DAANCE Drug Interactions and Contraindications in Anesthesia — Questions and Answers
Question 1: A patient taking a monoamine oxidase inhibitor (MAOI) for depression is scheduled for oral surgery under sedation. Which anesthetic agent combination poses the greatest risk of a life-threatening interaction?
- Nitrous oxide and midazolam
- Meperidine and an MAOI (Correct answer)
- Lidocaine and epinephrine
- Propofol and fentanyl
Correct answer: Meperidine and an MAOI
Meperidine combined with MAOIs can cause a fatal serotonin syndrome or hyperpyrexic crisis, presenting with hyperthermia, agitation, seizures, and cardiovascular collapse. This interaction is absolute: meperidine is contraindicated in patients taking MAOIs. Other opioids (e.g., fentanyl, morphine) also carry risk with MAOIs but the meperidine-MAOI interaction is the most severe and well-documented.
Question 2: A patient chronically taking beta-blockers presents for sedation. Which effect should the anesthesia team anticipate?
- Exaggerated tachycardia in response to hypotension
- Blunted heart rate response to laryngoscopy, hypoxia, and epinephrine (Correct answer)
- Increased sensitivity to benzodiazepines
- Elevated minimum alveolar concentration (MAC) for inhalation agents
Correct answer: Blunted heart rate response to laryngoscopy, hypoxia, and epinephrine
Beta-blockers competitively block beta-adrenergic receptors, so the compensatory tachycardia that normally accompanies hypotension, airway stimulation, or epinephrine administration is blunted or absent. This can mask signs of hemodynamic compromise and reduce the effectiveness of epinephrine in anaphylaxis.
Question 3: Which combination of drugs synergistically potentiates CNS and respiratory depression and requires significant dose reduction to avoid overdose?
- Benzodiazepines and opioids (Correct answer)
- Local anesthetics and corticosteroids
- Antihistamines and beta-blockers
- Nitrous oxide and lidocaine
Correct answer: Benzodiazepines and opioids
Benzodiazepines and opioids act on different CNS receptors but produce synergistic (greater-than-additive) respiratory and CNS depression when combined. The FDA has issued black-box warnings for this combination. In sedation, significantly reduced doses of each agent are required, and supplemental oxygen and capnography monitoring are essential.
Question 4: A patient's medical history reveals they take warfarin. The primary concern for the anesthesia team during a procedure is:
- Increased risk of malignant hyperthermia
- Prolonged bleeding and difficulty achieving hemostasis (Correct answer)
- Resistance to benzodiazepine sedation
- Enhanced uptake of inhaled anesthetic agents
Correct answer: Prolonged bleeding and difficulty achieving hemostasis
Warfarin is a vitamin K antagonist anticoagulant that prolongs clotting time (measured by INR/PT). Patients on warfarin are at risk for prolonged, difficult-to-control bleeding during and after procedures. The anesthesia team and surgeon must know the patient's current INR and have a bleeding management plan.
Question 5: Epinephrine-containing local anesthetics should be used with extreme caution or avoided in a patient currently taking which medication?
- Acetaminophen
- Non-selective beta-blockers (e.g., propranolol) (Correct answer)
- Proton pump inhibitors
- Selective serotonin reuptake inhibitors (SSRIs)
Correct answer: Non-selective beta-blockers (e.g., propranolol)
Non-selective beta-blockers block beta-2 vasodilatory receptors while leaving alpha-1 vasoconstrictor receptors unopposed. When epinephrine is given, the alpha-1 effect predominates unchecked, potentially causing severe hypertension and reflex bradycardia (the 'epinephrine reversal' phenomenon). SSRIs and PPIs have no clinically significant interaction with epinephrine.
Question 6: Which of the following best describes 'tachyphylaxis' in the context of drug interactions during anesthesia?
- A rapid, severe allergic reaction to an anesthetic agent
- Diminishing response to a drug with repeated dosing over a short time period (Correct answer)
- An abnormally fast heart rate caused by an anesthetic overdose
- Cross-reactivity between two chemically similar local anesthetics
Correct answer: Diminishing response to a drug with repeated dosing over a short time period
Tachyphylaxis is the rapid development of tolerance to a drug's effects with repeated administration over a short period, resulting in a diminishing clinical response. It is clinically relevant in anesthesia with agents like vasopressors (e.g., ephedrine) and some antiemetics, requiring dose adjustment or substitution during a procedure.
DAANCE Drug Interactions and Contraindications in Anesthesia
A patient taking a monoamine oxidase inhibitor (MAOI) for depression is scheduled for oral surgery under sedation.
Which anesthetic agent combination poses the greatest risk of a life-threatening interaction?