Non-Barbiturate IV Anesthetics

Anesthesia, Chapter 11

Benzodiazepines

1. Describe the primary means of termination of action of benzodiazepines (bzds).

2. You are in ambulatory surgery and the first patient of the day is a male in his mid-50's who appears much older than his stated age. You notice a vague odor of an unusual mouthwash on his breath. He insists he has been NPO since midnight. You notice spider nevi over his chest and abdomen as you place the EKG patches. He acknowledges consuming "one or two drinks per day". He complains about feeling very anxious about the upcoming procedure (removal of an internal fixator from his radius, which he fractured a year ago while climbing the steps to his house late at night). You premedicate him with midazolam 2 mg IV and he reports feeling better after 60 seconds. Within ten minutes he is complaining about anxiety again. Is it possible that the midazolam was cleared more rapidly than normal in this patient? Would you expect an equipotent dose of lorazepam to have a longer effect? After a third 2 mg dose of midazolam, the patient is more comfortable and voluble. He begins to regale you with stories of a recent GI bleed he'd neglected to mention earlier. He notes that since he began taking tagamet, he has had much less GI distress. What effect would you expect cimetidine to have on midazolam clearance? Would you expect similar effects on diazepam clearance? How about lorazepam?

3. Assume the patient in #2 presents with a history of cirrhosis. How would that history alter your selection and dosing of bzds?

4. Your first patient of the morning is an anxious 90 year-old whom you would like to premedicate with bzds. Which agent would you use? Why? Would you alter the dose if the patient was otherwise healthy and on no medications?

5. You give a very small initial dose of midazolam to the patient in #4. How long would you wait before titrating in additional midazolam?

6. How long is the amnestic period following an induction dose of midazolam?

7. Your thirst for knowledge about anesthesia techniques leads you to persuade your staff to let you do a midazolam induction with a continuous maintenance infusion for a long but minimally stimulating procedure. The patient is an otherwise healthy 32 year-old 210 kg female. How would you adjust your induction dose? Your infusion dose?

8. The patient in #7 remains intubated and barely arousable after 2 hours in the PACU. You titrate in flumazenil 3 mg IV and she becomes alert and is easily extubated. Fifteen minutes later she is doing so well she is transferred to the floor. Forty-five minutes after the patient's transfer you get a stat call to reintubate her. What happened? Do you plan to reintubate her? What other treatment might be an option?

9. What is the currently accepted theory of bzds' mechanism of action?

10. Briefly, describe the respiratory, cardiovascular and CNS effects of bzds.

Ketamine

1. You are asked to anesthetize a 2 year-old for repair of hip dysplasia. The procedure will last several hours and he will be admitted for several days post-op as he becomes accustomed to the spica cast he will be wearing for the next 8 weeks. He is a same day admit. You arrive to pre-op your patient and find the PAR in shambles and several of the staff attempting to coax a 25 kg dwarf-ex-NFL linebacker with a very negative attitude down from the IV hanger. You elect to forego rectal sedation and proceed to draw up a dose of ketamine for trans-pajama administration. What dose would you use? How long will it take before the "darted" child should slide from the IV pole and rest compliantly in your arms? How much time will you have to start an IV, place monitors, paralyze and intubate the child before Damian reappears? By what action will the action of ketamine be terminated?

2. A compliant 5 year-old with a history of asthma with a recent exacerbation (2 weeks ago) presents for appendectomy. He allows you to start an IV. Would you consider using ketamine for induction? What benefits would it have from a respiratory point of view? Are there side effects of ketamine which could complicate your induction? What IV dose would you use to induce this patient?

3. A patient in his 20's suffers a ruptured spleen in an automobile accident. He appears in the OR responsive but confused. BP is 70/40, HR 120. He was pinned in his car for over 2 hours before extraction. EMT personnel report that his BP and HR have been gradually decreasing over the past 15 minutes. Would ketamine be a reasonable anesthetic to use for this patient's splenectomy?

4. The above patient also has a known closed head injury. Would you use ketamine for induction? What are the CNS effects of ketamine?

5. List at least 5 contraindications to the use of ketamine.

6. The patient from #3 does well through your skillful management, the ready availability of 20 units of blood products and the speed of the level 1. 40 minutes post-op in the PACU he appears very agitated and is complaining about horrible nightmares. What is the explanation for this behavior? What treatment would you institute?

Etomidate

1. You induce a patient with 0.3 mg/kg of the (-) isomer of etomidate. What happens? Why?

2. How is the effect of etomidate terminated? How is the drug eliminated?

3. How would you adjust your induction dose of etomidate for a patient with cirrhosis?

4. Briefly describe the respiratory, cardiovascular and CNS effects of etomidate.

5. You are called to the PACU to see a patient who is hypotensive and tachycardic. He is a 62 year-old insulin-dependent diabetic with triopathy. He is s/p cadaveric renal transplant 2 years ago and has good renal function currently. He underwent total knee arthroscopy today and was induced with a single dose of etomidate. Could the etomidate be a factor in the patient's current hemodynamic changes?

6. Could etomidate be used for induction of a patient with porphyria?

Propofol

1. What is the formulation of propofol?

2. How is it metabolized?

3. Discuss the pharmacokinetics of propofol.

4. Briefly describe the respiratory, cardiovascular and CNS effects of propofol.

5. One of the claimed benefits of propofol is a decrease in post-op nausea and vomiting. If you use propofol for cases lasting more than one hour, would you expect a lower incidence of post-op nausea/vomiting than that following pentothal/isoflurane?

Droperidol

1. What is the mechanism of action of droperidol?

2. Briefly describe the respiratory, cardiovascular and CNS effects of droperidol.

3. A patient who had droperidol and fentanyl for awake sedation/analgesia for placement of a DL Leonard presents for revision of the non-functioning catheter. He tells you that, whatever the drugs were last time, he doesn't want "that stuff" again. On further inquiry he reports that the entire experience made him feel "horrible". Could the droperidol have been a factor? You learn further that he suffers from parkinsonism. Would droperidol be a reasonable choice for the current procedure? What if the patient wasn't parkinsonian, but was on haldol?