Platelet count is not the primary diagnostic test used to monitor the therapy’s effect of warfarin. Platelets are involved in the clotting process, but warfarin specifically works by inhibiting the synthesis of vitamin K-dependent clotting factors, which does not directly involve platelets.

Choice B rationale

The white blood cell count (WBC) is not used to monitor the effect of warfarin therapy. WBC is typically used to monitor for infection or inflammation, not the coagulation status of a patient.

Choice C rationale

Prothrombin time (PT) is the correct answer. Warfarin therapy is monitored using the PT, which is reported as the International Normalized Ratio (INR). Warfarin inhibits the synthesis of vitamin K-dependent clotting factors, which include Factors II, VII, IX, and X, and Proteins C and S. The PT/INR is sensitive to changes in these factors. An elevated INR indicates a higher risk of bleeding, while a lower INR suggests a higher risk of clotting.

Choice D rationale

Activated partial thromboplastin time (aPTT) is not typically used to monitor warfarin therapy. The aPTT test evaluates the intrinsic and common pathways of coagulation, which includes factors XII, XI, IX, VIII, X, V, II (prothrombin), and I (fibrinogen). Warfarin affects the extrinsic pathway and common pathway, not the intrinsic pathway. Therefore, aPTT is not the best test to monitor the effects of warfarin.

Choice A rationale

While electrolyte balance is important in patient care, it is not the primary reason for measuring gastric residual before administering a feeding through an NG tube.

Choice B rationale

Confirming the placement of the NG tube is crucial before administering a feeding. However, measuring the gastric residual is not the primary method used to confirm tube placement.

Choice C rationale

Removing gastric acid that might cause dyspepsia is not the main purpose of measuring gastric residual. Dyspepsia, or indigestion, is typically managed with medications and dietary modifications.

Choice D rationale

The primary purpose of measuring gastric residual is to identify delayed gastric emptying. Gastric residual refers to the volume of formula or contents remaining in the stomach from the previous feeding. If gastric emptying is delayed, the nurse should avoid overfeeding the patient and causing gastric distention.