Quiz Lect 4-6 (2) Flashcards
What are five types of injectable anesthetics
Barbiturates Propofol, disassociative anesthetics, neuroleptoanalgesia, alfaxalone
What does barbiturates do
Induce Anesthesia
What does propofol do
Induce or maintain Anesthesia
What do disassociative anesthetics do
They don’t produce unconsciousness alone
What is guaifenisin used for
Large animals only
How are barbiturates classed
Based on the duration of action.
Describe thiobarbiturates
High Lipid solubility, rapid effect, 30 to 60 second onset, 10 to 20 minute duration, short recovery time due to redistribution
What is the action and pharmacodynamics of barbiturates
Depresses nerve impulses in the cerebral cortex resulting in central nervous system depression and a loss of consciousness. This affect is terminated when the agent leaves the brain and is either metabolized excreted or redistributed
What is lipid solubility
Tendency of a drug to dissolve in fats, oils or lipids
Describe highly lipid soluble drugs
Thiopental, passes into brain cells more quickly causing a faster onset of action as compared with drugs with low lipid solubility
Describe drugs with a moderate lipid solubility
Pentobarbital, largely metabolized by the liver, a process that takes longer than redistribution
What is the name of the process where highly lipid soluble drugs are removed from the brain
Redistribution
Describe the duration of action with drugs with low lipid solubility
Phenobarbital, primarily excreted by the kidneys. A very long process
Describe the process of redistribution after Iv administration
Within 60 seconds of IV injection, thiopental is disbursed throughout the body via bloodstream. Large amounts of drugs rapidly reach the brain. Animal loses consciousness within 30 seconds. Once the thiopental concentration in the blood falls below that in the brain tissue the drug begins to leave the brain and reenter the circulation
Describe Thiopental absorption in the vessel rich group
Make up about 10% of total body weight but receive 75% of total blood flow
Describe thiopental absorption in muscle
Muscle makes up about 50% of body weight but receives only 20% of blood flow
Describe thiopental absorption in fat
Fat makes up 20% of body weight but receives 5% of blood flow
What can happen with repeat administration of thiopental
Prolonged recovery due to saturation of the tissues
What are barbiturates used for
An induction agent to allow et intubation followed by inhalent anesthetic
What are the effects of barbiturates on the central nervous system
Cause a full range of central nervous system depression, from mild sedation and hypnosis to complete unconsciousness. At low doses it can also cause central nervous system excitement
What are the effects of barbiturates on the cardiovascular system
Does direct depression of myocardial cells resulting in decreased cardiac output and causing hypotension immediately. There’s also a possibility of apnea, can also cause cardiac arrhythmias and rarely cardiac arrest
How do you minimize negative effects on the central nervous system by barbiturates
Injecting a barbiturate slowly over 10 to 15 seconds, using dilute solutions, avoiding use in patients with cardiac disease
Describe the effects of barbiturates on the respiratory system
Decreased respiratory rate, title volume, plus or minus respiratory arrest. A brief period of apnea is common after IV administration. Can cause respiratory center to become relatively insensitive to increased PaCO2
Why are barbiturates contra indicated in sight hounds
Due to small amounts of body fat’s causing oversaturation of tissues
What are injectable anesthetics
Drugs characterized by their ability to producer unconsciousness when given alone. Do not provide all the effect of general anesthesia. Must be used with other agents to produce the complete spectrum of affects for general and the seizure
In which patients should you avoid giving barbiturates
With hepatic disease, renal disease, hypothermia, hypotensive patients, shock patients
What happens if you inject barbiturates perivascular
Can cause tissue sloughing.
What do you do if you give barbiturates perivascular
Inject saline in the infiltrated area at least an equal volume to dilute the solution. 1 to 2 mL of 2% lidocaine without epinephrine may be added to the saline. Lidocaine causes vasodilation absorption of barbiturate a neutralization of the drug.
What can commonly happens during induction if barbiturates are given perivascular early or very slow
May result in stage two excitement
What happens if the barbiturates are not used within two weeks if refrigerated
They lose their potency
Are barbiturates able to give analgesia
No
How quick is the onset of action for thiopental
30 to 60 seconds
How long is the duration of thiopental
10 to 15 minutes
How long is the recovery for thiopental
Within 1 to 2 hours
Why is thiopental used
Used as an induction agents in small animal anesthesia or as a sole anesthetic for brief procedures
What is the shelf life for thiopental if refrigerated
1 to 2 weeks
What is the shelf life for thiopental at room temperature
Three days
What does 2% in mg/ml
20mg/ml
Why do you avoid injecting air when reconstituting thiopental
It can cause precipitate
What does the dosage of thiopental depend on
Concurrent use of other agents, depth of Anesthesia required
Is repeated doses cumulative for thiopental
Yes
What is the class of propofol
Hypnotic, ultra short acting non-barbiturate injectable anesthetic
Describe the mode of action and pharmacology for propofol
Minimally water-soluble. Appears to affect GABA receptors in a similar manner to barbiturates. Propofol is rapidly taken up by vessel rich tissues but very quickly redistributed to muscle and fat.
Where is propofol metabolized
Primarily in the liver but also can be in the lungs if liver is compromised
Where is propofol excreted from
The metabolites are excreted in the urine
What is the onset of action for propofol
30 to 60 seconds
What is the duration for propofol
5 to 10 minutes
How long is the complete recovery for dogs for propofol
20 minutes
How long is the complete recovery for cats for propofol
30 minutes
Describe the effects of propofol on the central nervous system
Dose-dependent central nervous system depression ranging from sedation to general anesthesia
Describe the effects of propofol on the cardiovascular system
Bradycardia, decreased CO2, increased vascular resistance, transient hypotension
Describe the effect of propofol on the respiratory system
Potential respiratory depressant, causes transient Apnea after rapid IV injection. Give Bolus slowly
What are the adverse affects of propofol on the central nervous system
Transient excitement and muscle tremors, paddling muscle twitching, nystagmus and seizures
What are the adverse affects on the cardiovascular system of propofol
Hypotension
What are the adverse affects of propofol on the respiratory system
Apnea
Why is propofol used
Brief procedures of sedation such as x-rays, induction agent prior to intubation, maintenance of anesthesia via repeated IV bolus, maintenance of Anesthesia via constant rate infusion
How is propofol given
Intravenously
Describe the IV injection technique of propofol
Pre-oxygenate for 3 to 5 minutes. Give propofol slowly one fourth every 30 seconds.
What are the advantages to using propofol
Wide margin of safety, many uses, no atropine premedication needed, repeated injection noncumulative
What is propofol suitable for induction
In patients with severe renal or liver disease, young puppies or sight hounds, healthy bitches requiring C-section, asthmatic patients
What are the disadvantages to giving propofol
Apnea, cardiovascular effects, muscle tremors, Poor analgesia, high cost
What are the contraindications with propofol
Avoided in patients with cardiac disease, hypertension, avoid with opioids
What is the mode of action and pharmacology of disassociative anesthetics
Disruption of the nervous system pathways within the cerebrum and the stimulation of the RAC causing selective CNS stimulation.
What do disassociative anesthetics cause
The cataleptoid state, intact reflexes, ocular affects, increased muscle tone, Analgesia, sensitivity to light and sound
What is the cataleptoid state
Patient does not respond to external stimuli and has a variable degree of muscle rigidity
What reflexes remain intact with disassociative anesthetics
Palpebral, corneal, pedal reflexes, pupillary light reflex, laryngeal, swallowing reflex
What are the ocular affects of disassociative anesthetics
Stay open resulting in increased drying so lubricants must be used. Pupils are central and dilated
Describe the effects of muscle tone when on disassociative anesthetic
Increased muscle tone with some spontaneous random movement
What are disassociative agents usually combined with
A tranquilizer to avoid excitement and improve muscle relaxation
Describe the effects of disassociative agents on the cardiovascular system
Increased heart rate, CO2, blood pressure
Describe the effects of disassociative agents on the respiratory system
High doses can apneustic respiration
What are the adverse affects of disassociative agents on the central nervous system
Potential for seizure activity, may increase cerebral spinal fluid pressure, may cause temporary personality changes may induced nystagmus
Describe the adverse effects of disassociative agents on the cardiovascular system
Increased risk of arrhythmias
Describe the adverse affects of disassociative agents on the respiratory system
May cause respiratory depression or rest, causes increased salivation and respiratory tract secretions
Why are dissociative anesthetics used
High margin of safety, maybe used for brief procedures when given with a tranquilizer, useful for restraint of fractious animals
Why do we only give ketamine IV in dogs
Due to possibility of seizures after Im injections
How is ketamine eliminated in the dog
By hepatic metabolism
How is ketamine eliminated in the cat
Renal excretion
What are the advantages to combining ketamine and diazepam
Minimal cardiac depression, good muscle relaxation, superior recovery
What is neuroleptoanalgesia
Combination of an opioid and a tranquilizing agent that can produce a state of profound sedation
What are the commonly used opioid agents in neuroleptoanalgesia
Morphine, buprenorphine butorphanol, Hydromorphone
What are the commonly used tranquilizing agents in neuroleptoanalgesia
Acepromazine, diazepam, midazolam xylazine, medetomidine
What is neuroleptoanalgesia used for
For induction of general anesthesia and dogs, to do sedation in patients undergoing minor procedures.
When do neuroleptoanalgesics have a profound effect
In high risk or debilitated dogs.
What can rapid infusion of neuroleptoanalgesia cause
Severe hypotension and cns stimulation. Can also cause severe respiratory depression
What is referred pain
Pain felt in a place other than which it is situated
What is hyperesthesia
Increased Sensitivity to heat, cold, touch
What is pain
An aversive sensitory reaction that elicits a protective motor action and results in learned avoidance.
How often do you assess pain in an animal during surgery
Hourly
How often do you assess patients pain levels with chronic pain
Less often than major surgical patients.
How do we obtain perioperative analgesia
Preemptive analgesia and multimodal therapy
What are the benefits to multimodal analgesia
each individual drug dose is reduced
Overall anesthetic drug requirements are reduced
Overall risk of toxicity and adverse effects are reduced
Describe animals who received premedication
Avoid windup
Less general anesthetic is needed for surgery
How long before a surgery should a fentanyl patch be administered in small animals
6-12hrs
NSAIDs affect blood flow to what organ which affects excretion
Kidneys
How do we know if it’s safe to administer NSAIDs
PAP and check blood pressure during surgery. Can cause hypotension
What is the mechanism of pain relief of opioids
Works at the brain and spinal cord
What is the mode of action of NSAIDs
Tissue and brain level, reducing release of PG
What is the mode of action of local anesthetics
Works at the level of the nerves. Blocks transmission of pain by sensory pathways
What is the mode of action of an alpha 2 adrenergic agonist
Activates alpha 2 adrenergic receptors both centrally and at the periphery
What is the mode of action of ketamine
Blocks the ndma receptor in the cns at the level of the spinal cord.
What is the mode of action of corticosteroids
Tissue level, blocking pg production
What is the mode of action of tramadol
Works at the brain level, inhibition of NE and serotonin uptake
What is the mode of action of a tranquilizer
Perpetuates the actions of opioids in some patients
How is the type of analgesia for surgery decided
By the severity, the type of pain and the animals general condition
How can pharmacologic analgesia be achieved
Opioid agents
NSAIDs
Local anesthetics, alpha 2, ketamine, corticosteroids, tramadol, tranquilizer
Why are opioids combined with a tranquilizer
Diminish windup if preemptive
Analgesia
Why are opioids given postoperativly
To reduce pain
If you have moderate to severe pain which opioid do you give
Morphine, fentanyl, Hydromorphone, oxymorphone
When you have mild to moderate pain what do you give
Buprenorphine, butorphanol
What are opioids metabolized by
The liver
What are the disadvantage to giving opioid
Short duration when given by injection, cross the placental barrier, have potential for bad side effects
What is the duration of morphine with severe pain
2-3hrs.
What is the duration of morphine with mild to moderate pain
4-6hrs
What is the duration of morphine oral
4-12hrs
What are the routes of morphine
Slow iv in dogs. Im or sc.
Why do you give dogs slow iv of morphine
Sudden release of histamine a
What is particular about morphine given im
It doesn’t cause hypotension but it burns and is painful
What are the adverse effects of morphine in dogs and cats
Initial gi stimulation Potential respiratory depression Excitement Bradycardia Urinary retention Miosis Hyperthermia
How often do you have to give hydro for analgesia
Q4-6hr
What is the difference between Hydromorphone and morphine
Hydro induces more vomiting
How rapid is the onset when fentanyl is given iv
2 min
What is the duration of fentanyl Iv
30 mins
What is butorphanol good for
Moderate visceral pain
What is the use of butorphanol
Preanesthetic, sedative, postop analgesia,
What is the duration of butorphanol in dogs
1-2hrs
What is the duration of butorphanol in cats
4hr after im or sc
How is butorphanol given
Sc, im, iv, cri, oral
What are the adverse effects of butorphanol
Some respiratory depression
What is the duration of buprenorphine
6-12hrs
Do you cut or trim the fentanyl patch
No never
Where do you apply the fentanyl patch
Between the shoulder blades
How long do you need to hold the fentanyl patch in place
2-3 mins
Why are fentanyl patches used
Post op surgery, orthopaedic procedures etc
How long are fentanyl patches good for
3 days
What are the adverse effects of fentanyl
Constipation, miosis, muscle rigidity
What should you avoid wth a fentanyl patch
Heat, don’t discharge a patient with the patch
