Anesthesia Flashcards
Of the different nerve fibers, which is the thickest and fastest conducting? These fibers are also most susceptible to damage with tourniquet placement ?
A fibers!! These are the thickest and fastest at transmitting information.
C fibers are the thinnest and not myelinated. These transmit CHRONIC, burning PAIN.
D fibers: are thin but myelinated and transmit short lived pain.
What track transmits pain?
Spinothalamic!
relays sharp pain, temp, crude touch, and noxious stimuli. Originates from periphery and concludes in the dorsal horn on the contralateral side of the thalamus.
- BRAIN STEM LESION: therefore a spinal cord lesion produces contralateral pain deficits,
- ** SPINAL CORD LESION: ipsilateral touch and proprioceptive deficits.
What is the resting state of a nerve cell?
How do local anesthetics act on cells?
-70mv with lots of Na outside the cell.
*** local anesthetics act on the Na/K ATP pump. INHIBIT depolarization of the cell, preventing Na to rush in…therefore propagation of a signal (pain) is not allowed. ( no action potential produced)
Local anesthetics are weak ______?
Weak bases! manufactures in the form of a hydrochloride salt. Contains protonated and unprotonated forms… but only the unprotonated molecules can diffuse across nerve cell membrane. Inside the cell, the molecule becomes protonated and therefore is trapped inside the cell.
Why are local infections weary to have in the use of a local anesthetic?
The infection causes an decreases pH outside the cell, therefore more PROTONATED molecules remain outside the cell membrane.
Therefore infections are acidic and reduce the effectiveness of locals. Inject local proximal to the site.
Tell me about the differences of ESTERS and AMIDES?
ESTERS: (procaine), metabolized in the blood( Hydrolysis by pseudocholinesterases). greater risk for allergies.
AMIDES: (lidocaine), used more frequently. Metabolized in the liver. Less risk for allergy. Excreted by renal system. Concern for toxicity… CHF or hepatic failure warrants extra concern.
Can I use lidocaine with epi in the digits?
according to mcglamry.. YES! research supports use, no need to withhold. But still administer cautiously. using epi means you can do surgery without tourniquet at times.
What is the concentration of Epi used with lido?
Most common side effect?
1:100,000 or 1:200,000
Most common side effect is tachycardia.
Epi reduces need to tourniquet or compression
Epi also increased acidity of the solution! FYI.
What can reduce irritation when administering a local anesthetic?
Quick penetration and slow infiltration.
common side effects: pain, ecchymosis, hematoma, infection, nerve lac, or tissue irritation.
How can anesthetics affect the CNS?
They selectively depress inhibitory centers = excitation -> generalized convulsions.
also could cause coma, resp arrest, and death, most commonly due to toxic dose, IV admin.
What is the order of nerve sensory inhibition with application of anesthetic?
pain > temp > touch > proprioception
Why is sodium bicarb used with local injections?
This can reduce irritation with administeration and also increase the pH to make the solution more basic and more readily diffuse across the cell membrane.
SCIATIC NERVE BLOCK
L4, L5, S1-3
- this nerve goes through the greater sciatic foramen.
- nerve is encountered medial to the ischial tuberosity
-
What is the one nerve that innervates the foot and does not come off the sciatic nerve?
SAPHENOUS NERVE - branch of the femoral nerve.
TIBIAL NERVE
L4-S3
- innervates the posterior leg and sole of foot
- 0.5-1cm lateral to midline of popliteal fossa (follows direction of sciatic before split)
- great for achilles lengthening, grastroc recession, etc
COMMON PERONEAL
- L4-S2
- innervates muscles on lateral and anterior aspects of leg as well as the dorsum of the foot.
- courses laterally across popliteal fossa–> hit it before it divides into deep and superficial peroneal near prox PL fibers. Palpate along fibular neck, it sits shallow here.
- good for post op pain management
SUPERFICIAL PERONEAL BLOCK
- L4-S1
- lower anterior leg and dorsum foot
- intermediate and medial dorsal cutaneous branches
- Hit it along the anterior border of the fibula
- Intermediate branch can be felt along tibiofib syndesmosis and will be visualized when taut ( PF foot)
- medial branch overlies the EDL, parallel to EHL. ( be careful of in ankle arthroscopies): HIT 1 cm prox to medial malleolar level, lateral to EHL
DEEP PERONEAL
- First dorsal interspace
- Travels with anterior Tib artery
- Sits between TA and EHL
HIT it 2.5 cm prox to ankle joint betwen EHL and EDL
POST TIB NERVE
- provides to medial posterior heel and plantar foot, posterior lower leg
- posterior to PT artery
- HIT It: palpate artery at medial malleolus, then most 1cm superior to this and and inject
What is CRPS Type 1 vs 2?
Type 1: regional sympathetic dystrophy. Occurs after illness or injury not directly damaging nerves in the affected limb.
Type 2: follows distinct nerve injury.
SURAL NERVE
Formed by the medial sural nerve ( br of tibial n), and the peroneal communicating branch ( lateral sural n or common peroneal n)
- lateral border to Achilles
- HIT IT: superior or inferior to lateral malleolus,
SAPHENOUS N
L3-4
- only branch to innervate the foot that is not derived from sciatic n.
- HIT IT: LATERAL to the great sapheous vein, before it crosses the ankle joint
ANKLE BLOCK
tibial, superficial peroneal (medial and intermediate dorsal cutaneous),deep peroneal, saphenous, sural
What is a MAYO block
saphenous, deep peroneal, medial plantar, medial dorsal cutaneous.
- performed for 1st MPJ procedure.
1. needle dorso-lateral to plantar
2. then dorso-lateral to dorso-medial
3. then dorsomedial to plantar
4. plantarly, directed medially to laterally
DIGITAL N blocks
- 2 pt: dorsal medial and dorso lateral
- anesthetic applied to 2 dorsal and 2 plantar digital nerves.
What is one way to anestitize a patient without a needle prick?
Topical! Good for children.
- EMLA is a good one ( eutetic mixture of local anesthetic) : side effect is methemoglobineria
What drugs cause the increased risk of Malignant hyperthermia?
Signs?
Treatment?
Halogenated Anesthetic agents and the depolarizing neuromuscular blocker, succylicholine.
Signs: rigidity, increased O2 consumption, CO2 production, tachycardia, and increased body temp.
Treatment: dantrolene sodium
What are the gene: ric names for the following benzos?
- lorazepam:
- diazepam:
- midazolam
Properties?
Reversal agent?
- lorazepam: ativan
- diazepam: valium
- midazolam: versed
Properties: anxiolytic, anticonvulsant, and muscle relaxing ( NO ANALGESIA- adjunct with opioids)
*** work like GABA inhibiting effects
Be careful wit midazolam = resp depression.
Reversal = Flumazenil
What is a common medication used for induction of general anesthesia?
Propofol: administered IV.
- sedative hypnotic effects
- Adverse = Resp depression
MOA: GABA and NMDA receptors are activated on spinal cord neurons.
Who can Ketamine be used in surgical patients most commonly?
When is Etomidate good anesthetic?
Children- less unpleasant reactions. ( but versed can be given as an adjunct in order to prevent these from occurring).
Etomidate: another short acting like ketamine. HEMODYNAMIC stability and minimal resp depression. NO ANALGESIA. Good for reduction of fractures, etc.
Adverse = N/V and pain on injection.
What do Fentanyl, sufentanil, and alfentanil have in common?
Synergistic effects occur with opioids and what other medications?
they are all OPIOIDS!
- hemodynamic stabilty.
- RESP DEPRESSION
- Fentanyl > morphine (100x)
- synergistic effects between opioids + benzos + propofol + volatile anestherics when administered together. Therefore a reduced amount of each agent is needed all together = BALANCED ANESTHESIA.
What are isoflurane, sevoflurane, and desflurane?
Fluorinated hydrocarbons used in inhaled anesthetics.
Delivered directly to lungs and taken up in vasc and brought to brain.
- LOC, amnesia, analgesia, and NM blockage, blunted autonomic reflexes.
- – patients need to be intubated at this time! and vitals should be monitored.
What is the max dose of lidocaine?
Bupivacaine?
Lidocaine: 300mg or 500mg with epi added
Bupivacaine (marcaine): 175mg or 225mg with epi
What is IV conscious sedation?
drug induced depression of consciousness.
- patients can respond to phy and verbal stimuli and can breathe, but anxiety is relieved and overall they are relaxed.
- good for minor procedures,
- consists of 2mg midazolam and 2 mg of morphine
- Make sure these patients are hooked up and vitals are monitored. NO anesthesia team required.
What is monitored anesthesia care?
Similar to IV conscious sedation, but DEEPER sedation and patient cannot be easily aroused but they are able to response to repeated or painful stimuli.
this is good for more complex cases, and anesthesia team manages vitals.
- Surgeon will administer local anesthetic to help with comfort and pain.
What is regional anesthesia?
Peripheral nerve block or central neural blockade.
This is the most common form of anesthesia used in podiatry! ( mayo block, ankle block).
- Subarachnoid block ( spinal)
- epidural block
General anesthesia ?
5 components?
3 Phases?
When a patient loses consciousness and the ability the respond purposefully. 5 components: 1. LOC 2. locking of pain (analgesia) 3. loss of memory ( amnesia) 4. Muscle relaxation/no movement 5. blunting of autonomic reflexes.
achieved with IV and inhalation agents.
A. induction
B. maintenance
C. emergent phases
specific nerve blocks are often still done with this as well!
What are adverse effects related to local anesthetics?
- systemic effects due to toxicity
numbness of tongue, twitching, restlessness, vertigo, tinnitus, slurred speech, convulsions, anxiety, hypotension, decreased CO, and cardiac collapse.
What is a product of ester local anesthetics metabolism that cause allergic reactions?
paraaminobenzoic acid
This reduced ester use in general population.
** skin eractions, resp collapse, anaphylactic shock.
Why do I draw up the corticosteroid first and the local anesthetic second?
More risk for allergic reaction to preservative in locals called METHYLPARABEN.
When Dr. Feilmeier orders a MAC for anesthesia what does that mean?
a monitored anesthesia care (MAC) is a planned procedure during which the patient undergoes local anesthesia together with sedation and analgesia. Actually MAC is the first choice in 10-30% of all the surgical procedures.
*** this is not a general anesthesia. The patient is awake and not fully put under.
