VN Q3 Local Anesthetics
Terms
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- List 4 local anesthetics
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Lidocaine
Bupivacaine
Procaine
Proparacaine - Define local anesthesia
- Use of chemical agent on sensory neurons to produce a disruption of nerve impulse transmission, leading to a temporary loss of sensation
- Toxicity of Local Anesthetics (5)
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If injected into nerve, loss of function
Irritation at injection site
Paresthesia - tingling, pain, irritation during recovery
Allergic reactions
Systemic toxicity - coma (injected IV, or overdosed) - Onset and duration of Lidocaine
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Immediate onset
Duration 1-2 hours - Onset and duration of Bupivacaine
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Onset 20 minutes
Duration 4-6 hours - Onset and duration of Procaine
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Immediate onset
Duration 1 hour - Onset and duration of Tetracaine
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Onset 5-10 min
Duration 2 hours - Define sympathetic blockade
- Loss of function of the neurons in the autonomic nervous system
- Name routes in which local anesthetic can be given
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topical application
infiltration (injection)
joint
nerve plexus
vein
epidural space - Advantages of local anesthetic (4)
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no systemic effects
short recovery time
useful in dentistries
do not penetrate placenta - Disadvantages of local anesthetic
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1) patient not unconscious
2) training required
3) ineffective if area is inflamed
4) toxicity - Local anesthetics' mechanism of action
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Stabilize cell membrane.
Blocks membrane channnels through which sodium flows into neuron.
Nerve depolarization is stopped.
Sensory and motor neurons stop functioning - Ethyl chloride
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Topical anesthetic
Sprayed on intact skin. Provides partial, short term analgesia by cooling skin.
Used for biopsies & superficial procedures. - EMLA cream
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Mixture of lidocaine & priocaine
Desentsitizes intact skin for minor superficial procedures such as catheterization.
Duration 1-2 hours - Splash block
- Use of sprays or soaked gauze sponges for local anesthesia.
- Two reasons why epinephrine is added to lidocaine
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1) Epinephrine prolongs effect of lidocaine by ~ 50%
It causes vasoconstriction, decreasing rate of drug absorption.
2) Reduces toxicity by reducing concentration of drug entering circulation at any given time. - Epinephrine should not be used with lidocaine on... (3)
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1) incision site - impairs tissue perfusion & healing
2) ears, tail, digits - circulation to these areas may be compromised
3) animals with cardiac disease - incrases risk of ventricular arrhythmias - Regional anesthesia
- Local anesthetic is injected into a major nerve plexus or in proximity to spinal cord. Results in blockage of a large area.
- Epidural anesthesia is best used on (3)
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1) Large animals
2) Debilitated small-animal patients in which general anesthesia is problematic
3) Patients requiring profound pain control - Where is anesthetic deposited for epidural anesthesia
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Epidural space - between dura mater and the vertebrae.
Between L7 and sacrum - IV regional anesthesia (Bier Block)
- Common in large animals - injected into distal segment of superficial vein