Exam 1 Flashcards
Lecture 1
-Important terminology: anesthesia, analgesia, sedation, tranquilization, neuroleptanalgesia.
-Review of Calculations: calculate anesthetic drug dosage, fluid drop rates, convert % solutions to mg/ml, and determine drug dilution amounts.
Define the following terms
anesthesia, analgesia, sedation, tranquilization, neuroleptanalgesia.
Anesthesia: total loss of sensation in a body part or in the whole body, generally induced by drug (s) that depress the activity of nervous tissue either locally, regionally, or generally (central).
Analgesia: Loss of sensitivity to pain without loss of consciousness.
Sedation: CNS depression in which an animal is awake but calm and generally uninterested in its surroundings, often interchangeable with tranquilization. If given sufficient stimulation the animal will be arouse/awaken.
Tranquilization: similar to sedation. The animal may be awake or not. Potentially indifferent to minor pain.
Neuroleptanalgesia: Hypnosis and analgesia produced by the combination of a neuroleptic drug (e.g., tranquilazer) and an anelgesic drug.
Anelgesia = loss of feeling
Awareness = consciousness
Agonist: a drug that produces an effect by interacting with an specific receptor site ex: opioid agonist morphine.
Antagonist: a drug that cunteracts the effects of another drug ex: opioid antagonist naloxone.
What are the five phases of anesthesia?
- Preanesthetic
- Induction
- Maintenance
- Recovery
- Postanesthetic period.
What is the difference between dose and dosage?
Dose: quantity of drug to be delivered at a particular time. It is expressed in mg, ml and calculated from the dosage rate.
Dosage: the amount of drug per unit of body weight.
Which is the only distinguishable microdrip set size after the bag has been opened?
The 60 drop.
What are some useful formulas for IV drop calculations?
drip rate = ml required/time * drops/1ml
concentration in mg/ml = mg of drug/ml of IV fluids.
ml per hour = volume to be infused in ml/length of infusion in hr
ml per minute = volume to be infused in ml/ length of infusion in hr * 60 (min/hr).
Lecture 2
What are the five W’s of performing a patient evaluation (pre-anesthetic)?
- Who should perform it: the veterinarian in charge of the patient should perform the evaluation
- What does it include: Start with the signalment. History (include previous anesthetic events)
-If patient is ill, find out what symptoms are present, the severity and how long it has been going on.
-What about recent medications, vaccinations?
-Physical exam (PE). Including BCS and BW
-Blood and urine samples
-Temperament/mentation, level of pain and stress
-Advanced diagnostics if indicated: ECG, BP, radiographs, and U/S, echo, endocrine testing, etc. - Where
- When
- Why
Is ECG a routine screening?
-For Patients with a history of cardiovascular disease
-Geriatric patients
-Underlying disease that may lead to arrhythmias: Hypekalemia, GDV, Splenomegaly, traumatic myocarditis.
AliceCor Heart monitor is an FDA approved iPhone case that produces an ECG
-Telemedicine consults with boarded cardiologists.
Physical exam, how do you use your stethoscope and fingers?
What do you evaluate with stethoscope?
Why should you palpate the trachea?
-Auscultate for murmur while palpating for femoral pulse simultaneously.
-Rate, quality, rythm
Respiratory rate: describe what you hear or don’t hear. “no presence of cracking, wheezing,..etc.
Mucus membranes, Capillary refill time. 2 seconds or less is normal. A CRT <1 sec is indicative of hyperdynamic state and vasodilation (bright red mucous membranes). It can be associated with systematic inflammation, heat stroke, distributive shocks, and hyperthermia.
What are some of the physical findings in dehydration? by percentage
<5 not detectable
5-6% subtle loss os skin elasticity
6-8% Defined prolonged CRT, eyes possibly sunken, dry mm possilbe.
10-12% tented skin stands in place, definite prolongation of CRT, eyes sunken, signs of shock.
12-15% definite signs of shock (tachycardia, cool extremities, rapid and weak pulses). Death imminent.
What are some other important part of PE and why?
-Integument: infection, tick, fleas
IV and epidurals should not be placed through infected skin. Surgery may be canceled.
Lymph nodes: maybe inflammation indication. FNA
GI tract, abdominal palpation, gut sounds. Pregnant, enlarged prostate,
Genitourinary tract: check for descended testicles
CNS: want to know about balance, seizures, aggression to select proper anesthetics.
What kind of lab work should be done before surgery?
Does extensive labwork pre-sx improve the outcome? NO
Depends on the physical exam and history of the patient.
-Young (<5 years old) healthy patient having an elective surgery with no abnormal history = PVC/TS/GLUCOSE/BUN (Big 4 or QATS).
-Older patients elective or non-elective, history of recent illness, etc. = CBC/CHEMISTRY profile/UA (minimum database).
-If break in preventative =4Dx
-+/- T4, ECG, blood pressure, thoracic radiographs, liver function, coagulation profile, etc.
Where is the pre-anesthetic evaluation performed?
When should it be performed?
Why should a pre-anesthetic evaluation be done in all patients?
-Clinic, but also done during farm calls
-Find a quiet area can better auscultate heart and lungs
-Within the day before the surgery or up to one week prior.
-Emergency cases done immediately
Questions to ask the owner:
-When was the patient last fed, pregnant, any drug or toxin exposure?
-Greater chance of safe anesthetic episode and/or more successful outcome.
-Formulate assessment of the patient’s overall organ function and preoperative risk.
-Provide client with valuable information for decision/risk.
Document the conversation prior to anesthesia
What are the five categories of ASA Physical Status Scale?
Which categories are more likely to suffer complications?
- A normal healthy patient
- A patient with mild systemic disease
- Patient with severe systemic disease
- Patient with severe systemic disease that is a constant threat to life
- Moribund patient that is not expected to survive without operation.
3-5 categories 4 times > complications than 1-2
Add E for emergency
What is the physical status of a patient?
When should the ASA be assigned?
How is an emergency defined?
-Presence or absence of disease
Determined by history, PE, laboratory and other diagnostics.
-Severity of pain present
-Levels of stress
-Overall efficiency and function of organs
-ASA after PE and labwork and diagnostics.
-Emergency: as existing when delay in treatment would lead to a significant increase in the threat to life or body part.
Why is ASA Physical status important?
-Used to assess the anesthetic risk of a case and select appropriate drugs.
-Physical status effects the pharmacokinetics and pharmacodynamics and aids in the selection of drugs, techniques for the patient.
Organs/systems we’re concerned with? = cardiovascular, pulmonary.
-Can also be used from a legal standpoint, retrospective.
What are often more important factors to considered in predict operative risk than increased ASA classification?
-Age, obesity
-Severity of operation
-anesthesia providers skill, staff
-Medicine, blood, implants
-Competence of surgical team, etc.
Increased cardiopulmonary emergencies during surgery*
Is age a disease? obesity?
What are other considerations for dosing drugs selection?
-No but it is an important independent risk factor regarding morbidity and mortality. Predictor of preoperative outcome.
-Obesity decreases CV function, at risk for hypoventilation.
-SA vs. LA
-Species variation in PK & PD
-Size of patient: smaller animals require a higher dose per unit of BW
-Obesity: volume of distribution for drugs changes
-Poor body condition, starvation
-Age: how does it change metabolic rate?
What are some of the effects of age when selecting anesthetic drug dosages?
How does fever affect metabolic rate?
-Neonate or pediatric: decrease dose
-Juvenile to early adulthood: Increase dose
-Geriatric: decrease dose
Fever: increases metabolic rate. 1 degree = 7% increase.
Hyperthyroidism: increases metabolic rate
Hypothyroidism: decreases MR.
Leukemia: can increase MR
Long-term pain: increases MR
Shock: lowers MR
Conditions for specific breeds or species
- Pigs: Malignant hyperthermia. Stress triggered, genetic.
- Quater horses: Hyperkalemic Periodic Paralysis, which causes episodes of tremors, myotonia, weakness, or paralysis in association with elevated serum potassium
- Rabbits: Malignant hyperthermia?
- Herding breeds: ABCB1/MDR1 (multidrug resistent gene mutation)
- Doberman Pinschers: Von Willebrand’s disease. Bleeding disorder. Do a buccal mucosal bleeding before emergency surgery. Avoid Acepromazine tranquilizer.
- Miniature Schnauzers: Sick sinus syndrome. Heart rate and rhythm condition, abnormal. Careful with atropine bc it can induce initial sinus bradycardia. Glycopyrrolate safer.
- Boxers: Arrythmogenic Right Ventricular Cardiomyopathy. Adult onset cardiac muscle disease. Caution with Acepromazine
- Pugs: Brachycephalic syndrome
What substances can either induce or inhibit microsomal enzymes?
Inducers
-Diazepam: maximal enzyme level after 5 days
-Diphenhydramine
-Hyperthyroidism
-Pentobarbital
-Phenobarbital
-Phenylbutazone
-Rifampin
-Progesterones
-Strogen
-Griseofulvin
-Prednisone
Inhibitors
-Chloramphenicol
-Cimetidine
-Cyclophosphamide
-Erythromycin
-Ketoconazole
-Morphine
-Organophasphates
-Quinidine
-Tetracycline
-Verapamil
Why is it important to ask owner about any current medications, including natural supplements?
They could cause problems during pre-anesthesia
What are the recommendations for the owner for patient preparation?
-Fasting and water: species and age dependent
Canine and feline: 6-12 hours. Water: access up to time of premed
Small ruminant: 12-18 hrs. Water: 8-12 hrs
Equine: 4-12 hrs. Up to premed
Cattle: 18-24 hrs. 12-18
Swine 12-24 hrs.
Rodents and rabbits: not necessary
Bird: 4-6 hrs
Birds <200g: not necessary
Neonate: not necessary.
Patients are fasted prior to anesthesia for the following reasons:
-Decrease food and fluid in stomach
-Decrease risk of aspiration
-Distended stomach or rumen impairs ventilation and could lead to hypoxemia and hypercapnia.
-In horses, a full stomach could rapture at induction
Why is it nor necessary for neonates, small birds, and some mammals to be fastened?
What about water deprivation?
They are prone to hypoglycemia within a few hours of starvation
Increased metabolic rate in birds and small mammals.
Some animals can not vomit, horses and rabbits
Water
-Renal insufficiency
-Febrile
-Diabetes
-Hot environment
Gastroesophageal reflux incidence in dogs decreased with small amount of canned food 3hrs prior to surgery.
What are the 4 H’s of Anesthetic concerns?
- Hypotension
- Hypoventilation
- Hypothermia
- Hypoxemia
Lecture 3
Premedication drugs for the anesthetic patient
-Explain why premedication drugs are beneficial for our veterinary patients
-Summarize the MOA and cardiorespiratory effects for drugs used for premedication
-Compare and list examples of neuroleptanalgesia and pre-emptive analgesia
-Estimate the cost and availability associated with different drug choices
-Associate meat and milk withdrawal times in food animals
-Identify the best resource a veterinarian can use to determine meat and milk withdrawal times in food animals.
-Explain why premedication drugs are beneficial for our veterinary patients
Should you ever induce an unsedated horse? NO
Pre and post anesthetic medications are essential to safe anesthetic management.
- Minimize stress, cardiopulmonary depression, and deleterious effects of IV and inhalant anesthesia.
- Ease of handling of patient
-Facilitates holding the patient, placing IV catheter, and further examination. - Lower dose of induction and maintenance drugs
-Minimum Alveolar Concentration (MAC) sparing effect for inhalant anesthetics. - Pre-emptive analgesia
- Smoother recovery period
- Synergistic effect form combining drugs produces better results than a single dose alone
What are the categories of preanesthetic medications? benefits? side effects?
- Anticholinergics
-Atropine
-Glycopyrrolate - Phenothiazine tranquilizers
-Acepromazine - Alpha-2 agonists
-Xylazine
-Dexmedetomidine - Benzodiazepines
-Diazepam
-Midazolam - Opioids
-Morphine
-Butorphanol
Post Anesthetics
- Analeptics
-Doxapram - Analgesics
-Alpha-2 agonists, opioid, non-opioid,
-Meloxicam
-Tramadol
Antagonists
-Benzodiazepine
-Naloxone
-Atipamazole
What is pre-emptive analgesia and why beneficial?
Analgesics given before surgery and continued intraoperative period.
Benefits:
-reduce pathophysiology associated with pain
Anticholinergics
-Inhibit bradycardia
What are they primarily used for?
When and what patients is preferred?
-Treatment of organophosphate toxicity
-Used primarily to limit salivary secretions, prevent bradycardia, or deliberately increase heart rate.
-Preferred when high vagal tone is currently suspected.
-Pediatric patient
-Prefer during anesthesia only
-Decrease cholinergic transmission
Negatives
-Atropine may induce sinus tachycardia (abnormally low sinus rhythms) or ventricular arrhythmias.
-Dry mouth, blurry vision, trouble urinating, constipation, hallucinations, confusion, decrease sweating (body temp can rise), flushing of the skin.
What is the MOA Anticholinergics Atropine and Glycopyrrolate?
Compare Atropine with glycopyrrolate
What are the side effects of these type of drugs?
MOA: inhibit acetycholine (and other cholinergic stimulators) at the postganglionic parasympathetic neuroeffector site.
Both: IV, IM, SQ.
Atropine
-60-90 mins
-crosses BBB and placenta
-Causes pupil dilation- impairs vision and may lead to poor recovery in cats.
-High doses inhibits urinary and GI tract motility
-Caution in horses and cattle
-Risk of colic, bloat.
-May produce drowsiness, disorientation, restlessness, in ruminants and elephants.
-ER endotracheal tube ok.
Glycopyrrolate
-Does not cross BBB nor placenta
-2-3 hrs
What are the physiological outputs mediated by muscarinic receptors? parasympathetic stimulation
Eyes: promotes miosis (pupillary constriction), relaxation of lens, focus on near objects possible.
Glandular secretion: stimulation of secretions except for sweat glands (inhibits).
Heart: reduced contractility, sinus rate, and AV nodal conduction. Reduce cardiac output and rate.
Lungs: bronchoconstriction, increased airflow resistance.
Recommendations for administering Atropine and Glycopyrrolate
Atropine
-Expect initial HR increase followed by a transient decrease (increase vagal tone).
Half dose IV, Half IM or SQ
Tranquilizers and sedatives
Phenothiazines
MOA: calming and neurologic effects are mediated by depression of the reticular activating system and antidopaminergic actions in the CNS
-Suppress sympathetic nervous system (depress mobilization of catecholamines centrally and peripherally)
-May lower seizure threshold in epilepsy, but INHIBIT KETAMINE.
Inhibit dopamine interaction in the chemoreceptor trigger zone in the medulla
Advantages
-Increase threshold for responding to external stimuli, though animal can be aroused by noxious stimuli.
-Reversible except Acepromazine
-ACEPROMAZINE most commonly used, not reversible
-Not analgesic but improves other drugs
Acepromazine
What breed of dog is a concern?
Phenothiazine tranquilizer
-Alpha-1 adrenergic blockade = vasodilation and HYPOTENSION
-Subsequent epinephrine drop due to B-2 effect
Reversal
-Alpha-adrenergic agonist ex: Phenylephrine
-Caution/Avoid Boxer dogs (spontaneous syncope due to sinoatrial block cause by excessive vagal tone) Atropine may help prevent this effect.
-Giant dog breeds caution, use minimum dose possible
-IV fluids for hypotension
Negatives
-Non reversible
-No analgesic effect
-Synergistic with analgesic drugs
-Antihistamine effects, careful when allergies present.
-Altered thermoregulation
Positives
-Muscle relaxer
-Long lasting 4-8 hours
-Ani-arrhythmic properties
Avoid/Caution
-Fractious or aggressive animals
-Liver disease or portocaval shunts. Primary organ of metabolism is liver.
-Valuable breeding stallions due to potential for praphimosis (inability to retract penis).
-Von Willebrand’s disease or other clotting disorders. Doberman Pinschers.
-Acepromazine significantly decreases platelet numbers, however ok in normal/healthy animals.
Acepromazine decreases platelet aggregation
-Shock or cardiovascular disease
Alpha-2 Adrenoreceptor Agonists
Xylazine 20-40 mins
Detomidine 90-120 mins
Romifidine 45-90 mins
Medetomidine 45-90 mins
Dexmedetomidine 45-90 mins
MOA: Produce CNS depression by stimulating both presynaptic and postsynaptic Alpha-2 adrenoreceptors in the CNS and peripherally.
-Decrease norepinephrine release and reduces ascending nociceptive input = decrease circulating catecholamines.
-Polysynaptic reflexes are inhibited, but neuromuscular junction is not affected.
Caution/Avoid
-Horses may be startled, approach carefully. Aggression reported in horses after Xylazine and Detomidine.
-If patient anxious or excited be careful
-Hypoventilation or apnea
-Decrease sensitivity to increased PCO2 in respiratory center.
-Horses and brachycephalic animals are prone to stridor and dyspnea from upper respiratory airway obstruction.
-Decrease cardiac output (tissue perfusion)
-Increase peripheral vascular resistance
-Ileus and bloat in dogs
-Colic in horses
-Pale mucous membranes cause by vasoconstriction
-Ataxia
-Diuresis: increase urination bc inhibits antidiuretic hormone.
-Vomiting in dogs and cats
-Suppress insulin resistance - hyperglycemia and glucosuria
Desired effects
-Pronounced sedation, sleep-like state.
-Muscle relaxation
-Analgesia
-Anxiolysis
-Can be buccally or by epidural or subarachnoid administration
-Antagonized by Alpha-2 receptor antagonists: Yohimbine, Tolazoline, Atipamezole.
Work synergistically with opioids to produce profound state of sedation
Cardiopulmonary effects
-Decrease CNS sympathetic outflow and increase parasympathetic activity.
-Induce bradycharchia, may initiate sinus bradychardia Xylazine ( Miniature Scherzer)
-Increase systemic vascular resistance
Should you give an anticholinergic when giving and alpha-2 agonist?
NOT generally recommended
-Consider administering anticholinergic IM or SQ
-Lidocaine could be considered instead. Lidocaine bolus and CRI following dexmedetomidine IV.
-Reversal with atipamezole (but patient may start waking up during surgery)
Which drug is an excellent analgesic for treating GI pain but causes oxytocin-like in ruminants? How does it work on pigs?
Xylazine or Alpha-2 agonists.
-induce premature delivery in cattle
-Pigs metabolize it too fast
Xylazine inflammatory if SQ in horse or cattle
Xylazine has two different concentrations one for SA and other for LA
1-5 mins onset or 20-40 mins
How does Detomidine compare to Xylazine?
Detomidine IM or IV
-Onset of action is lightly longer than xylazine
-Sublingual formulation available for horses
-Effects 90-120 mins
Horses 1ml IV per 1100 lbs
Romifidine produces more or less ataxia than xylazine?
Produces less ataxia than xylazine
-Effects 45-90 mins
-Typically LA dentals
Dexmedetomidine onset after IV is how long?
- 1-3 mins IV
-Quick onset
-IM 5-10 mins
-90-120 mins effects last
-Reversed with Atipamezole
-Smaller patients
Medetomidine analgesic effects last how long and sedation?
-Onset in 10 mis IM, faster if IV
-30 mins analgesia
-2 hrs sedation
-Reversed with Atipamezole
Latest drug on the market
Zenalpha
Should it be used in cats?
-Mixture of medetomidine and vatinoxan (peripheral alpha2 agonist)
1. Procedural sedations
2. Short onset 5-15 mins
3. Short duration
4. CV stability maintained at more acceptable levels
5. Reversed with Atipamezole
NOT in cats as hypotension is seen
Alpha-2 Antagonists
-Yohimbine: reversal for Xylazine typically
-Tolazoline: reversal used in camelids
-Atipamezole: concentration was formulated to the volume of injectable dose of dexmedetomidine
Tolazoline Toxicosis in Llamas
Benzodiazepines
Synergistic with other drugs for general anesthesia
Diazepam
Midazolam
Zolazepam
MOA: -Enhance the activity of CNS inhibitory neurotransmitters: gamma-amminobutyric acid, glycine, combined with CNS benzodiapzepine receptors. hyperpolarize membranes by opening the chloride channels.
-Reduces sympathetic output, minimal sedation, muscle relaxation, and antiseizure effects
Reversal: Flumazenil
Desirable effects
-No anelgesia
-Relax muscles
-Antiseizures effects
-Minimal calming effects
-Diasepam Stimulate appetite and produce pica (abnormal craving).
-Midazolam and Zolazepam are water soluble.
-Antagonize by Flumazenil
Diazepam
Where is it metabolized?
How fast can it be administered?
How long is the effects?
Can you mix with other drugs for use in cats?
-Paradoxical excitement and aggression can occur.
-Water insoluble, NOT IM (poor absorption and painful)
-Must be formulated in propylene glycol to make drug soluble.
-SLOW administration to prevent bradycardia, hypotension, or apnea.
-1-4 hours
-DO NOT mix except Ketamine. Liver failure in cats
Midazolam
Where is it metabolized?
How long is the effects?
Do you get the desirable results in normal to excitable patients?
-Liver, but metabolites are inactive
-Shorter acting and less risk of accumulation
-Absorbed through mucosal membranes in the oral cavity and in the stomach (intranasal or rectal).
-Water Soluble can IV, IM
-Better choice for sick, debilitated or older animals.
-2hrs
-NO, it won’t get them calmed down
Reversal of Benzodiazepines
Is it expensive?
Flumazenil
-Expensive
-Do not give to epileptic patient
Opioids
Where are they metabolized?
MOA: Act by reversible combination with one or more specific receptor (e.g., mu and kappa, delta) in the brain and spinal cord producing a variety of effects including analgesia, sedation, euphoria, dysphoria, and excitement.
Coupled to G-protein receptors that ultimately decrease conductance through calcium channels and open inward potassium channels, hyperpolarizing membranes and decreasing propagation of action potentials.
-Several senses are not significantly depressed by opioids: touch, vibration, vision, hearing, smell.
-Often administered before (preemptive), during (adjunctive), or after (rescue analgesia) surgery for analgesia.
-Metabolized in the liver
What are the CNS effects of opioids?
How do they especially affect cats and horses?
What are some of the negative effects?
-CNS effects include sedation, euphoria, dysphoria.
Cats and horses
-anxiety, restlessness, agitation, and dysphoria.
Negative effects
-Depression of respiratory center
-Bradycardia
-GI vomiting, defecation, salivation, decreased gastric emptying time, and ileus (absence of peristalsis, bowel obstruction).
-Miosis occurs in dogs
-Mydriasis occurs in cats
-Increased urethral sphincter tone and inhibition of voiding.
-Disruption of thermoregulation that is dose-related.
Morphine
-mu receptor high affinity
-Hydrophilic, longer duration of action than lipophilic opioids
- IM or SQ best
-Dose dependent, MAC sparing effect.
(Minimum alveolar concentration or MAC is the concentration of a vapour in the alveoli of the lungs that is needed to prevent movement (motor response) in 50% of subjects in response to surgical (pain) stimulus. MAC is used to compare the strengths, or potency, of anaesthetic vapours.).
-Duration 4-6hrs
Hydromorphone
What is a nice advantage that makes it preferable for horses?
-Semi-synthetic
-5-10 >potent than morphine
-IV, IM, SQ
-4-6 hrs (acute surgical pain 4hrs)
-Hyperthermia in cats
-Less likely to vomit if given IV
Fentanyl
-Synthetic
-100 >potent than morphine
-5-10mcg/kg
-IV bolus, followed by continuous rate infusion (CRI).
-Fast onset 1-2 mins
-Short duration 30 mins due to lipophilicity
-Transdermal fentanyl patches available
-Lollipops pediatric use in human anesthesia
Remifentanil
-Unique because metabolized by nonspecific esterases.
-Rapidly cleared not dependent on liver or kidney function
-Half as potent as fentanyl
-Requires CRI
-3-7 recovery after discontinuation
-Intense analgesia for a short time perfect
Methadone
Pure mu agonists
-Similar potency to morphine
-IV, IM dogs
-Least likely of mu agonist opioids to cause vomit
-NMDA receptor antagonist and serotonin reuptake inhibitor, which could improve analgesia and help prevent development of tolerance
-2-6 hrs.
-Very expensive.
Butorphanol
-Mixed agonist at kappa receptor and partial mu receptor agonist/antagonist
-Used for mild to moderate visceral pain, not effective for severe or orthopedic/dental pain
-IV, IM, SQ
-Duration 30 mins-2hrs
-Can be used to reverse sedative effects on respiratory mu agonists.
Useful premed for bronchoscopy or airway exam, also upper GI scope because it does not prevent passage of scope through pyloric sphincter.
Buprenorphine
-Partial mu agonist and an antagonist at kappa receptors
-Not adequate for severe pain
-Difficult to antagonize
-Long duration of action 4-8 hrs, maybe 12
-Slow onset 30 mins after IV
-IV, IM, SQ (not recommended), or transmucosal in cats
Simbadol
(buprenorphine injection)
-SQ use in cats for 24 hrs surgical pain control
-FDA approved for cats
-Up to 3 dose daily total 72 hours
-10 ml $200
Transdermal Buprenorphine (Zorbium)
-FDA approved in 2022
-Postop pain up to 4 days in cats
-Risk of accidental exposure for others
-Do NOT use in debilitated patients
-At least 4 mts of age and 2.6lbs
Adverse effects
-Hyperthermia, sedation, dysphoria, alterations in BP
Opioid Antagonists
Naloxone
-Reversal pure mu and mixed agonist/antagonist ex: butorphanol.
-High affinity for mu and kappa receptor
-Rapid onset 1-2 mins
-Lasts 30-60 mins
Nalmefene
Nalorphine
Diprenorphine
Naltrexone: longer duration twice as naloxone, wildlife reversal of carfentanil
Neuroleptanalgesia
A state of CNS depression and analgesia produced by the combination of a tranquilizer or sedative and analgesic drug.
-Hypnosis and analgesia
-May or may not remain conscious
-Useful in preanesthetic medication for a short time, simple operative procedure and cesarean section
-Horses become stuporous and attain a “saw-horse” stance.
-Bradycardia and respiratory depression can occur
-Synergism, so dose of each typically reduces
What are some examples of neuroleptanalgesia?
-Acepromazine + Opioid
-Benzodiazepine + Opioid
-Alpha2-agonist + Opioid
Dexmedetomidine (20mcg/kg) + Butorphanol (0.2 mg/kg) + (5mg/kg) Ketamine IM Kitty magic, castration procedure.
*Dental on a horse: Detomidine 40mcg/kg + Morphine 0.3 mg/kg all IV
Lecture 4 Induction of Anesthesia
Induction Drugs
Propofol
Dissociative Anesthetics
Alfaxalone
Etomidate
Barbiturates
Describe the following for the major categories of injectable drugs (listed to the right) covered in this lecture:
1. mechanism of action
2. effects of the drug on the body
3. time to onset and duration of action
4. species specific considerations
5. if contraindications to their use in a patient
6. common clinical usage
Propofol
-Abuse usually for its sedative and relaxing properties and induction of euphoric effects.
-It is nor a currently regulated substance that all veterinarians must track, depends on state.
-Milky white oil in water emulsion
Dogs ONLY
1. mechanism of action:
-Activates GABAa receptor, increases Cl- conduction and blocks sodium channel.
-Hyperpolarization
-CNS depression and loss of consciousness
-Lipophilic
-Rapid hepatic metabolism and excretion by kidneys Except Grey Hounds and Cats = longer recovery time.
- effects of the drug on the body:
-Decreases intracranial pressure and cerebral metabolism of oxygen. Anticonvulsant effects.
-Head trauma good choice
-CV: decreases BP
-Pain on injection: can give a small dose of lidocaine IV prior
-Be ready to ventilate patient if needed
Analgesia:
Muscle Relaxation: YES, transient myoclonus
Small volume:
Wide Safety Index:
Short duration of action and non-cumulative: YES
Water soluble (IM):
Minimal CV and respiratory changes:
Readily metabolized and excreted: YES
Long shelf life once vial is opened:
Availability:
Abuse potential: YES
- time to onset and duration of action
-20-30secs
-Recovery 2-12 mins - species specific considerations
-Greyhound and cats longer recovery time
-Horse: rarely used for induction excitation and volume cost, but can be use intra-op
-Swine: does not induce malignant hyperthermia
-Small ruminants and camelids: smooth rapid induction in good quality, but cost in food animals. - if contraindications to their use in a patient
-Hypovolemia, advanced age, or decreased left ventricular function. - common clinical usage
-Induction
-Constant Rate Infusion (CRI)
-C-section acceptable though crosses placenta barrier
-Can be use in patients with refractory seizures
Ketamine and Tiletamine
cats: Zolazepam + tiletamine
dogs: tiletamine + zolazepam
- mechanism of action:
-Mainly via antagonist effects at NMDA receptor: blocks binding of glutamate receptor and passage of calcium and sodium into the nerve cells = unconscious and relaxed.
-AMPA, BNDF, opioid.
-Ketamine: intranasal, IV, IM. 1 ml per 10 kg in 50:50 ratio per body weight with benzodiazepine or alpha-2 agonist. 5kg = 0.5mg = 0.25 ketamine + 0.25 benzo - effects of the drug on the body:
-Dissociation from thalamocortical (consciousness) and limbic (emotion, memory loss).
-CNS: cataleptic effect (not asleep but no response to stimuli).
-Emergence deilrium: ataxia, hyper-reflexive, sensitivity to touch, increased motor activity.
-CV: direct negative cardiac inotropic effects, but usually overcome by sympathomimetic effects.
-Increased BP, HR, CO, myocardial oxygen requirements and cardiac work.
-Inhibition of NE reuptake: increased plasma catecholamines.
-No significant respiratory depression
-Muscle rigidity and even spontaneous movements (which can be diminished with benzodiazepines)
-Increased inter ocular pressure due to increased tone of extra ocular muscles.
-Highly lipophilic crosses BBB and placenta
Analgesia: YES
Muscle Relaxation:
Small volume: YES
Wide Safety Index: YES
Short duration of action and non-cumulative:
Water soluble (IM): YES, but may be painful
Minimal CV and respiratory changes:
Readily metabolized and excreted:
Long shelf life once vial is opened: YES
Availability: YES
Abuse potential: YES
- time to onset and duration of action
-60 sec if IV or 10 min if IM
-Duration: 7-23 minutes - species specific considerations
-Cats form an active metabolite excreted unchanged in urine.
-Reports of fatal pulmonary edema in cats
-Dog: combine ketamine with benzodiazepine for induction, but can also use a alpha-2 agonist or opioid
-Cats: combine with ketamine, alpha-2 agonist, or benzodiazepine, and or acepromazine for IM
-Caution: dissociative seizures-like behavior can occur.
-Horses: adequately sedate before induction. Ketamine with benzo, or alpha-2 agonist, or guaifenesin
Telazol inductions are smooth, but recovery can be rough
-Ruminants: combine Ketamine with benzo, or guaifenesin
“ketamine stun” technique sub-anesthetic dose of ketamine (and xylazine) given to calves prior to castration
-Swine: does not induce malignant hyperthermia
Telazon reconstitute with 250mg xylazine and 250mg ketamine
Calm, slow recovery, not for pot belly pigs due to prolonged recovery
- if contraindications to their use in a patient
-Not to be used in cats with renal insufficiency
-Contraindicated if pancreatic or severe CV or pulmonary disfunction
-Avoid critically ill patients with decrease reserve, decrease BP
-Avoid if severe CV disease, tachycardia or arrhythmiaa.
-Avoid in C-section due to fetal depression
-Caution if hepatic dysfunction or pancreatitis. - common clinical usage
-CRI at sub anesthetic to reduce inhalant requirements and provide analgesic effects. NOT as sole analgesic agent
-Oral, ocular, and swallowing reflexes remain intact; nystagmus is common. Eyes stay open, provide lubrication.
What is the pressure flow and factors that rapidly change alveolar pressure (PA)?
- P delivered
- P circuit
- P inspired
- P alveolar
- P expired
- P arterial
- P tissues
- P venous
- P alveolar
- P expired
- Change in alveolar delivery
-Altered inspired anesthetic concentration: Increase vaporization of agent, decreased vaporizer setting, increased fresh gas inflow, decrease gas volume of anesthetic circuit.
- Alter alveolar ventilation
-Minute ventilation
-Dead space ventilation
- Change the removal from alveoli
-Blood solubility of anesthetic
-Cardiac Output
-Alveolar-venous anesthetic gradient
Lecture 6 NSAIDs
Learning objectives
Nine ways to minimize risks
What step is critical when prescribing pets NSAIDs?
Pet owners need to be told what the possible side effects are and their clinical signs
-Carprofen 75 mg. Discontinue and alert DVM if inappetence, vomiting, diarrhea, dark stools occur.
-Usually happens within 48-72 hrs
Pain Pathways
-AlphaBeta (Large myelinated) = Group II fastest: Low threshold mechanical (tactile or joint position)
-AlphaDelta = Group III less fast: Low threshold, mechanical or thermal. High threshold mechanical or thermal (specialized nerve endings).
-C (small myelinated) = Group IV slow: High threshold thermal, mechanical, chemical (polymodal nociceptors).
Dorsal Root Ganglia (DRG)
-Cell bodies of afferent axons provide main trophic support for the afferent nerve. Neurotransmitter synthesis.
-Large A and small B neurons: centrally nerve roots and peripherally nerves.
Terminal transduction and action Potential
-Peripheral terminal activation travels to peripheral terminal (antidromic conduction) and back to spinal cord (orthodromic conduction)
a. Low threshold transducers
b. High threshold transducers: activated by extreme changes of intensities.
