4/10Exam 3 N. Inhaled (7) Flashcards
Site of action of inhaled anesthetics
multiple sites of action and protein targets probably exist;
When does loss of consciousness ensue?
Once a critical concentration of drug has entered the brain and spinal cord
VA with a chloride ion
Isoflurane
What are The primary factors that influence absorption of the inhalation anesthetics? (VUCSA)
Ventilation,
Uptake into the blood
Cardiac output,
Solubility of the anesthetic drug in the blood, and Alveolar-to-venous blood partial pressure difference.
The concentration or partial pressure of anesthetic in the lungs is assumed to be
the same as in the brain, because the drugs are highly lipid soluble and diffusible, and they quickly and easily reach equilibrium among the highly perfused body compartments.
Dose of an individual drug is expressed in terms of the
minimum alveolar concentration (MAC)
MAC is the
Minimum alveolar concentration needed to produce anesthesia (lack of movement) upon surgical stimulation
The faster the lung (and therefore brain) concentration rises, the_______Anesthesia is achieved
the faster
anesthesia is achieved.
The faster the lung (brain) concentration falls after discontinuation of the drug, _________the patient emerges
the more quickly the patient emerges
What do you do when preparing for a patient who is susceptible to malignant hyperthermia to avoid exposure resulting from residual trace amounts of gases *(TRI) ?
Thorough flush of the anesthesia machine with 100% oxygen at 10 L/min for at least 20minutes
Replacement of breathing circuits and the carbon dioxide canister, and draining, Inactivation or removal of vaporizers are
advised
MAC of Sevoflurane
2
Blood/Gas partition Coefficient of Sevo
0.6
MAC of Isoflurane
1.15
MAC of Nitrous oxide
105
Blood/Gas partition Coefficient of N2O
0.47
Desflurane MAC
5.8
Blood/Gas partition Coefficient of N2O
0.42
Is an indicator of the speed of uptake and elimination
The blood/gas solubility coefficient of an anesthetic
Concentration effect
The higher the concentration of anesthetic delivered, the faster anesthesia is achieved; this is also referred to as over-pressuring; as with any drug, the larger the initial dose administered, the faster the onset of action
Oil/gas Solubility coefficient
The blood/gas solubility coefficient is the indicator of an anesthetic’s speed of onset and emergence:
the higher the coefficient, the slower the anesthetic; conversely, the lower the coefficient, the faster
the anesthetic
Second-gas effect
The second-gas effect is a phenomenon in which two anesthetics of varying onset speeds are administered
together: a high concentration of a fast anesthetic such as nitrous oxide is administered with a slower second anesthetic gas; the slower gas achieves anesthetic levels more quickly than if it had been given alone
Diffusion Hypoxia
Diffusion hypoxia occurs when high concentrations of nitrous oxide are administered; at the end of the procedure, when nitrous oxide is discontinued, it leaves the body very rapidly, causing a transient
dilution of the oxygen and carbon dioxide in the lungs; hypocarbia and hypoxia may occur;
How to prevent diffusion hypoxia?
administration of 100% oxygen for approximately 3-5 min when nitrous oxide is discontinued alleviates this problem
Allow for an increase in deposition of anesthetics into fat and may prolong
recovery
Long procedures and morbid obesity
The MAC or required dose of Anesthetics is
higher in infants and children and decreases with increasing age.
Infants MAC vs adult
Infants aged 6 months have a MAC 1.5 to 1.8 times higher than
a 40-year-old adult.59
Diffusion of Nitrous Oxide into Closed Spaces
Nitrous oxide diffuses into air-containing cavities in the body during an anesthetic procedure.
These air-containing spaces are normally rich in nitrogen, which is_________Soluble than nitrous oxide.
34 times less soluble than nitrous
oxide.
NItrous oxide , If the space is expandable
it increases in volume.
Examples of expandable air cavities, include
Air embolism Pneumothorax Acute intestinal obtruction Intraocular air bubles Pneumoperitoneum
Avoid nitrous during these procedures
tympanomastoid procedures
and intracranial air during diagnostic or surgical intracranial procedures.
Cuff and nitrous
endotracheal tube cuff, laryngeal mask airway, and
balloon-tipped pulmonary artery catheters may expand during nitrous oxide anesthesia, and appropriate precautions and adjustments
should be considered
The uptake of anesthetic drugs is faster in which population?
children than in adults. In other words, a child goes to sleep faster than an adult patient
Child goes to sleep faster than an adult, whY?
Child has higher alveolar ventilation per weight accounts for this effect.
The higher the cardiac output
the slower the onset.
Less soluble anesthetic work
faster
In general, the longer an anesthetic is administered,
the slower the patient emerges.
The least soluble
Exhibits the fastest clinical recovery, Least to fast order
desfluranewith sevoflurane and isoflurane following in that order.
Intraocular hexafluoride gas and N2O
2-18 mmHg increase in pressure in 20 minutes
Middle ear pressure and N2O
Increased 1-7 mmHg in 1 hour
Pneumothorax and Nitrous
2-3 times the volume in 5-20
minutes
Intestinal gas and N2O
Double in 150 minutes
Air Bubble and N2O
Immediate increases in size occur
Least metabolize
nitrous
Least metabolize before nitrous
Desflurane Less than 0.1
Minimum alveolar concentration—BAR definition
block adrenergic responses
(MAC-BAR)The alveolar concentration of anesthetic that blunts the autonomic response to noxious stimuli;
approximately
MAC Bar level
1.6-2.0 MAC
The MAC suppressing appropriate response to commands in
50% of patients; memory is usually lost at MAC-awake; approximately 0.3-0.5 MAC
The MAC suppressing appropriate response to commands in
50% of patients; memory is usually lost at MAC-awake;
MAC awake level is
approximately 0.3-0.5 MAC
Are the least metabolized and do not result in metabolism-related toxicity.
Nitrous oxide, desflurane, and isoflurane
First, the majority of the blood leaving the lungs with anesthetic is normally distributed to the vital organs
Vessel rich group
The longer the anesthetic is given , the
Greater the saturation of all the body compartments.
During induction, increases in cardiac output effect on onset?
slow onset.
Hyperthermia and MAC
Increase
Drug induces increases in CNS and MAC
Increase
Hypernatremia and MAC
Increases
Chronic Alcohol abuse and MAC
Increase
Hypothermia and Increasing age and MAC
Decrease