General Anesthetics Flashcards
What does a complete anesthetic produce?
Unconsciousness Unresponsiveness Amnesia Immobility Autonomic stability to the anesthetic state
Why isn’t Diethyl Ether used as a general anesthetic?
It is highly flammable
How do modern general anesthetics achieve the best qualities?
They’re given as a combination to get the advantages of all the drugs
What are the aspects of Ideal Surgical Anesthetics
Smooth and rapid induction
Produce unconsciousness
Produce amnesia
Maintain essential physiological functions, while blocking undesired reflexes
Skeletal muscle relaxation, but not respiratory muscles
Smooth, rapid, and uneventful recovery with no lasting adverse effects
What types of drugs would be in a anesthetic cocktail?
Antimuscarinics Various analgesics Nitrous oxide and/or opioids Antinicotinics Antiemetics Additional drugs
What role do antimuscarinics play in anesthetic cocktails?
Minimize salivation, larygospasms, and reflex bradycardia
What role do analgesics play in anesthetic cocktails?
Proprioceptive pain relief
Sedation
Amnesia
What role do Nitrous oxide and opioids play in anesthetic cocktails?
Reduce anesthetic requirement, provide analgesia
What role do antinicotinixs play in anesthetic cocktails?
Paralyze skeletal muscle
What role do “additional drugs” play in anesthetic cocktails?
Maintain organ stability
Why are general anesthetics not typically used in dental treatment?
Dental procedures are not usually as traumatic, so its not necessary or desirable to render the patient unconscious
Membrane Lipid Based Theory
The direct action of anesthetics on proteins lead to alterations
aka: Anesthetics interact with hydrophobic sites on proteins and affect their function
What sort of proteins are the likely targets of general anesthetics?
GABA receptors
Ligand activated ion receptors
CNS proteins
They interfere with the function of many proteins of neurochemical interest, but there is not a single target
T/F - Anesthetics have been observed to have both pre and postsynaptic effects
True
What is the reticular formation important for?
Major center supporting consciousness and alertness
Anesthetics that effect the reticular formation do what?
By depressing the RF, they induce unconsciousness
Anesthetics that effect the thalamocortical loop does what?
Induce unconsciousness
What is the limbic system involved in?
Memory
Inhibition of the limbic system would induce what?
Anesthetic-induced amnesia
Anesthetics that affect the spinal cord will do what?
Disrupt pain pathways
T/F - Anesthetics only need to depress one brain pathway to achieve anesthesia?
False - they need to depress many brain pathways
What are the stages of general anesthesia?
1) Analgesia (induction)
2) Excitement
3) Surgical anesthesia
4) Medullary paralysis
T/F - Modern anesthetic try to skip the steps of general anesthesia by being given in a cocktail
True
What is the pathway of distribution of volatile anesthetics?
Alveoli –> Blood –> Briain
What is the pathway of recovery of volatile anesthetics?
Brain –> Blood –> Alveoli
What does a low blood:gas coefficient mean?
Anesthesia has low solubility (prefers the gas stage)
Faster induction and recovery
Ex: nitrous oxide
What does a high blood:gas coefficient mean?
Anesthesia has a high solubility
Slower induction and recovery
exL Halothane
What determines MAC %?
Olive oil solubility
Drugs with a low MAC% have what?
High potency
What are desirable properties for inhalation anesthetics?
Low MAC
Low blood:gas coefficient
What are generalized pharmacological effects of volatile anesthetics?
Decrease the activity of cardiovascular system, respiration, kidney, skeletal muscle, and liver
Nitrous oxide
Volatile Anesthetic with low blood:gas coefficient, and high MAC
Used at concentrations of 20-50% (mostly as an anti-anxiety)
Used in conjunciton with other more potent anesthetics so the other drugs can achieve more rapid onset and recovery
Isoflurane
Improvement of halothane (less toxic, but less potent - lower B:G coefficient)
MAC = 1.15%
B:G = 1.4
Smells bad, so we want to knock the patient out with something else first
Desflurane
MAC = 6%
B:G = 0.45
Contraindicated in patients susceptible to malignant hyperthermia
Seroflurane
MAC = 2%
B:G = 0.65
More rapid acting that isoflurane
Barbituates
IV anesthetics that act as CNS depressants by potentiating the activity of GABA receptors
How do GABA receptors work?
When activated, release Cl in the cytoplasm to cause hyperpolarization, thus providing inhibitory influence on synaptic transmission
How are Barbituates classified?
Based on the duration of action
Classification of Barbituates
Ultra-short acting (15-30 min) Short acting (2-4 hrs) Intermediate acting (4-6 hrs) Long acting (6-8 hrs)
What are the advantages of IV agents in anesthesia?
Rapid distribution (from vein to brain in seconds)
Reduced cardiac depression
No risk of malignant hyothermia
Eliminate the risk of occupational exposure (only patient gets it)
What is the major adverse effect of IV anesthetics?
Respiratory depression
Thiopental
Ultra short acting barbituate Causes unconsciousness in 0.5-1 min 60% of dose reaches brain in 1 minute Consciousness returns in 5-10 minutes Largely has been replaced by Propofol
Methoxhexital
Similar to thiopental, but 2.5x more potent, faster acting, and a shorter duration
Sleep time is 5-7 minutes
Cleared 3x faster than thiopental
Faster recovery, and more favorable for dentistry
Propofol
Most popular barbituate
Rapid recovery and clearing
General state is normal after clearing
What is the induction dose for Propofol?
2-2.5 mg/kg
What is the maintenance dose for Propofol?
50 ug/kg/min - 200 ug/kg/min
Ketamine
Produces dissociation anesthesia
Analgesia and amnesia with minimal effect on respiratory function
Patient can blink and swallow, but doesn’t process info (PCP-like drug)
