3 - Ortho: Anesthetics Flashcards
Describe the factors that affect the activity of local anesthetics.
activity is a function of their lipid solubility, diffusibility, affinity for protein binding, percent ionization at physiologic pH, and vasodilating properties.
What explains the differences in onset, potency, and duration of action of various anesthetics.
They must enter the cell through the cell membrane. Differences in their physical properties (lipid solubility) cause different rates of entry in and out of the cell.
What is the mechanism of action of Local anesthetics?
reversibly bind to voltage gated Na+ channels, block influx and thus stop APs/nerve conduction
Describe the two classes of local anesthetics and how to remember which is which.
Esters - cocain, chloroprocaine, Procaine, Tetracaine “the caines”
Am”i”des - Bupivacaine, Lidocaine, Ropivacaine, Etidocaine, Mepivacaine “rule of i”
What are vasoconstrictors (epinephrine/phenylephrine) used for in conjunction with local anesthetics? When are they contraindicated?
They are used to prolong the effects of the anesthetics by reducing absorption, prolonging blocked, and causing capillary constriction
They should not be used in the ear, nose, fingers, toes, penis
What are the pros of ester local anesthetics?
Fast acting
Unstable in solution and can cause allergic reactions
What are the pros/cons of amide local anesthetics?
Lidocaine, Prilocaine
Commonly used in t regional and epidural or spinal techniques
Heat-stable, long shelf life, longer acting
Slow onset
What is the duration of action of lidocaine with and without epinephrine?
With epi - 3hrs
Without Epi - 30 mins to 2 hrs
What is a hematoma block?
Analgesic technique using a local anesthetic to allow for manipulation of a fracture without a need for full anesthesia
Most commonly used for distal radius and ulna fractures
Define regional anesthesia
Rendering a specific area of the body insensitive to stimulus of surgery or other instrumentation
Can be used for out patient surgery, post-op, during labor and delivery, and as a dx or therapy for patients with chronic pain syndromes
What are the various types of regional anesthesia?q
Topical - apply to mucous membrane (eye drop), could get toxic
Local/Field - subcutaneous to get nerve endings (suturing, minor superficial surgery (mole), could get toxic
Intravenous block (bier block) - injection for entire limb/extremity anesthesia, limited by tolerance of tourniquet
Peripheral (nerve) or plexus block - injected near the course of a named nerve, technically complex and could cause neuropathy
Central neuraxial (epidural, spinal) - injected into CSF, profound anesthesia of lower abdomen (done at L3/L4, can puncture the dura and cause major complications also must watch for migration up the chord to the cerivical levels C3/4/5 phrenic !!
Why is lidocain used instead of nabivecaine for nerve blocks (esp. near a joint)?
Nebivecaine has been found to be chondrotoxic: causing breakdown of cartilage that it comes in contact with.
Describe the likely complication of local anesthetics based on the symptom:
- Headache
- Infection
- Methemoglobinemia
- Dural puncture
- Meningitis secondary to spinal anesthesia
- prilocaine can cause this (delayed onset)
Describe the inherent contradiction involved in initiating DMARD treatment early.
They cause toxic side effects, so starting treatment early can cause serious problems in the patient while trying to help them.
Describe the dosing of leflunomide
Has a significantly long half life, so it is not able to be monitored effectively, given as a loading dose then is tapered down to avoid toxicity or something
