate would be contraindicated for a patients w/ hypoadrenocorticism?
etomidate b/c it inhibits cortisol synthesis
