Anesthesia (Strauss) Flashcards
What is the benefit of inhalation anesthesia over IV drugs?
Easier to use and titrate patient
What is the term for the use of a gaseous agent to achieve anesthesia from sedation to general anesthesia?
Inhalation anesthesia
Inhalational anesthesia is generally used for general anesthesia, except for which inhalant?
NO (Nitrous oxide?)
What is the state of current inhalational drugs?
Volatile liquids, not gases, that are non-flammable and non-explosive
All current inhalant drugs work on what system?
Reticular activating system
What is an instrument that adjusts flow to match output of the inhalant, accounts for temperature, and is specific to the agent?
Vaporizer
What are 4 methods to administer inhalants?
- Nasal Hood
- Full face mask
- LMA (laryngeal mask anesthetic)
- Endotracheal intubation
What is the method to administer inhalant indicated for oral procedures?
Nasal hood
What is the method to administer inhalant indicated for short procedures outside the face?
Full face mask
What are 2 methods to administer inhalant indicated for longer procedures?
- Laryngeal Mask anesthetic (LMA)
2. Endotracheal intubation
What are the 3 levels of respiration for the patient when on inhalational anesthesia?
- Spontaneously
- Assisted
- Controlled
What is the level of respiration for ambulatory procedure using inhalational anesthesia?
Spontaneous respiration
Why would a patient on an inhalational require aide with respiration?
Because all inhalationals are respiratory depressants (they also slow the heart rate a bit)
Therapeutic ratio is the difference between the therapeutic effect and toxicity, a lower ratio means what?
The lower the ration, the more dangerous the drug
Which part of respiration is active: inhalation or exhalation?
Inhalation
What is the reason for a patient needing assisted ventilation when on inhalational anesthesia?
Decreased tidal volume and rate
A nasal hood is easy to use and allows oral access, but what are its disadvantages?
- No positive pressure available
- No airway protection
- Difficult to control how much patient gets
A full face mask allows for a good seal, positive pressure ventilation, and 100% gas intake with no mixing, but what are the disadvantages?
No airway protection, no mouth access
What are some advantages of inhalational anesthesia?
- Easy to use
- Easily controllable/titratable
- Predictable effects
- Low toxicity
- Rapid effect
- Continuous dosing so very stable
- Can always add IV drug as needed
A full face mask is good for what part of the procedure?
Induction or non-oral procedures
What instrument gives partial airway protection, is easier to place in a difficult airway, and allows for better airway maintenance?
Laryngeal mask anesthetic (LMA)
All airway tubes have what at the connector end?
Universal 15mm connector at the end
On what does the LMA sit when placed?
On vocal cords, note: only offers partial (not 100%)airway protection
Why does air go into the lungs if you place a small amount of positive pressure onto the patient?
The trachea is the path of least resistance
An endotracheal tube has what at the end?
A small balloon
Where does an endotracheal tube sit when placed?
In trachea right above main bronchi
When passing endotracheal tubes between the vocal cords, if go to far, which lung will the tube go into and why?
Into right lung because it is the straighter bronchus
What gives the 100% seal for endotracheal tubes?
Inflation of the balloon end
Yellow indicates what gas?
Air
Green indicates what gas?
Oxygen
Blue indicates what gas?
Nitrous oxide
Is the anesthesia machine a closed or open system?
Closed, so it has a CO2 scavenger (Soda Lime)
What are 4 things that must be considered for inhalation anesthesia?
- Equilibration
- MAC
- Blood gas solubility
- Stages of anesthesia
The partial pressure of all gases will try to do what throughout the body?
Equilibrate (in alveoli, blood, body tissue)
Do all body tissues equilibrate to gases at the same rate?
No
The movement of gases in the body is determined by what?
Equilibration
Which tissues equilibrate quickly?
VRG (vessel rich group) = brain, heart, kidney, gut
What tissue is intermediate in its equilibration time?
VIG (vessel intermediate group) = muscle
What is the concentration of an anesthetic at which 50% of patients will not respond to a noxious stimulus (considered a measure of potency and is used to guide the correct dosages of agents)?
Minimum alveolar concentration (MAC)
Induction usually occurs at how many MAC?
2-3 MAC
Maintenance after induction usually takes place at how many MAC?
0.5-1.5 MAC
Are MACs independent or cumulative?
Cumulative, must consider other drugs used on the patient when considering MAC for a certain drug
When determining the stages of anesthesia, what must always be considered?
The drugs that mask/mimic signs, e.g. atropinecauses pupil dilation
Guedel’s stages of anesthesia based on what?
Ether
What are the 4 stages of anesthesia?
- Analgesia
- Excitement
- Surgical Anesthesia
- Apnea
What are the characteristics of a Stage 1 anesthesia patient?
They are conscious but do not feel pain
Stage 2 of anesthesia begins when and why?
Starts at loss of consciousness as patient begins to lose protective reflexes. Jerking caused by inhibition of
inhibitory CNS.
At what anesthesia stage is surgery performed?
Stage 3 surgical anesthesia
Do current inhalationals induce Apnea (Stage IV anesthesia)?
No
What is the coefficient that represents the ability of an agent to dissolve in blood?
Blood gas solubility
Only blood that (pick one) is or is not dissolved in blood can see the brain to produce effects?
Only NOT dissolved
What Blood Gas solubility / Blood Gas coefficient (BGC) is desired?
Lower the BGC, the faster the rise in arterial gas tension
What does a low BGC mean for both onset and recovery?
Both onset and recovery will be fast
Nitrous has a high or low BGC?
Low, starts within a few breaths and gone within 5 minutes on 100% oxygen
What are 5 minor inhalational agents?
- Ethyl chloride
- Chloroform
- Diethyl ether
- Methoxyflurane
- Nitrous oxide
What are 5 major inhalational agents?
- Halothane
- Enflurane
- Isoflurane
- Desflurane
- Sevoflurane
Of the 5 major inhalationals, which has liver toxicity and epinephrine sensitivity?
Halothane
Of the 5 major inhalationals, which can have seizure activity?
Enflurane
Of the 5 major inhalationals, which has the lowest BGC [0.42], so is very fast in/fast out, but is expensive?
Desflurane
What is the MAC of desflurane?
6
What are the cardiac actions of desflurane?
Tachycardia, but no change in cardiac output
With regards to the breathing associated with desflurane, what is increased?
The breathing is fast and shallow breathing
The PaCO2 increases
All inhalants cause some type of what?
Ionotropism
Most inhalants do what to heart stroke volume, and how does the body compensate?
- Decrease stroke volume
2. Compensate with tachycardia to maintain cardiac output
What is the concern with tachycardia and the heart (think when the heart gets fed)?
Heart gets fed during diastole. Diastole decreases in tachycardia, so heart is fed less.
In what patients is tachycardia a concern and why?
Cardiac patients and elderly. They have less cardiac reserve to compensate for less heart “feeding”during tachycardia.
All inhalationals do what to tidal volume: increase or decrease?
Increase Tidal volume
If all inhalationals increase tidal volume, why does the patient’s PaCO2 increase?
Because they cause tachypnea
What is the MAC of Isoflurane?
1.2 (potent)
Can induction be done with Isoflurane or Desflurane and why?
No, both are pungent and patient will hold breath
What are the cardiac effects of isoflurane?
Isoflurane has minimal cardiac effect, increases the HR by 10%
What are 2 positive characteristics of Isoflurane with respect to airway?
- Good bronchodilator
2. Good muscle relaxation
Isoflurane, being a good bronchodilator, would be indicated in what type of patient?
Asthmatic
What is a consideration as dentists for Isoflurane being a good muscle relaxer?
Makes the mouth easier to open when the patient asleep
What is the most common inhalational, besides N2O, used by our OMFS, with a low blood gas solubility (quick in, quick out)?
Sevoflurane
Because Sevoflurane has very little irritation, what can it be used for?
Used for induction (breath the patient down)
What is the MAC of Sevoflurane?
1.71
What are the cardiac effects of Sevoflurane?
Decreases both tidal volume and rate
Sevoflurane is a triggering agent for this which hasa high fatality that can only be diagnosed by a family history or muscle biopsy. Occurs when every muscle in body starts moving, producing CO2, and generating heat increasing the overall body temperature?
Malignant hyperthermia
High flow rate of Sevoflurane is required to prevent what?
Compound A toxicity (compound A is degradation product of Sevo, shown to cause renal necrosis in rats