Anesthetic Pharmacology Flashcards

A patient under IV sedation with midazolam and fentanyl becomes excessively sedated with significant respiratory depression. After administering naloxone, the patient's respiration improves, but they remain overly sedated. What is the next most appropriate pharmacological intervention?

Answer: Administer flumazenil.

The sedation was induced by two different classes of drugs: an opioid (fentanyl) and a benzodiazepine (midazolam). Naloxone is a specific opioid antagonist and will only reverse the effects of fentanyl. If the patient remains sedated after naloxone administration, it is due to the effects of the benzodiazepine. Flumazenil is a specific benzodiazepine antagonist used to reverse the sedative effects of drugs like midazolam.

What is the primary site of metabolism for amide-type local anesthetics, such as lidocaine and mepivacaine?

Answer: Liver

Amide-type local anesthetics are primarily metabolized by microsomal enzymes in the liver. This is a key pharmacological difference from ester-type local anesthetics, which are metabolized by pseudocholinesterases in the plasma. Liver function is therefore a critical consideration when administering amide anesthetics.

Which of the following sedative agents is known for providing "dissociative anesthesia" and can sometimes cause emergence reactions or hallucinations during recovery?

Answer: Ketamine

Ketamine is an NMDA receptor antagonist that produces a state of dissociative anesthesia, characterized by analgesia, amnesia, and a cataleptic state where the patient may appear awake but is detached from the environment. A well-known side effect is the potential for emergence phenomena, which can include vivid dreams, hallucinations, or delirium during recovery.

During the administration of local anesthetic with epinephrine, a patient suddenly becomes anxious, tremulous, and complains of heart palpitations. Their heart rate increases from 70 to 120 bpm. These signs are most consistent with:

Answer: A systemic reaction to epinephrine.

The rapid onset of tachycardia (rapid heart rate), palpitations, anxiety, and tremors are classic signs of a systemic reaction to the vasoconstrictor, epinephrine, often caused by an inadvertent intravascular injection. Anesthetic toxicity would more likely present with CNS symptoms like dizziness or perioral numbness, while a true allergic reaction would typically involve hives, rash, or respiratory distress.

A significant contraindication for the use of nitrous oxide sedation is a patient with:

Answer: Severe vitamin B12 deficiency.

Nitrous oxide inactivates the cobalt in vitamin B12, rendering it unable to function as a coenzyme. In patients with a severe pre-existing vitamin B12 deficiency, even a single exposure to nitrous oxide can precipitate serious neurological complications, such as subacute combined degeneration of the spinal cord. Therefore, it is a significant contraindication.

Which of the following anesthetic agents is formulated as a lipid emulsion and is known for its rapid onset, short duration of action, and potential to cause pain upon injection?

Answer: Propofol

Propofol is an intravenous anesthetic agent that is insoluble in water and is supplied as a milky-white lipid (oil-in-water) emulsion. It is characterized by a very fast onset and a short duration of action, making it ideal for sedation and induction of anesthesia. A common side effect is pain or burning at the injection site, which is thought to be related to the aqueous concentration of free propofol.