(2-22-17) General Anesthesia Flashcards
According to Dr. Manton what are the 3 components of being a doctor?
- Legal
- Practical
- Psychological
What are the two principle classes of general anesthesia?
- Intravenous
2. Inhalation
What is historically considered the first anesthetic?
Nitrous Oxide
If a patient inhales normal atmospheric air what percentage of O2 is present?
21%
If a patient inhales normal atmospheric air what percentage of N2 is present?
79%
Why do you Pre-oxygenate a patient?
To ensure that the patients functional residual capacity (about 2.5 L) has the maximum amount of O2 present while you intubate (thus giving you more time in case you don’t get the intubation on the first try).
What are the 4 A’s of General Anesthesia?
- Amnesia
- Analgesia
- Akinesia
- Autonomic and sensory areflexia
Type of General Anesthesia achieved with several agents
Balanced Anesthesia
Type of Local Anesthesia used to anesthetize a body region
Regional Anesthesia
Regional Anesthesia plus “light” General Anesthesia
Combined technique
IV agents for analgesia/ anxiolysis maintaining consciousness
Conscious Sedation
T/F: In terms of anesthesia, we usually use a combined technique or balanced anesthesia
True
What stage of anesthesia occurs without amnesia, impaired judgement, vertigo/ataxia, increased respiration, blood pressure, heart rate
Stage 1 (Stage of Analgesia)
What stage of anesthesia is the patient delirious, excited, amnestic, irregular respirations, struggling, retching and vomiting
Stage 2 (Stage of Excitement)
What stage of anesthesia will the patient experience recurrence of regular respiration–>cessation, loss of corneal, swallowing, eyelid reflexes, skeletal muscle relaxation, and decreased blood pressure
Stage 3 (Stage of Surgical Anesthesia)
What stage of anesthesia begins at cessation of spontaneous respiration–> severe depression of vasomotor and respiratory centre –> and can result in death without support
Stage 4 (Stage of Medullary Depression)
T/F: Nitrous Oxide is the ideal anesthetic drug for all cases
FALSE: No such thing as one ideal anesthetic.
What are the two main ways IV anesthetics act by?
A. Potentiating the action of an inhibitory ionophore (the GABAa receptor)
B. Blocking the action of excitatory ionophores (Nicotinic Ach & NMDA receptors in spinal chord)
What are the advantages and disadvantages of IV anesthetics?
Advantages: Rapid onset, controlled dosage, ease of administration
Disadvantages: Overdose not readily corrected, no antagonists or antidotes, prolonged after effects (hangover).
Dr. Manton used the drug_____ as an example for dissociative anesthetics. This drug can be administered in what ways?
Ketamine;
Intramuscularly or Intravenously
What class of drug is ketamine?
Cyclohexylamine (similar to angel dust or PCP)
How does Ketamine work? What is its main action on the body?
Blocks both nicotinic ACh and NMDA (glutamic acid) receptor channels; main action is cardiovascular stimulation
T/F: Dissociative anesthesia produces catatonia, amnesia, analgesia, and true surgical anesthesia
FALSE: It does not produce true surgical anesthesia
When are cyclohexylamines indicated?
Mainly in outpatient procedures, children, and burn dressings
If a patient is having an adverse (emergence) reaction to ketamine what drug is given to counteract the drug?
Diazepam or Versed
Are Benzodiazepines used mainly preoperatively, during the procedure, or post operatively?
Preoperatively
T/F: Benzodiazepines are primarily used for anxiolytic/ amnestic effects
True
What is the specific antagonist for benzodiazepines?
Flumazenil
Which of the following serves as the main analgesic agents intravenously? A. Barbiturates B. Benzodiazepines C. Opioids D. Dissociative Anesthetics
C. Opioids
T/F: Opioids do little to affect the CV system (CV stability) and have dose dependent respiratory depression
True
Propofol is what type of drug?
Alkylphenol
Why are alkyl phenols contraindicated for sedation in children?
Possible acidosis and neurological sequelae
What class of drug discussed by Dr. Manton produces a significant but transient fall in blood pressure and a rise in heart rate?
Alkylphenols (propofol)
Is ALPHA half-life synonymous with the redistribution half life or the excretion half life?
Redistribution
Is BETA half-life synonymous with the redistribution half life or the excretion half life?
Excretion
The most popular ambulatory surgery induction agent with the least residual sedation is….
Propofol
An ULTRA SHORT ACTING, class of drugs that induces anesthesia (hypnosis) in 1 circulation time and is very lipid soluble
Barbiturates
Barbiturates redistribution occurs at a rate proportional to blood supply. Rank the following structures in the order of Barbiturates action: Lean tissues, Fat, Brain.
Brain–> Lean tissues–> Fat
When using barbiturates, induction can be accompanied by laryngospasm, coughing, or sneezing. What drug do you give to prevent these?
Atropine or SCOPOLAMINE
Barbiturate solutions are very Alkaline or Acidic?
ALKALINE
T/F: Barbiturates cause a marked respiratory depression, and mechanical ventilation should be available.
TRUE
This class of analgesics are used mainly for induction and short duration procedures with Minimal cardiovascular or respiratory effects.
Imidazole’s (Etomidate)
T/F: Imidazoles have a rapid onset (seconds) and analgesia making it perfectly suited for some surgeries
FALSE: They do have a rapid onset, however they do not produce Analgesia (the patients reflexes are present).
What percentage of people experience pain on injection with Imidazoles?
30%
A single dose of Imidazoles causes what?
Inhibitory effects of steroidgenesis- adrenocortical suppression
How are inhalation anesthetics administered?
Via facemask or endotracheal tube
When two gases of different solubility exist together in the alveolus, the more soluble dissolves in the plasma first, leaving the less soluble as a bigger fraction of alveolar gas, thus allowing it to dissolve more rapidly than would otherwise be the case. This phenomenon is termed what?
Second Gas Effect
The steady state minimum alveolar concentration (percent) of an inhalation agent that is required for immobility of 50% of the subjects exposed to a noxious stimulus (e.g., surgical incision)
Minimum Alveolar Concentration (MAC)
1 MAC of Sevo is what percentage?
about 2%
Pharmacokinetically, inhalation anesthetics achieve increased effect as the steady state concentration increases in what bodily structure?
Brain
A low Blood: Gas coefficient @ 37 C (i.e. 0.47 :1) means what?
The drug is not very soluble in blood (i.e. has a higher affinity for air) and will thus be cleared quicker after cessation of administration.
Which of the following anesthetics has a HIGHER Blood:Gas Coefficient?
Nitrous Oxide or Sevoflurane
Sevoflurane
Which of the following anesthetics has a HIGHER Blood:Gas Coefficient?
Halothane or Sevoflurane
Halothane
Which of the following anesthetics has a HIGHER Blood:Gas Coefficient?
Halothane or Nitrous Oxide?
Halothane
Why do anesthesiologist use several multiples of the MAC value for an agent initially?
To increase the rate of induction (i.e. cause a more rapid onset) of the anesthetic, more rapidly achieving an adequate brain level of the agent to produce the desired affect
The rate of rise of anesthetic in the blood is also determined by the minute ventilation of the patient. What is the formula for the minute ventilation?
MV=TV x RR
Minute ventilation= Tidal Volume x Respiratory Rate
Increasing ventilation will generally _______ (increase/decrease) the speed of induction
INCREASE
T/F: The smaller the partial pressure gradient between arterial and venous blood, the less time it takes to achieve equilibrium (i.e. the faster the anesthetic works)
TRUE
Patients with low cardiac output would have a relatively _______ (quick/ slow) induction
QUICK; due to decreased pulmonary blood flow, the rate of rise of the arterial anesthetic gas tension would increase
The major route of elimination for inhalation anesthetics occur through which organ? Inhalation agents with ____ (low/high) solubility are eliminated quickly.
Lungs; low
What are the risks associated with Halothane?
- Malignant Hyperthermia
- 20% metabolism “toxic” products causing hepatic damage with repeated exposure
- Risk of spontaneous abortion in pregnant OR staff
An isomer of enflurane
Isoflurane
T/F: Isoflurane causes some CV or respiratory depression and upon induction BP will decrease, but the stimulation of surgery restores it.
TRUE
After giving Isoflurane, how is cardiac output maintained?
Increase in HR
T/F: Isoflurane contains a halogenated ether and #1 used inhalation anesthetic in U.S.
True
This inhalation anesthetic has a risk of malignant hyperpyrexia.
Isoflurane
This inhalation anesthetic is the least blood soluble (most rapid induction) and has virtually no metabolism (no liver toxicity, but is still a respiratory depressant).
Desflurane
When is Desflurane contraindicated as the sole anesthetic agent?
In cases of coronary artery disease (CAD) or where rise in heart rate or blood pressure is undesirable
What risks are associated with Desflurane?
Malignant hyperthermia, severe laryngospasm, secretion, apnea
This inhalation anesthetic has no respiratory tract irritation, poor solubility, and few real problems (however, should be used in closed circulatory systems at low gas delivery rates (due to formation of toxic Compound A with soda lime))
Sevoflurane
This inhalation anesthetic is commonly used but least potent. Really used as an analgesic attaining only stage 1, or as an adjuvant for the second gas effect. Also has a high risk of abuse in anesthetists, dentists, and nurses
Nitrous Oxide (Laughing gas)
