Midterm Flashcards
Allodynia
Pain caused by a stimulus that does not normally provoke pain
Analgesia
Loss of sensitivity to pain
Anesthesia
From greek word meaning insensibility to the entire or any part of the body
Balanced anesthesia
Combo of several drugs used to provide anesthesia ( usually one each addressed unconsciousness/amnesia, muscle relaxation, and analgesia)
General anesthesia
Loss of sensation to the entire body
Regional anesthesia
Loss of sensation in a larger, though limited body area ( usually blockade of specific nerves)
Local anesthesia
Loss of sensation in a prescribed body area ( blockage of specific nerve)
Surgical anesthesia
The stage/plane of general anesthesia that provides unconsciousness, muscle relaxation, and analgesia sufficient to allow painless surgery
Central sensitization
An increase in the excitability and responsiveness of nerves in the spinal cord
Circuit gas
The gases (O2 + anesthetic agent) the patient inhales and exhales and does not mix w/ ventilator drive gas
Drive gas
Gas a ventilator uses to deliver tidal volume
Eucarbia/Eucapnia
Normal CO2 concentration in patient’s blood with unit in mmHg and abbreviated as PaCo2
Expiratory time (expiratory pause)
Amount of time from completion of inspiration to initiation of the next breath
Hyperalgesia
Increased response to a stimulation that is normally painful wither at site of injury or in surrounding undamaged tissue
Hypercarbia/hypercapnia
Increased CO2 concentration in blood
Hyperesthesia/Hyperesthetic
Increased sensitivity to sensation
Hypoalgesia
Diminished sensitivity to pain
Hypocarbia/hypocapnia
Decreased CO2 concentration in blood
Hypoxemia
Decreased O2 concentration in blood’ may be due to lung disease, anatomical shunts, hypoventilation, ventilation/perfusion mismatch or breathing hypoxic gas measure…measured as PaO2
I:E ratio
Ratio of inspiratory time to expiratory time, goal to have >1:3 during ventilation
Inspiratory time
Amount of time required to deliver a tidal volume
Inspiratory pressure
Peak pressure required to deliver tidal volume and usually negative during normal breaking and positive when on a ventilator.
Line pressure
Supply pressure of gas used to drive a ventilator (50psi)
Minute volume
Tidal volume x RR measure in ml or L
Multimodal analgesia
Use of multiple drugs w/ different actions to produce optimal analgesia
Narcosis
Drug induced state of deep sleep from which patient may/may not be arousable
Narcotic
Agent that causes insensitivity or stupor…usually an opioid
Neuralgia
Pain in the distribution of a nerve or nerves
Neuritis
Inflammation of a nerve or nerves
Neuroleptanalgesia
Combo of a neuroleptic agent (tranq/sedative) and analgesic agent to produce state of heavy sedation and analgesia (ace+ morphine)
Neuropathy
Disturbance of function of pathologic change in a nerve
Nociception
Physiological components of pain; transduction, transmission, and modulation of neural signals generated in response to a noxious stimuli. Doesn’t include perception.
Nociceptor
Specialized nerve ending capable of encoding mechanical, chemical or thermal energy into electrical impulses
Nociceptor threshold
Min. strength of stimulus that will cause a nociceptor to generate nerve impulses
Opiate/Opiod
Class of drugs derived from opium poppy, can contain opium, or are produced synthetically
Pain
Unpleasant sensory and emotional experience associted w/actual or potential tissue damage, or described in terms of such damage.
Acute pain
Pain that follow bodily injury and disappears with healing..self-limiting
Cancer pain
Pain that can be acute, chronic or intermittent and related to the disease itself or to the treatment
Chronic pain
Pain that lasts several week to months beyond expected healing time and nonmalignant in origin
Neuropathic pain
Originates from injury or involvement of the peripheral or central nervous system. Burning, shooting and associated with motor, sensory or autonomic deficits (maybe).
Pathological pain
Pain that has an exaggerated response beyond its protective usefulness
Physiological pain
Pain that acts as a protective mechanism that incites individual to move away from the cause or avoid movement.
Somatic pain
Originates from damage to bone, joints, muscle or skin
Visceral pain
Arises from stretching, distension or inflammation of viscera
Peak inspiratory pressure
Peak airway pressure obtained when using IPPV with cmH20 as unit of measurement
Peripheral sensitization
Increase in excitability and responsiveness of peripheral nerve terminals
Positive End Expiratory Pressure
Airway pressure at end of exhalation and normally O but can be positive because of weight of bellows on ventilator
Preemptive analgesia
Administration of analgesic drug before painful stimulation to prevent sensitization of neurons improving postoperative analgesia
Reflex
Involuntary, purposeful and orderly responses to stimulus
Respiratory rate
Number of breaths/min
Sedation
State of CNS depression and drowsiness including reduced awareness of surroundings
Tidal volume
Amount of gas inhaled/exhaled with each breath measured in ml
Tranquilization
State of reduce anxiety & relaxation but still aware of surroundings
Assisted ventilation
Patient sets rate and ventilator senses initiation of breath by patient and trigger delivery of tidal volume to complete cycle
Controlled ventilation
Ventilator control both rate and tidal volume
Intermittent positive pressure ventilation
Artificial ventilation in which inspirations are provided by positive pressure applied to the airways..in contrast to negative pressure ventilation (manual or mechanical)
Manual ventilation
Person manually compresses rebreathing bag to breath for patient
Mechanical ventilation
Mechanical ventilator provides respiratory support
Wind-up
Temporal summation of painful stimuli in spinal cord mediated by C fibers and responsible for second pain
PaCO2
Carbon dioxide concentration in blood
PACO2
Carbon dioxide concentration in alveolar gas
ETCO2
Carbon dioxide tension in expired air
FiCO2
Carbon dioxide tension in inspired gas
PaO2
Oxygen concentration in blood
PAO2
Oxygen concentration in alveolar gas
Vt
Tidal volume
cmH20
Unit of measure for airway pressure and central venous pressure
torr
Unit of measure for arterial blood pressure and gas tension
mmHg
Unit of measure for arterial blood pressure and gas tension
psi
Unit of measure for compressed gases in cylinder or distribution systems
What are the reasons for giving premedication?
- Analgesia
- Decrease anxiety/stress
- Sedation-chemical restraint
- Minimize autonomic reflex activity
- Decrease anesthetic maintenance dose requirements
How do anticholinergic like atropine and glycopyrrolate work?
They competitively block acetylcholine on muscarinic receptors thereby minimizing autonomic reflex activity and reducing/preventing vagal effects like bradyarrhythmias and increased salivation/secretions (this part not useful in ruminants)
How can atropine and glycopyrrolate be administered, what is their onset of action and what is the difference in their cardiac effects?
SQ, IM, or IV
3-5 min for IV and 15 min for the others
Glycopyrrolate lasts 2-4 hours while atropine is only about 60-90 minutes
How do anticholinergic drugs treat bradycardia?
They increase the rate of spontaneous depolarization in the SA node (positive chornotrope) and increase transit speed though the AV node (positive dromotrope)
What are the undesirable effects of anticholinergics?
- Tachycardia and tachyarrhythmias
- Decreased GI motility (especially in horses)
- Miosis
- Bronchodilation
T/F: Atropine and glycopyrrolate can cross the blood brain barrier and enter into the placenta.
False. Glycopyrrolate can not cross the BBB or enter into the placenta.
Which anticholinergic has more pronounced effects and is better use in emergency situations?
Atropine
Which anticholinergic is rapidly metabolized in rabbits and why?
Atropine as rabbits have an enzyme, atropinase
What are the premedication effects of anticholinergics?
They decrease autonomic reflex activity. They no not have alagesic properties, decrease anxiety, sedate, or decrease anesthetic requirements.
What types of phenothiazines/butyrophenones do we use and what do they do?
Acepromazine, Droperidol and Torbugesic
They are tranquilizer that block dopamine receptors in the basal ganglia and limbic system and the alpa 1 adrenergic receptors causing vasodilation.
Which drug is the best used in combination with phenothiazines?
Opiods
What other effects besides being a tranquilizer do phenothiazines have?
- Decrease anesthetic requirements
- Reduce indicense of some adverse effects of other drugs like acting as an antiemetic, antihitaminic, and antiarrhythmetic
How are phenothiazines administered, what is their onset and duration?
IM or IV..oral at home Slow onset (15-20min) Long duration (2-4 hours)
What affects do phenothiazines have on the body?
- Hypotension and CO reduction
- Splenic sequestration of RBC ( decrease PCV)
- Antiemetic, delays gastric emptying and reduces lower esophageal sphincter tone
- Antihistamine
- May decrease seizure threshold
- Penile prolapse in stallions
- No analgesia
What is the maximum dose in dogs for acepromazine? What is the recommended dose?
3-4mg
0.01-0.1 mg/kg
What is the discrepancy between the labeled dose of acepromazine and the clinical dose?
The labeled dose is 10x higher, so don’t do that.
When should you not use ACE?
- Neonates
- Geriatrics
- Shocky/hypovolemic patients
- Risk of hemorrhage
- Boxers
what id the most common adverse effect of giving acepromazine?
Hypotension due to alpha 1 adrenergic receptor blockage
Why would you not want to give acepromazine to a patient that you need to do skin testing on?
It is an antihistamine and will mess up the result
How do benzodiazepines work?
They potentiate the effects of GABA at the GABA receptor site which increases the frequency of CL channels opening leading to the hyper polarization of the membrane and reducing neuronal excitability.
What do we use Diazepam and midazolam in the clinical setting?
- Mild sedatives ( enhances sedation/restraint when used with opioids)
- Central muscle relaxant
- Anticonvulsant (very effective)
- It reduces the dose of injectable and inhalant anesthetics
- High safety margin
Which drugs would you use in combination sight benzodiazepines?
A2 adrenergic receptor agonistic drugs like xylazine, detomidine, medetomidine, dexmedetomidine and atipamezole and opioids
What are the important differences between diazepam and midazolam?
Diazepam is not water soluble so it doesn’t mix well with most other drugs except ketamine and it is erratically absorbed and irritating if given IM.
Midazolam is well absorbed when given IM or SQ, its compatible with many other premeds and only need to give one IM injection.
What is the onset and duration of action of benzodiazepines?
Rapid onset if IV, but midazolam is rapid following IM as well. Diazepam lats several hours while midazolam last a couple hours.
If you are premedicating a neonate or geriatric patient, would you use acepromazine or benzodiazepines?
Benzodiazepines
What is the drug of choice for emergency seizure treatment?
Diazepam
What drug can be used to reverse the effects of benzodiazepines?
Flumazenil
Why are benzodiazepines so safe to use?
They only enhance the binding capability of GABA to the alpa subunit, so they will only be effective if there is GABA available to bind. Also, the reduce cardiopulmonary effects because you don’t have to use as much of other drugs that can cause these adverse cardio effects.
Why do you not want to give benzodiazepines
alone?
They can cause paradoxical anxiety or agitation in adults
What class of controlled substances are benzodiazepines?
Class 4
How do alpha 2 adrenergic agonist work?
They inhibit norepinephrine release in the CNS (sedative), activate alpha 2 receptors on the noradrenergic neuron in the dorsal horn of the spinal cord (analgesia), and activate other alpha 2 receptors on the endothelium (vasoconstriction, hypertension).
What are the main effects of alpha 2 adrenergic?
They cause a sedative/anxiolytics effect, an analgesic effect, and cause vasoconstriction/hypertension.
Rank these alpha 2 adrenergic agonists from most alpha 2 specific to least:
- Detomidine
- Xylazine
- Romifidine
- Dexmedetomidine
- Medetomidine
- Dexmedetomidine
- Medetomidine
- Romifidine
- Detomidine
- Xylazine
How are alpha2s administered, what is their onset of action and how long do they last?
SQ, IM, IV
Rapid onset especially IM (<15min)
Dose and drug dependent duration but for analgesia, it will be shorter (15-70min), while sedation lasts longer (30-90min)
What are the main uses of alpha2s clinically?
- Sedation/chemical restraint (often in combo with opioids)
- Analgesia
What are the disadvantages to using alpha2s as a premed?
- Bradycardia with second degree AV blocks
- Hypertension due to peripheral vasoconstriction
- Hypotension following hypertension with decreased cardiac output
- Can cause hyperglycemia due to inhibition of insulin release
- Increase urine production by blocking ADH effects
- Emesis and decrease in GI motility
- Impairs thermoregulatory control
How do alpha 2 agonists compare to phenothiazines when looking at heart rate and blood pressure?
Heart rate will be lower and blood pressure will be higher (but fluctuate less) with alpha 2s. HR will be higher and BP will fluctuate more when using phenothiazines.
How would you correct a bradycardia induced by alpha 2 agonist use in your patient?
You can use an anticholinergic like atropine or glycopyrralate ONLY If the blood pressure is low or normal. The anticholinergics can potentiate hypertension without improving CO and can increase the incidence of arrhythmias.
What would you do if you patient has bradycardia and high blood pressure after administering dexmedetomadine?
Use a reversal drug like atipamizole (anti sedan), yohimbine, or tolazoline.
What is the main problem with administering xylazine to ruminants?
Potential to cause abortion (cattle) and they are super sensitive to it so you need to give 1/10 of the equine dose ( double check your calculations, 2-3mg is too much), also marked hypoxemia can occur from pulmonary edema/hemorrage (sheep)
Are alpha 2 agonists controlled substances?
NO
What is a good combination of drugs to use in the capture and restraint of wildlife?
A combination of medetomidine and dexmedetomidine, or xylazine alone
What are the main differences between medetomidine and dexmedetomidine?
Medetoidine is a racemic mixture of decor and levo rotary forms while dexmedetomidine is the dextrose rotary form only. However, they are equipotent as levo is not active.
Which alpha 2 agonists are best for sm animal versus large animals?
Sm. animal first choice is dexmedetomidine
Lg. animal first choice is detomidine
In which situation would alpha 2 agonist not sedate a patient?
A very exited animal may be refractory to sedation due to the endogenous catecholamines competing for the alpha 2 agnostic binding sites.
Which alpha 2 agonist is the longest acting and the shortest?
Longest acting is detomidine while xylazine is the shortest acting.
What do you need to keep in mind when using alpha 2 agonists with horses and brachycephalic dogs?
It can cause strider and dyspnea
What two concentrations does xylazine come in?
- 100mg/ml
2. 20mg/ml
Which reversal agent for alpha 2 agonists is best to use in ruminants?
Tolazoline, unless you want to spend the money on atipamezole
How do opioids work?
Interact with endogenous opioid receptors on the nociceptor in the CNS and peripheral nerves. This decreases cAMP which hyper polarizes the neuronal membranes via the opening of Na and Ca channels ( G-protein coupled receptors).
Which opioids are considered u agonists (used most commonly in vet med) and what are they used for?
- Morphine
- Hydromorphine
- Fentanyl
- Remifentanil
- Oxymorphone
- Methadone
Moderate to marked sedation and profound analgesia
Which u opioids are short acting? How are they administered?
- Fentanyl (15 min.)
- Remifentanil ( 5 min. )
CRI IV with loading dose or IM or typical patch
Which u opioids are long acting?
- Morphine (4-6 hrs.)
- Hydromorphine (4-6 hrs.)
- Oxymorphone
- Methadone
Which opioids are partial u agonists?
- Buprenorphine
2. Tramadol
Which opioids are agonist-antagonists?
- Butorphanol
2. Nalbuphine
What drug can reverse opioid agonist activity? and partially reverse agonist-antagonist opioids? How is it administered?
Naloxone
IM or IV
What are the main reasons we use opioids?
- Analgesia
- Sedation/chemical restraint (depends on species, drug, dose and pain state)
- Decrease dose of other drugs (usually given in combo with other sedatives like alpha 2s and phenothiazines)
How are opioids regulated?
Since they have a high potential for abuse, they are very controlled so you must maintain records of use, store them in a lock box, and have a DEA license.
What are the main adverse effects of opioid use?
- Bradyarrhythmias with sinus bradycardia or 2nd degree AV blocks
- Histamine release (morphine) especially with rapid IV injection ( causes vasodilation and hypotension)
- Respiratory depression (decrease rate and tidal volume and raise PaCO2 threshold..dose dependent)
- Emesis and defectation within few min of Sq or IM dose
- Constipation w/ chronic use
- Panting in dogs
- Can develop tolerance
- Increase pyloric sphincter tone ( u agonists)
Why would you not want to use morphine in a patient with a mast cell tumor?
It can cause histamine release
T/F: Opioids have a profound effect on CO and blood pressure.
FALSE, they can cause bradyarrhythmias though which can be treated with anticholinergics
What can high doses of opioids in horses and cats do?
It can cause excitatory effects
What is the clinical relevance of the extensive first pass metabolism of opioids?
Need a high oral dose to have effects
What schedule are U opioid agonists?
II
Which short acting U opioid must be given at a CRI? and what is this drug commonly used for?
Remifentanil
C sections in dogs
Which opioid is the only one that increases heart rate?
Meperidine, a short acting u opioid not used much in vet med
Which opioid is considered the “gold standard”? How is this drug administered?
Morphine
IV (give slowly due to histamine release)
Which opioid is good to use for an epidural , acts as an anti-enetuc,but can cause panting and respiratory changes?
Morphine
Which opioid is considered vet meds “main opioid” and why?
Hydromorphine
Rapid onset Im in less than 15 min, safe to use IV, excellent analgesic with no histamine release.
What are some problems with hydromorphine specifically? What drug would be better to use du to this problem?
It can cause hyperthermia in cats, but it is rare and easy to treat. Bette rot use oxymorphone, but its expensive and inconvenient to use
Small animal surgeons like to use __________ (opioid) because of it’s low indigence of emesis following use and lower risk of aspiration pneumonia.
Methadone
Which receptors does buprenorphine act on? What does it cause?
It is a partial agonist at the u and NOP receptor and cares mild sedation (dogs) to mile to moderate analgesia
What is the onset of action and duration time for buprenorphine?
Slow onset (30-60min) with a long duration (6-12 hours)
What is simbadol?
It is the brand name for a cat specific buprenorphine that can be sent home with clients and given SQ
How is tramadol used and what is its duration of action?
It is oral and has a long duration of action (4-6 hours)
T/F: Tramadol is not a good choice of opioid for actually pain management.
True
Which receptors does butorphanol work on and how? Which other drugs is similar to it?
It is an agonist-abtagibust opioid that is a K agonist and u antagonist which produces mild to moderate sedation and analgesia.
Nalbuphine
When would you employ neuroleptanalgesia?
When you need sedation and analgesia for minor/local procedures, for chemical restraint, or for anesthetic induction in certain patients.
What are the reasons for using fluids preoperatively?
- Anesthetics aka relative hypovolemia prevention
- Absolute volume deficit replenishment
- To maintain venous access (especially emergency situation)
What can occur if a patient is suffering from hypovolemia?
- Myocardial depression
- Vasodilation
- Blunted sympathetic nervous system responsiveness
What can cause hypovolemia in a patient?
- Dehydration
- Blood loss
- Third space loss
- Uncorrected abnormalities
- Ongoing obligatory fluid losses
What percentage of water do most animals contain? ECF? ICF?
60%
20%
40%
If you have a 50kg dog, how many liters of water is inside their body? How much of that water is ECF versus ICF? How much of the extracellular fluid is intravascular?
Body water: 50kg x 0.6 = 30 L
ECF: 50kg x 0.2= 10L
ICF: 50 kg x 0.4= 20 L
IFV of ECF = 50kg x 0.15=7.5 L
What determines how fluid is distributed from the intracellular and extracellular compartments?
The cell membrane with the Na/K ATPase pump maintaining the concentration gradient between Na and K.( More NA outside and more K inside cells )
What determines how fluid is distributed from the intravascular space to the interstitial space?
The capillary endothelium with albumin acting as the osmoles
Osmolarity
Measure of the number os similes/L of solution which is independent of the membrane
Tonicity
Measure of effective osmolarity dependent on the semipermeable membrane (hyper, iso, hypo).
Which elements concentration creates the tonicity of plasma and is the only safe/effective ormolu for extracellular administration?
Na+
Whta is the difference between osmotic and oncotic pressure?
Oncotic pressure is created by the limited movement of colloids in the vascular walls ( the colloids increase oncotic pressure) while osmoles moves freely between the vascular and extravascular space
The extracellular fluid contains high concentrations of?
Na+, Cl-, and glucose
The intracellular fluid contains high concentration of?
K+, Mg+, Phos-, proteins
Describe what hypotonic fluid, isotonic fluid, and hypertonic fluid has in it relative to osmolality of certain compounds.
Hypotonic: The sodium concentration is equal to to less than the plasma sodium concentration so will distribute throughout all fluid compartments.
Isotonic: Sodium concentration is equal to the plasma sodium concentration, so will distribute to the extracellular space
Hypertonic: Sodium concentration is higher than the plasma sodium concentration, so will increase fluids in the intravascular space (higher blood volume), redistribute throughout the extracellular space and then may draw fluid from the intracellular space into the extracellular (shrinks the cells)
What is a colloid?
A large macromolecule impermeable to capillary membranes. Examples include albumin, globulin, sugars, starches, and proteins
Colloid oncotic pressure
Colloids draw/pull water across a semipermeable membrane so if colloid stay in the intravascular space, the water will stay there raining a high colloid oncotic pressure. If there is low colloids, the water will flow out of the vasculature into the extravascular space.
Crystalloids
Fluid that contains ions or solutes that may redistribute to all fluid compartments within the body
Colloids
Fluid that contains large macromolecules that remain predominantly within the intravascular space
How are crystalloid fluids classified?
Based on their:
- Electrolyte composition
- Tonicity
- Acid-base effect (pH)
If crystalloid fluids are classified by their electrolyte composition, what are the different classifications?
- Replacement fluids
2. Maintenance fluids
What is the difference between crystalloid replacement fluids and maintenance fluids?
Replacement fluids are balanced with an electrolyte composition similar to extracellular fluid or plasma. Maintenance fluids replace electrolytes and water lost continually so have low Na+, high K and glucose ( hypotonic relative to Na+)
What are examples of replacement crystalloid fluids? Maintenance?
Replacement: Lactated ringers, plasmalyte A, normosol-R and 0.9% saline
Maintenance: Normosol M, and plasmalyte-M
What are some examples of hypertonic crystalloid fluids?hypotonic? isotonic?
Hypertonic: 7.5% NaCl
Isotonic: Lactated ringers
Hypotonic: 0.45% NaCl
What are some examples of crystalloid fluids that are acidifying? Alkalinizing?
Acid: 0.9& NaCl
Alkaline: LRS, Normosol, plasmalyte
Which two rotes of fluid administration are only possible during anesthesia?
- Intraosseous,
2. IV
What are the fluid maintenance rates for anesthesia for dogs, cats and large animals?
Dogs and Lg animal: 5 ml/kg/hr
Cat: 3ml/kg/hr
What are the shock dose rates for dogs,cats and large animals?
Dogs: 90 ml/kg/hr
Cat: 60 ml/kg/hr
Lg animal: 45 ml/kg/hr
When giving a fluid bolus, what is the shock rate dose for 15 minutes in dogs, cats and large animals?
Dog: 20ml/kg
Cat: 15 ml/kg
LA: 10ml/kg
With high potassium containing fluids like normosol M and plasmalyte-M (maintenance fluids), what is the recommended max rate and why?
0.5 mEg/kg/hr
Usually only used in a ICU situation
K+ is cardiotoxic at high rates
What are some examples of natural colloid fluids?
Whole blood, plasma and packed RBC but only if resuspended in a colloid
What are some examples of synthesis colloid fluids?
Dextrans, hetastarch, pentastarch and bovine hemoglobin
glutamer
Where are the main side effects of colloid fluid use?
- Coagulapathy
- Renal failure
- Congestive heart failure
- Anaphylaxis
What is the typical colloid administration rates for dogs, cats and LG animals?
Dog: 10-20 ml/kg/24 hr
Cat: 5-10 ml/kg/24hr
LG animal: 10-20 ml/kg/24hr
All for a max of 3 days
When would you want to use blood products?
When the PCF < 20% and/or the TPP (total plasma protein) < 4 gm/dl
What do you do if you are supplying blood products during surgery and you noticed hypotension, urticaria, facial swelling and changes in the HR, RR temp, Hct, serum colors or ECG changes?
The animals is probably having a blood transfusion reaction so you need to stop the transfusion and give steroids.
What are the overall blood transfusion rates for the test dose, maintenance and the maximum?
Test: 0.25 ml/kg over 15 min
Maintenance: 5-10 ml/kg/hr
Max: 22-30 ml/kg/hr
If the patient is bleeding out, give them all you can give!
What factors influence the injectable anesthesia drugs effect?
- Blood volume
- Speed of injection
- CO
- Lean body mass vs. fat body mass
What is TIVA?
Total intravenous anesthesia protocol: A combination of an analgesic, sedative and muscle relaxant for anesthesia
What is the theraputetic index of a drug and what does it mean?
It is the LD50/ED50 and the larger the number, the safer to drug.
Which drugs are considered dissociative anesthetics?
- Ketamine
2. Tiletamine with zolazepam in telazol
How are dissociate anesthetics administered?
IM or IV ..sometimes oral/mucosal
How do dissociative anesthetics work?
Interact with multiple receptors wishing the CNS to produce analgesic and anesthetic effects (
What is the onset and duration of dissociates?
Rapid IV onset (30-45 s)
Rapid to moderate IM onset ( 2-10 min..ketamine is slower than telazol)
Duration is 15-30 min and is dose dependent
What effects do dissociates have on the body of the patient that we want to watch out for?
- Increase HR, CO, and BP
- Apnuestic ventilatory pattern
- EEG activity that resembles a seizure with increased intracranial pressure and intraocular pressure
Why is the anesthetic state when using dissociates “different” than other anesthetics we use?
The patient can swallow, blink, lacrimal, salivate and has poor muscle relaxation
Which drugs do we typically combine dissociates with?
- Benzodiazepines
- alpha 2 adrenergic agonists
- Acepromazine
- Guaifenisen
T/F: Using ketamine is a cat with renal issues is safe.
False, don’t use it.
Which is the most common induction drug in large animal medicine?
Ketamine
How do barbiturates work?
Indirectly or directly ( depends on dose) activate the GABA receptor with low doses providing a sedative/hyponotic effect and high doses having an anesthetic effect
What are commonly used barbiturates
in veterinary medicine?
- Thiopental
- Pentobarbital
- Phenobarbital
Which drug is the drug of choice for long term suppressing of seizure activity?
Phenobarbital
Which drug do we typically use for euthanasia?
Pentobarbital
Which injectable anesthetic can cause bigeminy, moderate hypotension and splenic engorgement?
Thiopental
What are the pain reasons fro using barbiturates?
It is a sedative at low doses and a anesthetic at high doses, but it has no analgesic effect
Why is the recovery of thiopental rough? For which particular species is this more of an issue?
It becomes very concentrated in the body tissues especially the vessel rich group, plus it undergoes hepatic metabolism.
Sighthounds dogs can have 6-8 hour long recovery instead of 30 min.
Why does thiopental cause perivascular necrosis and how would you treat it?
It is very basic. You would dilute the area with saline at least 5x the infected volume, maybe some lidocaine and anti-inflammatory agents added too.
Which type of propofol would you want to use in cats? Propofol or propoflo28?
Propofol, because propofol28 contains benzyl alcohol which may be toxic to cats
How does propofol work?
It potentiates GABA activity at the GABA receptor and decreases cerebral metabolic rate
Which drugs are cumulative, ketamine or propofol or etomidate?
Ketamine, so it is not suitable for CRI
If thiopental or propofol have a faster onset of action?
Thiopental
How long does propofol last?
6-8 minutes
What are the main adverse effects of using propofol?
- Dose dependent hypotension due to vasodilation
2. Apnea especially if induced fast
How much propofol and how fast should you give?
4mg/kg every 15-20 seconds
What affects does propofol have on the CNS?
It decreases intracranial pressure and cerebral metabolic as well as intraocular pressure. It also is an anticonvulsant.
Would you want to use propofol as an analgesic?
NOPE
With which injectable anesthetic are you most likely to see foreleg muscle rigidity?
Propofol
What can propofol do to cats if used repeatedly over several days?
Heinz body anemia
What is the drug of choice for anestisizing a patient with a significant cardiovascular disorder? Why?
Etomidate
It doesn’t cause cardiovascular or respiratory depression
Why would you not want to use etomidate as a injectable anesthesia in a patient?
- Myclonus
- Regurgitation/vomit at induction
- Rough induction/recovery
- Adrenocortical suppression
- Hemolysis
- Expensive
Which drugs would you want to use in conjunction with etomidate?
- Benzodiazepine
2. Some other premed
What is alfaxalone made of?
2-hydrozypropyl-b-cyclodectrin (HPCD) which is a molecule that does not release histamine and has a wide margin of safety.
What class of narcotic is alfaxalone labels under?
Class 4
How does alfaxalone work?
It selectively modulated Y-aminobutryic aside (GABA) and sedates the patient due to the CL- ions flooding into the cell.
T/F: Alfaxolone can be administered IM SQ, and IV, while propofol can only be administered IV.
True!
How long are you supposed to keep alfaxolone and propofol around on the shelf and how long do we actually keep in on the shelf for?
6 hours
24 hours
Although alfaxolone is labeled for dogs and cats, what other species can it be used in?
- Horses
- SM ruminants
- Rabbits
- Pigs
- Alpacas
Would you be able to give a big dose of alfaxalone? Why?
Yes, it has a wide margin of safety and only has mild cardiopulmonary depressions affects.
What are the disadvantages to using alfaxalone?
- Expensive
- Controlled
- Short shelf life
- Its concentration may limit usefulness
What type of patients would be best to use inhalant drugs with to induce?
Very young/small, exotics, birds, neonatal foals
What are the two main types of muscle relaxants and give examples of each.
- Central: Benzodiazepines and guaifenesin
2. Peripheral: Succinylcholine, atracurium and cisatracurium
Why and when do we use guaifenisen?
You can use it to induce large animals along with ketamine or thiopental. It can also be used in a triple drip with ketamine and xylazine (useful for CT’s or castrations)
How long should you use a triple drip- GKX?
60-90 minutes otherwise recovery will go to shit
Along with thiopental, what other injectable anesthetic can cause severe tissue necrosis when administered extravascularly?
Guaifenisen
Why do we use non-depolarizing neuromuscular muscle relaxants when dealing with ophthalmology issues?
Under inhalent anesthesia, the globes go into a ventral medially position, so drugs like cisatracurium moves the globes back into the center so you can do surgery on them.
Why do we not use succinylcholine do castrate horses anymore?
There is no analgesic component to this depolarizing neuromuscular blocker. It only paralyzes the patient, so this is considered malpractice.
How do non-depolarizing neuromuscular blockers work?
They interfere with Ach binding to nicotinic receptors and prevention depolarization. They can be reversed with acetylcholine esterase drugs.
Do central or peripheral muscle relaxants cause paralysis?
Peripheral, especially depolarizing ones like succinylcholine.
What is the goal during anesthesia when it comes to MAP and SAP?
We want MAP to be maintained above 70 mmHg and SAP to be above 90 mmHg
What is the most common complication during general anesthesia? How do we treat it (name the four steps)
Hypotension
- Stabilize rate/rhythm
- Fluids
- Anesthetic Depth
- Inotropic support
Which drugs most commonly cause bradyarrythmias?
- opioids
2. alphas 2 agonists
Would you want to give an anticholinergic if the patient has a normal HR and is hypotensive?
No, they can make it worse and cause tachycardia
What is the predominate effect of alpha 1 adrenergic receptors?
Vasoconstriction in the peripheral vasculature
What is the predominate effect of beta 1 adrenergic receptors?
Positive inotropy/chronotropy of the heart
What is the predominate effect of beta 2 adrenergic receptors?
Bronchodilation
At what point does the SpO2 have to drop for the PaO2 to start dropping significantly?
95%
What are the five causes of hypoxemia?
- Decreased FiO2
- Hypoventilation
- Diffusion impairment
- Ventilation/perfusion mismatch (V/Q)
- Intra and extra pulmonary shunting
How would you calculate the amount of Bicarb to give a patient that was suffering from metabolic acidosis?
mEq HCO3-=BW (kg) x BE x 0.3
