Lessons 3 & 4 Flashcards
How do you size an oral airway?
Corner of the mouth to the tip of the ear
Contraindications for a Nasal Airway
Bleeding disorder
Base-of-skull fracture
Nasal fracture
Previous nasal surgery or cleft palate repair
Sinusitis
History of frequent nosebleeds
Severe atherosclerosis
Normal thyromental distance
6 cm (approximately 3 fingerwidths)
<6cm (some will say 7) means a more difficult intubation
The longer it is, the more room you have to move the tongue forward and expose the glottis
What is the Mallampati score used for?
To predict the ease of endotracheal intubation
Think 1-2-3-4:4-3-2-1
For example, Mallampati 1 you can see 4 things, Mallampati 2 you can see 3 things, etc.
Mallampati I
Soft palate, uvula, *fauces, tonsillar pillars visible
fauces = throat (opening to pharynx)
Mallampati II
Soft palate, uvula, fauces visible
Lose tonsillar pillars
Mallampati III
Soft palate, base of uvula visible
Mallampati IV
Only hard palate visible
After intubation, where should the tip of the tube be?
Generally speaking, place ETT at 23 cm in males and 22 cm in females (measuring from the corner of the mouth)
Goal is 2cm cephalad to the carina on CXR
However, the lip to carina distance best correlates with patient’s height.
Optimal depth of ET placement can be estimated by the formula:
“(Height in cm/7)-2.5.”
Cormack-Lehane Grading System
Four grades of laryngoscopic view to predict the ease of intubation
What is the LEMON score used for?
To determine which patients might pose airway management difficulties. The score (with a maximum of 10 points) was calculated by assigning 1 point for each of the following LEMON criteria and multiplying by 2 (higher numbers = difficult airway):
L=Look externally (facial trauma, large incisors, beard or moustache, large tongue…any = 1 point)
E=Evaluate the 3-3-2 rule (incisor distance <3 fingerbreadths, hyoid/mental distance <3 fingerbreadths, thyroid-to-mouth distance <2 fingerbreadths…abnormal = 1 point)
M=Mallampati (Mallampati score ≥3 = 1 point)
O=Obstruction (presence of any condition that could cause an obstructed airway = 1 point)
N=Neck mobility (limited = 1 point).
How do you verify correct tube placement?
Gold Standard = direct visualization of tube through the cords (“second look”)
- Symmetric chest movement
- Symmetric breath sounds
- Fogging of tube
- End tidal CO2 (>30 for 3-5 breaths)
- Palpation of cuff in suprasternal notch
- Fiberoptic bronch
- CXR
Steps to peforming a RSI (rapid sequence intubation)
- Monitors
- Denitrogenate (preoxygenate)
- Induction drug and cricoid pressure* (+/- BURP)
- Immediately followed by NMB
- Intubation after NMB has taken effect
- No ventilation until ET tube is in place
* *Idea is to close the esophagus to prevent passive regurgitation (the cricoid cartilage is the only cartilage the completely surrounds the airway)*
What medications can be given to decrease the risk/complications of aspiration?
- Metoclopramide
- PPI
- Histamine-2 Blockers
- Sodium citrate
These are all debated and provide theoretical benefit
What is metoclopramide?
A gastroprokinetic (makes the stomach empty faster) that works 10-30 minutes after IV administration
Does NOT affect gastric pH
How does omeprazole work?
PPI = Increase in gastric pH
In theory, if regurgitation and aspiration does happen, it will do less damage
However, these drugs work slowly (over hours) and do nothing about acidity of contents already in the stomach
What type of drugs are cimetadine and ranitidine?
Histamine-2 Blockers
Increase gastric pH, but like PPIs, do nothing about the acidity of contents already in the stomach
What does sodium citrate do?
Neutralizes the acidity of the gastric contents within 15 minutes
Should be given 15-30 minutes prior to induction
Define a local anesthetic
A subtance which reversible inhibits nerve conduction when applied direcly to tissues at non-toxic concentrations
How do local anesthetics work?
They limit influx of sodium (i.e., depolarization), thereby limiting propagation of the action potential
They can be thought of as sodium channel blockers on the nerves
Why would local anesthetics be relatively useless in an acidic environment (e.g., septic patient or necrotic limb)?
Only the ionized form is active
Rule of “i’s” for local anesthetics
“i” before “caine” = amide
no “i” before “caine” = ester
Amides = bupivacaine, lidocaine, ropivacaine, etidocaine, mepivacaine
Esters = cocaine, chloroprocaine, procaine, tetracaine
Allergy vs Systemic Toxicity
for Local Anesthetics
A true allergy is very rare, however, most reactions are seen with esters
Systemic toxicity (when it happens) is seen more often with amides
Emergency treatment of systemic local anesthetic toxicity
Immediate IV injection of Intralipid 20% (1.5 ml/kg)
Can repeat several times or start infusion
Relative blood levels after different regional techniques with local anesthetic
In descending order = “BICEPS”
Blood
Intercostal
Caudal
Epidural
Peripheral Nerve
Subcutaneous
Where should vasoconstrictors (e.g., epi) not be used?
Fingers
Toes
Nose
Ear lobes
Penis
Again, this is more theoretical and less in practice
Define Regional Anesthesia
Rendering a specific area of the body (e.g., foot, arm, lower extremity) insensate to the stimulus of surgery/other instrumentation
Application of local anesthetic to mucous membrane (cornea, nasal/oral mucosa)
Topical anesthesia
Advantages = technically easy, minimal equipment
Disadvantages = large doses can lead to toxicity
What is a “Bier” block?
Injection of local anesthetic intravenously for anesthesia of an extremity
Step 1: place a small IV (20 or 22G) into a distal vein in the extremity to be blocked [note: this is not your main IV catheter]
Step 2: Exsanguinate the arm with an Esmarch bandage
Step 3: Inflate the tourniquet and inject local anesthetic
Disadvantages = duration limited by tolerance of tourniquet’s pain
Injecting local anesthetic near the course of a named nerve
Peripheral Nerve Block
2 major types of neuroaxial blocks
Subarachnoid (“spinals”)
Epidural
Caudal blocks are a different approach to the epidural space, so they are an epidural sub-type
Differences between Epidural and Spinals
Epidural: slower onset (potential space w/o fluid until you inject), do not puncture the dura, relatively high dose of local (serious toxicity if injected systemicall), CSF should not return from the needle, can be done at almost any level, 18G needle, more precise control over dermatomal level anesthetized
Spinal: relatively low dose of local (no toxicity), considered safe only in the lumbar spine, 22-27G needle, some control over dermatomal level anesthetized
Dermatomes you should know:
T4
T6
T10
L4
S1
T4 - Nipple line
T6 - Xyphoid process
T10 - Umbilicus
L4 - Anterior knee, medial foot
S1 - Lateral foot
Technical difference between thoracic and lumbar epidural
Angle of approach
(sharp downward angulation of thoracic spinous processes)
What determines potency of local anesthetics?
Lipid solubility
greater lipid solubility = greater potency (unlike inhaled anesthetics)
(tetracaine > bupivacaine > lidocaine > mepivacaine)
Complications of spinal/epidurals
Backache
Infection
Post-dural puncture headache
Hypotension, bradycardia, cardiac/respiratory arrest
