SGU SVM Anesthesia 2 Flashcards

cerebral blood flow
Terms Definitions
Which class of drug is the oldest injectable anesthetic?
Barbituates
Which barbituate is on of the few available today in vet med?
Thiopental
In solution, thiopental is highly alkaline, what effect does this have on tissues?
Highly irritant if extravasated
What is the mechanism of action of barbituates?
Depresses the RAS in the brainstem responsible for wakefulness, interacts with GABA
Which is the active portion of a barituate...the protein bound or unbound?
The unbound is active
Thiopental is up to 40% unionized in plasma, making it lipid soluble. In this form, what can the drug do?
Cross the blood brain barrier
What biochemical condition will increase the intensity of the barbituate effect?
Acidosis
Is recovery from a drug due to metabolism or redistribution?
Redistribution
In which breeds should Thiopental be avoided?
Sight hounds (low body fat = lack of depot for the drug)
How quickly does Thiopental take effect?
One arm-brain time...unconsciousness in 30 seconds
What effect does Thiopental have on intracranial pressure?
Lowers it
What are the CVS effects of Thiopental?
Cardiovascular depression, vasodilation, drop in output. arrhythmogenic
What respiratory effect is usually seen post induction?
Apnea
What caution must be taken with preparing Propofol?
Contains no preservative, can grow bacterial
What is the mechanism of action of Propofol?
Enhances GABA activity, enhances NMDA activity
What effect does Propofol have on intraocular pressure?
Reduces it
What are Propofol shakes?
Some animals can develop muscle rigidity and spasm following induction. responds to Ketamine
Does Propofol raise the seizure threshold?
No, used as an anti-convulsant in dogs with refractory epilepsy
What are the CVS effects of Propofol?
CVS depression, vasodilation, decreased aterial blood pressure, stroke volume and cardiac output Little effect on heart rate
What are the respiratory effects with Propofol?
Respiratory depression
How can the pain of injecting Propofol be reduced?
Draw blood back into the syringe prior to injection, use a low dose of lidocaine
Do pigs require higher or lower doses of Propofol?
Higher
What caution should be taken when using Propofol in cats?
Prolonged recovery if used as CRI
Which neuroreactive anesthetic agent is not yet licensed in the US?
Alfaxalone
What is the mechanism of action of Alfaxalone?
Enhances inhibitory effects of GABA, acts on central glycine and nicotinic Ach receptors
Alfaxalone has CVS effecst similar to what agent?
Propofol
In which species is Alfaxan not used?
Dogs, histamine release
Name the 2 common dissociative drugs used in vet med
Ketamine, Tiletamine
Ketamine is usually co-administered with what other class of drugs?
Rarely given alone, usually given with BZ, ACP, A2 agonist
What is the mechanism of action of Ketamine?
Unclear. Believed to be a result from inhibition of excitatory neurotransmitters
What is the name of the Ketamine metabolite formed in the liver?
Nor-ketamine
What is a disadvantage of Ketamine in terms of recovery?
Usually an unpleasant recovery
What are the CNS affects of Ketamine?
-increased cerebral blood flow -increased cerebral O2 consumption -increased intracranial pressure -epileptogenic -good analgesic -increases muscle tone
What ocular effects are seen with Ketamine?
-eyelids remain open (use eye gel) -increases intra-ocular pressure -dilated, centrally fixed pupils
What effect does Ketamine have on the CVS?
Stimulates the CVS, indirect sympathomimetic action
What are the respiratory effects of Ketamine?
Minimal respiratory depression Pharyngeal/laryngeal reflexes maintained Apneustic breathing Hypersalivation
What are some conditions that contra-indicate the use of Ketamine?
-increased ICP -hepatic, renal disease w/ obstruction -risk of seizure -increased intra-ocular pressure
How does Tiletamine compare to Ketamine?
Similar in action, but more potent and a longer duration of action
What are the common uses for Tiletamine?
-aggressive dogs, feral cats -horses, pigs, exotics
What is the advantage of using Etomidate?
Has minimal CVS depressant effects, minimal effects on the sympathetic nervous system and barorecptors
What is the effect of Etomidate on the adrenals?
Temporary adrenal suppression
What is TIVA?
Using drugs in combination as a continuous IV infusion to maintain anesthesia when an inhalational agent is not desirable or possible
What are the properties of the ideal drugs for TIVA?
non cumulative -rapidly metabolized -non irritant -no undersirable properties from long administration
What is an example TIVA technique used in equine medicine?
Triple drip...Guaphenesin, ketamine and xylazine
In which breeds do you avoid Thiopental?
Sight hounds
What issues are associated with brachycephalic dogs and inducing anesthesia?
-stenotic nares
-elongated soft palate
-braod, thick muscular tongue
-narrow laryngeal opening, everted saccules
All of the physical issues with brachycephalic dogs place them at risk for what?
Respiratory obstruction
Which dog breeds are more sensitive to ACP?
Boxers, giant breeds, setter
What effect can opiois have on sled dogs?
Dysphoria
In older dogs (5-10 years), what pre-anesthesia lab work should you perform?
Assessment of renal function
When would you preform a complete biochem profile prior to anesthesia?
Older animal, elective procedure of more than 30-40 minutes
If a breed is associated with a coagulation problem, what test should you perform?
BMBT
(Doberman, corgi)
In a diabetic animal, what level would you check just prior to anesthesia?
Glucose
Sedation can be thought of as what?
Heavy pre-mediation
Sedation is usually a combination of a tranquillizer and an opioid. This combination is called a what?
Neurolepanalgesic
What is the purpose of sedation vs anesthesia?
Allows for relatively non-painful procedures or manipulation with the need for GA.
What are the default drugs for sedation in a dog?
ACP plus morphine
In what cases would you reduce the amount of ACP given?
-sensitive breed (Boxer)
-older animal
-older, sensitive
-when prolonged sedation is not wanted
When using the IV route instead of the IM route for sedation, by how much is the dose decreased?
one-half
When would ACP not be used?
-hypovolemia, shock or hypotension
-skin testing
-impaired liver function
When might the morphine dose be increased for sedation?
-aggressive, boisterous temperament
-increased potential pain
-if a lower dose of ACP is used
When would morphine not be used for sedation?
-concerned about vomiting
-not a painful procedure
-don't want prolonged sedation
-skin testing (histamine release)
-certain breeds can react (sled dogs)
What sedative would you used for an aggressive dog?
Medetomidine
By which route is it best to administer pre-med drugs?
IV- allows accurate titration
As a premed, Thiopental should be given in a concentration of 2.5% max. Why?
To reduce the risk of arrhythmias or perivascular slough
When would you not use Thiopental?
-hypovolemic animals
-liver, kidney, heart dz
How is Propofol administered?
Slow IV to effect
Giving Propofol too quickly can induce what?
Apnea
During induction with Propofol, what side effect might you seen?
Muscle twitching
What other pre-med drug has similar effects to Propofol?
Alphaxalone
Why would you choose Etomidate as a pre-med?
-preserves cardiac function
-minimal respiratory depression
What are the drawbacks to Etomidate?
-pain on injection
-high incidence of nausea & vomiting
Which combination of pre-med drugs are very unpleasant and can cause dysphoric recoveries in dogs?
Diazepam/Ketamine
Diazepam/Ketamine should be avoided in which situations?
Animals at risk of seizuring or with increased CSF pressure
What is the last choice method for induction in dogs?
IM- medetomidine-xylazine plus ketamine
When would sevoflurane be the inhalational agent of choice in dogs?
For mask induction
Halothane should be avoided in dogs with what conditions?
-CV dz
-cardiac arrhythmias
-hepatic/renal dz
-IICP
If using nitrous oxide, what must you monitor?
Oxygenation- at least with pulse ox
When do you extubate a dog?
When he starts to swallow
What are the default pre-meds given to cats?
ACP plus morphine IM or SC
For fractious cats, what drug could you add?
Ketamine
What adjustment would you make to the ACP dosage in older cats?
Lower it
When would you decrease the dose of morphine in cats?
Old and quiet cats, cats with impaired liver function
When should morphine not be used in cat anesthisia?
When skin testing is the procedure
What other opioid works well in cats?
Buprenorphine
Why do some vets give atropine to cats?
To reduce salivation caused by ketamine
When would you give a high dose of ketamine to a cat?
-young, bouncy cat
-nasty/aggressive cat
As a last result, in dealing with an agressive cat, what pre-med drug could you give?
Ketamine- PO
When would you not use Ketamine in a cat?
-older, quiet cat
-quesitonable liver/kidney function
-urethral obstruction
-risk of seizure
Compared to dogs, the induction dose of propofol needs to be higher or lower?
Higher induction dose
During intubation of a cat , how could you reduce the occurrence or laryngospasm?
Apply lidocaine to the larynx
What triad of signs should you watch for in cats?
Hypotension
Bradycardia
Hypothermia
What are inhalational anesthetic agents?
Drugs that reach the circulation by the respiratory system
How are these drugs absorbed into the bloodstream?
Via the capillaries
What is saturated vapor pressure?
The equilibrium point for a vessel containing a volatile liquid, at a specific temp, where the number of molecules entering the gaseous phase equal the number of molecule leaving it
What is a partition coefficient?
The relative affinity that 2 tissues (or phases) that are in contact with each other have for the same substance.
What does a partition coefficient greater than 1 mean?
That the FIRST names tissue is going to hold more of the substance
The ratio of the amount of anesthetic dissolved in blood and in gas is called what?
Blood-gas solubility coefficient
Does a soluble inhalational agent have a large of small blood-gas coefficient?
Large
As a general rule of thumb, what type of inhalational agent works faster?
A more insoluble agent
The extent to which any tissues take up an anesthetic agent depends on its what?
Blood supply and size
Based in perfusion and proportion of body mass, the body can be divided into what 4 basic groups?
-vessel-rich
-muscle/skin
-fat
-vessel poor (connective tissue etc)
Of the four body groups of tissue, which one has the highest perfusion (as a % of cardiac output)?
Vessel rich tissue
The vessel-rich groups is composed of which tissues?
-brain
-heart
-liver
-kidneys
-endocrine glands
-splanchnic bed
When will uptake of an inhalational agent stop in a particular tissue?
When the tissue is saturated
Which is the first tissue to saturate?
Brain- small volume, high affinity, well perfused
What is MAC?
The minimum concentration of an anesthetic agent(measured at the alveolus) which will prevent purposeful movement in response to a supramaximal (painful) stimulus, in 50% of patients
MAC is a way of comparing what, across agents?
Potency
Is a lower MAC more or less potent than a higher MAC?
More potent
How would you monitor the MAC during anesthesia?
Expired, or end tidal, concentraions are a close approximation
What factors can decrease a MAC?
-narcotics, sedatives, tranq
-nitrous oxide
-age (old animals & neonates)
-hypothermia
-pregnancy
-severe hypoxia
-sever hypercapnia
-hypotentsion
What factors can increase MAC?
-hyperthermia
-neurotransmitter release
What is the approximate MAC of
Halothane
Iso
Sevo
Des?
H = 0.8-0.9
I = 1.5
S = 2.4
D = 8
How do you tell the amount of remaining nitrous oxide in a cylinder?
Weigh it
Under which conditions would you not use N2O as an anesthetic agent?
Head trauma or cerebral edema
(raises cerebral blood flow of ICP)
Compared to other inhalational agetns, N2O is the only one that has what additional property?
Analgesia
What effects does N2O have on the CVS?
-mild sympathetic stimulation (maintains BP, HR, CO)
N2O has min respiratory effects. At 100% it is lethal, never use a flow greater than what?
66%
How is N2O eliminated?
Through the lungs
What is the difference between the use of N2O in animals compared to humans?
N2O is only half as potent in animals
What are the benefits of using N2O?
-accelerates uptake of volatile anesthetics via second gas effect
-good analgesia
-decreases amount of inhalation agent needed to maintain plane
What are the disadvantages of nitrous oxide?
-low potency
-expensive
-potential for human abuse
-potential for hypoxia if wrong conc. given
-potential for diffusion hypozia at end of anesthesia
N2O can reduce the MAC of other inhalational agents by how much?
20-25%
What is the danger is using N2O in terms of gas-filled spaces?
N2O has low solubility and can diffuse into gas filled spaces such as the rumen, a GDV, pneumothorax and cause increased pressure
At the end of anesthesia with N2O, how do you avoid diffusion hypoxia?
Administer O2 for 5-10 mins following the cessation of N2O
What is the special storage requirement for Halothane?
Unstable in UV light- stored in a dark bottle
Halothane has what added to it as a preservative?
Thymol
Why is Halothane the most dangerous inhalational agent to use in animals with head trauma or suspected brain tumors?
Increases cerebral blood flow and decreases cerebral metabolic rate
What are the CVS effects of Halothane?
-dose-dependent CVS depression
-direct myocardial depression
-decreases stroke vol, CO, BP
-arrythmogenic
What are the respiratory effects of Halothane?
Dose-related respiratory depression
How does Halothane depress hepatic function in animals?
Decreased hepatic perfusion associated with decreased cardiac output
Halothane undergoes more metabolism in which organ than any other inhalational agent used in vet med?
The liver
What effects does Halothane have on the Gi system?
-reduces GIT motility
-reduces splanchnic blood flow by up to 33%
What other effects does Halothane have?
-profound relaxation of uterine muscles
-relatively poor skeletal muscle relaxation
Does Isoflurane require a preservative?
No
Should Isoflurane be used in the case of head trauma?
Yes, increases cerebral blood flow less than Halothane
Does Isoflurane cause CVS depression?
Yes, but by a different mechanism than Halothane
What kindof myocardial effect does Isoflurane have?
No direct myocardial depression
Isoflurane causes vasodilation which has what effect on blood pressure?
Hypotension
What are the respiratory effects of Isoflurane?
-respiratory depression
-irritant to upper airway
What effects does Isoflurane have on hepatic and skeletal blood flow?
hepatic- well maintained
skeletal- increased
What is compound A?
Some degradation of Sevoflurane occurs when exposed to CO2 absorbent, poducing compound A which has been shown to be nephrotoxic in rats
Sevoflurane has similar effects to Isoflurane. What are the CVS effects of Sevoflurane?
-CVS depression due to vasodilation
-does not sensitize the myocardium to catecholamines
Desflurane requires what special equipment?
A heated vaporizer
Is the MAC of Desflurane higher or lower than other agents?
Higher- but with high SVP and BP, easy to achieve
What do muscle relaxant drugs do?
Act to modify the activity of the post-synaptic muscle membrane and thus produce muscle relaxation
What level of sedation and analgesia do muscle relaxants provide?
When are NMBD's used?
-intra-ocular surgery
-reduces surgical traction and post op discomfort
-may facilitate intubation and IPPV
-predictable total relaxation
-non-depolarizing drugs can be antagonized
Which surgical procedure is it often truly necessary to use NMBDs?
ocular surgery
Neuromuscilar blockade may alos be used on high risk cases such as....
-thoracotomy
-diaphragmatic hernia repair
-laparotomy
-othro sx
-ear sx
What are some disadvantages to using NMBDs?
-controlled ventilation is essential
-difficult to monitor anesthesia & analgesia
-no motor response to stim- can cut a nerve
-monitoring neuro blockade is complex
-recurarisation
What are the 3 essential prerequisites of using NMBD's?
-ensure unconsciousness
-ensure adequate analgesia
-ensure ventilation support
What are the absolute contraindications of using NMDB's in animals?
-inability to ventilate the animal
-inability to provide adequate anesthesia and analgesia
Muscle paralysis follows what pattern?
From periphery to centrally- face and tail first, diaphragm last
return of function is opposite
After paralysis with an NMBD, what autonomic response should you look for?
-mydriasis
-lacrimation
-salivation
-tachycardia
-hypertension
-arrhythmia
-paradoxical jaw tone
-paradoxical jaw twitching
What is the preferred method for monitoring the use of a NMBD?
Peripheral nerve stimulator
if monitoring the effects of a NMDB by clinical signs, what do you look for?
-head lift
-cough
-squeeze
-inspiratory force
Name the 3 centrally acting muscle relaxant drugs
-Guaifenesin
-Benzodiazepines
-A2 agonists
Guaifenesin is usually mixed with other anesthetic agents for which species?
Horses
Where is the effect of Guaifenesin?
Block transmission of nerve impuleses at the internuncial neurons of the spinal cord, brainstem and subcortical areas
What effect does Guaifenesin produce?
Tranquillization, ataxia and recumebency, no analgesia
When is Guaifenesin used?
Induction of anesthesia in horses and cattle
TIVA (w/ Ketamine and Xylazine) triple drip
When has Guaifenesin been used in dogs?
To treat tetanus
Cattle are sensitive to a risk of hemolysis, what concentration of Guaifenesin is used?
Never more than 5%
What GGE should be used in horses?
Never more than 10%
Along with the centrally acting NMBD, name the 2 other types used?
Depolarizing
Non-depolarizing
How are the depolarizing drugs (suxamehtonium) broken down?
By pseudocholinesterases
The non-depolarizing agents include which drugs?
-Vecuronium
-Rocuronium
-Atracurium
The non-depolarizing NMDB are structuarlly related to what drug?
ACh
How do the non-depolarizing NMDB's work?
By competitive block, compete with ACh the the nicotinic ACh receptors
How is a neuromuscular blockade with a non-depolarizing drug reversed?
With anticholinesterases
What is the onset of action in a dog given Vecuronium?
3 minutes
In terms of cardiac effects, why is Vercuronium a good choice for a NMBD?
Excellent Cv stability, wide spearation between vagal and neuromuscular blocking doses
Rocuronium has a duration of action of how long?
30 minutes
Which NMBD is used in dogs, cats and horses?
Atracurium
Atracurium is the NMBD of choice in which type of patient?
Critically ill..has rapid recovery and used in patients with renal and hepatic disease/failure
Which category of NMDB's are reversible?
Non-depolarizing
Vecuronium, atracurium
What is the timing for giving a reversal agent?
Only when there are clinical signs or evoked signs of spontaneous recovery
In dogs and cats, what drugs are given to reverse NMDBs?
Anticholinesterases and an antimuscarinc (to protect against the muscaric effects of the build up of ACh)
When reversing an NMDB in a horse, is atropine also given?
No
Name the 2 anthicholinesterase drugs.
-Neostimine
-Edrophonium
How do anticholinesterases work?
Stop the breakdown of ACh in the region of the muscle plate, the increase in ACh can then compete for the receptors and replace the NMBD
In the absence of a peripheral nerve stimulator, how do you know that the reversal of a NMDB is complete?
Good jaw tone
Brisk palberal reflex
What is the "fish eye" sign?
Animal is still not completely reversed
When using a nerve stimulator, what is the most popular stimulation pattern used to check for nerve response?
Train of Four
What is the amount of nerve blockage as demonstarted by a train of four pattern that shows 1 twitch?
90% block
What is a common method of performing surgery on a ruminant?
Standing
A caudal epidural is used in a cow for what purpose?
Surgery of the tail, anus, vagina and perineum. Prevents rectal straining during calving
Replacement of prolapsed uterus
What is the effect of a caudal epidural on the uterine motility and locomotor function of the hindlimbs on a cow?
Unaffected
Where should the approach for a caudal epidural be made?
Between Cd 2 and Cd3
What drugs can be used for the caudal epidural?
Lidocaine
Xylazine
What local anesthetic technique can be used during flank surgery- c-section, abomasal surgery?
Inverted L-block
Where is the anesthetic agent injected for an inverted L block?
Below transverse process of lumbar vertebrae
What other type of flank procedure anesthesia can be used?
Paraverterbral anesthesia
The nerves for a paravertebral block are located where?
T13, L1, L2
What are the 2 approaches to a paravertebral block?
Dorsal
Lateral
What are the signs of a successful lateral paravertebral block?
-Anesthesia of the skin, peritoneum & musculature of the flank, increased skin temp and scolisos towards the desensitized side
Whay arent line blocks recommended for C-section?
-distortion of normal tissue architecture
-incomplete anesthesia
-incomplete muscle relaxation of dep players of abd muscle wall
-formation of hematomas along site
-increased cost- large doses
What anesthetic technique is used for digital surgical procedures in large ruminants?
Intravenous regional analgesia
In cattle and sheep, dehorning is achieved using what kind of anesthetic procedure?
Cornual nerve block
Which approach to horn nerve block is taken?
Cornual branch of the lacrimal nerve
In goats, which additional nerve needs to be blocked for dehorning?
Medial cornual branch of the infratrochlear nerve
In goats and large ruminants what other block should be done?
Ring block around the horn base
What is a good sign of a successful zygomaticotemporal nerve block?
Eye blink during administration
Drooping of upper lid after
Which nerve, in a ruminant, is blocked to paralyze the eyelid (without analgesia)?
Auriculopalpebral nerve
Why would you block the Auriculopalpebral nerve?
Removal of FB (in combo with local anesthetic
What 2 neve blocks are used for procedures on the eye?
Retrobulbar
Peterson's block
Which solution strength of Xylazine should be used in cattle?
2%- extremely sensitive
A higher dose of Xylazine increases the risk of what?
Recumbency
In which situation should Xylazine not be used in cattle?
Last trimester of pregnancy
For diffcult ruminants, what drug can be used?
ACP
What drug can be given with Xylazine or ACP if you don't want the cow to go down?
Morphine
What type of regurgitation can occur in a cow during induction?
Active regurgitation
During surgery what type of regurgitation can occur?
Passive
During ruminant surgery, what can cause bloat?
Accumulation of CO2 and methane in the rumen, not able to eructate
What effects will increasing abdominal pressure have?
Impair repsiration and venous blood return to the heart
When will the ability to eructate return?
When the animal is in sternal recumbency and in an advanced stage of recovery
What complication can occur during ruminant anesthesia in regards to saliva?
Ruminants produce a huge amount of saliva, during anesthesia the swallowing response is suppressed, saliva accumulates- can cause upper airway obstruction
Hypoventilation during anesthesia can occur due to....
-central depression
-V/Q inequalities due to recumbency
-low chest wall, lungs difficult to expand
-more impedence due to diaphragm position
-expanding rumen puts pressure n diaphragm
How are complication minimized during ruminant anesthesia?
-starvation 12-18 hrs prior
-with hold water 12 hours
-keep head elevated intubate asap
-adequate depth
How can the possibility of bloat be lowered?
With hold highly fermentable food for 24 hrs
Should atropine be give in cattle to reduce saliva production?
No, just makes saliva more viscous
What premeds are used in cattle?
none
IV access is best given where?
Auricular vein
What drugs for induction should be the first choices?
Ketamine/diazepam
What drugs comprise the triple drip?
GGE-Ketamine-Xylazine
What percentage of GGE should be mixed with Ketamine for triple drip?
5%
Why should you provide supplemental O2 when using triple drip in a cow?
associated with marked hypoxemia and respiratory depression
Entubation of an adult cow is performed how?
Blindly
Maintenance of anesthesia of a cow is achieved by using which inhalant?
Iso or Halothane
What is the position of the eyes during deep anesthesia of a cow?
Central
What are sings of a lighter plane of anesthesia?
Chewing and swallowing
In which position should the cow be placed for recovery?
Sternal recumbency and supported
To which class of drugs are goats extremely sensitive?
A2 agonists
Even at very low doses, what side effect can xylazine cause in sheep?
Pulmonary edema
How can the risk of pulmonary edema in sheep be reduced?
Give IM
Whcih drug, unlicensed in sheep and goat, can give a moderate to deep sedation?
Medetomidine
ACP given at what level of dose can provide sedation?
Low levels
Which class of drugs has less CV depression than A2 agonists in sheep and goats?
Diazepam
A combination of Xylazine, Buprenorphine and what else can be used as cattle induction.
Ketamine and diazepam
Are llamas ruminants?
No strictly...have a 3 compartment stomach
Where is the best place to start an IV in a llama?
Right jugular, high up
Why might it be difficult to place a venous catheter?
Veins have valves
What length of ET tube is needed for llamas?
35-40 cm
What is a good alternative to orotracheal entubation?
nasotracheal
What premed is used for llamas?
Xylazine
Opioids for analgesia or sedation
What induction drugs can be used?
Xylazine
Telazol
Propofol
How should the llama be maintained under anesthesia?
Small camelids are sensitive to inhalants, use ketamine to reduce the need
What is CPCR?
Cardiopulmonary Cerebral Resuscitation
The classic features of arrest include what signs?
-absence of ventilation/cyanosis
-absence of palpable pulse
-absence of heart sounds
-dilated pupils
At what pressure does femoral pulse disappear?
systolic < 60mm Hg
At what pressure do heart sounds disappear?
Systolic < 50mm Hg
In contrast to humans. cardiac arrest in animals is usually the result of what?
A non-cardiac condition
-anesthetic overdose
-primary cardiac disease that affects other organs
-dz of respiratory system
-systemic dz
Being prepared to handle arrest means identifying high risk patients. which includes what conditions?
-vagally mediate cardiac arrest
-anesthetic overdose
-trauma
-systemic/metabolic disease
-hypothemria
-respriatory dz
-cardiac dz
-acid-base abnormalities
In which species can vasovagal response primarily occur?
Brachycephalic
Boxers have enhanced parasympathetic tone combined with withdrawal of sympathetic tone...this usually manifests as bradycardia. What drug should you give?
Atropine..NOT adrenaline
What are the warning signs of a possible impending cardiorespiratory arrest?
-changes in resp rate, depth, pattern
-weak, irregular pulse, bradycardia
-hypotension
-unexplained change in depth of anes
-cyanosis
-hypothermia
CPCR consists of what 3 major components?
-Basic life support (chest compression and artificial vent)
-Advanced life support (+ drugs)
-Post -resuscitation care
Extended hypoxia can lead to brain damage which usually manifests how, in a dog?
Blindness
What is the first step you take during an arrest?
Call for assistance
What are the ABC's of treating an arrest?
Airway
Breathing
Circulatory support
Advanced life support includes what steps...D-E-F?
Diagnosis and drugs
ECG
Fabrillation
G-H-I of prolonged life support means what?
Gauging response
Hopeful measures for brain
Intensive care
How many people are needed to competently perform CPR?
4
CPR will rarely be successful if there i no response after how much time?
15 mins
After turning off the inhalant, how many breaths do you give per minute?
10-15
Which acupuncture point may help reverse respiratory arrest?
Jen Chung GV26
If femoral pulse is low or weak, systolic must be what?
< 80 mm Hg
What are the 2 choices for chest resuscitation?
Closed compression
Open massage
In which position is the patient for closed chest compression?
Left lateral or dorsal recumbency
How many compression per minute should be given?
100-120
In cats and small dogs., where do you compress?
Directly over the heart
Where do you perform compressions on a large dog?
Widest part of thorax
Lateral recumbency for chest compression is used on animals of what size?
Over 7kg
Cardiac compressions should be interspersed with what other compressions?
Abdominal
Through what 2 mechanisms does closed chest compressions produce flow?
-direct cardiac pressure (cardiac pump)
-pressure gradient (thoracic pump)
Closed chest compression achieves a cardiac output of how much?
20%
To perform open cardiac massage a thoracotomy is performed where?
Left lateral thorax between 4-6 ICS
What is the advantage of open massage?
Does not raise atrial pressure, provides better cerebral and coronary perfusion
Monitoring during CPR is essential and should include what?
-MM, CRT, cranial nerve reflex
-CNS
-peripheral and central pulses
-capnography
-pulse ox
-ECG
If needed, Doppler could be performed where to assess bloodflow?
On the cornea....with copious amounts of gel
What are the 4 cardiac rhythms that can cause a pulseless cardiac arrest?
Asystole
Pulseless electrical activity
Ventricular tachycardia
Ventricular fibrillation
Which is the most common arrest rhythm in dogs and cats?
Asystole
What is meant by pulseless electrical activity (EMD)
Despite normal heart rate and rhythm on ECG, no contractility in the myocardium
What is the cause of ventricular tachycardia?
Repetitive firing of ectopic focus or foci in ventricular myocardium or Purkinje system
What is the only treat for ventricular fibrillation?
To de-fibrillate
What is the number one drug in CPR?
Oxygen
Which is the first vein of choice for drug access?
Jugular
Which injection route is the last resort?
Cardiac injection
How would you administer intratracheal meds?
Use a cat urinary catheter to access respiratory bronchioles
Why should you be careful in giving fluids?
could produce elevated pre-load/CVP, and reduce coronary perfusion, increase ICP and pulmonary edema
Name the 5 primary drugs used in CPR
-epinephrine
-atropine
-lidocaine
-vasopressin
-reversal agent: naloxone, atipamezole, flumazenil
What are the contraindications for using epi during an arrest?
-ventricular tachycardia
-ventricular fibrillation
-presence of drugs that increase adrenergic effects incr v fib
What effects does epinephrine have?
-arterial vasoconstriction
-increase myocardial contractility
-bronchodilation
What is the duration of action of epi?
Short 3-5 mins
When is atropine given?
To treat bradycardia
What effect does atropine have?
antimuscarinic
increases heart rate and systemic vascular resistance
Why is vasopressin given?
Massive selective vasoconstriction, maintains blood supply to the cerebral and renal vasculature
what type of drugs are Lidocaine and Amiodarone?
Anti-arrhythmic
The role of lidocaine in CPR is changing, when is it now indicated?
For ventricular arrhythmias following resuscitation
Name the 3 anesthesia reversal drugs
-Naloxone
-Atipamazole
-Flumazenil
Electrical defib is the only treatment for what cardiac rhythm?
Ventricular fibrillation
What is involved in post resuscitation support?
-artificial ventilation
-inotropic support
-sometimes pressor support
-monitor urine and CVP
-anticipate SIRS, renal failure, DIC
-keep warm
Local anesthetics are also referred to as what?
Local analgesics
What benefits are there to adding Local anesthetics to GA protocols?
-minimal equipment
-minimal systemic effects when given peripherally
-reduce inhalational/IV anest reqs
-reduce sympathetic response to surgery
-improves post op analgesia
What benefits does a local anesthetics given systemically have?
-central analgesic effect (Na channel blockade)
-prokinetic activity in GIT
-antioxidant and inflammatory modulator
LA's are classified into what 2 categories?
Esters and Amides
Which classification of LA's are used in vet med?
Amides
lidocaine
bupivacaine
mepivicaine
How are amides metabolized?
Are very stable, metabolized by hepatic microsomes
How are esters degraded?
Degraded in plasma by pseudocholinesterases
Lipid solubility is responsible for which property of LA'a?
Anesthetic potency
In general potency of a LS increases with what?
Increase lipid solubility
What is the relationship between lipid solubility and speed of onset?
More lipid soluble the faster the speed of onset
Which property of LA's is responsible for the duration of action?
Protein binding
pKa determines what property of a LA?
Speed of onset
Onset of action is faster if the drug's pKa is what?
Close to physiologic pH
Which form of a drug crosses the cell membranes?
Un-ionized
What effect does dropping pH have on the un-ionized form of the drug?
With dropping pH non-ionized form decreases
What type of tissues have low pH, renedering a LA less effective?
Infected
How can you increase the portion of the drug into a non-ionized lipid soluble state to make it more effective?
Add sodium bicarb to alkalinize it
(also decreases pain on injection)
LA's act on which part of the cell to prevent propagation of AP in all nerve?
Cell membrane
Which nerve requires a higher concentration of a LA to be effective?
Motor nerves
LAs can also effect the impulse transition in excitable tissue such as what?
heart, muscle and brain
What is the principle action of LAs on nerve cells?
Blocking sodium channels in the closed configuration
Which nerves are blocked first....smaller or larger?
Smaller
Generally in which order are nerves blocked?
-autonomic, pregang sympath
-slow pain post gang
-fast pain temp
-motor- muscle spindle, proprio
-sensory- touch, pressure
-motor- skeletal
Esters are metabolized by what?
Para-amino benzoic acid (PABA)
Amides are metabolized where?
Liver with renal excretion
What is the half life of esters?
Amides?
Esters = few minutes
Amides = few hours
Why is regional nerve blockade preferred over local infiltration of tissues with LAs?
LA's can produce local tissue irritation and are neurotoxic
LA's can also be systemically toxic, the degree of systemic toxicity is based in what?
-dose
-route
-rate of absorption
-acid-base status (acidosis incr tox)
-rate of metabolism
-presence of epi
What is the toxic IV dose of Lidocaine?
10 mg/kg
never give more than 6-8mgkg dog/cat
What is the toxic IV dose of
Bupivacaine
4 mg kg
never give more than 2
What are the toxic doses of Ropivacine and Mepivicaine?
Ropivacaine 4-9 mgkg
Mepivicaine 25 mgkg
How do you calculate toxicity levels if a combination of LA's are used?
Toxicity is additive
These toxic doses produce what type of effects?
CNS signs (convulsions)
In the case of a LA overdose, which signs are seen first...CNS or CVS?
CNS
what are the CNS signs of a LA toxicity?
-initial transient CNS depression & resp depression
-agitation, muscle twitching, convulsion
What are the CVS effects of a LA overdose?
-direct myocardial depression--bradycardia and decr CO
-hypotension (vasodilation)
Which LA toxicity is more difficult to treat?
Bupivaciane- high binding affinity for cardiac myocytes
How are seizures from a LA overdose treated?
IV Diazepam/midazolam plus O2
What CV support is needed in an LA overdose?
symptomatic support: fluids, O2, inotropes, antimuscarinics if bradycardic
What are the preventive measures to be take when using LA's?
-dose according to lean bodyweight
-use caution in small pts
-weigh small pts
-dilute LA to safe working volumes
-check to ensure no accidental IV injection
Which LA in particular has vasodilator properties?
All do but esp Lidocaine
Why is Epinephrine sometimes added to LAs?
Delays absorption, prolongs action and improves intensity
Why would you NOT add epi with LAs for ring blocks, local anesthesia of distal extremities?
Potential local tissue ischemia
What effect would adding an opioid to a LA have?
-increase efficacy, extend duration of block
-may also mediate local analgesia
Which A2 agonists have been added to LAs?
Medetomidine, dexmedetomidine
When is a topical anesthetic used on the skin?
EMLA cream for catheter placement, bx
What is a splash block?
Direct application of a LA to a site of interest, most commonly the body wall on closure of the abdomen, peritoneum intra-op, ovarian ligaments, on wounds
When closing small lacerations of excising small masses, what type of LA application would you use?
Incisional and infiltrative
When is intrapleuarl LA used?
Can be instill thru a chest drain to facilitate movement of the animal, pain control
When might intraperitenal anesthesia be used?
Following laparoscopy or hysterectomy (Bupivacaine)
What is a soaker catheter?
A fenestrated tube place deep into a surgical site to allow continuous or intermittent application of LA
What procedure can be performed using infiltration/field block of LA?
-small skin masses
-ring block for teat surgery
-disbudding
-inverted L for standing lap/c-section
-equine castration
Where is the LA injected for equine castration?
Spermatic cord or testis
Intravenous regional anesthesia is also called what?
Bier block
When is intravenous regional anesthesia used?
Ruminant digital amputation/surgery
The procedure for a Bier block is to inject a LA into a local vein and isolate it from general circulation by what?
Applying a tourniquet
What is regional anesthesia?
Injecting LA around the specific nerve or nerves that innervate a surgical site
Regional anesthesia given where is used for standing laps and c-section?
Proximal and distal paravertebral
A brachial plexus block provides anesthesia at what level?
Below the elbow
What type of nerve block is used for de-horning?
Cornual nerve block
Which nerve block prevents eyelid closure during surgery?
Auriculopalpebral
Where do you inject a LA to have it be in the CSF?
SAS
What are the primary site for performing an epidural injection of LA?
Caudal epidural, Lumbosacral epidural
Caudal epidurl analgesia provides analgesia to what region?
Pelvis viscera and genitalia
also abd and hind limbs if vol is large
Which spinal anesthesia is used most in dogs and cats?
Lumbosacral epidural
When performing an epidural on a cat, what must you be sure of in your location?
That your are far enough distal to avoid the a spinal injection
What is the most popular combination of drugs for epidural injection?
Morphine w/ Lido or Bupi
If CSF is seen on an epidural, it is possible to continue the injection but reduce the dose by how much?
50%
What is an absolute contraindication for administering extradural anesthesia?
Never in a pt with coagulopathy or skin infection over injection site
Full doses of LA admimistered ito the CSF can produce what?
Total spinal block
What other side effects can LA's have?
-hypotension
-bradycardia
-coat abnormalities
-pruritus
-respiratory depression or arrest
When are epidural catheters used?
For prolonged analgesia
/ 375
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