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57 Cards in this Set
- Front
- Back
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RESTING STATE OF NERVE CELL
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-cell is polarized
-excess (-) inside -excess (+) outside **more Na outside, more K inside -Na permeability low -K freely permeable -threshold -60 --> -90 |
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NA/K ATP PUMP
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-3 Na out and 2 K in
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ACTION POTENTIAL
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-propagation of nerve impulse along an axon begins when the synapses receive neurotransmitters from nerve ending nearby
-this impulse ^ the nerves' permeability to Na going in and K going out --> lowering of voltage occurs until threshold potential occurs --> opens Na channels and massive amounts of Na ions enter the cell -action potential keeps developing as cell interior goes from (-) to more (+) ***cannot occur without a stimulus |
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REFRACTORY PERIOD
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-closing of Na channels
-opening of K channels -K is moved into the interstitial -Na pump restores resting potential -during this phase cannot respond to another stimulus |
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LOCALS MOA
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-blocking large influx of Na ions into the cell associated with membrane depolarization
-does NOT alter the resting membrane potential -believed to have greatest affinity for Na channel in activated (open) and inactivated state (open but inactive) vs. resting (when the channels are closed) |
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SENSITIVITY TO BLOCKADE DETERMINED BY
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-axonal diameter- smaller easier
-degree of myelination -conduction velocity- more rapid the nerve fires the easier to block -location in the nerve bundle- closer to mantle (outside) easier to block, closer to the core (inside) harder to block |
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CHEMISTRY OF LOCALS
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-lipophilic- benzene ring, (fat loving)
-hydrophilic- tertiary amine (water loving) -these two are separated by a chain that is either an ester or an amide -all locals are weak bases that carry a slightly positive charge at physiologic pH |
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ESTER METABOLISM
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-pseudocholinesterase (plasma cholinesterase)
-by product PABA (sunscreen) may cause allergic rxn -in GENERAL shorter duration than amides ***if they go into the CSF they are longer duration because no pseudocholinesterase in the CSF (most often used is tetracaine) **CSF not the same as epidural b/c in an epidural it is not in the CSF |
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AMIDE METABOLISM
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-metabolized in the liver (decrease in liver function will decrease the rate of metabolism)
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METHGB CAUSED BY WHAT LOCAL ANESTHETICS
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-metabolites of prilocaine and to a lesser extent topical benzocaine (hurricane spray, EMLA)
normal Fe2+ (FERROUS) goes to Fe3+ (FERRIC) O2 carrying capacity is poor -TX- give O2 or methylene blue 1mg/kg |
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CHARACTERISTICS OF LOCAL ANESTHETICS
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-the more lipid soluble the more potent (correlates partially with duration of action **more inside less available to be carried away with the blood)
-protein binding- PRIMARY responsible for duration of action (**binds to alpha 1 glycoprotein (and albumin) prolonging the elimination time) **old people have less protein so more free drug floating around |
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pKa of 2 (L.A. THAT IS A WEAK BASE pH > 7.45)
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****a weak base (L.A. > 7.45) going into an environment that is more acidic than the base (phys pH 7.4) with a pKa of 2 (which is more acidic than the environment) will have more unionized form of the drug and a faster onset. ***if the pKa were 9, the drug would have the least unionized drug and have the slowest onset
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ESTERS MAX DOSE, DURATION, MAX DOSE WITH EPI, DURATION WITH EPI
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Nesacaine/ chloroprocaine max - 12mg/kg, dur - 30-60min, max dose with epi - 14mg/kg, dur with epi - 30-90min
Novocaine/ procaine max- 12mg/kg, dur- 30-60min Pontocaine/ tetracaine max- 3mg/kg, dur 90min - 6 hours (with epi can go as long as 8) Cocaine max- 3mg/kg, dur- 30-60min |
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AMIDE (ALL HAVE TWO I'S) MAX DOSE, DURATION, MAX DOSE WITH EPI, DURATION WITH EPI
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Lidocaine/ xylocaine max- 4mg/kg (3-5), dur- 30-120min, max epi- 7mg/kg, dur with epi- 120-360min
Mepivicaine/ carbocaine max- 4mg/kg, dur- 45-90min, max epi- 7mg/kg, dur with epi- 120-360min Ropivicaine max- 3mg/kg, dur- 90-240min Bupivicaine/ marcaine max- 2.5mg/kg, dur- 120-240min, max epi- 3.2mg/kg, dur with epi- 180-420min Etidocaine/ duranest 1% max- 6mg/kg, dur- 120-180min, max epi- 8mg/kg, dur with epi- 180-420min |
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LIDOCAINE
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XYLOCAINE
MAX 4mg/kg (3-5) DURATION 30-120min MAX EPI 7mg/kg DUR WITH EPI 120-360min |
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MEPIVICAINE
(amide) |
CARBOCAINE
MAX 4mg/kg DURATION 45-90min MAX EPI 7mg/kg DUR WITH EPI 120-360min |
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ROPIVICAINE
(amide) |
MAX 3mg/kg
DURATION 90-240min |
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BUPIVICAINE
(amide) |
MARCAINE
MAX 2.5mg/kg DURATION 120-240min MAX EPI 3.2mg/kg DUR W EPI 180-420min |
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ETIDOCAINE
(amide) |
DURANEST 1%
MAX 6mg/kg DURATION 120-180min MAX EPI 8mg/kg DUR W EPI 180-420min |
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NOVOCAINE
(ester) |
PROCAINE
MAX 12mg/kg DURATION 30-60min |
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NESACAINE
(ESTER) |
CHLOROPROCAINE
MAX 12mg/kg DURATION 90min - 6 hours |
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COCAINE
(ESTER) |
MAX 3mg/kg
DURATION 30-60min |
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LOCALS MOST USED FOR SPINALS
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(ester) - tetracaine
(amide) - marcaine and lidocaine |
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BIER BLOCK
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Done on extremeties hand forearm, short procedure, trigger release, carpal tunnel release, cyst removal.
1) 2 IV's one surgical one for local on surgery arm 2) monitors, sedation 3) place dbl tourniquet 4) hold arm up 5) wrap esmarch tightly from figertips to tournaquet 6) inflate proximal cuff 250-300 mmHg 7) unwrap esmarch 8) inject local in slowly 0.5% lido (no epi) 40-50cc's 9) post injection remove IV and hold pressure 10) pt may c/o tournaquet pain if surg > 30min --> may inflate distal THEN let go of proximal **Min cuff time 20 min **Max cuff time 1.5-2 hour COMPLICATIONS - mechanical failure of tournaquet, L.A. toxicity |
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LOCAL ANESTHETIC TOXICITY
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FROM EARLY TO LATE
-circumoral and tongue numbness - lightheadedness and tinnitus - visual disturbances - muscle twitching (might want to start worrying here) - unconsciousness - convulsions - coma - resp arrest - CV collapse |
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TREATMENT OF LOCAL ANESTHETIC TOXICITY
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-O2 --> raises seizure threshold
- ET if needed - hyperventilate- decrease the delivery of local to the brain - DRUGS benzos, barbs supportive - code mode, CV collapse |
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BUPIVICAINE/ MARCAINE cardio toxicity
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-most cardio toxic
-Blocks Na channels and dissociates very slowly TREATMENT - 20% lipid rescue gives the bupivicaine/marcaine something to grab a hold of |
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PERIPHERAL NERVE BLOCKS
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-digits, ankles, brachial plexus, lower extremity, penile
***no epi with digits or penile blocks |
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EPIDURAL POSTERIOR TO ANTERIOR
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-me
-skin -sub Q tissue -supraspinous ligament -intraspinous ligament -ligamentum flavum (yellow or crunchy ligament) -***epidural space -too far -dura mater -arachnoid mater -pia mater |
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ROPIVICAINE SIMILAR PROFILE
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-similar profile with (isomer of bupivicaine/marcaine) Bupivicaine/marcaine, but less cardio toxic
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HANGING DROP METHOD FOR EPIDURAL
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-primarily recommended for thoracic epidural
-drop of fluid at the hub of the needle -insert in slow increments -when fluid gets sucked in you are in epidural space (neg pressure) |
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LOR TECHNIQUE FOR EPIDURAL (MOST COMMON)
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-Touhy syringe with few cc's of air or saline
-slowly advance with either with constant pressure or "tapping" on plunger until there is "loss of resistance" --> epidural space |
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TEST DOSE FOR EPIDURAL
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-once in space catheter is threaded into space
-may use PF NS to tent space first -catheter usually up 3-7cm ***3cc's of 1.5% lido with epi 1/200K (0.005mg/ml) this is a 5cc vial --> if in intravascular ^ HR and BP by 20-30% --> if subarachnoid will exhibit s/s of spinal (45mg of lidocaine and 15mcg of epi) ALWAYS PULL BACK BEFORE YOU INJECT ANYTHING INTO THE CATHETER |
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NESACAINE/CHLOROPROCAINE IN AN EPIDURAL
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-works very fast
-does something to the receptors and post op narcotics don't work in epidural space -doesn't last long 30min |
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DRUGS USED FOR EPIDURALS
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-Chloroprocaine/Nesacaine 2-3%
-Lidocaine/xylocaine 1-2% -Mepivicaine/Carbocaine 1-2% -Bupivicaine/Marcaine 0.25-0.75% -Ropivicaine 0.1-0.5% **Lower % more sensory block **Higer % more motor block |
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CAUDAL TYPE OF EPIDURAL
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-entering the epidural space thru the sacral hiatus
-involves penetration of the sacrococcygeal ligament -**Felt as groove or notch above the coccyx b/t the sacral cornua (two bony prominences) -used most often in pediatrics for analgesia (Bupivicaine/Marcaine, Ropivicaine, opioids, lido w/out epi) |
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SPINAL TECHNIQUE
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-you want below L-2
-L-4 - L-5 top of iliac crests -Monitor, O2, alarms, sedation -sitting or lateral -sterile P & D -1% lido local (skin wheel/sub Q) -introducer -Spinal needle advance until CSF -(quinke, sprotte, whitacre) |
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DRUGS FOR SPINAL
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-bupivicaine/marcaine 0.75%
-Lidocaine 5% -Tetracaine 0.5-1% -Procaine 10% -each drug has different characteristics -sensory vs. motor blockade |
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SUPINE HYPOTENSION
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-does not occur until 30% of blood volume is gone
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DISTRIBUTION AND LEVEL OF BLOCK
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-influenced by several factors
-Baracity- Density of the drug as compared to the CSF |
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HYPOBARIC
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-lighter than CSF, will float
-jack knife or lateral position (add sterile water) |
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HYPERBARIC
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-heavier than CSF, so will sink towards gravity
-will drop to most dependent part of subarachnoid space -dependent on position SUPINE- T5 SITTING - sacral 0.75% hyperbaric, most common mixed with dextrose 8.75% |
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ISOBARIC
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-mix with CSF
-will maintain at level of injection |
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KEY LANDMARK
SUPERIOR ILIAC CREST |
-L4-L5
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KEY LANDMARK
T4 |
nipples
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KEY LANDMARK
T6 |
xiphoid process
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KEY LANDMARK
T10 |
umbilicus
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ABSOLUTE SPINAL AND EPIDURAL C/I
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pt refusal, coagulopathies (idiopathic), severe uncorrected, severe AS, hypovolemic shock, ^ICP, infection at site
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RELATIVE C/I FOR SPINAL AND EPIDURAL
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-sepsis, uncoop pt, pre-existing neuro defecit, severe spinal deformity, stenotic valve lesions
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CONTROVERSIAL SPINAL AND EPIDURAL C/I
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-prior back surgery, communication issues, complicated surgery
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PHYSIOLOGIC EFFECTS OF SPINAL AND EPIDURALS
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-CV EFFECTS- mainly due to SNS blockade
--vasodilation (venous dilation not arterial) --decreased venous return, decreased BP/CO (lose preload) ****initial response is tachycardia and decrease BP If you get a low HR then you have a high block, (cardio accelerator fibers T1-T4 b/c of intercostals pt may not be able to get a deep breath or good cough) -PULM EFFECTS- blockade of intercostals Nausea from hypotension Hypothermia --> vasodilation |
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CARDIOACCELERATOR FIBERS
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fibers that innervate the heart
-when these are blocked it is considered a high spinal and you will see a decrease in your heart rate, when what you want is the initial compensatory increase in HR |
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ORDER OF BLOCKADE
TERMED DIFFERENTIAL BLOCKADE |
-(sympathetic fibers are blocked first, larger some myelinated blocked later)
***So more sensitive nerves may be blocked at higher levels before more resistant fibers at lower levels S-T-P-T-P-M-V-P sympathetic, temp, pain, touch, pressure, motor, vibration, proprioception ***so if we find sensory at T4, 2 above T2 will be SNS block, and T6 will be motor block |
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COMPLICATIONS OF SPINALS AND EPIDURAL
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-hypotension- prehydrate, vasopressors (ephedrine), LUD for pregnancy or obesity
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COMPLICATIONS OF SPINALS AND EPIDURAL
(PDPH) |
-post dural pucture H/A, CSF leak
-severe frontal, occipital headache, tinnitus, diplopia -worsens with sitting/standing TX- blood patch- take blood and put it in the epidural space (10-20cc's) |
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PREVENTION OF PDPH
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-use smaller needles
-paramedian approach -bevel to the side -pre-hydrate |
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HIGH SPINAL
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-tingling of the fingers
-C8 = middle -C7 = finger -C6 = thumbs can't talk, can't breathe, ----> intubate |
