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141 Cards in this Set
- Front
- Back
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What are the 3 primary objectives of anesthetics?
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1) Assure patient safety/ survival
2) Optimize surgical conditions 3) Pain relief/ management |
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What are the 6 steps along the path of anesthesioogy?
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1) Evaluation of patient's health
2) Get ready (equipment, etc) 3) Premedication 4) Induction 5) Maintenance 6) Recovery |
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What are the 4 parts of developing a plan geared towards optimizing anesthesia & analgesia?
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-Premedication
-Induction -Maintenance -Recovery |
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What 3 things should you monitor when performing anesthesia on a patient?
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1) Vital signs
2) Instrumentation 3) Trends |
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What are 3 things to consider selecting the best "tool" (drug) for the job at hand?
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1) Species/ patient
2) Experience 3) Availability/ conditions |
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What are 5 classes of drugs used for premedication?
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1) Anticholinergics
2) Phenothiazine tranquilizers 3) Benzodiazepines 4) Alpha2 adrenergic agonists 5) Opioids |
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What are the 6 classes of drugs used as an induction agent?
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1) Propofol
2) Dissociatives 3) Etomidate 4) Thiopental (?) 5) Alphaxiolone (?) 6) Inhalants |
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What are the 6 classes of drugs used for maintenance?
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1) Inhalants
2) Propofol 3) +/- opioids 4) +/- muscle relaxants 5) +/- alpha 2 adrenergic agonists 6) +/- local anesthetics |
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What are the 5 classes of drugs used during recovery from anesthesia?
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1) Phenothiazines
2) Benzodiazepines 3) Alpha2 adrenergic agonists 4) Opioids 5) NSAIDs |
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What are 3 drugs used to ease the recovery process from anesthesia?
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1) Anticholinergics
2) Adrenergic agonists -Dopamine -Dobutamine 3) Fluid therapy |
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What are the 5 basic reasons to premedicate animals?
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1) Analgesia
2) Decrease anxiety/ stress 3) Sedation --> chemical restraint 4) Minimize autonomic reflex activity 5) Decrease anesthetic maintenance dose requirements |
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What are the 4 routes of administration?
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1) Oral (PO)
2) Subcutaneous (SQ) 3) Intramuscular (IM) 4) Intravenous (IV) |
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Compare the onset, dependability and duration of oral and intravenous administration.
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Oral has longest duration but also has longest onset and least dependability
Intravenous has the quickest onset and most dependability but shortest duration |
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What are the 2 types of anticholinergics available to be used as a premedication?
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1) Atropine
2) Glycopyrrolate (Parasympatholytics) |
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What is the mechanism of action of anticholinergics atropine and glycopyrrolate?
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Competitively block acetylcholine on postganglionic parasympathetic cholinergic receptors (muscarinic receptor)
-Parasympatholytic causing increased heart rate, decreased GI tone, bronchodilation |
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What is the clinical use of anticholinergics (atropine and glycopyrrolate) as a premed?
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Minimize autonomic reflex activity
-Prevent/ reduce vagal effects **Treat bradyarrhythmias -Decrease salivation & secretions |
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When/ how do you use atropine?
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Either in combination with other preanesthetics or as needed anytime during preanesthetic period
-Some practitioners use routinely (current practice against) |
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If you think of treating bradyarrhythmias, what should come to mind?
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Anticholinergics!!!!!!
-Atropine or glycopyrrolate |
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How are premedications administered?
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Sq, IM or IV
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What is different about the cardiac effects of atropine and glycopyrrolate?
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Atropine is has a shorter acting cardiac effect (60-90m) than glycopyrrolate (2-4 hrs)
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True or false. The cardiac effects of anticholinergics last longer than the GI effects.
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False, the GI effects can last considerably longer
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What are the 3 desirable effects of anticholinergics (atropine & glycopyrrolate) as a premedication?
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1) Increase rate of spontaneous depolarization in SA node ( + chronotropic effect-HR)
2) Increase transit speed through AV node (+ dromotropic effect) 3) Decrease salivation (antisalogogue) |
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What are the 4 undesirable effects of anticholinergics (atropine & glycopyrrolate)?
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1) Tachycardia, tachyarrhythmias
2) Decrease GI motility (ileus, colic) -Big problem in horses 3) Pupillary dilation (may increase ocular pressure) 4) Bronchodilation, decreases respiratory secretions |
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Can atropine or glycopyrrolate cross the blood brain barrier & placenta?
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Glycopyrrolate does not
-Large quaternary compound Atropine does |
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Does atropine or glycopyrrolate have a more pronounced effect? Which would you use in an emergency situation?
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Atropine has a more pronounced effect and should be used in emergency situations
-But also more likely to cause tachycardia/ tachyarrhythmias, ocular & GI effect |
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Anticholinergics should be used w/ discretion in what animal?
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Horses
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Why don't we use anticholinergics on ruminants very often?
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Antisialogogue effect (anti salivary)
-Alters character of saliva and increases viscosity/ tenacity -Min effect on volume |
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Do anticholinergics cause analgesia? Decrease anxiety? Sedation/restraint? Decrease anesthetic requirements? Decrease ANS activity?
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Analgesia: No
Decrease anxiety: No Sedation/ restraint: No Decrease anesthetic requirements: No Decrease autonomic reflex activity: YES |
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What are the 2 groups of drugs that are the major tranquilizers?
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Phenothiazines (e.g. ace)
Butyrophenones |
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What are 3 phenothiazines?
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1) Acepromazine **
2) Promazine 3) Chlorpromazine -Large drug class- many antipsychotic drugs |
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Are butyrophenones currently used?
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No, none currently available
-Similar to phenothiazines -Droperidol, Azaprone, Lenperone |
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What are the 3 mechanisms of action of Phenothiazines (major tranquilizers)?
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1) Blockade of dopamine receptors in the basal ganglia & limbic system
2) Peripherally block alpha 2 adrenergic receptors ---> vasodilation of peripheral vasculature --> hypotension*** 3) Mild antihistaminic effect |
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What is the function of dopamine?
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Dopamine is an inhibitory neurotransmitter responsible for regulation of behavior, fine motor control and prolactin secretion
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What are the effects of blocking dopamine receptors in the chemoreceptor trigger zone?
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Produces an antiemetic effect
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What is clinical use of phenothiazines? Why?
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Commonly used tranquilizer
-Decreases anxiety & stress & calms patient -Decreases anesthetic requirements -Reduces incidence of some adverse effects to other drugs |
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True or false. Phenothiazines do not produce dependable chemical restraint.
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True
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How do phenothiazines decrease anesthetic requirements?
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Synergistic effect w/other anesthetic drugs
-Often used in combination w/ opioids (neuroleptanalgesia) |
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What are 3 ways that phenothiazines can reduce adverse effects of other drugs?
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1) Antiemetic effect
2) Antihistamine effect 3) Mild antiarrhythmic effect |
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Why is IM or IV administration of phenothiazines preferred over SQ?
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Absorption following sQ administration may be erratic
-Can be administered orally for home use |
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What is the onset of phenothiazines like? Duration?
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Relatively *slow onset
-Regardless of route -15-30 minutes Relative *long duration -2-4 h or more -May be greatly prolonged in neonates or geriatrics |
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How are phenothiazines eliminated from the system/
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Hepatic metabolism, renal excretion of metabolites
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What is the most significant cardiovascular effect of phenothiazines?
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Hypotension
-Alpha1 adrenergic receptor blockade |
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What are the 5 cardiovascular effects of phenothiazines?
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1) Hypotension
2) Concurrent reduction in CO 3) Minimal effects on HR 4) Mild antiarrhythmic effects 5) Splenic sequestration of RBCs- causes decrease in PCV |
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Why do you not want to use phenothiazines when sedating a patient to collect blood for lab data?
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Causes splenic sequestration of RBCs causing a reduction in PCV
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What are the 3 GI effects of phenothiazines?
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1) Antiemetic
2) Delays gastric emptying, reduces lower esophageal sphincter tone---> 3) Increased risk of gastric reflux |
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Why shouldn't phenothiazines be used when tranquilizing an animal for skin testing?
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Mild antihistainic effects can affect results
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What are 3 animals that phenothiazines are contraindicated in/
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1) Boxers
2) Herding breed dogs 3) Penile prolapse in male horses |
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Do phenothiazines provide analgesia?
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NO!!!
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What are 5 desirable effects of phenothiazines?
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1) MIld-moderate tranquilization
2) Antiemetic effect 3) Antihistaminic effect 4) antiarrhythmic effect 5) Long duration of effect |
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What are 6 undesirable effects of phenothiazines?
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1) Hypotension
2) Limited efficacy 3) Lowering of seizure threshold (??) 4) Penile prolapse in stallions 5) Slow onset of effect 6) Long duration of effect |
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Compare the bottle dose and clinically recommended dose of phenothiazines.
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Bottle dose is 10x clinically recommended dose
-Higher doses result in greater effect-longer duration and greater risk of adverse effects |
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Phenothiazines should be used with caution IF AT ALL in what 5 types of patients?
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1) Neonates
2) Geriatrics 3) Shocky or hypovolemic patients 4) Patients at risk of significant hemorrhage 5) Boxers |
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Do phenothiazines provide analgesia? Decrease anxiety? Sedation /restraint? Decrease anesthetic requirements? Decrease autonomic reflex activity?
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Analgesia: NO
Decrease anxiety: yes Sedation/ restraint: yes Decrease anesthetic requirements: yes Decrease autonomic reflex activity: No |
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What are the 3 main benzodiazepines? What's the reversal agent?
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1) Diazepam
2) Midazolam 3) Zolazepam -Reversal= flumazenil |
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What is the mechanism of action of benzodiazepines?
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Potentiates the effect of GABA at the GABAalpha receptor site
-GABA= inhibitory neurotransmitter -Enhance binding of GABA to the alpha subunit, resulting in increased frequency of channel opening --> hyperpolarization |
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What are the effects of GABA activation of the GABAalpha receptor?
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Increases chloride conductance, causing hyperpolarization of the neuronal membrane, thus reducing neuronal excitability
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True or false. Benzodiazepines don't have intrinsic activity at the GABAalpha receptor.
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True
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What are the 4 clinical uses of benzodiazepines?
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1) Mild sedatives
-May see paradoxical anxiety or agitation if used alone 2) Muscle relaxation -Centrally mediated 3) Anticonvulsant 4) Synergistic effects w/ other anesthetic agents -Potentiates sedative effects of other premedications -Reduce dose requirements of injectable & inhalant anesthetics |
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What is the water solubility of diazepam and midazolam?
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Diazepam: not water soluble, formulated in propylene glycol base
Midazolam: water soluble |
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What are 2 important ways that diazepam is different from midazolam?
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1) Erratically absorbed & irritating if given IM
2) Does not mix well w/ most other drugs Exception: ketamine |
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What are 3 important ways that midazolam is different from diazepam?
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1) Well absorbed when given IM or SQ
2) Compatible w/ many other premedications 3) Give one IM injection rather than several |
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The effects of diazepam is normally several hours, but it may be prolonged in what patients?
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Geriatrics
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Benzodiazepines are generally used as a ______ agent.
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Adjuctive agent w/ other drugs
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What are 5 reasons that benzodiazepines are usually used as an adjuctive agent with other drugs?
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1) Enhance sedation/ restraint w/ opioids
2) Counteract muscle rigidity produced by dissociatives 3) Prevent seizure activity produced by dissociatives 4) Reduce the dose of injectable agent required 5) Reduce the dose of inhalant anesthetics |
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The cardiopulmonary effects of benzodiazepines are: profound or minimal?
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Minimal
-Very high safety margin |
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Benzodiazepiens are often substituted for______ in neonates/geriatrics/ high risk patients.
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Acepromazine
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What benzodiazepine has a more dependable short duration of action in geriatrics?
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Midazolam
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What is the drug of choice for emergency treatment of seizures?
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Diazepam
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Zolazepam is only available in ____.
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Telazol= tiletamine (dissociative) + midazolam
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What class of drug are benzodiazepines?
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Class IV
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Benzodiazepines effects can be reversed with _______.
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Flumazenil
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Do benzodiazepines provide analgesia? Decrease anxiety? Do benzodiazepines cause sedation/ restraint? Decrease anesthetic requirements? Decrease autonomic reflex activity?
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Analgesia: No
Decrease anxiety: Yes Sedation/ restraint: Maybe.. Decrease anesthetic requirements: Yes Decrease autonomic reflex activity: No |
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What are the 5 alpha adrenergic receptor agonists?
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1) Xylazine
2) Detomidine 3) Medetomidine 4) Dexmedetomidine 5) Romifidine |
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What agent is best to reverse alpha2 adrenergic receptor agonists?
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Atipamezol
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What are the 3 mechanisms of action of alpha2 adrenergic agonists?
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1) Inhibit Norepinephrine release in the CNS
-alpha2 receptor provides feedback inhibition 2) Activate alpha2 receptors on nonadrenergic neuron in dorsal horn of spinal cord -Analgesic effect 3) Activate alpha2B receptors on vascular endothelium -Vasoconstriction, hypertension |
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What are the 2 anatomic locations of alpha2A receptors?
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1) CNS
2) Platelets |
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What are the 4 physiologic responses of alpha2A activation?
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1) Sedation
2) Supraspinal analgesia 3) Centrally mediated bradycardia 4) Hypotension |
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What are 2 anatomic locations of alpha2B receptors?
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1) Spinal cord
2) Vascular epithelium |
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What are 4 physiologic responses of alpha2B activation?
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1) Spinal analgesia
2) Vasoconstriction 3) Hypertension 4) Peripherally mediated bradycardia |
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What is the anatomic location of alpha2C receptors?
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Spinal cord
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What are the 3 physiologic responses of alpha2C activation?
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1) Spinal analgesia
2) Hypothermia 3) Modulate dopaminergic activity |
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What alpha2 adrenergic agonists has the least alpha2 specificity? Highest alpha2 specificity?
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Least: xylazine 160:1
Mot: Dexmedetomidine 1620:1 |
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What are 4 clinical uses of alpha2 adrenergic agonists?
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1) Profound sedation- chemical restraint
-Can decrease dose requirements of other drugs -Excited animals may be refractory to sedation 2) Analgesia -Sedative effects outlast analgesic effects 3) Rapid onset 4) Terminate effects w/ rapid & complete reversal |
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Why may excited animals be refractory to sedation with alpha2 adrenergic agonists?
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Endogenous catecholamines compete for binding sites
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How are alpha2 adrenergic agonists administered?
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SQ, IM, IV
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Are the cardiovascular effects of alpha2 adrenergic agonists profound or minimal?
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PROFOUND
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What are the 4 cardiovascular effects of alpha2 adrenergic agonists?
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1) *Bradycardia
2) *Hypertension 3) Initial hypertension followed by hypotension as peripheral effects decline & central CNS effects predominate (decreased sympathetic outflow) 4) Cardiac output decreases -Secondary to increased systemic vascular resistance |
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Compare the heart rate in an animal give acepromazine to alpha2 adrenergic agonists?
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Alpha2 adrenergic agonists cause the heart rate to decrease more
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Compare the effects on blood pressure of alpha2 adrenergic agonists and acepromazine.
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Alpha2 adrenergic agonists have less fluctuation in BP
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Why can't anticholinergics fix the decrease in heart rate caused by alpha2 adrenergic agonists?
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- Does not improve CO
- Potentiates the hypertension - Increase myocardial workload & O2 consumption -Increase incidence of arrhythmias - Net effect is decreased cardiac performance |
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When is it recommended to use anticholinergics to treat bradycardia from alpha2 adrenergic agonists?
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Recommended to only treat bradycardia w/ anticholinergics if blood pressure is low
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When should the effects of alpha2 adrenergic agonists be reversed w/ antagonists?
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If bradycardia and hypertension is severe
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What are the 3 respiratory effects of alpha2 adrenergic agonists?
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1) Mild depressant when used alone
2) Potentiates respiratory depression of other drugs 3) May see stridor & dyspnea in horses & brachycephalic dogs |
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What are 4 aspects of alpha2 adrenergic agonists that are peculiar to ruminants & sheep?
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1) Marked hypoxemia may be seen
2) Mediated by alpha2 receptors on pulmonary intravascular macrophages 3) Bronchoconstriction, increases pulmonary vascular resistance, increases pulmonary vascular permeability 4) Pulmonary edema and hemorrhage |
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Alpha2 adrenergic agonists inhibit release of _______.
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Insulin--> hyperglycemia
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What are 2 ways that alpha2 adrenergic agonists cause increased urine production?
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1) Blocks effects of ADH
2) Osmotic diueresis (hyperglycemia) |
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What are 2 animals that are a concern for emesis, decrease in GI motility with alpha2 adrenergic agonists?
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Cats
Colics |
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What animal should xylazine not be used in? Why?
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Cattle--> potential for abortions
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Alpha2 adrenergic agonists impair ______ control.
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Thermoregulatory
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What are the 2 desirable effects of alpha2 adrenergic agonists?
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1) Rapid onset of profound sedation & analgesia
2) Reversibility |
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What are the 7 adverse effects of alpha2 adrenergic agonists?
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1) Cardiopulmonary effects
2) Decreased GI motility 3) Vomiting in dogs (~20%) & cats (~100%) 4) Abortion in cattle (not horses) 5) Hyperglycemia (inhibits insulin release) 6) Increased urine production - ADH inhibition, osmotic diueresis 7) Impairs thermoregulatory control |
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What animals are extremely sensitive to alpha2 adrenergic agonists?
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Ruminants
-Use 1/10 of equine dose -Use care when calculating drug dosages |
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What are alpha2 adrenergic agonists EXTREMELY useful for?
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Capture/ restraint of wildlife
-Historically xylazine was drug of choice -Currently, medetomidine/ dexmedetomidine used more frequently |
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What class of drug are alpha2 adrenergic agonists?
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Not one- not controlled substance
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What is different about the composition of medetomidine VS dexmedetomidine?
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-Medetomidine is a racemic mixture of dextro & levo rotary
-Dexmedetomidine is the dextro rotary form only |
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Compare the concentrations of medetomidine and dexmedetomidine.
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Medetomidine: 1 mg/mL
Dexmedetomidine: 0.5 mg/mL |
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What are the 3 reversal agents for adrenergic agonists?
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1) Yohimbine
2) Tolazoline 3) Atipamezole **agent of choice |
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Why is atipamezole preferred over yohimbine and tolazoline for alpha2 adrenergic agonist reversal?
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Atipamezole is highly selective for alpha2: 1200-1800X greater selectivity for alpha 2
-Tolazoline= less specificity -Yohimbine=60 x greater selectivity for alpha2 than alpha1 |
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Do alpha2 adrenergic agonists provide analgesia? Decrease anxiety? Sedate? Decrease anesthetic requirements? Decrease autonomic reflex activity?
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Analgesia: yes
Decrease anxiety: yes Sedate: Yes Decrease anesthetic requirements: yes Decrease autonomic reflex activity: NO |
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What is the definition of opioids? Opium?
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Chemically related to compounds isolated from the juice of papaverum somniferum (synthetic)
Opium= unrefined extract |
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What are opiates?
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Opiates are naturally occurring substances e.g. morphine, codeine (compared to synthetic= opium and opioids)
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When is the term "opioid" used?
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To refer to all substances, natural & synthetic, that are chemical derivatives of compounds derived from opium
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What are 5 examples of opioid agonists?
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1) Morphine
2) Hydromorphone 3) Oxymorphone 4) Fentanyl 6) Codeine -There's more than 5 |
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What are 2 opioid agonists/antagonists?
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1) Butorphanol
2) Nalbuphine |
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What are 2 partial opioid agonists?
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1) Buprenorphine
2) Tramadol |
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What is an opioid antagonist (reversal agent)?
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Naloxone
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What is the mechanism of action of opioids?
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-Interact with endogenous opioid receptors
-G-protein coupled receptors: alter ion currents resulting in hyperpolarization of neuronal membranes |
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Where are opioid receptors found throughout the body?
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Principally CNS (brain & spinal cord)
Also peripheral nerves, synovium, etc |
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What are the 4 types of opioid receptors?
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1) Mu
2) Kappa 3) Delta 4) NOP (nociceptin opioid peptide) |
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What are the 4 physiologic responses of mu receptors?
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1) Supraspinal analgesia
2) Respiratory depression 3) Behavioral effects -Dogs- sedation -Cats, horses, ruminants- may see excitement 4) Pupillary effects Dogs- miosis Cats, horses, ruminants- mydriasis |
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What are the 2 physiologic responses of kappa receptor activation?
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1) Mild to moderate spinal analgesia
2) Mild sedation -Horses, ruminants- may see excitement |
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What is an agonist?
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Produces maximal physiological effect
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What is a partial agonist?
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Produces partial physiological effect
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What is an agonist-antagonist?
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Agonist activity at one receptor, antagonist activity at another receptor
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What is the definition of an anatagonist?
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Dose not produce a physiological effect
- competes with agonists for receptor site, thus inhibiting their effect |
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What is the MAJOR clinical use of opioids?
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Analgesia!!!!!
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What are the 3 clinical uses of opioids?
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1) Analgesia
2) Sedation, chemical restraint -Variable 3) Decrease doses of other drugs -Synergistic effect w/ other agents -Commonly combine w/ other sedatives |
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Opioids are a highly controlled substance that are controlled by _____ & _____.
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State and federal
-Must maintain accurate records of use -Must be stored in appropriate controlled locations -Require special licensing |
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What is a schedule I drug?
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No accepted medical use e.g. heroin
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What is a schedule II drug?
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High potential for abuse, w/ severe dependence (e.g. morphine)
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What are the 3 cardiovascular effects of opioids?
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1) Bradyarrhythmias
-Easily managed w/ anticholinergics 2) Minimal direct effect on cardiac contractility or vasomotor tone -Minimal if any change in CO or BP 3) Histamine release |
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What 2 opioids have the most potential for histamine release?
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M&M: morphine or meperidine
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What route of administration most commonly causes histamine release?
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Rapid IV Injection
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What does histamine release result in? What animals can be at risk?
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Vasodilation & hypotension
A patient with a mast cell tumor may be at greater risk |
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What are the effects of opioids on respiratory?
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Respiratory depression
-Usually minimal clinical significance -Decrease rate & tidal volume -Raise threshold to PaCO2 |
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What is uniqe about the respiratory depression caused by partial opioid agonists?
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Have a plateau effect
-Once maximal depression reached, do not see additional depression w/ additional dose |
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Opioids may cause vomiting &/or defecation _______.
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Initially
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When do opioids cause constipation?
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With chronic use
-Colic symptoms in horses? |
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What 2 animals tend to have excitatory effects at high doses of opioids?
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Horse
Cat ("morphine mania") |
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Why do dogs pant when taking opioids?
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Opioids "reset" the thermoregulatory center
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Why aren't opioids practical for long term use?
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Tolerance develops
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