Anesthesia Flashcards
Why Diethyl Ether was replace by halothane?
bc it is highly flammable
General Anesthesia component:
Lost sensation Lost consciousness Amnesia Relaxation of skeletal muscles suppression of reflexes.
Inhalation end-name?
’‘-ane’’
IV anesthetic agents end-name?
’‘-al’’ exept for Barbiturates, benzo ‘‘-am’’ and Propofol
Steps of drugs use in anesthesia
Premedication Induction agent Volatile agent and anesthetic gases Analgesics Muscle relaxants Reversal agents
Type of anesthetics often use for induction?
Intravenous anesthetics
Structure of IV agent?
IV agent have ring structures
Structure of Volatile anesthetics?
volatile do not have ring structure, but are small molecules with substitutions on the carbon chain.
Partial pressure =
Partial pressure of a gas is the driving force that get the drug from the alveolus into the blood, and then from the bllod into the brain.
Concentration of the drug (%) x the atmospheric pressure (760mmHg)
mix of gases need to include:
Oxygen
Most of the removal of general anesthetics is by
exhalation
NOT BY METABOLISM
All general anesthetics are lipid- or water-soluble?
Lipid soluble!
The Minimal alveolar concentration (MAC) is
the Concentration that will produce a surgical level of anesthesia in 50% of humans.
MAC is alter by:
Disease
presence of others drugs
Increasing MAC mean increasing ____.
Levels of CO2.
Increasing MAC can lead to
Respiratory depression (respiratory minute volume) Cardiovascular depression (BP)
Nitrous Oxide caracteristic
Is a GAS Majority are exhaled (NOT METABOLIZE) Good for pain relief Low solubility (move quickly in the brain) Do not decrease BP or respiration rate
Halothane caracteristic
Is soluble and dissolve in blood. (less of it immediately available to enter the brain)
Not compatible with epinephrine.
Metabolized 15%
Rare toxic effect
Isoflurane caracteristic
No production of toxic metabolites
Good muscles relaxant
Possible to use epinephrine
Avantages of IV anesthetics
Less respi and cardiovasc depression
RAPID ONSET with short duration
Wider margin of safety
Recovery of patient less difficult
Most commun inhalation anesthetics:
Nitrous Oxide
Halothane
Isoflurane
Sevoflurane
Classic barbiturate used for induction:
Thiopental
Most common IV anesthetics:
Thiopental (barbiturates), Midazolam (benzo), Etomidate, Propofol and Ketamine
Thiopental caracteristic:
Rapid onset and wear off quickly too
half-live longer bc stay in adipose tissue
Propofol caracteristics:
Rapid onset
Shorter half-life
Context-sensitive half-life is
how the drug can accumulate in other body tissues (taking more time to get ride off)
High half-life for:
Benzodiazepam (less for midazolam) and Barbiturates
Conscious sedation can be reach with
Opioids + midazolam
Fentanyl and Remifentanyl(more powerful) use as
induction agents for short procedures
Neurolept analgesia is
Fentanyl + antipsychotic
Ketamine
STIMULATE cardiovasc system
Psychiatric side effects: Dissociative Dysphoria
Major site of action of general anesthesics:
Inhibition: GABA A, Glycine
Exitation: Glutamate NMDA, 5HT, Nicotinic
Ketamine site of action:
Decrease glutamate at the NMDA receptor (blocking excitation)
IV anesthetics act primarly on:
Ligand-Gated ion channels
2 categories of neuromuscular blocking agents:
Competitive blocking agents (compete with acetylcholine)
Depolarizing blocking agents (activate the receptor of acetylcholine and DESENSITIZES)
Competitive blocking agents usual end-name:
’‘-ium’’
Succinylcholine is a
Depolarizing blocking agents (derivative of acetylcholine)
Curare is a
Competitive blocking agents
Pseudocholinesterase is a
plasma enzyme that breakdown succinylcholine
Individual with deficite in plasma pseudocholinesterase can lead to
stop breathing and not be able to recover quickly as without the deficite.
Local anesthesic act by
Blocking Voltage-gated Sodium channel.
Adrenaline with local anesthesic alter the pharmacokinetics by creating
an vasoconstriction –> less blood flow to the region –> slow rate of carrying the local anesthesic away from the site of action AND lest plasma cholinesterase to break down –> INCREASE half-life
Local anesthetics structure:
Lipid-soluble section, with ester link and an amine portion.
Local anesthetics are metabolized by
plasma cholinesterase
The delivery of the drug to the patient and subsequently to the brain is directly related to:
its partial pressure.
Factor influencing the rate of induction of anesthesia: (how fast the person will be anesthetized and ready for the surgery)
- Higher the concentration, faster the induction
- Higher/better the alveolar ventilation rate, faster the induction.
- Lower solubility of the agent in the blood, faster the induction.
- Very high cardiac output = less will go to the brain, less the rate of induction.
For most of the situations, we need (xMAC) for a safe amount?
1.3x MAC
Methoxyflurane % metabolized?
50-70%
Why is local anesthesia injected in the spinal fluid had a longer effect?
bc the spinal fluid is lower in cholinesterase. (take more time to get rid of the anesthetic agent)
Eutectic muxture of local anesthesics (EMLA):
mixure of local anesthetics in base form that can be absorbed through the skin. (no need to inject, usefull for kids)
