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53 Cards in this Set
- Front
- Back
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What is the definition of local anesthesia?
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Temporary loss of sensation without unconsciousness
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What is the purpose of using local anesthesia as an adjunct with general anesthesia/
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-inhibition of nociception, minimize subsequent neurological & endocrine changes
-reduced level of general anesthetic -even though brain is non-responsive during general anesthesia its still firing |
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How can local anesthesia minimize negative cardiopulmonary effects?
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May reduce doses of subsequent systemic analgesics post-operatively - less painful
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What are the 4 "definitions" of anesthesia?
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1) Prevent/minimize pain but not nociception
2) Loss of spontaneous and reflex muscle functions 3) Unconsciousness 4) Amnesic= don't remember |
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What are 4 sequelae to using anesthesia w/o pain blocking?
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1) Immune functions compromised, increased risk of infection
2) Impaired wound healing 3) Central & peripheral sensitization "wind-up" 4) Long term consequences unknown |
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What are 4 advantages of local anesthetics?
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1) Lower risk of organ failure
-cardiac, respiratory 2) Better pain relief 3) Low cost of material -drug, needle & syringe 4) Technique dependent |
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What are 9 routes of administration of local anesthetics?
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1) Topical anesthesia
-EMLA, corneal, mucous membranes, splash 2) Infiltration/ incisional line block -soaker caths 3) Peripheral/ regional nerve block 4) IV regional 5) Intraarticular 6) Epidural 7) Spinal 8) Intravenous 9) Transcutaneous |
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What are the 4 sites along the pain pathway that local anesthetics can act on?
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1) Inhibit transduction
2) INhibit transmission 3) inhibit modulation of spinal pathway -don't inhibit perception |
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What are the parts of the chemical structures of local anesthetics?
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-lipophilic, unsaturated aromatic ring
-hydrophilic, tertiary amine -Intermediate chain (determines drug disposition within body) |
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What are 3 intermediate chains that can be present on local anesthetcis?
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1) Amids
-lidocaine, bupivicaine 2) Esters -procaine, benzocaine 3) Weak bases -lipid soluble- neutral form -hydrophilic- charged form (active) |
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What is the mechanism of action of local anesthetics?
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-Reversibly blocks nerve transmission
-binds to receptor site within Na+ channel -diffusion through cell lipid bilayer -inactivate Na+ channel, prevent depolarization (nervous conduction) |
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Do active nerves or quiet nerves block faster with local anesthetics?
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Active nerves- frequency dependent block
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What about the structure of a local anesthetic determines its potency?
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Lipid solubility
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What determines the rate of onset of block?
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pKa (dissociation
-increased pKa= slower onset, increased % ionized |
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Compare the absorption rate of local anesthetics: epidural, brachial plexus, intercostal, peripheral nerve block
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intercostal > epidural > brachial plexus> peripheral nerve block
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What is the order of blockade (what's blocked first to last)?
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1) Pain
2) Temperature 3) Touch 4) Deep pressure 5) motor function -come back in reverse order |
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How are local anesthetics with an amide group eliminated?
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Biotransformaiton in liver
-lidocaine, bupivicaine |
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How are local anesthetics with esters eliminated/
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Enzymatic plasma hydrolysis
-procaine |
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What are some examples of toxic CNS effects of local anesthetics?
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-CNS depression & coma OR
-excitement & seizures |
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What are 3 toxic cardiovascular effects of local anesthetics?
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Hypotension, bradycardia, dysrrhythmias
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What analgesics can act centrally?
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All of them
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What's an example of how toxicity can occur due to improper drug administration/
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Unintentional IV injection or excessive
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What are 2 ways drug administration can damage surrounding structures?
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Traumatic technique
Sepsis |
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What are 2 reasons that drug administration could result in the drug not working?
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Lack of experience
Anatomical abnormalities |
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How do you calculate the dosage of local anesthetic administration?
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Volume/ Mg/kg
-then dilute w/ saline 50:50 to increase volume |
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What is the rule of thumb for doses and volumes of local anesthetics?
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Rough estimate dose < 0.5 mL/kg
-2% lidocaine, 0,5% bupivacaine |
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What are 3 additives to local anesthetics?
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1) Epinephrine
2) Bicarbonate 3) Opioids, alpha2 agonists, ketamine (epidural) |
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What are 3 reasons for adding epinephrine to local anesthetics?
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Prolongation of block
Increase intensity of block Decrease systemic absorption |
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What's two reasons of adding bicarbonate to local anesthetics?
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1) Hasten onset of block
2) Decrease pain of injection |
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What is the Sapir Whorf Hypothesis?
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Language influences how we think (think of Tam at the Buddhist temple trying to translate the fortunes - for some concepts there was no translation)
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What 5 nerves are blocked with a brachial plexus block?
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1) Musculoskeletal N.
2) Median 3) Radial 4) Axillary 5) Ulnar |
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What is blocked when a brachial plexus block is performed?
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Complete sensory and motor block
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How do you perform a brachial plexus block?
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-surgical prep
-palpate dorsal and medial coracoid process of scapula -spinal needle -bevel at center of triceps muscle -aspirate for presence of blood -50% of dose at site -50% infiltrated as needle is withdrawn |
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What are 2 local anesthetics used for brachial plexus block?
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Bupivicaine (36 hours)
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How can you tell if you have performed a successful brachial plexus block?
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Loss of motor & sensory:
-dropped elbow -unable to bear weight |
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What 2 nerves do you block on t he dorsal surface when performing a 4 point block? ventral surface?
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Dorsal surface:
-superficial radial n. -dorsal br. of ulnar n Ventral surface: -Median n. -ulnar n., palmar br |
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What local anesthetics do you use for a 4 point block?
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Combination of 2% lidocaine % 0.5% bupivicaine
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What do you use a 4 point block for?
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Distal limb declaws
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What surgeries are brachial plexus blocks good for?
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Surgeries that occur below the elbow - not adequate for amputation
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What local anesthetics do you use for oral nerve blocks? (4)
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1) Equal volumes of lidocaine and bupivicaine
2) Bupivicaine 3) Lidocaine 4) Septocaine: articaine w/ epinephrine |
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What does an infraorbital foramen block, block?
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Blocks PM3 to incisor 1
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What does a caudal mandibular nerve block block?
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M3 to Incisor 1
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What is the 4 point nerve block for?
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Distal limb surgery
-a ring block around the leg |
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What are 2 facial (dental) blocks performed in a cat?
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1) caudal mandibular nerve
2) Infraorbital nerve and foramen |
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What opioid can be added to an oral nerve block?
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Buprenorphine
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What are the 3 structures you need to palpate when performing an equine epidural?
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1) Cranial edge of ileus
2) Dorsal process of lumbar vertebra #7 3) Dorsal process of sacrum #1 |
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Where do you insert the needle for an equine epidural?
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Needle centered b/w dorsal processes of lumbar and sacrum
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How can you use local anesthetics to decrease pleural pain?
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Can actually infuse a local anesthetic intra-thoracically
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How do you want to position the spinal needle when performing an equine eipdural?
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-Bevel directed cranially
-60 to 90 degree angle to skin -advanced until change in resistance (pop) -test injection with sterile NaCl -then 0.1 mg/kg of morphine |
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When do you use a sacrococcygeal epidural block?
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-Analgesia & blockade of urethral spasm
-Urethral obstruction in the cat: following unplugging or surgerr (peroneal urethrotomy)- unplugging tom cats urethra -cat castration |
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What local anesthetic do you want to use for sacrococcygeal block?
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2% lidocaine
25 ga needle |
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What is local infiltration?
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Sticking needle in and blocking around an area
-Inverted L block commonly used in cows |
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What nerve block can be used for eye enucleation?
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Retrobulbar eye block
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