Preanesthetic medicatoins and dissociative anesthetics

Question 1

tranquilizers/anxiolytics

Answer 1

relieve anxiety without overt sedation

patient easily aroused and aware of surrounds

neuroleptics, ataractics

Question 2

sedatives

Answer 2

a state of central depression accompanied by drowsiness

makes it easier for patient to fall asleep

not as easily aroused

unaware of surroundings but response to painful stimulation

Question 3

analgesics

Answer 3

drugs use to provide freedom or absence of pain

Question 4

nacrosis

Answer 4

drug induced sleep

detines the sedation produced by opiats and opioids

Question 5

neuroleptoanalgesia

Answer 5

combination of a sedative/tranquilizer and an opioid

provides chemical restraing and greater degree of sedation and analgesia

numerous combination are possible

Question 6

dissociative anesthesia

Answer 6

state induced by drugs that interfere with transmission of nervous impulses between limbic system and thalamocortical areas of the brain

Question 7

reasons to pre-med (10)

Answer 7

reduce anxiety, apprehension, fear and resistance

render the patient more amendable to handling

prevents catecholamine release and CV consequences associated with it

reduces the risk of injury to patient and staff

counterat negative effects of sedative/anesthetic agents

preemptive analgesia

smooth induction of anesthesia

drug sparring

smooth maintenance of anestheia

smooth recovery

Question 8

considerations for pre meds

Answer 8

species

temperatment

desired drug effect and duraiton of action

undesirable effects of drug

degree of pain

health status of animal

Question 9

classes of common preanesthetic agents

Answer 9

phenothiazine

benzodiazepines

alpha-2 adrenergic agonists

opioids

dissociatives

Question 10

phenothiazines MOA

Answer 10

tranquilizers

dopamine antagonist (basal ganglia and limbic system) causes: anxiolysis, antiemetic, antihistamine, antiarrhythmic

block alpha1 addrenoceptors peripherally-causes vasodilation and hypotension, decrease PCV (splenic dilation), hypothermia

Question 11

acepromazine ADME

Answer 11

hepatic metabolism

renal excretion

highly protein bound (>90%)

onset-slow 30 to 45 min (IM), 5 to 15 min (IV)

duration: 3 to 8 hours

Question 12

what happens when acepromazine is given at a high dose?

Answer 12

prolongs duraiton of action but not degree of tranquilization

extrapyramidal effects

Question 13

acepromazine complications

Answer 13

vasodilation–>hypotension

renal hypotension

hypoproteinemic animals-prolonged duration of effect

flaccid paralysis/paraphimosis of penis and priapism in stallions

no antagonist

epinephrine reversal

Question 14

beznodiazepines MOA

Answer 14

anxiolytics-depression of limbic system

muscle relaxants-internuncial neurons at spinal levels

controlled substance-Class Iv

modaulation of GABA mediated neurotransmission-enhances inhibitory neurotransmission

no intrinsic activity at GABA receptors

Question 15

benzodiazepines

Answer 15

minimal CV effects

can cause mild respiratory depression, especially in the presence of other depressant drugs

wide margin of safety

antagonist available

usually used in conjunction with other drugs-effective for pediatrics, geriatrics and debilitated animals

Question 16

what happens when you give benzodiazepines to young healthy animals?

Answer 16

CNS excitement and altered temperament

will make a dog want to bite you since inhibitions are lost

Question 17

midazolam

Answer 17

water soluble base

IM or SQ absorption excellent and No Pain

highly protein bound

greater recept affinity

used in comb with opioids and dissociatives

lasts 1-2 hours

Question 18

diazepam

Answer 18

most commonly use benzo

insoluble in water, contains solvents such as propylene glycol and ehtanol

can cause hypotension if given rapidly IV

don’t mix with diluents

don’t give IM

highly protein bound (liver disease patients)

antagonist available

Question 19

Flumazenil

Answer 19

highlyg selective, competitve benzo antagonist

strong affinity for receptor and minim intrinsic activity

rapidly reverse the sedative, muscle relaxant and behavioral effects of benzo

works well but very expensive

not controlled

Question 20

alpha 2 agonists

Answer 20

reliably produce dose dependent sedation, analgesia and muscle relaxation

can be transietnly aroused and accurately bite or kick under sedation

analgesia similar to opioids and is synergistic with it…mostly visceral

Question 21

alpha 2 agonist MOA

Answer 21

centrally, alpha 2 agonist act via pre-synaptic receptor to inhibit release of NE and decreased sympathetic activity leading to

sedation, muscle relaxation, bradycardia, analgesia

peripherally activation of alpha 2B receptors cause vasoconstriction and reflex bradycardia

Question 22

alpha 2 agonist effects (10)

Answer 22

sedation, analgesia, muscle relaxation, bradycardia, hypertension/hypotesion, hypothermia, emesis, decreased GI motility, hyperglycemia, diuresis

Question 23

Alpha 2 agonists CV effect

Answer 23

Decreased CO

peripheral vasocontriction

hypertension, hypotension

bradycardia

arrhythmias (AV block)

don’t use atropine

Question 24

alpha2 agonist respiratory effects

Answer 24

respiratory depression-slows RR but no change in PaO2

ruminants-bronchoconstricton, increased pulmonary vascular resistance, intra-alveolar hemorrhage and pulmonary edema

brachycephalics-pharyngeal and laryngeal muscle relaxation

Question 25

alpha 2 agonist hormonal effects

Answer 25

decreased ADH secretion decreased renin secretion decreased insulin secretion decreased ACTH secretion decreased catecholamines release increased ANP release

Question 26

alpha 2 agonists GI effects

Answer 26

decreased GI motility decreased lower esophageal tone (regurgitation risk higher) emesis

Question 27

alpha 2 agonist considerations

Answer 27

species sensitivity don't use anticholnergics highly stressed animal may not sedate may cause abortion in pregnant cattle aerophagia in some dogs not controlled antagonist available

Question 28

xylazine

Answer 28

least specific commonly used in horses and cattle IM, SQ, IV onset-1 to 2 min IV duration: dose dependent 20 to 30 min combined iwth butorphanol for standing restraint in horses used with ketamine for injectable anesthesia or induction in large and small animals

Question 29

Romifidine

Answer 29

alpha 2 agonist sedation and analgesia in horses comparable to detomidine muscle relaxation is comparable to xylazine to detomidine but associated with less ataxia onset 2 to 10 min duration of effect: 40 to 80 mins

Question 30

medetomidine

Answer 30

more potent and longer duration of action when compared to xylazine IV, IM, SQ dogs and cats, horses (ataxia) onset 5 to 15 min duration of 1-2 hours

Question 31

dexmedetomidine

Answer 31

most potent and specific alpha 2 agonist available profound, long lasting effects good sedation and analgesia used in healthy dogs and cats duration is 1-3 hours can give IM, SQ, IV

Question 32

dexmedetomidine considerations

Answer 32

combine with opioids-decreased dose of both drugs if used as premed, decrease anesthetic drug doses used for chemical restraing for minor procedures use with ketamine for injectable anesthesia

Question 33

alpha 2 antagonists

Answer 33

antagonizes both sedation and analgesia may cause excitement, hypotension, muscle tremors, tachycardia and over-alertness give IM

Question 34

Yohimbine

Answer 34

alpha 2 antagonist for xylazine ratio of 10:1 (agonist:antagonist)

Question 35

tolazoline

Answer 35

alpha 2 antagonist for xylazine slow

Question 36

atipamezole

Answer 36

antagonist for Medetomidine and dexmedetomidine 1:10

Question 37

opioids

Answer 37

derived from Papaverum somniferum--\>opium endogenous opioids: enkephalin, endorphins and dinorphins used primarly for analgesia but also may cause sedation

Question 38

Opioids MOA

Answer 38

bind to specific opioid receptors and mimic the effect of endogenous opioids presynaptic (Ca) and postsynaptic (K) modulation of nociceptors receptors in brain, spinal cord and periphery

Question 39

mu receptors

Answer 39

mediate most of the effects seens with opioid use as well as most of the undesirable effects

Question 40

kappa receptors

Answer 40

mediate analgesia in central and peripheral sites but it is weak and has a ceiling effect

Question 41

OP3 or Mu opioid effects

Answer 41

analgesia sedation euphoria/dysphoria nausea, vomiting, constipation respiratory depression dependence miosis/mydriasis

Question 42

OP2 or Kappa opioid effects

Answer 42

analgesia sedation dysphoria diuresis miosis

Question 43

OP1 or delta opioid receptor

Answer 43

analgesia

Question 44

Opioids CV effects

Answer 44

minimal effect on CO, BP and rhythm bradycardia due to vaggal stimulation may occur and respond readily to anticholinergics if needed histamine released if used IV-vasodilation and hypotension

Question 45

opioids respiratory effects

Answer 45

dose dependent respiratory depression decreased responsiveness to CO2, compounded by the co-administration of sedatives or anesthesia

Question 46

opioids CNS effects

Answer 46

sedation CNS stimulation and excitement-cats and horses

Question 47

opioids thermoregulation

Answer 47

hypothermia hyperthermia in cats, horses, swine and ruminants

Question 48

opioids emesis

Answer 48

nausea and vomiting dogs\> cats less likely in post op period and in patients that are experiencing pain

Question 49

Opioids GI

Answer 49

defection initially spasm of GI smooth muscle-ileus and constipation may predispose an animal to colic or tympany more common in chronic cases

Question 50

Opioids genitourinary effects

Answer 50

urinary retention if epidural or intratecal dose dependent suppression of detrusor contractility and deccreased sensation of urge

Question 51

morphine

Answer 51

prototyical opioid full agonist of all 3 opioid receptors IM onset: 5 to 15 min duration: 3-4 hour use with tranquilizer in horses and cats inexpensive Schedule II

Question 52

oxymorphone

Answer 52

semisynthetic opioid full mu agonist analgesic efficacy and duration of action similar to morphine less likely to make dogs vomit and to cause excitement safe to give IV (no histamine release) excellent premed in pediatric, geriatric and debilitated dogs expensive schedule II

Question 53

hydromorphone

Answer 53

semisynthetic opioid full mu agonist, analgesic efficacy and duration similar to morphine similar characteristics to oxymorphone, cheaper less sedation more likely to cause hyperthermia in cats schedule II

Question 54

Meperidine

Answer 54

synthetic full mu agonnist opioid similar analgesic efficacy to morphine causes histamine release--\>no IV use atropine like effects onset 5 to 10 min duration-1 hour schedule II

Question 55

methadone

Answer 55

synthetic full mu agonist opioid much less likely to produce vomiting and histamine release acts via NMDA receptors as well duration 2 to 6 hours similar to morphine

Question 56

buprenorphine

Answer 56

partial agonist at mu receptors antagonist at kappa receptors analgesic efficacy lower than full mu agonists-mild to moderate pain control high affinity and slow dissociation from OP3 receptors slow onset, up to 45 min-1 hr for peak effect long duration of action 6-8 hour schedule III

Question 57

butorphanol

Answer 57

kappa receptors agonist Mu antagonist less effective analgesic and sedative plateau effect mild to moderate pain control (viscera) onset 5 to 7 min duration: 45 min to 1.5 hours schedule IV

Question 58

nalbuphine

Answer 58

kappa agonist and mu antagonist mild analgesia, minimal to no sedation duration: 1 to 2 hours used to reverse mu agonist effects, maintain some analgesia not scheduled

Question 59

naloxone

Answer 59

pure antagoinst at all opioid receptor less effective against partial agonists short acting, re narcoitzation is possible

Question 60

naltrexone

Answer 60

long acting derivative of naloxone useful when a longer acting reversal is needed

Question 61

acepromazine/opioid

Answer 61

can be used in healthy, active dogs, husky types, and biting types used in cats but sedation is minimal provides neuroleptanalgesia

Question 62

benzodiazepine/opioid

Answer 62

providdes neuroleptanalgesia mild sedation, use if debilitated CV stability both drugs can be antagonized

Question 63

alpha 2 agonist/opioid

Answer 63

used for chemical restrain in aggressive dogs horses-standing procedure, premed can do minor surgical or diagnostic procedure causes bradycardia do not use if debiltated good analgesia both drugs can be antagonized

Question 64

dissociative drugs

Answer 64

provide dose dependent unconsciousness and analgesia ranging from mild chemical restraint to anesthesia rapid onset of action due to molecular weight, pKa and lipid solubility analgesia-subanesthetic doses-greater for somatic pain

Question 65

Dissociatives MOA

Answer 65

NMDA recetpor antagonism (glutamate) interference with transmission of nervous impulses between limbic system and thalamcortical areas of brain-dissociation between subconscious and conscious systems analgesia NMDA receptors appear to be involved in hyperalgesic states after tissue injury

Question 66

dissociatives CV effects

Answer 66

indirect CV stimulation sympathomimetic by inhibition of neuronal catecholamine uptake increased CO, HR and BP CV changes can be reduced by prior administration of benzo, alpha 2 or phenothiazine

Question 67

Dissociatives CNS effects

Answer 67

increases intracranial pressure due to respiratory depression, increased muscle tone and decreased venous return can cause seizure like activity in dogs (used with benzo) avoid in epileptics and animals prone to seizures

Question 68

DIssociatives respiratory system effects

Answer 68

dose and species dependent dogs may have rate and minute volume transiently decreased but return to normal within 15 minutes cats may have apneustic, shallow, and irregular pattern at higher doses increased salivation and respiratory tract secretions

Question 69

dissociatives considerations

Answer 69

wide therapeutic index IM premed-Cats, aggressive dogs, swine, exotic species IV induction-prior to inhalational agents, used in many species IM or IV for injectable anesthesia not IM in horses--\>ataxia

Question 70

ketamine

Answer 70

used for premed, chemicacl restraint, and dissociative anesthesia ni severeal species used as induction agent may cause hyperthermia in cats in recovery

Question 71

tiletamine telazol

Answer 71

1:1 mix of dissociatve tiletamine with benzodiazepine zolazepam reconstitute with saline, will lose potency over time similar use to ketamine and benzodiazepine may have prolonged recovery due to slow metabolism of zolazepam

Question 72

anticholinergics

Answer 72

parasymatholytic drugs decrease parasympathetic tone by binding to muscarinic receptors primarily CV and GI effects pre and postsynpatic locations

Question 73

anticholinergics effects

Answer 73

used to manage bradycardia and AV blocks caused by tissue manipulation, administration of other drugs, occasionaly used to control excessive secretions can cause significant tachycardia, increase myocarial work and oxygen consumption, decrease myocardial perfusion decreases GI motility and decreases lower esophageal sphincter tone

Question 74

atropine

Answer 74

non selective anticholinergic crosses blood brain and placental barriers onset 5 to 20 min IM, 1-5 min IV duration-HR increases for approx 30 min radpily hydrolyzed by atropinase enzymes in rabbits and cats

Question 75

Glycopyrrolate

Answer 75

longer duration of action anticholinergic (1 hr) less likely to cause tachycardia than atropine may be safer for use in horses under anesthesia does not alter pupil diameter and influnece IOP

Question 76

anticholinergic considerations

Answer 76

can cause transient 2nd degree AV block, esp after IV administration not routinely used in ruminants or horses CI with tachyarrhythmias