OS Final Flashcards
Which ions are associated with extracellular space?
Na+, Cl-, HCO3-
- more positive
Which ions are associated with intra cellular space?
K+, proteins
- more negative
Where do local anesthetics exert their pharmacological action on nerve (which part of the nerve?)
on the nerve membrane
how do local anesthetics work (which ion channel?)?
LA binds to specific receptors on the Na+ channel to prevent channel from opening (therefore no action potential and no pain for the patient)
“specific receptor theory”
What is the speed of conduction for a myelinated nerve?
120 m/sec
What is the speed of conduction for an unmyelinated nerve?
1.2 m/sec
Where do local anesthesia work on a myelinated nerve?
at the Nodes of Ranvier (abundance of sodium channels located here)
How do local anesthesias work on the nodes of ranvier?
need to have 2-3 nodes (8-10mm) of the nerve blocked
According to the specific receptor theory, where does local anesthesia bind to?
Specific receptor on the Na channel
What is the order of onset for local anesthetic agents?
Cocaine > Articaine > Mepivacaine > Lidocaine > Prilocaine > Bupivacaine > Procaine
What is the duration order of local anesthetics?
Bupivacaine > Mepivacaine > Lidocaine = Prilocaine > Cocaine > Articaine
What is the onset, duration time, and mg/kg of maximum dose for lidocaine?
2-3 min (rapid)
1.6 hours
4.4 mg/kg (300mg)
What is the onset, duration time, and mg/kg of maximum dose for prilocaine?
2-4 min
1.6 hours
6mg/kg (400mg)
What is the onset, duration time, and mg/kg of maximum dose for mepivicaine?
1.5-2min (rapid!!!)
1.9 hours
4.4mg/kg (300mg)
What is the onset, duration time, and mg/kg of maximum dose for bupivicaine?
6-10 min (very slow onset)
2.7 hours (longest duration)
1.3mg/kg (90mg)
What is the onset, duration time, and mg/kg of maximum dose for articaine?
1-2 min (rapid, 2nd fastest)
0.5 hours (shortest duration)
7mg/kg (500mg)
What is the onset and duration time for cocaine?
1 min (fastest onset)
1-1.5 hours
What is the onset for procaine?
6-10 min (slowest)
What pH determines the ease for nerve blockade?
extracellular pH
What tissue is more difficult to get adequate anesthesia? why?
Inflamed or infected tissue because lower pH or increased H+
What increases the shelf life for LA?
Low pH -> 5.5-7
How does pH affect LA?
If the pH of the environment does not allow the free base form (what enters the nerve membrane) of the anesthetic to exist, numbing will not occur
- The further the pH is from the ideal for that specific anesthetic, the lower the percentage of that local anesthetic will be present in the free base form
Is local anesthesia hydrophilic or hydrophobic?
Amphipathic (both hydrophilic and lipophilic)
What is the exception of LA being amphipathic?
Benzocaine, which doesn’t have a hydrophilic group–making it great for
topical anesthesia
How do organic components of local anesthetic change from charged form to non-charged form? (in ninja terms)
The ninja has on his backpack (H+) and is injected, he ditches his backpack and become a free base to cross the nerve axon membrane, then gets his backpack back to be able to complete the mission (bind to the sodium channel)
Only the free base form (“ninja”) of the anesthetic can enter the nerve, the sodium channel must be blocked from the inside
Process of anesthesia changing from cation to anion (NOT in ninja terms)
- Anesthesia is injected as an ionized cation that cannot cross the nerve cell membrane (but can become a non-ionized free base, which can diffuse into the membrane)
- Once in the nerve, the free base can become its ionized version again and bind to the specific receptor to prevent Na channel from opening
What happens once free bases diffuse?
they must dissociate back to cationic form in order to bind to the receptor
How does pKa affect local anesthetic?
lower pKa = faster onset
higher pKa = slower onset (because fewer free base molecules are available to diffuse)
How does lipid solubility influence local anesthesia?
Lipid solubility influences potency
What happens to the drug with increased lipid solubility?
The drug is more potent
(directly related because nerve membrane is 90% lipid)
What happens with decreased lipid solubility?
The drug is less potent
(directly related because nerve membrane is 90% lipid)
What does protein binding influence?
Protein binding influences duration
What happens to the drug with increased protein binding?
the drug has longer duration
(directly related because nerve membrane is 10% protein)
What happens to the drug with decreased protein binding?
the drug has shorter duration
(directly related because nerve membrane is 10% protein)
What is the most used vasoconstrictor?
Epinephrine
Which is the most profound vasoconstrictor?
Cocaine (also ropivicaine)
Which is the most profound vasodilator?
Procaine
Mnemonic for how to tell the difference between an ester and an amide?
“i” before the “-caine” if an amide
What is the effect of esters in aqueous solutions?
Readily hydrolyzed
What are examples of esters?
Procaine
Propoxycaine
Tetracaine
Cocaine
Benzocaine
Dyclonine
What is the effect of amides in aqueous solutions?
resist hydrolysis; get excreted in urine as an unchanged form
What are examples of amides?
Lidocaine
Etidocaine
Mepivocaine
Bupivocaine
Prilocaine
Articaine
How are esters metabolized in the body?
Hydrolyzed in the plasma by pseudocholinesterase into paraaminobenzoic acid (PABA)
What do people have a reaction to in an ester local anesthetic?
PABA
Where are amides metabolized in the body?
Primary biotransformation process site is the liver
What is the relationship between cirrhosis patient and metabolism of local anesthetics?
A liver with cirrhosis becomes flooded with blood after anesthetic delivery
What is cirrhosis?
Late stage of scarring (fibrosis) of the liver
LA with cirrhosis is a contraindication for what patients?
ASA IV to V for patients with liver dysfunction (or heart failure)
How do cirrhosis and/or CHF interfere with the amount of your local anesthesia injection?
Amide LAs are chemically modified (metabolized) in the body in the liver, so since the liver is not functioning as well (doesn’t have the full metabolic capacity), then less LA should be administered
Does this disease state increase the availability of this drug or decrease the availability?
This disease increases the available (will be available longer) due to the liver not being able to biotransform the drug. Therefore we give them less LA
Which organ in the body has the greatest concentration of local anesthesia?
Skeletal muscle
What is tachyphylaxis?
The increase in tolerance to drug after repeated administration
What is elimination half life?
time needed for 50% of the drug to be reduced in blood level
How do you calculate the elimination of half life?
1st half-life: 50% eliminated
2nd half-life: there is 50% of the drug left…half of 50 is 25. Add 25 to the previous 50 you have eliminated 75%
3rd half-life: you have eliminated 75%, there is 25% left, 25/2= 12.5 add that to 75=87.5% eliminated
4th half-life: you have eliminated 87.5% up to this point. There is 12.5% left. Half of that is 6.25 add that to 87.5= 94% eliminated
Do all local anesthesia readily cross the BBB and placenta?
Yes
What happens initially when a patient has overdose/toxicity to local anesthesia?
causes excitatory response (numbness of tongue and circumoral region slurred speech, shivering, AV disturbances, tremor, etc.)
- if you ignore initial signs, patient can go into a seizure
- if you keep loading them up with more local anesthesia, they will stop breathing
What happens eventually when a patient has overdose/toxicity to local anesthesia?
depressive response on CNS with a lesser CV effect as well as agitation, confusion, dizziness, drowsiness, dysphoria, auditory changes, tinnitus, perioral numbness, metallic taste, etc.)
What LA’s are catecholamines?
epinephrine, norepinephrine, dopamine
What LA’s are non-catecholamines?
amphetamine, ephedrine, methamphetamine
What does epinephrine dilution mean? If someone ask you what’s 1:300,000 mean.
___:____ -> gram (or mg) of drug: ml of solution (so 1:300,000 would be 1 g (1000 mg) of drug per 300k ml of solution
How do you calculate mg/ml of solution?
Just divide. Here would be 1000mg/300,000ml = 0.0033 mg/ml of solution
How to know which dilution formulation is more concentrated when comparing two values?
ex: 1:100,000 and 1:200,000
The lower the second number (ml of solution), the higher the concentration (i.e. 1:100,000 is more concentrated than 1:200,000)
What’s the maximum fose for epinephrine in a healthy patient?
0.2 mg (200 mcg)
What is the maximum dose of epinephrine in a not so healthy patient (cardio patient)?
0.04 mg (40 mcg)
Which agent (catecholamine) lacks significant B2 actions thus produces intense peripheral vasoconstriction with possible dramatic elevation of blood pressure?
Norepinephrine – EXCESSIVE vasoconstriction
- is associated with a side effect ratio 9X higher than that of epinephrine? That’s one of the big reasons why this agent is NOT available in the U.S.
* Levonordefrin closely resembles norepinephrine
What are contraindications for vasoconstrictors?
“memorize them”
- High blood pressure (200mmHg systolic OR 115mmHg diastolic)
- Uncontrolled hyperthyroidism
- Severe cardiovascular disease
- Undergoing general anesthesia WITH halogenated agents
- Other drugs: Patient receiving non-specific beta-blocker, MAOi, tricyclic antidepressants
What are indications of severe cardiovascular disease in which you would not administer a vasoconstrictor?
a) Less than 6 months after myocardial infarction
b) Less than 6 months after cerebrovascular accident
c) Daily episodes of angina pectoris or unstable angina
d) Cardiac dysrhythmias despite appropriate therapy
e) Post-coronary artery bypass surgery (CABG), less than 6 months
4) Undergoing general anesthesia with halogenated agents
What patients are NOT normally considered candidates for elective or emergency dental treatment in the office?
Patients in categories 1 to 3a through 3d are classified as ASA 4 risks
In what instance can OD occur if MRD is administered?
If a patient is a hyperresponder
Do patients OD if you exceed MRD (maximum recommended dose)?
Not necessarily, chances of OD just increase, but you can actually OD below the MRD too
Do we need to decrease maximum calculated drug dose on medically compromised, debilitated or elderly?
YES, Disadvantaged people are slower in metabolizing these drugs, so you need to decrease the MRD on them
What’s the most common cause of failure to achieve adequate anesthesia?
Anatomical variation and faulty technique
That’s right, it’s not the drug’s fault. It’s your technique and patient
Articaine is _______ concentration
4%
What are contraindications to articaine?
- patient allergic to amide type anesthesia
- sulfite sensitivity
- caution with hepatic disease
- patient with impairments in cardiovascular function
- children <4 y/o
Can articaine be used on children under 4 years of age?
Not recommended due to insufficient data
Smaller the gauge, the __________ the diameter of the needle
Bigger
Describe the diameter of a 25 gauge
Greater internal diameter
Describe the diameter of a 30 guage
smaller diameter
- Less deflection, greater accuracy in injection
- Less chance of needle break, easier aspiration
Total of 4ml of 3 % Mepivacaine without epinephrine has been used. What is the total mg used in this case? The MRD for this local anesthesia is 4.4mg/kg (MPD)
120mg
4ml x 0.03% = 0.12
0.12 x 1000 = 120mg
Billy Jean is going through special diet, and after 2 months she only weight 20kg. She is here at University of Miracle KC, College of Dentistry for some dental work. You picked 2% lidocaine with epinephrine 1:100,000 as your anesthetic agent (b/c it has red label on it). What is the maximum mg that you can give for her?
(remember 4.4 is MPD for lidocaine)
4.4 mg/kg x 20 kg = 88 mg
Can we use a needle on more than one patient?
No
Needle should be covered with a protective sheath when not in use
True
Use both hands to recap the needle
big NO, use scoop technique
Since there are curves and different contour of facial skeleton, we should bend the needle for
difficult access block
Absolutely NO
Needle must be _________ after use
properly disposed
Which agent is a bacteriostatic and was removed from local anesthesia cartridge on 1984 due to reported allergic reactions
methylparaben
What was novacaine replaced by?
Lidocaine
Does the exterior surface of the cartridge have sterility?
No manufacturer claim of sterility about exterior surface of the cartridge
- Bacterial culture tested fail to produce nay growth
Can a cartridge withstand extreme temperature?
NO
- No autoclaving especially plastic cartridge
- When heated, the vasopressors are destroyed
Where should cartridges be stored?
In room temperature in a dark place
- no benefit from using cartridge warmer
What should you not soak a cartridge in?
in alcohol or cold sterilizing solution
- Semipermeable diaphragm permits diffusion of these solution
What are the most common psychogenically induced reactions people have upon local anesthesia injection?
- Vasodepressor syncope (fainting)
- Hyperventilation
What is a relative contraindication?
caution should be used when two drugs or procedures are
used together. (It is acceptable to do so if the benefits outweigh the risk.)
What are examples of relative contraindications?
i) Pregnant women in 1st trimester
ii) Cimetidine + ASA III CHF patient
iii) Malignant Hyperthermia
iv) Methemoglobinemia (to Prilocaine)
What is cimetidine + ASA III CHF patient a contraindication for? Why?
amide LA
Why is cimetidine a contraindication for amide LA?
Cimeditine increases 1⁄2 life of circulating LA
(a) H2 receptor blocker competes with lidocaine for hepatic oxidative enzyme
Why is CHF a contraindication for amide LA?
CHF (ASA III or IV) may demonstrate decreased liver perfusion and increased 1⁄2 life amide LA.
What is an absolute contraindication?
event or substance could cause a life-threatening situation
What are examples of absolute contraindication?
i. ASA IV Cardiovascular risk patient
ii. Tricyclic Antidepressant (TCAs)
iii. Cocaine abuser
What are ASA IV cardiovascular risk patients not a candidate for?
vasopressors or elective dental care
How recent do cardiovascular patients need to have a MI to be contraindicated?
Recent (<6 months) or repeated MI increases risk during dental care or local injection
Why is a cocaine abuser an absolute contraindication?
because it stimulates NE release and inhibits reuptake
What can cocaine using and local anesthetic cause?
MI
How soon after cocaine use can LA be administered?
72 hours of clearance
- Postpone dental treatment, if suspected usage within 24 hours.
What is absolutely contraindicated for a cocaine abuser when performing treatment?
Epinephrine-impregnated gingival retraction cord is absolutely contraindicated
How long is topical applied for?
2 minutes
Why is aspiration important?
To make sure you’re not in a blood vessel
Where should the bevel of a needle be placed?
Place the bevel of the needle on the tissue (in the direction you want to go) and then inject
What does the bevel of a needle face?
The bone
What should you do with the needle as you enter?
Twist to keep it from deflecting in one direction
Where should the finger be when injecting?
Finger rest
What division is V1?
Opthalmic
What division is V2?
Maxillary
What division is V3?
Mandibular
Where does V1 exit?
Superior orbital fissure
Where does V2 exit?
Foramen rotundum
Where does V3 exit?
Foramen ovale
One of the branch of V2 (trigeminal nerve), upon exiting cranial base, makes a quick 180 degree turn back into the cranium. This nerve provides sensory innervations to the dura mater. It’s the ______ nerve.
Middle meningeal nerve
Is V1 ophthalmic sensory or motor?
Sensory
Is V2 maxillary sensory or motor?
Sensory
Is V3 mandibular sensory or motor?
sensory AND motor
What are the three types of anesthestia?
- Local infiltration
- Field block
- Nerve block
What is a local infiltration?
Numbs one tooth
What is a field block?
Numbs about 2 teeth
What is a nerve block?
Numbs entire area. injecting the nerve bundle
When is infiltration performed?
If numbing one tooth (premolar)
Where is the needle entered in an infiltration?
Adjacent to bone apical to apex
Why does an infiltration work?
Maxillary labial bone is porous, allows infiltration of anesthetic (anesthetic diffuses into the bone
What areas are anesthetized in infiltration?
single tooth
buccal periodontium and bone
mucosa (labial or buccal)
Where is a posterior superior alveolar nerve block (PSA) entered into?
Height of the vestibule at a 45* angle to the occlusal plane
- needle is inserted in about 16mm
What is super important to do in a PSA block?
Aspirate (aspiration rate is 3%)
Can cause hematoma if there is positive aspiration
What areas are anesthetized in a PSA?
- Maxillary molar tooth pulps
- MB root of 1st molar in 72%
- Buccal periodontium and bone (not palatal)
Remember max 1st molar MB root has special innervation. Which one is more likely to give you the ugly hematoma?
PSA
Where is the needle injected in a middle superior alveolar nerve block (MSA)?
injected well above premolar apices (bevel facing bone)
What areas are anesthetized in a MSA block?
- Maxillary premolars
- MB root of 1st molar in 28%
- Buccal periodontium and bone (not palatal)
Where is the needle injected in anterior superior alveolar nerve block (ASA)?
Needle contacts roof of infraorbital foramen (which is located about 16 mm above vestibule)
Where is anesthetic directed in an ASA block?
Directly into canal
How to work the needle for an ASA block
Insert about ½ the needle length, orient needle bevel towards bone and insert until bone is contacting needle
When should you maintain pressure during an ASA block?
During injection and 1 minute after
What area is anesthetized in an ASA block?
- Maxillary central incisor through canine
- Premolars
- MB root of first molar in 28%
- Buccal periodontium and bone
- Lower eyelid, side of nose, and upper lip
Where is the needle injected in a greater palatine?
Locate greater palatine foramen and inject midway between midline and free gingival border (10mm from palatal midline)
How can the greater palatine foramen be identified?
By finding the junction of molars 2&3 and then moving the needle 1cm mesially
What areas are anesthetized in a greater palatine?
- Posterior portion of hard palate (canine to last molar)
- Overlying soft tissues
**no anesthesia of teeth
Where is there no anesthesia with a greater palatine?
Teeth
Where to inject in the nasopalatine?
0.5cm posterior to the central incisors at the midline at the base of the interdental papilla between the maxillary central incisors
What areas are anesthetized in a nasopalatine injection?
- Anterior portion of hard palates
- Both hard and soft tissues
- NO anesthesia of teeth
What are the landmarks for the long buccal nerve?
mucobuccal fold & mandibular molars
- Parallel to the occlusal plane of ipsilateral mandibulars
Where areas are anesthetized in a long buccal nerve?
- Gingiva buccal to molars
- Retromolar pad mucosa
- Buccal mucosa in molar area
- NO hard tissue anesthetized
What are the landmarks for the inferior alveolar block?
- Occlusal plane of mandibular posterior teeth
- Coronoid notch (make syringe level to
coronoid notch) - Pterygomandibular Raphe
Where is the injection area for the inferior alveolar block?
medial side of the ramus
* Approach from the contralateral side
* Site is between pterygomandibular raphe and coronoid notch
What is the anesthetized area of the inferior alveolar block?
mandibular quadrant except buccal soft tissue associated with molars
- Entire unilateral side from midline
- Lingual mucosa, tongue, teeth
What nerves are anesthetized in the inferior alveolar block?
Inferioralveolar, incisive, mental, lingual (usually)
What patients are gow-gates good for?
Patients whom IA nerve block doesn’t supply adequate analgesia
What are landmarks for the gow-gates block?
- Corner of the mouth
- Intertragic notch
- Distolingual cusp of the second maxillary
molar
Where to inject on a gow-gates block?
Needle contacts neck of condyle
- patients should open wide so condyle moves forward
What nerves does the gow-gates anesthetize?
inferior alveolar, lingual, mylohyoid, auriculotemporal, buccal (usually, 75%)
What is special about the vazirani-akinosi nerve block?
“Closed-mouth” mandibular nerve block
What is the height of injection for a vazirani-akinosi block?
Maxillary muco-gingival line
Where is the vazirani-akinosi nerve block injected?
Direct parallel to Ramus, insert 25 mm depth
What nerves are anesthetized for a vazirani-akinosi nerve block?
- Inferior Alveolar nerve
- Lingual nerve
- Mylohyoid nerve
What is the mental nerve?
terminal branch of
inferior alveolar (mental nerve)
What do you palpate in a mental nerve block?
Mental foramen (near premolars) to determine site
Where do you inject for a mental nerve block?
Tissue over foramen
What areas are anesthetized on the mental nerve block?
- Mucosa anterior to foramen
- Skin of the lower lip
- Chin
What should you beware of in a mental nerve block?
Possible hematoma (positive aspiration rate of 5.7%)
What are maxillary injections?
- PSA, MSA, ASA
- Greater palatine, nasopalatine
What are mandibular injections?
- Long buccal nerve
- Inferior alveolar block
- Gow-gates block
- Vazirani-akinosi nerve block
- Mental nerve block
What block should be used on its own?
Buccal nerve
Why should a buccal block be used?
Numb it if you want to take care of buccal tissue around the mandibular molar
What is the location of the buccal nerve?
Between lateral pterygoid heads
What areas are anesthetized in a buccal nerve block?
- Cheek area
- Molar buccal gingiva
- Retromolar pad mucosa
- Buccal mucosa in molar area
- NO hard tissues anesthetized
Comparing gow-gate/vazirani-akinosi/inferior alveolar, which injection has the needle placed closest to the condyle?
Gow-gates closest to condyle
