Inhalation Anesthesia: Uptake and Distribution

Anesthesia, Chapters 6 & 7

1. Discuss factors involved in delivering partial pressure gradients for inhalation induction of anesthesia.

2. Summarize the concentration effect and the second gas effect. Describe how you might capitalize on these phenomena to rapidly induce a screaming 2-year-old.

3. Pediatric patients can be rapidly anesthetized with inhalational agents. We rarely perform inhalation inductions on adults, particularly older people. How come?

4. You are inducing a 21 month old patient of Dr. Foker's who has a history of pulmonary outflow obstruction and a VSD. The child presents for repair of an inguinal hernia. Will her right-to-left shunt influence inhalation anesthetic uptake and speed of onset of induction? How? If the child had a left-to-right shunt, what would be the effect on uptake an rate of induction?

5. A patient presents for general anesthesia for I & D of an abdominal abscess. She recently underwent a pancreas transplant with the subsequent peek, poke, and pull of the graft. She has been intubated and on mechanical ventilation since before the "pull." When you arrive in SICU to transport the patient, the on-call resident mentions that the patient apparently has severe atelectasis and significant intrapulmonary shunting. Your somewhat underdeveloped anesthetic plan is to take the patient to the OR, place monitors, connect the ventilator, and turn on the gas. How will the parent+s shunt influence induction if you use N20 alone? Halothane alone?

6. Assume the patient in #5 has had a PE rather than a shunt due to atelectasis. How will this influence induction with N20 alone? Halothane alone?

7. What is MAC? List the MAC numbers for the following:

• ¥ Isoflurane
• ¥ Enflurane
• ¥ Halothane
• ¥ Sevoflurane
• ¥ Nitrous oxide
• ¥ Methoxyflurane
• ¥ Desflurane

8. What factors increase MAC? Decrease MAC?

9. A 4 year old Is receiving 50% N20 with 1.5% halothane. How much isoflurane would be required to produce the same anesthetic level? What if the patient was on 50% N20 and 1.5% enflurane? 50% N20 and isoflurane?

10. Each of the following volatile anesthetics is a derivative of methyl ether except:

1. Halothane
2. Enflurane
3. Isoflurane
4. Methoxyflurane
5. Sevoflurane

11. The vessel rich group includes which of the following?

1. Brain
2. Heart
3. Endocrine glands
4. Liver/splanchnic bed
5. Kidney

12. The vessel rich group receives what portion of cardiac output?

1. 15%
2. 30%
3. 60%
4. 75%
5. 80%

13. How would a right mainstem intubation affect the rate of increase in arterial partial pressure of volatile anesthetics?

1. Reduced to the same degree for all volatile agents
2. Accelerated to the same degree for all volatile agents
3. No change if PaO2 > 60 mm Hg
4. Reduced for the most insoluble agents
5. Reduced for the most soluble agents

14. Increased VA will accelerate the rate of increase of FA/FI the most for:

1. Desflurane
2. Methoxyflurane
3. Halothane
4. Enflurane
5. Isoflurane

15. The rate of induction of anesthesia with volatile agents would be slower than expected in a patient:

1. With anemia
2. With chronic renal failure
3. With cirrhotic liver disease
4. In shock
5. With right-to-left intracardiac shunting

16. A right-to-left shunt would have the greatest impact on the rate of inhalation induction with:

1. Halothane
2. Enflurane
3. Isoflurane
4. Desflurane
5. Nitrous Oxide

17. True statements concerning the effect of VA and /or cardiac output on the rate of increase in FA/FI:

1. The effect of an increase in VA on the rate of increase in FA/FI is greater for halothane than for N20
2. The effect of an increase in cardiac output on the rate of increase in FA/FI is greater for halothane than for N20
3. A proportional increase in VA and decrease in cardiac output will accelerate the rate of increase in FA/FI
4. A decrease in cardiac output will FA/FI rate of increase

18. In an effort to accelerate emergence at the end of a 2 hour case, you turn off the isoflurane and increase your N20 level from 30 to 70%. The surgeons finish abruptly. You tum off the gas, and in an effort to save precious pennies, leave the 02 flow rate at 1.5 liters/min. The 70 kg patient is breathing spontaneously at a rate of 16 bpm. 02 sats prior to turning off the N20 were 100%. The patient rapidly desaturates to 89%. What happened? What could be done to avoid this problem in the future?

CNS Effects

1. The correct order from greatest to least decrease in CMRO2

1. Halothane>lsoflurane>Enflurane
2. Halothane>Enflurane>lsoflurane
3. Isoflurane>Halothane>Enflurane
4. Isoflurane>Enflurane>Halothane
5. Enflurane>lsoflurane>Halothane

2. Leaving the OR after a 12 hour case using primarily inhalation agents, you cannot remember where you parked your car. Your plan to call your S.O. to explain why you will be late is confounded by the fact that you can' remember your phone number until you find it on the calling card in your wallet. You also have some trouble dialing the number once you find it. You recount all of these incidents to your S.O. when you reach him/her, saying you believe this is a result of workplace exposure to trace gas. Should he/she buy this excuse or assume you have precocious senility and/or you were really at fluid rounds with the rest of your esteemed colleagues?

3. The correct order from greatest to least increase in CBF and CSF pressure:

1. Halothane>lsoflurane>Enflurane
2. Halothane>Enflurane>lsoflurane
3. Isoflurane>Halothane>Enflurane
4. Isoflurane>Enflurane>Halothane
5. Enflurane>lsoflurane>Halothane

4. True or False: Nitrous oxide increases CBF to a significant degree.

5. What effects do volatile anesthetics have on SSEP's? BAER's?

Pulmonary Effects

1. Most inhalation agents:

1. Increase tidal volume and decrease respiratory rate
2. Increase respiratory rate and decrease tidal volume
3. Decrease minute ventilation in proportion to the decrease in tidal volume
4. Decrease minute ventilation in proportion to the decrease in resp. rate
5. None of the above

2. You are covering the PACU (will it never end?) and are asked to evaluate a patient who has undergone mediastinoscopy after presenting with hoarseness. The PACU nurse informs you that he has a 1.2 pack-century smoking history. He came from the OR extubated and breathing spontaneously at a rate of 8, but shortly after arrival has been breathing at lower and lower respiratory rates. His 02 Sats are 86% on your arrival. His respiratory rate is 4. You give Narcan without response. Review of the anesthetic record reveals that the patient received 2 cc of fentanyl 4 hours ago at the beginning of the case. He was maintained on isoflurane 1.5-1.8% throughout the case. End tidal isoflurane levels were recorded as 0.2% at the time of transport from the OR. What might explain this parent+s lack of respiratory drive?

3. The correct order from greatest to least increase in PCO2 in spontaneously breathing patients at 1 MAC is:

1. Enflurane>lsoflurane>Halothane> N20
2. Isoflurane>Halothane> N20>Enflurane
3. Halothane>lsoflurane> N20>Enflurane
4. N20>Halothane~Enflurane>lsoflurane
5. Enflurane>Halothane>lsoflurane> N20

4. True or false Volatile anesthetics are an excellent choices for use in patients with atopic asthma.

Cardiovascular Effects

1. True or False: Nitrous oxide decreases cardiac output.

2. N20 increases:

1. Arterial blood pressure
2. Heart rate
3. Systemic vascular resistance
4. Cardiac output

3. You are anesthetizing a patient with a history of ASCVD and ischemic cardiomyopathy. You induce the patient with opioids and scopolamine. You plan to maintain the patient on low dose isoflurane (<0.3%) and N20. After an uneventful induction, you turn on the inhalational agents. Shortly thereafter you note a significant decrease in the patient's blood pressure. In an effort to evaluate you shoot a quick cardiac output reading. Would you be surprised is the patient's cardiac output was decreased? Why/Why not? Which of the agents is most likely responsible for your findings?

4. During an inhalational anesthetic with halothane on a 6 year old asthmatic, the patient suddenly desaturates, becomes hard to ventilate and rapidly becomes tachycardic and hypotensive. All of this occurs shortly after administration of a test dose of a cephalosporin. The patient has an identified allergy to penicillin. As part of your response to this problem would you give epinephrine? If so, what dose?

5. Inhalational agents that decrease SVR include:

1. Enflurane
2. Isoflurane
3. Halothane
4. N20

6. Rank the inhalation agents in order of their effect on SVR from greatest to least.

7. Would you use isoflurane on a patient with known 3-vessel coronary artery disease and reversible ischemic changes on dipyridamole-thallium scan? Why/Why not?

8. Has a significant myocardial depressant effect:

1. Enflurane
2. Isoflurane
3. Halothane
4. Nitrous oxide