Anesthesia, NMB, and Local Flashcards
Define: blood:gas ratio
How much of the drug is bound to protein in the blood (inactive): how much of the drug is free molecules (active)
Define: MAC
minimal alveolar anesthetic concentration (aka potency): concentration of inhaled drug as a percent of inspired air at which 50% of the population will be TKO’d
Characteristics that will increase MAC/decrease potency
hyperthermia, red hair, hypernatremia, increased NTs
Characteristics that will decrease MAC/ increase potency
hypothermia, old age, opioids, hyponatremia, lipid soluble, pregnancy/postpartum
What can you do to increase uptake and distribution of an anesthetic
- increase partial pressure of drug in inspired air
- increase alveolar ventilation
- decrease functional residual capacity
- decrease blood solubility
- decrease CO
- 2nd gas effect
define: second gas effect
give one gas to decrease lung volume, give a second less potent drug to maintain anesthesia
examples of inhaled anesthetic
NO2, Halothane (fluranes)
examples of “fluranes”
isoflurane, desflurane, sevoflurane
CNS effects of inhaled anesthetics
dose dependent depression of EEG, sensory/motor potentials, cerebral metabolism rates; increase in cerebral blood flow > ICP
CVS effects of inhaled anesthetics
decrease in systemic resistance and mean arterial pressure, redistribution of blood flow, Iso and Des increase HR
Respiratory effects of inhaled anesthetics
decreased tidal volume and reflex to hypoxia; increased respiratory rate and relaxation of smooth muscle
Neuromuscular effects of inhaled anesthetics
relaxed skeletal muscle, malignant hyperthermia
Thiopental and Methohexital
- class
- mechanism
- use
- Barbituate
- GABA agonist, NMDA-glutamate antagonist
- hypnosis/sedation with rapid onset/short duration > induce anesthesia
Propofol
- mechanism
- use
- side effects
- consideration
- GABA agonist, alpha2 antagonist
- sedation and hypnosis, antiemetic
- propofol infusion syndrome: met acidosis, heart failure, rhabdomyolysis, hyperkalemia, renal failure
- allergies to soy and egg
Etomidate
- mechanism
- use
- side effects
- GABA agonist
- elderly or minimal cardiac reserve
- pain on administration, PONV, involuntary myoclonic movement, decreased cortisol
Ketamine
- mechanism
- use
- side effects
- no idea, dissociative anesthesia
- cardiovascular stimulation, people who are bleeding out/hypotensive
- dilerium, hallucinogen, nightmares, nystagmus, salivation, lacrimation
Dexmedetomide
- mechanism
- use
- a2 agonist, natural sleep
- morbidly obese patients
Succinylcholine
- class
- mechanism
- side effect
- depolarizing NMB
- binds to ACh receptors, ACh agonist
- dysrhythmia, sludge, malignant hyperthermia, hyperkalemia
‘Curoniums’
- class
- mechanism
- reversal
nondepolarizing NMB
- blocks ACh receptors
- AChE inhibitors
what is unique about Atracurium
histamine release > hypotension and tachycardia
what is unique about pancuronium
can’t use with renal insufficiency
what is unique about rocuronium
can be reversed by sugammadex
Reversal of NMBs
AChE inhibitors (edrophonium, neostigmine, pyridostigmine) and anti-muscarinics (glycopyrrolate)
Local anesthetics
- active form
- mechanism of action
weak base: nonionized form travels across the membrane, ionized form is active within the cell. Blocks the binding site of the inactivated sodium channel
Two types of local anesthetics with examples
esters (procaine, cocaine, benzocaine) and amides (lidocaine, bupivacaine, and mepivacaine)
Which nerves are the most sensitive to local anesthetics
nerves with the smallest diameter, most myelination, and fastest firing rate: Type B > Type C > Adelta > Agamma and Abeta> A alpha
Nerve type responsible for sharp pain
Adelta
Nerve type responsible for dull pain
C
What factors influence the absorption of a local anesthetic
most absorption in highly vascular tissue, lipid solubility, presence of alpha1 agonists
How do you keep the local anesthetics from spreading into systemic circulation
administer with an alpha 1 agonist
which anesthetic comes with it’s own alpha agonist
cocaine: it is a norepi reuptake inhibitor, thus more norepi in nerve terminals, more alpha stimulation
where does metabolism of local anesthetics take place
esters: tissue esterases
amides: liver amidases
special considerations of local anesthetic metabolism
esterases have high phenotypic variation, there are slow and fast metabolizers-> watch your patient
amides need a properly functioning liver
Local anesthetic, systemic toxicity
nervous toxicity, cardiovascular toxicity, methemoglobinemia
LA early CNS toxicity
excitation: decreased inhibition, talkativeness, sensory disturbance, restless, tremor
LA late CNS toxicity
depression: lethargy, hypotension, bradycardia, decreased respiratory rate, seizure
LA cardiotoxicity
Bupivacaine: reduced cardiac conductivity, excitability, contractility, arrhythmia, hypotension, bradycardia
Local toxicity for LAs
Neuronal injury, transient neurologic symptoms (lidocaine), allergies (esters)
