A nurse is caring for a client who is postoperative following orthopedic surgery and is receiving IV ketorolac.
Which of the following findings should the nurse identify as the priority to report to the provider?

Choice A rationale

An INR (International Normalized Ratio) of 4.0 indicates that the client's blood is much thinner than the therapeutic range for most conditions (usually 2.0-3.0 for warfarin). This significantly increases the risk of bleeding. Vitamin K is the antidote for warfarin because it is essential for the synthesis of clotting factors (II, VII, IX, X) in the liver. Administering vitamin K reverses the anticoagulant effect of warfarin, reducing the risk of hemorrhage by promoting the production of functional clotting proteins.

Choice B rationale

Protamine sulfate is the antidote for heparin. It works by forming a stable ion pair with heparin, neutralizing its anticoagulant effects. It has no effect on the anticoagulant properties of warfarin, which acts by inhibiting vitamin K epoxide reductase, an enzyme crucial for the regeneration of active vitamin K necessary for clotting factor synthesis. Therefore, protamine is not indicated for warfarin overdose.

Choice C rationale

Calcium gluconate is used to treat hypocalcemia and magnesium toxicity. Calcium plays a vital role in numerous physiological processes, including bone health and muscle function, and is essential for blood coagulation. However, it does not directly counteract the effects of warfarin, which targets vitamin K-dependent clotting factors, and is not the appropriate antidote for an elevated INR.

Choice D rationale

Epinephrine is a potent vasoconstrictor and bronchodilator used in anaphylaxis, cardiac arrest, and severe asthma. It acts on alpha and beta-adrenergic receptors, leading to increased heart rate, blood pressure, and bronchodilation. It has no role in reversing the anticoagulant effects of warfarin and is not indicated for managing an elevated INR.

Choice A rationale

Restlessness, also known as akathisia, is not a typical expected adverse effect of ondansetron. Ondansetron primarily acts as a selective 5-HT3 receptor antagonist, blocking serotonin's emetogenic effects in the chemoreceptor trigger zone and gastrointestinal tract. Common adverse effects are generally mild, including headache, constipation, or diarrhea, with neurological effects like restlessness being rare and atypical for this drug's primary mechanism.

Choice B rationale

Ondansetron should be administered prophylactically, typically 30 minutes *before* chemotherapy, to achieve optimal antiemetic effect. Its mechanism involves blocking serotonin receptors that, when activated by chemotherapy, trigger nausea and vomiting. Pre-emptive administration ensures therapeutic drug levels are present to counteract the emetogenic stimuli effectively before their onset.

Choice C rationale

Acute nausea and vomiting associated with chemotherapy can persist for significantly longer than 12 hours, often lasting for 24 to 48 hours or even longer depending on the specific chemotherapeutic agent and its emetogenic potential. The duration of emesis is highly variable and directly related to the drug's pharmacokinetic profile and the extent of serotonin release.

Choice D rationale

If nausea persists despite ondansetron administration, it indicates an inadequate antiemetic response, likely due to the complex neurochemical pathways involved in chemotherapy-induced nausea and vomiting. This often necessitates a multi-modal approach, involving the addition of other antiemetic agents like corticosteroids (e.g., dexamethasone) or neurokinin-1 receptor antagonists (e.g., aprepitant) to target different emetogenic pathways for more complete symptom control.