week 2 regional & locals 4 of 4 Flashcards
amides are metabolized by
P450 enzymes in the liver
greatest to least metabolism of amides
prilocaine>lidocaine>mepivacaine>ropivacaine>bupivacaine
comparing amid metabolism to ester metabolsim
amid metabolism is consistently slower than ester
abnormal liver function or decrease blood flow to liver results in what concerns with amides
toxicity
T/F
amides are excreted by the kidneys very little
True!
what two locals are metabolized to PABA and associated with anaphylaxis
procaine and benzocaine
what metabolizes ester local anesthetics
3 names for this one thing
plasma pseudocholinesterase (plasma cholinesterase or butyrylcholinesterase)
why do esters not accumulate in blood
ester hydrolysis is very rapid in the blood stream (excreted in the urine)
esters are derived from
benzoic acid
what is important about CSF and the termination of action of local anesthetics
The CSF lacks esterase enzymes, so termination of action of LA intrathecally depends on redistribution into the bloodstream as it does for all other nerve blocks
as soon as you stick someone for a local what is the absolute first thing you do
what is the second thing you do
ALWAYS ASPIRATE
second- test dose- check HR, numbness around lips, tinnitus
what two drugs can cause methemoglobinemia- and many hospitals/ facilities do not permit use
Prilocaine: causes methemoglobinemia (generally not used)
Benzocaine (common ingredient in topical LA sprays) can cause
treatment for methemoglobinemia
IV methylene blue (1-2 mg/kg of a 1% solution over 5 minutes)
what does methylene blue do to the FE
FE3-FE2
ferric to ferrous
LA toxicity-
Neurological:
Early symptoms:
Circumoral numbness, tongue paresthesia, dizziness, tinnitus, blurred vision
LA Toxicity
Neurological:
Excitatory signs:
Restlessness, agitation, nervousness, feeling of “impending doom”,
Muscle twitching may preceded “tonic-clonic” seizures
Higher blood concentrations (toxicity) may produce CNS depression- coma, respiratory arrest
Seizures:
prevention-
benzodiazepines & hyperventilation (raise seizure threshold)
Propofol (0.5-2 mg/kg) –quickly terminates seizure activity after onset (careful with airway/hypotension etc… )
Benzodiazepines and barbiturates may terminate seizure as well
what is the concern with respiratory and metabolic acidosis as it relates to seizures
it will decrease (lower) seizure threshold
Cocaine toxicity: patient presentation
Restlessness, emesis, tremors, convulsions, arrhythmias, respiratory failure, cardiac arrest
Unintentional injection of large volumes of chloroprocaine in SA space (intended for epidural space: resulting in)
Total spinal
Prolonged neurological deficits (direct neurotoxicity and/or preservative– now prepared preservative free)
total spinal occurs when what spinal level is reached
T4-cardiocelerators
what block did we talk about last semester that patients can end of with a total spinal
retrobulbar block
patient is having an emergency C section which local anesthetic will you administer and why?
Chloroprocaine- fast onset
TEST
lidocaine neurological toxicity
Neurotoxicity (cauda equine syndrome/transient neurological symptoms)
