Anesthetics Flashcards
What are the volatile liquid general anesthetics?
halothane, isoflurane, desflurane, enflurane, sevoflurane (HIDES)
What is the gas general anesthetic?
nitrous oxide
What type of general anesthetics are inhaled?
volatile liquids and gas
What type of general anesthetics are IV?
thiopental (barbiturates), midazolam (benzodiazepines), propofol (phenols), morphine (opioids)
What are the local anesthetic drugs?
cocaine, procaine, tetracaine, lidocaine, bupivacaine
General anesthetics use what type of channel?
ligand gated
Local anesthetics use what type of channel?
voltage gated
What are general anesthetics?
drug induced absence of ALL sensations
What are the sensations that are absent with general anesthetics?
unconsciousness, analgesia, amnesia, loss of reflexes
How are general anesthetics mainly administered?
inhalational and IV
What is balanced anesthesia?
anesthesia with a mx of inhaled and intravenous anesthetics
What are the classes of sedative-hypnotics from high to low?
general anesthesia> deep sedation> moderate sedation> minimal sedation
What is the therapeutic indices range for inhalational anesthetics?
2 to 4
What are the kinetics of uptake and distribution of inhalational anesthetics?
- rate of entry controlled by respiration, a cyclic process
- elimination occurs in the lungs
What are the two drugs that are NOT eliminated by lungs?
methoxyflurane and halothane
What is tidal volume?
amount of air in lung when you take a breath
What is the rate of respiration?
number of breaths per minute
What is minute ventilation?
amount of air going in and out of lungs per minute
What is the minimum alveolar conc. (MAC)?
conc. that results in immobility in 50% of patients when exposed to noxious stimulus
If the MAC is larger, what amount of conc. is needed to have an effect?
more
If the MAC is smaller, what amount of conc. is needed to have an effect?
less
What are the factors that affect uptake of inhalation anesthetics?
solubility in blood and conc. of anesthetic agent in the inspired gas
What is the coefficient of of solubility in blood?
blood:gas partition coefficient
What does the blood:gas partition coefficient/index of solubility define?
relative affinity of an anesthetic for blood in comparison to air
How does solubility affect the rate of rise of its tension in the blood then brain?
the lower the solubility, the faster the rate (smaller B:G = more pressure = faster delivery to brain)
What can increase the rate of induction?
an increase in teh inspired anesthetic conc.
What is pulmonary ventilation?
when increased, it will speed up the uptake of an anesthetic with higher B:G partition coefficient
What is the hypothesis of the pharmacodynamics of anesthetics?
direct correlation between lipid solubility and potency
What receptor is the target for most general anesthetics?
GABAa
GABAa channel activity is increased in the presence of what drugs?
benzodiazepines, barbiturates, propofol, enflurane
What is the practical approach to evaluate the depth of anesthesia?
- if the eyelid blinks when eyelashes are touched
- if patient swallowing reflex disappears
- if respiration becomes irregular in the rate and depth
What can reduce the respiratory tidal volume?
an increase in the depth of anesthesia
What happens when potent halogenated agents are used?
arterial blood tends to vary directly with the depth of anesthesia
What can be used as an approximate index of dosage when potent halogenated agents are used?
hypotension
What is the cardiovascular effect on halogenated general anesthetics?
dose dependent reduction in blood pressure
What is the respiratory effect on halogenated general anesthetics?
reduce ventilation in conc.-dependent way by depressing medullary centers in the brainstem; reducing minute ventilation
What is an adverse affect of anesthetics?
malignant hyperthermia: rapid rise in body temp.
What are the symptoms of malignant hyperthermia?
hyperthermia, tachycardia, hypertension, acidosis, muscle rigidity
What makes malignant hyperthermia most common?
use of halothane and succinylcholine
What is the drug used to prevent death from malignant hyperthermia?
dantrolene
What is the main application of nitrous oxide?
adjuvant with other inhalational anesthetics
What is the percentage of nitrous oxide needed to have analgesia (no pain) as an effect?
20%
Can nitrous oxide achieve behavioral disinhibition, amnesia, or unconsciousness?
yes
40%- behavioral disinhibition
60%- amnesia
80%- unconsciousness
Are barbiturates good analgesics?
NO; can increase sensitivity to pain
What type of circulation do barbiturates have?
one arm-to-brain circulation
What occurs in the circulation of barbiturates?
decreases arterial pressure due to a reduction in cardiac output
What occurs in the respiration of barbiturates?
reduces minute ventilation by lowering the sensitivity of medullary respiratory center to carbon dioxide
Propofol induces anesthesia as rapidly as what other type of drug?
barbiturates; but has shorter half-life
How does propofol affect systemic arterial pressure?
decreases it due to peripheral vasodilation
What can occur at the site of injection for propofols?
apnea
Propofol is used mainly for what type of surgery?
“day surgery”
What type of drug is known as “milk of amnesia”?
propofol due to it being lipid soluble
What can benzodiazepines cause?
sedation, reduction in anxiety, amnesia, moderate depression of circulation and respiration
Are benzodiazepines analgesic?
NO; they are amnesic
What drug is used to reverse the action of benzodiazepines?
flumazenil
Out of diazepam, midazolam, and lorazepam, which has a more rapid onset?
midazolam
Are opioids an analgesic?
YES and very powerful
What are the effects of opioids?
- mild decrease in blood pressure
- impair ventilation, depress respiration
- increase chest wall rigidity
What is the antagonist used for opioid overdose?
naloxone
What are local anesthetics?
reversibly block impulse conduction along nerve axons that use Na channels
What are the effects of local anesthetics?
- block pain sensation
- cause vasoconstriction
- reduces bleeding
What type of chemistry do local anesthetics include?
lipophilic group connected by an intermediate chain to an ionizable group (aromatic ring + ester/amide + tertiary amine)
What are the esters of local anesthetics?
- cocaine (vasoconstrictor)
- procaine (vasodilator)
- tetracaine (vasodilator)
What are the amides of local anesthetics?
lidocaine (vasodilator) and bupivacaine (vasodilator)
What is the ONLY vasoconstrictor in local anesthetics?
cocaine
Are local anesthetics weak acids or bases?
weak bases
What form of local anesthetics penetrate the cell?
non-ionized form
What form of local anesthetics occupy the Na channels?
ionized form
What does epinephrine do during absorption in local anesthetics?
prolongs activity and reduces the dose and change of toxicity
What are vasoconstrictor substances?
reduce the absorption of local anesthetics from depot site by decreasing the blood flow
When should epinephrine NOT be administered?
when anesthetizing tissues with end arteries
What type of local anesthetics have a shorter half-life?
esters
What are amides metabolized by during elimination?
liver followed by hydrolysis (amidases)
How do ester anesthetics become inactive products?
through hydrolysis by plasma cholinesterase and live esterase
Local anesthetics have a HIGHER affinity for what states?
activated and inactivated states opposed to resting states
What is conformational dependent?
the binding of local anesthetics to Na channel
What type of channel do local anesthetics use?
voltage-gated Na channels
What are the toxicity and adverse effects of the central nervous system?
excitation, convulsion, respiratory depression
What are the toxicity and adverse effects of the cardiovascular system?
- direct effect on cardiac and smooth muscle
- indirect effect on autonomic nerves
