SEE/NCE Anesthesia IV and Inhaled Anesthetics Flashcards
The presence of a right to left shunt will affect inhalation induction by?
Lower/decrease the arterial partial pressure of the anesthetic
How does the right to left shunt leads to a slower rate of induction?
In a right-to-left shunt, the shunted blood dilutes the blood returning from ventilated alveoli. As a result, the arterial partial pressure of the gas is reduced, and the rate of induction becomes slowed.
This slowing down of induction in a right-to-left shunt will be more pronounced in an agent with
low blood solubility than in an agent with high blood solubility. This is because the uptake of the soluble agent offsets the dilutional effect the shunt produces
Age and Intraoperative bronchospasm relationship
age less than 10 years more at risk
Airway device and bronchospasm relationship
Endotracheal intubation
How does the inhaled anesthetics affect myasthenia gravis?
Skeletal muscle relaxation In patients with myasthenia gravis is more pronounced and enhanced by as much as 40%
Skeletal muscle relaxation is most pronounced when using what kind of volatile anesthetics?
potent volatile anesthetics in excess of 1.0 MAC
Which effect on the respiratory system are you most likely to see with the administration of an inhalation anesthetic?
Respiratory depression due primarily to a decrease in TIDAL VOLUME
With volatile anesthetics, how is minute ventilation affected ?
The tidal volume is primarily affected, followed by the respiratory rate.
Vt and volatile anesthetic relationship
Inverse proportional relationship –> The tidal volume is decreased as the concentration of the agent increases
What happens to the RR ? Does CO2 increase?
The respiratory rate increases, but this is typically insufficient to prevent increases in arterial CO2 due to hypoventilation
2 potential byproducts of sevoflurane administration are
Compound A
Fluoride
Compound A and sevoflurane has been associated with
Low flow anesthesia
How to remember number of fluoride between DES, SEVO and ISO
5-6-7 I-D-S 5- Isoflurane 6- Desflurane 7- Sevoflurane
The composition of the inspired gas mixture a patient receives depends primarily upon what 3 things? .
Fresh gas Flow rate
Absorption by the circuit
Volume of the breathing circuit
The best way inspired gas concentration will be closer to the fresh gas concentration
- if the circuit volume and level of absorption by the circuit are low
- the fresh gas flow is high.
A patient with a right-to-left shunt is about to undergo induction of general anesthesia. You expect that the speed of induction will be _____ and this effect would be greatest with _____.
Slower;
Greatest with the low blood/gas solubility agent like nitrous / desflurane
What is the vapor pressure of Desflurane?
660 mmHg
What is the vapor pressure of Isoflurane?
240 mmHg
How does nitrous oxide affect PVR (Pulmonary vascular resistance)
Nitrous increases PVR
You are anesthetizing a patient with a congenital heart disease and a right-to-left shunt. The use of nitrous oxide could
increase the shunt due to an increase in PVR
MAC is related to the
oil:gas solubility coefficient of an anesthetic agent.
One way to estimate the approximate MAC of an agent is to
divide 150 by the oil:gas coefficient. In this case, 150 divided by 100 would equal an estimated MAC of 1.5%.
Overpressuring during an inhalation induction is acceptable with sevoflurane because it
less pungent and less likely to produce airway irritation.
What is the definition of Overpressuring?
Overpressuring is the use of higher inspired concentrations of an inhaled anesthetic than the desired endpoint to achieve a faster induction speed. Overpressuring is acceptable with sevoflurane
Under normal conditions, the mechanism of autoregulation maintains constant cerebral blood flow over a range of mean arterial pressures from _____ to _____ mm Hg.
60-140 mmHg. (nagelhout)
As MAP decreases within the autoregulation range (60-140mmHg) what happens to cerebral vessels?
the cerebral vessels dilate to keep CBF constant.
Modern volatile anesthetics decrease the blood pressure primarily by their effect on
systemic vascular resistance
How are cortical somatosensory evoked potentials affected by the administration of volatile anesthetics?
DAIL
Decrease Amplitude
Increase Latency
Which is more pronounce with the effect of volatile anethestics on SSEPs : The decrease in amplitude or the increase in latency?
The decrease in amplitude is more pronounced than the increase in latency.
Vessel rich group receive _____% of CO?
75
Desflurane boils at ______
22.8 C which is slightly above normal room temperature.
When a volatile agent is administered, there is an initial _______in amplitude followed by a _____ in both amplitude and frequency.
increase ; decrease
At what MAC does EEG exhibit electrical silence; What is it referred to as?
At about 2.0 MAC, the EEG may temporarily exhibit electrical silence. This is referred to as burst suppression.
The concentration of inhaled anesthetic that prevents an adrenergic response to skin incision is referred to as
MAC-BAR
Adrenergic response to skin incision are
increased heart rate, blood pressure, plasma norepinephrine levels
What is the dose of volatile anesthetic that prevents the adrenergic response in 50% of patients?
MAC-BAR50
What is the dose that prevents an adrenergic response in 95% of patients.
MAC-BAR95
The blood/gas partition coefficient of isoflurane is
1.43 (some source say 1.46).
Where do anesthetics act to inhibit motor responses to noxious stimuli?
act on the spinal cord to inhibit motor responses to painful stimuli.
At 760 mmHg, the boiling point of Sevoflurane in degrees Celsius is:
58.5
Boiling point mnemonic from high to low for Desflurane, Isoflurane, Halothane, Enflurane, and Sevoflurane
HL -> SE-HID
Boiling point for Desflurane, Isoflurane, Halothane, Enflurane, and Sevoflurane
- 8 C
- 5 C
- 2 C
- 5 C
- C
Volatile anesthetics are eliminated from the body primarily by the
Alveoli (lungs)
Metabolic acidosis on MAC acute ethanol intoxication, anemia, lidocaine administration, and decreased central neurotransmitter levels may decrease MAC levels.
Decrease
Hypoxia on MAC
Decrease
Hyperthermia on MAC
Increase
Lidocaine administration on MAC
Decrease
Decreased central neurotransmitter levels on MAC levels
decrease MAC levels .
Na+ leves and osmolarity and effect on MAC
hyponatremia, hypo-osmolality, pregnancy
Acute Ethanol on MAC
Decrease MAC
Anemia on MAC
Decrease MAC
Which of the following agents is most likely to increase the systemic vascular resistance? Amount VA and nitrous
Nitrous oxide
All modern volatile anesthetics decrease the blood pressure in a dose-dependent fashion by decreasing
vascular resistance.
All modern volatile anesthetics decrease the blood pressure in a dose-dependent fashion by decreasing vascular resistance. Nitrous oxide, however,
increases the SVR by activating the sympathetic nervous system.
You are preparing to induce general anesthesia with a volatile anesthetic in a patient with a LEFT - to - RIGHT shunt. You know that this condition would
produce a higher partial pressure of anesthetic returning to the lungs
In a left-to-right shunt, the blood delivered to the lungs has a______(high or low) partial pressure of anesthetic than the blood that has passed through the tissues.
higher partial pressure
Left-to-right shunt vs right-to-left shunt>? will offset the dilutional effect of a right-to-left shunt.
a left-to-right shunt will offset the dilutional effect of a right-to-left shunt.
In fact, the effect of a left-to-right shunt on the speed of induction is only detectable if
a right-to-left shunt is already present.
Ventricular septal defect (as may occur with tetralogy of Fallot) produces a _______ shunt.
right-to-left
Mnemonic to remember effects of right-to-left shunt OR left-to-right shunt on volatile anesthetic partial pressure
RLL (right left low)
LRH (left right High)
Which agent has the lowest blood:gas partition coefficient?
Xenon
Blood:gas partition coefficient of nitrous is
0.46
Blood:gas partition coefficient of desflurane is
0.42
Blood gas partition coefficient measured at which temperature
37C
Blood:gas partition coefficient of Isoflurane is
1.4
Blood:gas partition coefficient of Sevo is
0.6
Blood:gas partition coefficient of Volatile anesthetics : HIGH to LOW - mnemonic
Blood/GAS - I See No D*ck
Iso sevo nitrous des
Blood:gas partition coefficient of Volatile anesthetics : HIGH to LOW - Numbers
- 4
- 6
- 47
- 42
Oil:gas partition coefficient of Volatile anesthetics :HIGH to LOW - mnemonic
Oh GOD - I See De Nis Isoflurane Sevoflurane Desfluane Nitrous
Oil:gas partition coefficient of Volatile anesthetics :HIGH to LOW - numbers
99
50
18.7
1.4
Simultaneous administration of a relatively slow agent such as isoflurane and a faster drug such as nitrous oxide (in high concentrations) to speed the onset of the slower agent is referred to as
the second-gas effect
One of the most significant concerns with the use of nitrous oxide is its ability to
to expand an air-filled space.
Expansion of nitrous with air-filled space can occur in any closed
space that contains air including the bowel, an air embolus, or even the balloon in an endotracheal tube cuff.
Nitrous oxide is contraindicated during tympanoplasty because the
pressure can build up to the point that it dislodges the graft.
Despite having a lower blood:gas solubility coefficient, the rate of rise of the FA/Fi ratio is higher for nitrous oxide than for desflurane. This is due primarily to the
concentration effect
Agents with a lower blood:gas partition coefficient exhibit a _______ (faster/slower)rate of rise in the FA/Fi ratio.
faster
Agents with a lower blood:gas partition coefficient exhibit a faster rate of rise in the FA/Fi ratio. What is one exception? and why?
The exception is that nitrous oxide will exhibit a faster rate of rise than desflurane despite the fact that it has a blood:gas partition coefficient of 0.47 and desflurane has a blood:gas partition coefficient of 0.42.The increase with nitrous oxide is due to the fact that it is administered in doses of 50-70% compared to 3-9% for desflurane. This is referred to as the concentration effect.
Which term describes the administration of a higher partial pressure of anesthetic than the alveolar concentration actually desired for the patient?
Overpressuring. Done to speed up induction
An increase in cardiac output would slow the onset of which inhalation anesthetic the most?
Isoflurane
The higher the blood:gas partition coefficient is, the more the onset will be______ (faster/slower) by an increase in cardiac output.
slowed
The partition coefficient describes the concentration ratio of a gas at equilibrium between two locations. In this example, a blood:gas partition coefficient of 0.5 means that the blood contains
half the concentration present in the alveolar gas when equilibrium is reached.
Volatile anesthetics can produce dilation of healthy coronary vessels. When diseased vessels are not able to dilate, the risk for ischemia increases as
more blood is shunted away from the diseased vessel.
Volatile anesthetics can produce dilation of healthy coronary vessels. When diseased vessels are not able to dilate, the risk for ischemia increases as more blood is shunted away from the diseased vessel. This is known as
coronary steal
Coronary steal results in the diversion of blood flow from ___________ to _______ I
from under-perfused, ischemic myocardial areas to areas with adequate perfusion.
Coronary Steal is also known as the reverse Robin Hood effect, meaning that
oxygenated blood is diverted from the poorly-perfused areas toward the areas that already have excess flow.
The three factors that affect anesthetic gas uptake are the:
BAD
Blood:gas solubility of the gas
Alveolar blood flow
Difference in partial pressure between alveolar gas and venous blood.
Does not affect rate at which the alveolar concentration of an inhaled anesthetic approaches the inspired concentration of the anesthetic
Oil:gas partition coefficient