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
How is a dose related hepatotoxicity from methotrexate detected in a patient?
Seen as an enzyme elevation (not cirrhosis)
What is the antidote used for OD/toxicity caused by Methotrexate?
Leucovorin, given 24 hours after each weekly dose.
What is the mechanism of action of Methotrexate? What makes it also a good cancer drug?
Inhibits AICAR… inhibiting immune cell proliferation and also inhibits pro-inflammatory cytokines.
By inhibiting proliferation in general, it inhibits cancer cells, since they too are proliferating
What latent diseases can be re-activated by TNF alpha directed MABs?
Latent TB can be activated so must screen for it before starting treatment
In rare cases, can also activate SLE
What is the use of penicillamine?
Interacts with lymphocyte membrane receptors, may interfere with DNA synthesis (unclear
Used for progressive-erosive RA that can’t be controlled by conservative therapy
Contraindicated in patients with other autoimmune diseases
What are the uses and limitations of use for acetominophen in RA patients?
Can be used to relieve pain as an adjunct to an anti-inflammatory.
Limitation - HAS NO ANTI-INFLAMMATORY effects.
Describe the mechanism and use of Tofacitinib.
JAK inhibitor, used in adults with severe RA that didn’t respond to Methotrexate
Contraindicated in children and patients with liver problems
Describe the mechanism of action and use of Abatacept?
ANTI Tcell/TNF drug
Binds CD80 subunit on Antigen Presenting Cell (APC)
Prevents T-Cell activation
Describe the mechanism of action of Alefacept
Binds CD2 portion of TCell - preventing activation
Used in plaque psoriasis
What is the mechanism of Adalimumab, Infliximab, Etanercept, Rituximib
antibodies against TNF, preventing inflammation
Of the MABs, treat Juvenile arthritis
Etanercept
Of the MABs, treat plaque psoriasis
Alefacept
How long do DMARDs and Mabs generally take to show effects?
4 weeks to a year
What is the role of MHC and Tcell surface antigens in T-Cell activation?
MHC is recognized by T-Cell surface receptors as part of the activation process
Discuss the use of glucocorticoids as a treatment for RA. Pros/Cons
Can help with pain if given intra-articularly
Can cause adrenal gland suppression, hypomania, uclers
