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29 Cards in this Set
- Front
- Back
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Generally, how do local anesthetics work?
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Then bind to Na2+ channels in nerves and block signal conduction.
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List 4 different ways local anesthetics can be used
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1. Topical
2. Subcutanaeous 3. Perepheral nerve block 4. Neuraxial nerve block |
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What type of nerve fiber is easiest to anesthetize?
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Small myelinated nerves.
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Which class of nerves are not myelinated? What do they do?
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Type C fibers, they carry visceral pain
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Which class and subclass of fibers are easiest to block? What do they do?
What about second? |
Type A gamma, they control muscle tone
Type A delta, they transmit pain, and temperature |
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Suppose you block a nerve root, where relative to that root's dermatome will you block sympathetic, motor, and sensory components of that root?
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Sympathetic - above
Sensory - At the dermatome Motor - Below the dermatome |
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What states of sodium channel is preferentially blocked?
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Inactivated and Open (the H gate is out of the way of their site of efficacy in these states)
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How do you remember what local anesthetics are amides?
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They have 2 i's in their names!
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Describe the unique properties of locals and their charge as it relates to their efficacy.
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The anesthetics can only cross the membrane in their uncharged form but the charged form is the active form.
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Are locals generally basic or acidic?
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They are basic, pKa's are 7.6-8.7
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In order to speed up the action of locals what can you do?
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Administer them with sodium bicarbonate (buffer an acidic tissue closer to the pKa of the drug) or choose a local with a low pKa
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How do you localize the effects of a local anesthetic?
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Use a vasoconstrictor (epe). This works best with anesthetics that normally vasocilate (lidocaine, mepivicaone)
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What are the indications of a neuraxial block?
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Abdominal or lower extremity pre/post op
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What are the contraindications of neuraxial block?
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Absolute: Infection at the site of injection, elevated ICP, bleeding
Relative: abnormal coagulation, bacteremia, cardiac disease |
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Compare a spinal Vs. an epidural block
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Spinals go into the subarachnoid space at the cauda equina and there is no sacral sparing.
Epidurals function at the nerve root, you can vary the drug and dose to create timing effects. They affect a specific root and can effect any root. |
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Discuss respiratory issues at high block levels.
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You cant do them without ventilation and vasopressors. You will repress the respiratory centers and cause a sympathetectomy.
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Absorption of locals is affected primarily by what?
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Tissue vascularization
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What are the maximum doses in adults and neonates for Bupivicaine?
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Adults: 3 lg/kg
Neonates: 2.5 mg/kg |
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What are the maximum doses in adults and adults on epe for Lidocaine?
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Adults: 5 mg/kg OR 7 mg/kg with epe
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What are signs of local anesthetic toxicity?
What increases these? |
Lightheartedness, peri-oral numbness, tinnitus, seizures.
Acidosis |
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How do you treat local anesthetic toxicity?
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1. A, B, C's
2. Treat seizures (benzodiazepines) 3. Treat arrythmias (epe, atropine, vasopressin) 4. Use intralipid 1cc/kg |
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What are the complications of local anesthesia?
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Spinal headache (PDPH), transient neurologic symptoms, backache
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Describe the risks of PDPH
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females, large needles, pregnancy
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Describe how you treat PDPH
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Sit down, administer fluids, caffeine, do a blood patch
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What is Procaine?
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A short acting low potency local anesthetic
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Name a long acting, potent amine local anesthetic.
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Tetracaine
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Name a medium duration medium potency amide local.
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Lidocaine
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What is Mepivicaine?
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A low potency, medium acting, amide local,
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Name 3 local anesthetics that are long lasting, highly potent amides
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Bupivicaine, Levobupivicaine, Repivicaine
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