pharm-LAs pt 2. Flashcards
(88 cards)
- what physical change causes pregnant (and obese) persons to require a change in the amount (cc) of neuraxial anesthesia
- what is the hormonal reason?
- there is a narrowing of the spinal column in pregnant, which results in needing less LA to reach the appropriate level
- progesterone may change protein binding leaving a higher free fraction of the drug
- name reasons why a LA would be more likely to cross the placenta:
- what LAs would be least likely to cross the placeta?
- what would happen if the baby was acidotic from fetal distress?
- the less protein bound the LA is, the greater the chance of crossing the placenta
- esters usually dont cross becaust they are metabolized too fast
- ion trapping of the ionized LA in the distressed fetus
what are the systemic effects of LA toxicity?
cardiovascular
central nervous
neruotoxic
allergic
what agents are most likely to cause system toxicity in order from GREATEST –TO– LEAST:
2-chloroprocaine, etidocaine, mepivicaine, prilocaine, procaine, lidocaine, tetracaine, cocaine, dibucaine, bupivicaine
- COCAINE
- DIBUCAINE
- TETRACAINE
- BUPIVICAINE
- ETIDOCAINE
- MEPIVICAINE
- LIDOCAINE
- PRILOCAINE
- PROCAINE
- 2-CHLOROPROCAINE
mnemonic:
“"”cool dudes try bringing everyone more laughs;
people person? 2-cool”””
cocaine, dibucaine, tetracaine, bupivicaine, etidocaine, mepivicaine, lidocaine
prilocaine, procaine, 2-cloroprocaine
systemic effects based on HIGHEST to LOWEST blood flows:
-subarachnoid,-epidural,-paracervical,-caudal,-trachea,-intercostal, -brachial plexus, -subcutaneous,
- trachea
- intercostal
- caudal
- paracervical
- epidural
- brachial plexus
- subarachnoid
- subcutaneous
what kind of duration does a LA have in a highly perfused area?
LA has a shorter duration the more highly perfused the area
low doses of LAs do what to blood vessels?
high doses do what?
low doses vasoconstrict
high doses vasodilate
why does LA cause vasodilation?
- -has direct effect on cardiac and smooth muscle mebranes (remember, blocks sodium channels and interfere with calcium)
- -also has indirect effect on autonomic nerves
why do LAs cause bradycardia?
because the SA node is fast leaking sodium channel (LAs block sodium channels)
what cardiac effects will you see from local anesthetics?
- bradycardia
- increased PR interval
- wide QRS
- AV block
- decreased contractile strength (except cocaine)
- decreased automaticity and conductivity
- cardiac arrest (cocaine especially)
what vascular effects will you see with LAs?
- smooth muscle relaxation resulting in vasodilation (except ropivicaine and cocaine)
- inhibition of c-AMP= further CV effects
how is cocaine different?
it inhibits reptake of NE (causes hypertension, vasoconstriction and arrhythmias)
If your patient has had intravascular injection of a LA and he/she takes alot of epi and atropine to come around, what LA was used?
bupivicaine
- what patient population has a higher incidence of CARDIOtoxicity from LAs?
- what is the reason?
- obstetrics
2. unknown, but lower doses are recommended d/t spinal changes so use lower doses.
- what neuro issue from toxicity leads to increased o2 consumption?
- this rapidly becomes what respiratory issues(___ & ___)
- these cause what issue (ph____)?
- these all cause what cardiac issues (_____&______)
- seizures
- hypoxia and hypercapnia and acidosis
- acidosis
- negative inotropic and negative chronotropic
- what does interlipids do?
2. how long might it take for your patient to fully recover from toxicity even with interlipids?
- extracts lipid soluble bupivicaine from the blood or enters the tissue and blocks bupivicaine (tx for cardiac and cns toxicity)
- may take 1 hour for it to resolve toxicity
- what is bolus dose of interlipids?
2. what is the infusion dose?
- 1.5 ml/kg bolus over 1 minute, repeat every 5 minutes
2. infusion at 0.25 ml/kg/min increase to 0.5 ml/kg/min if needed
what are the CNS side effects?
–they vary with plasma level
1st_ circumoral and tongue numbness occurs at low doses
2nd_ sleepiness, lightheadedness, visual and auditory disturbances, vertigo, tinnitus and restless are next
3rd_muscle twitching, excitability then seizures
4th_transitional phase of excitement, then cns depression, then coma
how do LAs affect the cns (what is the action)
depress cortical inhibitory pathways leading to unopposed excitatory activity
what is the best way to prevent toxic side effects?
- use the lowest dose of LAs
2. pre-treatment with benzos can raise seizure threshold
seizure management from LA toicity:
- prevent hypoxemia, hypercapnia and aspiration
2. give benzos or barbs
neurotoxic effects:
- how often and from which method of administration?
- what is the range of symptoms?
- any LAs more than others?
- what else can it be confused with?
- rare, but usually follow SAB and epidural administration
- range from patchy numbness to persistent weakness to severe syndromes
- certain LAs have been implicated more than others
- differential diagnosis-can be confused with nerve damage from positioning
what are specific neurotoxic effects?
- transcient radicular irritation
- cauda equina syndrome
- anterior spinal artery syndrome