Exam 1 Flashcards
What dermatome does the clavicle correlate with?
C4
What dermatomes correlate with the nipples?
T4-T5
What dermatomes correlate with the xiphoid?
T6-T8
What dermatomes correlate with the inferior border of the scapula?
T7
What dermatomes correlate with the umbilicus?
T10
What dermatomes correlate with the Superior border of the iliac crest?
L4
What dermatomes correlate with the perineum?
S2-S5
What are the 3 classes of nerves?
motor, sensory and autonomic.
What class of nerves transmit sensations such as touch and pain to the spinal cord and from there to the brain.
sensory
What class of nerves Controls the caliber of blood vessels, heart rate, gut contraction and other functions not under conscious control.
autonomic - the PNS and SNS
What class of nerves convey messages for muscles to contract and when they are blocked muscle paralysis results.
motor
What is the goal of every regional anesthetic
Sensory anesthesia (or analgesia)
What is local anesthetics Mechanism of action
Local anesthetics bind to sodium channels, in the inactivated-closed state, thus preventing them from converting to activated-open or rested-closed.
When are Sodium channels not permeable to sodium and can not propagate an action potential.
in the inactivated-closed state
LAs diffuse through What
the lipid bilayer of the cell [the uncharged portion)
What does the charged portion of LA’s do once the uncharged portion diffuses through the lipid bilayer?
the charged portion accesses the Na+ channel and prevents an action potential from forming by blocking Na+ entry into the cell (the cell remains non depolarized)
Though local anesthetics bind to sodium channels in the inactivated- closed state, they only gain access during?
the activated-open state
What is Differential Blockade
Local anesthetics act on nerves at a different (or “differential”) rate, depending on The thickness of the nerve. Thicker nerves need more LA (exception to the rule is B pre-ganglionic sympathetic fibers)
Motor fibers are (blank) than sensory fibers and therefore it is possible to get sensory anesthesia, without getting muscle paralysis.
larger
What fibers are the most susceptible to conduction blockade
Preganglionic type B (despite being larger than type C fibers.)
Myelin makes the nerve fiber more or less susceptible to conduction blockade?
more
How many nodes of Ranvier does it take to block conduction?
approx 3
As nerve size increases what happen to the nodes of Ranvier?
the nodes are more spread out and it’s harder to block them
What is Nerve Fiber TypeA Alpha”s Function
Proprioception, large motor
What is Nerve Fiber TypeA Beta”s Function
Touch, pressure, small motor
What is Nerve Fiber TypeA Gamma”s Function
Muscle spindles
What is Nerve Fiber TypeA Delta “s Function
Pain, temperature (fast pain, touch, cold temperature)
What is Nerve Fiber Type B’s function
Preganglionic autonomic
What is Nerve Fiber Type C dorsal root’s function
Pain (“slow” pain and temperature)
What is Nerve Fiber Type C sympathetic’s function
Postganglionic
Which nerve fibers have heavy myelination
All Type A’s (alpha, beta, gamma, delta)
Which nerve fibers have light myelinaiton?
Type B
Which nerve fibers do not have myelination?
Type C
Which never fibers diameter is 12-20 (um)
Type A Alpha
Which never fibers diameter is 5-12 [um)
Type A Beta
Which never fibers diameter is 15-30 um
Type A Gamma
Which never fibers diameter is 2-5 (um)
Type A Delta
Which never fibers diameter is <3 (um)
TypeB
Which never fibers diameter is 0.4-1.2 um
TypeC Dorsal root
Which never fibers diameter is 0.7 - 2.3 um
TypeC Sympathetic
What are some factors that affect nerve blockade
Tissue pH, C02 tension, local ion gradients, frequency of nerve stimulation
What group of LAs are metabolized mostly by the liver
Amides
What group of LAs are metabolized by plasma cholinesterase and the byproduct is PABA
Esters
Which LAs are Amides;
Lidocaine, Mepivacaine, Bupivacaine, Etidcoaine, Prilocaine
Which LA’s are esters?
Cocaine, Procaine, Chloroprocaine, Tetracaine
LAs that are more protein bound have less What
ability to cause toxicity
The more lipid soluble an LA is the more (blank) it is?
potent
pKa- agents that have a pKa that is closest to the body’s pH will
have the fastest onset (because more will be unionized)
What would cause a faster onset and longer duration of blockade of an LA
larger volume and concentration: the more injected (larger volume),
What can limit systemic absorption and maintain the drug concentration in the vicinity of the nerve fibers.
use of vasoconstrictors (epi)
Which LA would adding epi have less of an effect on and why? Bupivacaine or Lidocaine?
less of an effect on bupivacaine than lidocaine, presumably because of the greater lipid solubility of bupivacaine compared to lidocaine).
Absorption is influenced by:
dose and pharmacologic properties of the individual drug (lipid solubility, protein binding).
Which has a faster onset Subarachnoid blocks or epidurals?
subarachnoid blocks
Does the addition of epi to LA’s change rate of onset?
No
What does addition of sodium bicarbonate to the LA do?
Speeds the onset and spread of the block by increasing pH of the LA so more is in the unionized form
At what temperature would a LA work faster?
Body temp
List (High to low) what injection sites from the notes would have greater peak plasma concentrations and shorter DOA. (Also greater risk for toxicity)
Intercostal space>Caudal>Epidural>Brachial plexus>sciatic/femoral nerves
What is order of their “typical” presentation, of local anesthetic toxicity?
- Circumoral numbness (numbness ot the tongue or lips)
- Metalic taste
- tinnitus
- Lightheaded, Slurred speech, Visual Disturbances
- Muscle twitching
- Vertigo
- Seizures soon afterwards and unconsciousness
- CNS depression and Coma
- Respiratory Arrest
- Cardiovascular collapse
How long is the pt monitored after initial insertion of a block?
Monitoring during the block (and for 30 minutes after)
State monitoring modalities required during administration of a regional anesthetic
Airway, Oxygenation via pulse ox, Heart Rate (via pulse ox and/or ekg) and Blood Pressure
Describe the equipment which must be available during the administration of a regional anesthetic, especially when “off site.”
- Source of oxygen, suction apparatus, airway equipment and positive-pressure ventilation.
- Additional equipment if indicated (nerve stimulator, c-arm, ultrasound)
