Local ANesthetics- Pharm Part 2

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Local Anesthetics Pharm Part 2

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Topical Anesthesia1. mucous membranes-42. intact skin3. cut skin
1. bronch, endoscopy, nasal surgery, intubation2. IV start, skin grafting, circumcision3. lac repair
Tumescent Anesthesia1. med used2. EBL/ analgesia?
1. Lidocaine (0.1% or less) with Epi (1:1000000)2. 12ml bld loss/ L of fat removed18-24hrs in some patients
TachyPhylaxis1. def2. way to prevent?3. thot to be d/t what?
1. repeated injection of same dose produces dcrs response2. short dosing intervals so pain does not re-occur3. central mechanism (spinal cord sensitization)
Metabolism1. estersa. pathwayb. slowest/ fastest2. amidesa. pathway and 1st stepb. dependent on 4 thingsc. ___ excretion of ___d. clearance is decr in what 3 conditions?
1a. hydrolysis of ester bond by plasma cholinesteraseb. slow- tetra. fast- chloroprocaine2a. enzymatic degradation in liverb. hepatic extraction, bld flow, metabolism, protein bindingc. Renal/ metabolitesd. hepatic dysfunction, IA, PIH
1. what will signif prolong Lidocaine's half life3. rapidly cleared?4. 2 with interned clearance?5. 2 with slower clearance?
1. hepatic dysfunction2. Renal disease3. chloroprocaine4. Lidocaine, Mepivacaine5. Bupivacaine, Ropivacaine
Lung Extraction1. pulmonary extraction of which amide LA's?2. for Bupivacainea. pulm extraction is ______, therefore _____b. it is inhibited by _____(both incr risk of toxicity)
1. Lidocaine, prilocaine, Bupivacaine2a. dose-dependent/ saturableb. beta blockers (propranolol)
**VERY few True allergies**1. most common true allergy with esters is r/t what?2. no _____ btw classes3. patient may be allergic to _____
1. PABA2. cross-sensitivity3. preservative
Absorption of LA1. 2 things that will incr absorption systemically?2. 3 things that will dcrs absorption?3. order of types of blocks with highest to lowest chance of incr absorption/ toxic effects?
1. if site is very vascular and incr dose (linear relationship btw dose and plasma lvls)2. -high fat area- incr potency (high lipid sol/ incr Prot binding= less systemic absorption)- vasoconstrictor= dcrs bld flow/ less absorbed3. intercostalcaudal (type of epidural)epiduralbrachialsciatic/ femoral
1. relationship btw concentration and bound drug (r/t protein binding)2. fetal trapping of drug in which situation?3. addition of vasoconstrictor will effect
1. incr concentration= incr % of free drug, lower % of bound drug2. fetus- acidotic; drug trapped in ionized state3. longer DOA and dcrs blood levels- more with intermediate than long acting drugs
Incidences of TNS after spinal anesthesia1. occurs more frequently with which drugs?2. which position?
1. Lidocaine and Mepivacaine2. lithotomy, knee arthroscopy
Local Toxicity1. exposure of ___ nerve to high concent of LA in lab resulted in injury2. 2 areas most susceptible to injury3. nerve condition that makes is more susceptible to injury
1. desheathed2. spinal cord and nerve root (peripheral nerve block - safe)3. nerve that is stretched
1. 3 S/S or components of neurotoxicity2. Transient neurological symptomsa. symptomsb. occurs when?c. what is normal?d. recovery occurs when?e. treatment?f. incidence high with which drug?- not r/t what?- could be r/t what?
1. non-specific patchy numbnessTNSCaudal Equina Syndrome2a. moderate to severe pain in lower back, buttocks and post thighsb. 6-24hrs after resolution of blockc. sensory/ motor examd. 1-7 dayse. pain mgmt (NSAIDs, opioids)f. intrathecal (into joint) Lidocaine- concentration- microcatheter use
1. 3 signif factors that pre-dispose pt to TNS
1. patient positioningneural ischemia secondary to stretchmaldistribution of LA (pooling... r/t micro-cath)
Cauda Equina SYndrome1. diffuse injury across ___ ___ resulting in varying degrees of what 3 things?-- r/t what?2. other causes?** need to rule this out before implementing Sx-matic Tx for TNS
1. lumbosacral plexus/ sensory loss, bladder/ bowel dysfunction, paraplegia-- toxicity of LA2. trauma, compression (hematoma, infection)
1. LA and BBB2. dose-dependent pattern of symptomsa. low plasma concentrationsb. higher concentrationsc. very high concentrations
1. readily cross BBB2a. CNS depressionb. CNS excitation (seizures)c. generalized CNS depression
Factors in CNS Toxicity1. potential approx parallels ____2. what will increase the potential (pH, Pro, clear.)3. what will decrease potential
1. drug potency2. acidosisincr PCO2dcrs Pro bindingdcrs clearancerapid IV injection3. BZD, Barbs (could mask CNS sx's and result in more serious cardiac symptoms)
1. potential for CNS toxicity varies with type of block= how?2. likelihood of unintentional vascular injection highest with what?
1. ICE BS2. peripheral nerve block
1. cardiac or CNS toxicity requires higher plasma concentrations?2. potential for cardiac toxicity parallels ____3. which agents have higher inherent cardiotoxicity4. increasing doses of less potent agents results in what?
1. cardiac2. potency3. high lipid solub/ high potency4. bradycardia, hypotension, hypoxia
Lidocaine vs Bupivacaine1. myocardial contractility2. elctrophysiologic effects3. higher affinity for resting/ inactive Na channels**Bupivocaine dissociates much more slowly than Lido= Na channels never completely recover- conduction block accumulates**
1. equal2. Bupiv produces greater3. Bupivacaine
1. TH for bupivacaine induced cardiotox is reduced in what condition?- patient's taking what?2. additional factors that affect (may mask) cardiotoxicitya. CNSb. peripheral
1. pregnancy- BB, CCB, diogixin2a. inhibition of nucleus tracts solitarii in medulla - inhibition of autonomic relfexes (no tachycardia)b. direct vasodilationpotent peripheral inhibition of sympathetic reflexes
1. compare Ropivacaine/ Levobupivacaine with Bupiva. equipotent for which 2 procedures?b. when should u use Rop/ LEvo instead?
1. the exhibit 30-40% lower potential for systemic toxicitya. plexus anesthesia and nerve blockb. when u need large dose of LA (epidural)
1. good way to prevent cardiotoxicity2. other than ACLS stuff, what may be good treatment for cardiotox?
1. appropriate dose** frequent aspiration of fractional injection**2. Lipid infusion (drug bound in lipid)