Intravenous Opioid Anesthetics

Miller Anesthesia, Chapter 12

1. You are called on to provide anesthesia for reduction of an open tibial-fibular fracture and ORIF of a proximal humeral fracture in a patient who was involved in a pedestrian vs. automobile accident this evening. The patient is in his mid-30's with a long history of IV drug abuse. Discuss your plans for managing his anesthetic. Will you premedicate him with narcotics? Will you take any special precautions in managing his airway? Will you use general or regional anesthesia

2. You are called to the ER to intubate an obtunded patient who was "found down" and unresponsive in a local park. When you arrive you notice he is somnolent and is breathing at a rate of 6 bpm with significant apneic pauses from time to time. He is easy to mask ventilate. Since he is stable with the respiratory therapy tech ventilating him, you elect to start an IV prior to intubating him. During multiple IV attempts you notice widespread "needle tracks" over most of the patient's major peripheral veins. After finally placing a 20 gauge IV in a scalp vein, you elect to titrate in a dose of naloxone. What endpoint will you use to direct your dosing of naloxone?

3. The patient in #2 responds nicely to Narcan and avoids the necessity of intubation in the ER. He is ultimately transferred to a step-down unit bed, where you next see him after being paged stat once again to manage his airway and ventilation. He was breathing 12 bpm and was easily arousable after Narcan in the ER. On your arrival he is again breathing 5-6 bpm with a periodic pattern, and he is barely arousable to sternal rub. What is the likely explanation for his respiratory depression? What treatment will you institute?

Renal and Gl Effects

1. You are called to the PACU to address a lack of urine output in a patient who had a minimally invasive procedure and who received morphine for intraop and postop analgesia. The patient is not catheterized. Could the morphine be a cause of the patient's lack of urine output? If so, how?

2. You are planning a rapid sequence induction of one of Dr. Buchwald's obese patients. Will you give opioids prior to induction? Why/Why not?

3. True or False: All opioids increase tone in the sphincter of Oddi and increase biliary duct pressure.

4. True or False: Opioid induced biliary spasm frequently causes severe epigastric pain that may be confused with symptoms of cardiac ischemia.

5. Describe two pharmacologic approaches to reverse opioid-induced biliary spasm.

6. Narcotic analgesics may increase the incidence of perioperative nausea and vomiting by:

• increasing Gl secretions
• stimulating the chemoreceptor trigger zone in the area postrema
• prolonging Gl emptying times
• decreasing Gl motility
• all of the above
  
  

Miscellaneous Effects

1. You are walking through the PACU, minding your own business when you are suddenly confronted by a nurse with a patient who is shivering violently. He has an axillary temp of 98 and has just arrived following a prolonged balanced anesthetic, which included significant levels of isoflurane. He is otherwise healthy except for a history of depression for which he takes "some kind of anti-depressant medication." You're asked to write an order for Demerol to treat his shivering. You do so, and before you can leave the PACU, the patient becomes agitated, hypertensive, rigid, and seizes. What anti-depressant was the patient likely taking?

2. Would you use opioid narcotics as part of your anesthetic technique when caring for a 20 year old woman who has an appendicitis and happens to be 17 weeks pregnant?

Drug Interactions

1. You use a balanced anesthetic technique to anesthetize a 31 year old schizophrenic admitted for a 2 hour inguinal herniorrhaphy. He weighs 70 kg. During the procedure he receives 700 mcg of fentanyl. In the PACU he remains quite somnolent and is still breathing at only 8 bpm 90 minutes after arrival. He is chronically on thioridazine (Mellaril). Could the size of the narcotic dose alone explain the patient's slow wake-up and prolonged respiratory depression? What role might his psych medication play in this?

Agonist-Antagonist and Antagonist Opioids

1. At the end of a carotid endarterectomy on a 72 year old with a history of angina with minimal exertion, the neurosurgeons are insistent that the 450 mcg of fentanyl you gave 3 hours ago during induction are the cause of the patient's failure to awaken immediately in the PACU. They insist you give "something to reverse the narcotics." Assume for a moment that these neurosurgeons are from a different planet and are actually willing to listen to your input about this course action. What would you advise about "reversing" the narcotics. If persuaded by their concerns, how would you proceed? What agent would you employ? How much? How fast?

Pharmacokinetics

1. Has a relatively low lipid solubility:

• Fentanyl
• Morphine
• Sufentanil
• Alfentanil
• Meperidine

2. Renal metabolism may account for as much as 38% of its clearance:

• Fentanyl
• Morphine
• Sufentanil
• Alfentanil
• Meperidine

3. You are called to emergently manage the airway of a patient on the General Surgery service who has apparently seized. You provide ventilatory support briefly until the patient is sufficiently recovered to sustain his own airway. During this time you learn from the surgery intern cross-covering on this patient that the patient has a history of renal failure and 4 days ago underwent a bilateral nephrectomy. His considerable post-op pain has been managed with rather high levels of PCA meperidine (he gets hives from morphine). He was last dialyzed 2 days ago and is due for dialysis in the morning. To your utter astonishment, the intern seeks your opinion about managing this patient. What may have caused the apparent seizure? Could any of his medications have been a factor in precipitating this spell? Can you recommend an approach for controlling this patient's pain that may be more appropriate and effective?

4. Safe to use with MAO inhibitors:

• Fentanyl
• Morphine
• Sufentanil
• Alfentanil
• Meperidine

5. Rank the following in order from most highly lipid soluble to least:

• Fentanyl
• Morphine
• Sufentanil
• Alfentanil
• Meperidine

6. Rank the following in order from most highly protein bound to least:

• Fentanyl
• Morphine
• Sufentanil
• Alfentanil
• Meperidine

7. Explain why alfentanil has a relatively short elimination time? Why does it have a relatively rapid onset of action?