PAIN OSCE Flashcards
MOA of local anesthetics
Blocks Na+ channels
* bind receptors in phospholipid membrane
* Stops transmission of action potential
There are at least 9 Na+ channel binding sites
* heterogeneous structure
How are LA classified
Classified by their ability to react w/specific receptor sites in Na+ channel
* 4 sites w/in sodium channel
- w/in Na+ channel (tertiary amine local anesthetics)
- outer surface of Na+ channel (tetrodotoxin, saxitoxin)
3-4. Activation or inactivation gates (Scorpion venom)
Characterize Sodium Channels in Neurons
Na+ migrates inward bc:
1. concentration (Greater outside)
2. electrostatic gradient positive ion attracted by neg. intracellular potential)
Resting nerve membrane=impermeable to Na+
* prevents massive influx
Na+ travels external to internal=Depolarizing event
What is highly conc around nodes of ranvier?
Na+ Channels
Where does LA act?
Nodal areas (Nodes of Ranvier)
* blocks depolarization
Can you block one node of ranvier w/local anesthetic to implement action
No, must block multiple nodes of ranvier
LA must bathe 8-10 mm of neuron to block
Characterize the resting state of neurons
Slightly permeable to Na+
Freely Permeable to K+ & Cl-
What stimuli excite pain receptors? How sensitive are receptors to these stimuli?
Mechanical, Thermal, Chemical
Does local anesthetic block more than pain
Does not block proprioception
* Pressure, vibration, temperature
What is important regarding local anesthetic application
volume
concentration
pH
what can remove LA at the site of LA administration
Most is lost at the perineurium
* absorbed by Nutrient blood vessels & lymphatics
* greatest barrier to diffusion
What form of LA penetrates the lipid bilayer of the nerve axon membrane?
Base form
Drugs w/what pka have a slower onset
High pka=slower onset
pka 7.5-9.0
What is the pH of LA w/o vasoconstrictors
pH 5.5-7
Characterize LA pH w/vasoconstrictors
LA w/vasoconstrictor are acidified to retard oxidation & prolong shelf life
Sodium Bisulfite
* antioxidant
* increase shelf lie
2% Lidocaine HCL
* pH: 6.8
* acidified to pH 4.2 w/sodium bisulfite
* at pH 4.2 it will take longer for anesthetic to function at full effect
What are the properties of LA
Reversibly block nerve conduction
* Must be lipophilic & hydrophilic for effective parenteral injection
Drugs that are not hydrophilic=Topical Drugs
LA w/o hydrophilic component is used for what?
Topical
Benzocaine gel
What influences drug removal & how do we modulate it?
Factors that remove:
* Increased protein binding
* Vascularity of injection site
* presence or absence of vasoactive substance
What is the max dose of each type of LA
What is the typical amount of episodes in a cartridge of LA
18 micrograms=.018 mg
What is the typical amount of LA in a cartridge (1%)
18 mg
What is the significance of epi in LA
20 ug of epi: Doubles pre-op plasma conc.
200 ug of epi surpases
* heavy exercise
* surgery
* pheochromocytoma
Increases cardiac work
* MI & arrhythmias are more likely to occur
do LA have significant systemic effects?
Aside from their influence on cardiovascular & CNS fxn
* LA exert few systemic effects
What determines LA toxic Potential
The uptake of LA into systemic circulation & removal by redistribution, metabolism & excretion
Drug w/potent vasodilating properties may enhance their own uptake=esters
What occurs to LA when entering the circulation
Proteins made in liver (Albumin)
* if liver is not working properly, less will be bound to plasma proteins
entering circulation, LA is partially (5-95%) bound to plasma proteins
* a1-acidglycoprotein
* albumin
* RBCs
how does pregnancy impact LA
–
Lidocaine across the BBB contributes to what?
CNS Depression
Tonic-Clonic convulsions
Septocaine
4 %
* aka articaine
* shortest duration
lidocaine
2%
* aka xylocaine
* safest in children
mepivacaine
3%
* aka Carbocaine
* causes least vasodilation
* no epi
standard mepivacaine/carbocaine epi
0
bupivacaine
0.5%
aka Marcaine
Longest duration
* not safe in children
Standard bupivacaine epi
1:200,000
0.009 mg per cartridge
what is the maximum cartridges used for health pts vs cardiac pts
what is the limiting factor for LA in pediatric pts, LA or epi?
LA
what is the LA maximum in pediatric patients?
4 mg/Kg
Kg=lbs/2.2
what are the signs & symptoms of LA toxicity?
Signs:
* Slurred speech
* Shivering
* Muscle Twitching
* Dizziness
* Disorientation
Symptoms:
* Warm, flushed feeling of skin
* Pleasant dream-like state
* Numbness of tongue and entire mouth
What are the signs & Symptoms of LA overdose
Signs:
* Slurred speech
* Excitability
* Elevated BP, HR, Respiratory Rate
* Sweating
* Vomiting
Symptoms:
* Metalic Taste
* Visual Disturbances (inability to focus)
* Loss of consciousness
What are local complications when delivering LA
Needle breaks
Prolonged anesthesia or paresthesia-resolves 8 wks
Facial nerve Paralysis
Trismus (restricted jaw movement)
Soft Tissue Injury
Hematoma
Burning on injection
How can LA get to facial nerve?
to far posterior of IAN block can contribute to facial nerve paralysis
what is the most likely adverse run to LA administration?
Fainting
What is the solubility of N2O in the blood?
0.47
When administering N2O, what should O2 saturation be above?
94%
What date do you want to collect for patients before a procedure with N2O?
PMH, PSH, MED-DRUG hx
Drug Abuse
Vital Signs
Respiratory System Assessment
After administering N2O, what do you want to monitor?
Level of consciousness-Mental Status
Ventilatory Function
Oxygen Desaturation-Hypoxemia
Pulse Oximetry
End Tidal CO2
Pt response to gas response or hypo-response
What is the appropriate response to nitrous?
comfortable/relaxed
reduced fear/anxiety
aware of surroundings
responds to commands
Might experience tingling of extremities &/or mouth, heavy legs/arms, body warms, light feeling,
what is the maximum N2O Flow
50%
What is the technique for nitrous administration
Assemble and assess N2O cart, tanks etc
* Check scavenger device fxn
Oxygen Flow: reservoir bag 2/3 full
Secure Nasal Hood & Establish baseline
Titrate Nitrous
Terminate Nitrous-5 min Post op O2 100%
Assess recovery
Discharge pt
What does 5 mins of post-op O2 prevent
diffusion hypoxia
What information should you obtain from a patient post N2O
Vital Signs
Lethargy
Headache, Dizziness, Confusion, Nausea
What are potential changes w/N2O administration
Myocardial Depression: Mild
Cardiac Output: Unchanged
BP: Unchanged
Arrthymia potential: None
Respiratory Depression: Mild
Respiratory Rate: Slightly increased
Tidal Volum: Decreased
Can we administer N2O to pregnant patients? If so, when?
Can be used in pregnant patient
Use after 1st trimester
* Consult pt’s OBGYN
What are relative contraindications for N2O
1st trimester pregnancy
Pneumothorax
Cystic Fibrosis
URI
COPD
Psychologic impairment
What is the universal color for N2O & O2?
N2O=Blue
O2: Green
What are the advantages of N2O
Smaller volume of gases used
less cost
Decreased in exhaled N2O Contamination
What are the disadvantages of N2O Administration
Fixed Percent increments of N2O=easier to oversedate pt
What is the normal variation in vital signs before and after administering N2O
Blood Pressure
* +/- 20 mmHg/10 mmHg from baseline
Heart rate:
* +/- 15 beats/in from baseline
* Same rhythm as baseline
Respirations:
* +/- 3 breaths/min from baseline
Ibuprofen MOA
NSAID
* inhibits prostaglandin synthesis
* vasodilation-acts on heat regulating center of hypothalamus
Produces analgesic and anti-inflammatory effects
* decreases fever
30 min onset
Ibuprofen: Max dose
Adults:
* 400-800 mg 3-4 times/day
* Maximum: 3.2 g/day
Children:
* 5-10 mg/kg/dose q6-8h
* Max: 40 mg/kg/day
Where is ibuprofen metabolized?
Liver
Ibuprofen: Pregnancy
Category B
3rd trimeter=D
Acetaminophen: MOA
Central Analgesic
Unknown MOA
* inhibit prostaglandin synthesis in CNS
* Block pain impulses through peripheral action (less)
* Peripheral vasodilation by acting on hypothalamic heat-regulating center
antipyresis (Fever reducer)
Analgesic
15-30 min onset
Where is Acetaminophen metabolized?
Liver
Acetaminophen: Pregnancy
Category B
Acetaminophen: Max Dose
Adults/Elderly:
* 365-650 mg q4-6H or 1 g 3-4x daily
* Maximum: 4g/day
Children:
10-15 mg/kg/dose q4-6h as needed
Max: 5 doses/24 hr
Hydrocodone: MOA
Blocks pain perception in cerebral cortex
* bind to u &. K opiate receptors at synapse
* results in decreased synaptic chemical transmission throughout CNS
Alters pain perception
Analgesic
Hydrocodone: Pregnant
Category C
Hydrocodone: Max Dose
Adults & Children older than 13 or 50Kg +: 60 mg/daily
Elderly: 2.5-5 mg q4-6h
Children: 0.135 mg/kg/dose q4-6h
What is Norco
Hydrocodone + Acetaminophen
7.5 or 10 mg hydrocodone + 325 mg Tylenol
Side effects of opioids
N & V
Constipation
Sedation
Respiratory Depression
Addiction
Oxycodone: MOA
Opioid Analgesic
* Binds opioid receptors in CNS
Alters the perception & emotional response to pain
Oxycodone: Max Dose
Adults, Elderly:
* initially 5 mg q6h as neeeded
* may increase up to 30 mg q4h
* usual: 10-30 mg q4h as needed
Children:
0.05-0.15 mg/kg/dose 14-6h
What is Percocet
oxycodone 2.5-10 mg
Acetaminophen: 325 mg
What is the appropriate pain control for dental procedures
