Anesthesia Midterm- the actual flashcard worthy stuff 2

kelseyfmeyer's version from 2015-09-27 20:57

Local anesthetics

Question Answer
are LAs acids or bases?WEAK BASES
what are the two kinds of LAs (structure wise) and list off some drugs which belong in each groupamino-amides: lidocaine, bupivicaine, ropivicaine, mepivicaine, prilocaine. Amino-esters: cocaine, procaine, tetracaine, amethocaine (basically, nobody cares about poor ester)
what is the MOA for local anesthetics?works as a direct Na+ channel blockade --> prevents Na+ influx to provide membrane stabilization. This means the cell membrane can't depolarize, which means there is no nerve conduction
Order of block corresponds with particular nerve fibers. Which fibers for 1,2,3,4,5 block?1: B fiber. 2: C and A-delta. 3:A-chi(X looking thing). 4: A-beta. 5 A-alpha (B, C + Ad, Achi, Ab, Aa) (oh look, it's ABC order backwards for part of it)
Nerve fiber B has what function and is involved in what order of block?order 1. (autonomic, preganglionic, sympathetic) (effect of block is warmth from vasodilation)
Nerve fiber C has what function and is involved in what order of block?pain, order 2
Nerve fiber A-delta has what function and is involved in what order of block?pain and temp, Order 2
Nerve fiber a-chi has what function and is involved in what order of block?mm tone, order 3
Nerve fiber A-beta has what function and is involved in what order of block?touch, pressure order 4
nerve fiber A-alpha has what function and is involved in what order of block?motor, order 5
order of block corresponds with particular nerve fiber functions. name loss of functions in order of blockvasoconstriction blocked with 1, pain + pain temp blocked with block 2, mm tone from block 3, touch/pressure with block 4, motor activity blocked with 5 (gets more severe)
are proximal or distal regions blocked first?proximal
which is blocked first: small sensory, large sensory, or large motor?small sensory first. then large sensory, then motor
explain how frequency of stimulation influences onset of blockade?more frequently stimulated (in pain) nerves blocked faster (so traumatized tissue more sensitive to blockade)
the potency of a LA is related to it's...lipid solubility (nerve membrane consists of primarily lipids)
what factor of the LA influences it's speed of onset? (explain)pKa! LAs are weak bases (pKa 7.6-9.1), so the closer the LA is to the body pH (7.4) the LESS ionized they are, and non-ionized diffuse easier which means they work faster. (example of one with pKa close to body pH so it works fast is liodcaine)
do inflamed tissues INC or DEC effectiveness of LAs?DEC... because inflammation lowers pH of tissue, and LAs are weak bases and MOST effective at a pH close to their basic pKa. So inflamed tissue= less effective
the protein binding of a LA influences it's what?Protein binding determines duration of action!! more protein bound means WORKS LONGER. ( EX: Bupivacaine: 95 % protein bound – long duration. Lidocaine: 65 % protein bound – short duration)
lipid solubility determines..potentcy (just like brain with gas anesthetics-> more fat loving, more effective)
pKa determines...onset of action. If not ionized can diffuse faster to start working faster
protein binding determines...duration of action. If bound to protein, sticks around for longer
how do LAs affect the blood vessels...and what is the result?cause VASODILATION (remember B fibers control vasoconstriction, which gets blocked) which means the drug gets carried away faster, which shortens duration of effect
adding epinephrine to an LA does what?it's a VASOCONSTRICTER--> delayed absorption, prolonged action (look out, localized ischemia possible)
adding Hyaluronidase to LA does what?(it's an ENZYME) increasing tissue permeability, facilitates diffusion, rapid onset
adding Bicarbonate to LA does what?buffers H+, faster diffusion, shortens onset and duration, injection less painful (remember, LA are weak bases and if the pH is closer to their pKa, then their onset of action is faster...pKa=IONIZATION)
describe the metabolism of amide LAs vs ester LAsAMIDE: SLOWLY metabolized in liver, with renal excretion, means they can accumulate for a long time after IV infusion. ESTER: hydrolyzed by plasma cholinesterases (in blood) so they quickly become inactive compounds
how do loco-regional use of LAs affect MAC?they dec mac (less pain--> lower CO. lower CO means better diffusion into blood. Which means that it's more effective, so the MAC is lower)
MAC spraing affect means?LOWERS the mac (ie, if something is lowering the MAC, it's causing the induction to be more effective)
systemic use of LAs has a CENTRAL analgesic effect, which means it might be able to..reduce hyperalgesia
how do systemic LAs affect the GI of horses?prokinetic effect
do systemic LAs inc or dec arrythmias?DEC
what are the 2 stages of SYSTEMC TOXICITY of LAs?(1) initial CNS tox: sedation, disorientation, ataxia, muscles tremor, convulsions, respiratory depression (2) cardiovascular tox: depress myocardial contractility, profound hypotension, arrhythmias, CV collapse.
what is Methaemoglobinaemia? which LAs cause it?Methemoglobinemia is a blood disorder in which an abnormal amount of methemoglobin -- a form of hemoglobin -- is produced. With methemoglobinemia, the hemoglobin can carry oxygen but is unable to release it effectively to body tissues. This happens with prilocaine, benzocaine
how much (%) lidocaine will cause an irreversible block w/in minutes?5% lidocaine
what are the LOCAL TOXICITY effects of LAs?Tissue irritation, neurotoxicity (high concentrations) (5% lidocaine=irreversible block), tissue ischemia (when using epinepherine), and allergic reactions (esters)
which group of LAs can cause allergic reactions?esters (allergic to ester's cocaine)
how would you tx seizures induced by systemic tox of LAs?benzodiazepines, propofol CRI
how would you tx CNS depression induced by systemic tox of LAs?supportive care, mechanical ventilation
how would you tx cardiac problems induced by systemic tox of LAs?supportive care, fluids, O2 atropine, antiarrhythmic
what is an IV lipid emulsion, and why would you use it?you can use this as resuscitation from cardiac toxicity due to LAs. may remove lipophilic toxins from affected tissue. It surrounds LA molecules in plasma
what is the onset and duration like for lidocaine?RAPID onset (5min) (pKa close to pH) and short duration (1-2hrs) (is a amide- tissue esterases).
what special thing can you do with lidocaine?Used also for treatment of ventricular tachycardias/- arrhythmias
who is esp. sensitive to lidocaine? side effects?cats-- might cause laryngeal edema in cats (lidocaine spray for ET intubation)
uses for lidocaine?Nerve block, epidural/spinal, infiltration, CRI (IV)
what is mepivacaine's onset and duration?similar to lidocaine's (5min onset, 1-2hr duration) (think that LI-ME similar....lime)
uses for mepivacaine?SC, local infiltration, intraarticular (there was a pic of a horse on this slide... ME the HORSE)
which is more irritating- lidocaine or mepivicaine?lido--mepi is less-because it is preferred in HORSES, and theyre sensitive babies
what is mepivicaine preferred for?Preferred for equine nerve blocks, and intra-synovial analgesia (ME the HORSE)
Bupivacaine- what is the onset and duration?SLOW onset (20-30min) and LONG duration (4-6hrs) (BUPivicaine is a BUM UNDER PRESSuRE--> ie goes slow)
what is bupivicaine often used for?Nerve block, epidural/spinal
which is more cardiotoxic- bupivicaine or lidocaine?BUPI more cardiotoxic ---- (BUP=BUM UNDER PRESSURE= SLOW ONSET AND DURATION= being lazy is BAD FOR YOUR HEART)
which is better for joints- mepivicaine or bupivicaine?MEPIVICAINE is USED FOR JOINTS (me the sensitive horse joint) however, BUPIVICAINE causes Damage to articular cartilage --> being lazy and fat is bad for your joints
what is the kinda bupivicaine which is less toxic? L-bupivacaine (L-B--this of elbie the dog)
Ropivicaine- what is another form which is available? how lipid soluable is it? how cardiotoxic is it?S-ropivicaine, less lipid soluble than bupi, and SIG less cardiotoxic
which LA allows faster return to motor fxn?ropivicaine (think of ropes moving your limbs for you till you recover)
what is "EMLA Cream"?Eutectic Mixture of Local Anesthetics... its 2.5% lidocaine + 2.5% prilocaine (EMLA (emily) PRIS open the LIDOCAINE to stop her pain)
what is EMLA cream used for? notes about its use?Useful for skin anesthesia prior to IV catheter BUT Must wait for action (20-30 minutes) (...duh)
explain the relationship between opioids and LAsopioids Increase efficacy and extend duration of block...Morphine often used intra-articular and epidural blocks
explain the relationship between LAs and α2 adrenoceptor agonistsMedetomidine and dexmedetomidine may extend the duration and increase the efficacy of local blocks
LAs can be used for Differential nerve blockade..what does this mean?like when you have a horse and you start blocking stuff to figure out what's wrong with it
list of some topical anesthetic methodslaryngeal (spray-- cats, pigs, rabbits...), corneal, cutaneous (EMLA-Eutectic Mixture of Local Anesthetics), intraplueral, intraperitoneal, urethral, "splash block" on surgical wounds.
Interpleural/interperitoneal local anesthesia-- WHICH DRUG? ADMIN? how to prevent stinging?BUPIVICAINE (want a SLOW DRUG because i want my innards to not hurt for as long as possible) admin via chest drain or into abd. cavity. (4-6 hrs effective analgesia). *you can dilute with sodium bicarb to prevent stinging
Infiltrational and incisional anaesthesia--> useful for for what? explain how you do ituseful for repair of small lacerations or skin mass removal. you do a line block before sx incision, and then before or after the closure. you basically do multiple small SC injections around area to be desensitized.
Intra-articular--> commonly used for what? what is given POST-op?commonly used for stifle sx/arthroscopy (mepivicaine is recc for articular sx) and POST op bupivicaine is given ((even though it can cause articular joint damage...?) ..possibly combined with lidocaine. **NOTE: if tissues inflamed, use opioids-- LAs wont be very effective
facial/dental nerve blocks- which are the nerves that are/can be blocked? (4)mental nerve block, mandibular nerve block (inferior alveolar), infraorbital nerve block, maxillary nerve block
mental nerve block-- part of what nerve, and blocks what stuff?part of mandibular nerve of TRIGEMINUS (CN V). It blocks the bone, incisors, and soft tissue rostral to 2nd mandibular premolar (its the hole at the front of the mandible)
mandibular nerve block-- aka? what is this nerve a part of? what's the area affected by this block? what are the two techniques?aka inferior alveolar nerve block (by angle of jaw). this is a branch of the trigeminal n (CN V), and the areas blocked are mandibular bone, teeth, soft tissue and tongue on infiltrated side. 2 techniques are intraoral and extraoral (on either side of the angle of the jaw)
infraorital nerve block-- part of what nerve? blocks what tissues? if the block starts to move caudal, what other block does it become?part of maxillary branch of trigeminal (V). blocks bone, soft tissue and dentition rostral to maxillary first moral. if LA moves backwards, becomes maxillary block
whats the only reason you'd do a MAXILLARY block instead of a infraorbital?if you needed to block the soft palate
areas desensitized by a maxillary nerve block?(inject behind last tooth in maxilla) maxillary bone, upper teeth, soft tissues, PALATE, NARES, upper lip
what is a retrobulbar block used for? what are some of the side effects?produces proptosis (protrusion of eyeball) due to volume injected. distorts globe an causes inc in IOP-- but it's used for eye enucleation, so whatever
what is a digital nerve block used for? what nerves does it block? what is an alternaitive block you can use?used in onychectomy/digit amputation. you are blocking the superficial branches of the radial and median nerves, and dorsal and palmar branches of the ulnar nerve. can do a RING BLOCK as an alternative
what on earth is a BIER BLOCK? explain how you do it(AKA IVRA- intravenous regional anesthesia) This is a technique of "IV LOCAL" anesthetic. place venous catheter, tightly wrapped leg with vetwrap from distal to prox to drive out blood then tourniquet was place prox to catheter, then through catheter inject local anesthetic. commonly used in human med. however the time you have for sx is limited bc of ischemia--- ischemia happens after 60 min. so only have 60 min for procedure. if open tourniquet too early, then systemic effects which is bad. timed window you cant go below or above. Also good visibility because less blood all over the place.
epidural anesthesia/analgesia (EDA)-- where do you do this and how to you use landmarks? how is the animal laying?use LUMBOSACRAL SPACE, L7-S1. orientation is the wings of the ilia, L7 transverse projection. aniaml can be sternal or lateral.
speed at which you want to inject for an epidural (EDA)SLOW injection- over a minute
where exactly do you inject in epidural?OUTSIDE OF THE DURA MATER

Recent badges