56 Questions
When a patient wakens prematurely from inhalant anesthesia administered from a modern agent specific vaporizer which of the following will increase delivery of inhalant anesthetic to the alveoli and return the patient to a stable plane of anesthesia?
Increasing patient alveolar ventilation and increasing vaporizer output
An abstract of a manuscript reads “The respiratory effects of identical doses of xylazine in two groups of horses, one anesthetized with 1.0 MAC of Isoflurane and the other anesthetized with 1.0 MAC of Desflurane, was compared”. From reading this section of the manuscript you immediately know that…
Both groups of horses were at the same anesthetic depth of Des and Iso during the study
Given the following table of Inhalant anesthetic properties Cyclouranium --> MAC 8.5, Blood:Gas PC 6.0, Vapor press 21mmHg Diethylpropane --> MAC 9.0, Blood:Gas PC 4.5, Vapor press 255mmHg Inanethane --> MAC 2.0, Blood:Gas PC 0.5, Vapor press 250mmHg Isoplutonium --> MAC 1.2, Blood:Gas PC 14.0, Vapor press 126mmHg Methoxyxenon --> MAC 3.0, Blood:Gas PC 2.4, Vapor press 925mmHg
Which of the inhalant anesthetics listed is the LEAST potent?
Diethylpropane
Given the following: Cyclouranium --> MAC 8.5, Blood:Gas PC 6.0, Vapor press 21mmHg Diethylpropane --> MAC 9.0, Blood:Gas PC 4.5, Vapor press 255mmHg Inanethane --> MAC 2.0, Blood:Gas PC 0.5, Vapor press 250mmHg Isoplutonium --> MAC 1.2, Blood:Gas PC 14.0, Vapor press 126mmHg Methoxyxenon --> MAC 3.0, Blood:Gas PC 2.4, Vapor press 925mmHg
What vaporizer setting would likely be necessary to provide surgical anesthesia to a population of 100 collared peccaries administered no other drugs and using only Inanethane delivered from an Inanethane-specific vaporizer?
3.0%
Cyclouranium --> MAC 8.5, Blood:Gas PC 6.0, Vapor press 21mmHg Diethylpropane --> MAC 9.0, Blood:Gas PC 4.5, Vapor press 255mmHg Inanethane --> MAC 2.0, Blood:Gas PC 0.5, Vapor press 250mmHg Isoplutonium --> MAC 1.2, Blood:Gas PC 14.0, Vapor press 126mmHg Methoxyxenon --> MAC 3.0, Blood:Gas PC 2.4, Vapor press 925mmHg
Which of the following is true?
Diethylpropane is more soluble than Inanethane
During recovery what causes inhalant anesthetics to move from the blood into the alveoli once the anesthetic vaporizer is turned off?
partial pressure gradient
Recovery from inhalant anesthesia occurs when….
Alveolar partial pressure of anesthetic is lower than blood partial pressure
During the maintenance phase of inhalant anesthesia the partial pressure of anesthetic in the alveoli is equal to the partial pressure of anesthetic in the blood. Because of this during the maintenance phase…
No net movement of anesthetic will occur between the alveoli and blood
Cyclouranium --> MAC 8.5, Blood:Gas PC 6.0, Vapor press 21mmHg Diethylpropane --> MAC 9.0, Blood:Gas PC 4.5, Vapor press 255mmHg Inanethane --> MAC 2.0, Blood:Gas PC 0.5, Vapor press 250mmHg Isoplutonium --> MAC 1.2, Blood:Gas PC 14.0, Vapor press 126mmHg Methoxyxenon --> MAC 3.0, Blood:Gas PC 2.4, Vapor press 925mmHg
Which anesthetic has the HIGHEST solubility in blood?
Isoplutonium
Which of the following circuits allow the anesthesia provider to change inspired concentration of inhalant anesthetics most rapidly?
Nonrebreathing (Mapleson) circuits
All other factors remaining equal a patient having a cardiac output of 1 L/min will change depth of anesthesia in response to a change in inspired concentration __________ compared with an identical patient having a cardiac output of 4 L/min.
4 times as fast
During which phase of inhalant anesthesia is the brain PP of anesthetic higher than the alveolar PP of anesthetic?
recovery
Cyclouranium --> MAC 8.5, Blood:Gas PC 6.0, Vapor press 21mmHg Diethylpropane --> MAC 9.0, Blood:Gas PC 4.5, Vapor press 255mmHg Inanethane --> MAC 2.0, Blood:Gas PC 0.5, Vapor press 250mmHg Isoplutonium --> MAC 1.2, Blood:Gas PC 14.0, Vapor press 126mmHg Methoxyxenon --> MAC 3.0, Blood:Gas PC 2.4, Vapor press 925mmHg
Based solely upon the information in the table above which of the inhalant anesthetics would result in the fastest induction of anesthesia, fastest recovery from anesthesia and fastest changes in anesthetic depth in response to a 1.0 MAC change in inspired concentration?
inanethane
During the induction phase of inhalant anesthesia which of the following will increase transfer of inhalant anesthetic from the breathing circuit to the alveoli?
Increased alveolar ventilation
Assuming solubility is the only consideration, which of the following is true if an inhalant anesthetic has a high solubility in blood?
Patients will recover slowly once administration is discontinued
Because the drug is MAC sparing you would expect that preanesthetic administration of the opioid drug methadone would allow you to use _______ vaporizer settings of sevoflurane compared to a patient who had not been premedicated.
lower
Which of the following is true concerning the Vapor Pressure value of an inhalant anesthetic?
The Vapor Pressure value is a measure of anesthetic solubility
What is the partial pressure of sevoflurane administered from a precision sevoflurane vaporizer located at a veterinary clinic in Tucson (Elevation = 2,300 ft, PATM = 700 mm Hg) when the vaporizer is set to 2%?
14mmHg
An anesthetized dogs’ lung at sea level (760 mm hg) contains the following mixture of gases: Oxygen 90%, Isoflurane 2%, Carbon Dioxide 4% and Water Vapor 4%. What is the sum of the partial pressure of all gases within the lung?
760 mmHg
An athletic patient having a resting cardiac output that is 3x higher than normal would be expected to induce into isoflurane anesthesia _______ rapidly compared to an identical patient having a normal cardiac output.
less
Significant differences between isoflurane and sevoflurane include…
blood solubility
The toxin Compound A is produced when which of the following inhalant anesthetics is administered in rebreathing circuits that use soda lime and low fresh gas flow rates?
sevoflurane
Which of the following is false concerning the gaseous anesthetic N2O?
N2O has a lower MAC value compared with Isoflurane
Which of the following is false concerning the inhalant anesthetics?
In general, inhalant anesthetics are potent analgesics
Which of the following is true concerning administration of epidural opioids to canine patients?
Epidural administration of hydrophilic opioids such as morphine is associated with a long (12-24 hr) duration of action
IV administration of which of the following opioids is frequently associated with histamine release and resultant hypotension?
Morphine
Numerous studies have confirmed that the μ opioid receptor conveys the highest quality of analgesia when compared to other opioid receptors. Based upon this information which of the following is likely to provide the highest quality of analgesia?
Hydromorphone
Which of the following opioids would be expected to decrease the amount of sedation of a patient that had been administered an infusion of fentanyl?
Butorphanol
Which of the following μ opioids is least likely to result in emesis following preoperative administration to a canine patient?
Methadone
Which of the following is false concerning the inhalant anesthetic Nitrous Oxide (N2O)?
N2O has a low MAC value and therefore high potency
Epidural administration of opioids provide analgesia by binding to opioid receptors that are located…?
in the spinal cord dorsal horn
Which of the following opioids are pure μ receptor agonists and would therefore provide the highest quality of analgesia?
all of the above
Which of the following is a pure opioid antagonist having antagonist activity at the μ, δ and κ opioid receptors?
naloxone
Which of the following is a mixed opioid agonist/antagonist having agonist activity at the κ opioid receptor?
butorphanol
Which of the following is true concerning opioids and the α-2 agonist drugs?
Both opioids and α-2 agonists produce sedation
Which of the following is true concerning epidural administration of opioids in dogs?
Hydrophilic opioids such as hydromorphone have a 12-24 hour duration of action
A dog under a light plane of sevoflurane anesthesia is observed to have a profound decrease in mean arterial pressure following the administration of Morphine, 0.5 mg/kg as an IV bolus. What is the most likely reason for the decrease in arterial pressure?
histamine release
Which of the following is false concerning epidural administration of opioids in dogs?
The opioid dose for epidural administration is 20% higher than a typical IM dose
Which of the following is true concerning the injectable anesthetic Alfaxan®?
Administration of clinically appropriate dosages is associated with significant CV stability
Which of the following is true concerning the injectable anesthetic Telazol®?
Telazol is supplied as a powder and is reconstituted prior to use
Which of the following would be a poor choice for administration to a canine patient presenting in hypovolemic shock?
Acepromazine
What is the main difference between the available α2 agonist sedatives (xylazine, detomidine, dexmedetomidine and romifidine)?
Specificity for the a2 receptor
All of the following would be an expected effect following administration of atropine or glycopyrrolate except?
Bronchoconstriction
Which of the following is true concerning atropine and glycopyrrolate?
Glycopyrrolate does not cross the placenta
When administered as the sole preanesthetic drug to canine patients, acepromazine….
Has an inhalant MAC sparing effect
The tranquilizer midazolam…..
Is associated with minimal CV depression at clinically used dosages
The graph below depicts HR values from a group of dogs administered a preanesthetic drug. Baseline (pre drug) HR’s are recorded at time 0 and immediately after collecting the HR values the premedication drug was administered IV (arrow). Based upon your knowledge of preanesthetics, which preanesthetic drug was administered?
(chart shows HR dropping immediately after administration)
Xylazine
Which of the following is false concerning the α-2 antagonist drugs?
Vantinoxan is commonly used to antagonize xylazine sedation in cattle
What is primarily responsible for the rapid decline in drug brain concentrations following IV induction using ketamine?
Redistribution from the central compartment to the muscles
You wish to induce anesthesia in a horse using a combination of xylazine and ketamine. After administration of xylazine IV to a horse you must….?
Verify adequate sedation and muscle relaxation before administering a bolus of ketamine IV
Which of the following is a butyrophenone tranquilizer having similar pharmacology to phenothiazine tranquilizers?
Droperidol
The cyclohexamine anesthetic ketamine is always administered in conjunction with an α2 agonist or a benzodiazepine because
Administration of ketamine alone is associated with CNS excitation and poor muscle relaxation
The bradyarrhythmia pictured below is commonly associated with IV administration of which of the following? (VPCs-- p wave with no QRS)
Xylazine
The Alfaxalone anesthetic within Alfaxan® is delivered via the carrier molecule cyclodextran because. . .
Alfaxalone is not water soluble
Which of the following is false concerning the drug propofol?
Propofol’s anesthetic effects are terminated by plasma pseudocholinesterase
Which of the following is the rationale for the inclusion of vantinoxan in the recently released combination drug Zenalpha®?
Vantinoxan inhibits α-2 peripheral vasoconstriction
Study Notes
Inhalant Anesthesia
- When a patient wakes up prematurely from inhalant anesthesia, increasing the delivery of inhalant anesthetic to the alveoli can return them to a stable plane of anesthesia.
- During recovery, the anesthetic vaporizer is turned off, causing the inhalant anesthetic to move from the blood into the alveoli.
Properties of Inhalant Anesthetics
- The potency of an inhalant anesthetic is inversely proportional to its MAC (minimum alveolar concentration) value.
- The LEAST potent inhalant anesthetic is Diethylpropane with a MAC of 9.0.
- Isoplutonium is the most potent inhalant anesthetic with a MAC of 1.2.
Pharmacokinetics of Inhalant Anesthetics
- The rate of induction and recovery from anesthesia is influenced by the solubility of the anesthetic in blood and tissues.
- An anesthetic with high solubility in blood will result in slower induction and recovery.
- Inanethane has a low solubility in blood, making it suitable for rapid induction and recovery.
Vapor Pressure and Vaporizers
- Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid phase.
- Vaporizers deliver a precise concentration of anesthetic vapor.
- The vaporizer setting required for surgical anesthesia depends on the anesthetic's MAC value and the patient's cardiac output.
Anesthesia Circuits and Breathing Systems
- The anesthesia circuit allows the anesthesia provider to change the inspired concentration of inhalant anesthetics rapidly.
- Allowing the patient to breathe in a mixture of oxygen, anesthetic, and air helps to facilitate the uptake of the anesthetic.
Cardiovascular Effects of Inhalant Anesthetics
- Inhalant anesthetics can cause cardiac output to decrease, leading to a slower response to changes in inspired concentration.
- Patients with a higher cardiac output will experience faster changes in anesthetic depth in response to changes in inspired concentration.
Opioids and Analgesia
- Opioids bind to μ, δ, and κ opioid receptors to produce analgesia.
- The μ opioid receptor conveys the highest quality of analgesia.
- Epidural administration of opioids provides analgesia by binding to opioid receptors in the spinal cord.
Other Topics in Anesthesia
- The toxin Compound A is produced when sevoflurane is administered in rebreathing circuits that use soda lime and low fresh gas flow rates.
- N2O is a gaseous anesthetic that can be used as a carrier gas for other anesthetics.
- α2 agonists and benzodiazepines are often used as preanesthetics to reduce anxiety and provide sedation.
- Atropine and glycopyrrolate are anticholinergics used to reduce salivation and bronchial secretions.
Test your knowledge on increasing delivery of inhalant anesthetic to the alveoli and stabilizing the patient's plane of anesthesia when awakening prematurely from modern agent specific vaporizer administration.
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