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What is local analgesia?
temporary loss of pain sensation and movement
What does local analgesia affect?
Does local analgesia affect the entire CNS?
Does local analgesia have any of the same risks as general anesthesia?
Local analgesia is _____ toxicity and _____ cost.
What kind of recovery does local analgesia have?
Why is local analgesia good for Caesarian sections?
because it does not cross the placenta and affect the babies
What are the disadvantages of local analgesia?
- still need restraint
- can OD small patients
- does not work well on connective tissue
What are the different types of local analgesia?
What is lidocaine?
What is the onset of lidocaine?
What is the duration of lidocaine?
1 - 2 hours
What does lidocaine feel like to the patient when it is injected?
What is bupivacaine?
What is the onset time for bupivacaine?
What is the duration of bupivacaine?
Is epinephrine a local analgesia?
what is epinephrine?
a sympathetic neurotransmitter
What does epinephrine do?
What drug do we sometimes add epinephrine too and why?
- the vasoconstriction keeps the drug from being picked up into circulation
What are the advantages of using epinephrine?
- prolongs numbing effect
- reduces toxicity by lowering blood concentration
- reduces bleeding at surgery site due to vasoconstriction
What are the disadvantages to using epinephrine?
may reduce healing rate at surgery site
What are the systemic effects of epinephrine?
increased HR, strength of contraction, more prone to arrhythmias
When would we use lidocaine without epinephrine?
treat certain cardiac arrhythmias
Does local analgesia have little to no respiratory or cardiovascular side effects?
Does local analgesia provide any sedation?
What does local analegsia do?
blocks transmission of nerve impulses (stops nerve depolarization)
What is the order of loss of sensation?
- joint sensation
- deep pressure
What is sympathetic blockage?
loss of autonomic impulses from brain to body
What does sympathetic blockage mainly affect? Why?
- sympathetic nervous system
- due to location of nerve cell bodies in sympathetic ganglia
Where are the sympathetic ganglia located?
on either side of the thoracic and lumbar vertebrae
What does sympathetic blockage cause?
What could happen during an epidural?
agent may go too far cranial and affect the sympathetic ganglia
What are the different routes of administering local analgesias?
- inflitration (injecting into the area)
Do local analgesia's penetrate intact skin?
What do local analgesia's penetrate?
What are the different types of topical analgesias?
- conjunctiva (eye drops)
- oral (spray for vocal cords)
- lubricating gels
How do we avoid complications with infiltrating a local analgesia?
- clip and prep to avoid infection
- use small needle to avoid tissue damage
What are the two different types of infiltration?
When do we mainly use nerve blocks?
in large animals
How do we deposit local analgesia for nerve blocks?
around the nerve - not in it
Where do we put line blocks?
infiltrate in line between spinal cord and surgery site
What is the onet of a line block?
3 - 5 minutes
When are regional analgesia mainly used?
human and large animal medicine
What is the injection site for regional analgesia?
into major nerve plexus or close to spinal cord
What is intravenous infusion?
- apply tourniquet to limb
- inject local analgesic into superficial vein of limb
- numbs limb distal to tourniquet
How long can the tourniquet be left on for intravenous infusion?
no more than an hour and a half
How do we remove a tourniquet after intravenous infusion? Why?
- slowly over 5 minutes
- to prevent large amounds of local analgesic from reaching the brain quickly
What are some complications of local analgesic?
- anaphylactic reaction
- local damage
- systemic toxicity
- epidural complications
What can cause local damage?
- injecting into a nerve
- local irritation
If local analgesics reach high blood levels what can it affect?
the brain and heart
What are the clinical signs of local anaglesic toxicity in the brain?
- muscle twitching
- respiratory depression
What is the treatment for toxicity in the brain?
What are some epidural complications?
- trauma to spinal cord
- too cranial
What can happen if an epidural is injected too cranially?
- paralyze repiratory
What are the two types of ventilation?
- assisted ventilation
- controlled ventilation
What is assisted ventilation?
patient initiates each breath and anesthetist bags during the breath to increase tidal volume
Assisted ventilation can be _____ or _____.
continuous or intermittent (every 5 minutes or so)
Why do animals "sigh"?
- re-inflate partially collapsed alveoli
- remove excess CO2
What is controlled ventilation?
- anesthestist controls both rate and depth of breathing
- patient makes no spontaneous efforts to breathe
What are the two different types of controlled ventilation?
What is manual controlled ventilation?
anesthetist bags patient every 5 seconds or so
What is mechanical controlled ventilation?
continuous ventilation by machine
What does PPV stand for?
positive pressure ventilation
What is PPV?
gases are pused into the patient's lungs by manual bagging or mechanical compression of bellows
What is negative pressure ventilation?
normal breathing or iron lung (chest expands when muscles of inspiration contracts and pulls gases into lungs)
What is the purpose of PPV?
anesthetized patient is often unable to breathe well enough on his own
What is ventilation?
moving gases into and out of the lungs
Is inhalation active or passive?
Is exhalation active or passive?
What is inhalation initiated by?
increased blood CO2 levels
What is tidal volume?
amount of gas that passes in and out of lungs per breath
What is respiratory rate?
breaths per minute
In anesthetized patient's the brain is _____ to blood CO2 levels. It takes _____ CO2 level to initiate next breath.
Because anesthetized patients have lower respiratory rates what does this mean to the patient?
- blood CO2 builds up
- blood O2 decreases unless on 100% O2
- atelectasis can occur
How can the anesthestist compensate for the effects of a lower respiratory rate?
- give 100% oxygen
- bag the patient
What is the procedure for manual ventilation?
- close pop-off valve
- press reservoir bag up to 20cm H2O
- open pop-off valve
What is the difference for non-precision vaporizer and precision vaporizers for bagging?
- non-precision: turn off non-precision vaporizer for bagging
- precision: no need to turn off
What do we need to do with the precision vaporizor if we are totally controlling ventilation?
turn it down or it will deliver a large volume of gas and the patient will go too deep
When is controlled, continuous ventilation necessary?
- thoracic surgery
- respiratory disease
What is the purpose of controlled ventillation?
lowers patient's blood CO2 levels - less stimulus to breathe, spontaneous breathing stops
What is the breaths per minute for controlled ventilation?
8 - 12 breaths/minute
How do we wean a patient off of controlled ventilation?
- turn off vaporizer and N2O
- continue 100% O2
- gradually reduce bagging rate to about 5 per minute
When is mechanical ventilation used?
for controlled ventilation
What does mechanical ventilation do?
compression of bellows pushes gases into patient's lungs
Where does the mechanical ventilation attach?
to anesthesai machine at bag opening
Types of mechanical ventilators deliver according to...
- volume of gas
When is mechanical ventilation most commonly used?
in thoracic surgery
What are the risks of controlled ventilation?
- pressure can get too high an can rupture alveoli
- decreased cardiac output
- excessive anesthetic vapor may be delivered if using VIC system
When the alveoi ruptures what can it cause?
- mediastinal emphysema
What does decreased cardiac output cause?
high pressure in thorax which compresses vena cava
What do muscle paralyzing agents do?
affect voluntary skeletal muscle - stops impulses from going there
When do we use muscle paralyzing agents in small animal anesthesia?
- mechanical ventilation
- Caesarian section
How do we administer muscle paralyzing agents?
- given after patient is anesthetized and ventilation is controlled
- given IV slowly
How long does muscle paralyzing agents last? Can we give repeated doses?
What do muscle paralyzing agents do?
interrupt transmission of impulse from nerve ending to muscle
What are the two types of neuromuscular blocking agents?
What do depolarizing agents do?
causes surge of activity at neuromuscular junction followed by refractory period - muscles cannot accept impulses
What do depolarizing agents do?
block muscle receptors - muscles are unable to accept impulses
Do reverser agents exist for depolarizing agents and depolarizing agents?
- depolarizing agents: no reverser
- non-depolarizing agents: reversers
What do reversers do?
- have parasympathetic side effects - bradycardia, salivation
- pretreat patient with atropine or glyco
What are some risks of neuromuscular blocking agents (muscle paralyzing agents)?
- hard to assess depth of anesthesia
- cannot assess pain
- avoid in kidney and liver disease and glaucoma
What drugs affect potency of neuromuscular blocking agents?
- anticancer drugs