CHS Pharmacology & Medication Management 3 — Questions and Answers
Question 1: Doxorubicin (Adriamycin) is considered a relative contraindication for HBO therapy because it:
- Prevents angiogenesis needed for wound healing
- Potentiates cardiotoxicity under high oxygen partial pressures (Correct answer)
- Blocks hemoglobin oxygen binding
- Increases nitrogen solubility in tissues
Correct answer: Potentiates cardiotoxicity under high oxygen partial pressures
Doxorubicin has known cardiotoxic effects, and high oxygen partial pressures may potentiate cardiac oxidative damage in patients receiving this agent.
Question 2: When managing a patient on warfarin undergoing HBO therapy for chronic wound care, the clinician should be aware that HBO may:
- Completely inhibit warfarin's anticoagulant effect
- Potentiate anticoagulant effects by increasing platelet sensitivity (Correct answer)
- Have no effect on INR or bleeding risk
- Reverse warfarin toxicity through oxidative mechanisms
Correct answer: Potentiate anticoagulant effects by increasing platelet sensitivity
HBO therapy has been shown to potentiate the anticoagulant effects of warfarin, requiring closer INR monitoring in patients on long-term HBO courses.
Question 3: Which medication used for carbon monoxide poisoning acts synergistically with HBO by increasing CO elimination from cytochrome oxidase?
- N-acetylcysteine
- Hydroxocobalamin (Correct answer)
- Sodium bicarbonate
- Mannitol
Correct answer: Hydroxocobalamin
Hydroxocobalamin binds cyanide and works alongside HBO in combined CO/cyanide poisoning (as in smoke inhalation), while HBO displaces CO from hemoglobin and cytochrome oxidase.
Question 4: Nitroglycerin patches worn by a patient during HBO should be managed how?
- Left in place; pressure does not affect transdermal delivery
- Removed before treatment to prevent unpredictable absorption and fire risk (Correct answer)
- Covered with non-flammable dressing and left on
- Dose reduced by 50% before chamber entry
Correct answer: Removed before treatment to prevent unpredictable absorption and fire risk
Nitroglycerin patches should be removed before HBO sessions because pressure alters transdermal absorption rates and the adhesive base may pose a fire hazard.
Question 5: A hyperbaric patient on theophylline (bronchodilator) requires careful monitoring because HBO may:
- Accelerate theophylline clearance, requiring higher doses
- Lower the seizure threshold in combination with theophylline's CNS effects (Correct answer)
- Convert theophylline to a toxic metabolite under pressure
- Cause severe bronchospasm when combined with oxygen
Correct answer: Lower the seizure threshold in combination with theophylline's CNS effects
Theophylline lowers the seizure threshold via adenosine antagonism, and this effect is additive with CNS oxygen toxicity risk in HBO therapy.
Question 6: Bleomycin chemotherapy is considered a strong contraindication for HBO because it causes:
- Severe hypertension during compression phases
- Cumulative pulmonary fibrosis worsened by high-pressure oxygen (Correct answer)
- Rapid hemolysis in elevated oxygen environments
- Systemic vasoconstriction incompatible with wound healing goals
Correct answer: Cumulative pulmonary fibrosis worsened by high-pressure oxygen
Bleomycin causes pulmonary fibrosis that is dramatically worsened by high inspired oxygen fractions, making HBO potentially fatal in patients with bleomycin exposure.
Question 7: When a patient requires IV medication during a multiplace HBO treatment, the drug delivery system must be evaluated for:
- Compatibility with normal saline diluent only
- Pressure effects on flow rates and air bubbles in IV lines (Correct answer)
- Reduced efficacy due to altered protein binding at depth
- The medication's interaction with the stainless steel chamber walls
Correct answer: Pressure effects on flow rates and air bubbles in IV lines
Pressure increases gas solubility, but bubbles trapped in IV tubing can compress and later expand, causing flow rate inaccuracies and potential air embolism risk on decompression.
CHS Pharmacology & Medication Management 3
Doxorubicin (Adriamycin) is considered a relative contraindication for HBO therapy because it: